Tachometer signal jitter reduction system and method
Assessing and removing jitter from tachometer signals enhances the performance of condition monitoring systems where accurate tachometer signals are needed. A system as disclosed herein can be designed and configured to have a low order of operations, so as to allow for implementation on low cost microcontrollers, which can be important for bused, distributed monitoring systems in which the tachometer zero crossing data is collected at a tachometer sensor and then broadcast to other remote sensors needing that information for vibration or other advanced analysis. Moreover, for monolithic architecture systems (e.g., a centralized processing and control architecture), the low order of operation and small software code base allows the system to be a simple/low cost addition to existing monitoring systems.
1. A system of monitoring a rotating component comprising:
a tachometer sensor coupled to the rotating component so as to produce a tachometer signal representative of the speed of rotation of the rotating component;
a controller electronically coupled to the tachometer so as to receive the tachometer signal, the control system including a processor and a set of instructions, the set of instructions including:
determining an effect of jitter on the tachometer signal; and
removing the amount of jitter from the tachometer signal using a filter.
2. A system according to claim 1 , wherein the determining the effect is performed using a tachometer signal zero crossing time.
3. A system according to claim 2 , wherein the effect of jitter is presumed to be a zero mean Gaussian process.
4. A system according to claim 1 , wherein the filter is an infinite impulse response filter.
5. A system according to claim 4 , wherein the filter is run so as to be a zero phase filter.
6. A system according to claim 4 , wherein the filter is a single pole infinite impulse response filter.
7. A system according to claim 6 , wherein the single pole infinite impulse response filter is applied to a pseudo derivative of the tachometer zero crossing time.
8. A system according to claim 7 , wherein the pseudo derivative is generated by determining the change in time between successive tachometer zero crossing times.
9. A system according to claim 1 , further including, with the set of instructions, identifying tachometer signal variations unrelated to jitter.
10. A system according to claim 9 , wherein the identifying is completed by integrating the filtered pseudo derivative of the zero crossing time.
11. A system according to claim 1 , wherein the removing results in increase separability for an analysis of condition indicators.
12. A system according to claim 1 , wherein the filter includes a filter coefficient and wherein the filter coefficient is determined using an objective function that is continuous and has a derivative.