Uncovering the mechanisms of wing damage compensation in insect flight using control theory and robophysics*

Flies maintain flight even after losing half of a single wing, a feat with no current analogue in robotics. Compensation is achieved through changes in the motion of the intact and damaged wing. However, the impact of wing damage on performance, and the neuromechanical strategies used to compensate for wing damage, are not well understood. By studying intact and injured flies inside a virtual reality arena, we quantified the impact of wing damage on gaze stabilization. Using system identification techniques, we found that wing damage subtly reduced flight performance. By combining flight data with a robophysical model, we discovered that damage compensation is driven by both active and passive mechanics. The robophysical model and flies exhibited a passive increase in wing amplitude and flapping frequency with increasing wing damage. However, flies decreased the amplitude of the intact wing and shifted the abdomen towards the intact wing, suggesting active control. Using control theory, we show that compensation to wing damage is achieved by active changes in internal gains that trade off stability and performance. Studying the response of flying insects to wing injury can inform the design of flapping-wing robots that maintain function following damage.