Safety is critical in robotic tasks. Energy function based methods have been introduced to address the problem. To ensure safety in the presence of control limits, we need to design an energy function that results in persistently feasible safe control at all system states. However, designing such an energy function for high-dimensional nonlinear systems remains challenging. Considering the fact that there are redundant dynamics in high dimensional systems with respect to the safety specifications, this paper proposes a novel approach called abstract safe control. We propose a system abstraction method that enables the design of energy functions on a low-dimensional model. Then we can synthesize the energy function with respect to the low-dimensional model to ensure persistent feasibility. The resulting safe controller can be directly transferred to other systems with the same abstraction, e.g., when a robot arm holds different tools. The proposed approach is demonstrated on a 7-DoF robot arm (14 states) both in simulation and real-world. Our method always finds feasible control and achieves zero safety violations in 500 trials on 5 different systems.
翻译:安全对于机器人任务至关重要。基于能量函数的方法已被引入来解决这个问题。为了在控制限制的情况下保证安全,我们需要设计一个能量函数,该函数在所有系统状态下都能产生持续可行的安全控制。然而,针对高维非线性系统设计这样的能量函数仍然具有挑战性。考虑到高维系统中存在着相对于安全规范的冗余动态,本文提出了一种名为抽象安全控制的新方法。我们提出了一种系统抽象方法,使得能够在低维模型上设计能量函数。然后,我们可以根据低维模型综合出能量函数以确保持续可行性。结果得到的安全控制器可以直接转移到具有相同抽象的其他系统中,例如当一个机械臂握着不同的工具时。所提出的方法在模拟和实际世界中都在一个 7 自由度(14 个状态)的机械臂上进行了演示。在5个不同的系统上的 500 次试验中,我们的方法总是找到可行的控制,并实现零安全违规。