Design And Implementation Of EtherCAT-based Control System Of Flying-around Simulator

With the rapid development of space technology in various countries,the flight mission of spacecraft and other spacecraft has become more diversified and complicated.Spacecraft flying-around plays a particularly important role in the rendezvous and docking,formation flight,anti-satellite strategic weapons,on-orbit monitoring and other space missions.Due to the uncertainty of the space environment and the complexity of the spacecraft mission,simulation experiments on the ground need to be carried out before the spacecraft is launched to verify the reliability of whole system.The traditional ground simulation equipment has been unable to achieve the process of flying-around,so it's urgent to develop a new type of ground simulation equipment for flying-around.To this end,the research and design of simulation system for flying-around is carried out in the paper.Firstly,the demand of the flying-around simulator system is analyzed,and the overall scheme of the system is determined.The two three-degree-of-freedom turntables are used to simulate the attitude motion of the tracking spacecraft and the non-cooperative target spacecraft.At the same time,the EtherCAT bus is used to simplify the design of the electronic control system,and the selection of key components is completed in accordance with the system performance requirements.Secondly,the requirements of system software is analized and the overall architecture of the system software is detemined.The modular design is adopted and the design of the main function modules is completed.And under the Windows platform,the Ether CAT master program is developed using the Winpcap and a high-precision timing method is proposed.Then,the servo control system design is implemented.Taking the single degree of freedom as an example,the general design method of the current loop,the speed loop and the position loop controller is given.The design of the feedforward controller is carried out to improve the dynamic performance of the system,and the disturbance observer and the double position feedback scheme are respectively designed to solve the problem of load variation and rotational arm oscillation in actual system.Finally,the measurement of the system's integrated accuracy is completed.The establishment of coordinate system,the calibration of the zero position and the measurement of the integrated precision are carried out by using the laser tracker.The method of piecewise linear interpolation is used to compensate error.And the final results of accuracy measurement is given to verify the system to meet the requirements.