Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Electric motor actuators for robotic and automation systems often require a transmission (speed reducer) in order to operate within the speed-torque requirements of a specific application and of the motor. Commonly used systems include multi-stage gearboxes, timing belts, cables with capstans, harmonic drives, and cycloid gearboxes. These systems may have shortcomings, such as too inefficient, susceptible to overload damage, heavy, and require expensive precision manufacturing. Such systems are also often too expensive for consumer products when high performance is required.
As an example, harmonic drive systems can be used in high performance applications where low backlash and gear-ratios greater than 50:1 are required. The harmonic drive is proprietary, heavy, inefficient, susceptible to damage from shock load, and expensive for consumer application. As another example, cable drive systems can be lightweight and efficient; however, achieving useful transmission ratios may lead to complex multi-stage designs that require high preload forces, large cable bend radii, and challenging cable management. Often it is desired to integrate a torque sensor such as a strain gauge load cell at or near the output of the transmission in order to achieve closed loop torque control. Practically, such as a case on a rotating output hub, integration of this sensor can prove challenging as the sensor wires typically rotate with the transmission output, and therefore, require cable management, adding complexity and increasing the number of failure points.