Performances And Control Algorithm Study Of Electro-hydraulic Servo 6-DOF Stewart Platform

The electro-hydraulic servo 6-DOF Stewart platform is a simulated trial equipment on the mechanical environment,which adopts the typical Stewart mechanism,with the advantage of powerful carrying capacity,high stiffness and great accuracy,it has been widely applied in many areas,such as war industry,nuclear power and high speed rail.This dissertation will center on the performance of 6-DOF Stewart platform,and the research contents are as follows:In this dissertation,kinematics analysis of Stewart platform is carried out by coordinate transformation and matrix differentiation firstly,the model of inverse kinematics and a numerical method of the forward kinematics are deduced.Then using the Kane method,the single-rigid-body dynamic model of Stewart platform is established,and the simulation is carried out in Simulink and SimMechanics,which proves that the dynamic model is correct.The workspace and the singularity are important performance indicators of Stewart platform.For a given structure of Stewart platform,3D representation method for the reachable workspace is given and the singularity is checked to ensure structural safety.To design the low cost and energy conserving hydraulic power mechanism is one of the key point of electro-hydraulic servo 6-DOF Stewart platform.According to the functional requirements of Stewart platform,the hydraulic drive system is optimized.Then the hydraulic cylinder and servo-valve are designed based on the optimal load matching rules,and the flow of the hydraulic power units and the effective working volume of the accumulator are analyzed and calculated.Finally,with the analysis of the biggest function curve and natural frequency of Stewart platform,the rationality of the hydraulic system is verified.The last part of this work is focus on the control method of Stewart platform.Firstly,according to the interaction relationship between the hydraulic driving systems and mechanical system,the integrated dynamic model of system is established.With this integrated dynamic model,frequency responses of degrees of freedom are analyzed.Then,for the problem of waveform distortion,an amplitude-phase control method based on the Widrow-Hoff learning algorithm is employed to improve the platform's response for sinusoidal signals,and its validity is proved through experiments.