New multi-d.o.f. haptic device using a parallel mechanism with a wide rotational working area

A parallel mechanism is a multi-legged kinematic structure with actuators fixed on the base. In recent years, parallel mechanisms have been implemented in haptic devices due to their benefits, such as high rigidity, high output force, high accuracy and high backdrivability. Multi-d.o.f. haptic devices with rotational motion have become increasingly important as haptic applications have become diversified (e.g., in surgical training). However, typical multi-d.o.f. parallel mechanisms (e.g., Stewart platform and HEXA) have limitations on the working area for rotational motions. A multi-d.o.f. haptic device can be designed by stacking the translational and rotational mechanisms by decoupling these motions. However, this dedoupling can have an adverse effect on inertia because of the weight of the stacking mechanism. Eventually, the operability of the device deteriorates. Therefore, a parallel mechanism with both a translational and rotational multi-d.o.f. structure can effectively apply the full advantages of a parallel mechanism to a multi-d.o.f. haptic device. In this paper, a 6-d.o.f. (five active: three translations, two rotations and one passive rotation) parallel mechanism, called the D-8, is presented. In the D-8, a new redundant parallel mechanism is introduced to overcome the problem of operability.