Research On Loading Strategies Of Passive Torque Servo System

The Passive Torque Servo System(PTSS), also known as load torque simulation system or torque loading system, is used to simulate the hinge moment acted on rudder system in the actual working condition, which plays a crucial role in testing and hardware-in-the-loop simulation of the aviation, weaponry, industrial production, scientific research and other sectors. As the motor manufacture and drive control technologies have developed in recent years, electric rudders have been widely used, and control precision and maneuverability of rudder system have increased significantly. Accordingly, higher loading performance requirement of the matching Electrical Passive Torque Servo System(EPTSS) has been put porward. Found by the theoretical analysis and engineering practice, surplus torque caused by the movement of rudder system is the main reason for restricting the loading precision and load bandwidth, in addition, electromagnetic torque ripples of the loading motor, system robustness, mechanical resonance can also cause a certain impact on loading performance, and restrict further promotion. Due to high performance requirement and control complexity of EPTSS, it has to be improved in the factors of control system structure, control strategies and EPTSS loading components.The loading performance of the EPTSS is restrained by the inner-ring performance. To improve the dynamic/static performance of the traditional current controller, the current control method of loading system is proposed. During dynamic loading, the variation of system running conditions will result in changes of armature inductance, causing failure of the current decoupling containing inductance parameters. The complex vector PI controller built by the motor complex vector model does not need any inductance parameter and thus it can effectively improve the dynamic performance and robustness of the inner ring. The generalized integrator is introduced to suppress the current low-order harmonics caused by the motor cogging effect and inverter non-linearity and improve the static performance of the current ring. The current-given forwardfeed control is added to settle the step response over-tuning after the generalized integrator is applied.The control structure is built for the EPTSS, and the necessity of introduction of speed ring is analyzed, and the speed ring controller design method is proposed to improve the system robustness. To improve the damping coefficient and anti-disturbance performance of the loading system, a control structure is proposed where the three-ring control of torque, speed and current is combined with the load torque disturbance forwardfeed compensation. To settle the uncertain parameter and disturbance of the bearing and loading systems, the improved time mean parameter identification algorithm is put forward, which can carry out accurate identification for such system parameters as the moment of inertia, the coefficient of viscosity, Coulomb friction, and the identification results are used for parameter setting of the speed ring. It analyzes the dynamic characteristics of the do uble-inertia system composed by the loading system and the bearing system. Since it may generate mechanical resonance when the system controller is saturated, the adaptive trap is used.The proportional resonant(PR) control is introduced to the loading torque outer-ring controller to simplify the control algorithm and improve the loading accuracy of PTSSs and suppress the surplus torque. One or more PR controllers are built on the basis of the expected torque and the spectral analysis of the position disturbance of the bearing system to achieve static-error-free tracking given by the harmonic frequency sinusoidal signal and effectively suppress the sinusoidal disturbance. To achieve accurate simulation of the three special torques —the moment of inertia, the viscosity torque and the elastic torque, the expected moment of inertia and viscosity torque can be directly worked out by the function relationship of the position, speed and acceleration signal in the sinusoidal movement, and static-error-free loading can be realized with combination of PR controllers to realize accurate simulation of the moment of inertia, the viscosity torque and the elastic torque. The cascading structure of multi-unit PR controllers is presented, and the frequency domain design is used to realize separate design of several integral parameters and ensure system stability and rapidness. The speed signal forwardfeed of the bearing system is introduced to suppress the impact of the loading torque over-tuning on the system at the initial loading stage and realize rapid convergence.The EPTSS where the double-stator permanent-magnet synchronous motor(DSPMSM), works as the loading component is proposed to raise the loading bandwidth. Restrained by the motor rotary inertia, the existing dynam ic performance of EPTSSs still cannot meet the demand of big torque and bandwidth. Based on the fact that the double-stator motor has high torque to inertia ratio, it proposes the loading mode based on the direct drive of DSPMSM. For the actual conditions of low speed and big torque, the DSPMSM design is presented for the EPTSS and the finite element simulation is carried out. Mathematical model of DSPMSM is established, to compare the loading performance of double stator structure and single stator structure under the same control method. It is proved with the double stator structure has higher loading bandwidth.Based on the fact that the DSPMSM has two electrical terminals, the study on synchronous controls is developed, and coordinated control is carried out for the two stator systems to realize the angle tracking control and torque tracking control of the loading motor, suppressing the surplus torque and significantly reducing the complexity of the control system.