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Real-Time Order Tracking of Gear Mesh Vibration in High Speed Planetary Gearboxes
Last modified: 2017-12-15
Abstract
Vibrations caused by gear meshing can lead to audible noise. This is particularly prevalent in applications where a high power density is needed. In transportation, aerospace or similar industries lightweight structures provide high fuel efficiency but are susceptible to vibration. Passive damping introduces an undesirable amount of weight. The gear design is largely constraint by efficiency requirements and cannot prioritize quiet operation. Active vibration control using inertial mass actuators may provide a lightweight and efficient solution in this situation. The active vibration control strategy needs to be closely matched to the excitation mechanism. Therefore, a thorough experimental investigation is needed.
[Figure included in MS Word document]
Fig. 1 Left: Core of the experimental setup. Outer assemblies are not displayed. Right: Close-up view gear box mount.
The vibration of differently sized planetary gear boxes are examined on the test rig displayed in Fig. 1. The gear box is driven at speeds up to 10,000 rpm by an electric motor. An eddy current brake can apply up to 30 Nm of load to the output shaft. This results into a vibration spectrum filling the complete audible range. The test rig can record not only the acceleration on the surface but also internal forces and torques using a configuration of two triaxial force transducers. Within these parameters stationary and transient operation is investigated. The correlation of the vibration to load, speed and size of the gear box is analyzed.
In comparison to parallel gear boxes, planetary gear boxes exhibit a more complex gear mesh excitation. The cyclic motion of the planet gears causes a modulation of magnitude and phase of the gear mesh vibration. Because of the high frequency and the deterministic behavior of the vibration signal, adaptive feed-forward control is most suited to the problem. The complex vibration signal can be split into a sum of harmonic oscillators. This requires a technique called order tracking. Here integral transform methods, Vold-Kalman-filters and heterodyne filters are viable approaches. The performance of these three approaches is compared. However, only a heterodyne filter bank is able to achieve real-time performance. On the foundation of the heterodyne filter bank an active vibration control scheme is proposed.
[Figure included in MS Word document]
Fig. 1 Left: Core of the experimental setup. Outer assemblies are not displayed. Right: Close-up view gear box mount.
The vibration of differently sized planetary gear boxes are examined on the test rig displayed in Fig. 1. The gear box is driven at speeds up to 10,000 rpm by an electric motor. An eddy current brake can apply up to 30 Nm of load to the output shaft. This results into a vibration spectrum filling the complete audible range. The test rig can record not only the acceleration on the surface but also internal forces and torques using a configuration of two triaxial force transducers. Within these parameters stationary and transient operation is investigated. The correlation of the vibration to load, speed and size of the gear box is analyzed.
In comparison to parallel gear boxes, planetary gear boxes exhibit a more complex gear mesh excitation. The cyclic motion of the planet gears causes a modulation of magnitude and phase of the gear mesh vibration. Because of the high frequency and the deterministic behavior of the vibration signal, adaptive feed-forward control is most suited to the problem. The complex vibration signal can be split into a sum of harmonic oscillators. This requires a technique called order tracking. Here integral transform methods, Vold-Kalman-filters and heterodyne filters are viable approaches. The performance of these three approaches is compared. However, only a heterodyne filter bank is able to achieve real-time performance. On the foundation of the heterodyne filter bank an active vibration control scheme is proposed.