Feedback Control-Based Navigation of a Flying Insect-Machine Hybrid Robot.

This study reports the first ever demonstration of the aero navigation of a free-flying insect based on feedback control. Instead of imitating the complicated kinetics and mechanisms of insect locomotion, a live insect can be directly transformed into a soft robot by embedding it with artificial devices. Since many insects can perform acrobatics aerially, thereby exhibiting far greater flexibility than current man-made flyers, correctly commanding the internal structures of an insect to perform based on the instructions would be a breakthrough. Herein, beetles (Mecynorrhina torquata) were chosen as the flying platform, and an inertial measurement unit-implemented electronic backpack was designed and manufactured to remotely command the beetles. To achieve horizontal flight control, multiple flight muscles of the beetles, that is, the basalar and third axillary muscles were stimulated to control the flight directions. However, the beetles were found to gradually adapt to the electrical stimulation, and the flight corrections were elicited by generating compensatory flight forces during a long-lasting stimulation (>300 ms), which were revealed by the decrease in induced lateral force. Based on this finding, a proportional derivative feedback controller was designed to navigate the flying beetles based on the predetermined path using frequency-dependent electrical pulses. To avoid a continuous stimulation, we proposed a stimulation protocol which separated two stimulations with a 50-ms rest. Compared to long stimulations (>300 ms), a 150-ms stimulation with 200-ms update interval was more efficient in correcting the flight direction of the beetles.