| Aiming at the technical problems of the existing hydraulic support test-bed,this thesis carries out integrated innovative design including type synthesis,performance analysis,dimensional optimization and structural design based on the hybrid hydraulic support test-bed.The output degree of freedom(DOF)of the test-bed is determined according to the procedure latest revised of hydraulic support test,and the three-DOF parallel mechanisms with one movement and two rotations(1T2R)is used as the loading actuator device of the test-bed,and then connected in series with the threetranslational(3T)kinematic chain to construct the 5-DOF hybrid mechanism body configuration of the new hydraulic support test bench.Focusing on the object of the asymmetric UPS-RPU-PU parallel mechanism used as loading actuator device of the test-bed,this thesis carries out following study including configuration analysis,kinematics modeling,performance evaluation,and dimensional multi-objective optimization.By performance comparison of multiple sets of typical multi-objective optimization results with empirical design mechanisms,the optimal dimensional parameters,used to design the virtual prototype of the hybrid test-bed,is ultimately selected.Finally,the ZF9200/24/50 D hydraulic support is taken as the engineering test object,and the simulation analysis of the test-bed under various working conditions is carried out on the Ansys Workbench virtual environment to verify whether the stiffness and strength of the test-bed are both qualified.The research results aforementioned can provide a theoretical basis for further development of the physical prototype of the parallel mechanism and field loading test.The specific research contents are as follows.Firstly,the study on type synthesis of parallel mechanism applied in external loading test of hydraulic support is carried out in this thesis.Combined with the latest procedure of support loading test and relevant enterprise standards,the expected DOF of the loading actuator device of the novel hydraulic support test-bed is determined.Utilizing the position and orientation characteristic set,this thesis conducts the mathematical set relationship between the DOF of parallel mechanism platform and the end motion of each kinematic branch chain.On this basis,the topology design method of the parallel mechanism based on the equivalent hybrid kinematic chain is proposed.Therefore,a variety of 1T2 R parallel mechanisms with planar closed-loop structure and partial motion input-output decoupled characteristic are obtained,which can provide multiple references for configuration design of test-bed loading device.Secondly,the kinematics of a novel asymmetry UPS-RPU-PU parallel mechanism is analyzed.According to the analogical selection principle of mechanism configuration similarity and test-bed function correlation,an asymmetric UPS-RPU-PU parallel mechanism is proposed,and its kinematics theoretical modeling and simulation verification are carried out.First of all,use the single open chain theory to carry out configuration analysis,and the results demonstrates that the output DOF of moving platform is 1T2 R,and the coupling degree is zero.Then,based on the closed vector method,the analytical forward and inverse solutions mathematical model is derived,and the corresponding symbolic position solutions are obtained through numerical example.Furthermore,the analytical velocity and acceleration equations of this mechanism are derived,and the Jacobian matrix and Hessian matrix representing the velocity and acceleration mapping relationship between the driving joint and the output motion parameters of the moving platform are established,respectively.Finally,the correctness of the established kinematics models are verified by Matlab numerical calculation and Adams motion simulation.In addition,based on the Jacobian matrix of the mechanism,the motion singularity of this mechanism is further investigated.Thirdly,the performance analysis and the optimal configuration selection of parallel loading mechanism are further carried out.Using screw theory as mathematical tool,this thesis establishes the numerical calculation model of evaluating the motion/force transfer performance of asymmetric UPS-RPU-PU mechanism is established.The output axis of end-effector is designed offset,and the functional relationship is established between Euler and orientation angles by using azimuth and title angles to describe the orientation of output axis.On this basis,the definition and calculation method of effective transmission orientation workspace,regular effective transmission orientation workspace and orientation capacity are given.Based on this,the mathematical models of the global transmission index and the transmission fluctuation index are established by using discrete-analytic principle,and finally an integrated evaluation system which can demonstrate the overall performance of the mechanism is formed.Through this evaluation system,the performance indices of UPS-RPU-PU mechanism with the empirical size is analyzed,the numerical solutions of each performance index and performance map are obtained.Moreover,to select high-quality configurations for hydraulic support loading test,this thesis further selects two semi-symmetric 1T2 R parallel mechanisms,2PUS-PU and 2RPU-RPS,and uses aforementioned performance evaluation system to compare the performance of the three mechanisms.Then,the research on the multi-objective optimization of dimensional parameters of UPS-RPU-PU parallel mechanism and the corresponding solving algorithms are carried out.Based on the functional requirements of support loading test,the expensive constrained multi-objective optimization model of dimensional parameters of this mechanism is established,which comprehensively considers performance indices including orientation capability,global motion/force transmissibility,transmission fluctuation,and constraint conditions such as avoiding rod interference,coordinating rod length,and range motion of kinematic joints.This thesis uses the differential evolution operator to replace the genetic operation in the traditional NSGA-II,and incorporates the constraint processing technology,thus forming the constrained multiobjective optimization algorithm,called NSDE-II.Therefore,NSDE-II is applied to solve this multi-objective optimization problem,and then there are multiple sets of Pareto alternative solutions being obtained,which can provide multiple schemes for designing the virtual prototype of novel hydraulic support test-bed.Subsequently,a comparative test on computation performance of four MOEAs used to solve this multi-objective dimensional synthesis model is carried out to verify the feasibility and effectiveness of NSDE-II.That is,three classical algorithms NSGAII,MOEA/D-GA and MOEA/D-DE are applied to solve the multi-objective optimization implementation of UPS-RPU-PU mechanism,and the corresponding results of the four algorithms are compared one by one.For engineering optimization problem,this thesis further propose a performance index,named as the average value of the adjacent minimum vector angle,which can describe the diversity of the Pareto solutions set.On this basis,the comprehensive performance evaluation and comparison for the four multi-objective evolutionary algorithms are carried out by combining the degree of mutual coverage,the normalized coverage space and the computational time.Finally,typical multiple Pareto optimal(or near-optimal)solutions are selected to compare results with the mechanism designed under empirical dimension parameters,thus selecting out a set of dimension parameters with the optimal comprehensive performance.The virtual prototype of the “3T+1T2R” serial-parallel hybrid type hydraulic support test-bed is designed by using the optimal dimensional parameters.Then the ZF9200/24/50 D hydraulic support is selected as the engineering test object,and the simulation and analysis for loading test of the hybrid test-bed based on virtual prototype in the Ansys Workbench,and the corresponding results demonstrate that the bearing capability and workspace of this test-bed can meet the loading test requirements of most hydraulic supports in the market,which also provides theoretical guidance for the subsequent physical prototype development and the field loading test of hydraulic support.The dissertation has 72 figures,19 tables and 187 references. |
PDF Full Text Request