A new approach for the design of robot joint transmission

Until recently the only alternative to traditional transmission techniques for robot manipulators was direct-drive (DD), and associated transmission mechanisms. These methodologies were developed to overcome the inherent problems of friction, backlash and compliance of gearboxes. The DD concept is however not ideal as the absence of a reduction ratio, means that dynamic coupling and joint interaction become important at the motor shaft. An alternative approach that keeps the directness of DD, while providing dynamic coupling and joint interaction attenuation, is the non-linear direct transmission. The new concept is applied to the prototype SPRINTA robot and its performance demonstrates the potential of the non-linear direct transmission philosophy.