Magnetic Suspension Using Variable Flux Path Control Mechanism with Permanent Magnet (Simultaneous Suspension Experiment of Two Iron Balls)

et al. 2017

Parallel magnetic suspension has been proposed which levitates multiple floators with a single power amplifier. This study applies this concept to a multi-degree-of-freedom system. In such systems, multiple electromagnets are used to stabilize multi-degree-of-freedom motions of the floator. In conventional system, each electromagnet is driven by the corresponding power amplifier. In contrast, multiple electromagnets are driven by a single power amplifier simultaneously in the case of parallel magnetic suspension. This study shows the feasibility of multi-degree-of-freedom control with a single power amplifier. First, the controllability of two-degree-of-freedom system controlled by parallel magnetic suspension is discussed. Second, an experimental apparatus is fabricated in which the vertical translational motion and the rotational motion around a horizontal axis are controlled by two pairs of electromagnets operated in a differential mode. Third, stable levitation is achieved in the apparatus. In addition, the dynamic characteristics are evaluated based on step response and frequency response with respect to external force. It is observed that the two suspended points vibrate in common phase with respect to the disturbance in a low-frequency region.

Realization of two-degree-of-freedom motions control using parallel magnetic suspension

et al. 2017

Basic characteristics of a parallel magnetic suspension system controlling two-degree-of-freedom motions

et al. 2018

A basic single-degree-of-freedom magnetic suspension system consists of one floator, one electromagnet and one amplifier. For multi-degrees-of-freedom control, multiple electromagnets and multiple amplifiers are necessary, which increases the cost of total system. As a means of overcoming this problem, parallel magnetic suspension has been proposed which controls multiple floators or multi-degree-of-freedom motions with a single power amplifier. In this system, all of the suspended points move simultaneously even when a disturbance acts on one of the suspended points solely because all electromagnet's coils are connected. This paper studies the moving direction of each suspended point with respect to a step disturbance in double parallel magnetic suspension system. The analytical study shows that the response direction is determined by the system parameter that relates the response speed of each subsystem. In the slower subsystem, the suspended point moves in the same direction as the applied force while in the faster subsystem, the suspended point moves in the opposite direction. In other words, the slower subsystem has positive stiffness while the faster system has negative stiffness. To confirm this prediction, step responses are measured in the experimental apparatus.

Zero-power control of double parallel magnetic suspension system with parallel connected coils

et al. 2014

Parallel magnetic suspension has been proposed where multiple floators are controlled with a single power amplifier. The feasibility of voltage-controlled double parallel magnetic suspension with parallel connected coils has been already demonstrated in the previous work. This study focuses on the zero-power control in a voltage-controlled double parallel suspension system with parallel connected coils. In this system, there are three methods of achieving zero-power control: feeding back the control voltage, either or the sum of the coil currents. This paper shows the conditions for the system with each zero-power controller to be controllable, and compares their performances.