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.
Research Interests
Research on Human-friendly motion control; Development of human assistance;rehabilitation system; Design of robotic system based on human musculoskeletal system; Analysis of human walking dynamics and its application to robotics; 친인간적인 운동제어 설계연구; 인간 보조;재활 시스템의 설계 및 개발연구; 인간 근골격계에 기초한 로봇기구 개발연구; 보행운동 분석과 모델 및 로봇기구에의 응용