Pneumatic Systems

With robotics, most pneumatic systems don't have much path control of the action from the controller with the exception of having exhaust flow control for smooth motion. Acceleration is a function of pressure and flow, or force, geometry and inertia. Speed controls is limited by flow of the pneumatic valve and exhaust restriction. Deceleration is usually accomplished with hydraulic cushions. This earned pneumatic robots the name "bang-bang robots". Many of the early robots that were hydraulic worked in the same manner. They moved from one hard stop to another.

There were some attempts at building pneumatic servo robots, they never really were accepted. Some time ago, one robot manufacturer displayed a fully pneumatic robot at a show, and I recall them working all night to get it working. (I often worked all night at shows) It had Motorola 68000 microprocessors on each axis to control it - always adding and removing air from the actuators to maintain a position. (Air is very expensive) Air is a compressible fluid and doesn't lend itself well to robot servo applications.

I have used pneumatic servo actuators very successfully on other applications. There were pneumatic servo actuators available several years ago the took a voltage command signal of 0 to 10 volts and responded like a cylinder to a corresponding position and maintained it. A one inch stroke actuator extended 1/2 an inch when it received a 5 volt command. At GRI we used them successfully in a dual component metering system for paint. They didn't require much power, so they could be made explosion proof using intrinsically safe barriers. The also didn't use a lot of air to get the job done. I'll add more to this page as I remember things of interest.

Some examples later. (Still under construction)

 

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