ATRIAS 2.1 Handbook/Printable version

ATRIAS 2.1 Handbook

The current, editable version of this book is available in Wikibooks, the open-content textbooks collection, at
https://en.wikibooks.org/wiki/ATRIAS_2.1_Handbook

Permission is granted to copy, distribute, and/or modify this document under the terms of the Creative Commons Attribution-ShareAlike 3.0 License.

How to use this WikiBook

Intent of this WikiBook

• Store all relevant info for how to build, use, maintain and generally anything useful for the ATRIAS 2.1 robot
• Ease of adding the above info by any and all collaborators of the ATRIAS 2.1 robot system
• The page will evolve as people add content and learn how to better use and maintain their ATRIAS 2.1 robot platforms

• When you learn something useful about the robot (for example a good spring constant that would be useful for a particular walking gait in a certain environment) you add it to the correct page. Thus the information is not lost when you graduate or move on to other tasks.

Licensing your uploaded pictures

It is very important that you apply the correct licensing to your pictures hosted on wikimedia commons, they will delete your pictures if you mess this up. I've (jesse grimes) used the following and seems appropriate. Copy and past this into your licensing attribute.

{{Attribution|year=2013|month=05|day=24}}

link filled pages - marked as SPAM

It is a current issue that the pages that house useful links to products, manufactures and suppliers for the robot get tagged as spam by the WikiBooks overlords. We'll find a solution to this. It might just be that we have to prove ourselves as worthy contributors and that these link filled pages are not spam.

Suppliers and Manufacturers

This page lists suppliers that are used or considered for use on the robots built in this lab. These are places that we've used in the past for various aspects of the robots creation and maintenance. Note that some of these places (namely the machine and anodize shops) are local to Oregon State University in Corvallis, Oregon and may not be useful for you folks at UofM and CMU. The intent is that you can search here first for where we got an item (say a certain sensor).

Add to these lists as you find useful hardware or manufactures that may be useful in in upgrading our hardware. Also list places that we should not work with. This can save us some serious time and effort later on. Remember that the lab will be here a long time working with these, and future, robots. And as undergrads and grad students we will come and go. WE WANT OUR INFORMATION LEARNED WHILE WORKING IN THESE LABS TO BE PRESERVED FOR THE BENEFIT OF THE RESEARCH!!!

1. Machine Shops Places where we have machined parts made for our robots
2. Anodizing Shops Places where we have our machined parts colored
3. Water Jetting Shops Places where we can get water jetting jobs done
4. Cables and Rope Cable and rope for cable drives and such
5. Composites Shops Places where we can get composite work done
6. Electric Motors
7. Harmonic Drives Compact, geared transmissions
8. Bearings Large diameter, thin section bearings among others
9. Sensors High resolution absolute and incremental encoders
10. Slip Rings Continuous rotation electrical contacts
11. Raised Floor Tiles used in the experimental room at OSU.
12. PCB Manufacturing Where we get our custom PCB's made
13. General Suppliers
14. Other Useful Companies Things that just flat out come in handy

Disclaimer

In no way to we endorse or promote the use of these companies and vendors over others. This is a simple list of options we have explored and our experience with them. This page is to be used among the Oregon State University Dynamic Robotics Lab and it's collaborative labs at the University of Michigan and Carnegie Mellon Universities Robotics Institute (as of May 2013). Others are welcome to see what our experience has taught us but keep in mind we are not promoting or advertising this information.

General Information/Cost of Transport Definition

NOTE:
At some point the info below should be distilled down to useful info and presented in a wikipedia/textbook/encyclopedia format. This email chain was provided to me [Jesse Grimes] by Jonathan Hurst concerning cost of transport

Jonathan,

I misspoke on the phone. If you are at 0.5 A and 50 V, then you are using 25 Watts. Let's say you are moving at 1 m/s and the ATRIAS Monopod weighs in at 20 Kg.

THEN....and you will like this.............

Mechanical Efficiency = 25*1/(g m distance) = 25 / (10*20*1) = 25/200 = 1/8 = 0.125

The number for a human walking is 0.05......and ATRIAS is hopping. Your robot may be a game changer!

Here are the numbers given by my simulation, with torso stabilization:

Step 50 completed at time t = 18.7972, Stride duration = 0.37769, Speed = 1.588, Stride length = 0.59976, cmt=1.028, cet=0.12047

ATRIAS is much closer to the net power, which allows negative power to be shunted to the battery, than to the efficiency estimate that looks at positive work and gives no credit for negative work.

Jessy

Jonathan,

I was confused about the difference between CMT and CET. The paper by Ruina, cited by Koushil below (see link) clarifies this. In my simulations, I had been focusing on CMT because that is all we can estimate for MABEL. For ATRIAS, it is easier to do the CET, from what I understand.

Jessy

Dear Prof. Grizzle,

Sorry, missed your mail. Prof. Geyer is specifically talking about CET, the specific cost of energetic transport. We have never measured this value for MABEL. We calculate only CMT, the specific cost of mechanical transport.

This paper [pdf] (refer pg. 2, column 2) mentions human CET = 0.2, and human CMT = 0.05.

MABEL min CMT = 0.1, and we are a factor of two away from that of humans in this regard.

Thank you,

koushil

NOTE: Said .PDF file was not attached to my email. -Jesse Grimes

Jessy,

Here is some COT data on humans and horses for different gaits.

For the human data, assuming a body weight of 70 kg gives a walking minimum of COT = 2, or if divided by gravity, CET = 0.2. For running that will be about twice as much.

For the horse data, the weight is about 140 kg, and 1ml_O2=20J, yielding the same values for minimum walking COT and CET as those for humans. However, horses reach the same minima in other gaits at higher speeds as well.

Hartmut

File:COT horses.jpg Cost of transport of horses at various speeds and gaits

File:COT human.jpg Cost of transport of humans compared to other various locomoting things

Technical Specifications/Solid Model Specifications

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Technical Specifications/Toe Cell

Measurements resulting from these cells should be accurate to within 5 Newtons.

Unit Letter	Sensitivity [N/bit]	Offset [N]
A	0.2883	1872.2
B	Example	Example

Servicing Information/Loctite Procedure

1. Clean the hole using the thread chaser.
2. Prime the hole and the screw to be used. LET DRY COMPLETELY OR THREADLOCKER WILL NOT SET!
3. Apply enough threadlocker to completely cover to the first 5-10 threads of the tip and 1 drop on the threads in the hole.
4. Torque screw to specifications. See Torque Specifications below.

Table of torque specifications to be used on ATRIAS 2.1. Use a torque wrench!

	Torque	Torque
Size	Dry	w/ Loctite
ENGLISH BOLTS
4-40	5.2 Inch LBS	4.42 Inch LBS
6-32	9.6 Inch LBS	8.16 Inch LBS
8-32	19.8 Inch LBS	16.83 Inch LBS
10-24	22.8 Inch LBS	19.38 Inch LBS
1/4-20	75.2 Inch LBS	63.92 Inch LBS
METRIC BOLTS
M6	84.0 Inch LBS	71.40 Inch LBS
M8	192.0 Inch LBS	163.20 Inch LBS