Shared Control methods often use impedance control to track target poses in a robotic manipulator. The guidance behavior of such controllers is shaped by the used stiffness gains, which can be varying over time to achieve an adaptive guiding. When multiple target poses are tracked at the same time with varying importance, the corresponding output wrenches have to be arbitrated with weightings changing over time. In this work, we study the stabilization of both variable stiffness in impedance control as well as the arbitration of different controllers through a scaled addition of their output wrenches, reformulating both into a holistic framework. We identify passivity violations in the closed loop system and provide methods to passivate the system. The resulting approach can be used to stabilize standard impedance controllers, allowing for the development of novel and flexible shared control methods. We do not constrain the design of stiffness matrices or arbitration factors; both can be matrix-valued including off-diagonal elements and change arbitrarily over time. The proposed methods are furthermore validated in simulation as well as in real robot experiments on different systems, proving their effectiveness and showcasing different behaviors which can be utilized depending on the requirements of the shared control approach.

翻译：共享控制方法常采用阻抗控制来跟踪机器人操作臂的目标位姿。此类控制器的引导行为由所使用的刚度增益决定，而刚度增益可随时间变化以实现自适应引导。当同时跟踪多个具有不同重要性的目标位姿时，对应的输出力/力矩必须通过随时间变化的权重进行仲裁。本研究将阻抗控制中的变刚度稳定性问题与不同控制器输出力/力矩按比例相加的仲裁问题统一纳入整体框架进行分析。我们识别了闭环系统中的无源性违反问题，并提出了系统无源化方法。所得方法可稳定标准阻抗控制器，为开发新型灵活共享控制方法奠定基础。本方法不约束刚度矩阵或仲裁因子的设计——两者均可包含非对角元素的矩阵形式，且可任意时变。所提方法通过多系统仿真与真实机器人实验验证，证明了其有效性，并展示了可根据共享控制方法需求利用的不同行为特性。