| Because of the high stiffness, strong bearing capacity, small inert ia and no error cumulative, parallel mechanism has been applied in many areas, such as motion simulation, parallel machine tool, micro- motion parallel mechanism and robot manipulator., and the performance of which has an important effect on the progress of relevant industry, and can be considered as the important symbol of the technical level for the country. As a consequence, it’s of great significance to study parallel mechanism.The study of this paper is based on the planar paralle l mechanism consisted of the horizontal actuators and the platform of hydraulic vibration table. C onsidering the poor effic iency of hydraulic servo system composed of valve and cylinder, structural parameter-optimization of the mechanism has been studied. The transformation relation of force and that of motion between freedom space and joint space have been derived, and on the base of which, mathematical model and constraint condition of optimization problem aimed at minimum total power of hydraulic driving system have been established. The condition must be satisfied for planar parallel mechanism to achieve minimum total power of hydraulic driving system under the hypothesis with the analys is based on genetic algorithm. Contrastive Analysis of some important properties between optimal structure and the classical orthogonal structure has certified the effectiveness and feasibility of the method proposed.Dynamic model of planar parallel mechanism has been established with the method of Lagrange. Dynamic calculation of the optima l structure has been conducted, the contrast between which and the simulation result of adams has certified the correctness of the dynamic model. The vibration equation of system has been derived based on the dynamic model considering the hydraulic cylinder as hydraulic spring. Dynamics coupling caused by eccentric load has been discussed. Theoretical modal analysis of system composed by mechanism and eccentric load has been conducted, and the modal matrix and modal Parameter are obtained. The mapping relation between physical space and mode space has been established, which can be used to solve the problem of coupling in physical space with the method based on mode space.The control strategy of planar parallel mechanism w ith eccentric load has been studies to solve the problem of dynamics coupling and coupling among degree of freedom channels and to find the condit ion to realize decoupling among those channels. Considering the weighted orthogonality of principal mode about mass matrix and stiffness matrix, mo dal coordinate transformation can be conducted to convert coupling dynamical equation in physical space to decoupling dynamical equation in mode space. Transfer function matrix of the system with modal coordinate transformation can be analyze to find the conclus ion that consistency of dynamic characteristics in each modal channel is one of the suffic ient conditions to achieve decoupling among each degree of freedom channel. Dynamic characteristics in each modal channel can be adjusted independently to meet the sufficient condition. Simulation analys is in time domain and frequency domain can be conducted to certify the correctness of the suffic ient condition to achieve decoupling among each degree of freedom channel. |
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