Robots mimicking the structure of the musculoskeletal systems have been de- veloped in order to realize high physical performance or to reveal the con- tribution of the musculoskeletal systems to body movements. The movement of center of rotation (CoR) of biological joints have been focused on in var- ious research fields. However, to date, the isolated contribution of the joint displaceable center of rotation (JDCR) on physical performance has not yet been analyzed. Revealing this contribution is expected to provide guidelines for the design methodology of robots. In this paper, we compared two mod- els in order to investigate the effect of JDCR on physical performance. The first model has two virtual links to represent the joint including the JDCR (JDCR model). The second model represents the joint with fixed CoR (JFCR model). We evaluated the two models by analyzing energy consumption during reaching motions. In addition, we examined energy consumption while the end effector traced a circular trajectory using extended models (eJDCR model and eJFCR model). The results showed that the energy consumption of models which include JDCR lower than models which does not under all tested con- ditions. This study suggested that a joint including JDCR can improve energy consumption.
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