Reflexes in Variable Stiffness Actuators

Kurzfassung

In humans, as well as in animals, reflexes are responsible for a variety of tasks in motion control. This thesis aims to analyze reflex mechanisms and transfer them to a Variable Stiffness Actuator (VSA) joint in the DLR Hand Arm System of the German Aerospace Center. The reflex arcs in humans are studied from input organ to activated neurons and muscles. Three main reflexes in skeletal muscles are identified: The stretch reflex, the Nociceptive Withdrawal Reflex (NWR) and the autogenic inhibition. An implementation hierarchy is proposed and the mathematical stability of the controller is shown. Fast, online generated NWR trajectories for VSAs are best of jerk-limited type and damage of the spring can be avoided by temporarily switching into torque control. The advantages to performance and safety of the system are experimentally proven. A prototype of the DLR artificial skin is mounted on the forearm of the DLR Hand Arm System for the experimental setup.