Fault diagnosis and tolerance for elastic actuation systems in robotics: physical human-robot interaction

Abstract

In the last decades, elastic actuation receives increasing attention in robotics. Due to introducing flexible elements in the drive train, such actuators show beneficial capabilities for safe human-robot interaction and energy-efficient operation. Besides these advantages, practical implementations of such actuators have higher complexity than non-elastic ones and might be operated in more critical operating conditions. Due to these issues, fault sensitivity can increase but a structured analysis of how faults influence human-robot interaction is missing up to now. The project “Fault diagnosis and tolerance for elastic actuation systems: physical human-robot-interaction” aims at understanding these influences and develops control methods that enable fault tolerant interaction. It experimentally investigates the users’ stiffness experience and develops fault-tolerant control methods for reliable human-robot interaction. To this end, fault diagnosis methods from the previous project phase and psychological studies guide the development of fault-tolerant control algorithms.The influence of stiffness faults in wearable robots on user experience is examined in psychometric and psychophysical experiments. The resulting insights in human perception and human-robot interaction support the improvement of user and interaction models and guide the design of control and adaptation algorithms that facilitate safe and reliable human-robot-interaction. These fault-tolerant controllers detect stiffness faults with the previously developed diagnosis algorithms and actively compensate fault consequences. To examine the practical feasibility of the fault-tolerant physical human-robot interaction concepts, a variable stiffness actuator and an elastically actuated knee orthosis are implemented and considered.With the developed control and adaptation algorithms, an important step towards fault-tolerant human-robot interaction is performed. Moreover, the project contributes to the design and control of elastically actuated wearable robots and the understanding of users’ stiffness experience. Thereby, it supports the long-term goal of achieving intuitive and reliable motion assistance for healthy and physically challenged individuals.