A Linkage Design for Direct-Drive Robot Arms

A new approach to manipulator link mechanism design is presented. Given torque-speed characteristics of actuators and an arm link mechanism, the resultant force-speed characteristics at the tip of the arm arc analyzed. The link mechanism is optimized so that the end point speed and force are within appropriate ranges. This method is applied to a two-degree-of-freedom direct-drive arm. Direct-drive arms, in general, tend to have excessively fast operating ranges, whereas output forces are extremely small. A closed-loop five-bar-link mechanism is applied to the direct-drive arm, and the link dimensions arc optimized in order to acheive appropriate force and speed ranges at the arm tip without using reducers.