SERA Actuator/Belleville Worm, Second Iteration

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Whiteboard sketch of the redesigned actuator.

The team then attempted to alleviate the problems with the spur gear train by moving the motor inline with the worm axle and using a coupler for torsional stiffness while allowing for axial motion. This coupler was an especially difficult problem as it needed to be very efficient and could not introduce hysteresis to the system.

Another debate going on during this design period was whether to use a particular small motor or a larger, slower motor. The decision made was to use the larger motor so that the worm shaft could be attached directly to it rather than requiring spur gears to reduce the speed and increase the torque. However, this created problems with bearings and bushings as bushings could not handle the rotary speed and bearings would have difficulty with axial translation due to the elastic element. These problems drove the team to the flexure-based design.

A paper sketch of the later design which led to the flexure-based design

The "Clock" shaped actuator which kept the spur gear design but was eventually abandoned for the.