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# Differentiate X Y and Z Values

07/07/2018 11:49 PM

How do I different the values in X, Y ,Z axis reading in accelerometer between vibrating engine but idle vehicle and vibrating engine with moving vehicle ?

Any differentiated in the X, Y and Z value will be recorded?

Can we different the value from there?

Thank you

Pathfinder Tags: accelerometer engine speeds
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Guru

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#1

### Re: How do I different the values in X, Y ,Z axis reading in accelerometer between vibrating engine but idle vehicle and vibrating engine with moving vehicle ?

07/08/2018 12:24 AM

Yes.

Compare the differences.

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#8
In reply to #1

### Re: How do I different the values in X, Y ,Z axis reading in accelerometer between vibrating engine but idle vehicle and vibrating engine with moving vehicle ?

07/09/2018 11:47 PM

I agree with Lyn.

Why is the engine vibrating .

Are you trying to check the difference between a stationary and static condition.

Is this a test vehicle.

2
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#2

### Re: Differentiate X Y and Z Values

07/08/2018 10:36 AM

You need to take the frequency spectrum of the acceleration values. The spectrum will consist of a series of harmonics that are multiples of the engine rotation rate and cylinder firing rates. When the automobile is in motion, the RPM will be higher and these frequency peaks will be shifted up in frequency.

http://www.vibrotek.com/articles/state/index.htm

You could use a bandpass filter tuned to the peak idle frequency vibration. When the engine turns faster, the peak will shift out of the passband of the filter.

Good Answer (Score 2)
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#9
In reply to #2

### Re: Differentiate X Y and Z Values

07/10/2018 1:30 AM

And also consider the frequency of ground contacting components, road components, paving anomalies (washboards for instance) that can add more excitation to the mechanical system through resilient motor mounts, and transient torque pulsation applied to the power train.

i think with wheel diameter, knowing reduction from engine crankshaft speed, you should be able to mask road noise and cyclic excitation from other rotating components (ie wheel balance). The key is to assume that the engine speed while driving the wheels is proportional to ground speed. Also to collect enough data to be able to discriminate between (hopefully random) road noise & engine produced vibration.

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#3

### Re: Differentiate X Y and Z Values

07/08/2018 12:06 PM
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#4

### Re: Differentiate X Y and Z Values

07/08/2018 9:57 PM

You have to have a three axis accelerometer.

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#5

### Re: Differentiate X Y and Z Values

07/09/2018 8:02 AM

Or three separate accelerometers.

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#6

### Re: Differentiate X Y and Z Values

07/09/2018 8:42 AM

You may use three separate unidirectional accelerator on each axis.

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#7
In reply to #6

### Re: Differentiate X Y and Z Values

07/09/2018 9:00 AM

Alignment to exact orthogonality can be the complication the OP is trying to avoid. Just buy the correct hardware.

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#10

### Re: Differentiate X Y and Z Values

07/10/2018 12:04 PM

At what times did the stationary engine start, and stop, vibrating?...

At what times did the moving engine start, and stop, vibrating?...

How do those times correlate, if at all?...

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