Design and calibration of spoke piezoelectric six-dimensional force/torque sensor for space manipulator

The large manipulator outside the space cabin is a multi-degree of freedom actuator for space operations. In order to realize the automatic control and flexible operation of the space manipulator, a novel spoke structure piezoelectric six-dimensional force/torque sensor with redundancy ability, high stiffness and good decoupling performance is innovatively proposed. Based on the deformation coordination relationship, the redundancy measurement mechanism is revealed. The mathematical models of the sensor with and without branch fault are established respectively. The finite element model is established to verify the feasibility of structure and redundancy measuring principle of the sensor. Depending on the theoretical analysis and simulation analysis, the prototype of the sensor is developed. Static and dynamic calibration experiments are carried out. The actual output voltage signal of the six-dimensional force/torque sensor is collected to establish the equation between the standard input applied load and the actual output voltage signal. Based on ant colony optimized BP algorithm, performance indexes of the sensor with and without branch fault are analyzed respectively. The experimental results show that the spoke piezoelectric six-dimensional force/torque sensor with the eight-point support structure has good accuracy and reliability. Meanwhile, it has strong decoupling characteristic that can effectively shield the coupling between dimensions. The nonlinear errors and maximum interference errors of decoupled data with and without branch faults are less than 1% and 2%, respectively. The natural frequency of the six-dimensional force sensor can reach 2856.45 Hz and has good dynamic characteristics. The research content lays a theoretical and experimental foundation for the design, development and application of the new six-dimensional force/torque sensors with redundancy. Meanwhile, it will significantly improve the research level in this field, and provide a strong guarantee for the smooth implementation of force feedback control of the space station manipulator project.