Admittance Control Based on EMG-Driven Musculoskeletal Model Improves the Human–Robot Synchronization

The synchronization of output torque is an important issue during human-robot interaction. Since the human-robot synchronization may be affected by the delay between the human's voluntary torque and the robot's assistive torque when a torque sensor is applied to detect human intention, an electromyography (EMG)-based admittance controller (EAC) was proposed to improve human-robot synchronization compared with that achieved by the use of a torque-sensing-based admittance controller (TAC). Simulations and experiments were conducted to investigate the performance of the EAC and the TAC. The simulation results indicated that the delay between the human's voluntary torque and the exoskeleton robot's assistive torque significantly degraded the performance of the human-robot cooperation movement when the TAC was used. The experimental results indicated that the jerk value, interaction torque, and EMG level of the tibialis anterior obtained with the EAC were significantly smaller than those with the TAC. Compared with the TAC, the EAC has an advantage in improving human-robot cooperation movement because the EAC can reduce the delay between the human's voluntary torque and the exoskeleton robot's assistive torque.