Motion Control of Series-Elastic Actuators

Direct, physical interaction between a human and a robot has potential to provide assistance or rehabilitation which can extend the human user's physical capabilities. To be successful, the robot must be able to realize the system-level objectives without compromising the subject's safety. For applications which involve a powered robot, compliant actuators may help guarantee safety. However, the more complex dynamics of compliant actuators requires proper model selection and controller design to give satisfactory performance. Here, a series-elastic actuator integrated to an upper-limb exoskeleton is considered. To consider the effects of the elastic element, a model for the series elastic actuator with load-side dynamics is introduced, validated, then used for controller design. The performance and safety of several control architectures are analyzed, then compared experimentally.