This article offers a new insight to the achievable stiffness limitation of the impedance control of series elastic actuators (SEAs) by suggesting a comparative analysis of energy ports and passivity control framework at the energy port to enhance the maximum achievable rendered stiffness of SEAs. To this end, it is explored that SEAs have two different port definitions to assess energy and passivity of the system - spring port and load port; and conservatisms for passivity evaluation of two ports are investigated and compared utilizing frequency characteristics. The results reveal that the load port passivity exhibits less conservatism, which allows to render larger achievable stiffness in impedance-controlled SEAs. Moreover, key parameters that determine the passivity characteristic of the SEA impedance control are discovered based on the load port passivity analysis. A novel passivity control framework that incorporates the time-domain passivity observer and the passivity controller is designed utilizing the load port energy monitoring, which offers a less conservative assessment of the systems passivity. Throughout this novel port passivity analysis and the passivity control, it can be achieved to render maximum rendered stiffness of the SEA impedance control much higher than the limitation that has been perceived as the maximum value.

中文翻译：

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基于负载侧阻尼分配的高刚度控制串联弹性执行器的无源控制器


本文通过对能量端口和能量端口处的无源控制框架进行比较分析来提高 SEA 的最大可实现呈现刚度，为串联弹性执行器 (SEA) 阻抗控制可实现的刚度限制提供了新的见解。为此，探索SEA有两种不同的端口定义来评估系统的能量和无源性——弹簧端口和负载端口；并利用频率特性对两个端口无源性评估的保守性进行了研究和比较。结果表明，负载端口无源性表现出较少的保守性，这允许在阻抗控制的 SEA 中提供更大的可实现刚度。此外，基于负载端口无源性分析，发现了决定SEA阻抗控制无源特性的关键参数。利用负载端口能量监控设计了一种新颖的无源控制框架，该框架结合了时域无源观测器和无源控制器，该框架提供了对系统无源性的不太保守的评估。通过这种新颖的端口无源性分析和无源性控制，可以实现使SEA阻抗控制的最大渲染刚度远高于被视为最大值的限制。