Variable physical damping actuators (VPDAs): Facilitating the control and improving the performance of compliant actuation systems

As recent application domains emerge requiring the employment of robots within unstructured environments, new demands arise requiring more versatile systems which can cope with unpredictable interactions. Recently, compliance has been identified as one of the key features which enables the safe operation of robots interacting with humans and environment. Despite the certain merits gained with the introduction of compliance, this property introduces also some drawbacks as the reduction of the bandwidth achievable in the controlled system and the introduction of oscillatory dynamics which dramatically reduce the stability and accuracy of the system. A solution which can be used to overcome such issues consists in the incorporation of physical damping within the actuator mechatronics. Motivated by the above, this work presents the evolution of such actuators from purely compliant to more complex and performing systems which incorporate variable physical damping as added feature for the development of robust, safe and still well performing robots. The mechatronics of the developed units are analysed. The compact compliant actuator (CompAct™) with variable physical damping is evaluated with experimental trials performed using a prototype unit.