| Rail grinding is an effective method to rail through the removal of metal from the surface of the rail head by using high speed rotating grinding wheel, which can obviously prolong rail’s service life, reduce rail maintenance coasts, lower noise and improve train’s riding stability. Nowadays, pneumatic technology is widely operated in compressive loading system on rail-grinding train thanks for its increasing development. Complexity of operating environment during rail-grinding and non-linear nature of pneumatic system, however, brings significant difficulty for power control. Besides, it will also considerably weaken the actual grinding ability of the train. In the paper, the author considered the rail-grinding train with pneumatic loading drive as the study object, and proposed a pneumatic pressure control system based on chamber adjusting technology, including the system structure, the acquirement to the feedback signal and the control strategy. To be more specific, it could be described as follow.After having a quick review and analysis of recent power control strategy used in rail-grinding train, the power fluctuation model for rail grinding was build based on power control theory. And then the factors answering the power fluctuation were found through analysis of disturbance transfer law, and the author introduced an effective scheme to improve power control. On the one hand, the chamber adjuster was designed to improve the anti-perturbation capability of the system by adjusting the volume of its chamber indirectly. On the other hand, a controller of controlling of cylinder’s two sides’output pressure was established to stabilize output loading force. Simulation verified the accuracy and effectiveness of the proposed scheme.A varying parameters pneumatic structure was presented based on the given improvement plan of system structure. The basic idea of the structure is realize the non-rod cavity volume of cylinder expanded by setting a chamber adjuster which is made up by air tank and proportional flow valve connect with non-rod cavity. In order to deal with the strongly nonlinear relationship between controlled and output in chamber adjuster system, a disturbance compensation and feedback linearization controller is founded. The coupling of tank pressure and control parameter is solved well by the control strategy, and it made a good performance in realize cavity volume expanded. In order to solve the problem of proportional valve control limit, a control strategy about tank pressure is proposed, which adjust the air tank pressure to make chamber adjuster works better. Simulation results show the above mentioned make chamber adjuster performance good.Mathematical model of the chamber adjuster with varying control parameters was established. High accuracy of the model was proved by contrast experiment. On the basis of this, a study on how to acquire the feedback signal was conducted. According to the current features and filtering requirements, a new filtering algorithm which based on kalman filtering is proposed. The filtering algorithm uses mean square error of innovation sequence correct the filter factor. The simulations reveal that the method have a quickly rate of convergence, and could get good filtering result. Meanwhile, a novel state observer with forced perturbation was build. Firstly, the unpredictable perturbations were looked as new state items to void the uncertain cycle in the system. Then, in order to getting real two sides’pressure of the cylinder, a new state observer fitting new system was established. Finally, the simulation proved that.According to the strong nonlinearity, multi-control object and stochastic disturbance of the varying parameters pneumatic structure, an overall control strategy of varying parameters pneumatic system is studied and proposed, which based on the improvement scheme for system control strategy mentioned above. On the one hand, the strategy can improve system disturbance resisting ability by designing a multiple closed-loop control, combined with the cylinder cavity pressure obtained from the state observer. On the other hand, the strategy realizes the accurate control for each target controlled of it, which based on the sliding mode varying structure control, and combined with some advanced control theories like the auto disturbance rejection control technology and adaptive control. This paper designs three set of simulation experiment contrast items under many kinds of disturbed environment, and the results show that the overall control strategy of varying parameters pneumatic structure has obvious advantages in the stability and accuracy.With the help of the rail-grinding test-bed, pneumatic circuit for the loading part was updated according to the given pneumatic circuit with varying parameters. After the correction of the model parameters, the result of the experiment showed the actual reaction fit the model reaction. In addition, the contrast grinding experiments were conducted by grinding rail surface under different power control schemes. The result indicated that the rail-grinding power control strategy, which was based on the novel pneumatic circuit with varying parameters, has the significant advantages both in disturbance resisting and accuracy control. Besides, the designed filter and state observer also has excellent perform. |
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