ਟਰੈਕਿੰਗ ਫਿਲਟਰ ਨੂੰ ਸਮਝਣਾ
A ਟ੍ਰੈਕਿੰਗ ਫਿਲਟਰ — also called an order-tracking filter or synchronous filter — is a narrow ਬੈਂਡ-ਪਾਸ ਫ਼ਿਲਟਰ ਵਿੱਚ ਵਰਤੀ ਜਾਂਦੀ ਵਾਈਬ੍ਰੇਸ਼ਨ ਵਿਸ਼ਲੇਸ਼ਣ instruments that automatically slides its centre frequency to follow a chosen multiple, or order, of the machine’s rotational speed. A “1× tracking filter,” for example, continuously locks onto the running-speed frequency, rejecting everything else and passing only the fundamental 1× component; a 2× or 3× filter follows twice or three times running speed in the same way. Because the filter rides the speed rather than sitting at a fixed frequency, it can measure the ਐਂਪਲੀਟਿਊਡ (ਆਯਾਮ) ਅਤੇ ਫੇਜ਼ of a synchronous component even while the machine accelerates or coasts down. That makes tracking filters essential for variable-speed equipment, for startup and ਕੋਸਟਡਾਊਨ transients, and for isolating individual order components within ਆਰਡਰ ਵਿਸ਼ਲੇਸ਼ਣ.
1. How a Tracking Filter Works
The basic principle
- ਗਤੀ ਸੰਦਰਭ: a ਟੈਕੋਮੀਟਰ ਜਾਂ ਕੀਫੇਜ਼ਰ supplies a once-per-revolution pulse.
- Frequency calculation: the instrument derives the instantaneous rotational frequency from the timing of those pulses.
- Order multiplication: it multiplies that frequency by the chosen order number — 1, 2, 3, and so on.
- Filter centring: a narrow band-pass filter is centred on the resulting frequency.
- Continuous adjustment: as the speed changes, the filter’s centre frequency tracks it without interruption.
- ਆਉਟਪੁੱਟ: a clean filtered signal containing only the selected order.
The defining trick is that the filter is slaved to the tachometer, so it always knows where the order of interest currently lives on the frequency axis — something a fixed filter can never do on a machine whose speed moves.
Filter characteristics
- ਬੈਂਡਵਿਡਥ: typically ±2–10% of the centre frequency.
- ਸੰਕੁਚਿਤਤਾ: rejects neighbouring frequencies effectively.
- Tracking rate: able to follow rapidly changing speeds.
- Multiple filters: modern instruments can track several orders at once.
2. Applications
1. Startup and coastdown analysis
This is the headline application. As the machine runs up or coasts down through its speed range, a tracking filter follows the 1× component continuously:
- Track 1× amplitude and phase against speed during the transient — the same data captured during a ਰਨ-ਅੱਪ.
- ਬਣਾਓ ਬੋਡ ਪਲਾਟ of amplitude and phase versus speed.
- ਪਛਾਣ ਕਰੋ ਕ੍ਰਿਟੀਕਲ ਸਪੀਡਾਂ from the amplitude peaks.
- Estimate ਡੈਂਪਿੰਗ from the width of each resonance peak.
- Track 2× and 3× simultaneously to reveal multiple modes.
2. Variable-speed equipment
- Maintain order-based measurements despite a constantly moving speed.
- VFD-driven motors whose speed changes with the process.
- Wind turbines responding to gusting wind.
- Process equipment whose speed drifts with load.
- Consistent trending regardless of speed fluctuation, because everything is referenced to orders rather than fixed frequencies.
3. ਬੈਲੇਂਸਿੰਗ
- Track the 1× component throughout the ਬੈਲੇਂਸਿੰਗ procedure.
- Filter out non-1× content for a cleaner reading.
- Take the phase measurement at the 1× frequency only.
- Improve accuracy by rejecting unrelated vibration sources.
4. Order-specific analysis
- Isolate a particular order for detailed study.
- Track 2× to monitor the progression of ਮਿਸਅਲਾਈਨਮੈਂਟ.
- Follow the blade passing order in fans and pumps.
- Separate frequency components that would otherwise overlap.
3. Advantages of Tracking Filters
Speed independence
- Measurements stay meaningful no matter how the speed varies.
- Data from different speeds can be compared on the same order basis.
- Essential for any machine that does not hold a constant speed.
Component isolation
- Separates one order from every other frequency present.
- Yields cleaner signals than a full-spectrum FFT.
- Improves the signal-to-noise ratio for the order of interest.
- Enables precise amplitude and phase measurement of that order. This synchronous focus is conceptually allied to synchronous averaging, which also uses the tachometer to lift speed-locked components out of the noise.
Transient analysis
- Follows components straight through speed changes.
- Provides continuous measurement during acceleration and deceleration.
- Needs no steady-state condition.
- Reveals speed-dependent behaviour that a static measurement would miss.
4. Limitations and Considerations
It requires a tachometer
- An accurate speed reference is mandatory.
- The quality of the tachometer signal directly limits filter performance.
- It cannot be used on equipment without a speed reference.
- The once-per-revolution pulse must be reliable, or the tracking wanders.
It tracks only synchronous components
- Non-synchronous faults are not captured — including most ਬੇਅਰਿੰਗ ਨੁਕਸ, which produce ਅਸਿੰਕ੍ਰੋਨਸ ਵਾਈਬ੍ਰੇਸ਼ਨ.
- Electrical-line frequencies are not tracked.
- Random and broadband vibration is filtered out.
- Complementary analysis is needed for a complete diagnosis.
Filter-bandwidth trade-offs
- Narrow filter: better rejection of adjacent frequencies, but slower to respond to speed changes.
- Wide filter: faster tracking, but may admit nearby components.
- ਓਪਟੀਮਲ: a 5–10% bandwidth suits most applications, balancing selectivity against tracking speed.
5. Tracking Filter versus FFT
A tracking filter and an FFT are complementary rather than competing tools. The FFT shows the whole spectrum at a fixed speed; the tracking filter follows one order through changing speed. The table summarises where each excels.
| ਵਿਸ਼ੇਸ਼ਤਾ | FFT ਵਿਸ਼ਲੇਸ਼ਣ | ਟਰੈਕਿੰਗ ਫਿਲਟਰ |
|---|---|---|
| Speed requirement | ਕਿਸੇ ਵੀ ਸਪੀਡ 'ਤੇ ਕੰਮ ਕਰਦਾ ਹੈ | Requires a tachometer |
| Speed variation | ਸਥਿਰ ਗਤੀ ਦੀ ਲੋੜ ਹੈ | ਬਦਲਦੀ ਗਤੀ ਨੂੰ ਸੰਭਾਲਦਾ ਹੈ |
| ਜਾਣਕਾਰੀ | ਪੂਰਾ ਸਪੈਕਟ੍ਰਮ, ਸਾਰੀਆਂ ਫ੍ਰੀਕੁਐਂਸੀਆਂ | ਸਿਰਫ਼ ਸਿੰਗਲ ਆਰਡਰ |
| Non-synchronous faults | ਸਾਰੇ ਨੁਕਸ ਦਾ ਪਤਾ ਲਗਾਉਂਦਾ ਹੈ | ਗੈਰ-ਸਿੰਕ੍ਰੋਨਸ ਖੁੰਝ ਜਾਂਦਾ ਹੈ |
| Transient analysis | ਮੁਸ਼ਕਲ | ਸ਼ਾਨਦਾਰ |
| ਲਈ ਸਭ ਤੋਂ ਵਧੀਆ | ਆਮ ਡਾਇਗਨੌਸਟਿਕਸ, ਸਥਿਰ-ਸਟੇਟ | Critical-speed analysis, variable speed |
6. Modern Implementations
Digital tracking filters
- Implemented in software inside modern analysers.
- Track multiple orders at once — 1×, 2×, 3× concurrently.
- Offer adjustable bandwidth.
- Display in real time during transients.
Integration with order analysis
- Tracking filters form the foundation of comprehensive order analysis.
- The full order spectrum is extracted, all orders together.
- Results appear as colour maps of order against speed, closely related to the waterfall ਅਤੇ ਕੈਸਕੇਡ displays.
- Critical speeds can be detected automatically from the order-tracking data.
7. Tracking Filters in Field Balancing
On a portable instrument the tracking filter is what keeps a balancing measurement honest when the speed will not hold perfectly steady. By passing only the 1× order and rejecting everything else, it gives the software a clean amplitude-and-phase vector to work from. The Balanset-1A uses exactly this approach: its tachometer pulse defines running speed, the synchronous 1× component is extracted in the machine’s own bearings at operating speed, and the resulting vector drives the trial-weight and correction calculations — and then confirms the residual vibration after correction. The tracking filter is the quiet mechanism that makes those numbers repeatable on real, slightly-unsteady machinery.
Tracking filters are specialised but powerful tools, especially for rotor dynamics and variable-speed equipment. By holding their focus on a chosen order while the speed moves, they enable transient analysis and speed-independent monitoring that ordinary FFT techniques cannot match — which is precisely why they remain central to critical-speed identification and advanced machinery diagnostics.
