Comments on: Programmable spring actuator legs

By: ihavenobeer

ihavenobeer — Mon, 07 Sep 2009 17:01:10 +0000

kill it with fire!

By: Bill Bigge

Bill Bigge — Mon, 07 Sep 2009 13:21:38 +0000

General note – my prototype actuators are really weak and I could only afford to make four, hence the reason for two legs with two degrees of freedom – you can see in the video that I put a counterweight on the back of the bot to help with the weight. This isn’t a major issue, I just need better motors. The actuators are a bit over-sized as well but I should be able to engineer them to fit into something about the same size and power (and price) of some of the robot servos that are on the market.

You could easily extend this robot to create a hexapod with three degrees of freedom per leg – it would still walk when you pulled it, and you can extend the control system further so it could walk autonomously – I’m also working on embedding a small neural network in each actuator to reproduce some more biological CPG based behaviors.

And also, yes – with the addition of a balance sensor you could use them to make your own miniature version of big dog, but for a few hundred dollars.

By: Bill Bigge

Bill Bigge — Mon, 07 Sep 2009 13:05:16 +0000

Satiagraha:

The graph is actually the method of defining the spring damping behavior of the actuator – the X axis is the actuators angle (the axis name was clipped from the image) and the Y axis is force (for the red line) and damping (for the other two lines) you ‘draw’ the spring forces and damping forces with the mouse and download the configuration to the actuator, when it runs it reads its angle and looks up the force value for that angle, reads its velocity and adds in the damping, then applies that force to the output.

This lets you define arbitrary spring damping behaviors that vary across all angles. There are two sets of damping, one for each direction of motion, so you can make things that are highly damped but only in one direction, and only across certain angles.

By: deedubs

deedubs — Sun, 06 Sep 2009 13:49:07 +0000

I can see this as a awesome trailer for increasing the load of Boston Dynamics Big Dog

By: le'chef

le'chef — Sun, 06 Sep 2009 11:10:37 +0000

NightMareish zombie torso!
Why won’t you die?!?!

By: memals

memals — Sun, 06 Sep 2009 09:41:10 +0000

I can not help but imagine this with grey rubbery ‘seal’ skin as a toy.

By: 24601

24601 — Sun, 06 Sep 2009 04:40:24 +0000

it’s awesome! I’d love to make that into a zombie half-corpse on a noose and drag it around the neighborhood on Halloween!

By: DrNick

DrNick — Sun, 06 Sep 2009 01:36:48 +0000

I did some research on the locomotion in the cat. The stepping reflex is hardcoded in the neural networks in the spine of all mammals and works a lot like this robot. When one leg has reached its hind position, it is brought in front and the other leg is inhibited from lifting up in order to support the weight. This is a fantastic demonstration of this concept. Google «Central pattern generator»

By: monkeyslayer56

monkeyslayer56 — Sat, 05 Sep 2009 20:29:58 +0000

now if only u make it instead of spring like make it were it walks on it own.

By: Mic

Mic — Sat, 05 Sep 2009 19:10:54 +0000

Very impressive motion. Looks like dog got hit by a train, eh soggy?

By: Satiagraha

Satiagraha — Sat, 05 Sep 2009 18:55:18 +0000

It looks pretty cool, definitely a very organic feel to the motion.

Has anyone noticed that the graph in the “Programmable Spring Actuators” link is completely useless? What is it plotting??

By: Larry

Larry — Sat, 05 Sep 2009 18:44:05 +0000

awesome, the movement is very interesting.

By: Scott

Scott — Sat, 05 Sep 2009 18:19:50 +0000

@soggy pretzels, I was thinking dog with busted backbone, the robot looks pathetic like it needs to be put down.

By: Mark

Mark — Sat, 05 Sep 2009 16:57:26 +0000

I went to a talk the creator (Bill Bigge) did at the BuildBrighton hacker space. Its a research project for his PhD. The idea was to make something the home builder could afford. MIT have something like it but its massively expensive.

By: Drake

Drake — Sat, 05 Sep 2009 16:31:58 +0000

Soggy Pretzels –> The legs appear to only have 2 actuators on each of them. If more were used in a configuration closer to that of a mammal then it probably would have more stability. Also they could probably be setup with some sort of hardware/software neural network to make it run smoother.

I think it looks like a sea turtle being dragged. Though they typically use their underside as a fifth leg.