Monday, August 30, 2004

First Part


The first part is made

Stuart made the first of many parts this week. It's so great to see it join us in the physical world.

Some Feedback on the New Look


A tribute to Brian Dean's Servo Mojo Eval Board
Keith Rowell Design

Excellent! Careful ... that's tempting to put up on my web page :-)
BTW, I like your new "head" design a lot better than the original.
Looks clean and modern. You ought to turn this into a product once
you get it fab'd. A kit would be great. I know I'd buy one as long
as it was affordable.
Great work!
-Brian


Hey Keith!

Looks like you are making great progress! Are you machining the parts yourself or are you using a fab shop? I have been thinking about getting a table top mill to do things like that, but it's hard to justify the cost. The lateral joints at the knees are interesting. Are there also lateral joints at the hips? About the batteries in the head. You are correct - the high center of gravity requires less shift left or right to balance the robot over a foot. I haven't done any formal calculations, but I think that the higher center of gravity would also improve the efficiency of the walk. A biped with a low center of gravity will need to "waddle" back and forth more to shift the CG over a foot. The overall result is that the body of the robot travels in a zig-zag as it walks forward. With a higher CG, the robot waddles less and the body travels in more of a straight line. The distance between the hips will have a similar effect - the farther apart the legs are for a given height, the more the robot will have to waddle to shift the CG over a foot.

Please keep me informed of your progress!

Later,

Mike

Thursday, August 19, 2004

A New Look

Hey, I like the new 'head' design. Sort of looks like a mechanical fist walking around to find something to punch! Bill Hotch


This shows the current new head design, and what it would look like if the bot were anodized in gold or yellow.

Keith Rowell Design

In the intrest of avoiding any conflicts with the Lucas Films guys in the future, I've been advised to avoid derivitive design based on the Star Wars AT-ST (though I love that design so much).
So all future work will be original in style, (all comments and critiques welcome). Hence the funky head shown in this week's update. Please respond with your first impressions. I will incorporate all ideas possible. Don't get stuck on this first one, The sky's the limit until it comes time put in the electronics and start testing. Lets hear your ideas...

The project has had many leaps forward this week.

First of all, IronCAD has chosen to sponsor the bot. So we'll be sporting the IronCad logo, on the bot it'self at all events...

The first parts have been made and they fit perfectly! I place the bearings into the lower ankle rod myself today, and they fit like a gove. You can spin this thing on the bearing and it runs forever, zero friction! I like it. Thanks to Stuart Rolf for his formidible experience, ability and generosity to provide the machine work. I can see 2:1, 4:1, ad infinitim scale versions of this in the future. Watch out world!

Draftech is expected to print out a copy of the new head shape on their 3D STL machine tomorrow, in abs plastic. Asuming I can get the file ready.

Another area I would like ideas on is weapons. I plan to enter it in the first (American) Robo-One competition, http://www.robo-one.com/ which will probably happen next year. And a major requirement for competetiveness is the ability to get up when knocked over, and some kind of ability to knock over opponents. So get your viking battle magic thinking helmets on and offer some suggestions. I'll try and summarize the rules for that competetion here soon.

Keith Rowell

It laks some of the angular agressiveness of the original, and it's not prickling with guns.

Keith Rowell Design

Tuesday, August 17, 2004

IronCad Sponsors the Project

I designed the whole project in IronCad so far. I really like the interface.



Looks like we can go ahead with the sponsorship

Keith Rowell Design

Hello Keith,

Looks like we can go ahead with the sponsorship. Our VP of Marketing is asking for "use of the IronCAD model files and images, promotion of the IronCAD name on any website or write ups and placement of IronCAD sticker on machine".


Best regards,
Kevin
IronCAD -
700 Galleria Parkway Suite 330Atlanta, GA 30339
Toll-free: 800-339-7304
web: http://www.ironcad.com

From: Shaun
Sent: Monday, August 16, 2004 5:39 PM
To: Kevin
Subject: RE: Knewt walker project

Kevin;

This sponsorship should be fun. Please ask for the following marketing promotional benefits (use of models and images, promotion of IC name on any website or write ups and placement of IC sticker on machine). If they go for this lets do it.


From: Keith Rowell
Sent: Monday, August 16, 2004 4:15 PM
To: Kevin
FW: Knewt walker project

Thanks Kevin for the the menu advice,
The "TBC" file problem happened only once before to me, many years ago, I'm very gratefull for your help.

We're getting ready to start cutting parts for this robot now. All the motors and batteries and electronics have been aquired and tested. I plan to enter it in the first (American) Robo-One competition, http://www.robo-one.com/ which will probably happen next year. I plan to use it for trade show promotions, other robot events, etc in the coming couple of years. It's completion date is scheduled for next spring.

The following email is my last update to the group that's involved in the build team. I have electronics types, mechanical engineering types and machinists contributing. I've been very lucky on this project in regards to attracting high quality advisors and I think it's mostly because of the "coolness" factor.

I approached you once before about the possibility of sponsorship in return for some some marketing worthy models. I'm hopefull that this project qualifies. Can you pass this message around to anyone who might be able to make that happen? I can offer logo space on the bot, and do some promotion events as well.

Sincerely,

Keith Rowell



Monday, August 16, 2004

I recover from the crash, with an improved design


The head sits directly above the weight shift motor. The head plate and bearing attach to the neck plate. I can't wait to start cutting some parts. I'll start making drawings this week to make parts from. I have lots of screws and bearings and gears to show you Stuart. I want to get your advice on how to do some things.

Keith Rowell Design

Having started at the foot and worked my way up, we've now reached the head. Getting the neck support in around the motors was getting to be tiresome, but after 3 tries, I think this will work. I wanted all the wires to come through the neck but the simplicity of this "head turn motor" design convinced me to just bundle them from the back. All the electronics will go in the head. The back of the plastic toy head comes off and the servo motor driver board fits in nicely.

Keith Rowell Design

I went with 6 NMh 1.2V batteries instead of 2 3.6V Lithium simply because the size of the lithium were inconvenient. I have space on the bots back for the lithium if needed. but the hydride prism cells fit very well into the bot's belly. If this causes drastic weight shifting requirements, I may have to go back to the lithium, and put them maybe in the head even. Perhaps Micheal Smyth will comment. His bot has the batts in the head, I assume for that reason, higher center of gravity equals less weight shifting degrees... See MiniMechaDon
http://home.ctlnet.com/~minimechadon/minimechadon.htm

Keith Rowell Design

The weight shift motor has 16 degrees of travel. I expect to need less than 10deg.

Keith Rowell Design

The maximum turning angle for one foot is 10deg. combined with the other foot, that's 20deg of turn per step.

Keith Rowell Design

settled on a horizontal mount for the leg motor.

Keith Rowell Design


Keith Rowell Design

The foot lifting motor now has a gear for power transmission. This multiplies the torque 4 times to 60 oz.in. The pillowBlock takes the stress off the servo motor. I think this kind of beef is required because this is the only motor that sees the entire weight of the bot. Both pinion and ring gear are dark blue.

Keith Rowell Design

I recovered ok from the crash, with an improved design.

Keith Rowell Design

Does anyone have any ideas for how to minimise the wiring clutter? If we cut the parts from copper clad fiberglass circuit board, we could cut the conductor paths directly into the structure. Then only jumper points between moving parts would be required. How thick can this material be gotten?

Thanks in advance for any and all feedback/critiques.
I'm standing on the shoulders of giants.

Keith Rowell

Saturday, August 14, 2004

Bob Points Out the Competetion

Have you seen this new biped from Lynxmotion?
http://www.lynxmotion.com/Category.aspx?CategoryID=67

I guess our kit will be worth at least $600, but less than $1500. See also the KHR-1 http://www.sozbots.com/robo-one/

Monday, August 09, 2004

Possible Custom Acceleration

The Servo Mojo uses straight line acceleration and I had asked Brian if an
exponential ramp was possible.


Thanks very much Brian, we were satisfied with the ServoMojo in our preliminary tests. At this point, we have to get some hardware and motors mounted to do more serious testing. Thanks for the offer to make modifications. I'll let you know if we have any suggestions at that point.

We plan to make one copy in plastic, sort of a version 1.0, modify the design, then make a ver. 2.0 in aluminum. I'm still making configuration changes.
This image shows a more compact arrangement for the batteries and motors.

Keith Rowell


This image shows a more compact arrangement for the batteries and motors


I never heard back from you on whether or not you have found the acceleration and velocity values that produce the motion that you are looking for. Have you had success with that?
I'm greatly hoping ServoMojo is going to serve your needs. When you said you were making a Biped walker, I had no idea it was going to be so well engineered. I can't wait to see your finished project. Let me know if you require any firmware changes on your ServoMojo to
support any special requirements you might have. Code space is very tight, but if you need a certain functionality, perhaps I can accomodate your needs.

Best Regards,
-Brian
--
Brian Dean
http://www.bdmicro.com/

A Pretty Good First Pass, Then a Crash

Cool stuff. Where's the laser cannon? Bill Hotch


That thing is way cool, Keith! Brian Dean


Looks cool Keith. I can't wait for the 6 foot version!!! Clark Wimer



A complete mock up so far.
Keith Rowell Design

the batteries are yellow
the spring is green
the ball linkages are black
screws are grey
bearings are red
servo motors are blue

The file crashed after building it up to the avbove level. and I lost all that placement. I'll have to do that part over again. Basically, there's bearing at each end of the hip plat that the legs attach to, that's the pivot point at the top to correspond to the pivot point at the ankle. The ball rod (in black) is the third leg of the tripod to keep the bot's reference horizontal as transmitted through the foot.


That thing is way cool, Keith!

I never heard back from you on whether or not you have found the acceleration and velocity values that produce the motion that you are looking for. Have you had success with that?
I'm greatly hoping ServoMojo is going to serve your needs. When you said you were making a Biped walker, I had no idea it was going to be so well engineered. I can't wait to see your finished project. Let me know if you require any firmware changes on your ServoMojo to
support any special requirements you might have. Code space is very tight, but if you need a certain functionality, perhaps I can accomodate your needs.
Best Regards,
-Brian

Thanks very much Brian,
We were satisfied with the ServoMojo in our preliminary tests. At this point, we have to get some hardware and motors mounted to do more serious testing. Thanks for the offer to make modifications. I'll let you know if we have any suggestions at that point.

Side view showing motor placement.
Keith Rowell Design

This one shows the right leg attached to the body (hip) part...I'll try other orientation for the leg motor to keep it from hanging down so low. This orientation is used to avoid hitting the other motors. That space gets tight when the leg motor is horizontal.

Shows the hip motor linkage. It rotates the hip about the red bearing.
Keith Rowell Design

Monday, August 02, 2004

Entire Leg is Designed

Working from the ground up, parts are getting designed.


This image shows the leg bone connected to the Ankle bone, and the Ankle bone connected to the foot bone, and the ....
Keith Rowell Design

This image of the foot bracket shows a slot for the servo motor and the foot tendon ending in a gear that meshes with a pinion on the servo.