By:

Piyush Jain (Project Manager)

Zachary Bruyn & Yasin Khalil (Electronics & Controls)

Natalie Arevalo (Manufacturing)

Melwin Pakpahan (Missions, Systems, & Test)

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:

1. 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.
2. 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.

 

By: Abraham Falcon (Electronics and Control)

Approved by: Alexander Clavel (Project Manager)

Introduction

The electronics and control engineer job is to find the right equipment and test it for its project functionality. To make sure the biped can participate in the game it must have a color sensor to detect the red dots placed on the floor. This experiment was done to see if the adafruit color sensor can sense red and to discover what the best range of detection is. As per the requirements of our project, this test was able to verify that we were indeed able to detect dots as well able to detect the dots at the specified distance of 2mm.

Equipment

Material	Quality
Arduino Uno (any family of Arduino)	1
USB Printer Cable	1
Breadboard	1
Male to Male Jumper Wires	4
Color Paper (Red) (Any objects that is red in color)	1

Table 1

Arduino Code

The code below is from adafruit which can be located in the reference section of this post. The purpose of the following code is to be able to give feedback on the raw data of the colors. We were able to test this by placing different colors under the sensor and observing the given data.

#include <Wire.h>

#include “Adafruit_TCS34725.h”

Adafruit_TCS34725 tcs = Adafruit_TCS34725(TCS34725_INTEGRATIONTIME_700MS, TCS34725_GAIN_1X);

void setup()

{

  Serial.begin(9600);

}

void loop()

{

  uint16_t r, g, b, c, colorTemp, lux;

  delay(25);

  tcs.getRawData(&r, &g, &b, &c);

  colorTemp = tcs.calculateColorTemperature(r, g, b);

  lux = tcs.calculateLux(r, g, b);

  Serial.print(“Lux: “); Serial.print(lux, DEC); Serial.print(” – “);

  Serial.print(“R: “); Serial.print(r, DEC); Serial.print(” “);

  Serial.print(“G: “); Serial.print(g, DEC); Serial.print(” “);

  Serial.print(“B: “); Serial.print(b, DEC); Serial.print(” “);

  Serial.print(“C: “); Serial.print(c, DEC); Serial.print(” “);

  Serial.println(” “);

}

This code using the raw data from previous code from Adafruit will now check for red color since it is part of the requirements for the BiPed.

#include <Wire.h>

#include “Adafruit_TCS34725.h”

Adafruit_TCS34725 tcs = Adafruit_TCS34725(TCS34725_INTEGRATIONTIME_700MS, TCS34725_GAIN_1X);

void setup()

{

  Serial.begin(9600);

}

void loop()

{

  uint16_t r, g, b, c, colorTemp, lux;

  delay(25);

  tcs.getRawData(&r, &g, &b, &c);

  colorTemp = tcs.calculateColorTemperature(r, g, b);

  lux = tcs.calculateLux(r, g, b);

  float ColorAverage, RED, GREEN, BLUE;

  ColorAverage = (r + g + b) / 3;

  RED = r / ColorAverage;

  GREEN = g / ColorAverage;

  BLUE = b / ColorAverage;

  if (RED > 1.4 && GREEN < 0.9 && BLUE < 0.9)

  {

    Serial.println(“RED Detected”);

  }

}

Experiment

To perform the experiment, the color sensor was placed on the breadboard for easy connection. The color sensor itself  has four connections and the Arduino was powered by the computer through USB connection. The four connections that are being used are SDA, SCL, Vin and GND. Vin and GND are connected respectively to the Arduino for 3.3 volts and ground. Below is how the color sensor is connected to the Arduino to the computer.

Figure 1

Figure 2 shows the mini breadboard we were using to test the actual sensing of the color red. There were various other objects of different sizes and colors that were used to see whether or not the sensor is was picking only red or if there were any errors of any kind. We did not want the sensor to pick up a bright orange when what we really wanted was red. We were able to verify that it only detected red and on any other color would not light up the LED counter.

Figure 2

To conduct this test, the red mini breadboard was placed on top of the sensor to detect red and to see how this color sensor performs. Figure 3 shows the set up and how the test was actually performed. This was the first step to show that the components were performing the way we wanted it. Once we had verified that it was picking up red and only counting the red objects we then moved on to trying to find the optimal distance.

Figure 3

Figure 4

Figure 4 shows the test that was done to find out the operational range of the color sensor. The setup was very basic in the way that the color sensor was connected to the Arduino and placed side ways. A tape measure was placed along side it to indicate distance. The red mini bread board was then placed at varying distances. We initially put the sensor an inch away from the red object, but nothing was detected. From there we continuously moved the red object an eighth of an inch closer and closer until the red color was detected. The resulting distance happened to be about half an inch. This distance is well over our required detection distance of 2mm.

Analysis/Data

Table of Results

Color Sensor	Operating Voltage (Volts)	Operating Range for Biped (Inch)
Adafruit RGB Color Sensor	3.3 V	0.5 in

Table 2

Raw Color Data

Figure 5

Figure 5 shows the raw data for the colors, which are red, green, and blue. This sensor detects and uses this raw data as a reference code to be implemented to detect red for biped function. The raw data shown is sensing red green and blue, but the point was to take account of the red values. To do this we took the red, green, and blue raw values to a sum which will be called the average. So we then used the total raw values and then divided the specific color raw values to get the ratio of those colors from the sensor raw data. Using this ratio, we can make conditions where it reads only red when these conditions are true. In the section of Arduino codes, the code for reading red is provided. This code will help detect red and to be use for biped main code.

Arduino Serial Monitor Test of Detection

Figure 6

Using the previous codes to detect red the red mini breadboard was detected and shown on the Arduino serial monitor. This code is successful for detecting red and will be used for biped main code.

Conclusion

Performing this color sensor experiment we can see that this sensor will operate successfully for the biped to participate in the game. This sensor will help the biped be able to read red dots placed on the floor. It also shows that the color sensor will perform well and beyond the range of what is actually required. In conclusion the tests were successful and showed that the mission is achievable.

References

1. http://www.makerblog.at/2015/01/farben-erkennen-mit-dem-rgb-sensor-tcs34725-und-dem-arduino/
2. https://learn.adafruit.com/adafruit-color-sensors?view=all – programming

By: Alexander Clavel (Project Manager)

Approved By: Alexander Clavel (Project Manager)

Introduction

This post will cover an updated design of the last prototype as there were issues with functionality and acceptability by the customer. From the last design we had, it did not account for shifting the center of mass at all and had no way to balance its self during each step. Instead it used overlapping feet in which case was pointed out by the customer as unacceptable. This new design incorporates a similar gear box as the last with modified feet and an added balancing system.

New Design

Figure 1

The main difference between with the new prototype is the ability to shift its center of mass. That was also the main issue with the customer as he pointed out the sloppy and sluggish walking movement of the last prototype. Figure 1 shows what the new design is centered upon which is a tilt box with a moving ball bearing. The idea behind it is that as the BiPed takes each step, the box will tilt and roll the weighted ball to shift the center of mass onto the other foot. Timing was a big issue with this design as the mass had to be shifted just as the opposite foot was being planted to become the main support. If it was done too early or too late then the robot would have fallen over.

Another central design change is that instead of putting the DC motor slightly to the side, I put it directly into the middle as shown in Figure 3 below. This plays an important role in keeping the center of mass in the center and making it easier to shift the mass from one foot to the other. In this entire system as shown in the picture, the DC motor is what takes up most of the weight. As it is, the entire system weighs less than 200 g. What this means for the robot is that most of the weight is placed lower to the ground. This makes it easier to achieve static walking and keeps it more balanced as opposed to placing most of the weight at the top.

Method of Balancing

Figure 2

Figure 3

Figure 4

Figure 2 and 3 shows how the robot would stand on one foot to stay balanced. In figure 2, the box is shown to be tilted and in which case the ball bear is sitting on the left side (right side of the picture) of the robot allowing it to stand only on the left foot. Figure 4 shows the placement of the bearing  when shifting to one side. The feet in the images are a “C” shaped configuration, but it should not be confused with overlapping as in the last prototype. It is to be noted that the shape of the foot could be manipulated very easily, but for the sake of testing how balanced it would be, they were made to be large enough to be certain that it would cover wherever the center of mass shifted to.

This was the starting point to moving forward with the product. There are requirements stating that the BiPed should be able to statically walk which by definition is being able to maintain it’s balance throughout each stage of its walking. It should also still be able to stay upright even when power is shut off. This design evidentally works as shown in the pictures as there is not power attached to the robot but still is able to remain standing.

Walking & Static Balance Experiment

The design as shown in the figures above was not enough to keep it walking continuously. There was another CAM that was needed to be able to tilt the box back and forth. The completed prototype and design is shown in Figure 5 below.

Figure 5

Figure 5 shows the Biped in mid step as it starts to lift up its right foot (left side of the picture) and starting to shift its weight. The leg CAMs and the box CAM are all connected through to the same motor and share the same gear ratio so that the rotational speed is synced perfectly. As the feet are turning, the small pegs on the long metal shaft are rotating at the same rate. The position of the pegs is what allows for the shifting of the weight at the opportune moment. As a peg completes a rotation, the more elongated part of the peg will make contact with the box and tilt it up inevitably rocking the ball bearing to the opposite side. This took much trial and error to find the optimal positioning.

Once the optimal position was found, I connected the motor to the battery and let it run freely. The result was that it walked exactly as I wanted it and it was able to stay stable throughout the entire walk. Here a short video can be found as to the actual walking footage and balancing test.

Conclusion

In the end, static walking had been achieved but can still be improved on. The robot is able to statically walk but the inertia of the moving ball does seem to have a slight affect on the robot as it rocks the biped slightly. It is still able to walk in a straight line but it can be improved upon. The final design should include something to dampen the ball bearing like perhaps a sponge or spring as to soften the momentum. This should prevent the robot from any sort of falling due to any kind of sideways momentum.

By: Alexander Clavel (Project Manager)

Approved by: Alexander Clavel (Project Manager)

Introduction

The BiPed projects goal is to be able to create a walking bipedal robot that is able to perform static walking. The definition of static walking is walking that remains constantly balanced throughout the robots entire walk. In theory, when the power to the robot is cut off, the BiPed should stay standing and balanced. This is one of our main requirements. This blog post shows the process of building one of the prototypes.

Design/Construction

The overall construction which included buying all the parts and materials and then assembling them together took a little less than a day. We decided to go with a design that was found through reserach on youtube of walking bipeds. We were looking to find something simplistic as to be able to stay light on the material as well as the power draw on the electrical components. The BiPed we based this prototype off can be found here in a video. In the video, the biped uses a straight leg with no linkage and uses circular motion to walk forward. It is also a very small design that reaches a little under 20 centimeters in height which is something we would like to incorporate in ours.

Gear Box

Figure 1

Figure 2

This was the first attempt at using a gear/pulley combination to drive the robot. The white round gears on the outside of the wood area in figure 1 show the rotational movement that the legs would be taking during the walking motion and the actual legs would be connected to the metal pegs sticking out. The rubberband in the pulley in figure 1 would wrap up to the pulley that is attached to the motor in figure 2. I tried using a 1 to 1 ratio for the pulley on the shaft to the pulley that will drive the 2 gears next to it. From reasearch done and experience with cars, I learned that using a smaller radius for the driver to a larger radius produces more torque, but less speed. For our requirements we will be needing that torque to be able to drive the robot, but we will also need to keep it fast enough to pass our speed requirement. From this reasoning I tried a 2 to 1 or 3 to 1 for the purpose of testing the walking motion. The two additional bevel gears in figure 2 were to work towards a solution for the balancing problem, but it was never completely finished due the professor not liking the design of our feet (which overlapped each other) so the design was to be changed anyways.

Leg Design/Movement

Figure 3

As stated before, there is a single wooden board for the legs that use a rotational motion for the legs. Figure 3 shows a side view of the gear box where the legs would be attached. The bottom of the robot is to the right of the image. This being just a test, I placed the pegs very close to the shaft because I just wanted to at least see if it would rotate. The final product would have to have a larger radius from peg to shaft so that the robot will be able to get a decent distance with each step. Again our design was kicked back because the feet  that were attached were overlapping to account for the balancing. Without the overlapping feet, the balancing mechanism at the top of the robot would have had to be completed.

Conclusion

Figure 4

Figure 4 shows the entire main body of the biped attached. Again the rubberband is connected from the pulley in the gearbox to the pulley driver connected to the motor. The legs were not added to the image, but again, they are connected to the metal pegs sticking out on the sides. To restate it, the gear at the top of the robot is vestigal at this point and doesn’t serve a purpose for this prototype but should play a bigger part in the final product. When completely assembled, the robot shows that it does indeed give a clean walking motion while being held in the air. When placed on the ground the robot does “walk”, but it was a very rough, sloppy, and unbalanced motion. As it moves forward it does wobble side to side to a large degree, but at a very slow pace. Concluding comments would be that:

• It does perform a walking motion
• It does not stay balanced without the overlapping feet unless a balancing mechanism can be created
• The walking speed is very slow.

There will need to be more adjustments to the prototype for application on the final product.

Referrences

1. http://www.blocklayer.com/pulley-belteng.aspx
2. http://tech.txdi.org/gearsandpulleys
3. https://www.youtube.com/watch?v=Z7N0xCDVzIA&feature=youtu.be

By: Abraham Falcon (Electronics and Control)

Approved by: Alexander Clavel (Project Manager)

Introduction:

Electronics and Control engineer job is to do an experiment on the servo motor to see if it can the handle the weight needed to perform the funtion of turning at the ankle. The following experiment is to know if the chosen servo motor can handle the Biped’s weight. The stress weight of the Biped was chosen to be at 500 grams as to be the maximum weight, but our actual weight should be lower than this. The experiment is also to see if the power consumption of the servo will exceed our maximum of 500 mA.

Experiment:

Table of results:

Servo Motor	Servo Location	Stress Weight	Operating Voltage (Volts)	Stress Current (Amps)
HXT900 Micro Servo	Ankles	500 grams	3.3 volts	270 mA

This experiment was done by hooking up the servo motor to the arduino and the digital multimeter in series. The weight of 500 grams was attached to a servo plastic gear with a radius of 1cm.

 

Here is an example of the servo connection without the weight and you can see that with no load the servo runs at the highest 71.961 ma.

The setup from above picture was used but added the weight of 500 grams. To simulate the weight of the ankle from Biped weight the servo was put upside down and observed if the full rotation of the gear on the servo with the weight performs well. By observing the weight on this servo, it can handle the stress weight of the biped and the current was around 270 mA.

Conclusion:

The experiment was preformed and showed that this HXT900 Micro Servo will make Biped be able to turn on the ankles and the current shows that the power consumption is under 500 mA. This experiment concluded that this servo will be effective for the ankles to turn. In the references section shows a video of the servo torque test of this type of servo chosen and this was a guide to perform this experiment.

Referrences:

1. https://www.youtube.com/watch?v=dCgiE0xpToI&index=11&list=FLoSP5pt7W0bsWc1xuJASmww&t=168s