Research On Capture Tool Controller And Servo Control Strategy

In order to maintain the sustainable development of space activities,countries began to develop on-orbit service technology.On-orbit capture technology is the premise and key to on-orbit service.In this paper,the manipulator end effector for in-orbit capture,ie the catching tool,is developed,the controller of the catching tool is developed,the servo control strategy of the catching tool is developed,and the ground test is carried out to verify the catching performance of the catching tool..This paper first carried out the sensor system design and electrical system design of the capture tool.The capture tool design integrates a variety of sensors for vision,position,current and temperature,and has a rich sensing capability to fully sense its own state and capture target status.For the complex conditions of space,the electrical system of the capture tool has the characteristics of high reliability,high integration and low power consumption.Secondly,the capture process of the capture tool is analyzed and divided into three phases: the collapse phase,the drag phase and the locking phase.According to the functional requirements of each stage,a composite servo control strategy of speed control and torque control is proposed.Speed control is used during the closing and dragging phase and torque control is used during the locking phase.Speed control uses speed loop and current loop double closed loop control to ensure the speed response speed.Torque control uses feedforward control based on the locking force model.In order to simplify the system,the bus current detection is used to reconstruct the phase current of the motor,thereby completing the current loop closed loop.The servo control model was established in Simulink and the control simulation was carried out.Then,the controller design based on the anti-fuse FPGA is completed.The hardware programming language is used to realize the SPI interface acquisition function of the AD converter,the monitoring bit input interface acquisition function,the PWM square wave modulation of the DC brushless motor,the real-time calculation of the motor speed,the PI adjustment of the motor speed loop and the current loop,and the motor holding brake.Control and communication with external serial bus.Each module was simulated and verified by Modelsim.Finally,the capture tool controller performance test and capture experiment were performed.A controller test experimental platform was built to test the performance of the current loop and the speed loop.The results show that both the current response and the speed response can meet the requirements of the capture function.A simulation capture experimental platform was built and a capture experiment was carried out.The experiment proved that the capture tool can complete the capture of the target within the specified time.