46 Estimation of Instantaneous Speed for Rotating Systems: New Processing Techniques 533 Comparison of Assigned Tach Vs. Baysian Estimate Difference between Processed Tach Estimate and Baysian Estimate Percentage Difference between Processed Tach Estimate and Baysian Estimate Instantaneous speed estimate (rpm) Instantaneous speed estimate (rpm) Time(sec) Time(sec) Time(sec) Assigned Tach Bayesian 3 a c b 2.5 2 1.5 0.5 0 0 5 10 15 20 25 30 -200 -100 0 0 100 200 300 400 500 5 10 15 20 25 30 5 -3 -2.5 -2 -1.5 -0.5 0 0.5 1.5 Percentage difference in RPM (%) 2 1 -1 10 15 20 25 30 1 x 10 4 Fig. 46.15 (a) Bayesian estimate vs nth pulse estimate, (b) absolute difference and (c) % difference The Bayesian algorithm provides a way of estimating the speed from vibration data without the need for a tachometer. This can prove highly advantageous for applications with constraints like space, cost or unfavourable operating conditions. The smart algorithm developed in this work greatly reduces the analysis required and thus brings down the processing time by as much as 100 times. The most important contribution of this algorithm is the ability to reprocess with different parameters over different parts of the data. The results have a high signal to noise ratio and can directly be used for generation of RPM spectral maps. There is no need for approximations and assumptions in the assignment of a particular speed to a given data block [7]. Though the benefits from this method are attractive, there are several shortcomings like the requirement of a high speed computer and a skilled operator due to which it might not be viable for all practical real time applications.
RkJQdWJsaXNoZXIy MTMzNzEzMQ==