Full state feedback (FSF) controllers for series elastic actuators bridge the gap between impedance and admittance controllers. For humanoid robots—which must stably accomplish both stiff and soft behaviors—FSF controllers are ideal candidate joint controllers. However, previous work on FSF gain tuning has used a nonlinear passivity analysis which does not account for time delay and can result in unstable behavior. In this article, we introduce a phase-based frequency domain approach to limiting these gains. This strategy can guarantee phase-relaxed passivity according to a relaxation parameter—an a priori bound on the regenerative efficiency of springs appearing in the environment. A simple demonstration illustrates how relaxed phase passivity behaves differently than strict passivity in how it handles the load inertia, allowing stiffness beyond the passive limit.

中文翻译：

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串联弹性执行器的相位松弛无源全状态反馈增益限制

串联弹性执行器的全状态反馈（FSF）控制器弥合了阻抗和导纳控制器之间的差距。对于必须稳定完成硬性行为和软性行为的类人机器人，FSF控制器是理想的候选关节控制器。但是，以前在FSF增益调整方面的工作使用了非线性无源分析，该分析不考虑时间延迟，并且可能导致不稳定的行为。在本文中，我们介绍了一种基于相位的频域方法来限制这些增益。该策略可以根据松弛参数（a）来保证相位松弛的无源性。先验限制了环境中出现的弹簧的再生效率。一个简单的演示说明了松弛相无源性在处理负载惯性方面的行为与严格无源性有何不同，从而使刚度超过了无源极限。