Rotating the heading angle of underactuated flapping-wing flyers by wriggle-steering

The Harvard Robobee is a fly-sized aerial vehicle that can perform controlled flight maneuvers. But this robot is unable to control its yaw or heading angle to a desired value. Motivated by this deficiency, we propose a new method to produce yaw-axis rotations. Termed wriggle-steering, it consists of driving body oscillations around its two other rotational axes. Because no torque is applied directly around the controlled axis, it therefore constitutes an alternative control method for under-actuated designs. Oscillations are driven around pitch and roll axes at the same frequency but 90 degrees out of phase, resulting in a small change in yaw angle after each cycle because of nonlinearity in attitude dynamics. We propose two wing kinematics perturbations that produce the necessary actuation. The predictions are validated with a quasi-steady aerodynamics model, free-body simulations, and flight tests on a fly-sized hovering aerial robot. The results suggest that wriggle-steering can save mass and reduce complexity by eliminating the need for additional actuators in flapping-wing robots or other aircraft.