Dynamic Modeling And Control Strategy Formulation Of Milling Device Of The Milling-grinding Train

In recent years,the increasing of the transportation speed and capacity have led to the intensification of the dynamic effect between wheel and rail,and accelerated the formation speed of rail surface diseases.Therefore,the efficient rail maintenance machinery is urgently needed to maintain the rail lines,which promotes the demand for new efficient rail milling-grinding trains to present a strong growth trend.In the process of the milling-grinding train,the milling device is positioned on the rail surface,which causes the reference position to change in real time.And the milling depth of online processing needs to be adjusted in real time.Thus,the variable exciting force of the milling device will affect the dynamic characteristics of the system to change in real time.Therefore,it is difficult to accurately control the feed movement.And the effect of processing operation is seriously affected.In this paper,the dynamic model of the milling device is established based on the milling device of the rail milling-grinding train.The accuracy of the dynamic model is verified by simulation and experimental results.And a control strategy of servo motor is proposed to improve the milling quality of the milling device.The main research contents are as follows:(1)Joint load calculation of the milling device.According to the relationship between the milling depth of the milling cutter and the milling force,and the distribution ratio of the supporting reaction force in the design of the milling device,the trend of the external load on the milling cutter,positioning shoe and hydraulic cylinder are deduced.Based on the classical mechanics theory,the change rule of external load on the guide slider,bearing and bolt joints are analyzed.The results show that the external load on each joint increase with the gradual increase of the milling depth.(2)Modeling and dynamic characteristic parameter analysis of the key joint for the milling device.According to the contact characteristics and actual stress conditions of each joint,the equivalent dynamic models for bearing joint,guide rail joint,screw joint and hydraulic cylinder joint are established.The dynamic characteristic parameters of guide slider and bearing joint are analyzed respectively by using the theory of elastic oil film lubrication and the Hertz contact theory.According to the Takashi Yoshimura method,the dynamic characteristic parameters of the screw joint is calculated.The stiffness characteristic parameter of the hydraulic cylinder is calculated based on the relationship between the volume change rate of hydraulic oil and the stiffness characteristic.The results show that the equivalent stiffness and damping parameters of each joint increase with the increase of the milling depth.(3)Dynamic simulation and the test of the milling.The stiffness and damping parameters of the joints are extracted based on the milling depth of the corrugation.The dynamic model of the milling device is established.The dynamic characteristics of the milling device are simulated according to the different processing methods of the joints.The modal test of hammering method is carried out on the milling device.The relative error between simulation and test results is compared and analyzed.The accuracy of the equivalent dynamic model of the milling device is verified.(4)Rigid-flexible coupling dynamics simulation and control strategy formulation of the milling device.The rigid-flexible coupling dynamics model of the milling device is established by flexible processing of some parts for the milling device.According to the torque characteristic curve of the servo motor in the feed system,the driver program is applied to analyze the influence of the flexible parts on the feed transmission.The delay time of the rigid-flexible coupling dynamics model is analyzed.Based on the delay time,a servo motor control strategy based on motor torque characteristic curve is proposed.And the feasibility of the strategy is verified by simulation.The results show that the equivalent dynamic model and the control strategy for the milling device system have reference value for improving the repair effect of the milling device.