Vibration control of active electromagnetic levitation system with three-dimensional position estimation by current and magnetic flux

This paper describes the three-dimensional motion control of a magnetic levitated object in an active electromagnetic levitation conveyance system. Generally, the magnetic levitation conveyance system is useful when we convey products without qualitative degradation due to contact. However it is necessary to control the three-dimensional motion of the levitated object and it is difficult to measure the position. Therefore we propose how to estimate three-dimensional position without a position sensor. Four Hall elements are installed on the bottom of the electromagnet instead of the position sensor. A state observer estimates the three-dimensional position of the levitated object from the four Hall voltages and the current and the input voltage to the electromagnet. The three-dimensional motion controller uses a state-feedback control based on the estimated position. This controller has a large stability margin in order to compensate the modelization error. The validity of the proposed method is confirmed by experiment results.