Design of a Reconfigurable Robot Arm for Assembly Operations inside an Aircraft Wing-Box

We present a design concept and two initial prototypes of a robot arm for assembly operations inside an aircraft wing-box. The wing-box has a large span, but is only accessible through multiple small portholes along its length. The arm is compact enough to enter the wing-box through the small portholes and is capable of subsequent reconfiguration so as to access a number of assembly points inside the wing-box. Traditional electromechanical actuators are unsuitable for our purpose, because of limited space and large payload requirements. We use an actuator module comprising Shape Memory Alloy (SMA) wires, which are known for their high stress to volume ratio. Our design also addresses the issue of limited strain of SMA wires through a displacement amplification mechanism. Our compact, high displacement actuator module can be readily integrated into the structure of the robot arm. We also discuss a deployment scheme for the robot arm, which eliminates gravity loading during the reconfiguration phase, and also helps to position the end effecter at the various assembly points inside the wing-box.