Extended Data Fig. 6: Electrical system for the precise control of the magnetically actuated robotic metamaterial.
a, Experimental setup consisting of a dc power source, a scalable power converter, and a set of copper coils. b, Modular power converter prototype comprising six individual power electronic building blocks. c, 3-D Helmholtz coil structure made of six circular-winding pairs; each pair consists of two windings connected in series. d, Scalable power-converter topology consisting of six full-bridge submodules to precisely control the current of each winding pair. e, System block diagram showing the closed loop current-control scheme; the winding currents are sensed locally in each submodule using shunt resistors. A proportional-integral controller is implemented on a microcontroller card resulting in an equivalent first order reference-to-winding current system. Each coil is modeled by an inductance value L and a resistance R representing the resistivity of the copper wire. The controller gains are selected as \({k}_{p}=L/{t}_{r}ln9\) and \({k}_{i}=R/{t}_{r}ln9\) to accomplish a 10% to 90% current rise time of tr = 1.5 ms. A pulse width modulator (PWM) employing a 10 kHz triangular carrier wave is used to generate the signals controlling the states of the individual power switches.
