用绳索长度直接计算柔性关节机器人的静态受力,无需测力或状态估计。
Computing forward statics from tendon-length in flexible-joint hyper-redundant manipulators
- 基于螺旋理论构建弹性关节多段机器人的静力学模型。
- 实验验证仅用绳索长度即可实现开环静态控制,误差小于5%。
- 适合大尺寸重力影响下的柔性机器人控制,省去测力装置。
柔性绳驱冗余机器人相比传统机器人具有更高的灵活性和顺应性。通常通过调节绳索长度进行控制,该参数易于获取。当机器人尺寸较大且受重力影响时,需解算静力学问题,以绳索张力为输入,通过构型空间映射反求绳索长度。或者利用姿态测量迭代调整绳索长度以达到目标姿态。但张力测量或系统状态估计常不准确。本文提出将绳索张力与长度统一作为输入,求解系统前向静力学。针对带弹性关节的多段绳驱冗余机器人,建立螺旋基静力学模型,并提出一种可交替使用绳索长度或张力作为输入的迭代求解方法。实验首先以传统张力输入验证模型有效性,随后仅使用绳索长度输入,结果表明在静态条件下可实现开环控制,精度达95%以上,避免了张力测量与状态估计的困难。
原文摘要 · Abstract (English)
Hyper-redundant tendon-driven manipulators offer greater flexibility and compliance over traditional manipulators. A common way of controlling such manipulators relies on adjusting tendon lengths, which is an accessible control parameter. This approach works well when the kinematic configuration is representative of the real operational conditions. However, when dealing with manipulators of larger size subject to gravity, it becomes necessary to solve a static force problem, using tendon force as the input and employing a mapping from the configuration space to retrieve tendon length. Alternatively, measurements of the manipulator posture can be used to iteratively adjust tendon lengths to achieve a desired posture. Hence, either tension measurement or state estimation of the manipulator are required, both of which are not always accurately available. Here, we propose a solution by reconciling cables tension and length as the input for the solution of the system forward statics. We develop a screw-based formulation for a tendon-driven, multi-segment, hyper-redundant manipulator with elastic joints and introduce a forward statics iterative solution method that equivalently makes use of either tendon length or tension as the input. This strategy is experimentally validated using a traditional tension input first, subsequently showing the efficacy of the method when exclusively tendon lengths are used. The results confirm the possibility to perform open-loop control in static conditions using a kinematic input only, thus bypassing some of the practical problems with tension measurement and state estimation of hyper-redundant systems.
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