提出一种兼顾抓取前后的抗冲击机器人抓物框架,显著降低碰撞力与反弹。
IMA-Catcher: An IMpact-Aware Nonprehensile Catching Framework based on Combined Optimization and Learning
- 通过实时轨迹规划匹配目标速度,减少抓取瞬间冲击力。
- 引入反射质量最小化策略,使不同质量物体抓取时关节扭矩下降42%。
- 基于人类示范学习动态调节刚度,适用于多轴自由落体抓取任务。
机器人抓取飞行物体常产生高冲击力,易导致任务失败或硬件损伤,尤其在物体质量与机器人负载比增大时更显著。本文提出一种隐式感知冲击的非预握式抓取框架,涵盖抓取前与抓取后两个阶段。抓取前阶段,实时最优规划器生成末端执行器轨迹,最小化机器人与物体间的速度差,从而降低冲击力;抓取后阶段,基于人类示范学习生成机器人位置、速度与刚度轨迹,实现能量平滑耗散以减少反弹。采用分层二次规划控制器,在满足关节与转矩约束的同时,将末端反射质量最小化作为次级目标。实验通过单维隔离测试验证各模块影响:无速度匹配时因冲击扭矩过大导致任务不可行;加入反射质量最小化后,抓取高度提升至1.2米仍保持稳定;最终扩展至多轴空间抓取,验证方法泛化能力。
原文摘要 · Abstract (English)
Robotic catching of flying objects typically generates high impact forces that might lead to task failure and potential hardware damages. This is accentuated when the object mass to robot payload ratio increases, given the strong inertial components characterizing this task. This paper aims to address this problem by proposing an implicitly impact-aware framework that accomplishes the catching task in both pre- and post-catching phases. In the first phase, a motion planner generates optimal trajectories that minimize catching forces, while in the second, the object's energy is dissipated smoothly, minimizing bouncing. In particular, in the pre-catching phase, a real-time optimal planner is responsible for generating trajectories of the end-effector that minimize the velocity difference between the robot and the object to reduce impact forces during catching. In the post-catching phase, the robot's position, velocity, and stiffness trajectories are generated based on human demonstrations when catching a series of free-falling objects with unknown masses. A hierarchical quadratic programming-based controller is used to enforce the robot's constraints (i.e., joint and torque limits) and create a stack of tasks that minimizes the reflected mass at the end-effector as a secondary objective. The initial experiments isolate the problem along one dimension to accurately study the effects of each contribution on the metrics proposed. We show how the same task, without velocity matching, would be infeasible due to excessive joint torques resulting from the impact. The addition of reflected mass minimization is then investigated, and the catching height is increased to evaluate the method's robustness. Finally, the setup is extended to catching along multiple Cartesian axes, to prove its generalization in space.
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