High Performance Differential Elastic Actuator for Robotic Interaction Tasks

For complex robotic tasks (manipulation, locomotion, haptics, ...), the lack of knowledge of precise interaction models, the difficulties to precisely measure the task associated physical quantities (force, speed, ...) in real time and the non-collocation of sensors and transducers have negative effects on performance and stability of robots when using simple force or simple movement controllers. To cope with these issues, some researchers proposed a new approach named «interaction control» that refers to regulation of the robot’s dynamic behavior at its ports of interaction with the environment. Interaction control involves specifying a dynamic relationship between motion and force, and implementing a control law that attempts to minimize deviation from this relationship [1]. The implementation of machines able to precisely control interaction with its environment begins with the use of actuators specially designed for that purpose. To that effect, a new compact implementation design for high performance actuators that are especially adapted for integration in robotic mechanisms is presented, this design making use of a mechanical differential as central element. Differential coupling between an intrinsically high impedance transducer and an intrinsically low impedance spring element provides the same benefits as serial coupling [4]. However differential coupling allows new interesting design implementations possibilities, especially for rotational actuators