Research On Key Technology Of High Quality Position Control For Servo System

The “Made in China 2025” requires China to transform from “large manufacturing country” to “manufacturing power”,and improve the national manufacturing industry innovation ability,strengthen the industrial basic ability,and accelerate the development of key technologies and products such as intelligent manufacturing equipment and core components.Among them,the position servo system is a key component in the fields of high-end computerized numerical control(CNC)machine tools,robots,and intelligent manufacturing engineering,and its key performance such as position tracking accuracy,feed speed harmonics,and anti-interference ability directly determine the core performance of the above equipment.However,high-end position servo systems,such as CNC systems and high-precision stages,are still occupied by foreign brands.Therefore,the key technology of high-quality position control of the servo system studied in this paper has important market value and strategic significance.This paper studies the key technology of high-quality position control,which can effectively improve the trajectory tracking accuracy,disturbance suppression performance,and feed speed smoothness of the feed position servo system,as well as the ability to suppress the natural vibration of the mechanical system.The specific research contents are as follows:In order to suppress the mechanical transmission resonance and lightly damped flexible load vibration in the feed position servo system.In this paper,a suppression strategy is studied,including the resonance suppression of parameter mapping Tustin discrete notch filter and the vibration suppression method of flexible beam load based on 1-cosine acceleration trajectory planning.Firstly,the double inertia resonance model of the feed mechanical system is established,and the resonance mechanism is analyzed.The parameter mapping Tustin discretization notch filter is designed to correct the distortion caused by the traditional Tustin discretization method,and the double resonance frequency suppression of the position servo system is realized.Secondly,in this paper,the light damping flexible load is equivalent to the flexible beam load,and the dynamic model of the flexible beam load is established based on the Euler-Bernoulli theory.The vibration mode and natural frequency are obtained,and the transfer function from the motor torque output to the flexible beam load is established.The vibration suppression mechanism of notch filter,input shaping and trajectory planning on light damping flexible beam load is analyzed theoretically.Compared with notch filter and input shaping to suppress the vibration of flexible beam load,the 1-cosine acceleration trajectory planning designed in this paper meets the requirements of both trajectory accuracy and vibration suppression at the end of flexible beam load.Finally,the mechanical natural vibration suppression strategy proposed in this paper can effectively suppress mechanical resonance and flexible load vibration,and improve the trajectory tracking accuracy of the system.For the disturbance suppression method,the electrical disturbance and mechanical disturbance existing in the feed position servo system.To solve this problem,this paper studies a composite control strategy which combines phase angle compensation resonant control and second-order sliding mode disturbance observer.Firstly,the electrical disturbance equations introduced by current sampling gain and bias error factors in position servo system and the differential equations of mechanical disturbance introduced by mechanical transmission,external disturbance torque,nonlinear friction and variable system parameters in position servo system are established respectively.the parallel phase angle compensation resonant controller is proposed to suppress the feed speed fluctuation caused by electrical disturbance.The second-order sliding mode disturbance observer is proposed to estimate the disturbance caused by mechanical factors,and the estimated disturbance is added to the control system through feedforward to effectively suppress the feed speed fluctuation and tracking error caused by mechanical disturbance.The disturbance suppression mechanism of the proposed composite control strategy is analyzed theoretically,and the design and parameter tuning process of the control strategy are given.The experimental results show that the proposed composite control method can effectively improve the disturbance rejection ability of the feed position servo system.A series-parallel coupling iterative learning control strategy and a controller parameter tuning method are studied in this paper for the working conditions of trajectory repetition and high demand for trajectory accuracy and feed rate fluctuation in the feed position servo system.Firstly,the parallel iterative learning control is designed according to the system model,and the frequency domain tuning method of its learning equation parameters and phase advance order is studied.Parallel iterative learning control has a high learning bandwidth,which can suppress the feed speed fluctuation within the learning bandwidth,but the tracking accuracy of the trajectory in the speed transient stage still has room for improvement.Furthermore,a method of coupling series iterative learning control after using parallel iterative learning control is proposed,and the frequency domain tuning method of the learning equation parameters and phase angle advance order is studied.Finally,a non-causal filter is designed to suppress the noise in the tracking error within the learning bandwidth without causing phase lag of the tracking error information.Experiments show that the proposed series-parallel coupled iterative learning control strategy improves the tracking accuracy of the whole trajectory segment under repeated trajectory conditions and reduces the feed rate fluctuation within the learning bandwidth.It is of great significance to improve the tracking accuracy of the position servo system under non-repeatable trajectory working conditions.Therefore,this paper studies an finite impulse response(FIR)type dynamic compensation feedforward control and closed-loop error feedforward control and parameter tuning strategy.According to the system dynamics model and considering discretization,delay,and trajectory planning,the dynamic compensation feedforward control strategy in FIR form is proposed.In order to further improve the tracking accuracy of the positioning system,the transfer function of the closed-loop residual tracking error of the system after the dynamic compensation feedforward control in the form of FIR is derived.Combined with trajectory planning and considering the influence of discretization and delay,a closed-loop error feedforward control strategy in the form of FIR is proposed.Aiming at the difficulty of parameter tuning of the FIR feedforward controller,the controller parameter tuning method based on iterative learning data is proposed to solve the problem of controller parameter tuning.Combined with the phase angle compensation resonant controller and the second-order sliding mode disturbance observer proposed in this paper,the anti-disturbance ability of the proposed feedforward control strategy can be effectively improved.Experiments show that the proposed FIR form feedforward control and tuning parameter strategy can be extended to different trajectories,and the parameters are adaptable under the same velocity,acceleration,jerk,and jerk but different position trajectories.