Vex Walker

New Innovation First youtube vid!!

This thing is awesome B-)

My next goal is to have the robot stand on 1 foot. Once I get that position I think I will be able to take a step. I will have to adjust the head. I’m not getting the Center of Gravity positioned correctly to balance on one foot. Currently I have 2" standoffs on the neck. I’ll be putting longer standoffs there until I get a stable position.

The camera’s are there for weight right now. One of them will stay, the other one will be replaced by the receiver. I also want to put a light on the head and eventually if it ever walks I think a sonic sensor would be cool.

Any input or ideas are welcome and appreciated. The current code is posted at If anyone wants to download it and give me some input please don’t hesitate. It’s written in EasyC Pro.

I like the images you also posted up there. Looks like a cool project.

Have you checked out these?
(just google 'em )
Parallax Penguin
Biped BRAT
Biped Scout

Futuba Humanoid
Kondo Humanoid
Alpha Rex (LEGO NXT)
Robotis Humanoid

might give some inspiration and ideas, though im sure an innovation first enginner wouldnt need 'em :wink:

keep up the good work

oh and technically, welcome to vex forum :smiley:

wow. this looks like a very challenging project. good luck on finishing it, and i can’t wait to see what becomes of it.

I looked at a bunch of the Japanese Humanoid Robots prior to starting. What inspired this project was the Vexplorer Challenge with Grant Imahara. There was an entry that attempted a walker with a pendulum. The Humanoid Robots move the CG with the servos in the feet. The pendulum design I thought was a very elegant and more natural way of moving the CG. I wish I knew that contestants name, he had a great idea.

If this design doesn’t work I will have to add servos to the feet and move the CG the way all the other Humanoid Robots do. If you notice I have different size rubber pads on the bottom of the feet. I hope this will allow the Robot to lean over more.

depends surface really, on hardwood/laminate yes but on carpet you want a larger quantity of smaller ones so its kinda blends in -> like velcro (IMHO)
factors being fluffiness and thickness of the carpet

100% agreed with pacoliketaco

After increasing the head stand offs to 4" I was not able to lift a foot off the ground. I was very close though. The supporting legs knee joint is not able to support the weight of the robot. The torque being generated is causing the head to cross the centerline of the ankle joint and allowing the robot to fall.

I have several options at this point: I can double up the elastic bands on the back of the legs to help support the weight. I can also add additional weight to the head. I can strengthen the joints (keep adding metal until it stops flexing).

One thing I have to do is lower the head. With the 4" standoffs the head is almost impossible to control now, even after I replaced the chain and sprocket with gears.

Anybody have any other ideas?

Just wondering, is it me or do the Vex servos have a much rougher resolution then other servos. I was working with a lynxmotion a few days ago and that thing was killer smooth. If so I could see the rough motions of the vex servos being a problem (along with the play in vex gears, shafts, and chain) while trying to get this thing to work. I will say it looks killer awesome with the 2 vexplorer cameras on top. :slight_smile:

Also, are you saying that the torque created is making the robot fall because its back driving other servos?

The SW is moving each servo in sequence a little bit at a time. It’s pretty smooth, but not perfect.

The servos are not being back driven, the supporting knee joint is twisting and allowing the CG to move back toward the centerline which is causing the instability. Doubling up on the elastic bands I hope will solve both issues.

I wonder if adding some more weight lower on the robot would also help. Like heaver feet. Also I wondering if because you are moving things slowly that affects it. What I mean is try and walk like you normally would but slowly it’s a lot harder to keep balanced.

Looks like it would be nice to have something to shift weight from one side to the other on the body as well as the motion of the head so that you can adjust the center of gravity further. How about adding a rack and pinion with a slider the width of the body that is weighted in the middle? it would let you shift weight to either leg, and then back to the center as needed to, canceling out a bit of the robot’s movement-resisting inertia.

Having big heavy feet is how the Humanoid Robots get it done. I could do that but then it would not be near as fun.

The robot that inspired this project had a pendulum very low and between the legs but it could not adequately move the CG.

Newton’s First Law of Motion definately applies if this robot ever walks. A very slow tedious motion is not what I want this robot to do and it wold not be a very efficient walker. We have several of the Humanoid Robots here and I want the Vex Walker to sprint by them.

The rack and pinion idea is interesting. I could run the rack off the gear in front. That’s an excellent idea as long as I can keep the weight down. I will definately consider that.

Keep in mind I only have a single motor port left.

yea ive used tons of GWS servo’s and they’re all smooth, i find the vex ones are really rough and jerk around