Research Of Force Loading Control Based On 6-Dof Motion Platform

With the rapid progress in speed railway, the requirment for test devices becomes higher. The comprehensive test-bed of hydraulic researched in this paper is based on 6-DOF parallel mechanism, which can stimulate the movement relationship between car-sides when the train is running, and can measure the whole inter-train stiffness and damping, and can test the coupler, through passage, electrical connector and the brake pipe. All of these provide basis for dynamic analysis and structural design of the train. When measuring parameters of the through passage,such as stiffness and damping , we need to study the force loading control based on 6-DOF motion platform.Firstly, this paper introduces the properties, development and application overview of parallel mechanism, and the research and key issues of force control as well. Then the paper analyzes the position and force loop dynamic characteristics of the single channel system, and discusses the coordinate transformation process of the force sensor value , analyzes the dynamic response of which is discussed when it is extended to 6-DOF motion platform. In the corresponding analysis, it applies a feasible control strategy, and designs an effective force controller.In the single channel system analysis, this paper establishes the mathematical model of the valve controlled singal-rod hydraulic cylinder power mechanism and the through passage firstly. Through simulation analysis, it obtains the frequency range and dynamic response characteristics of the system. When it analyzes the properties of force loading control, this paper applies the force control strategy inclusive position loop. Through force controller based on admittance control, the force error signal is converted to compensation signal of the internal position loop. Thus the loading force control is realized, and the frequency range of the force control system as well. Because of the time-varying parameters of the through passage in the force loading process, the paper studies the influence of the parameters changes on the dynamic response of the singal-channel system respectively.This thesis analyzes the measurement principle of force loading control based on 6-DOF motion platform, and studies the transformation process of the force sensor value from the sensor coodinate to the aided coordinate, in which the parameters of the through passage are computed. And the transformation relationship between them is getted. By the Euler angles discription of coordinate transformation, the solution process of the transformation relationship is given.Finally, in the singal degree of freedom force loading control analysis of 6-DOF motion platform with generalized output force closed-loop, it first improves the control strategy of the singal channel system, and add a dynamic presure feedback loop. Then for the sixl degree of freedom force loading control based on internal position loop, the paper analyzes the dynamic response characteristics of its force loop respectively and together.