Design of a Parallel Haptic Device with Gravity Compensation by using its System Weight

This paper proposes a 6 degree of freedom (DoF) manipulator for haptic application. The proposed haptic device, named GHap, is designed based on the four-bar-linkage mechanism for linear motion with the ring-type gimbal mechanism. To improve the force display ability, the device is designed to compensate the gravity force of the manipulator by its own weight. The conceptual mechanical design is compared by placing the third joint, which controls the four-bar mechanism, in two different configurations. The forward kinematics and the jacobian of GHap are presented. Finally, the gravity compensation method and open-loop force display performance of the proposed haptic device are validated by an experiment with the GHap prototype.