基于质点-弹簧系统的柔性线缆建模及其运动仿真

Modeling and Progression Simulation of Flexible Cables Based on Mass-Spring System

针对虚拟环境下柔性线缆在拾取和牵引等操作过程中的运动仿真问题,提出了一种基于质点-弹簧系统的仿真方法。首先建立线缆的质点-弹簧模型,同时采用显示欧拉法建立模型的运动控制方程,通过分析线缆受力情况,求取对质点位置更新起关键作用的合力,其间采用虚拟耦合技术将输入设备的空间位置信息转化为作用在线缆上的操作力,解决了操作力的模拟问题;通过对线缆几何模型施加变形率约束,给出了操作力沿线缆传播的计算方法。然后,根据材料力学和机械振动理论,建立刚度系数和阻尼系数的计算模型。最后,在此基础上,提出了基于OpenGL的线缆动态绘制算法并进行了仿真实验。实验结果表明采用所提方法进行线缆仿真能够很好地模拟线缆长度保持特性和抗弯性能,线缆运动的物理规律能够得到真实体现,仿真的线缆具有很强的真实感。

An algorithm based on mass-spring system was proposed to simulate the progression of flexible cables during grasping or pulling and so on in virtual environment. Firstly, the mass-spring model of cable was constructed and its motion control equations were given according to explicit Euler method. With the analysis of forces applied on each particle, the gross force, which was critical to update the position of particles dynamically, was evaluated. Virtual coupling technique, which transformed the displacement of input device into force, was employed to simulate the operation force. Ratio constraint of deformation was applied to animate the force propagation along the cable. Secondly, based on mechanics of material and mechanical vibration theory, the selection principle of parameters in the model, such as stiffness and damp, was proposed. Finally, a dynamical rendering algorithm based on OpenGL was proposed and implemented for virtual cable. The proposed method was verified in simulation experiment. The result shows that the length conservation and bend properties can be realized effectively, which gives a realistic expression of physics principles during the moving of cable, and the simulated cable gets a high reality.