| With the automobile driving on the road,the dynamic performance of the engine was affected by various road conditions.However,the conventional bench test differs greatly from the actual operating conditions of the automobile engine.Therefore,it was of great practical value to study the engine test equipment close to the actual road conditions.The road simulation platform based on parallel mechanism can reproduce the motion of engine in complex road conditions.In this paper,a 3-DOF redundant drive parallel simulation platform with a shear fork branch was designed.The main contents of this paper were as follows:Firstly,according to the actual engine operating conditions,a parallel simulation platform with continuous shaft and heavy load was synthesized.According to the motion index,the platform should be able to realize two-rotation and one-movement motion with relatively large stiffness and bearing capacity.Therefore,a three-degree-of-freedom redundant drive parallel mechanism 2UPS-2RPU-PU with two defined continuous shafts was firstly synthesized.In order to increase the carrying capacity,the PU branch was designed as a shear fork structure to obtain the final 2UPS-2RPU-PU* simulation platform.Then,the position of the simulation platform was analyzed,and the reachable workspace was obtained by platform constraints.The kinematics model of the platform was established based on vector method,and the velocity and acceleration of the platform were analyzed.The singular configuration of the platform was determined by analyzing the determinant of jacobian matrix,and the singular space was obtained.Thirdly,the kinematics model of the simulated platform was established,the velocity and acceleration of the mechanism were analyzed and verified.Based on the principle of virtual work,the dynamics of 2UPS-2RPU-PU* simplified mechanism was analyzed,and the driving force of the platform was optimized by using the least square method.The results show that the redundancy drive can significantly reduce the driving force of each branch and improve the bearing capacity of the simulation platform.Finally,the structural design of the components of the simulation platform and the selection of each component of the linear drive unit were carried out,and the finite element static analysis of some parts and the overall structure was carried out to ensure the rationality of the design. |
