Design and Validation of a Fully Mechanical Torque-Boosting Elastic Actuator with Passive Energy Harvesting and a Load-Triggered Release

Abstract

Applications where peak loads appear every so often would highly benefit from actuators of which the torque can be boosted by an elastic element like a spring. This paper provides a design and validation of a fully mechanical torqueboosting elastic actuator that can accumulate energy within its springs, and release this energy in the form of an additional torque once it senses that the output torque coming from the motor is insufficient. A prototype was manufactured and its performance was validated by measuring the input and output torques during the loading of the springs and the releasing of the energy. Releasing the energy from the springs increased the output torque with 44.7% (from 159Nmm to 230Nmm). However, it was measured that the efficiency of the mechanism averaged around 19.4%, meaning that, even after a torque boost, the mechanism loses torque overall. Nevertheless, the mechanism could accumulate energy, put this energy aside by decoupling itself from the main driveshaft, sense a deficiency of output torque, and release the stored energy in the form of a torque. Therefore, all functional requirements were met. Further research should prove to what extend the performance based criteria can be reached by improving the efficiency of the design.