Regbot encoder analysis - Revision history

Jca: /* Regbot encoder issues */

2024-11-28T13:48:48Z

Regbot encoder issues

Jca: /* Regbot encoder issues */

2024-11-28T13:45:27Z

Regbot encoder issues

← Older revision		Revision as of 15:45, 28 November 2024
Line 22:		Line 22:

	At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not equal or symmetric.		At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not equal or symmetric.
	In this case, the resulting velocity noise is about 20% of the velocity.		In this case, the resulting velocity noise is about 10% of the velocity.

Jca: /* Regbot encoder issues */

2024-11-28T13:44:17Z

Regbot encoder issues

← Older revision		Revision as of 15:44, 28 November 2024
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	The velocity is more stable at 10 cm/sec, and the average delay is less than 10 ms.		The velocity is more stable at 10 cm/sec, and the average delay is less than 10 ms.

	At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not ~~totally~~ equal.		At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not equal or symmetric.
			In this case, the resulting velocity noise is about 20% of the velocity.

Jca: /* Regbot encoder issues */

2024-11-28T13:25:56Z

Regbot encoder issues

← Older revision		Revision as of 15:25, 28 November 2024
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	The Regbot motors use a magnetic encoder at the motor axle, as shown below.		The Regbot motors use a magnetic encoder at the motor axle, as shown below.

	[[file:regbot_encoder_delay.png]]		[[file:regbot_encoder_delay.png \| 500px]]

	The encoder has 12 magnets and two HAL sensors. The sensors have a separation and position that should give symmetric A and B signals, as shown. If all magnet dipoles have exactly the same size and strength, then velocity can be estimated using the time between any two flanks. But this is not the reality.		The encoder has 12 magnets and two HAL sensors. The sensors have a separation and position that should give symmetric A and B signals, as shown. If all magnet dipoles have exactly the same size and strength, then velocity can be estimated using the time between any two flanks. But this is not the reality.
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	The following plot tests this. A fast PI velocity controller is used to obtain stable velocities between 0.05 and 1.3 m/s. The motor gear is 9.6:1, and the wheel radius is 0.03m.		The following plot tests this. A fast PI velocity controller is used to obtain stable velocities between 0.05 and 1.3 m/s. The motor gear is 9.6:1, and the wheel radius is 0.03m.

	[[file:encoder_delay.png]]		[[file:encoder_delay.png \| 500px]]

	The magnetic encoder is used to calculate motor (and robot) velocity, which is estimated based on the time between encoder ticks.		The magnetic encoder is used to calculate motor (and robot) velocity, which is estimated based on the time between encoder ticks.

Jca at 13:25, 28 November 2024

2024-11-28T13:25:08Z

← Older revision		Revision as of 15:25, 28 November 2024
Line 5:		Line 5:
	[[file:regbot_encoder_delay.png]]		[[file:regbot_encoder_delay.png]]

			The encoder has 12 magnets and two HAL sensors. The sensors have a separation and position that should give symmetric A and B signals, as shown. If all magnet dipoles have exactly the same size and strength, then velocity can be estimated using the time between any two flanks. But this is not the reality.

			A more stable velocity is obtained using the time between the same flank on the same signal, e.g. the rising flank on the A signal. This gives a velocity estimate at every flank, but the velocity is estimated over a longer time.

			The average delay is half the time between two equal flanks on the same signal plus the time since the flank was detected.

			The following plot tests this. A fast PI velocity controller is used to obtain stable velocities between 0.05 and 1.3 m/s. The motor gear is 9.6:1, and the wheel radius is 0.03m.

	[[file:encoder_delay.png]]		[[file:encoder_delay.png]]

	The magnetic encoder is used to calculate motor (and robot) velocity~~. The velocity~~ is estimated based on the time between encoder ticks.		The magnetic encoder is used to calculate motor (and robot) velocity, which is estimated based on the time between encoder ticks.

			At a robot velocity of 5 cm/sec, the average delay is often more than 30 ms. The velocity controller is not well designed for this delay.

			The velocity is more stable at 10 cm/sec, and the average delay is less than 10 ms.

			At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not totally equal.

Jca at 13:04, 28 November 2024

2024-11-28T13:04:35Z

← Older revision		Revision as of 15:04, 28 November 2024
Line 1:		Line 1:
	== Regbot encoder issues ==		== Regbot encoder issues ==

			The Regbot motors use a magnetic encoder at the motor axle, as shown below.

			[[file:regbot_encoder_delay.png]]



	[[file:encoder_delay.png]]		[[file:encoder_delay.png]]

	The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks.		The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks.

Jca: /* Regbot encoder issues */

2024-11-28T12:57:27Z

Regbot encoder issues

← Older revision		Revision as of 14:57, 28 November 2024
Line 1:		Line 1:
	== Regbot encoder issues ==		== Regbot encoder issues ==

	[[file::encoder_delay.png]]		[[file:encoder_delay.png]]

	The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks.		The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks.

Jca: Created page with "== Regbot encoder issues == file::encoder_delay.png The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks."

2024-11-28T12:57:08Z

Created page with "== Regbot encoder issues == [[file::encoder_delay.png]] The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks."

New page

== Regbot encoder issues ==

[[file::encoder_delay.png]]

The magnetic encoder is used to calculate motor (and robot) velocity. The velocity is estimated based on the time between encoder ticks.

← Older revision		Revision as of 15:48, 28 November 2024
Line 1:		Line 1:
	== Regbot encoder issues ==		== Regbot encoder issues ==

	~~The~~ Regbot motors use a magnetic encoder at the motor axle~~, as shown below~~.		As shown below, the Regbot motors use a magnetic encoder at the motor axle.

	[[file:regbot_encoder_delay.png \| 500px]]		[[file:regbot_encoder_delay.png \| 500px]]

	The encoder has 12 magnets and two HAL sensors. The sensors ~~have a~~ separation and position ~~that~~ should give symmetric A and B signals, as shown. If all magnet dipoles have exactly the same size and strength, then velocity can be estimated using the time between any two flanks. But this is not the reality.		The encoder has 12 magnets and two HAL sensors. The sensors' separation and position should give symmetric A and B signals, as shown. If all magnet dipoles have exactly the same size and strength, then velocity can be estimated using the time between any two flanks. But this is not the reality.

	A more stable velocity is obtained using the time between the same flank on the same signal, e.g. the rising flank on the A signal. This gives a velocity estimate at every flank, but the velocity is estimated over a longer time.		A more stable velocity is obtained using the time between the same flank on the same signal, e.g. the rising flank on the A signal. This gives a velocity estimate at every flank, but the velocity is estimated over a longer time.
Line 11:		Line 11:
	The average delay is half the time between two equal flanks on the same signal plus the time since the flank was detected.		The average delay is half the time between two equal flanks on the same signal plus the time since the flank was detected.

	The following plot tests this. A fast PI velocity controller ~~is used to obtain~~ stable velocities between 0.05 and 1.3 m/s. The motor gear is 9.6:1, and the wheel radius is 0.03m.		The following plot tests this. A fast PI velocity controller obtains stable velocities between 0.05 and 1.3 m/s. The motor gear is 9.6:1, and the wheel radius is 0.03m.

	[[file:encoder_delay.png \| 500px]]		[[file:encoder_delay.png \| 500px]]
Line 23:		Line 23:
	At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not equal or symmetric.		At 0.5 m/sec and faster, a repeating pattern is visible. This pattern is related to the velocity and is repeated for every motor rotation. This indicates that the magnets in the encoder are not equal or symmetric.
	In this case, the resulting velocity noise is about 10% of the velocity.		In this case, the resulting velocity noise is about 10% of the velocity.

			Much of this noise could be eliminated if the different sizes of the 12 magnets were estimated. Such a function is not implemented.