Self-Sensing Control of Highly Efficient Self-Bearing Motor for Artificial Heart

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Application of self-bearing motor as an actuator for an artificial heart was considered. When it is applied to an artificial heart actuator, miniaturization of the system, high efficiency, low power consumption and low heat generation is required. Moreover, the sinusoidal flux distribution between the rotor and the stator is also preferable to suppress dogging torque and realize stable levitation control Self-bearing motor is an active control system, which requires a certain type of sensor. Therefore, self-sensing is very important technique to realize miniaturization of the system.This project proposed self-sensing control technique based on the principle of differential transformer to the interior permanent magnet (IPM) type self-bearing motor. Main flux (d-axis) directional permeance is different from its orthogonal (q-axis) directional one because of the salient pole property in the IPM type motor. When the IPM type rotor rotates, the mutual inductance between the driving coil and … More the control coil varies with not only radial displacement but also its rotation angle. It means that the radial direction displacement information is not detected simply from the mutual inductance independently.First, Magnetic field analysis using finite element method was done to analyze the allocation of the interior permanent magnets of the rotor. Prototype IPM self-bearing motor was designed and fabricated from the analyzed results.Secondary, new detection method using full-wave rectification was introduced to obtain the more stable differential output and new compensation was also proposed to linearize the nonlinear characteristics of the self-sensing signal.Finally, to confirm the proposed compensation method, an internal PM type active magnetic bearing was made and tested. The result showed no interference and linear characteristics in the static experiment and accomplished stable rotation control up to 6,000rpm.From these results, we confirmed that the proposed method has high possibility and feasibility for self-sensing control of the IPM type self-bearing motor. Now we plan to improve linearized compensation and apply to the IPM type self-bearing motor for development of the available actuator as an artificial heart. Less