Mechanism Research Of 3-DOF Parallel Wave Energy Conversion Device

The application of parallel mechanism in the field of wave power generation has important theoretical research significance and engineering application value.At present,most of the oscillating float type wave energy conversion devices at home and abroad are single DOF(degree of freedom)motion.The wave energy conversion devices based on parallel mechanism or series parallel mechanism are rarely studied,and most of them are in the stage of configuration design or theoretical research.In this paper,3-DOF parallel mechanism with redundant branch chain and series parallel 3-DOF mechanism are proposed as wave energy conversion mechanism of wave power generation device,which can effectively solve the problems of complex structure and low energy conversion efficiency of wave energy device.This paper studies the configuration design,performance analysis,parameter optimization and prototype design of wave energy conversion device.The main research contents are as follows:Wave power generation equipment is overall planned and designed.The 3-DOF parallel mechanism is used as the energy acquisition and conversion mechanism of the wave energy conversion device.Based on kinematics and mechanical characteristics,22kinds of 3-DOF parallel mechanisms with two-dimensional rotation and one-dimensional motion are proposed by using the theory of G_F(Generalized function set).The evaluation index of the configuration of wave energy conversion device is proposed.The configuration evaluation of the synthesized mechanism is carried out,and the energy conversion mechanism of up-down opposite type and overhanging offset type wave energy device is designed.Kinematic analysis of the float of the wave energy conversion device is carried out.Based on Froude-Krylov theory,the wave force(torque)models of float with shape of vertical cylinders,cuboids and hemispheres are established.The coupled equations of heave and pitch motion of the float are built.The hydrodynamic coefficients are determined by the slice theory,and then the equations of motion are solved.The relationship between the energy collection efficiency of the float and the shape and size of the float is established.The shape and size parameters of the float are designed to provide the basis for the kinematic and dynamic analysis of the wave energy conversion device.A kind of up and down opposite wave energy conversion device based on3-RPS/3-SPS parallel mechanism is proposed,and the inverse solution analysis of position,velocity and acceleration of the device is carried out.The workspace of the mechanism is analyzed by using structural constraints.The kinematic model is verified by simulation.The force analysis of the up-down opposite wave energy device mechanism is carried out.The dynamic supplementary equation is established by using the coordination relationship between deformations of branch chain members under the stress state of the mechanism.Based on the D’Alembert principle,the inverse dynamic the mechanism is modeled.The branch force and joint force of the mechanism are solved.The correctness of the dynamic model is verified by simulation.A kind of extension offset type wave energy conversion device based on1-P_qU/3-RUS parallel mechanism is proposed,and a positional inverse solution model for the mechanism of the device is established.The working space of the float is determined using the boundary search method.The mapping relationship of velocity and acceleration between the branch chain and the end of the moving platform is established.The kinematics model is verified by simulation.The force analysis of the mechanism of the extended offset wave energy device is carried out.The dynamic supplementary equation is established by using the coordination relationship between deformations of branch chain members under the stress state of the mechanism.The inverse dynamic of the mechanism is modeled by Newton Euler method.The force acting on the swing rod at the end of the branch chain of the mechanism and the constraint reaction force of the kinematic pairs are solved.The correctness of the established dynamic model is verified by simulation.The effective workspace evaluation index,global kinematic performance evaluation index,output power index and constrained reaction force evaluation index of kinematic pair of the wave energy device are proposed.Based on the performance evaluation index,the normalized weighted sum method is used to realize the multi-objective structural parameter optimization design of the two kinds of wave energy devices.The structural parameters with better comprehensive performance of the two wave energy devices are determined respectively.By comparing and analyzing the wave energy device of 3-DOF with that of single DOF,the application situations of up-down opposite wave energy device and extended offset wave energy device are determined,and the advantages of3-DOF wave energy device in power generation capacity are verified.In order to meet the working conditions of different sea areas,an extended offset wave energy conversion device based on series parallel hybrid mechanism is redesigned.The Hooke hinge and 3-RUS mechanism in the float center are replaced by 5R parallel mechanism and connecting rod transmission mechanism,so that it has different motion performance.The kinematics and dynamics analysis of the improved extended offset wave energy device is carried out,and the correctness of the theoretical derivation is verified by simulation.The prototype of the up-down opposed wave energy device and the extended offset wave energy device are designed.The overall structure design and layout planning of the wave power generation device are carried out,and the experimental prototype of the extended offset wave energy device is developed.The research of this paper lays a theoretical foundation for the development and practical application of wave power generation device based on parallel mechanism,and is of great significance to expand the application field of wave power generation technology.