Design calculations - Revision history

Jca: /* Encoder calculations */

2024-11-28T13:42:18Z

Encoder calculations

← Older revision		Revision as of 15:42, 28 November 2024
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	Distance per tick = pi*0.06/464.64 = 0.40568 mm/tick		Distance per tick = pi*0.06/464.64 = 0.40568 mm/tick

	This type of encoder introduces some delay in the velocity estimate, see [[Regbot ~~velocity estimate~~]] for further details.		This type of encoder introduces some delay in the velocity estimate, see [[Regbot encoder analysis]] for further details.

	== Speed calculation==		== Speed calculation==

2024-11-28T13:41:37Z

Encoder calculations

← Older revision		Revision as of 15:41, 28 November 2024
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	This gives 48*9.68 = 464.64 ticks per wheel revolution, or		This gives 48*9.68 = 464.64 ticks per wheel revolution, or
	Distance per tick = pi*0.06/464.64 = 0.40568 mm/tick		Distance per tick = pi*0.06/464.64 = 0.40568 mm/tick

			This type of encoder introduces some delay in the velocity estimate, see [[Regbot velocity estimate]] for further details.

	== Speed calculation==		== Speed calculation==

2019-05-24T07:50:06Z

Speed calculation

← Older revision		Revision as of 09:50, 24 May 2019
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	If there is more than one encoder tick within 1ms, then the velocity is averaged over 1 ms. At lower speed the velocity gets updated at every tick time (fewer than one encoder tick in 1 ms).		If there is more than one encoder tick within 1ms, then the velocity is averaged over 1 ms. At lower speed the velocity gets updated at every tick time (fewer than one encoder tick in 1 ms).
	If time between encoder pulses is more than 0.5 sec, then speed is set to 0.		If time between encoder pulses is more than 0.5 sec, then speed is set to 0.
	If time since last encoder tick is longer than last encoder tick period, then velocity is based on time since last tick (up to 0.5 sec, where the speed is set to 0). I.e. the minimum speed measured is		If time since last encoder tick is longer than last encoder tick period, then velocity is based on time since last tick (up to 0.5 sec, where the speed is set to 0). I.e. the minimum speed measured is 2*0.0041 m/s = 0.81cm/sec.

	Sample time is (pt.) 1ms.		Sample time is (pt.) 1ms.

2019-05-24T07:47:47Z

Speed calculation

← Older revision		Revision as of 09:47, 24 May 2019
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	Speed is calculated based on time between encoder ticks		Speed is calculated based on time between encoder ticks

	At max speed there should be approx 4.48 encoder ticks per ms, or 223 us between tics		At max speed there should be approx 4.48 encoder ticks per ms, or 223 us between tics.
	~~The timing base~~ is ~~pt. 10us~~, so velocity ~~resolution~~ is ~~rather bad~~ at ~~high speeds~~.		If there is more than one encoder tick within 1ms, then the velocity is averaged over 1 ms. At lower speed the velocity gets updated at every tick time (fewer than one encoder tick in 1 ms).
	~~This may be improved by averaging if~~ time between encoder ~~edges~~ is ~~smaller~~ than ~~sample~~ time.		If time between encoder pulses is more than 0.5 sec, then speed is set to 0.
			If time since last encoder tick is longer than last encoder tick period, then velocity is based on time since last tick (up to 0.5 sec, where the speed is set to 0). I.e. the minimum speed measured is

	Sample time is (pt.) 1ms.		Sample time is (pt.) 1ms.

2018-12-31T08:16:26Z

2017-06-12T12:06:52Z

Speed calculation

← Older revision		Revision as of 14:06, 12 June 2017
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	This function currently disabled - gave problems while balancing.		This function currently disabled - gave problems while balancing.

	The motor controller has problems with low (and high) PWM values at the used 20kHz switch rate. This gives almost no motor power if PWM is less than 7-10%.		The motor big controller has problems with low (and high) PWM values at the used 20kHz switch rate. This gives almost no motor power if PWM is less than 7-10%.
	Lower switch frequency may give problems with audio noise and high peak current in anchor coils.		Lower switch frequency may give problems with audio noise and high peak current in anchor coils. The tiny motor controller has much higher BW, but noise from switching can give false encoder pulses, and thus there is mounted 1-4.7nF filter capacitors on the encoder lines.

	== Parameter estimation==		== Parameter estimation==

2017-06-12T12:04:13Z

Current consumption

← Older revision		Revision as of 14:04, 12 June 2017
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	On this robot the total anchor resistance is estimated to about 3.3 Ohm (including H-bridge and wires) based on current step response.		On this robot the total anchor resistance is estimated to about 3.3 Ohm (including H-bridge and wires) based on current step response.

	~~== Current consumption ==~~

	~~When idle (drive motors not running), the current consumption is approximately:~~
	* from 12V: 60mA, 35mA if teensy is in deep sleep mode.
	* from 7.5V: 80mA.
	* from 5V: 120mA.
	~~This is to drive the Teensy 3.1 at 96MHz, the buck-boost converter and the motor controller with output disabled.~~
	~~From 5V~~

2017-05-28T06:04:09Z

Maximum speed

← Older revision		Revision as of 08:04, 28 May 2017
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	This gives a max speed of 5600/60/9.680.06Pi = 1.8m/s		This gives a max speed of 5600/60/9.680.06Pi = 1.8m/s

			(with a maximum motor voltage of 9V should - for short periods - allow up to 2.7m/s).

	== Encoder calculations==		== Encoder calculations==

2016-01-14T13:46:57Z

Current consumption

← Older revision		Revision as of 15:46, 14 January 2016
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	When idle (drive motors not running), the current consumption is approximately:		When idle (drive motors not running), the current consumption is approximately:
	* from 12V: 60mA,		* from 12V: 60mA, 35mA if teensy is in deep sleep mode.
	* from 7.5V: 80mA.		* from 7.5V: 80mA.
	* from 5V: 120mA.		* from 5V: 120mA.
	This is to drive the Teensy 3.1 at 96MHz, the buck-boost converter and the motor controller with output disabled.		This is to drive the Teensy 3.1 at 96MHz, the buck-boost converter and the motor controller with output disabled.
	From 5V		From 5V

2016-01-14T13:45:30Z

Parameter estimation

← Older revision		Revision as of 15:45, 14 January 2016
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	Pololu say that at 6V stall current is 2.2A, or R_A = 2.7 Ohm		Pololu say that at 6V stall current is 2.2A, or R_A = 2.7 Ohm

	On this robot the total anchor resistance is estimated to 3.3 Ohm (including H-bridge and wires) based on current step ~~responce~~.		On this robot the total anchor resistance is estimated to about 3.3 Ohm (including H-bridge and wires) based on current step response.

	== Current consumption ==		== Current consumption ==