The linear-actuated parallel mechanism that changes the motion characteristic according to the actuator configuration is known. The authors previously (2000) reported on the kinematics and the motion characteristic on the basis of the motion transmissibility. In this report, we analyze the changed in motion characteristics using the measures of manipulability. Indices of manipulability are given with components of the value determined by the singular value decomposition. The typical index is a volume of the manipulability ellipsoid. We clarify the features of the motion characteristics according to a change in the actuator configuration using these indices. Finally, we show the recommended application examples that are designed for mechanisms using the obtained result.

Parallel mechanisms driven by fixed linear actuators promise high speed and high output, thanks to lightweight movable parts. Several types of mechanism applying this mechanical principle are already known. Although these have different methods of actuator arrangement, they may be considered the same mechanism since they can be treated using the same kinematics. However, it is not known how the output characteristics differ with differences in actuator arrangement. The article first shows the general kinematics that can be applied regardless of actuator arrangement. Next, changes are shown in the output characteristics occurring with changes in the actuator layout angle in a linear-actuated parallel mechanism with validity arranged actuators. The movable space and motion transmission indexes were used to determine the output characteristics. A total transmission index integrating the transmission index into the movable space is proposed, and the effects of design parameters other than actuator layout angle were investigated while giving weight to the motion transmissibility. The results show that the best actuator layout angle is 45-75 (deg).

Contact state information is indispensable for performing skillful tasks in which an end-effector should be in contact with the environment. In previous work, the authors introduced the concept of a pseudo contact point that is useful for tasks involving contact as one expression of the contact state. In this paper, an extended definition of the pseudo contact point is proposed. The pseudo contact point is defined as the foot of the perpendicular from the nearest point on a reference object to the line on which the contact point and external force vector lie. The system may estimate the contact state and its transitions by monitoring the pseudo contact point in spite of the fact that the pseudo contact point does not always denote the real contact point. Experimental results suggest the effectiveness of our method, which is particularly valuable in providing an intuitive positional description of a contact state.