Closed-Loop Control of a Magnetic Particle at the Air-Liquid Interface

One of the greatest challenges in microrobotics is the development of robotic devices for high-speed transportation and precise positioning of microcomponents. This paper proposes to use non contact magnetic actuation in which objects are placed at the air/liquid interface and are actuated through magnetic field gradients. A physical model is developed and identified to perform closed-loop control. This approach is validated through several experiments in 1-D. Precise positioning and high-speed trajectory tracking of objects smaller than 100 m are achieved. The position error of an object of 60 50 25 m is less than 10% of its size and the maximum velocity reached is about 6 mm/. The closed-loop control has been tested on objects as small as 30 20 25 m and demonstrates its ability to perform precise positioning (the position error is less than 7% of the size of the object). This approach represents a promising solution to design devices for high throughput transportation and precise positioning of micro-objects, which will lead to magnetic smart surfaces at micrometer scale. Note to Practitioners-This paper was motivated by the problem of the adhesion effects on the control of objects at the microscale. The micro-objects behave differently in ambient environments and in liquids. In ambient environments the micro-objects can reach high velocities since the viscous forces are negligible, however the adhesion forces limit the repeatability of the motion. In liquid medium, the issues of the adhesion effect decrease, but the velocity is limited due to the viscous forces. This paper suggests a noncontact approach where micro-objects are placed at the air-liquid interface and are controlled by magnetic forces. In this paper, we have demonstrated, by using a closed-loop control, a high speed and precise actuation of micro-objects along one axis (1-D). The position error of an object of 60x 50 x 25 mu m(3) is less than 10% of its size and the maximum velocity reached is about 6 mm/s. In addition, objects smaller than 50 mu m can be controlled (the position error of an object of 30x 20 x 25 mu m(3) is less than 7% of its size). This approach avoids the issues of the adhesion effects and represents a promising solution for high speed transportation and precise positioning of objects. In future research, a strategy of control will be developed for high speed/precise control of objects in 2-D. These developments will directly contribute to the design of magnetic smart surfaces at micrometer scale that will convey microcomponents. It represents a key element of future assembly lines at micrometer scale.