Low-cost, high performance servo-pneumatic manipulators with sensor feedback

New types of manipulators featuring both low cost and flexibility are required to expand the spectrum of applications in factory automation for assembly purposes. A low-cost manipulator which uses pneumatic cylinders as the actuators is described. The cylinders do not require any gearboxes and are fitted with incremental encoders for continuous position monitoring. Continuous positioning of the manipulator axes is achieved through proportional pneumatic valves driven by a hierarchical control structure. This distributed structure also simplifies the integration of the sensors required for each particular application. A machine vision system based on the use of fast digital signal processors was developed, providing additional sensory feedback. To overcome the problems associated with the highly nonlinear nature of the system composed by the proportional valves and the pneumatic cylinders, both variable structure control algorithms and proportional-integral-derivative algorithms are used to achieve an optimal response