| In order to improve the quality of the disabled people's life, the research on humanoid prosthetic hand is of great importance. This paper is based on national high technology research and development program"Research on high performance humanoid prosthetic hand"(No. 2009AA043803). Design and improvements for the mechanism of the humanoid prosthetic hand are carried out. The kinematic analysis and static analysis for the index finger are established by bar-group method. The force-tracking impedance control algorithm of the prosthetic finger is studied, based on which, simulation and experiment are carried out.First, the research situations of prosthetic hand in and out of China are analyzed, based on which, the basic features and development direction of the research on prosthetic hand are summarized. The research situation of force-tracking impedance control is analyzed and several algorithms are compared with each other.The fingers of the prosthetic hand are based on coupling linkages. The three phalanxes of each finger are motivated by one motor. The hand weighs 420g and its size is 95% of a normal human hand's. Its appearance is nice and it is smart and light. Owing to the design and improvements for the mechanism of the prosthetic hand, the strength and stiffness of the mechanism are enhanced, and the reliability of the parts'orientations and linkages are improved. The cost of the manufacture is decreased by increasing the modularization level of the electronic system.Based on the theory of Assur group, the models of the kinematic analysis and static analysis for the four-linkage structures of the prosthetic index finger are established by bar-group method. With the help of Matlab, the kinematic analysis and static analysis are carried out, which have been validated by the simulation in ADAMS. The results prove that the coupling movement of the joints tally with the design requirement, which also provide the foundation of the control algorithm of the prosthetic hand.In order to overcome the instability of the hybrid position / force control in the control mode switch and the force-tracking disability of ordinary impedance control, a force-tracking impedance control algorithm of the prosthetic finger is studied. The algorithm is composed of an impedance filter with an adaptive control method and a robust position control method based on Time-Delay Estimation (TDE), which can overcome the uncertainty of the environment position and dynamics of the finger respectively. In order to overcome the uncertainty of the dynamics of the finger, the equivalent inertia of the four-linkage structures of the prosthetic index finger to its base joint is calculated, and the lower bound of the inertia term in the dynamic equation during the finger's movement is made sure.Finally, with the help of Simulink in Matlab, the model of the force-tracking impedance control system for the prosthetic finger is established, and the affects of the control parameters on the force-tracking ability of the system is studied based on simulations. Moreover, the force-tracking ability of the system is tested by experiments. The results of the simulations and experiments show that the control system can overcome the uncertainty of the environment position and performs well in force-tracking. |
