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This pneumatic power design could improve working robots. Yes, you would still need a motor to actuate each joint, but now you can put the motor anywhere. Pla

by lostdog 12y ago

This pneumatic power design could improve working robots. Yes, you would still need a motor to actuate each joint, but now you can put the motor anywhere. Placing the motor in the torso removes weight from the arms, which means you need less power to control the arms and the arms have less momentum, both of which greatly increase safety.

Animats 12y ago
True. You can also get rid of the motor entirely and just use proportional valves and compressed air. Festo's robots work that way. A common model of human and animal muscles is to treat them as two opposed springs, where the spring constant and neutral point are both adjustable. Mechanical systems for that have been built for research robots, but they're mechanical nightmares of cables, pulleys, and springs. Two opposed air cylinders, though, can directly implement a pair of adjustable springs. That's been done a few times on research robots. This gives you muscles of adjustable softness, just like humans. A running robot with spring-type energy recovery could potentially be done that way. (Humans recover about 60-70% of energy from one stride to another when running. Cheetahs, 90%.) Mechanical running machines with springs for energy recovery have been built. With fixed springs tuned for running, all they can do is run. To make soft air springs work, you need position and pressure feedback on everything, and small, fast servovalves. Fast servovalves tend to be very expensive. They also have to be near the cylinders for good position control - too much air line and there's no way you can make the system stiff when you want to. Of course, you need compressed air. Meanwhile, brushless DC motors have improved so much, and are so easy to control now, that the trend is away from pneumatics and hydraulics. Boston Dynamics' humanoid is all hydraulic (it's really a modified Big Dog), but Schaft's is all electric. Google now owns both, of course.

by lostdog 12y ago

Animats 12y ago

True. You can also get rid of the motor entirely and just use proportional valves and compressed air. Festo's robots work that way. A common model of human and animal muscles is to treat them as two opposed springs, where the spring constant and neutral point are both adjustable. Mechanical systems for that have been built for research robots, but they're mechanical nightmares of cables, pulleys, and springs. Two opposed air cylinders, though, can directly implement a pair of adjustable springs. That's been done a few times on research robots. This gives you muscles of adjustable softness, just like humans. A running robot with spring-type energy recovery could potentially be done that way. (Humans recover about 60-70% of energy from one stride to another when running. Cheetahs, 90%.) Mechanical running machines with springs for energy recovery have been built. With fixed springs tuned for running, all they can do is run. To make soft air springs work, you need position and pressure feedback on everything, and small, fast servovalves. Fast servovalves tend to be very expensive. They also have to be near the cylinders for good position control - too much air line and there's no way you can make the system stiff when you want to. Of course, you need compressed air. Meanwhile, brushless DC motors have improved so much, and are so easy to control now, that the trend is away from pneumatics and hydraulics. Boston Dynamics' humanoid is all hydraulic (it's really a modified Big Dog), but Schaft's is all electric. Google now owns both, of course.