Browsing by Author "Farrell, Logan C"

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    Efficiency of One- and Two-Stage Compact Cycloidal Transmissions for Robotic Applications
    (2018-03-30) Farrell, Logan C; O'Malley, Marcia K
    Many robotic applications demand compact, high reduction drives for their actuators. To date, the most commonly used actuator for this application is a harmonic drive. However, cycloidal drives could be considered for these applications as they provide high reductions in a compact package, are highly customizable, and can be easily manufactured in comparison to harmonic drives. Single-stage cycloids have been well analyzed in the literature, but not well tested. In this work, a single-stage cycloid was built and run for 300+ hours and 129,000 output revolutions to determine in-use efficiency and lifetime. This testing demonstrated that the compact, pin-in-housing designs can achieve efficiencies near and above the efficiencies of a comparable harmonic drive with a peak efficiency of 81% as well as a 2x increase in specific torque. A substantial burn-in of approximately 8 hours was noted, and the efficiency did not degrade appreciably over the course of the testing. A new design for a two-stage cycloid has been recently proposed and the basic kinematic analysis conducted. A test article for this two-stage design was constructed and tested. This testing identified gaps in the literature regarding the losses associated with the lobe to pin interactions. This work developed the mathematics necessary to characterize these losses in theory and are then compared to the tested actuator. The actuator’s losses nearly match the predicted losses of the two-stage system. This work presents many additional design equations for a two-stage cycloid system, the primary result suggesting that a two-stage system must be built with rolling elements in the housing to achieve satisfactory (above 50%) efficiencies. This thesis demonstrates enables two key conclusions: first single-stage cycloids are a viable replacement for harmonic drives in high reduction applications where backlash is allowed, second, additional design equations are necessary for a two-stage cycloid design.