| The Control Moment Gyroscope(CMG)has been the key actuators of attitude control system in agile maneuver spacecraft because of its advantageous features including fast-response,large outputting torque and ability of continuous torque outputting.Compared with the traditional mechanical CMG,a magneticlly suspended control moment gyroscope(MSCMG)supports its high-speed flywheel rotor by magnetic bearing,which has inherent superior features such as adjustable bearing,low vibration,zero friction and longevity,and it has been becoming the ideal solution for fast-response and high-precision attitude control for maneuver spacecraft.In order to achieve high-precision control performance,this dissertation focuses on the key control technologies of the MSCMG,including high performance driving technology of high-speed flywheel,high-precision speed control of gimbal servo system,suspending control of high-speed flat rotor,control system design and implementation.The main contributions are listed as follows:(1)In order to achieve the capability of high reliability,high safety and low power consumption in aerospace applications,a high performance driving scheme for high-speed suspending flywheel rotor of the CMG is proposed.Firstly,the driving performance of the traditional three-phase inverter and buck-converter based three-phase inverter for high-speed brushless direct current(BLDC)motors used in flywheel are analysed,a highly fault-tolerant power converter based on buck-converter with three-phase H-bridge combinations is presented.Secondly,the zero-crossing points(ZCPs)of back-electromotive force(EMF)detection circuit is designed and the position detection error is analysed.Thirdly,a speed measurement with enhanced detection frequency and accuracy is proposed.Then,a fast two-stage commutation instant shift compensation method is designed based on the unique speed measurement method.High reliable and accurate commutations are achieved especially in the high-speed steady state,which improves the speed control precision and decreases the motor driving loss.Finally,the control system design process is proposed and a fault tolerant control strategy is presented to enhance the reliability of the system.Experimental results illustrate the effectiveness and practicability of the proposed inverter scheme and the position sensorless control method.(2)High-precision torque control for variable speed CMG(VSCMG)under reaction flywheel mode is studied.In order to meet the control requirement of high attitude stability for the agile spacecraft in steady state and improve the torque-output precision of the variable speed MSCMG under reaction flywheel mode,compensation methods are proposed respectively to attenuate the undesirable torque ripple caused by nonideal back electromotive force waveform and commutation in classical control of brushless DC motor.The real-time back EMF is estimated according to rotor position and speed to obtain reference current,Pulse width modulation duty cycle is calculated in the torque controller.The theoretical derivation is analyzed,methods of modulation of the non-commutation phase during low-speed range and modulation of the switching-out phase during high-speed range are presented based on the characteristics respectively.Also,calculation method of the commutation time is given.The experimental results show that the proposed method can achieve an effective compensation effect.(3)A high-precision speed control based on multiple phase-shift resonant controllers for gimbal servo system in MSCMG is proposed.At first,the periodic torque ripples caused by cogging torque,flux harmonics,inverter dead time effect and dynamic unbalance of high speed rotor are analyzed and modeled.Then,the principle and structure of MPRC parallel with proportional integral(PI)controller are discussed.The design and stability analysis of the proposed MPRC plus PI control scheme are given both for current loop and speed loop.The closed-loop stability is ensured by adjusting the phase in the entire operational speed range.Finally,the effectiveness of the proposed control method is verified through simulation and experimental results.(4)To solve the stability problem of the high-speed flat magnetically suspended rotor caused by the strong gyroscopic effect,a filter order scheduling cross feedback control approach based on the rotor speed is proposed.We first establish the model of the suspended rotor system in the generalized coordinate,in which,the non-decoupling six decentralized control channels are decoupled in five degree of freedom.A speed gain based generalized root locus cross feedback control method is designed and the detailed derivation is given.Then,a filter order scheduling cross feedback control approach is put forward,the order of the filter varies adaptively with the rotor speed to compensate the phase lag of control system for precession and nutation mode during different speed ranges.Simulation and experiment results prove that the filter order scheduling cross feedback control based on speed adaptive approach can suppress the gyroscopic effect effectively and the magnetic suspending rotor can keep high stability suspension in the whole speed range.(5)A general digital control system based on Field-Programmable Gate Array(FPGA)and Digital Signal Processor(DSP)for MSCMG is designed.Firstly,hardware analysis and design for suspension control system and gimbal servo system are conducted.Secondly,the function of the digital contolller is divided,a DSP is used as the primary controller to perform the function of computing control algorithm and a FPGA is used as secondary controller to perform data sampling,PWM generation and timing control.At last,a schme of am angle measurement system based on the two-speed resolver is designed. |
PDF Full Text Request