| Abstract:Prosthetic hand stably and effectively grasping object is the premise of its wearer completes various tasks in the daily life, so grasping force control system with simple structure and good dynamic response characteristics is very important for the application and popularization of the prosthetic hand. To analyze the influence of prosthetic hand restore spring stiffness and object stiffness on the dynamic response, the system characteristics of tendon-driven prosthetic hand is studied. Then, we established the dynamic mathematical model of the Force Sensing Resistors and studied the impact of pressure sensor FSR on control performance. In order to improve the response characteristics of the prosthetic hand system, a controller is designed based on the analysis results. The primary work in this thesis is as follows:Firstly, we established the system model of prosthetic hand and studied the influence law of prosthetic hand restore spring stiffness and object stiffness on the dynamic response. In addition, the open loop system stability and response characteristics were analyzed.Response characteristics of pressure sensor are obtained through experiment. According to the experimental results, a series of dynamic mathematical models with different order of the pressure sensor are established based on approximate optimal auxiliary variable method. Through the experimental comparison, an appropriate sensor model is selected.We analyzed the influence law of pressure sensor characteristics, prosthetic hand restore spring stiffness and object stiffness on the grasping force control performance with PID controller.Due to the presence of non-model error, such as external disturbances, system friction and clearance, the traditional PID cannot obtain the expected control effect, so, a fuzzy PID controller is designed to improve the system response characteristics.Finally, an experimental platform is established to study the control performance of control system, finish the data acquisition of grasping force via the force sensitive resistance and conduct the real-time control on NI virtual instrument platform. We develop the software control system and data acquisition based on Labview. Finally, the experiments of grasping force control were conducted, and the result verifies the effectiveness of control system. |
