In this paper, we propose a couple of configurations for development of an electro hydrostatic actuator (EHA). The study shows that both configurations result in the same dynamic model, and that the resulting dynamic model is equivalent to the dynamic model of flexible joint robots (FJR). Consequently, in controlling the EHA-based robots, we can apply a control strategy that is developed for flexible joint robots (FJR). In particular, we applied a position-based PD control with inertia reshaping technique, which is one of the most widely used control method for compliant interaction with environments. The proposed scheme was verified through experiments using a 1 degree-of-freedom testbed for both configurations of EHA.