Robust linear control of a bending molecular artificial muscle based on spin crossover molecules

Bending actuators represent a popular class of artificial muscles for which efficient closed-loop control is remarkable challenge, due to the complexity physico-chemical phenomena occurring during dynamic contraction. In this study, we investigate an electro-thermally actuated, bilayer bending actuator based on spin crossover molecules. While these can open-loop contract in several tens seconds, show that simple PID-control able reduce response time ca. 1.5 s, even with loads up 5 times weight (i.e. maximal load about 343 mg). We demonstrate also satisfactory sine wave tracking performance. The relevance linear approach applied nonlinear consequence high sensibility current, responsible Joule effect. Notably, roughly behaves like second-order system, whose “constants” decrease current. Consequently, natural speed improvement peculiar PID-controller further amplified by effect, without any loss stability system.