Magnetic suspension systems have shown a great deal of promise in the field of microrobotics. This paper discusses the performance of a new large gap magnetic suspension system developed by the researchers. The magnetic drive unit consists of six electromagnets attached to a soft iron pole piece and yoke. Levitation of an 11.19 g microrobot prototype is demonstrated for step, ramp and periodic input trajectories using PID control. The working envelope of the microrobot is 30 × 22 × 20 mm3, with an RMS error on the order of 18 µm in the vertical direction and 8 µm in the horizontal direction. It is demonstrated that the levitated microrobot is able to track the desired trajectory precisely and that the system has potential application for micromanipulation.
Micromanipulation is an emerging technology in such diverse areas as precision engineering, microfabrication, and microsurgery. Each of these areas impose certain technological constraints and requirements in fabrication, actuation, and control. This paper performs a review on the latest technologies of microrobotic actuation techniques and suggests a suitable technique for the actuation of a magnetically levitated microrobot. The microrobot, suspended in an externally produced magnetic field, consists of a gripper attached to a series of permanent magnets and is capable of simple pick and place tasks. A number of electromagnets produce the external magnetic field and three laser sensors feedback the position of the levitated microrobot. Through finite element analysis, performance of the levitation system was investigated, and simulations and experiments were carried out to demonstrate the practical capabilities of the proposed system.
Magnetically levitated microrobotic systems have shown a great deal of promise for micromanipulation and biomedical applications. This paper discusses the identification of the vertical and horizontal motion models for a large-gap magnetic suspension system developed by the authors. The suspension system consists of six electromagnets attached to a soft iron pole piece, which levitate a small microrobot prototype manufactured from a 10 mm × 10 mm cylindrical neodymium magnet. A modified least squares algorithm is used to identify ARMAX models describing the motion of the system. Due to the unstable nature of open loop vertical position control, the black-box open loop model is extracted from the identified closed loop model by examining the motion of the closed loop poles on a root locus diagram. The identified models are able to reasonably predict the system behaviour.
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