考虑运动副摩擦时平面闭链五杆机构逆动力学分析

The Inverse Dynamics Problem of Closed Loop Five Bar Mechanism Considering Joints Friction

提出一种修正的指数摩擦模型,给出了摩擦系数与速度的关系式,避免了速度零点的多值问题,建立了机构运动副摩擦的数学模型。建立了包含运动副摩擦的平面闭链五杆机构的逆动力学模型,并给出了一种迭代求解方法,可得到运动副的约束力、驱动力和运动副摩擦力矩。在相同运动规律下,对计入和不计入运动副摩擦两种情形进行驱动力矩的比较。仿真结果表明:两种情形下的驱动力矩有较明显的差异,在速度反向区,运动副摩擦力矩的变化剧烈,对机构驱动力矩的影响最大,在机构运行速度较低时,这种现象更为明显。

The characteristic of joint friction in closed-loop mechanism was analyzed, and a mended exponential frictional model which could avoid detecting the point of zero velocity was put forward in this paper. The mathematic model of joint friction in closed-loop mechanism was described. The inverse dynamics model of a 5R closed-loop mechanism considering the joint friction was proposed. An iterative arithmetic was presented to solve the model, and joints force, joints friction moment and actuating moments were acquired. Results of simulation indicated that the joint friction had obvious influence about drive moments of the mechanism, and the effect deteriorated in the re- gion of relative velocity reversing direction.