Vold-Kalman Order Tracking: New Methods for Vehicle Sound Quality and Drive-Train NVH Applications

The use of Kalman filter methods for high-performance order tracking of noise and vibration signals was introduced in 1993. Based on experience with that original formulation, further work has produced significant enhancements which greatly extend the ability of these methods to deal with several practical issues of concern in vehicle testing. This paper reports on advances in the areas of:

• RPM estimation accuracy, even for fast-changing events such as gear shifts;
• Higher order Kalman filters, with improved shapes for extracting modulated orders;
• Decoupling of close and even crossing orders by use of multiple RPM references;
• Significant speed improvement over the original algorithm.

Besides obtaining the magnitude and phase of selected orders as a function of time or RPM, the harmonic content may be extracted as time-histories, with no phase or leakage distortion. Because they are phase coherent with the original waveforms, these time histories are useful for the editing and synthesis of non-stationary order components in sound quality applications. The new algorithms have been integrated into a commercial sound quality system, which produced the vehicle test results presented here.