Research On Performance Analysis And Control Strategy Of A Novel Redundant 6-DOF Parallel Mechanism

With the development of high speed railway,speeding up,intellectualizing,and light-weighting are mainstream trend.Vehicle body and components are working under much more severe conditions.High requirements are putting forward on stability,security,fatigue durability of vehicle bogie,vehicle body and other components.In this paper,Test Bench for Bogie Parameters(TBBP)was proposed and mainly used for dynamic simulation of train running on the line and high precision measurement for both dynamics and structural mechanics parameters of vehicle body and bogie.Therefore,the research focuses on kinematic characteristics and kinematics control,dynamic characteristics and its control strategy,calibration of platform measurement system.The content mostly covers the following aspects:1)Kinematic analysis of redundant 6-DOF parallel mechanism.Based on mechanism topology theory,the degrees of integer cycle freedom,coupling,and redundancy are analyzed.Mathematical model of forward and inverse kinematics are thus established.Three innovative algorithms for forward kinematics are proposed,including intelligent algorithm based on L-M algorithm improved BP neural network algorithm and Genetic algorithm optimized BP neural network algorithm;Numerical iteration method based on signaling processing decoupling theory;Fusion algorithm consist of geometric analysis method based on linearized decoupling and Higher order iterative method for forward kinematics.By use of the TBBP,the test for measuring pose of vehicle end adjacent and for measuring bogie rotational resistance parameters are taken as examples for testifying the effectiveness of the three innovative algorithms.2)Dynamics modeling and performance analysis of redundant 6-DOF parallel mechanism.Based on second Lagrange Equation,dynamic models of platform and hydraulic servo system are established.The cause of coupling internal force and its characteristics in redundancy driving system are also analyzed.Hypermesh Software is used for meshing the mechanism.Modal analysis and high-frequency vibration analysis of the mesh model are carried out by using ANSYS software.These analysis results provide theory basis for structure optimization of construction.ADAMS-Simulink-AMESim co-simulation model is then built for providing a model base for the following control strategy design.3)Research on servo control strategy of redundant 6-DOF parallel mechanism.Five-order transfer function of electro-hydraulic servo system is developed.Reduct the transfer function from five-order to three-order by optimal approximation to the dominant energy method.Set the three-order transfer function as controlled object,TVC feedforward and feedback control,TVC optimized fuzzy adaptive PID control(TVC-FPID)and TVC optimized H infinite robust control(TVC-ROB)are proposed.The three controllers are compared in system bandwidth characteristic,tracking performance and control energy.4)Research on vibration coordinated control strategy based on workspace.Three types of large closed loop of Parallel mechanism's end effector are proposed,including 6-DOF outer loop control strategy based on workspace,Inner loop TVC optimization based H-infinite robust control strategy,6-DOF inner-outer loop vibration coordination large closed loop control strategy.H infinite loop-shaping method control strategy based on Terminal high-order sliding mode control rate for 6-DOF outer loop control is proposed.This control strategy is combined Nonlinear Terminal high-order sliding mode controller possessing high tracking accuracy,rapid convergence speed and lower steady-state error with robust controller possessing strong disturbance resistance.The ideal trend and amplitude frequency gain of system frequency characteristic can be devised through weight functions1 W,2W and 3W designed by loop-shaping method.This control strategy can solve high-order sliding mode's buffeting and noise vulnerable problem and also promote the tracking ability of robust control.System performance is thus elevated.Aiming at decoupling internal force of redundant mechanism,the dynamic pressure equilibrium control strategy is presented.Simulation results further prove the effectiveness of the control strategy.5)Portable 6-DOF platform pose measurement system and its calibration device scheme are proposed.Firstly,build inverse and forward kinematics model by ADAMS and MATLAB/Simulink,respectively.Secondly,the calibration scheme can be realized for single-DOF and also multi-DOF under various-frequency,and various-amplitude condition during calibration process.6 knobs of calibrator can be adjusted simultaneously or separately and adjusted order will not matter.Dynamic and static kinematic calibration device of measurement system can be thus finished and owns a great generality.Lastly,both design of monitoring system and software development of measurement and control system is realized based on MATLAB/GUI.Practicability,effectiveness and progressiveness are the guiding ideology of this paper during the research.In the basis of analysis of kinematics and dynamics of Redundant 6-DOF Parallel Mechanism,a series control methods are proposed to improve the high-precision of mechanism motion and to further consummate the control strategy of redundant parallel mechanism.