Research On The Joint Of The Reconfigurable Space Manipulator With Wireless Communication

Affected by fuel depletion,space debris and faults,the maintenance and capacity of these space assets become an important issue to improve space efficiency and ensure the capability of spacecraft. On-orbit servicing is of great significance to the development of China’s space events. It is a reliable way to prove on-orbit service by using the space manipulator instead of astronauts in the complex space environment. The development of reconfigurable robotic manipulator makes a single mechanical arm complete several different on-orbit tasks possible; Wireless manipulator with fast response overcomes complex and redundant cable wire in the traditional mechanical arm,shortens the cycle of design and debugging. Aiming at the goal of space on orbit service,this paper proposes a wireless and reconfigurable space manipulator.According to the requirement of the space manipulator in orbit,the technical indexes of the space manipulator are analyzed in detail and the modular joint of the space manipulator is designed. Joint is the core of the mechanical manipulator with a set of mechanical,electrical,control and integration of modular components. In the mechanical design,with the reference to the previous mechanical arm joint design,we use the hollow brushless DC motor and harmonic reducer to meet the requirements of hollow cable routing and improve the accuracy of joint transmission. The joint is equipped with rich sensors,including the incremental encoder at the end of the motor,Hall sensor fixed on the motor,the absolute encoder fixed at the end of the joint,the torque sensor fixed on the harmonic drive. Through merging sensors,we can improve the position accuracy. In order to realize the mechanical arm of the reconstruction, the design of the joint can be reconfigurable interface, reconfigurable interface design with steel ball locking the purely mechanical scheme. The reconfigurable interface is improved on the basis of the pneumatic quick joint, which comprises three parts: the active interface, the passive interface and the auxiliary tool. The auxiliary tool is installed on the base, which is used for controlling the position of the clamping sleeve to control the installation and separation of the active interface and the passive interface. The air plug is arranged in the middle of the quick joint, and the electric connection is completed at the same time of the mechanical connection.According to the accuracy and control requirements of the manipulator, the joint servo control system is developed, and the vector control of the brushless DC motor is simulated by using MATLAB. The control system adopts distributed control system, which includes the upper computer and the lower computer. The upper computer is based on PC,which is used to send commands to the joint controller. The lower computer includes joint controller and actuator. The control of the torque loop,position loop and speed loop of the joint is realized in ARM3. Between the upper computer and the lower computer,WIFI is used for wireless communication. The control of the motor adopts vector control strategy. The paper uses MATLAB to simulate the vector control. The simulation shows that the vector control has higher control precision and faster response.According to the design indexs of the manipulator, joint and interface, the experiment of joint and interface is carried out. Experiments includes single joint torque,position,speed and current tracking experiment,output torque,stiffness,the function of the two joints and the quick change interface functional experiment. The experimental results shows that the developed system has large load,high precision and satisfies the design requirements.