Motion transmissibility of in-parallel actuated manipulators

When all input links except one are fixed in the mechanism of an in-parallel actuated manipulator with N degrees of freedom (dof), N kinds of mechanisms with a single dof can be obtained, and pressure angles corresponding to each mechanism can be defined. In order to transmit power efficiently from input links to the output link, all of the cosines of the pressure angles must be as large as possible. The present paper proposes a new transmission index (TI) for in-parallel actuated manipulators based on the power transmitted from input links to the output link, which is defined as the minimum value of cosines of the pressure angles. For planar and spatial in-parallel actuated manipulators, the effectiveness of TI is investigated considering static characteristics of mechanisms. Working spaces of in-parallel actuated manipulators obtained with consideration of motion transmissibility are also shown.