The development of a frictionless pneumatic actuator: a mechatronic step towards safe human-robot interaction

In the quest for a robot arm, which is capable of mechanical interaction with humans, biology can be a good source of inspiration. After all, the human arm is the best example of such a manipulator. A comparison between the human movement apparatus and an industrial robot arm reveals the most important criteria: the actuators of a human-like robot arm should have high compliance, no dry friction and low weight. The proposed solution combines air bearing technology and pneumatics to obtain a compact system with high performance. A thorough identification of the plant enables the design of a specialized controller which compensates for the plant nonlinearities like the dead zone of the pneumatic proportional valves. The prototype of the force controlled, frictionless pneumatic actuator (FPA) has a bandwidth of about 50 Hz and, compared to traditional robot drives, an extremely high compliance (or low stiffness) even for disturbances above the controller bandwidth.