Investigating the Effect of a Series Elastic Actuation Retrofit to Black-Box Actuators
This work provides a low-cost method to enhance force control in black-box actuators, benefiting robotics applications requiring compliance and precision.
The authors retrofitted a series elastic actuator (SEA) to a black-box actuator to improve force control. The SEA module increased open-loop force control bandwidth from 10.32 Hz to 30.32 Hz (2.93× improvement) and outperformed a commercial force sensor by 7.63% at a fraction of the cost.
In robotic applications, actuators are typically designed to be stiff with minimal backlash to ensure precision and repeatability. However, this limits compliance, leading to potential damage and poor force control in uncertain environments. Series Elastic Actuation (SEA) introduces compliance to enhance disturbance rejection and enable force measurement via Hooke's Law but reduces system bandwidth. A custom Series Elastic (SE) element was retrofitted to a black-box actuator to mitigate non-linearities like backlash and static friction. Integrating the SE element enabled high-fidelity force measurements, improving force control bandwidth and performance. A torsional SE element was designed through Finite Element (FE) analysis, yielding a stiffness of 2155.4 Nm/rad. Open-loop force control bandwidth was measured for the original motor and the SEA-integrated configuration, while closed-loop bandwidth was assessed using feedback from the SEA and a commercial force sensor. The SEA module increased bandwidth from 10.32 Hz to 30.32 Hz, a 2.93X improvement. Additionally, it outperformed the commercial sensor by 7.63% despite costing 25 GBP, a fraction of the price.