Configuring cogging torque compensation - Revision history

Esa at 10:35, 2 December 2016

2016-12-02T10:35:22Z

Tero K at 11:17, 28 May 2016

2016-05-28T11:17:29Z

Tero K at 23:28, 2 November 2015

2015-11-02T23:28:48Z

Tero K: /* Finding values */

2015-11-02T23:19:47Z

‎Finding values

Tero K: /* Finding values */

2015-11-02T23:18:35Z

‎Finding values

Tero K: /* Configuration */

2015-11-02T23:11:30Z

‎Configuration

Tero K: Created page with "[https://en.wikipedia.org/wiki/Cogging_torque Cogging torque] compensation feature in drive that aims to make motor torque production more uniform and ideal. ''"Cogging torq..."

2015-11-02T22:50:54Z

Created page with "[https://en.wikipedia.org/wiki/Cogging_torque Cogging torque] compensation feature in drive that aims to make motor torque production more uniform and ideal. ''"Cogging torq..."

New page

[https://en.wikipedia.org/wiki/Cogging_torque Cogging torque] compensation feature in drive that aims to make motor torque production more uniform and ideal.

''"Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. It is also known as detent or ‘no-current’ torque. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator.”''

This can be compensated by modulating motor current to counter the motor cogging. In some Granite Devices drives ([[IONI]] Pro family on the time of writing) there are options to adjust compensation current by few parameters.

{{picturebox|torqueCompensation.png|596px|caption=Cogging torque compensation parameters in Granity}}

==Configuration==
===Parameters===
Static no-current cogging compensation is done by summing a fixed amplitude waveform on the torque [[setpoint]]. The default waveforms are sinusoidal where phase angle of sine is driven by motor angle.
*{{param|TRF1}} - selects the function of compensator
*{{param|TRA1}} - adjusts the amplitude of summed torque command

Dynamic nonuniformity compensation helps to reduce torque ripple when non-zero current is being driven. The method of operation is same, except this time setpoint amplitude is modulated by scaling of torque setpoint instead of summing.
*{{param|TRF2}} - selects the function of compensator
*{{param|TRA2}} - adjust the modulation depth of compensator
===Finding values===
TODO

[[Category:IONI_user_guide]]
[[Category:Technology]]

@@ Line 26: / Line 26: @@
 As the frequency is known, we proceed choosing the correct function and amplitude setting:
 #Set drive in torque mode and enable it without any setpoint
-#Start with Sin(Nx) function and try different TRA2 values (positive and negative, varying magnitudes). On each TRA2 value, try rotating motor by hand and identify the lowest cogging setting.
+#Start with Sin(Nx) function and try different TRA1 values (positive and negative, varying magnitudes). On each TRA1 value, try rotating motor by hand and identify the lowest cogging setting.
 #Repeat the last step but this time with Cos(Nx) function.
 #Choose the settings that yielded the lowest cogging

@@ Line 23: / Line 23: @@
 #Divide this number by motor poles and multiply by two. So equation is N=2*number_of_cogs/pole_count (same as {{param|MPC}}.
 #The optimal TRF1 function is either Sin(Nx) or Cos(Nx). For example, if motor has 8 poles, and we feel 12 cogs per revolution, the value of N becomes 2*12/8=3. So in this case we would use Sin(3x) or Cos(3x) function.
 {{warning|These methods are done on user's own risk. Remember that any malfunction in software or hardware may cause unexpectedly high torque.}}
 As the frequency is known, we proceed choosing the correct function and amplitude setting:
@@ Line 34: / Line 33: @@
 {{machine|Beware of handling motor when torque setpoint is given. Always start with very low setpoint values to avoid injury or damage. Always keep emergency stopping method rapidly accessible.}}
 [[Category:IONI_user_guide]]
 [[Category:Technology]]

@@ Line 21: / Line 21: @@
 Determining cogging torque frequency is straight forward.
 #Rotate unpowered motor by hand count the number of major "steps" or "cogs" per revolution
 #Divide this number by motor poles and multiply by two. So equation is N=2*number_of_cogs/pole_count (same as {{param|MPC}}.
-#The optimal TRF1 function is either Sin(Nx) or Cos(Nx).
+#The optimal TRF1 function is either Sin(Nx) or Cos(Nx). For example, if motor has 8 poles, and we feel 12 cogs per revolution, the value of N becomes 2*12/8=3. So in this case we would use Sin(3x) or Cos(3x) function.
 {{warning|These methods are done on user's own risk. Remember that any malfunction in software or hardware may cause unexpectedly high torque.}}

@@ Line 18: / Line 18: @@
 ===Finding values===
 The first task is to determine the frequency of imperfections so we know which functions to start experimenting.
 Determining cogging torque frequency is straight forward.
@@ Line 25: / Line 24: @@
 #The optimal TRF1 function is either Sin(Nx) or Cos(Nx).
 As the frequency is known, we proceed choosing the correct function and amplitude setting:
 #Set drive in torque mode and enable it without any setpoint

@@ Line 1: / Line 1: @@
-[https://en.wikipedia.org/wiki/Cogging_torque Cogging torque] compensation feature in drive that aims to make motor torque production more uniform and ideal.
+{{#ev:youtube|Rp8YyCMY4vs|320|right|Cogging and anticogging explained.}}[https://en.wikipedia.org/wiki/Cogging_torque Cogging torque] compensation feature in drive that aims to make motor torque production more uniform and ideal.
 ''"Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. It is also known as detent or ‘no-current’ torque. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator.”''
@@ Line 5: / Line 5: @@
 This can be compensated by modulating motor current to counter the motor cogging. In some Granite Devices drives  ([[IONI]] Pro family on the time of writing) there are options to adjust compensation current by few parameters.
 ==Configuration==
 ===Parameters===
 Static no-current cogging compensation is done by summing a fixed amplitude waveform on the torque [[setpoint]]. The default waveforms are sinusoidal where phase angle of sine is driven by motor angle.

@@ Line 13: / Line 13: @@
 *{{param|TRA1}} - adjusts the amplitude of summed torque command
-Dynamic nonuniformity compensation helps to reduce torque ripple when non-zero current is being driven. The method of operation is same, except this time setpoint amplitude is modulated by scaling of torque setpoint instead of summing.
+Dynamic torque ripple compensation helps to reduce non-uniform torque when non-zero current is being driven. The method of operation is same, except this time setpoint amplitude is modulated by scaling of torque setpoint.
 *{{param|TRF2}} - selects the function of compensator
 *{{param|TRA2}} - adjust the modulation depth of compensator
 ===Finding values===
-TODO
+The first task is to determine the frequency of imperfections so we know which functions to start experimenting.
 [[Category:IONI_user_guide]]
 [[Category:Technology]]