Development of Sensory Feedback Device for Myoelectric Prosthetic Hand to Provide Hardness of Objects to Users

Abstract

In this paper, a sensory feedback device was developed to improve the operability of a myoelectric prosthetic hand. The device is worn on the user’s upper arm and provides object hardness feedback to by winding a belt onto the upper arm using a motor. When the finger of the myoelectric prosthetic hand grabs the object, the contact force on the object is detected by a pressure sensor attached to a finger cushion on the myoelectric prosthetic hand. Based on the sensor’s input, the hardness of the object is calculated. According to the hardness of the object, a reference input to realize the corresponding winding speed of the belt is generated by a reference input generator. Then, the motor of the feedback device is controlled to track the reference input by using the self-tuning PID control technique, taking parameter variation into account. Thus, the belt of the feedback device is wound by the motor and tightens the user’s upper arm, thereby enabling the user to receive tactile feedback. Finally, confirmation tests are conducted based on a psychophysical method to verify the effectiveness of the feedback device and its control system. As a result, the difference threshold of the sensory feedback device was 0.59 N/mm.