A shape memory alloy actuated robotic arm for aerial manipulation

Aerial manipulation is an important field of robotics with wide-ranging applications in maintenance, construction, and inspection. However, complex aerial manipulation tasks are often limited to large drones due to the high mass of existing robotic arms, a large potion of which is contained within its actuators. Shape memory alloy (SMA) actuators provide a lightweight alternative to actuate a robotic arm, but have seen little use due to the lack of a robotic arm with suitable strength and range. The strength of existing SMA-actuated arms cannot easily be increased, as increasing the number or size of the actuators drastically increases complexity. This paper addresses these limitations by developing a lightweight, 3-DOF robotic arm actuated by shape memory alloy wires capable of achieving aerial manipulation tasks. Topology optimization was applied to arm links to reduce mass. The resulting arm is capable of exerting over 25 times the torque of existing SMA-actuated arms. Control is achieved using an adaptive proportional-integral (PI) controller, the performance of which was experimentally measured through a series of step responses and path following tasks. The controller was found to be effective in manipulating masses of up to 300 g, roughly three quarters the mass of the arm itself.