Comparison of Drivetrain Topologies for an Ankle Gait Cycle

Powered prosthesis actuation is a field where energy efficiency and mass are important characteristics. The motion requirements of high torque at low speed and low torque at high speed are difficult to effectively combine in a single electric motor. A possibility is to use an oversized direct-drive motor that can deliver the peak torque. However, this results in a heavy actuation system and low overall efficiency. A common practice is combining a smaller electric motor with a gear reduction system. In the literature, novel redundant electric actuation systems have been presented with or without locking mechanisms to mitigate this problem. In this work, we provide a comparison of multiple electrical actuation systems composed of electric motors, gear reduction systems and locking mechanisms. This is done using the gait cycle of a human ankle as a case study. An electric motor with a double stator and a single rotor combined with a gearbox shows the most promising overall results when taking energy loss, total mass and complexity of the system into account.

Automated summary

Powered prosthesis actuation is a challenging field that requires high energy efficiency and low mass. Combining high torque at low speed and low torque at high speed in a single electric motor is difficult. One possible solution is to use an oversized direct-drive motor, but this results in a heavy and inefficient system. A common practice is to combine a smaller electric motor with a gear reduction system. In this study, we compare multiple electrical actuation systems with different motor-gearbox combinations, and a double-stator, single-rotor electric motor with a gearbox shows the most promising overall performance.