Doing More with Less: Weight-Optimised Electric Actuation Systems 2007-01-3830
Precision gear systems using Harmonic Drive gears are well-known for their reliability and high torque-to-weight ratio. A new series of gear improves these features further plus additional properties such as an increased hollow-shaft diameter.
Stiffness of the gear is a key element for the precision and zero-backlash features of the Harmonic Drive gear. A systematic analysis of the actuator elements and their impact on the overall transmission accuracy, performance and precision was carried out in order to identify where reduced cross sections with lower stiffness results in lower weight without compromising the performance characteristics of the gear.
The paper presents the approach and results of this analysis, including FE-modelling and deformation values under various loading conditions of the gear. As a result of this analysis, stiffness requirements for the mounting structure are defined.
In a next step, this approach is now widened up to the integration of the motor, including its bearings and housing structure.
The resulting product allows transmitting the same torque as the previous design with a weight benefit of 20 … 40%, depending on gear size. At the same time gear inertia was reduced by about 40%, allowing a higher dynamic response of the actuator.
The paper closes with a look into planned, future developments.