Specific Kinematic Changes in a Linear-Actuated Parallel Mechanism According to Differences in Actuator Arrangement

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 present report 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 radially arranged actuators. The moving range and motion transmission index 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.).