Active Control of Gear Noise Using Magnetic Bearings for Actuation

This paper investigates experimentally the active control of gear noise and vibration using magnetic bearing actuators in a feedforward active control scheme. The dynamic forces caused by gear meshing can produce large noise and vibration signatures that can cause annoyance and also fatigue mechanical components. In this work active magnetic bearings were used as actuators to introduce control forces very close to the source of the disturbance i.e. directly onto the rotating shaft. The proximity of the actuators to the source ensures that substantial control can be achieved using a small number of actuators. A four-square gear rig was constructed in order to test the control methodology experimentally. A proximity sensor placed near the gear teeth was used as a reference sensor and used to drive the two magnetic bearing actuators through a time domain filtered X-LMS control system to minimize the outputs from both vibration and pressure error sensors. At one microphone over 20 dB of reduction in acoustic levels was achieved at the gear mesh frequency and an overall reduction of 6 dB was demonstrated at four microphones. It is also shown that gear mesh noise and sideband frequencies can be simultaneously controlled.