Visual servo control of electromagnetic actuation for a family of microrobot devices

Microrobots have a number of potential applications for micromanipulation and assembly, but also offer challenges in power and control. This paper describes the control system for magnetically actuated microrobots operating at the interface between two immiscible fluids. The microrobots are 20 μm thick and approximately 100-200 μm in lateral dimension. Several different robot shapes are investigated. The robots and fluid are in a 20 × 20 mm vial placed at the center of four electromagnets Pulse width modulation of the electromagnet currents is used to control robot speed and direction, and a linear relationship between robot speed and duty cycle was observed, although the slope of that dependence varied with robot type and magnet. A proportional controller has been implemented and characterized. The steady-state error with this controller ranged from 6.4 to 12.8 pixels, or 90-180 μm.