Spring 2018: BiPed Ultrasonic Sensor Board Power Test

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jorge Hernandez (Electronics & Control Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

From the research performed, the number of ultrasonic sensors required to make a bi-ped robot for our project is one. We know one sensor will be used which will cause the robot to only detect objects in a one-directional plane which will act as the eyes of the robot. We are using the ultrasonic HC-SR04 sensor to meet our level two requirements:

Shall be able to see other robots to avoid a collision. The robot will stop completely and wait for a command. (Ultrasonic sensor). This expands further:

1. If the sensors are too far from an object, the robot will move forward.

2. If the sensors are too close to an object, the robot should move backward.

3. If the sensors are within the range of an object, the robot will not move.

Choosing our Ultrasonic

For economical reason, we chose to go with the SEN136B5B ultrasonic sensor as the previous Biped Robot from spring 17’ had left thiers with Professor Hill (along with other parts); L1-8: Micro FOBO shall not exceed a cost of $200 to construct. Although there are more precise sensors all we needed was a sensor to provide a measurement of how far an object is away (3cm-400cm) which the Sen136B5B does well. Another reason why we chose this ultrasonic is to satisfy requirement L1-4: Micro FOBO will be a toy robot based on the design of the FOBO, which make it seem as the eyes of Micro Fobo.

Power Estimates

Due to the fact, the 3DoT board we are using has a 3.3V input is another huge reason we are using the SEN136B5B as it functions at 3.3V, unlike the HC-SR04. We could have used the HC-SR04 but to save space we eliminate the idea of a booster shield which will allow us to use this sensor and other 5V sensors if needed. The global current consumption was very hard to test as it only draws 15 mA according to http://wiki.seeedstudio.com/Ultra_Sonic_range_measurement_module/ which is very low and did not give me a reading when I attached it to a current sensor which would’ve given me the power estimates of this ultrasonic.

Fig.1 Ultrasonic 6in Test

Fig.2 Ultrasonic Connections

This sketch reads a PING))) ultrasonic rangefinder and returns the distance to the closest object in range. To do this, it sends a pulse to the sensor to initiate a reading, then listens for a pulse to return. The length of the returning pulse is proportional to the distance of the object from the sensor.

The circuit:

+V connection of the PING))) attached to +5V
GND connection of the PING))) attached to ground
SIG connection of the PING))) attached to digital pin 7

Wiring & Code

*/

// this constant won't change. It's the pin number of the sensor's output:

const int pingPin = 7;

voidsetup() {

  // initialize serial communication:

  Serial.begin(9600);

}

voidloop() {

  // establish variables for duration of the ping, and the distance result

  // in inches and centimeters:

  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.

  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:

  pinMode(pingPin, OUTPUT);

  digitalWrite(pingPin, LOW);

  delayMicroseconds(2);

  digitalWrite(pingPin, HIGH);

  delayMicroseconds(5);

  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH pulse

  // whose duration is the time (in microseconds) from the sending of the ping

  // to the reception of its echo off of an object.

  pinMode(pingPin, INPUT);

  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance

Fig.3 Ultrasonic Test#2

Power Estimates Continued

We choose to go with the Seed Ultrasonic Sensor (SEN136B5B ) as it is 3.3V compatible, the sensor was available from previous biped projects, and to meet requirements for our project which were explained above. This 3 pin ultrasonic requires power, Gnd, and a digital pin has an operating current of 15 mA and can read up to 400cm as tested.

Fig.2 Part 1 Power Estimates Table

Fig.2 Part 2 Power Estimates Table

Conclusion

We choose to go with the Seed Ultrasonic Sensor (SEN136B5B ) as it is 3.3V compatible, the sensor was available from previous biped projects, and to meet requirements for our project which were explained above. This 3 pin ultrasonic requires power, Gnd, and a digital pin has an operating current of 15 mA and can read up to 400cm as tested.

References

Spring 2018: BiPed Preliminary Design Documentation

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager), Jeffery De La Cruz (MST), Jorge Hernandez (E&C)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Mission Objective

By: Miguel Gonzalez (Project Manager & Manufacture)

Our goal for this project is to design and manufacture a BiPed Robot. This robot will be slightly similar to the BiPed robot that was created in Spring 2016 and another bipedal robot named FOBO, created by Jonathan Dowdall. Our design will be based on FOBO but will be much smaller in size that implements micro servos for walking and turning. For sensing its surroundings, the robot will utilize ultrasonic and Infrared sensors. Other key differences between the FOBO and our micro version of FOBO are that:

The head of our robot shall house a 3DoT board, servos controller shield, and a sensor shield.
The movement of our robot will be conducted via SG90 micro servos that will replace the clunky and oversized Hitec HS-805BB servos.
The legs of our robot will have a more efficient method to mount and utilize its servos for weight reduction and for longer walking steps.
Our robot will utilize Bluetooth technology for user to robot communication and movement control
The robot’s power system will be changed from heavy LIPO batteries to a single Samsung 18650 battery located near the robot’s center of mass.

The mission of Project BiPed is to design the BiPed to navigate a predesigned maze. The BiPed shall be able to navigate the maze with user input from the Arxterra App/Control Panel. The BiPed will be able to memorize the user-defined path and will be able to navigate it autonomously. In addition, the BiPed will acknowledge other robots while traversing the maze and avoid collisions using its sensors. To learn more about the mission objective you can take a look here. For preliminary maze designs and definitions take a look here.

Project: Level 1 Requirements

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Will:

L1-1: Micro FOBO will stand on its own without any physical help.

L1-2: Micro FOBO’s electronic components will be easily assembled and disassembled.

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-6: Micro FOBO will fit within the classroom cabinets shelves. 28”x13”x14.5”

L1-7: Micro FOBO will utilize a 3DoT board or Sparkfun Pro Micro 3.3V/8MHz.

L1-8: Micro FOBO’s part components will be 3D printed using the material carbon fiber PLA.

L1-9: Micro FOBO will not exceed a print time of 7.80 hours. Upon approval of the waiver.

Shall:

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

L1-12: Micro FOBO shall detect intersections in the maze.

L1-13: Micro FOBO shall be able to perform static walking.

L1-14: Micro FOBO shall produce 90 degrees turn.

L1-15: Micro FOBO shall be guided through the maze with the use of the Arxterra application.

L1-16: Micro FOBO shall record the path of the maze.

L1-17: The Micro FOBO shall traverse the maze using the recorded path.

L1-18: Micro FOBO shall be able to traverse cloth, paper, and linoleum materials.

L1-19: The Final Biped shall be completed by May 10th, 2018.

Should:

L1-20: Micro FOBO should step over a square rod 1cm tall, 1 cm wide by 10 cm long

L1-21: Micro FOBO should be able to perform dynamic walking

System/Subsystem: Level 2 Requirements

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Will:

L2-1: Micro FOBO will be connected via Bluetooth to the app on an android phone.

L2-2: Micro FOBO dimensions of the robot will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-3: Micro FOBO will use SG90 micro servos.

Shall:

L2-4: Micro FOBO shall use UV/IR sensors to detect intersections.

L2-5: Micro FOBO shall use the color of the maze to establish if it needs to turn. black (0,0,0) green (0,255,0) for line following.

L2-6: Micro FOBO shall use a battery that outputs 3.7V nominal.

L2-7: The user shall use the Arxterra application to move the robot forward, backward, left, and right.

L2-8: Micro FOBO connectors shall be able to connect and reconnect all the wiring in less than 10 min.

L2-9: Micro FOBO wiring shall be nice and clean with the use of terminal blocks, contact pins, 2.0mm PH series JST connectors, and barrel connectors.

L2-10: Micro FOBO shall play a musical tune when the maze is completed.

L2-11: Micro FOBO shall have indicating LEDs to demonstrate either a left or right turn.

L2-12: The Micro FOBO shall record the path of the robot on the 3DoT board or the Sparkfun Pro Micro 3.3V/8MHz to navigate the robot through the maze.

L2-13: Micro FOBO shall use a 3D printed chassis and leg components.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

L2-15: Micro FOBO shall weigh no more than the allocated mass of 460g.

L2-16: Micro FOBO shall detect objects 8 inches from it.

Should:

L2-17: Micro FOBO should be able to see other robots to avoid a collision. The robot will stop completely and wait for clearance. (Ultrasonic sensor)

L2-18: Micro FOBO should take a bow at the end of the maze as a victory celebration.

System Block Diagram

By: Jorge Hernandez (E&C Engineer)

Verified By: Miguel Gonzalez (Project Manager)

After looking at all the constraints and requirements for the robot our group came up with a system block diagram that could help us visualize how the robot’s components interacted with one another. This diagram made it clear to understand where initial designs should be made and provided great insists to some challenges we would have in the future. For example, we can see the product breakdown structure down below and notice that our robot’s chassis contains more sub-branches than the rest of the diagram sibling branches. This indicates that most of the designing will be involved in the creation of the robot’s main hardware. This would help our manufacturing engineer know that designing of the robot’s chassis should be done as early as possible to prevent set back. Another branch that stands out is the software section. This branch is made up of multiple sections that include Arxterra control, line following, avoidance detection, and turning code. This branch is important as the diagram illustrates that our robot is highly dependent on its software to achieve a successful mission objective.

Fig.1 System Block Diagram

Work Breakdown Structure

By: Miguel Gonzalez (Project Manager & Manufacture)

Once we had a clear idea of how the robot would be made we proceed to create a WBS. A work breakdown structure allows us to list and assign tasks/work that needs to be completed for the success of the robot. The tasked listed on the WBS based on the team member’s job description and are directly imported from the tasks created on the Spring 2018 Task Matrix that can be found here. The diagram below is a much easier method of reading the tasked matrix as it clearly shows each team member’s responsibilities.

Our group consists of three members fulfilling the roles of Project Manager, E&C, MST, and Manufacturing Engineer. Since the group has fewer members than the positions available the manufacturing role of the team was given to the Project Manager.

The diagram below shows the workload of the project and how it is distributed among the team. It is based on the job descriptions and shows major tasks that each person is responsible for. We will be taking a look at each team members role more closely to better understand the structure of the team and its workload.

Fig.2 BiPed Work Breakdown Structure

Miguel Gonzalez (Project Manager)

Fig.3 PM and Manufacturing Engineer Tasks (Blue)

At the top of the WBS in blue, we have the project manager section. Note that in our case the project manager is also the manufacturing engineer and thus the tasks for both roles are given to the same person. The second blue icon shows the tasks specific to the project manager which has the project manager responsible for the following tasks:

Creating and managing schedule
Creating a budget list
Creating the preliminary report
Creating the final blog post
Creating project video
Define Work Breakdown Schedule

The manufacturing tasks given to the project manager are listed to the right side of the WBS also in blue. These tasks are broken down into three sections Mechanical Design, 3D Modeling, and Assembly. These sections were created based on which tasks are needed to be done before moving on to the next section. For example, Mechanical Design is a prerequisite for 3D Modeling and Assemble thus it is located on top of the other tasks.

Jeffery De La Cruz (MST)

Fig.4 MST Tasks (Red)

Moving on to the left side of the WBS (in red), we have all the tasks assigned to the MST engineer. Once again, these tasks are divided up into three sections System Designs, Software, and System Tests. The system designs include tasks that have a focus on research and trade studies that will end up helping with the software development and system test. Once those tasks are done the MST engineer can proceed with implementing the software with the Arxterra control panel and onto an android application. The final tasks for the MST engineer focus on verifying and testing all sections of the robot to see if they are operational.

Jorge Hernandez (E&C)

Fig.5 E&C Tasks (Green)

The final branch in the WBS applies to the E&C engineer and his tasks needed for a successful project. The E&C has the greatest responsibility for the success of the robot becoming operational. His roles are divided into 4 categories Electronics Design, Experiments, Microcontroller, and Control. These categories cover a wide range of tasks that need to be realized to proceed with the overall goal of the Biped project.

Product Breakdown Structure

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Fig.6 Product Breakdown Structure

Based on System Block

Sensor Suite

The color sensor will be able to detect colors and its data input range Ex, black (0,0,0) green (0,255,0) for line following.
Will be able to see intersection sign on the maze and differentiate its color from the path lines.
Shall be able to see other robots to avoid a collision. The robot will stop completely and wait for a command. (Ultrasonic sensor/IR)
The robot should have to indicate LEDs to show where the robot plans to make a turn (left or right)

Smartphone App

Will allow usage of the app to navigate the robot through the maze through forward, back, left, and right commands.
Will record the path of the robot in 3Dot board to navigate robot without the user controlling it.
The robot will be connected via Bluetooth to the app on an android phone.

Chassis

The wiring for the robot shall be nice and clean with the use of terminal blocks, contact pins, 2.0mm PH series JST connectors, and barrel connectors.
All connectors shall be able to connect and reconnect all the wiring in less than 5 min.
Dimensions of the robot will need to be small enough to fit in a 6in by 6in box for maze purposes.

Battery

The robot power management system will use two 1000mAh 2S 20C Lipo Pack rechargeable LIPO batteries.

Interface Matrix

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Fig.7 Interface Matrix

The current interface matrix for the prototype Micro FOBO uses the Arduino UNO. A CD4017BE IC was used to control the eight servos. The output of the CD4017BE IC has then connected the Arduino UNO which will the Robot Poser control the movement of the servos so that the Micro FOBO can walk. The interface matrix will be updated once the 3DoT board or the Sparkfun Pro Micro 3.3V/MHz is acquired. This is currently for the prototype of the Micro FOBO. The excel file containing the interface matrix for the prototype Micro FOBO can be found here.

Prototype Fritzing Diagram for Biped

By: Jorge Hernandez (E&C Engineer)

Verified By: Miguel Gonzalez (Project Manager)

The Fritzing application allows a physical breadboard design to be created digitally. By designing a digital version, the beginning PCB designs can begin. One difficulty with using the free software is that the library does not have all the parts needed for many designs. Using Google, many of the parts required were found with Github.

Here are links to the Fritzing libraries for FOBO:

(If using the Adafruit Servo Driver)

https://github.com/adafruit/Fritzing-Library

(For the Bluetooth Module HC-06 and Accelerometer/Gyroscope MPU-6050)

https://github.com/RafaGS/Fritzing

Fig.8 Electronic Fritzing Diagram

There was nothing to change at all as we are using the FOBO’s same hardware build. We decided

to go with 2 Lithium Ion batteries, 12 servos, and ultrasonic as well. The color sensor is being

discussed since we know Spiderbot wants to use UV sensors but will be added to fritz diagram

once we know the final maze descriptions.

References

Spring 2016 ROFI

Spring 2017 Velociraptor

Updated Fritzing

Mechanical Drawings

By: Miguel Gonzalez (Project Manager & Manufacture)

Related Requirements

Level One Requirements

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

Level Two Requirements

L2-2: Micro FOBO dimensions will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

Micro FOBO Design

For some clarification and for better understanding our design of the Micro FOBO, I have created a color-coded assembly of the robot with matching titles indicating the names of each component. Below I discuss the design of these components that make up the Micro FOBO.

Fig.9 Micro FOBO Colored Parts

As you can see from the image above, the Micro FOBO consist of 9 different parts: Servo Hip, Foot, Servo Band, Servo Bracket, Servo Wrap, Bearing Frame, Body Riser, Electronics Frame, and the Head. Note that Micro FOBO can be made up of multiple copies of the same part component and thus colored coded with the same color. For example, there are four servo bands in Micro FOBO which are shown in light green on the picture. Now that we know which parts make up the robot we can begin looking at the design of each part individually.

Part 0: Servo Hip

Fig.10 Part 0: Servo Hip

The “Servo Hip” component of the Micro FOBO is responsible for attaching the two upper micro servos which are the hip servos. This bracket connects both servos (right and left legs) together to act as a hip bone that allows the robot to move its legs left to right. The connection to the servos is made via servo horns that are provided by the manufacturer. This part has two allocated trenches that match the dimensions of the servo horns allowing the servos to mount to the part. The horns are then screwed onto the servo hip using M2.5 screws that are 8mm in length.

Drawing File

Part 1: Foot

Fig.11 Part 1: Foot

The “Foot” component is the same for both legs and is a simple shoe like design with wide pads on its sides. The extra material on the sides allows a greater amount of surface to touch the floor allowing the robot to balance easier. Currently, this part is in its simplified state as there is not much detail design put on it. This is because the team plans on mounting UV sensors onto the bottom of the foot where the hole is located. This would allow the sensor to be as close to the ground as possible to maintain an accurate reading. Once we receive the sensor additional design changes will be made to this part. Currently, the part allows the ankle servo, which is the servo closest to the ground, to be mounted onto one side of the foot though servo horn cutouts. The horn cutout is located on the inside wall of the part. The hole then allows an M2.5 X8 screw to secure the servo onto the foot piece.

Drawing File

Part 2: Servo Band

Fig. 12 Part 2: Servo Band

There is a total of four “Servo Bands” located on the Micro FOBO. This part is responsible for grouping two micro servos together which forms a section of a leg. The two servos are pressure fitted into the square cutout and thus this part must be dimensionally precise to prevent servos to come loose. This piece had several revisions to satisfy the dimensional accuracy need to keep the servos secure. The servos were measured with a caliper and the thickness of the servos stickers even had to be considered when designing this piece. Due to leg movement constraints, only one servo can have extra material to be screwed onto the part.

Drawing File

Part 3: Servo Bracket

Fig.13 Part 3: Servo Bracket

The ‘Servo Bracket” is a shorter version of part 0: servo hip and serves a similar purpose. This component mounts onto two servos that are located on the servo bands. This allows the second to the top servo to move the lower leg. This piece is located in the middle of the leg and connects the top and lower sections. This piece can be thought as the knee of the robot. Just like the other brackets, there are two cutout trenches that allow servo horns to be mounted and secured through a single screw. This piece can be varied in length to adjust the height of the robot and adjust the walking stride of the robot itself.

Drawing File

Part 4: Servo Wrap

Fig.14 Part 4: Servo Wrap

The “Servo Wrap” is a small piece that attaches the back of the hip servo (top leg servo) to be mounted onto part 5: Bearing Frame. It is connected via an M2 screw that is 18mm in length. The screw goes through the servo, through the servo band, and screws into this piece. A hole on the left side of the wall was added to allow the servo wires to feed through and connect back to the electronics. Notice there is a hexagon trench located near the middle of the part. This trench allows an M3 nut to be placed in that location and lets a screw to secure Part 4 with Part 5. Another key design feature is the chamfer cutout located on the backside of the part. This permits higher degrees of movement from the hip servos by at least 45 degrees more.

Drawing File

Part 5: Bearing Frame

Fig.15 Part 5: Bearing Frame

The “Bearing Frame” is a mirror-like component to part 0 as both pieces work together to provide the connection of legs to body. One of the key differences is that this piece contains two large circular trenches in which a bearing can fit onto. Using a 10mm circular bearing we place it on the part to provide free angular movement to the left and right sides of the pieces. Once the bearings are fitted inside, we can use M3X14 bolts to attach the servo wrap pieces to the left and right side of the Bearing Frame. Since the legs servos are already attached to the servo wrap we effectively attached the two legs to the body of the robot.

Drawing File

Part 6: Body Riser

Fig.16 Part 6: Body Riser

Micro FOBO mainly consists of a head and two legs but this part, body riser, can be considered the body of the robot. This component connects the two attached legs with the head. There are two fork-like structures located at the top of the piece that allows part 0 and part 5 to fit in snugly effectively connecting the two legs to this piece. Part 0 and part 6 are secured through a couple of M3 screws with an approximate length of 16 mm. The back side of this component is flat and has two holes for connecting to part 7 which is the electronics frame. The body riser can be increased in height allowing the robot’s head to be located higher above the legs. We can experiment with changing the height to allow shifting the robot’s center of mass higher or lower as needed.

Drawing File

Part 7: Electronics Frame

Fig.17 Part 7: Electronics Frame

The Electronics Frame is a thin component that is responsible for connecting the PCB to the body riser. The PCB will contain four mounting holes which will allow the board to connect to this part. Note that the part contains extruded cubes that correspond to the location of the PCB hole mounts. These extruded cubes also have a hole cut out to fit M3 screws that secure the board in place. Finally, the part can be secured to the head via similar M3 screws on the side of the part and head

Drawing File

Part 8: Head

Fig.18 Part 8: Head

One of the first challenges in creating a miniature FOBO we observed was that our robot would need to support large amounts of electronic components that used to be on the regular size FOBO. These electronics would need to be smaller in size or our head design would need to optimize to fit all the electronics. Our first design was based on the prediction that the new electronics would have a smaller footprint and thus the head of the Micro FOBO is much smaller. The exact dimensions can be found on the link below. Once the size of the head was set I began to look at some redesigns that I can implement to change the look and functionality of the robot’s head. That is when I stumbled on an image of a tin toy robot from the 1950s.

Fig.19 1950’s Tin Toy

As you can see from the image above this robot has a similar head as the FOBO which gave me the idea of emulating the design of the face. The ultrasonic sensor will take place as the robot’s eyes and the mouth and nose features would simply be aesthetics. Another thing that I noticed was that the tin toy contained antennas on the left and right side of the head. One of the redesigns I wanted to incorporate since the beginning was adding turn signals to the robot and the antennas can certainly be used for that. My idea is to have small 5mm red LED’s as the tip of the antennas that would blink indicating when the robot will turn and in what direction. Finally, we see that there is a small red light on top of the robot that can be designed to indicate on/off status of the robot.

Fig.20 Mechanical Design Improvements

Drawing File Tin Robot Toy

Resource Reports (Power, Mass, Cost)

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Below are the preliminary resource reports for the mass, power, and cost for Project BiPed. As we continue working on Project BiPed, the resource report will be updated to the actual numbers of each mass, power, and cost.

Fig. 21 Mass Report

The total mass of the Micro FOBO is at around 351.5 grams. This mass consists of the following:

Part 0: Hip Bracket x1

Part 1: Foot x2

Part 2: Servo Band x4

Part 3: Servo Bracket x2

Part 4: Servo Wrap x2

Part 5: Bearing Frame x1

Part 6: Body Riser x1

Part 7: Electronics Frame x1

Part 8: Head Compartment x1

Micro Servos x8

Samsung ICR18650 x1

Arduino UNO x1

Servo Shield x1

Ultrasonic HC-SR04 x1

To view the excel file of the mass report, click here.

The mass of the Micro FOBO will change because the material used to print the parts of the Micro FOBO will change from regular PLA to carbon fiber PLA. The Micro FOBO will become just lighter but not by much. The mass of the Arduino UNO and servo shield is included at the moment but will be updated once the 3DoT Board of the Sparkfun Pro Micro 3.3V/8MHz is included. Also, the battery case was not included because the position of the battery is to be determined.

Fig.22 Power Report

Cost Report

By: Miguel Gonzalez (Project Manager & Manufacture)

Related Requirement

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

Project BiPed is one of this semesters robot production division in which a bipedal robot will be designed, engineered, and produced by the end of the semester. One of the most important tasks of any project is to evaluate and determine the cost of production of said products. In this post, we will be looking at the estimated cost of producing the BiPed robot. These costs will solely rely on physical component cost and any design and research development cost will not be mentioned in this post.

As part of the requirements stated by the customer, a budget was set for each project divisions. This is a loosely budget of $250 in which all material bought can be reimbursed in full. Any additional items and/or services that exceeded this budget will be covered by the team members working on the project. To help reduce costs, the customer has allowed access to his lab stock inventory of electronics, hardware, and materials. Borrowed items will be included in the budget table but the costs of the items will not be included in the total money spent.

Fig.23 Spring 2018 BiPed Budget Table

Budget Table (for access to links found on the table)

The above table shows the cost of components we have used and purchased as of April 18, 2018. The budget table above is divided into ten separate columns indicating important information about the used and purchased products. In the left column are the names of the parts and items used by the team to produce the biped robot. To the right of the parts column, is a link section that allows viewers to find the same parts we used for this project online. The table is also set up for invoice collection for any items that were purchased these invoices/receipts are linked on the second column to the right of the table. The budget table tries to incorporate all useful information that may be needed for future part purchases, replacement of parts, and for reimbursements.

Overall, we wanted to make sure not to spend any unnecessary money and to reuse as many electrical components and hardware as we could. It is important to note that some additions to the table will be made as the project continues and more items are needed. Multiple hours of reading past blogs as well as research were done to reduce unnecessary consumption of resources and to allocate as much possible reused parts from previous semester projects. Our total expenditures as of April 18, 2018, is a grand total of $226.54 which is under the customer’s project funding of $250.

Planning & Schedule

By: Miguel Gonzalez (Project Manager & Manufacture)

This schedule is comprehensive and accounts for all tasks that should be completed by the displayed due dates. Using Project Libre, we can list the tasks needed to have a successful project. By using the Gantt chart feature we can see the tasks in a much more comprehensive chart that clearly demonstrates time frames and work periods. All tasks and due dates listed were imported from our class task matrix.

Overall Goal

Of course, like any project, our goal for BiPed robot is to finish every task on time while meeting our initial level one and level two requirements. To succeed, the following Gantt Chart was created with very precise timelines and due dates for procedural tasks that must be met to succeed in completing the BiPed robot on time. When creating the Gantt Chart, we notice three major tasks that are important to the success of the project. These tasks were the general project plan, finalization of the 3D model, and the final blog post. The deadlines for these tasks are March 15^th, April 12, and May 8^thin that order. Because the completion of these tasks is important we made sure to leave time after deadlines for adjustment and revisions. It is allowable to miss a deadline for tasks, but a penalty exists that increases as time passes. To prevent loss of points, additional precautions were put in place. As a group, we set the goal to complete these important tasks and blogs one class day in advance to confirm the completion of tasks within the timeframe.

Fig.24 Gantt Chart pt1

Fig.25 Gantt Chart pt2

Fig.26 Gantt Chart pt.3

Burndown Chart

Fig.27 Burndown Chart

At the start of the semester, our team was quick and productive in submitting material and doing research for the project. Initially, the number of tasks was low and amount of time was high thus, we were more productive compared to the actual workload that was given. As the weeks passed our team fell behind as other classes also increased in workload. The increase of work, unfortunately, caused our group to fall behind on assignments that resulted in our group to work overtime during the spring break. This inrush of productivity allowed our team to regain a proper schedule by the end of our spring break.

Now that we are approaching the end of the semester we are tasked to meeting tough deadlines and yet again when looking at the breakdown chart we can see have more stuff to work on compared to the time that we have. At this time our group has developed a mutual consensus that we need to increase our productivity and work together for the success of our robot.

Summary of Experiments done / Rapid Prototyping Completed

By: Miguel Gonzalez (Project Manager & Manufacture)

It has been approximately eight weeks since the start of the semester and most of the first month consisted of mainly research and write-ups. But after the first month, we began experimenting with small components and sections of our BiPed. We started by looking at the legs of our robot as we knew that making the robot walk on two legs was a crucial part of our design. We created a copy of the 2016 Fall ROFI design and just focused on the legs of that robot. This initial design consisted of having 6 servo motors operating the leg and foot. Using the blog post on that robot and using help from projectbiped.com we were quick to get the robot’s leg to move. If you would like to see images and videos of the robot when it’s operating, you can view our drive folder here. In this configuration, the robot’s leg is very robust and can do very intricate movements while maintaining the robots balance. The issue with this design is that nearly 70 percent of all the weight of the robot consists of the legs alone. We knew that if we can decrease the weight on the robot we could have easier walking movements that in theory can speed up its walking speed. Our secondary design for the robot was to reduce the number of servos operating on the legs by only having four servo motors instead of six.

Fig.28 ROFI vs FOBO

Fig.29 Original Size vs Micro Size

This newer design would remove both the knee servo and middle leg servo on both legs. Theoretically, the newer design should remain functional and provide the ability to take longer strides when walking. It is important to note that the designs for the new leg designs have been modeled and 3D printed but the test will take place on March 17, 2018. This experiment will allow us to verify that the legs can perform walking movement and maintain a higher walking speed than the six-servo design.

Spring 2018: BiPed Preliminary Budget

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

updated: 4/29/2018

Related Requirement

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

Objective

Project BiPed is one of this semesters robot production division in which a bipedal robot will be designed, engineered, and produced by the end of the semester. One of the most important tasks of any project is to evaluate and determine the cost of production of said products. In this post, we will be looking at the estimated cost of producing the BiPed robot. These costs will solely rely on physical component cost and any design and research development cost will not be mentioned in this post.

As part of the requirements stated by the customer, a budget was set for each project divisions. This is a loosely budget of $250 in which all material bought can be reimbursed in full. Any additional items and/or services that exceeded this budget will be covered by the team members working on the project. To help reduce costs, the customer has allowed access to his lab stock inventory of electronics, hardware, and materials. Borrowed items will be included in the budget table but the costs of the items will not be included in the total money spent.

Fig.1 Spring 2018 BiPed Budget Table

Budget Table (for access to links found on the table)

Summary

The above table shows the cost of components we have used and purchased as of April 18, 2018. The budget table above is divided into ten separate columns indicating important information about the used and purchased products. In the left column are the names of the parts and items used by the team to produce the biped robot. To the right of the parts column, is a link section that allows viewers to find the same parts we used for this project online. The table is also set up for invoice collection for any items that were purchased these invoices/receipts are linked on the second column to the right of the table. The budget table tries to incorporate all useful information that may be needed for future part purchases, replacement of parts, and for reimbursements.

Overall, we wanted to make sure not to spend any unnecessary money and to reuse as many electrical components and hardware as we could. It is important to note that some additions to the table will be made as the project continues and more items are needed. Multiple hours of reading past blogs as well as research were done to reduce unnecessary consumption of resources and to allocate as much possible reused parts from previous semester projects. Our total expenditures as of April 18, 2018, is a grand total of $226.54 which is under the customer’s project funding of $250.

References

https://www.arxterra.com/wp-content/uploads/2018/04/Budget-Table.pdf

Spring 2018: Biped Mass Report

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jeffery De La Cruz (Mission, Systems, and Test Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Fig.1 Mass Report

The total mass of the Micro FOBO is at around 351.5 grams. This mass consists of the following:

Part 0: Hip Bracket x1
Part 1: Foot x2
Part 2: Servo Band x4
Part 3: Servo Bracket x2
Part 4: Servo Wrap x2
Part 5: Bearing Frame x1
Part 6: Body Riser x1
Part 7: Electronics Frame x1
Part 8: Head Compartment x1
Micro Servos x8
Samsung ICR18650 x1
Arduino UNO x1
Servo Shield x1
Ultrasonic HC-SR04 x1

To view the excel file of the mass report, click here.

The mass of the Micro FOBO will change because the material used to print the parts of the Micro FOBO will change from regular PLA to carbon fiber PLA. The Micro FOBO will become just lighter but not by much. The mass of the Arduino UNO and servo shield is included at the moment but will be updated once the 3DoT Board of the Sparkfun Pro Micro 3.3V/8MHz is included. Also, the battery case was not included because the position of the battery is to be determined.

References

https://drive.google.com/open?id=1d0iSAl9_i4ClQRSkrW_wMS650_uzvDZU

Spring 2018: Updated Prototype Fritzing Diagram

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jorge Hernandez (Electronic & Controls Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Fig.1 Updated Prototype Fritzing Diagram

This is an updated Fritzing diagram, especially for Micro Fobo. A PCA9865 servo expander was used because we need to drive 8 micro servos and this expander breakout board lets us use up to 16 micro servos if needed. We only need 8 and that is why 8 headers are empty as they are not needed. A TCS9648A multiplexer board was used as we are using 2 UV’s and they will need different addresses If we want to gather information from them individually. This multiplexer board allows us to have 8 of the same sensor all with different addresses but we will only be using 2. We also have an external power source that will be connected directly to the Ultrasonic that is connected to the Pro Micro. The external power source is also connected to the servo expander and the micro servos will need much more than just 3.3V that is provided from the pro-Micro to run.

References

https://www.arxterra.com/spring-2016-rofi-pcb-design-alternative-arduinos-and-custom-eagle-components/

Spring 2018: BiPed Planning and Schedule

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager & Manufacture)

Approved by: Miguel Garcia (Quality Assurance)

updated: 4/21/2018

Objective

The objective of this post is to implement organization for the overall schedule of our BiPed project. This schedule is comprehensive and accounts for all tasks that should be completed by the displayed due dates. Using Project Libre, we can list the tasks needed to have a successful project. By using the Gantt chart feature we can see the tasks in a much more comprehensive chart that clearly demonstrates time frames and work periods. All tasks and due dates listed were imported from our class task matrix.

Overall Goal

Of course, like any project, our goal for BiPed robot is to finish every task on time while meeting our initial level one and level two requirements. To succeed, the following Gantt Chart was created with very precise timelines and due dates for procedural tasks that must be met to succeed in completing the BiPed robot on time. When creating the Gantt Chart, we notice three major tasks that are important to the success of the project. These tasks were the general project plan, finalization of the 3D model, and the final blog post. The deadlines for these tasks are March 15^th, April 12, and May 8^thin that order. Because the completion of these tasks is important we made sure to leave time after deadlines for adjustment and revisions. It is allowable to miss a deadline for tasks, but a penalty exists that increases as time passes. To prevent loss of points, additional precautions were put in place. As a group, we set the goal to complete these important tasks and blogs one class day in advance to confirm the completion of tasks within the timeframe.

Fig.1 Gantt Chart pt1

Fig.2 Gantt Chart pt2

Fig.3 Gantt Chart pt3

Burndown Chart

Fig.4 Burndown Chart

At the start of the semester, our team was quick and productive in submitting material and doing research for the project. Initially, the number of tasks was low and amount of time was high thus, we were more productive compared to the actual workload that was given. As the weeks passed our team fell behind as other classes also increased in workload. The increase of work, unfortunately, caused our group to fall behind on assignments that resulted in our group to work overtime during the spring break. This inrush of productivity allowed our team to regain a proper schedule by the end of our spring break.

Now that we are approaching the end of the semester we are tasked to meeting tough deadlines and yet again when looking at the breakdown chart we can see have more stuff to work on compared to the time that we have. At this time our group has developed a mutual consensus that we need to increase our productivity and work together for the success of our robot.

Spring 2018: Micro FOBO Mechanical Designs

April 19, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Notice

In this blog post, you will learn about initial mechanical designs for the Micro FOBO. We will discuss our thought process for each design component and relate it back to the customer’s requirements. Note that this the first post for the mechanical drawings of the miniaturized FOBO design created by Jonathan Dowdall. New advances in construction and design of the robot will be updated in a future post and linked at the bottom of this page. It is important to note the models shown in this post have yet to be physically tested. But plans to 3D print them have been made and the parts will be tested together. All results will be posted in a follow-up update blog post detailing our results of the models introduced here.

Introduction

The ROFI and FOBO bipeds can be considered as aging robots in which the designs have been used in many occasion for EE 400D projects. This can be particularly helpful if new students like ourselves would like to make such robots, considering resources for these models are plentiful on Arxterra.com. Unlike previous semesters our biped design will not encapsulate the same model but instead be a miniaturized version of those robots. Our group will particularly focus on the FOBO design by Jonathan Dowdall which is found on projectbiped.com. The miniaturized FOBO will be much smaller than the original approximately 60 percent its size and be controlled via micro servos (SG90S). We hope that in miniaturizing the design we can achieve a more efficient way of making the robot walk, turn, and avoid obstacles; all which are some design criteria for the maze.

Related Requirements

Level One Requirements

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

Level Two Requirements

L2-2: Micro FOBO dimensions will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

Micro FOBO Design

For some clarification and for better understanding our design of the Micro FOBO, I have created a color-coded assembly of the robot with matching titles indicating the names of each component. Below I discuss the design of these components that make up the Micro FOBO.

Fig.1 Micro FOBO Colored Parts

As you can see from the image above, the Micro FOBO consist of 9 different parts: Servo Hip, Foot, Servo Band, Servo Bracket, Servo Wrap, Bearing Frame, Body Riser, Electronics Frame, and the Head. Note that Micro FOBO can be made up of multiple copies of the same part component and thus colored coded with the same color. For example, there are four servo bands in Micro FOBO which are shown in light green on the picture. Now that we know which parts make up the robot we can begin looking at the design of each part individually.

Part 0: Servo Hip

Fig.2 Servo Hip

The “Servo Hip” component of the Micro FOBO is responsible for attaching the two upper micro servos which are the hip servos. This bracket connects both servos (right and left legs) together to act as a hip bone that allows the robot to move its legs left to right. The connection to the servos is made via servo horns that are provided by the manufacturer. This part has two allocated trenches that match the dimensions of the servo horns allowing the servos to mount to the part. The horns are then screwed onto the servo hip using M2.5 screws that are 8mm in length.

Drawing File

Part 1: Foot

Fig.3 Foot

The “Foot” component is the same for both legs and is a simple shoe like design with wide pads on its sides. The extra material on the sides allows a greater amount of surface to touch the floor allowing the robot to balance easier. Currently, this part is in its simplified state as there is not much detail design put on it. This is because the team plans on mounting UV sensors onto the bottom of the foot where the hole is located. This would allow the sensor to be as close to the ground as possible to maintain an accurate reading. Once we receive the sensor additional design changes will be made to this part. Currently, the part allows the ankle servo, which is the servo closest to the ground, to be mounted onto one side of the foot though servo horn cutouts. The horn cutout is located on the inside wall of the part. The hole then allows an M2.5 X8 screw to secure the servo onto the foot piece.

Drawing File

Part 2: Servo Band

Fig. 4 Servo Band

There is a total of four “Servo Bands” located on the Micro FOBO. This part is responsible for grouping two micro servos together which forms a section of a leg. The two servos are pressure fitted into the square cutout and thus this part must be dimensionally precise to prevent servos to come loose. This piece had several revisions to satisfy the dimensional accuracy need to keep the servos secure. The servos were measured with a caliper and the thickness of the servos stickers even had to be considered when designing this piece. Due to leg movement constraints, only one servo can have extra material to be screwed onto the part.

Drawing File

Part 3: Servo Bracket

Fig.5 Servo Bracket

The ‘Servo Bracket” is a shorter version of part 0: servo hip and serves a similar purpose. This component mounts onto two servos that are located on the servo bands. This allows the second to the top servo to move the lower leg. This piece is located in the middle of the leg and connects the top and lower sections. This piece can be thought as the knee of the robot. Just like the other brackets, there are two cutout trenches that allow servo horns to be mounted and secured through a single screw. This piece can be varied in length to adjust the height of the robot and adjust the walking stride of the robot itself.

Drawing File

Part 4: Servo Wrap

Fig.6 Servo Wrap

The “Servo Wrap” is a small piece that attaches the back of the hip servo (top leg servo) to be mounted onto part 5: Bearing Frame. It is connected via an M2 screw that is 18mm in length. The screw goes through the servo, through the servo band, and screws into this piece. A hole on the left side of the wall was added to allow the servo wires to feed through and connect back to the electronics. Notice there is a hexagon trench located near the middle of the part. This trench allows an M3 nut to be placed in that location and lets a screw to secure Part 4 with Part 5. Another key design feature is the chamfer cutout located on the backside of the part. This permits higher degrees of movement from the hip servos by at least 45 degrees more.

Drawing File

Part 5: Bearing Frame

Fig.7 Bearing Frame

The “Bearing Frame” is a mirror-like component to part 0 as both pieces work together to provide the connection of legs to body. One of the key differences is that this piece contains two large circular trenches in which a bearing can fit onto. Using a 10mm circular bearing we place it on the part to provide free angular movement to the left and right sides of the pieces. Once the bearings are fitted inside, we can use M3X14 bolts to attach the servo wrap pieces to the left and right side of the Bearing Frame. Since the legs servos are already attached to the servo wrap we effectively attached the two legs to the body of the robot.

Drawing File

Part 6: Body Riser

Fig.8 Body Riser

Micro FOBO mainly consists of a head and two legs but this part, body riser, can be considered the body of the robot. This component connects the two attached legs with the head. There are two fork-like structures located at the top of the piece that allows part 0 and part 5 to fit in snugly effectively connecting the two legs to this piece. Part 0 and part 6 are secured through a couple of M3 screws with an approximate length of 16 mm. The back side of this component is flat and has two holes for connecting to part 7 which is the electronics frame. The body riser can be increased in height allowing the robot’s head to be located higher above the legs. We can experiment with changing the height to allow shifting the robot’s center of mass higher or lower as needed.

Drawing File

Part 7: Electronics Frame

Fig.9 Electronics Frame

The Electronics Frame is a thin component that is responsible for connecting the PCB to the body riser. The PCB will contain four mounting holes which will allow the board to connect to this part. Note that the part contains extruded cubes that correspond to the location of the PCB hole mounts. These extruded cubes also have a hole cut out to fit M3 screws that secure the board in place. Finally, the part can be secured to the head via similar M3 screws on the side of the part and head

Drawing File

Part 8: Head

Fig.10 Head

One of the first challenges in creating a miniature FOBO we observed was that our robot would need to support large amounts of electronic components that used to be on the regular size FOBO. These electronics would need to be smaller in size or our head design would need to optimize to fit all the electronics. Our first design was based on the prediction that the new electronics would have a smaller footprint and thus the head of the Micro FOBO is much smaller. The exact dimensions can be found on the link below. Once the size of the head was set I began to look at some redesigns that I can implement to change the look and functionality of the robot’s head. That is when I stumbled on an image of a tin toy robot from the 1950s.

Fig.11 1950’s Tin Toy

As you can see from the image above this robot has a similar head as the FOBO which gave me the idea of emulating the design of the face. The ultrasonic sensor will take place as the robot’s eyes and the mouth and nose features would simply be aesthetics. Another thing that I noticed was that the tin toy contained antennas on the left and right side of the head. One of the redesigns I wanted to incorporate since the beginning was adding turn signals to the robot and the antennas can certainly be used for that. My idea is to have small 5mm red LED’s as the tip of the antennas that would blink indicating when the robot will turn and in what direction. Finally, we see that there is a small red light on top of the robot that can be designed to indicate on/off status of the robot.

Fig.12 Mechanical Design Improvements

Drawing File Tin Robot Toy

Spring 2018: BiPed Work Breakdown Structure

April 12, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Work Breakdown Structure

For project BiPed, the group consisted of three members fulfilling the roles of Project Manager, E&C, MST, and Manufacturing Engineer. Since the group consisted of fewer members than the positions to fill the manufacturing role of the team was given to the Project Manager.

The diagram below shows the workload of the project and how it is distributed among the team. It is based on the job descriptions and shows major tasks that each person is responsible for. We will be taking a look at each team members role more closely to better understand the structure of the team and its workload.

Fig.1 BiPed Work Breakdown Structure

Miguel Gonzalez (Project Manager)

Fig.2 PM and Manufacturing Engineer Tasks (Blue)

At the top of the WBS in blue, we have the project manager section. Note that in our case the project manager is also the manufacturing engineer and thus the tasks for both roles are given to the same person. The second blue icon shows the tasks specific to the project manager which has the project manager responsible for the following tasks:

Creating and managing schedule
Creating a budget list
Creating the preliminary report
Creating the final blog post
Creating project video
Define Work Breakdown Schedule

The manufacturing tasks given to the project manager are listed to the right side of the WBS also in blue. These tasks are broken down into three sections Mechanical Design, 3D Modeling, and Assembly. These sections were created based on which tasks are needed to be done before moving on to the next section. For example, Mechanical Design is a prerequisite for 3D Modeling and Assemble thus it is located on top of the other tasks.

Jeffery De La Cruz (MST)

Fig.3 MST Tasks (Red)

Moving on to the left side of the WBS (in red), we have all the tasks assigned to the MST engineer. Once again, these tasks are divided up into three sections System Designs, Software, and System Tests. The system designs include tasks that have a focus on research and trade studies that will end up helping with the software development and system test. Once those tasks are done the MST engineer can proceed with implementing the software with the Arxterra control panel and onto an android application. The final tasks for the MST engineer focus on verifying and testing all sections of the robot to see if they are operational.

Jorge Hernandez (E&C)

Fig.4 E&C Tasks (Green)

The final branch in the WBS applies to the E&C engineer and his tasks needed for a successful project. The E&C has the greatest responsibility for the success of the robot becoming operational. His roles are divided into 4 categories Electronics Design, Experiments, Microcontroller, and Control. These categories cover a wide range of taks that need to be realized to proceed with the overall goal of the Biped project which is stated in our preliminary design blog post and here.

Spring 2018: Biped Fabrication Methods (Trade-off Study)

April 12, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Related Requirements

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-18: Micro FOBO shall be able to traverse cloth, paper, and linoleum materials.

Introduction

When thinking about manufacturing our robot we looked at the many fabrication methods available that we could use to create the BiPed. Of course, the list of ways we can manufacture our robot can be endless, but we made sure to focus our research to limit this list. Our goal for this study is to list the most feasible methods of fabricating our robot and compare the pros and cons of each method. The top three most feasible fabrication methods we could implement on our robot was sheet metal folding, laser cutting, and 3D printing. This blog study will look at each method mentioned to see the benefits and disadvantages of incorporating them into our design. Below you can find our study and the results we arrived when conducting a few tests.

Sheet Metal Folding Method

Fig.1 Sheet metal folding example

The first fabrication method we looked at was sheet metal folding which is a process of getting thin metal sheets and cutting them into specific shapes that would be folded to produce a three-dimensional shape. This shape can be a servo mount, 3DoT casing, robot feet, and so much more. Sheet metal folding is cheap and is a good way to produce sturdy parts rapidly without much effort. One of the drawbacks of this method is that complicated designs are almost impossible to produce. Accurately measured pieces are hard to produce and making exact copies of parts that share the exact dimensions are nearly impossible to make using this method. These drawbacks are too big to ignore especially when we plan on creating a robot that requires precision measurements and complicated design.

Laser Cutting Wood

Fig.2 Laser cutting example

The next fabrication method we consider was laser cutting. Laser cutting is a very niche fabrication method for hobbyists but has been gaining traction in the recent years. With the laser cutting method, you can use various materials for your builds such as sheet metal, plastics, and even wood. This method of fabrication utilizes the precision of a powerful laser to cut material into a predefined shape. This means that you can achieve very accurate and precise cuts. Laser cutting, in general, is very versatile but our team realized that we lacked knowledge on how to use a laser cutter. It was also clear that laser cutting would only be used for a section of our robot design and can’t make complicated three-dimensional shapes that extend well above the laser’s cutting threshold. This takes us to the third fabrication method mentioned below.

3D Printing

Fig.3 3D Printing Diagram

Out of all the fabrication methods described in this blog post, 3D Printing was the only method of creating stuff that has been used by a team member. 3D Printing is a fabrication process of creating a three-dimensional object by adding small amounts of material upon itself until the desired shape/object is obtained. There are multiple ways a 3D printer can produce a design, but we focused on an additive manufacturing process called Fused Filament Fabrication (FFF). This is the most common consumer grade process that is readily available.

With 3D printing, we can model our robot’s chassis designs and print them out at the same dimensions specified in the CAD model. This would allow us to expedite the design and manufacturing process in our project. 3D printing also allows us to create precise measurements and make exact copies of parts while maintaining constant measurement accuracy at each copy. With FFF 3D printing we are limited to using only plastic materials but fortunately, we can choose from various plastics that have different properties. In a later blog post, we will be looking at the different materials available for FFF 3D printing and looking at their properties.

Conclusion

After considering all three methods of fabrication we decided that we should use 3D printing to create all the designs in our robot. 3D printing’s only drawback was that it can only produce stuff in plastics, but our team has concluded that plastic has enough robustness to make our robot function and complete the maze. Lastly, our class has been informed that multiple 3D printers are available in house to produce our robot parts and thus this method of fabrication is also the most available for us.

Sources

Fall 2017 BiPed: Preliminary Design Document

September 27, 2017/in 3DoT Biped, Biped Generation #4/by Jain Piyush

By:

Piyush Jain (Project Manager)

Zachary Bruyn & Yasin Khalil (Electronics & Controls)

Natalie Arevalo (Manufacturing)

Melwin Pakpahan (Missions, Systems, & Test)

Table of Contents

Program Objective

By: Piyush Jain (Project Manager)

The objective of Project BiPed is to design and manufacture a miniature bipedal robot. The BiPed shall incorporate a Theo Jansen leg design, use a single DC motor and mini servo for walking and turning, and shall use a similar joint mechanism as the 2017 Spring Velociraptor [1].

The model of the BiPed shall use the same principle mechanics as Theo Jansen models, with the design inspired by the 2017 Spring Velociraptor. The difference between the design shall be:

The head shall be removed and the tail replaced altogether with a different system of allocating the mass to retain a proper center of mass.
Replace clunky hip design with something more compact which has a smaller turning radius.

Mission Profile

The mission of Project BiPed is to design the BiPed to navigate a predesigned maze [1]. The BiPed shall be able to navigate the maze with user input from the Arxterra App/Control Panel. The BiPed will be able to memorize the user-defined path and will be able to navigate it autonomously. In addition, the BiPed will acknowledge other robots while traversing the maze and avoid collisions.

References:

[1] http://web.csulb.edu/~hill/ee444/2%20The%20Mission.pdf

Requirements and Verifications

Program Level 1 Requirements

By: Piyush Jain (Project Manager)

L1-1: The Biped shall be finished by Wednesday, December 13, 2017 [1]

L1-2: The Biped shall not exceed a budget limit of $250.00

L1-3: The Biped Shall be a toy robot.

Project Level 1 Requirements

By: Piyush Jain (Project Manager)

L1-4: The BiPed shall navigate the maze with user-defined inputs.[2]

L1-5: The BiPed shall memorize said user-defined path and navigate it autonomously.

L1-6: The BiPed shall navigate the maze in seven minutes or less.

L1-7: The BiPed shall navigate the maze without colliding into other robots.

L1-8: The BiPed will be controlled by a 3DoT board.

L1-9: The BiPed will be able to walk on cloth, linoleum, and paper.

L1-10: All electronic components shall be able to be disassembled and reassembled within 20 minutes.[3]

L1-11: All 3D printed robot components shall be printed in less than 6 hours, with no single print session taking longer than 2 hours.[3]

References:

[1] http://web.csulb.edu/gobeach/depts/enrollment/dates/registration.html

[2] http://web.csulb.edu/~hill/ee444/2%20The%20Mission.pdf

[3] http://web.csulb.edu/~hill/ee400d/Project%20and%20Mission%20Objectives.pdf

System/Subsystem: Level 2 Requirements

By: Melwin Pakpahan (Missions, Systems, & Test)

L2-1: Operate using the Arxterra Android/iPhone application. This includes navigating the maze, with and without user input, as well as turning and walking. L1-4

L2-2: Have Bluetooth communication which will sync with the Arxterra Android/iPhone application L1-3

L2-3: Be integrated with all the appropriate libraries to communicate with all electronic devices. L1-8

L2-4: Use a gyroscope/accelerometer to help navigate its way through the maze. L1-4

L2-5: Use a proximity sensor to detect and avoid other robots in the maze. L1-7

L2-6: Design the BiPed’s feet size to be approximately 3″ by 2.5″. L1-3

L2-7: Design the BiPed’s hip size to not exceed 3″. L1-3

L2-8: Design the BiPed’s center of mass shifting system to not exceed 5″ in length and width. L1-3

L2-9: Choose a motor which will provide enough torque to support the weight of the BiPed. L1-6

L2-10: Design the BiPed to be less than 1.5 pounds. L1-6

L2-11: Be powered by one RCR123A Lithium Polymer Battery which will operate for a minimum of 10 minutes before recharge.

L2-13: Utilize one mini servo for turning and one for the mass shifting mechanism. L1-6

L2-14: Be wired in a manner which is professional and shall not interfere with when navigating the maze. L1-6

L2-15: Have two leaf springs on each foot, for stability and flexibility of the feet. [1] L1-9

Design Innovation

By: Piyush Jain (Project Manager)

Working from the previous semester’s built BiPed chassis, the team came up with potential problems we might encounter. With respect to the customer’s demands, our main problems were turning the Biped, while maintaining a small turning radius, and the static walk, with the feet in close proximity, all while maintaining a proper balance for the BiPed. We decided we would focus on turning the BiPed as that is the biggest challenge. From our creativity exercise, we surmised different methods of turning including : having a 3″ or less turning gears for the hips, having a joint system similar to humans, and removing the turning gear all together and attaching wheels to legs to drive the BiPed through the maze. The first two methods were thought up during the brainstorming approach, while the last one was thought up during the attritube listing. After going over all our options, we decided to design a turning gear which will be less an 3″ because that will give us the greatest control in how the BiPed turns.

System/Subsystem Design

Product Breakdown Structure

By: Piyush Jain ( Project Manager)

Power

The Biped shall be powered by a singular portable CR123A Lithium Polymer Battery. The battery shall power the 3DoT board, 1 DC Motors, 1 Servos, I2C, and the Accelerometer/Gyroscope.

Actuator

The actuators for the BiPed are 1 DC Motors and Servos. The DC Motor will control the leg movement for walking, while the servo will control the turning mechanism.

Communication

The Software for the BiPed will be in C++ and written in Arduino sketch. The code shall control the motor functions and communicate with the Bluetooth module. The module will be controlled via the Arxterra control panel, synched to an Android or iPhone.

Manufacturing

With the chassis prebuilt, we will focus on creating an optimal design for the hip and feet. The hip shall be able to turn with a small turning radius, to fit within the parameters of the maze, while the feet shall be designed to stabilize the structure. In addition, the center-of-mass distribution shall be manufactured as to maintain a center of balance when walking and turning.

PCB

Our design will incorporate two PCB boards. The first will be the 3DoT board, provided by Professor Hill, which will contain the microcontroller and shall control the servos and motors. The second will be the custom PCB board which shall control everything else.

Electronic System Design

System Block Diagram

By: Zachary Bruyn (Electronics & Control)

The Microcontroller has inputs of the battery and input sensors. The battery shall power the BiPed and the Input Sensors; accelerometer/gyroscope and proximity sensor help to navigate the BiPed thru the maze. The Actuators; DC motors and servos help to physically move the BiPed. The communication device includes the Arxterra application, control panel, Android/iPhone, and Bluetooth device give the user the ability to control the BiPed.

Interface Definition

By: Melwin Pakpahan (Mission, Systems, and Test)

The interface definition shown below defines the pins of the ATmega32U4. The microcontroller has a modest selection of programmable pins to configure. In the future, trade-off studies will be conducted to determine which resources would best suit components and how to configure them accordingly [1]

Reference:

[1] https://www.arduino.cc/en/Hacking/PinMapping32u4

Mechanical Design

By: Natalie Arevalo (Manufacturing)

The overall design of this semester’s BiPed project can be broken down into four major sections: feet, legs, hips, and center-of-mass shifting mechanism.

The project as a whole can be seen as an iteration of the Spring 2017 Velociraptor project or modification of the Velociraptor project into a BiPed. As a result, the design of the BiPed will be kept as top-heavy however the head-tail component of the velociraptor will be eliminated. Although the body of the BiPed will be kept heavy to keep its moment of inertia small, the weight will be kept confined to the center-of-mass shifting mechanism as well as the servos and motors. In addition, stability in the legs and feet will be increased by using different materials as that of the previous project for the feet as well as by making the feet bigger to better distribute the weight along to using different springs.

Feet

The size of the feet will be increased so that the weight of the top-heavy robot can be better distributed as it’s walking. Additionally, the shape of the feet was also modified to minimize the amount of material to be used in the manufacturing. Since most of the weight of the robot will be exerted on the corners of the feet, just like how the weight of humans is placed on the toes and heels of the foot, the shape was kept with four major corners.

Back of envelope design

A trade-off study in conjunction with a simulation in SolidWorks will be later conducted to determine which design will work the best for the BiPed. Furthermore, the feet will be incorporated into the BiPed so that they can hinge as the robot takes a step. To increase the stability of the feet and therefore the ankle part of the robot, a leaf spring will be used in place of a traditional spring. The leaf spring will provide the better stability while still maintaining enough flexibility for the foot to flex at every step taken.

Legs

The leg design from the Spring 2017 Velociraptor project will be kept the same. The design used previously is the linkage system found in the Theo Jansen Walking Biped. The linkage system already mimics the kinetics behind walking. Furthermore, the design eliminates the need for taking into account the hinge movement of the knee since the leg rotates at the hip and creates that movement on its own.

Leg Design Model from Wiki [1]

Reference:

[1] https://en.wikipedia.org/wiki/Jansen%27s_linkage#/media/File:Jansen%27s_Linkage.svg

Hips

The hips as a whole are being made smaller in width so as to make them have a tighter look them. This is going to be accomplished by making gears in the hips that allowed the velociraptor to turn have a smaller radius. Additionally, the space between the universal joint and the rotating disk of the hip/leg will be made much smaller. With these two modifications, the hips will be made smaller in diameter which will decrease the distance of rotation during turning as well as decrease the time it takes the robot to turn and therefore navigate the maze. A quick Solidworks model is provided below based on preliminary talks on the optimal design.

Center-Of-Mass Shifting Mechanism

In order to modify the velociraptor design into a BiPed, the head-tail component was completely eliminated. As a result, a center-of-mass shifting mechanism had to be created in order to shift the center of gravity of the BiPed as it is turning so that the toy will not fall over during this motion. The inspiration for the mechanism came once again from the Theo Jansen Walking Biped. The weight shifting mechanism used in this robot can be seen here:

Essentially, this mechanism would be implemented in an automated version instead of a purely mechanical way. A weight will be placed as part of the body of the robot that will be slowly shifted by a motor to the opposite side of the pivot point of the BiPed as its turning. The modeling and simulation of this mechanism will be done in the future.

Design & Unique Task Description

By: Piyush Jain (Project Manager)

The BiPed shall incorporate a single 3.7v battery which shall power the BiPed through the three maze trials. The battery will be able to be recharged in between the trials. The BiPed shall use one mini servo and one DC motor to help turn and perform a static walk. The turning mechanism shall employ a small turning radius. The static walk shall ensure that the feet are kept in close proximity.

BiPed Tasks

Conduct trade-off study to choose the optimal DC motor and servo for given parameters. – October 11th
Create the fritzing diagram to test the breadboard. – October 10th
From the fritzing diagram create PCB on Eagle CAD. – October 16th
Using Arduino IDE to create control algorithm for the servo and DC motor – November 29th
Design Center of Mass part to maintain balance during walking, turning and stopping. – October 29th
Design lightweight and efficient models for the legs and hip. – October 15th
Configure proximity sensor to detect other robots while traversing the maze. – October 6th
Create Interface Diagram which is compatible with both 3DoT chassis and BiPed. – October 11th

Work BreakDown Structure

By: Piyush Jain ( Project Manager)

The Work Breakdown Structure displays in an easy to read manner for the tasks which need to be completed by the respected division engineers. It details the kind of work which has to be done, moving forward, in order to have a successful BiPed by December 13, 2017. The tasks were derived from the Lv 1 requirements agreed upon by the customer.

Project Schedule

By: Piyush Jain (Project Manager)

The Project Schedule details the project timeline from a Top-Level/Subsystem Level perspective. The Top Level consists of four main sections; Planning Phase, Design Phase, Assembly Phase, and Project Launch. These four sections help to guide the project towards mission success by breaking the work down into realizable goals.

The System/Subsystem Level was designed to complement the Work BreakDown Structure. It details the specific work which needs to be done by each engineer in their specific division. It allots specific time to each task such that the project will be completed by December 13, 2017. It is broken down into the Manufacturing, MST, and E&C division.

Top Level Schedule

System/Subsystem Level Tasks

Burn Down

By: Piyush Jain (Project Manager)

The Burn Down Schedule shows the amount of work needed to be completed in order for the mission to be a success. The blue linear line shows the ideal schedule for the amount of work per week. The orange line indicates the actual work to be done. As shown, the work increases in loads as the semester progresses.

System Resource Reports

By: Melwin Pakpahan (Missions, Systems, & Test)

The Lv 2 requirement for the BiPed is to be under 850 grams or roughly 1.5 pounds. This was selected so the BiPed would be able to traverse the maze in a timely manner. A rough mass report was generated to guide us to hit our Lv 2 requirement. According to this report, we are well under the 850 grams. Our biggest item of uncertainty is the frame of the BiPed. It is estimated to come in at 300 grams, which is 200 grams less than the previous semesters’ design.

A preliminary power report is provided below. The power report is missing much of the Electronic & Control engineering work because we had many problems with the engineer. By October 25th, 2017 we shall have an updated power report.

Project Cost Estimate

By: Piyush Jain (Project Manager)

The main program requirement for this BiPed is that it shall not exceed $250.00. A project budget cost was formulated with this requirement in mind. As seen by the image below, we are well below the limit of $250.00. We are able to reduce the cost of this project by obtaining several times from Hill, including the DC motor and mini servo. Also, the sensors decided will be of low cost and optimal performance. The main cost of the project will be the frame of the BiPed because we decided to incorporate a more compact, yet sturdy design. The item of most concern is the custom PCB. Even with a $10 estimate, based on a quick research, we will need to conduct a more in-depth research as to which companies can provide us a high quality, low-cost single board.