Performance Analysis And Optimization Of Compliant 3-PRS Parallel Mechanism

With the rapid development of industrial technology and the continuous improvement of automation level,the compliant parallel mechanism plays an important role in the field of robotics by virtue of its characteristics of high precision and stable performance.On the basis of clarifying the difference between compliant and noncompliant mechanisms,the 3-PRS parallel mechanism is studied by the numerical method.In addition,the research on the operation precision of the compliant parallel mechanism is more in-depth.As a key factor affecting the accuracy of the compliant parallel mechanism,the flexure joint is of great significance to the practical application of the compliant parallel mechanism.Therefore,it is of far-reaching significance for the development and application of the compliant 3-PRS parallel mechanism to deeply study the elastic characteristics of flexure joints and improve the operation accuracy of the compliant 3-PRS parallel mechanism.The main contents are as follows:(1)Several elastic characteristics models of flexure joints are established.A threedimensional model of flexure joints are established,and the elastic characteristics of the joint are analyzed based on the finite element method.According to the proportional scaling model with 0.1～2 times scale factor,the effects of different sizes on joint elasticity are analyzed in order to find the best proportion of the model.Then,combined with the elastic characteristics of different notch profiles and the overall stiffness and working environment of the mechanism,Flexure joints used by the mechanism are identified.The dimensions of the compliant 3-PRS parallel mechanism are designed according to the different elastic characteristics of the joint notch shape.Finally,Euler-Bernoulli equation is used to establish a series of joint flexibility models,and the models are verified by finite element method,which lays a foundation for the construction of the compliant parallel mechanism.(2)A calculation method of equivalent rigid replacement is proposed.The drive stroke and the platform pose are fitted by regression,so as to realize the kinematics analysis and drive stroke optimization of the compliant parallel mechanism.The inverse kinematics of 3-PRS parallel mechanism is analyzed,and the joint pose of non-compliant mechanism is obtained.Then,the finite element model of the compliant 3-PRS parallel mechanism is established and the rotation of flexure joints is studied.the motion results of the equivalent non-compliant mechanism and the compliant mechanism are compared and analyzed.Finally,the relationship between the driving stroke and the posture of the moving platform is fitted by the method of multiple nonlinear regression,and then the driving stroke suitable for the compliant mechanism is obtained.The accuracy of the optimized model is verified by finite element analysis.The experimental results show that the simulation results of the optimized platform are closer to the preset values,which provides an important theoretical basis for the kinematics analysis and drive stroke optimization of the compliant 3-PRS parallel mechanism.(3)Based on the vector relationship between the joint and the long bar,the force model of each joint of the mechanism is established.According to the configuration of the compliant 3-PRS parallel mechanism,the rotation direction of the long rod and the position of the spherical joint and the revolute joint in the fixed coordinate system is analyzed.Then,the joint velocity and acceleration as well as the angular velocity and acceleration of the long rod are obtained by taking the derivative of the joint direction vector according to the position relation.According to the force balance equation,the driving force along the guide rail,the shear force between the driver and the slide rail,the support force provided by the slide rail to the driver perpendicular to the base and the force relationship between the spherical joint and the platform are investigated.Finally,based on the above research,the supporting forces of the spherical joint on the platform in three directions are obtained,and the forces of the actuator in three directions are solved by simulation,which provides a theoretical basis for the kinematic research of the compliant 3-PRS parallel mechanism.