Research On Nonlinear Control Of Test Platform Of Marine Component Mechanical Properties

With the rapid development of the shipbuilding industry,the detection of the ship component has been unable to meet the current situation in China. Therefore,it is imperative to meet the demand for testing a variety of marine component projects. In this paper,the test perform for mechanical property of the ship component is a kind of multifunctional tester,which is able to carry on many experiments such as tensile and stress testing,emergency towing and so on, whose control system is electro-hydraulic servo control system. In the process of modeling, most researchers neglected nonlinear factors in hydraulic servo system, so that the analysis of the control performance is not in line with the actual situation, so the study of nonlinear system control has very important theory meaning. Combining with the structural feature of test platform and considering the nonlinear factors, the mathematic model of hydraulic servo system in test platform is established and then the model is optimized. Simulating the mathematic model through Simulink modules in Matlab proves that the model has better control characteristics after optimization.The main contributions are as follows:(1) According to the structure of test platform, analyzing the properties of each part of the system is to establish the mathematic model of control system in test platform. But the electro-hydraulic servo system has obviously nonlinear factors,they are, the hydraulic valve of flow-pressure nonlinear and power mechanism of Saturation, loopback and friction. Using Taylor series linearization method to carry on the linearization of system models can obtain the transfer function of control system in test platform.(2) Since higher order term is neglected in the model process of conventional Taylor series linearization approximation, there is a certain deviation existed in the real control system. However, the feedback linearization method can reserve the message of control system more completely. Based on this, considering the nonlinear properties of the system, the paper establishes a precise nonlinear mathematic model of control systems to eliminate the influence of nonlinear elements in the system by means of using feedback linearization method to linearizate the nonlinear mathematic model and get the mathematic model after the state feedback exact linearization. Applying the theory of linear quadratic optimal control to design the controller for it, the optimal control rate is obtained.(3) The paper uses Matlab/Simulink to conduct the simulation of the whole control system. Simulating the moulds which contains the conventional mould,adding the PID controller mould, and exact feedback linearization mould, analyzing their control performance,the effects of system parameters on the control performance is studied. The simulation results show that the response time of the system is reduced by 0.1s, the overshoot is reduced by 3% in the control of state feedback exact linearization, and the system has good stability and tracking performance, finally through the marine emergency towing test verify the effectiveness and feasibility of the control system.