| The dynamics performance of rail vehicle is regarded as an important indicator to assess the performance of rail vehicle and determines whether the rail vehicle can be put into use,moreover, it has widely gained a lot of attentions from experts and scholars. And instrumented wheel-set plays an important role in rail vehicle dynamics performance test. The interaction force between the rail vehicle and the wheel rail can be detected by the instrumented wheel-set, the corresponding derailment coefficient can also be calculated and so on, and the dynamic performance of the rail vehicle is evaluated. The calibration of instrumented wheel-set with high precision plays an extremely important role in rail vehicle dynamics performance test, the accurate calibration of instrumented wheel-set has become the premise of the vehicle dynamics test. The above problems have been solved by the development of test bench for instrumented wheel-set. How to achieve the accurate loading and precise measurement of wheel / rail forces and the relationship between wheel / rail forces and shape variables, which has become a focus for the research of the calibration test bench for instrumented wheel-set. In this paper, the vertical hydraulic loading system is regarded as object in the instrumented wheel-set calibration test bench. To achieve the synchronous control of the of vertical position of two hydraulic cylinders,and the vertical loading force to the wheelset when loading vertical load to the wheelset, which the hydraulic loading system is studied for the test-bed.At first, the loading principle of loading system is analyzed for the calibration test bench.By comparing with a variety of synchronous control circuit design methods and combining with the function and requirements of the test bench, this paper designs the synchronous control circuit of the test-bed and defines the project of the synchronous control system and design of hardware system.Then, the mathematical model of each component in the loading system is established,and the block diagram and transfer function of the loading system are simplified. In order to facilitate the analysis, the wheel is considered as a rigid body, and a synchronous loading system model is established, which is based on the coupling relationship between the sliding friction force and the two hydraulic cylinders. Combined with the characteristics of the electro hydraulic servo loading system, in order to improve the control precision, such as nonlinear and time-varying characteristics, the problem of synchronous control is studied based on the fuzzy control theory and variable universe theory. Due to the low control precision caused by the restriction of the number of rules, the fuzzy PID control algorithm based on variable universe is designed to solve the fuzzy PID controller. And a control method based on thecombination of the equivalent control and the deviation coupling control can improve the synchronous capability of the double vertical cylinder during the loading process.Finally, simulation analysis and experimental verification demonstrate the effectiveness of the developed method. This paper analyzes the loading system by using the Simulink module in Matlab, and the system is controlled by the fuzzy PID control algorithm and variable universe fuzzy PID control algorithm. Test bench in the actual application of the loading requirements is simulated. The position and force synchronization control is simulated respectively. The correctness of variable universe fuzzy PID control algorithm is verified, and the rationality of the design of synchronous control circuit is proved. The calibration test for the instrumented wheelset of subway train is carried out by using designed wheel-set calibration test bed, the line test is carried out by using the calibrated wheel-set, the effectiveness and the promising application effect of the method is achieved. |
