Gyroscope Primer - Revision history

Mparadis: /* Drift */

2014-07-02T16:00:25Z

Drift

← Older revision		Revision as of 16:00, 2 July 2014
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	==Drift==		==Drift==
	Gyroscopes drift. It is unavoidable. Even extremely expensive, high end models will have significant drift. For example, the [[~~1056~~ User Guide\|~~1056~~]] is rated to drift 4°/min. So over the course of an hour of measurements, the gyroscope will be reporting values that are ~~240~~° off what they should be. This is obviously quite substantial. In order to compensate for drift there are a few things you can do:		Gyroscopes drift. It is unavoidable. Even extremely expensive, high end models will have significant drift. For example, the [[1042 User Guide\|1042]] is rated to drift 0.114°/min, so over the course of an hour of measurements, the gyroscope will be reporting values that are nearly 7° off what they should be. This is obviously quite substantial. In order to compensate for drift there are a few things you can do:

	The best thing to do is zero the gyro on a regular basis. Zeroing the gyro will reset the drift back to nothing and you can begin again. The problem with this is that you can only zero the gyro when it is stationary. This means that you will need to stop movement for a period of time (it can take a few seconds to complete the operation) before continuing on with measurements.		The best thing to do is zero the gyro on a regular basis. Zeroing the gyro will reset the drift back to nothing and you can begin again. The problem with this is that you can only zero the gyro when it is stationary. This means that you will need to stop movement for a period of time (it can take a few seconds to complete the operation) before continuing on with measurements.

Burley: /* Noise */

2012-08-07T18:29:33Z

Noise

← Older revision		Revision as of 18:29, 7 August 2012
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	==Noise==		==Noise==

	Noise is present in gyroscopes just like any other device. ~~While drift~~ is ~~the more important characteristic for gyroscopes,~~ noise ~~must still~~ be ~~taken into account~~. Noise levels will be different for each axis, because each orientation of sensor is build slightly differently and they are on different chips with different manufacturing procedures. Two of the major types of noise are white noise and random walk.		Noise is present in gyroscopes just like any other device however with gyroscopes noise is often not as important. Most typical uses of gyroscopes involve detecting large movements and as a result noise is easy to distinguish and ignore. Nevertheless noise can be a concern if it is too large. Noise levels will be different for each axis, because each orientation of sensor is build slightly differently and they are on different chips with different manufacturing procedures. Two of the major types of noise are white noise and random walk.

	===White Noise===		===White Noise===

Burley: /* Noise */

2012-08-07T18:25:57Z

Noise

← Older revision		Revision as of 18:25, 7 August 2012
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	White noise is the short-term noise that is contributed to from a number of internal and external factors. For example, when a gyroscope is stationary on your desk, it might read 100°/s one sample, 101°/s another sample, and 97°/s in yet another sample. Luckily, white noise is usually fairly consistent which means it can be mitigated quite effectively if you average multiple samples together. With a Phidgets Inc. gyroscope, if you select a data rate slower than its maximum it will automatically average as many samples as it can within that time frame for each value. In applications where you need an extremely fast sampling rate, and can't afford to spend time averaging samples, you should look for a gyroscope with low white noise. Also keep in mind the noisiness of your environment- For example, the engine and road noise on a bus will easily be more noisy than the gyroscope - so there is no point in paying for a low noise device. See the [[Allan Deviation Primer]] for more information on spatial noise characteristics.		White noise is the short-term noise that is contributed to from a number of internal and external factors. For example, when a gyroscope is stationary on your desk, it might read 100°/s one sample, 101°/s another sample, and 97°/s in yet another sample. Luckily, white noise is usually fairly consistent which means it can be mitigated quite effectively if you average multiple samples together. With a Phidgets Inc. gyroscope, if you select a data rate slower than its maximum it will automatically average as many samples as it can within that time frame for each value. In applications where you need an extremely fast sampling rate, and can't afford to spend time averaging samples, you should look for a gyroscope with low white noise. Also keep in mind the noisiness of your environment- For example, the engine and road noise on a bus will easily be more noisy than the gyroscope - so there is no point in paying for a low noise device. See the [[Allan Deviation Primer]] for more information on spatial noise characteristics.


	===Random Walk===		===Random Walk===

	Often called drift, random walk is the long-term noise that causes samples to gradually become further and further away from their true values. This type of noise is less important for applications with constant movement and a fast sampling rate, but for applications where values are averaged over longer periods of time, it can cause severe inaccuracies. See the [[Allan Deviation Primer]] for more information on accelerometer noise characteristics.		Often called drift, random walk is the long-term noise that causes samples to gradually become further and further away from their true values. This type of noise is less important for applications with constant movement and a fast sampling rate, but for applications where values are averaged over longer periods of time, it can cause severe inaccuracies. See the [[Allan Deviation Primer]] for more information on accelerometer noise characteristics.

Burley: /* Noise */

2012-08-07T18:25:45Z

Noise

← Older revision		Revision as of 18:25, 7 August 2012
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	==Noise==		==Noise==

	~~As with all electronics~~, ~~electronic compasses will~~ be ~~effected by some amount of noise, usually caused by thermal and mechanical fluctuations inside the sensor~~. Noise levels will be different for each axis, because each orientation of sensor is build slightly differently ~~(for example, it is much more difficult to get low noise from the vertical axis because the sensor is a flat piece of silicon~~. Two of the major types of noise are white noise and random walk.		Noise is present in gyroscopes just like any other device. While drift is the more important characteristic for gyroscopes, noise must still be taken into account. Noise levels will be different for each axis, because each orientation of sensor is build slightly differently and they are on different chips with different manufacturing procedures. Two of the major types of noise are white noise and random walk.

	===White Noise===		===White Noise===

	White noise is the short-term noise that is contributed to from a number of internal and external factors. For example, when a ~~compass~~ is stationary on your desk, it might read 100μG one sample, 101μG another sample, and 97μG in yet another sample. Luckily, white noise is usually fairly consistent which means it can be mitigated quite effectively if you average multiple samples together. With a Phidgets Inc. ~~compass~~, if you select a data rate slower than its maximum it will automatically average as many samples as it can within that time frame for each value. In applications where you need an extremely fast sampling rate, and can't afford to spend time averaging samples, you should look for a ~~compass~~ with low white noise. Also keep in mind the noisiness of your environment- For example, the engine and road noise on a bus will easily be more noisy than the ~~compass~~ - so there is no point in paying for a low noise device. See the [[Allan Deviation Primer]] for more information on spatial noise characteristics.		White noise is the short-term noise that is contributed to from a number of internal and external factors. For example, when a gyroscope is stationary on your desk, it might read 100°/s one sample, 101°/s another sample, and 97°/s in yet another sample. Luckily, white noise is usually fairly consistent which means it can be mitigated quite effectively if you average multiple samples together. With a Phidgets Inc. gyroscope, if you select a data rate slower than its maximum it will automatically average as many samples as it can within that time frame for each value. In applications where you need an extremely fast sampling rate, and can't afford to spend time averaging samples, you should look for a gyroscope with low white noise. Also keep in mind the noisiness of your environment- For example, the engine and road noise on a bus will easily be more noisy than the gyroscope - so there is no point in paying for a low noise device. See the [[Allan Deviation Primer]] for more information on spatial noise characteristics.

Burley: /* Drift */

2012-08-07T18:18:28Z

Drift

← Older revision		Revision as of 18:18, 7 August 2012
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	In practice a combination of the 2 above strategies is the best. Continually subtracting drift from the measurements and zeroing whenever it is possible to do so.		In practice a combination of the 2 above strategies is the best. Continually subtracting drift from the measurements and zeroing whenever it is possible to do so.

			==Noise==

			As with all electronics, electronic compasses will be effected by some amount of noise, usually caused by thermal and mechanical fluctuations inside the sensor. Noise levels will be different for each axis, because each orientation of sensor is build slightly differently (for example, it is much more difficult to get low noise from the vertical axis because the sensor is a flat piece of silicon. Two of the major types of noise are white noise and random walk.

			===White Noise===

			White noise is the short-term noise that is contributed to from a number of internal and external factors. For example, when a compass is stationary on your desk, it might read 100μG one sample, 101μG another sample, and 97μG in yet another sample. Luckily, white noise is usually fairly consistent which means it can be mitigated quite effectively if you average multiple samples together. With a Phidgets Inc. compass, if you select a data rate slower than its maximum it will automatically average as many samples as it can within that time frame for each value. In applications where you need an extremely fast sampling rate, and can't afford to spend time averaging samples, you should look for a compass with low white noise. Also keep in mind the noisiness of your environment- For example, the engine and road noise on a bus will easily be more noisy than the compass - so there is no point in paying for a low noise device. See the [[Allan Deviation Primer]] for more information on spatial noise characteristics.


			===Random Walk===

			Often called drift, random walk is the long-term noise that causes samples to gradually become further and further away from their true values. This type of noise is less important for applications with constant movement and a fast sampling rate, but for applications where values are averaged over longer periods of time, it can cause severe inaccuracies. See the [[Allan Deviation Primer]] for more information on accelerometer noise characteristics.

Burley: /* How Gyroscopes Work */

2012-08-07T18:17:12Z

How Gyroscopes Work

← Older revision		Revision as of 18:17, 7 August 2012
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	==How Gyroscopes Work==		==How Gyroscopes Work==
	Gyroscopes contain small strips of metal that bend when the gyro twists and moves. By measuring the amount of bending the gryo can accurately report what angular velocity it is experiencing. Angular position is often what is desired however. In order to obtain angular position the angular velocity can be integrated over time. Once integrated the data will be similar to the data from a 3 axis compass, it is important to note however that the gyro data will be with respect to an arbitrary 0 where as the compass is with respect to the Earth's magnetic field. This means that the gyroscope will more often than not give you different numbers than the compass. The only time this is not true is when the gyro is zeroed directly parallel with the Earth's surface and pointing to the North magnetic pole.		Gyroscopes contain small strips of metal that bend when the gyro twists and moves. By measuring the amount of bending the gryo can accurately report what angular velocity it is experiencing. Angular position is often what is desired however. In order to obtain angular position the angular velocity can be integrated over time. This procedure is shown in the C# example "Spatial-wireframe." Once integrated the data will be similar to the data from a 3 axis compass, it is important to note however that the gyro data will be with respect to an arbitrary 0 where as the compass is with respect to the Earth's magnetic field. This means that the gyroscope will more often than not give you different numbers than the compass. The only time this is not true is when the gyro is zeroed directly parallel with the Earth's surface and pointing to the North magnetic pole.

	===Basic Use===		===Basic Use===

Burley at 15:39, 7 August 2012

2012-08-07T15:39:34Z

← Older revision		Revision as of 15:39, 7 August 2012
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			[[Category:Primer]]
	==Introduction==		==Introduction==
	A MEMS (microelectrical-mechanical system) gyroscope is a device that is used for measuring orientation. Accelerometers can perform a similar function when they are stationary by measuring the components on each axis of Earth's gravitational field. However, if the accelerometer is experiencing acceleration other than gravity it will not be able to distinguish and consequently will not be able to determine orientation. This is where gyroscopes become useful.		A MEMS (microelectrical-mechanical system) gyroscope is a device that is used for measuring orientation. Accelerometers can perform a similar function when they are stationary by measuring the components on each axis of Earth's gravitational field. However, if the accelerometer is experiencing acceleration other than gravity it will not be able to distinguish and consequently will not be able to determine orientation. This is where gyroscopes become useful.

Burley: /* Drift */

2012-08-03T20:48:11Z

Drift

← Older revision		Revision as of 20:48, 3 August 2012
Line 13:		Line 13:

	==Drift==		==Drift==
			Gyroscopes drift. It is unavoidable. Even extremely expensive, high end models will have significant drift. For example, the [[1056 User Guide\|1056]] is rated to drift 4°/min. So over the course of an hour of measurements, the gyroscope will be reporting values that are 240° off what they should be. This is obviously quite substantial. In order to compensate for drift there are a few things you can do:

			The best thing to do is zero the gyro on a regular basis. Zeroing the gyro will reset the drift back to nothing and you can begin again. The problem with this is that you can only zero the gyro when it is stationary. This means that you will need to stop movement for a period of time (it can take a few seconds to complete the operation) before continuing on with measurements.

			The next thing that can be done is to continually correct for the drift. In order to do this the drift rate needs to be measured over as long a period of time as possible. Keep the gyro as stationary as possible and leave it overnight. Check the gyro reading in the morning and you know how much the gyro has drifted over the period of X hours. Now you can divide that down to determine the drift amount for each individual sample, and then in your program you can subtract the drift amount from each and every sample. The issue is that drift is not constant, averaging over a large period of time will help negate any instantaneous ill effects but individual samples still have a margin of error associated with the subtracted drift value.

			In practice a combination of the 2 above strategies is the best. Continually subtracting drift from the measurements and zeroing whenever it is possible to do so.

Burley: /* Basic Use */

2012-08-03T19:45:15Z

Basic Use

← Older revision		Revision as of 19:45, 3 August 2012
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	Note that the gyro headings are the roll, pitch and yaw of the gyro with respect to the arbitrary zero point set at the beginning.		Note that the gyro headings are the roll, pitch and yaw of the gyro with respect to the arbitrary zero point set at the beginning.

			==Drift==

Burley: /* How Gyroscopes Work */

2012-08-03T19:31:18Z

How Gyroscopes Work

← Older revision		Revision as of 19:31, 3 August 2012
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	==How Gyroscopes Work==		==How Gyroscopes Work==
			Gyroscopes contain small strips of metal that bend when the gyro twists and moves. By measuring the amount of bending the gryo can accurately report what angular velocity it is experiencing. Angular position is often what is desired however. In order to obtain angular position the angular velocity can be integrated over time. Once integrated the data will be similar to the data from a 3 axis compass, it is important to note however that the gyro data will be with respect to an arbitrary 0 where as the compass is with respect to the Earth's magnetic field. This means that the gyroscope will more often than not give you different numbers than the compass. The only time this is not true is when the gyro is zeroed directly parallel with the Earth's surface and pointing to the North magnetic pole.

			===Basic Use===
			In general gryoscopes must be calibrated, most are calibrated at the factory where they are manufactured though. Check the data sheets for the gyro you have to see if it requires manual calibration.

			Once calibrated you are ready to start using the gyro. When you power it up you need to hold it as still as possible and then use the zero function or button to make the gyro ready to take accurate measurements.

			Note that the gyro headings are the roll, pitch and yaw of the gyro with respect to the arbitrary zero point set at the beginning.