Development of series elastic actuator based myoelectric knee exoskeleton for trajectory generation and load augmentation

This paper describes the development and control of a series elastic actuator based myoelectric knee exoskeleton which can be used for gait rehabilitation and load augmentation purposes. The device consists of a motorized ball screw mechanism along with a spring placed between the motor and load. In load augmentation mode, the spring strain is measured to get accurate estimate of force which can be controlled in force feedback mode for amplifying force according to user's intention. User's intention is reflected in myoelectric signal. For gait rehabilitation purpose, this device has been developed to function as a normal knee joint during walking by acquiring myoelectric signals from muscles around knee and joint trajectory information. Joint angle obtained from position sensor is combined with the gait parameters acquired from EMG and they are fed to a PID servo which has been developed to control knee angle trajectory of the exoskeleton. Functioning, control and acceptability of the exoskeleton device increases to a user as the system is run and controlled by user's own intention.