Switched fuzzy-PD control of contact forces in robotic micromanipulation of Drosophila larvae

Force sensing and control are of paramount importance in robotic micromanipulation. A contact force regulator capable of accurately applying mechanical stimuli to a live Drosophila larva could greatly facilitate mechanobiology research on Drosophila and may eventually lead to novel discoveries in mechanotransduction of neuron circuitry. In this paper, we present a novel contact force scheme implemented in an automated Drosophila larvae micromanipulation system, featuring a switched fuzzy-PD controller and a noise-insensitive extended high gain observer. The switched fuzzy-PD controller inherits the fast convergence from fuzzy controller and overcomes the drawbacks (overshoot and oscillation) of a conventional fuzzy controller. The observer provides precise estimation to compensate for system modeling errors despite force measurement noise, which overcomes the disadvantage of traditional high gain observer. Force control experiments show that, compared to an conventional PID controller, this new controller-observer scheme has significantly enhanced dynamic performance in terms of rising time, overshoot, and oscillation. The developed robotic system and the force control scheme will be applied to mechanical stimulation and fluorescence imaging of Drosophila larvae for identifying new mechanotransduction mechanisms.