| This dissertation presents mechanical design techniques of improving the performance of robot manipulators. Although measures of robot performance for conventional applications--such as payload, dynamic response, accuracy, economy and reliability--are considered, this research is especially concerned with the behavior of robots in unstructured environments. In such a setting, the total system mass, the energy efficiency, and the ability of a manipulator arm to interact positively with its surroundings are also important. Included here are three methods of overcoming performance limitations.;Gravity-induced joint torques can seriously degrade manipulator performance. A method of passive and energy-conservative mechanical gravity compensation is developed which can be applied to a wide range of manipulator geometries, two examples of which are presented. Experimental verification of compensation performance for one- and two-link implementations is reported, which shows the method to be accurate to well within one percent, and to be stable under a wide range of dynamic and static loading conditions. This approach to gravity compensation is also economical and easily applied.;Another method is a means of modifying the transmission characteristics of a robot manipulator to improve the predictability of actuator response. This is accomplished by optimizing the transmitted inertia matrix relating actuator inputs to joint outputs. Included is an application of this technique to a two-joint planar manipulator. Also discussed are methods of regenerating the energy expended in accelerating members to reduce energy consumption.;Finally, a new robot arm design is presented as an example of the use of mechanical design ideas to improve the performance of robot manipulators. The design is a demonstration of the benefits of applying these research results: in comparison to an advanced conventional arm, the new design uses less than a tenth as much energy, has better dynamic and static performance, and has lower mass and inertia. |
