Identifying External Contacts from Joint Torque Measurements on Serial Robotic Arms and Its Limitations
Identifying External Contacts from Joint Torque Measurements on Serial Robotic Arms and Its Limitations
复制标题
通过串行机械臂的关节扭矩测量识别外部接触及其局限性
DOI：
10.1109/icra48506.2021.9561761
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Jack Umenberger
中科院分区：
文献类型：
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作者：
Tao Pang;Jack Umenberger
检测和估计外部接触的能力对于机器人手臂在人类占据的非结构化环境中操作至关重要。然而，大多数机器人手臂没有配备足够的传感器来检测其整个身体上的接触。许多机器人手臂都有用于单个关节的扭矩传感器。通过定量分析，我们认为机器人表面上的两个不同接触很可能产生几乎相同的关节扭矩测量值。当这种情况发生时，可实现的最佳接触估计是一组可能的接触位置，所有这些位置都将再现测量的关节扭矩。通过结合拒绝抽样和梯度下降法，我们提出了一种接触估计方法，该方法能实时地找到非线性规划的所有局部最优解。此外，我们提出了一个积极的接触探索方法，伪造虚假的接触估计在一组局部最优的机器人的当前配置周围的小动作。所提出的方法突出的警告，接触估计，从只有联合扭矩，再加上已知的限制，这样的估计，建议一个更有能力的传感器可能需要强大的全身接触估计。
The ability to detect and estimate external contacts is essential for robot arms to operate in unstructured environments occupied by humans. However, most robot arms are not equipped with adequate sensors to detect contacts on their entire body. What many robot arms do have is torque sensors for individual joints. Through a quantitative analysis, we argue that it is fairly likely for two distinct contacts on the robot’s surface to generate almost identical joint torque measurements. When this happens, the best contact estimate achievable is the set of possible contact positions, all of which would reproduce the measured joint torque. Searching for elements of this set is equivalent to solving to global optimality a nonlinear program.By combining rejection sampling with gradient descent, we propose a contact estimation method which in practice finds all local optima of the nonlinear program at real-time rates. In addition, we propose an active contact exploration method which falsifies spurious contact estimates in the set of local optima by making small motions around the robot’s current configuration. The proposed methods highlight the caveats of contact estimation from only joint torque, which, coupled with known limitations of such estimators, suggest that a more capable sensor is probably needed for robust whole-body contact estimation.