Impedance control for a pneumatic robot-based around pole-placement, joint space controllers

Traditionally the control of pneumatic actuators has been limited to movement between pre-set stops or switches. Modern pneumatic systems exhibit great power to weight ratio, are backdrivable and can be precision controlled. As such these actuators offer great advantages over direct drive electric motors for robotic devices. Increasingly robots are required to interact directly with humans requiring control of not only the robot position but also taking into account the applied forces. Robotic physiotherapy is one such application. This paper describes the implementation of a force and position control strategy, termed impedance control, on a pneumatic robot designed to implement robotic physiotherapy. The controller is shown to work appropriately over a range of conditions. The performance achieved is limited by the quality of force measurement in multiple axes. (C) 2004 Elsevier Ltd. All rights reserved.