Intentionally applying impacts while maintaining balance is challenging for legged robots. This study originated from observing experimental data of the humanoid robot HRP-4 intentionally hitting a wall with its right arm while standing on two feet. Strangely, violating the usual zero moment point balance criteria did not systematically result in a fall. To investigate this phenomenon, we propose the zero-step capture region for non-coplanar contacts, defined as the center of mass (CoM) velocity area, and validated it with push-recovery experiments employing the HRP-4 balancing on two non-coplanar contacts. To further enable on-purpose impacts, we compute the set of candidate post-impact CoM velocities accounting for frictional-impact dynamics in three dimensions, and restrict the entire set within the CoM velocity area to maintain balance with the sustained contacts during and after impacts. We illustrate the maximum contact velocity for various HRP-4 stances in simulation, indicating potential for integration into other task-space whole-body controllers or planners. This study is the first to address the challenging problem of applying an intentional impact with a kinematic-controlled humanoid robot on non-coplanar contacts.

翻译：有意识地在保持平衡的同时施加冲击，对腿式机器人而言极具挑战性。本研究起源于对双足站立的人形机器人HRP-4用右臂故意撞击墙壁这一实验数据的观察。奇怪的是，违反常规零力矩点平衡准则并未系统性地导致摔倒。为探究这一现象，我们提出了面向非共面接触的零步捕获区域，定义为质心速度区域，并通过采用HRP-4在两种非共面接触上保持平衡的推回复实验进行了验证。为进一步实现有目的的冲击，我们计算了考虑三维摩擦冲击动力学后的候选碰撞后质心速度集合，并将该完整集合限制在质心速度区域内，以在冲击过程中及冲击后通过持续接触维持平衡。我们通过仿真展示了HRP-4在不同站位下的最大接触速度，表明其具备集成到其他任务空间全身控制器或规划器中的潜力。本研究首次解决了运动学控制的人形机器人在非共面接触上施加有意冲击这一难题。