一种新型2T2R并联机构及其运动学分析

摘要

在4-UPU并联机构中，增加一条PPs支链，得到一种新型4．UPU／PPs并联机构，其中UPU支链为驱动支链，PPS为恰约束从动支链。利用修正的Kutzbach—Griibler公式计算该机构的自由度，并根据对各支链的分析，表明该机构具有2个转动自由度和2个移动自由度。以一组位姿参数作为初值，在给定输入的条件下，利用变步长Runge-Kutta-Felhberg算法求解运动平台位置变化过程，在此基础上，应用一阶和二阶差分方法分别计算运动平台的速度和加速度，结果与实际相符。%Based on the parallel mechanism of 4-UPU and by means of adding a PPS-limp, a novel spatial parallel mechanism of 4-UPU/PPS is built where the UPU-limp is regarded as the driver and the PPS-limp is the driven. The degree of freedom （DOF） of this mechanism is caculated by revised Kutzbach-Grubler formula. Each limp is analyzed, and the result demonstrates that this mechanism possessse two-translational DOFs and two-rotational DOFs. Given the input, one of the positional and orientational parameters as the initial value is used to caculate the position variation with time for the motion platform by Runge-Kutta-Felhberg algorithm, and then the result of posi- tion variation with time is used to calculate the speed and acceleration by the method of first order difference and second order difference. The result of kinematics analysis is in agreement with actual conditions.