A Robust Time-Stepping Scheme for Quasistatic Rigid Multibody Systems
A Robust Time-Stepping Scheme for Quasistatic Rigid Multibody Systems
复制标题
准静态刚性多体系统的鲁棒时间步进方案
DOI：
10.1109/iros.2018.8594378
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Russ Tedrake
中科院分区：
文献类型：
--
作者：
Tao Pang;Russ Tedrake
一个有效的方案来模拟低速，接触丰富的操作任务是假设准静态物理和先进的系统状态，通过解决线性互补问题（LCP）。然而，现有的基于LCP的准静态时间步进计划未能模拟抓取操作中的一个基本运动原语，由于两个缺点特定的准静态系统。首先，准静态系统的输入是速度指令而不是转矩。当两个接触的刚性体被命令相互推压时，这可能导致穿透，从而导致不可行的LCP。其次，由于给定速度命令存在多个力解，因此不能保证抓取速度命令能够产生足够的抓取力。在本文中，我们将准静态时间步进格式转化为一个具有互补约束和二次目标的优化问题。通过最小化实际速度和命令速度之间的差异，线性化的非穿透约束总是可以满足的。此外，可以通过考虑弹性来去除法向力不足的不期望的解决方案，弹性通过比较实际速度和命令速度来建模。由此产生的优化问题是一个混合整数二次规划，可以合理地快速解决中小型系统。不同复杂度系统的仿真结果验证了所提方法的有效性。
An effective scheme to simulate low-speed, contact-rich manipulation tasks is to assume quasistatic physics and advance system states by solving linear complementarity problems (LCPs). However, the existing LCP-based quasistatic time-stepping scheme fails to simulate grasping-an essential motion primitive in manipulation-due to two drawbacks specific to quasistatic systems. Firstly, inputs to quasistatic systems are velocity commands instead of torques. This can lead to penetration, and thus an infeasible LCP, when two rigid bodies in contact are commanded to push against each other. Secondly, as multiple force solutions exist for a given velocity command, a grasping velocity command is not guaranteed to generate sufficient grasping forces. In this paper, we reformulate the quasistatic time-stepping scheme as an optimization problem with complementarity constraints and a quadratic objective. By minimizing the difference between actual and commanded velocities, linearized non-penetration constraints can always be satisfied. Moreover, undesirable solutions with insufficient normal forces can be removed by considering elasticity, which is modeled by comparing actual and commanded velocities. The resulting optimization problem is a mixed-integer quadratic program, which can be solved reasonably quickly for small-to-medium-sized systems. The effectiveness of the proposed reformulation is validated by simulation results of systems with different levels of complexity.
DOI：
10.15607/rss.2017.xiii.040
发表时间：
2017-05
期刊：
ArXiv
影响因子：
--
作者：
Jiaji Zhou;J. Bagnell;M. T. Mason
通讯作者：
Jiaji Zhou;J. Bagnell;M. T. Mason