Pedmatic

Dr. C. S. Soh the famous LEGO pneumatic engine enthuesiast threw down a friendly challenge that we need a pneumatic biped made from small pneumatic pistons. It took up the challenge and met the challenge after less that four hours of building time.

Pedmatic uses pistons in four places: left leg forward/backward, left leg right/left, right leg forward/backward, and right leg left/right. Small pistons act quickly, but produce much less force than larger pistons. I combined two pistons per switch so the pistons would be able to flip the pneumatic switches. I also chose switches that flip easily. My switches are highly used, so some of them flip very easily.

The combination of piston and switch are a fundamental part of Pedmatic's design. It can be a lot of work drawing out a LEGO pneumatic circuit using pistons, switches, and the linkages that hook them together. Here is an example of a large piston controlling a switch.

This picture introduces a symbolic representation of the piston/switch combination to make it easier to draw out Pedmatic's pneumatic circuit.

Pedmatic is an example of a pneumatic sequencer, a circuit that changes piston states (expand vs. contract) in a repeated pattern.

Pedmatic Sequence

Left Leg	Right Leg
Forward/Weight Bearing	Backward/Up
Backward/Weight Bearing	Forward/Up
Backward/Up	Forward/Weight Bearing
Forward/Up	Backward/Weight Bearing

You can see Pedmatic go through this sequence in this movie

The left and right hips are hooked up to do the opposite of each other, as are the right and left ankles. There are four switches in the circuit. Each switch is responsible for moving to the next state in the sequence. Pedmatic Images