Post-stroke robot-aided neurorehabilitation is an emerging research field, aiming to improve the intensity and the effectiveness of post-stroke rehabilitation protocols by using robotic technology and virtual reality. One classification that has been proposed for therapy robots is between exoskeletons and end-effector based machines. The latter are those devices whose interaction with the patient’s arm takes place at the end-effector level. This paper presents the design of two novel end-effector based robots for upper-limb rehabilitation, named Sophia-4 and Sophia-3. Although the devices are based on a common concept (the cable-drive actuation over a planar workspace), the latter differs from the former by the number of employed cables (4 and 3, respectively), and, by several design solutions, such as the introduction of a moving pulley-block to enhance workspace and a tilting table to better target the patient’s shoulder. Both mechanical and control system design are addressed and a comparison of performances is presented.

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A path-planning algorithm for encountered-type haptic devices that render multiple virtual objects in 3D space is proposed. To render multiple virtual objects with a single haptic device, the following two behaviors must be realized: (i) the device should move to the target object location in advance of the user’s hand so that the user can encounter it; (ii) otherwise, the device should keep away from the user’s hand, avoiding an unexpected collision. To realize such a consistent encounter, the user’s hand motion must be tracked. The proposed algorithm determines the device location based on the minimum distance problem between a point (the user’s hand) and a convex polyhedron constructed from the reference points of multiple objects. An automobile virtual control panel was constructed using an encountered-type haptic device in which the proposed path-planning algorithm was implemented. The validity of the proposed algorithm was confirmed and the required performances, such as the device speed and the accuracy of hand tracking were evaluated.

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The design of robotic orthoses focuses strongly on replicating kinematics of human limb. However, often sophisticated mechanisms which attempt at reproducing complex kinematics of human joints fails in adapting to geometrical variations of subjects sizes and eccentricities. One major that arises from this mismatching is an occurrence of hyperstaticity induced by the uncontrolled interaction forces. In this paper, we take the point of view of statics to investigate the force transmission problem, which is required for a fine force control. The main result of this study focuses on designing fixations between the orthosis and the human limb that provide additional degrees of freedom. The method involves two steps. Firstly, a set of possible solutions with respect to the isostaticity criterion is derived. Then, among these possible solutions, a set of design rules considering physiological aspects of transmitting forces to human limbs is used to select a preferred configuration. As an example, the method is applied to an existing 4 active DOF arm orthosis.

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This paper proposes a tendon driven system with antagonistic pairs of polyarticular tendons to simulate a variable stiffness of a human fingertip. The stiffness of a robot finger should be adjusted according to a situation that includes large position errors or collisions, because it tolerates errors of object positions and dimensions in assembly task and absorbs collision energy in hitting or catching task. The variable stiffness therefore contributes to stable grasping and dexterous manipulation. Besides, a stiffness of a human fingertip can be controlled by consciously contracting antagonist muscles when it does not contact anything such as in a preshaping phase. This study simplifies a tendon driven system of a human finger and then searches feasible parameter settings of the tendon driven system with antagonistic pairs of polyarticular tendons through numerical simulations. Finally it is experimentally confirmed that the proposed tendon driven system has similar stiffness to a human finger.

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