Human Arm Posture Optimisation in Bilateral Teleoperation through Interface Reconfiguration

In this paper we propose a method for addressing the human operator's ergonomics during bilateral teleoperation. The method is based on human operator's musculoskeletal and fatigue models, whose input is the force produced by the operator through the haptic interface (master) in order to control the slave robot in the remote environment. The system then estimates the fatigue-based endurance time for producing the desired task force in different human arm configurations within the selected workspace. We perform an online optimisation process to find the optimal configuration that has the longest endurance time, which signifies that the operator can perform the task in that configuration for a longer period. Next, a trajectory is generated on the master robot in order to guide the human arm into the optimal configuration. The teleoperation is temporarily suspended by decoupling the master from the slave robot when the master robot is being reconfigured. The teleoperation will be resumed and the slave robot will be teleoperated again from where it stopped after the master robot guided the operator's arm to the optimised configuration. The main advantage of the proposed method is that the human operator can perform the task with less muscle fatigue, which increases the endurance time. To validate our approach, we performed proof-of-concept experiments on a teleoperation system composed of two Panda robots by Franka Emika, where one was serving as master and the other as slave. The main experimental task was for the human operator to produce a reference force with the slave robot on an object in a remote environment. A supplementary task involved putting an object of unknown mass on the slave robot end-effector.