Research On The Nonlinear Backstepping Control Of Electro-hydrostatic Actuator For Rail Grinding Vehicles

With the rapid development and requirements of high-speed,heavy-duty and passenger comfort railway in China,the line acceptance standards have gradually improved,forcing the further innovative development of large-scale line operation and maintenance equipment.Taking the rail grinding truck,which is widely used in rail operation and maintenance equipment,as an example,it has the characteristics of complex working conditions,limited installation space,high risk of failure,poor maintainability and so on,which puts forward higher requirements for the power transmission system.Combined with the trend of energy saving and emission reduction and the development of all-electrification of equipment,this thesis proposes the strategy of using Electro-Hydrostatic Actuator(EHA)instead of rail grinding vehicle grinding motor lifting and grinding head deflection cylinders.And taking control accuracy and response speed as indicators,considering the influence of nonlinear factors,based on PID,sliding mode variable structure,backstepping control algorithm for simulation and experimental research.The main work of the thesis is as follows:(1)A lot of challenges existing in the rail grinding vehicle under the background of the development of large-scale operation and maintenance equipment of railway lines tending to be fully electrified are summarized.Based on the current construction process difficulties of rail grinding vehicle,the EHA is proposed to replace the grinding motor lifting and lowering and the deflection of the grinding head deflection cylinders of rail grinding vehicles.(2)The working conditions of the rail grinding vehicle grinding device are analyzed,and the EHA design requirements are condensed.Then the special EHA for the rail grinding vehicle are designed.And the nonlinear efficiency of EHA pumps based on volume loss and the nonlinear friction effects of hydraulic cylinders based on Lu Gre model are researched,and establishing the mathematical model of the EHA system and nonlinear factors.(3)The EHA control strategy is studied by using three control algorithms: PID,sliding mode variable structure and backstepping.In order to comprehensively evaluate the control accuracy and response speed,the rise time and control accuracy of the EHA step response are selected as the evaluation index,and the maximum overshoot is introduced as the penalty power index factor to build a scientific and objective EHA control performance evaluation system.(4)The virtual prototype of piston pump,hydraulic system and control system are constructed,which verify the correctness of the piston pump model,EHA hydraulic system,control system and multi-system coupling.Based on the simulation analysis of the joint simulation model,compared with the PID and sliding mode variable structure control,the backstepping control has a fast response speed and the control accuracy can reach up to0.035 mm.(5)EHA and four-quadrant working condition test platform are manufactured,the fourquadrant working condition and amplitude frequency characteristics tests are completed.Then,the performance of control algorithm is tested by test platform.Based on the evaluation results of simulation for control algorithm performance test under the load,backstepping control response speed is better than PID and sliding mode variable structure control,control accuracy up to 0.21 mm.The results show that the EHA nonlinear backstepping control accuracy for rail grinding vehicle is 0.21 mm,and the response speed is better than PID and sliding mode variable structure control,which proposes a feasible solution for the power transmission system of rail grinding vehicles.