Research On Compliance Control Of A New Spherical Wrist Based On The Friction Compensation

Many fields such as military、aerospace、nuclear have become the strategic targets by developed countries racing to develop, its external operating environment is narrow、 complex、dangerous、unstructured and so on. These operation occasions are unsuitable for people to work, so there is an urgent need to develop high-performance robot for human. The wrist is key components of the robot, its performance directly affect end effector’s positioning accuracy、flexibility etc. In order to improve the operational capability of the space robot and break through the bottleneck problem of the wrist module, it has become a top priority to develop high-performance wrist with compliance operation ability for external enviroment.This paper proposes a3-dof decoupled spherical robotic wrist with high integration and relative independence movement chains. The structure of the spherical wrist was analyzed, and double universal joint and double hemisphere structure are employed to guarantee the wrist compactedness and flexibility. The workspace of the wrist joint is analyzed and its kinematics model is derived by the transfer matrix and geometrical analysis, Jacobian matrix of robotic joint had be inferred and the singular position is analyzed, and a3-dof decoupled spherical robotic wrist with high integration had been designed, manufactured and tested. Simulation and experimental assessment of the joint performance demonstrates that the wrist could realize the pitch, yaw and rotation in stable and flexible way.Based on the large number of literatures about compliance control that we looked up and summarized, the3-dof decoupled spherical robotic wrist with high integration was charged as the research object, this paper studying the decoupled spherical wrist compliance control principle based on the friction compensation, exploring the feasibility of compliance control based on the friction compensation.A series of ideas was put forward in this paper in order to realize the compliance control of the decoupled spherical wrist. Established a suitable friction model for wrist module and the model is processed to comply with the requirements of the application. Maked appropriate experimental and simulation program and identified the systerm friction parameters based on the genetic algorithm. Installed a force sensor on the wrist end and established the motor torque model under the compliance control considering the end contact force and resisitance. The genetic algorithm identification program is completed. The simulation model of compliance of the decoupled spherical wrist was set up with the use of Simulink toolbox provided by MATLAB. Based on the simulation results, the feasibility and effectiveness of the compliance control mode of the decoupled spherical wrist based on the friction compensation is verified.This paper integrated the new robot wrist mechanism、friction model parameter identification and compensation and put forward the design method and control theory of the compliance control of the decoupled spherical wrist based on the friction compensation. The wrist has great application value and also the compliance control mode based on the friction compensation has general application significance.