Extended Data Fig. 4: Details of simulation and robophysical implementation of delayed stretch activation.
From: Bridging two insect flight modes in evolution, physiology and robophysics
a) Data from Fig. 2c replotted (black line is mean, shaded region is ±1 s.d., grey lines are individual traces. A two parameter model fit (r3 and r4) of phases 3 and 4 of the M. sexta delayed stretch activation response (Eq. 6). b) Diagram of the muscle block alone. Output is a weighted sum of asynchronous feedback and synchronous forcing, saturated such that it exerts force only in one direction. The sine generator has a phase, θ0, of 0 for the upstroke muscle and π for the downstroke muscle so that together the two muscles generate sinusoidal forcing. c) Block diagram of simulation of antagonistic muscles under both delayed stretch activation and synchronous forcing. d) Schematic of the robophysical experiment. A dynamically scaled wing is immersed in a large water tank and is actuated by a brushless motor under torque control. An angular encoder measures the wing rotation and the calculated wing velocity is supplied to a Simulink simulation of delayed stretch activation. The combined output of delayed stretch activation (Fasync) and the synchronous force (Fsync) is provided to the motor driver to actuate the wing. e) A photo of the experimental setup.
