一种用于无人驾驶汽车运动模拟的3自由度并联机构动力学建模

Dynamic Modeling of a Three Degrees of Freedom Parallel Manipulator for Motion Simulation of Unmanned Vehicle

针对无人驾驶汽车半物理仿真试验对运动模拟系统精度要求高的特点,给出一种以3-RPS并联机构为基础的改进型3自由度并联机构。与3-RPS并联机构相比,由于该改进型并联机构中的被动约束承受了3-RPS并联机构中驱动器所承受的沿其转轴方向的力,因而改善了驱动器的力学特性。根据该并联机构的结构,建立运动学方程。基于Newton-Euler方法建立动平台的动力学方程。根据力矩平衡原理分别计算出同时垂直于驱动器及其转轴的分力以及同时垂直于被动约束上部及其转轴的分力。依照功率守恒原理计算出沿被动约束上部的力。驱动器的驱动力以及被动约束沿转轴的力即可求出。此计算方法对少自由度并联机构的动力学求解有借鉴意义。

During the semi-physical simulation experiment of unmanned vehicle,taking into account the features of high precision requirement to motion simulation system,a modified three degrees of freedom parallel manipulator based on the 3-RPS parallel manipulator is proposed.In comparison with the 3-RPS parallel manipulator,because the forces along the spinning shafts of the actuators in 3-RPS parallel manipulator are undertaken by the passive constraints of the modified parallel manipulator,the mechanical properties of the actuators are improved.The kinematic equations are established according to the structure of this parallel manipulator.The dynamic equations of the moving platform are formulated based on the Newton-Euler method.In the light of the principle of moment equilibrium,a force which is perpendicular to the actuator and its spinning shaft is worked out,and a force which is perpendicular to the upper part of the passive constraint and its spinning shaft is also worked out.According to the principle of power balance,a force along the upper part of the passive constraint is calculated.The driving forces of the actuators and the forces along the spinning shafts of the passive constraints can be obtained finally.This calculation method sheds light on dynamics calculation of lower mobility parallel manipulators.