Robotic Biceps Exercise Machine: Hardware Using Series Elastic Actuator and Control with Disturbance Observer

Resistance training is a popular form of exercise owing to its health-related and athletic performance benefits. Robotic exercise machines using human-robot interaction are a promising solution for designing resistance training programs that successfully achieve training gains. We propose a robotic biceps exercise machine that generates a variable resistance force profile and controls the interaction force corresponding to the profile through a range of motion of exercises. A series elastic actuator measures and controls the resistance force. A novel cascade control structure comprising an inner velocity and outer force control is presented. The inner loop disturbance on the dynamics and outer loop disturbance on the kinematics are eliminated by a disturbance observer (DOB) in each loop. The performance of the proposed force control scheme is validated by comparisons with the conventional DOB and proportional-integral (PI) control schemes. Additionally, the resistance force profile and interaction force of a conventional robotic biceps exercise machine are analyzed experimentally.