Extension of measurement bandwidth in an AMB-based gyroscopic sensor

A gyroscopic sensor using active magnetic bearing (AMB) is studied both theoretically and experimentally. The sensor has been proposed to realize high accuracy, compact and low-cost sensors, and it utilizes the control function of the AMB. The sensor works as a two-axis gyroscopic sensor and also as a three-axis servo-type accelerometer. Angular velocities and accelerations are measured based on the control signals for cancelling the inertial effects that act on the AMB rotor. The methods to detect the accelerations and angular velocities have been validated from several experimental results. In addition, it has been indicated that there is an upper limit in the measurement bandwidth of the sensor when the two-axis angular velocity is measured simultaneously. However, factors determining the limit have not been presented in a concrete manner. This paper discusses these factors and presents a methodology that can extend the measurement bandwidth of the sensor. The limiting factors are investigated extensively by analysis, numerical simulations and experiments with the AMB. The relationship between the measurement bandwidth and the control system is also investigated. In addition, the measurement range of the gyro is discussed.