Design,Kinematics Analysis And Experiment Of Tendon-Driven Dexterous Finger

Currently, space in-orbit maintenance tasks mainly rely on the astronauts. While, the harsh space environment is too dangerous to astronauts. Multi-fingered dexterous robot hands, based on space in-orbit maintenance tasks, are undoubtedly the best choice to assist or replace the astronauts in space tasks performing. However, most of dexterous robot hands ignored the impacts of space environment in mechanism, electrical and sensor systems designing. Based on the support of the National 863 Program, a dexterous finger is designed, which focuses on space in-orbit maintenance tasks and space environment. In addition, its kinematics characteristics and control performance are analyzed. The main contents of this paper are as follows: the dexterous finger design specifications analysis, design and analysis of mechanical systems, kinematics analysis and control experiments with a dexterous finger prototype.Firstly, based on the anatomy of human finger and space in-orbit maintenance tasks, design specifications and overall schemes of the dexterous finger designed, including the degrees of freedom(DOF) configuration of the finger, drive and transmission schemes design. In order to be similar to human finger in dexterity, the dexterous finger is designed with four joints and three independent DOFs. Wherein, the MP joint is a two DOF differential coupling joint, the PIP joint is a one DOF joint, DIP joint is coupled to PIP joints with a "?" type preloaded coupling mechanism. With "N-type" transmission system, the size of the drive system is reduced effectively, and the differential coupled mechanism is achieved. In order to achieve the internal and external information of the finger, sensor system is designed with giant magnetoresistive angular position sensors of drive units and tendon tension sensors to get the joint torque and the joint position of finger indirectly.Second, as a series articulated robot system, the finger is modeled. The transmission map between drive space and joint space is descripted and tendon length compensation is done for the long tendon elastic transmission system. Based on D-H parameters, kinematics analysis of the finger is done, based on which the working space is drawn. The mapping between drive space and joint space is analyzed based on the characteristics of the "N" type transmission system. The precise map between the joint space, drive space and tendon tension, achieved by tendon length compensation, provides a theoretical basis for the joint position measurement.Finally, taking the non-linear characteristics of long tendons transmission system of the dextrous finger and the indirect joint position and joint torque measurement into account, a real-time test system for the dextrous finger was constructed, with which the position tracking performance of the dextrous finger with long tendons transmission system in joint space and Cartesian space is tested. Position control(joint space position control and Cartesian space position control) tests shows that the dextrous finger position tracking accuracy is good. Joint space forces impedance control tests shows that the fingertip force response fast. These tests together shows that the tendon-driven finger is designed rationally.