Implementation of Direct Floor Vibration Feedforward Using an Absolute Displacement Sensor

Acceleration signal from an accelerometer has been conventionally used in the field of vibration control. However, its integration in order to detect the velocity signal will amplify the pink-noise of the sensor and cause a drift problem in low frequency, when the accelerometer is applied as a feedback or feedforward sensor. In this paper, an absolute displacement sensor, which can simultaneously detect the acceleration, velocity, and displacement signals from its stable control loops, is proposed, and the direct velocity and displacement feedforwards are implemented for an air type anti-vibration apparatus. Namely, the floor vibration is detected as the velocity and displacement signals, and those are directly fed forward to the voice coil motor fixed with the apparatus. At first, the effects of the velocity and displacement feedforwards are respectively shown. Next, both feedforwards are simultaneously implemented. As these results, the performance to suppress the vibration of the isolated table is improved by using the direct floor vibration feedforward.