A Control Study For The Prosthetic Hand’s Motor Drive Based On Muscle’s Drive Characteristics

Prosthetic hand is very important for disabled people to carry out a normal life and better integrate into society, so it is an urgent desire for physically disabled persons to have a bionic prosthetic hand with good security and flexibility and fast real-time control in grasping movements. The neuromusculoskeletal motion system’s variable stiffness characteristics is studied through modeling and simulation. The prosthetic hand can reproduce the muscle-driven flexibility in a certain extent by designing the control strategy of the motor drive system. The main research work includes the following aspects:(1) A muscle’s three-element lumped parameter model that is called Hill-type muscle model is used. The Hill-type muscle model intuitively shows the relationships between the output force of a muscle and the length of the muscle/velocity of muscle length changing. The dymamics model of a spindle, the muscle proprioceptor, is simulated and the results demonstrate the spindle is closely related with the muscle length, the velocity of muscle length changing and the neural input to spindle.(2) A mathematical model of a joint neuromusculoskeletal movement system driven by a pair of antagonistic muscles is built. The simulation results show that the muscle drive system behave variable stiffness characteristics in the process of freee moving and force contact space,and the force load of grasping is smooth and stable. it reveals that the hand drive system possesses a flexible drive characteristic of variable stiffness.(3) A bionic tracking control strategy based on the neuromusculoskeletal motion model is proposed. PID controller and fuzzy PID controller are designed, and simulation analysis is carried out in two aspects of motor speed control and force loading control. The simulation results can confirm the rationality and effectiveness of the control strategies and the controller.(4) Based on LabView platform, a motor-driven online real-time closed-loop control system is built. The experimental programs of motor control and force loading are designed so as to achieve the closed-loop control of position, speed and force, and the experimental data has been analyzed. The experimental results confirm that to a certain extent the motor can realize muscle’s flexible drive by active control.