Members and Communities – Page 133

Dimension Determination

May 10, 2014/in Communites, Members and Communities, UFO, UFO Generation #2/by arxterra

By Juan Montano

In this study, we will try to determine the appropriate dimensions for the UFO. To meet the customer’s requirement that it should look like the UFO from the movie, the day the earth stood still, we worked off of the picture (shown below) that he thought best represented the UFO from that movie.

Using that as our guide, we modified the picture, using the free drawing software called GIMP, to include the remaining parts of the UFO and to try to extract only the edges from the UFO as shown below.

Once we had that complete model, we were able to extract the measurements from the drawing itself by measuring the amount of pixels this drawing took up in for certain areas. Below we show the measured out areas.

Now to visually compare the original picture with our measured 3D model we have:

These two look approximately the same, we can increase the number of points used to get the top portion of the dome to get shape more accurately if needed.

Now that we know we have the correct shape, we will want to resize the dimensions to get realistic measured values.

We currently have:

X=length of base=477 pixels

Y=height of UFO=145 pixels

X1= length of 2^nd base = 417 pixels

Y2= height of dome from 2^nd base=76 pixels

Y1= height base=69 pixels

Dz= distance between curve points=45 pixels

Zi= height of curvature from 2^nd base=7, 18, 45, 67, and 76 pixels

R= radius of dome=100 pixels

We will extract the ratios of lengths based on the length of the base therefore we will have:

T= total Height/length ratio:

Y/X= 145/477=0.3040

B= base 2 to dome ratio:

R*2/X1= 200/417=0.4796

YY= Height/height ratio:

Y1/Y, Y2/Y= 69/145, 76/145= .4759, .5241

RX=radius/length:

R/X= 100/477= 0.2096

Zy= ratio of height curvatures:

Z/Y2= 7/76, 18/76, 45/76, 67/76= .0921, .2368, .5921, .8816

Angle between two bases:

Arctan(Y1/((X-X1)/2))= arctan(69/30)= 66.5 degrees

Given the 50 mm fans from the customer, we would like to construct the appropriate dimensions for this UFO. To keep the same shape as the UFO, we would like to mount the fans in the relatively flat part of the second base. Therefore we have:

Fan= 53 mm (59mm at the top)

53+53mm = x1-2*R= 106mm (108mm), since we know B, we can determine X1,

X1= 106/(1-B)= 203.7 mm +/- 10mm (226.74mm)

Since we know x1, we can find the radius of the dome

R= x1*B/2= 48.8 mm +/- 10 mm (54.37mm)

Since we know R, we can find the Base/total length of the ufo:

X= R/RX= 233.03 mm +/- 10 mm =9.17 inches (259.39mm =10.21in)

Since we know X, we can find the heights of this UFO, which we get:

Y= X*T= 70.84 mm +/- 10 mm (78.86mm)

Y1=Y*yy1= 33.71 mm +/- 10 mm (367.53mm)

Y2= Y*yy2= 37.13 mm +/- 10 mm (41.33mm)

Since we know Y2, we can find the ratio of height curvatures:

Zi= Y2*Zy= 3.41, 8.79, 21.98, 32.73 mm +/- 5 mm (3.8,9.7,24.47,36.43mm)

Thus now we have all the dimensions we need to create this 3D model.

Appendix A:

The requirement of landing on the hand was considered previously. In consideration of the future, which may change the fans, here is a brief discussion on the dimensions using that requirement:

To land on one’s hand, the base of the UFO must be proportional to the size of the customer’s hand. Using the average hand size for a male, 189×84 mm, and assuming the UFO would be lightweight (as determined by the Number of Fans test, no more than 1104g), the UFO would be reasonably land on the hand as long as the diameter is no larger than 1.5xsize of the hand.

1.5×189=283.5 mm (UFO diameter based on hand length)

1.5×84= 126 mm (UFO diameter based on hand width)

Taking the average of the two above would yield 204.8 +/- 20 mm (8.06 in) UFO max length. Once we know the diameter of the UFO, the rest would follow using the ratios mentioned above.

Thus, we determined the dimensions of this UFO, however, there is a safety issue in considering the fans. Using the provided 50 mm fans, part of the fans would be in the way, making it unable to land on one’s hand. We can resolve that issue by making it larger, however, that would also not land on one’s hand reasonably (it would become a balancing act). Besides switching out the fans with some smaller fans, there are two methods we will mention to try to resolve this issue.

Our first idea would be to separate the fans away from the area from which the UFO would land on. That is, we create two sections: land section, and fan section. Below we show an example of such a model:

The land section would have to be on the area where the center of mass is located, ensuring the UFO would land on the hand. The dimensions of that area are similar to before. The fan area would have to be separated from the land section by at least half an index finger length (average would be 4 inches for index finger length) in consideration of safety. The fan section itself, would only need to be as large as the fans themselves, the rest would follow while taking into consideration the UFO model from the movie (which the picture above does a terrible job at). We can make this separation visible only from the bottom to preserve the UFO’s original look if necessary.

Our other idea would be implement some landing gear, namely the exit. We can include an exit stair case beneath the UFO which would serve as the place where the customer would hold onto the UFO. The inclusion of landing gear (which the customer expressed a want for), would allow the UFO to land on a flat surface as well. The length of such hand held exit would have to be around the width of the hand which is 89mm. Taking into consideration the height of the UFO would be around the same, we would have to implement ways of making that shorter, however the idea behind that would look like this:

Heat and Power Problems

May 10, 2014/in Communites, Hexapod, Hexapod Generation #2, Members and Communities/by arxterra

By Tien Dang

Introduction
Power level, power lost, and heat product are the problems that we need to maintain during testing and demoing period. To maintain the power level, we need to use a voltage regulator (https://www.arxterra.com/voltage-regulator), but power lost and heat product are always there, all we can do is deduce them to a minimum level; we can’t get rid of them.

Reducing Heat Product
When using a step down voltage regulator, a massive production of heat will be produced. The reason of this heat problem is because the different Voltage of the battery (7.4 V) and the output of Voltage regulator (6V). This difference will form extra energy, which is heat. For a long period of time, this heat will be a thread and cause fire if we do not deduce it. To prevent this problem from happening, we installed two small heat sinks under and one small fan next to the Voltage regulator.

Figure 1: Voltage regulator andHeat Sinks

Figure 2: Fan and Battery

Heat sinks do not need power, so we do not need to apply any power to them; all we need that is attach them under the Voltage regulator so they can suck out the heat however the fan needs power to turn it on. For our project, we will use a separate battery (as show in Fig. 1) to minimize the power drain from the main power source.

Minimizing Power Lost
Beside the power lost due to heat converting while use Voltage regulator (which is unavoidable), the power may lost while the robot is stand by, but the power is still in the power outlet. To prevent this, we attached an On/Off button to the main battery. So we do not have to worry about the power lost while the robot is standing by.

Figure 3: A switch is attached to battery

Conclusion
Heat and power lost are unavoidable, but we can minimize them. Adding button to main battery, installing heat sink under Voltage regulator, and connecting a small fan next to Voltage regulator are solutions of our team. After the tests that we performed to test the movement of the Hexapod, we could see that these solutions are working very well. The voltage regulator is not getting hot or smoked, and battery can be used over ten minutes without running out of power.

Spiderbot Schedule

May 7, 2014/in Communites, Members and Communities, Spiderbot/by arxterra

By Kristine Abatay – Project Manager

In true undergrad fashion, the completion of Spiderbot is behind schedule. An image of the updated schedule is posted below, along with the allocation of tasks for the group members in the Gantt chart below it:

As anticipated, the printing of 3D parts for Spiderbot had to be pushed back with the increasing need of 3D printed parts from other projects. We are very satisfied with the turnout of our pieces, so many thanks to Manufacturing Division Manager, Ali Etezadkhah for his hard work and for offering his 3D printer in the first place.

Difficulties were encountered with the initial casted Spiderbot component (the tibia). The original casted pieces were much too heavy for the servo motors to handle, so our manufacturer worked hard to develop a modified method that would produce pieces that were lighter in weight. Unfortunately, this hard work caused manufacturing dates to be pushed back as well.

Servo tests were initially not properly run, which caused the breakdown of one of the servos that needed to be tested. The completion date of this task was later due to availability of the group members and our designated systems engineer, as well as a modification of the nature of the overall test for proper testing late in the game.

Due to unforeseen issues that occurred with prototype Chop Suey, coding of Spiderbot has also been pushed back to an extremely optimistic and risky completion date that will truly be a test of the group’s determination and work ethic.

Many lessons have been learned as a result of these unfortunate delays. A majority of these delays were caused by hurdles that needed to be overcome in order for proper materials studies and tests to be conducted, which is a good reason for delay.

Periscope!

May 7, 2014/in Communites, Members and Communities, Spiderbot, Spiderbot Generation #2/by arxterra

By Simon Abatay – 3D Modeling & Manufacturing

This semester, Spiderbot will try out a new method for the pan and tilt portion of the robot. The pan and tilt portion of Spiderbot was designed so that the placement of the smart phone with the Arxterra app will be flat and face-down. This can be seen in the SolidWorks design shown below:

In this position, the smart phone will be unable to capture live video of the objects in front of it while in motion. To remedy this, an A8022 periscope will be attached by magnet to the smart phone camera.

This product can be found at this website for a fairly cheap price:

http://www.dx.com/p/a8022-creative-periscope-attachment-for-iphone-ipad-black-206277#.U2mRyvldUSM

This attachment maintains the original image quality of the smart phone and offers a good field of vision for the Arxterra Control Panel display. A video of this attachment in use can be found at the following link:

http://youtu.be/KZ8glROwRx4

Chop Suey: Chopped

May 7, 2014/in Communites, Members and Communities, Spiderbot, Spiderbot Generation #2/by arxterra

By Matthew Clegg – Computer & Control Systems

Many issues were faced when working with prototype Chop Suey. During the initial stages of coding, a single servo was connected to a single breakout board, with power being supplied by a DC power supply in a CSULB classroom. When code was uploaded, the servo would execute what it was instructed to do. This was the case when servos were connected for two legs of Spiderbot (6 servos, 3 servos per leg).

When more than two legs were connected to the breakout boards, Chop Suey seemed to have a mind of its own. Since the cause of the issue was not known, current was increased to its maximum for 6V on the power supply. The same issue occurred, so different inputs of the power supply were tried. The best results initially occurred when the leads for the breakout boards were connected to the fixed voltage and fixed current inputs for the power supply. After discussion with the creator of Chop Suey, David Gonsalez, it turned out that similar issues were faced in the previous semester because the DC power supplies do not provide enough current for sufficient control of all the servo motors used by Spiderbot.

Though this input allowed for better control of the servos, it ultimately caused one of the breakout boards for Spiderbot to smoke and no longer function properly. In that situation, too much current was being provided to the boards.

Luckily, Hexapod, Spring 2014 had extra breakout boards for purchase, so Spiderbot group is very grateful for that. The upside of this downfall, however, is that the reasoning for using breakout boards as a form of protection from damage for the Arduino and the servo motors has been verified, seeing as to how our Arduino Uno and all of our servo motors are still operating properly.

Mold Case Study

May 7, 2014/in Communites, Hexapod, Hexapod Generation #2, Members and Communities/by arxterra

By Vinh Kim, 3D Modeling and Manufacturing

Introduction:
Here I did a study on Silicone rubber (Mold Max 40 vs OOMOO 30) vs. Polyurethane rubber. The Mold Max 40 was the silicone rubber the fall 2013 Hexapod team used. I want to give our regards to Ramon Luquin (Fall 2013 Hexapod Project Manager) for donating his mold and casting material to our team.

Durability:
Here we want the rubber to be flexible as much as possible, so it does not break when bending. Therefore, we will take a look at the Elongation at Break and Tear Strength number from www.smooth-on.com.

The Elongation at Break is when the material breaks after it being pulled apart and the Tear Strength is the material that resistance to tearing. As shown in the Figure 1 and 2 that I am bending the rubber with my hand and it did not rip or pull apart.

Figure 1: Mold Max 40 Rubber

Figure 2: OOMOO 30 Rubber

Product Name:	Elongation at Break	Tear Strength
Mold Max 40	250 %	120 pli
OOMOO 30	250 %	40 pli
Vytaflex 60	480 %	136 pli

Durability Winner:

Vytaflex 60
Mold Max 40
OOMOO 30

Mixing Viscosity:
Here we will look at the viscosity. I noticed that if the viscosity has a very low Centipoise (CPS) number than it will flow really easy and does not need to be vacuum degassed when mixing. If it has a high CPS number, than it requires vacuum degassing to remove all the air when mixing because it does not flow easily which will create a lot of air bubble.

Figure 3: Mold Max 40 Mixing

Figure 4: OOMOO 30 Mixing

Product Name:	Mixing Viscosity
Mold Max 40	45000 cps
OOMOO 30	4250 cps
Vytaflex 60	2000 cps

Mixing Viscosity Winner:

OOMOO 30
Vytaflex 60
Mold Max 40

What is a Shelf Life?
A shelf life is an unused product in a container that has been opened and exposed to the ambient moisture in the air.

For polyurethane rubber, from Smooth-on.com states, “Unused Part A product exposed to humidity will begin to turn from liquid to solid in as little in a few hours. Part A exposed to relatively low levels of humidity which will last two to three months in the container before showing signs of moisture contamination”.

For silicone rubber, Smooth-on.com states, “Properly stored at room temperature (73°F/ 23°C), silicone rubber will have a shelf life of 6 months from date of manufacture”.

Shelf Life Winner:

Silicone rubber( Mold Max 40 and OOMOO 30)
Polyurethane rubber( Vytaflex 60)

Cost:
Here we will look at the cost of the 1 gallon unit and the trial size. For our group, we did not need and use a lot of rubber, so we went with 2 trial size of OOMOO 30 to mold the body and the leg of the Hexapod.

Product Name:	1 Gallon Unit	Trial Size
Mold Max 40	$96.54	$25.47
OOMOO 30	$153.03	$25.47
Vytaflex 60	$110.17	$25.96

Cost for Trial Size Winner:

Mold Max 40 and OOMOO 30
Vytaflex 60

Cost for 1 Gallon Unit Winner:

Mold Max 40
Vytaflex 60
OOMOO 30

Conclusion:
Overall, I think the OOMOO 30 is the best rubber to buy because of the trail size cost. Also the shelf life is so much better and last longer than the polyurethane rubber and it does not require vacuum degassing when mixing. Plus the durability is pretty good. I recommend when purchasing molding material, remember look for the durability, mixed viscosity, shelf life and cost.

References:

http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html

http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1136/index.html

http://www.smooth-on.com/Urethane-Rubber-an/c6_1117_1142/index.html

http://www.smooth-on.com/faq_display.php?faq_id=99

http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html?catdepth=1

http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1136/index.html?catdepth=1

http://www.smooth-on.com/Urethane-Rubber-an/c6_1117_1142/index.html?catdepth=1

How to perform a Stress Test

May 7, 2014/in Communites, Hexapod, Hexapod Generation #2, Members and Communities/by arxterra

By Vinh Kim, 3D Modeling and Manufacturing

Introduction:
Here I will show you how to perform a Stress test using Solidworks and SimulationXpress Study for the Hexapod leg and bracket design to determine its maximum stress level.

Leg Stress Testing:

Figure 1

First, open Solidworks and open the leg design the user wants to test.

Figure 2

Click on “Evaluate” and next on the top right click on “SimulationXpress Analysis Wizard”

Figure 3

Now, on the box on the left side using the mouse, right click, and click on the “Apply/Edit Material”

Figure 4 a

Figure 4 b

A Material box will show up. Now pick any material that the user wants to test. I picked 6061 Alloy because SolidWorks already had the value in auto set so simply click apply and close.

Figure 5

Now, right click on fixtures than click on fixed geometry.

Figure 6

The Fixture box will show up. As shown, here I clicked on the four holes than a green arrow will pop up and that means that this will be the precise location where the user chose. When done, just click on the green check mark on the left side.

Figure 7

Now, right click on the External Loads and click on the Force and apply the force.

Figure 8

Figure 9

When the leg is sweeping, Figure 8 shows the wrong way of applying the force at the bottom on the leg and Figure 9 shows the right way of applying the force at the bottom from the side.

Figure 10

Now in the Force box, I set the force to 500 N and click on the green click mark

Figure 11

Figure 12

When finish setting the force number, in the left side the user will see a box (similar to Figure 11) than click next three times and click Run Simulation (Figure 12)

Here is the video of the leg sweeping: http://youtu.be/z0AmgpNLJIg

Figure 13

Click on the Factor of Safety (-Max von Mises Stress-) and the user will see a lot of red that mean that the force of 500 N is pretty high, so I am going to lower the force and rerun the study until we see all blue and that will be are maximum force.

Figure 14

At 102 N, we see a little red.

Figure 15

At 101 N, we see no more red, so this is our maximum force for this leg design.

Bracket Stress Testing:

Figure 16

Figure 17

Here I am using 6061 Alloy again and applying fixtures in the bottom (green arrow) and force of 30 N on the top (purple arrow).

Figure 18

On the left hand side click next three times and run simulation.

Here is a video of the bracket bending: http://youtu.be/RigGvNsRHT4

Figure 19

This is at 30 N and you can see all the red, which is not good because it will break. Rerun the test again now lowering the force down.

Figure 20

Here we find out that the maximum of this bracket is 6 N.

Conclusion:
It is recommend to manufacturer that when designing any types of robotic model. They should always consider of using Solidworks SimulationXpress Study to check their design and use different material to run simulation to test their design if its strong enough to handle all those pressures and burdens that will be placed on the robot.

Voltage Regulator

May 7, 2014/in Communites, Hexapod, Hexapod Generation #2, Members and Communities/by arxterra

By Tien Dang

Problem Statement
Base on current test and calculations from discharge rate of current (available at https://www.arxterra.com/current-draw), we noticed that the battery provided 7.4V and 5000mAh, while each servo only required 6V (maximum) and 450mAh (with full load) to work. Essentially, the servos could burn without something to step down the voltage.

Solution
To prevent an overload voltage and current, we chose to use a voltage/current step-down regulator to limit the current as well as the voltage that going into ADK board and the servos.

Figure 1: Voltage step down regulator

Figure 2: Equivalent Circuit

With this particular voltage step down regulator, we can limit the voltage and current that flows through the servos and ADK board.

Set up process
This Voltage regulator has a DC input and a DC output. All we need to do is connect the source to the input and use a voltage meter to measure the output voltage. We can adjust the voltage by turning the Adjust Button using a flat screwdriver.

Figure 3: Adjust button and flathead screwdriver.

After adjusting the voltage to a prefer level (in our case we adjusted to 6V), the Voltage regulator is ready to use. All we need to do is connect the output into an outlet and ready to apply power into applications.

Android Phone Complications with Arxterra Robot Application

May 7, 2014/in Communites, Hexapod, Hexapod Generation #2, Members and Communities/by arxterra

By Tien Dang

Introduction
ArxRobot is an application for Android phone that allows users to control their robots wirelessly through Internet command (panel website: http://cp.arxterra.com/#). For this project, we will be using this application to control the Hexapod for walking sequence and traveling over objects on the testing field.

Trouble download and connection
In order to download the App from Play Store into the phone, we need an Android phone with version of Android 1.6 or higher. Although, there are other phones that allow you to download the App and use it but there are few of them (?) can’t recognize the USB from your phone and the Microcontroller ‘s USB ( a test had been done using a Samsung galaxy SII (SGH-R760), Samsung galaxy S4 (SGH-M919) , Samsung galaxy S3 (SGH-T989) and found out that these phones are not recognized by the USB from the ADK board, due to the phones IOIO-OTG were not supported). To check that if the phones are compatible with IOIO-OTG or not, the user can visit at https://github.com/ytai/ioio/wiki/Supported-Devices. There are certain cases that the user phone is compatible with the IOIO-OTG, but is not compatible with the App. (I have tested HTC WildFire S)

Figure 1: Compatibility of HTC Wildfire S from https://github.com/ytai/ioio/wiki/Supported-Devices

Figure 2: Compatibility of HTC Wildfire S when downloading the App.

Solution
If your phone is not compatible with the ArxRobot App, we have no choice besides using another phone. Incase if your phone is not compatible with the IOIO-OTG USB. All we need to do is unlocking the bootloader from your phone and install the USB driver into it.

What is a Booloader?

Bootloader is a piece of code that runs before any operating system is running. Bootloader is used to boot other operating system and usually each operating system has a specific set of Bootloader for it. For the new phones such as Samsung Galaxy S.x, bootloader is actually locked. The guide that shows how to unlock Bootloader can be find at http://www.addictivetips.com/mobile/what-is-bootloader-and-how-to-unlock-bootloader-on-android-phones-complete-guide .

Advantages and disadvantages of Bootloader

Figure 3: Screen shot while unlocking bootloader

If the user decided to unlock the Bootloader for their phone, the phone will show the picture as Fig.3 demonstrated. The user phone’s warranty will be voided, and could cause some applications on their phone to not work properly. But on the other hand, they will be able to install and custom any drivers for their phone as desired. For an Android phone version of 4.3.x and up, the developer team has not been able to unlock the bootloader at this point of time yet. So there is no way we can control the Microcontroller board via Internet if we own an Android with version 4.3.x or beyond this version.

3D Mold Making

May 6, 2014/in Communites, Members and Communities, Spiderbot, Spiderbot Generation #2/by arxterra

By Simon Abatay – 3D Molding & Manufacturing

Video By Kristine Abatay

After receiving the 3D-printed parts from manufacturing manager, Ali, it came time to create the mold for casting. The purpose of molding and casting the part is to eliminate the amount of time it would potentially take to print several pieces. The downfall is that the method can become costly if not done properly the first time. Molding and casting also allows projects to have replacement parts if any of the parts break or get damaged.

(Note: this method is only useful if you plan on mass producing a part or plan on having back up parts. If you only need 1 or 2 pieces, it is recommended to use the 3-D printer.)

This post explains the method of mold making that was used to make components for Spiderbot.

Materials:

Oomoo 30
Plastic tools to dispose of.
Oil Based Clay
Hot glue and glue gun
Polycarbonate sheets or lexan sheets
Mold release spray for silicone and rubber
Clear plastic cups for mixing
Aluminum foil

Process:

Lay the aluminum foil down so you have can protect your work surface.
Cut the plastic sheets to size. (This size is much larger than the piece you are trying to mold.)
Using the glue and glue gun, build a box out of the plastic sheets around the part.
Using the oil based clay. Fill half of the box with the clay and submerge half of the piece in the clay.

Make positive keys in the clay. (These keys will help with aligning the mold when you are ready to cast.)
Pour the 2 parts into two different cups while making sure they are of equal amounts as the instructions indicate to mix them at a 1:1 ratio.
After making sure the mixture of the two parts is a uniform purple tint, pour it into the box submerging the exposed half of the part.
Let cure for 6 hours.
After curing, flip the box over and remove all clay.

10. Build a clay cylinder and place it on the highest point of the newly exposed part. This will be the spout for the plastic resin to pour into.

11. Spray down the box and newly exposed part with the mold release spray. (This spray will prevent the just cured half of the mold from sticking to the new half.)

12. Repeat steps 6 through 8.

13. After the final half of the mold is cured, remove the mold from the box.

14. Pull the molds apart and remove the 3-D printed piece.

15. You may now begin casting your part!

This video was used as a reference to make molds and was provided originally by the supplier.

https://www.youtube.com/watch?v=FQ1A7ZjTsx8

This second video shows the process above being applied to the creation of a tibia piece for Spiderbot:

http://youtu.be/OL3B0jtyZZw

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