Design, Simulation and Experiment of a Novel Mass Detection System with Active Control Magnetic

It is presented in this paper an active magnetic levitation system used for the nanogram detection in biomedical domain. The design, simulation and levitation experiment are presented in detail. The device is composed of three parts: planar coil electro magnetic (EM) as lower stator, permanent magnetic (PM) as rotor and capacitance plate as lower stator. The levitation force versus displacement is analyzed by Ansys software and the air damping coefficient is also calculated. A dynamic model of levitation control is build to select control parameter and explain the experimental measurement. The stiffness versus frequency is analyzed. Experimental results of initial levitation, square wave response and sine wave sweep frequency response are presented and discussed. Preliminary measurements indicate that the response time for initial levitation is 0.2s, and the control current is 0.17A when the levitation height is 1mm. The quick-response performance is in agreement with the dynamic simulation by Matlab/Simulink. From sweep frequency experiment, it can be seen that when the levitation height is 1mm, the resonant frequency is 27.34Hz. The relationship between minimum detectable mass and frequency has been got. At last, the prospective MEMS design is proposed, which is applicable for the cancer cell weight detection.