Shape memory alloy and electrostatic brake hybrid actuator system for energy-efficient actuation strategies

This work presents a novel actuator system consisting of a combination of shape memory alloy (SMA) wires with electrostatic clutches. The proposed combination of smart material systems stems from the need to reduce the energy consumption of SMA based actuators while leveraging their high energy densities in compact actuation systems. To this end, large actuation forces provided by SMA wires are combined with the highly energy-efficient actuation of electrostatic clutches. The actuation of the SMA wire generates the desired motion after which the activation of the clutch and deactivation of the SMA wire ensures that the desired position is held in an energyefficient manner. A retractable electro-adhesive tubular clutch was chosen for our testing due to its enclosed nature and ease of fabrication. A characterization setup is also developed and used to demonstrate the feasibility of our new actuator concept. The tests show that a 254 μm SMA wire has an energy consumption rate of about 850.7 mJs⁻¹ as compared to less than 31.3 mJs⁻¹ for the clutch, which results in an energy savings rate of over 800 mJs⁻¹ for position holding tasks.