Tuning Recipe - Revision history

OlliW at 13:47, 21 January 2023

2023-01-21T13:47:20Z

← Older revision		Revision as of 15:47, 21 January 2023
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	<span style="font-size:88%">''by Yang/wdaehn, with edits by OlliW</span>''		<span style="font-size:88%">''by Yang/wdaehn, with edits by OlliW''</span>

	A major problem for people new to brushless gimbals is finding the correct values of the PID parameters. A PID controller is a well known and often used method for calculating a new input value by measuring the difference between the current state and a target state, and applying a formula to the difference. In theory, after the calculation is applied, the target state would be reached immediately, but in reality it is not, because e.g. the motor is not indefinitely fast. So in the next iteration there is still an error, smaller but it exists, and an improved input value is calculated based on the new difference between actual and target states.		A major problem for people new to brushless gimbals is finding the correct values of the PID parameters. A PID controller is a well known and often used method for calculating a new input value by measuring the difference between the current state and a target state, and applying a formula to the difference. In theory, after the calculation is applied, the target state would be reached immediately, but in reality it is not, because e.g. the motor is not indefinitely fast. So in the next iteration there is still an error, smaller but it exists, and an improved input value is calculated based on the new difference between actual and target states.

OlliW: /* Tuning Procedure */

2018-05-01T12:48:40Z

Tuning Procedure

← Older revision		Revision as of 14:48, 1 May 2018
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	== Tuning Procedure ==		== Tuning Procedure ==

			{{COMMENT\|T-STorM32 users please refer to the article [[Getting Started with T-STorM32]]}}.

	The tuning of one axis might impact the other axis, nevertheless it is best to tune one axis after the other. Accordingly, the first step in tuning a brand new gimbal is to disable all motors except of the pitch motor, and find the proper tuning parameters for it. Then the roll motor is enabled and the corresponding PID parameters are tuned. Finally, the yaw axis is done.		The tuning of one axis might impact the other axis, nevertheless it is best to tune one axis after the other. Accordingly, the first step in tuning a brand new gimbal is to disable all motors except of the pitch motor, and find the proper tuning parameters for it. Then the roll motor is enabled and the corresponding PID parameters are tuned. Finally, the yaw axis is done.

Timvrakas: /* The I Parameter */

2017-01-24T01:46:49Z

The I Parameter

← Older revision		Revision as of 03:46, 24 January 2017
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	Now the {{PARAMNAME\|I}}ntegral term can be adjusted. The goal is, similar to the other parameters, to find the largest possible value without introducing negative side effects.		Now the {{PARAMNAME\|I}}ntegral term can be adjusted. The goal is, similar to the other parameters, to find the largest possible value without introducing negative side effects.

	In fact, the {{PARAMNAME\|I}} term plays a much more important role for the stabilization accuracy than the {{PARAMNAME\|D}} and {{PARAMNAME\|P}} parameters. In practical terms this means, that it is more important to set a large {{PARAMNAME\|I}} value, or vice versa, that one doesn't loose too much if {{PARAMNAME\|D}} and {{PARAMNAME\|P}} are not at their highest possible values. So, it is actually not a bad idea to lower {{PARAMNAME\|D}} and {{PARAMNAME\|P}}, as this increases e.g. the reliability of the PID controller behavior.		In fact, the {{PARAMNAME\|I}} term plays a much more important role for the stabilization accuracy than the {{PARAMNAME\|D}} and {{PARAMNAME\|P}} parameters. In practical terms this means, that it is more important to set a large {{PARAMNAME\|I}} value, or vice versa, that one doesn't loose too much if {{PARAMNAME\|D}} and {{PARAMNAME\|P}} are not at their highest possible values. So, it is actually not a bad idea to lower {{PARAMNAME\|D}} and {{PARAMNAME\|P}}, if this increases e.g. the reliability of the PID controller behavior.

	When you look carefully again at the last few seconds of the previous video, where {{PARAMNAME\|I}} was 5, you'll see that the camera could not be kept level when the gimbal was moved. The {{PARAMNAME\|I}} term is responsible for this part of the movement.		When you look carefully again at the last few seconds of the previous video, where {{PARAMNAME\|I}} was 5, you'll see that the camera could not be kept level when the gimbal was moved. The {{PARAMNAME\|I}} term is responsible for this part of the movement.

OlliW: /* Tuning Procedure */

2016-07-05T15:34:49Z

Tuning Procedure

OlliW: /* Balancing the Gimbal */

2016-07-05T14:00:04Z

Balancing the Gimbal

← Older revision		Revision as of 16:00, 5 July 2016
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	Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in someone points). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.		Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in someone points). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.

	A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts:		A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts, such as:
	* When the gimbal as a whole is accelerated, the camera would rotate out of position due to residual forces - see the image below.		* When the gimbal as a whole is accelerated, the camera would rotate out of position due to residual forces - see the image below.
	* The motors need to apply more power to keep the camera in position.		* The motors need to apply more power to keep the camera in position.
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	* Vibrations in the gimbal are more easily induced.		* Vibrations in the gimbal are more easily induced.

	Balancing not only brings advantages, a ~~minimu~~ degree of balancing is in fact mandatory for the gimbal and controller to function at all. It's as simple as that: The better the balancing the better the gimbal performance. This holds true especially for a 3-axis gimbal.		Balancing not only brings advantages, a minimum degree of balancing is in fact mandatory for the gimbal and controller to function at all. It's as simple as that: The better the balancing the better the gimbal performance. This holds true especially for a 3-axis gimbal.

	You will always have to compromise, because e.g. the gimbal does not allow for infinitely precise adjustments, or because of friction in the motors, and so on. Hence take considerable effort in balancing the gimbal as good as possible, but at some point one of course has to let go.		You will always have to compromise, because e.g. the gimbal does not allow for infinitely precise adjustments, or because of friction in the motors, and so on. Hence take considerable effort in balancing the gimbal as good as possible, but at some point one of course has to let go.

OlliW: /* Balancing the Gimbal */

2016-07-05T13:59:15Z

Balancing the Gimbal

← Older revision		Revision as of 15:59, 5 July 2016
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	== Balancing the Gimbal ==		== Balancing the Gimbal ==

	Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in someone ~~point~~). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.		Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in someone points). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.

	A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts:		A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts:

OlliW: /* Balancing the Gimbal */

2016-07-05T13:59:02Z

Balancing the Gimbal

← Older revision		Revision as of 15:59, 5 July 2016
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	== Balancing the Gimbal ==		== Balancing the Gimbal ==

	Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in ~~one~~ point). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.		Before any tuning, the gimbal needs to be balanced. Balancing means to bring the center of gravity (COG) of the mounted camera into the center of all three gimbal motor axes (depending on the gimbal construction it is also part of the balancing to ensure that all three gimbal motor axes cross in someone point). A quick test, which may be sufficient for larger cameras, is to move the camera by hand while all gimbal motors are turned off: The camera should remain in its position whenever you let it go, as demonstrated in the video below.

	A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts:		A perfectly balanced gimbal has many advantages. Otherwise you will get artefacts:

OlliW at 13:57, 5 July 2016

2016-07-05T13:57:36Z

← Older revision		Revision as of 15:57, 5 July 2016
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	See [http://en.wikipedia.org/wiki/PID_controller Wikipedia] for further details on PID control.		See [http://en.wikipedia.org/wiki/PID_controller Wikipedia] for further details on PID control.

	Below a relatively simple and straight forward tuning technique is suggested, which often works surprisingly well, and has a theoretical foundation. However, it may also fail. In fact, it is important to realize that some gimbals might not be tunable at all, because e.g. too weak or too strong motors ~~are used~~, and other reasons. As a rule of thumb: When you don't get a good tuning within 10 min (per axis) then chances are that something is wrong with the gimbal design. There ain't no such thing as a hard to tune gimbal. There are just well and badly designed gimbals.		Below a relatively simple and straight forward tuning technique is suggested, which often works surprisingly well, and has a theoretical foundation. However, it may also fail. In fact, it is important to realize that some gimbals might not be tunable at all, because of e.g. too weak or too strong motors, too high friction, improper balance, and several other reasons. As a rule of thumb: When you don't get a good tuning within 10 min (per axis) then chances are that something is wrong with the gimbal design. There ain't no such thing as a hard to tune gimbal. There are just well and badly designed gimbals.

	== Balancing the Gimbal ==		== Balancing the Gimbal ==

OlliW at 14:56, 27 March 2016

2016-03-27T14:56:33Z

← Older revision		Revision as of 16:56, 27 March 2016
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	* In general, the smaller the camera the more important is the balance.		* In general, the smaller the camera the more important is the balance.

	[[File:DSC_7111.jpg]]		::[[File:DSC_7111.jpg]]

	{{#ev:youtube\|4Mq2NTyiBf8}}		::{{#ev:youtube\|4Mq2NTyiBf8}}

	== Tuning Procedure ==		== Tuning Procedure ==
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	* A parameter setting may be double-checked by turning the motors by hand into all allowed positions. This has less to do with the PID regulation by itself, but tests whether the current parameter values work well in all positions. If the gimbal and camera would be balanced perfectly, then there wouldn't be a need to do that, but, reality ...		* A parameter setting may be double-checked by turning the motors by hand into all allowed positions. This has less to do with the PID regulation by itself, but tests whether the current parameter values work well in all positions. If the gimbal and camera would be balanced perfectly, then there wouldn't be a need to do that, but, reality ...

	[[File:Storm32-wiki-imu-pid-01.jpg\|480px]]		::[[File:Storm32-wiki-imu-pid-01.jpg\|480px]]
	<!-- this simulator isn't a PID simulator!		<!-- this simulator isn't a PID simulator!
	=== The Online PID Simulator ===		=== The Online PID Simulator ===
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	{{COMMENT\|A common misconception is that the motor needs to work only against the forces/torques due to an improperly balanced gimbal, and that one thus can get away with smaller motor power or motors if only the gimbal is very well built. However, if one wants to move the camera with the stick or wants the camera to follow the gimbal (pan mode), then the motor has to work also against the mass momentum of the camera. Unpredictable dynamic forces such as wind and so on come in additionally. Keep all of that in mind when estimating the amount of force the motor should apply to the camera.}}		{{COMMENT\|A common misconception is that the motor needs to work only against the forces/torques due to an improperly balanced gimbal, and that one thus can get away with smaller motor power or motors if only the gimbal is very well built. However, if one wants to move the camera with the stick or wants the camera to follow the gimbal (pan mode), then the motor has to work also against the mass momentum of the camera. Unpredictable dynamic forces such as wind and so on come in additionally. Keep all of that in mind when estimating the amount of force the motor should apply to the camera.}}

	{{#ev:youtube\|wq6e38EWjWE}}		::{{#ev:youtube\|wq6e38EWjWE}}

	=== The D Parameter ===		=== The D Parameter ===
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	{{COMMENT\|In the GUI you can move the slider also using the cursor keys. Click on the slider handle with the mouse, and hit the left/right key to change the value by its minimal step width. Very useful, especially for adjusting D.}}		{{COMMENT\|In the GUI you can move the slider also using the cursor keys. Click on the slider handle with the mouse, and hit the left/right key to change the value by its minimal step width. Very useful, especially for adjusting D.}}

	{{#ev:youtube\|voxJ9IAcaQg}}		::{{#ev:youtube\|voxJ9IAcaQg}}

	=== The P Parameter ===		=== The P Parameter ===
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	The video shows the procedure. After five seconds, {{PARAMNAME\|P}} and {{PARAMNAME\|I}} are set to non-zero values and the gimbal moves into a level position. Then the {{PARAMNAME\|P}} value is increased. Once P = 15 is reached, some weird shakes start to appear when the motor is released from a tilted position, which get worse and worse, and with P = 23 the camera shakes for a while even. Only once the {{PARAMNAME\|P}} value is set back to 13 a smooth movement from all positions is achieved again.		The video shows the procedure. After five seconds, {{PARAMNAME\|P}} and {{PARAMNAME\|I}} are set to non-zero values and the gimbal moves into a level position. Then the {{PARAMNAME\|P}} value is increased. Once P = 15 is reached, some weird shakes start to appear when the motor is released from a tilted position, which get worse and worse, and with P = 23 the camera shakes for a while even. Only once the {{PARAMNAME\|P}} value is set back to 13 a smooth movement from all positions is achieved again.

	{{#ev:youtube\|O_FC6S_Lpgs}}		::{{#ev:youtube\|O_FC6S_Lpgs}}

	=== The I Parameter ===		=== The I Parameter ===
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	In the video, the {{PARAMNAME\|I}} value is initially set to 480. I in comparison to the behavior for I = 5, a perfect movement is now obtained: fast speed, the camera remains horizontal, it truly is horizontal, everything is fine. Maybe one can increase {{PARAMNAME\|I}} even further. At I = 700 the same situation, everything looks nice. At I = 1200, however, the camera isn't horizontally aligned, and - if you look carefully at the yellow cable of the IMU connector - you see that it is vibrating (sorry, not very visible in the video). So, I = 1200 is too high for sure. There were slight vibrations in some positions of the camera even at I = 700, so {{PARAMNAME\|I}} was set to 620 at the end.		In the video, the {{PARAMNAME\|I}} value is initially set to 480. I in comparison to the behavior for I = 5, a perfect movement is now obtained: fast speed, the camera remains horizontal, it truly is horizontal, everything is fine. Maybe one can increase {{PARAMNAME\|I}} even further. At I = 700 the same situation, everything looks nice. At I = 1200, however, the camera isn't horizontally aligned, and - if you look carefully at the yellow cable of the IMU connector - you see that it is vibrating (sorry, not very visible in the video). So, I = 1200 is too high for sure. There were slight vibrations in some positions of the camera even at I = 700, so {{PARAMNAME\|I}} was set to 620 at the end.

	{{#ev:youtube\|kGFhd7Q4vgw}}		::{{#ev:youtube\|kGFhd7Q4vgw}}

	== Repeat for all Axes ==		== Repeat for all Axes ==

OlliW: /* Balancing the Gimbal */

2015-09-14T14:46:47Z

Balancing the Gimbal

← Older revision		Revision as of 16:46, 14 September 2015
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	The video shows a well balanced gimbal. Here it is possible to move the camera to any orientation and let it free, without it turning back to a preferred orientation.		The video shows a well balanced gimbal. Here it is possible to move the camera to any orientation and let it free, without it turning back to a preferred orientation.

	~~Some further~~ tips:		Please also consider these tips:
	* It is {{WARNING\|'''important'''}} to electrically disconnect the motors from the board, since then they can rotate more freely than just being disabled in the GUI.		* It is {{WARNING\|'''important'''}} to electrically disconnect the motors from the board, since then they can rotate more freely than just being disabled in the GUI.
	* A much more severe test to check balance is to heavily shake the gimbal, up and down, left and right, forward and backward. When balanced, the camera will stay in the position it was before the shaking started. Do this for different camera positions.		* A much more severe test to check balance is to heavily shake the gimbal, up and down, left and right, forward and backward. When balanced, the camera will stay in the position it was before the shaking started. Do this for different camera positions.

← Older revision		Revision as of 03:46, 24 January 2017
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	Now the {{PARAMNAME\|I}}ntegral term can be adjusted. The goal is, similar to the other parameters, to find the largest possible value without introducing negative side effects.		Now the {{PARAMNAME\|I}}ntegral term can be adjusted. The goal is, similar to the other parameters, to find the largest possible value without introducing negative side effects.

	In fact, the {{PARAMNAME\|I}} term plays a much more important role for the stabilization accuracy than the {{PARAMNAME\|D}} and {{PARAMNAME\|P}} parameters. In practical terms this means, that it is more important to set a large {{PARAMNAME\|I}} value, or vice versa, that one doesn't loose too much if {{PARAMNAME\|D}} and {{PARAMNAME\|P}} are not at their highest possible values. So, it is actually not a bad idea to lower {{PARAMNAME\|D}} and {{PARAMNAME\|P}}, as this increases e.g. the reliability of the PID controller behavior.		In fact, the {{PARAMNAME\|I}} term plays a much more important role for the stabilization accuracy than the {{PARAMNAME\|D}} and {{PARAMNAME\|P}} parameters. In practical terms this means, that it is more important to set a large {{PARAMNAME\|I}} value, or vice versa, that one doesn't loose too much if {{PARAMNAME\|D}} and {{PARAMNAME\|P}} are not at their highest possible values. So, it is actually not a bad idea to lower {{PARAMNAME\|D}} and {{PARAMNAME\|P}}, if this increases e.g. the reliability of the PID controller behavior.

	When you look carefully again at the last few seconds of the previous video, where {{PARAMNAME\|I}} was 5, you'll see that the camera could not be kept level when the gimbal was moved. The {{PARAMNAME\|I}} term is responsible for this part of the movement.		When you look carefully again at the last few seconds of the previous video, where {{PARAMNAME\|I}} was 5, you'll see that the camera could not be kept level when the gimbal was moved. The {{PARAMNAME\|I}} term is responsible for this part of the movement.

← Older revision		Revision as of 17:34, 5 July 2016
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	== Tuning Procedure ==		== Tuning Procedure ==

	The tuning of one axis might impact the other axis, so it is best to tune one axis after the other. Accordingly, the first step in tuning a brand new gimbal is to disable all motors except of the pitch motor, and find the proper tuning parameters for it. Then the roll motor is enabled and the corresponding PID parameters are tuned. Finally, the yaw axis is done.		The tuning of one axis might impact the other axis, nevertheless it is best to tune one axis after the other. Accordingly, the first step in tuning a brand new gimbal is to disable all motors except of the pitch motor, and find the proper tuning parameters for it. Then the roll motor is enabled and the corresponding PID parameters are tuned. Finally, the yaw axis is done.

	Our goal in the PID tuning is to find the highest value for each of the {{PARAMNAME\|P}}, {{PARAMNAME\|I}} and {{PARAMNAME\|D}} parameters which still work stably. The higher the values the better distortions can be compensated, and the more accurate the camera will be hold in position. If a value however is too large, then the PID controller will overcompensate, and we will notice oscillations, noise, or even erratic behavior in the worst case.		Our goal in the PID tuning is to find the highest value for each of the {{PARAMNAME\|P}}, {{PARAMNAME\|I}} and {{PARAMNAME\|D}} parameters which still work stably. The higher the values the better distortions can be compensated, and the more accurate the camera will be hold in position. If a value however is too large, then the PID controller will overcompensate, and we will notice oscillations, noise, or even erratic behavior in the worst case.

	To find the sweet point we will start ~~with~~ a low value, increase it until the gimbal starts to misbehave, and ~~move back~~ until it works again. This will be done first for the {{PARAMNAME\|D}} parameter, when the {{PARAMNAME\|P}} value, and last but not least the {{PARAMNAME\|I}} term.		To find the sweet point we will start at a low value, increase it until the gimbal starts to misbehave, and lower it until it works again. This will be done first for the {{PARAMNAME\|D}} parameter, when the {{PARAMNAME\|P}} value, and last but not least the {{PARAMNAME\|I}} term.

	Before that, we will have to set the {{PARAMNAME\|Motor Vmax}} parameter, which also affects the tuning. Fortunately, it is relatively easy to adjust and not too critical (unless the gimbal tends to vibrations at certain gimbal ~~postions~~).		Before that, we will have to set the {{PARAMNAME\|Motor Vmax}} parameter, which also affects the tuning. Fortunately, this parameter is relatively easy to adjust and not too critical (unless the gimbal tends to vibrations at certain gimbal positons).

	The procedure is illustrated below also by videos.		The procedure is illustrated below also by videos.
			<!--
	Further tips:		Further tips:
	* A parameter setting may be double-checked by turning the motors by hand into all allowed positions. This has less to do with the PID regulation by itself, but tests whether the current parameter values work well in all positions. If the gimbal and camera would be balanced perfectly, then there wouldn't be a need to do that, but, reality ...		* A parameter setting may be double-checked by turning the motors by hand into all allowed positions. This has less to do with the PID regulation by itself, but tests whether the current parameter values work well in all positions. If the gimbal and camera would be balanced perfectly, then there wouldn't be a need to do that, but, reality ...

	::[[File:Storm32-wiki-imu-pid-01.jpg\|480px]]		::[[File:Storm32-wiki-imu-pid-01.jpg\|480px]]
	<!-- this simulator isn't a PID simulator!		--><!-- this simulator isn't a PID simulator!
	=== The Online PID Simulator ===		=== The Online PID Simulator ===
	If you want to know more about the PID control loop, there is a [[PID online simulator]] page showing the effects in a diagram and let you play with the various parameters.-->		If you want to know more about the PID control loop, there is a [[PID online simulator]] page showing the effects in a diagram and let you play with the various parameters.-->
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	Also, ensure that:		Also, ensure that:
	* All three axes should be in hold mode, i.e., in the {{GUI\|Pan}} tab the parameters {{PARAMNAME\|Pitch Pan}}, {{PARAMNAME\|Roll Pan}} and {{PARAMNAME\|Yaw Pan}} should be set to zero or alternatively the {{PARAMNAME\|Pan Mode Default Setting}} set to {{PARAMVALUE\|hold hold hold}}.		* All three axes should be in hold mode, i.e., in the {{GUI\|Pan}} tab the parameters {{PARAMNAME\|Pitch Pan}}, {{PARAMNAME\|Roll Pan}} and {{PARAMNAME\|Yaw Pan}} should be set to zero or alternatively the {{PARAMNAME\|Pan Mode Default Setting}} set to {{PARAMVALUE\|hold hold hold}}.
	* {{PARAMNAME\|Voltage Correction}} should be set to 0%.		* {{PARAMNAME\|Voltage Correction}} should be set to {{PARAMVALUE\|0%}}.
	* A 2nd IMU should be deactivated, i.e., in the {{GUI\|Setup}} tab the parameter {{PARAMNAME\|Imu2 Configuration}} should be set to {{PARAMVALUE\|off}}.		* A 2nd IMU should be deactivated, i.e., in the {{GUI\|Setup}} tab the parameter {{PARAMNAME\|Imu2 Configuration}} should be set to {{PARAMVALUE\|off}}.
	* The battery should neither be fully charged nor nearly discharged, i.e., have a voltage of about 3.7 V per cell.		* The battery should neither be fully charged nor nearly discharged, i.e., have a voltage of about 3.7 V per cell.