A general purpose six degree-of-freedom haptic device is newly designed, which can be used as a general motion commander as well as a force reflector. The structure features the large workspace and easy analysis of a serial structure and the compactness and durability of a parallel structure at the same time. The study analyzed kinematics of the proposed device to obtain the optimal device parameters in terms of kinematics and derived dynamics to form a linear control system through the feedback. In calculating the optimal design factors of the haptic device in terms of kinematics, this study employed the global isotropy index. The proposed structure has high manipulability within the workspace, which is an essential factor for a motion generator. Also the study proposed a force controller featuring an inner nonlinear loop designed to compensate the nonlinear dynamics of the device and an outer linear control loop aimed to compensate un-modeled dynamics and disturbance. For an outer linear controller, the study adopted an LQG/LTR controller that can systematically take into account stability, robustness and frequency characteristics in the design process. The performance of the proposed device was verified with its efficiency through simulation and experiments.
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