Let's Make Robots!

robotizing a mechanical walking frame


I'm looking for a device that records my walking motions digitally, and can control servos to imitate my walking forces, balance etc..

You see, I've got this 'mechanical spring-loaded bipedal walking frame' that assists in the walking motion (google search "spring walker" to understand what I mean), and what I want to do with it is turn it into a autonomous walking robot.

I've been thinking that if I attached servos and a computer (brain) to it to record my walking motions, then I can get it to walk on its own...without me strapped into it, that is. But I need advice on what kind of servos (make, model) to use that's powerful enough to move the walking frame. And, also what kind of device or program would allow me to record and save my actions in such a manner that I don't have to keep sorting out the data to tell the computer "when this, do this, etc (if p then q)? Presumably there's a device out there that would do all this for me, and not too expensive? 

I figured I could utilize the info gained by IR sensors taped to the frame to help with the decision making of what king of motion to do at a given situation (i.e. that it doesn't try to clime a hill when walking on the road, or walking when it's suppost to clime, etc.) Can you advise on what IR sensors are good for this particular job?

I don't know the scale of this kind of project, or if it's too difficult to do without expert roboticists on hand, but I'd like to try anyway.

Thanks very much, hope you guys can help.

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This sounds like a pretty involved project. There's a biped robot website at Xrobots that shows a number of simple, cheap as possible, robots that could simulate walking, not sure about jumping. The early designs (Android 7 and under) use surplus windshield wiper motors to have enough torque to move. These you'd need to apply your own drivers to, as well as developing the program for the micros needed.

About recording your motions, you could either rig a "leg jig" or use a webcam. The leg jig would have potentiometers or some other displacement reading device at each joint, then the outputs could be sent to a micro, that could stream the data into a PC. The webcam(s) could record data from special color markers placed at joints, to record data in a simlar manner. I believe that some of the bipeds, like Asimo, have been based on pre-recorded data like you are considering, but they also rely on sensor data to use control algorithms (like PID) to "adjust" these pre-recorded motions to the current floor conditions.

At any rate, quite a project. I don't know of any premade system that will help record or play back motion in this manner. Oh, regarding sensors, might be better to go the sonar route, for greater distance. It's ok for a robot that is breadbox sized to see only 30" ( 80 cm) to 60" (160 cm) in front with IR, but a people sized robot would benefit with a little more warning.

Hey thanks for the advice! I’ve been looking on the internet for info on IR and Sonar ranges, specs etc., in order to compare them. Have you got any info you could share regarding these (and maybe prices if you know of sellers)? Thanks very much. J

Check the thread here :


Sharp IR sensors run from $9 to $15 from various vendors.

The Maxbotix sonars as well as a few of the Devantechs are around $25, the Senscomps around $50 I think. 

Oh yeah, they’re a variation on the “bionic boot”.

Trouble is I’d have to construct legs and hips with joints & everything if I wana get them to walk on their own!

I figured copying my walking would be a better way to teach a robot to walk than having to go through artificial codes. Can a PID be tuned to take into account my walking motion and use that as its user-defined parameter? just wondering what's the cheapest, fastest, best way?

Well, yes but. Think about it the other way: How would YOU balance. If your robot is copying you, walking along beside you or whatever and you miss a step or trip on the sidewalk. You make moves to correct your own balance, which will probably CAUSE your robot to fall over, because it "thinks" it should be copying you.

Your respective environmanets would need to be identical. If you walk on a stone, with your right foot, your left foot starts to rise sooner than expected. If there is no stone under the robot's right foot, it'll try to lift the left too soon and fall over.

I suppose you might consider an high level of abstraction, where your movement translates to "he's walking" or "he's running" or "he's turning". Then you could program the robot to "walk" or "run" or "turn" as applicable.

...but then you're into artificial codes...

Yeah, balance is gonna be a major problem to overcome, especially on two legs. I’m not too keen on using big feet to produce better stability, but I was thinking of using some sort of gyro to enable 'centre of gravity' finding with a built-in sensor…but where can I get the right gyro-sensor unit?


For a video of the spring walker in action see: http://www.springwalker.com/SpringWalker.mpg


What I mean is if you build in ANY sort of PID or sense-and-react system the result will not be a copy of your movements.
you should post a video of it in action - its hard to tell how it all works from just a static picture.  Then if you could get BOA to try it ... that way we can see how "simple" it really is - (should make an awesome video too) ;DD