Digital Motion Control and Profile Planning for Pneumatic Servos

This paper considers the use of “profile-planning” to (i) improve/optimize certain performance characteristics of pneumatic servos and (ii) simplify procedures associated with their tuning. The underlying approach is to preplan the transient behavior of the system thereby generating an appropriate command profile. To assist in applying this technique to the control of air-powered servo-systems, the paper highlights important knowledge derived previously with regard to the stability and operating characteristics of pneumatic drives. Preliminary rules for conducting such planning are then proposed with reference to a series of experimental observations. This approach can be employed to significantly reduce or prevent overshoot and instability of servo-driven pneumatic actuators (cylinders in particular) which are difficult to overcome by using conventional methods. At the same time, increased operating speeds and improved positioning can be attained. The proposed control scheme has been implemented in prototype form through using a proprietary programmable motion controller which incorporates software mechanism for generating gearbox and cam-like motion profiles.