Fault-Tolerant Force in Human and Robot Cooperation

Fault-tolerant solutions greatly benefit the dependability of robotic systems. This advantage is critical for robotic systems that perform in collaboration with humans. This work addresses the fault tolerance of robotic manipulators for cooperatively manipulating an object together with a human. Cooperation occurs for slow lifting or pushing of the object. Reconfiguration of the manipulator is performed to maintain the cooperative force level despite the occurrence of robot joint failures. We present several strategies that are investigated for optimally maintaining the required force level for human-robot task cooperation. For each strategy, a reconfiguration control law is introduced that optimises the fault tolerance of the maintained force level. Three case studies are introduced to validate the proposed reconfiguration laws,demonstrating that this approach results in an optimal fault-tolerant force in human-robot cooperation.