Dynomotion

Group: DynoMotion Message: 9905 From: daveymahomh600e Date: 8/4/2014
Subject: DC Servo Current Measurement
Hi Tom,

I know there is a way using a SnapAmp to monitor the currents within 3 phase brushless servos to determine when they are against an obstacle. Is there a way to do this with a brushed DC servo as well?

Also, in your example setup of DC brushed servo motors here... http://dynomotion.com/Help/ExampleConfigurations/BrushServoSnapAmp.htm it seems the "pwmc" can be set to drive these DC motors with a certain power. Is this what that variable does? Can it be set for each axis individually within the init file?

Thank you in advance,
David.

 
Group: DynoMotion Message: 9912 From: Tom Kerekes Date: 8/5/2014
Subject: Re: DC Servo Current Measurement
Hi David,

Yes it is possible to monitor currents.  See the example:

<>\C Programs\SnapAmp\SnapAmpCurrents.c

The "pwmc"commands is used to set a current manually to some value.  I don't think that is what you want to do.  The "Output" of the Servo loop is what commands the current to the motor.  By setting the MaxOutput for the axis you can control the Max Current that will ever be commanded.

HTH
Regards
TK





From: "david.m.stevenson@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Monday, August 4, 2014 1:05 PM
Subject: [DynoMotion] DC Servo Current Measurement

 
Hi Tom,

I know there is a way using a SnapAmp to monitor the currents within 3 phase brushless servos to determine when they are against an obstacle. Is there a way to do this with a brushed DC servo as well?

Also, in your example setup of DC brushed servo motors here... http://dynomotion.com/Help/ExampleConfigurations/BrushServoSnapAmp.htm it seems the "pwmc" can be set to drive these DC motors with a certain power. Is this what that variable does? Can it be set for each axis individually within the init file?

Thank you in advance,
David.
 
Group: DynoMotion Message: 9913 From: David Stevenson Date: 8/5/2014
Subject: Re: DC Servo Current Measurement
Hi Tom,

I looked at that currents program but wasn't sure how to apply the values.

In regard to the pwmc, I noticed when I was moving the 2 axis that one seemed to move easier than the other and by changing the pwmc value I could make them move about the same. I guess that once the SnapAmp is in control it will adjust the current to provide the desired motion.

Thanks for your help,
David.

On 8/5/2014 3:00 PM, Tom Kerekes tk@... [DynoMotion] wrote:
 
Hi David,

Yes it is possible to monitor currents.  See the example:

<>\C Programs\SnapAmp\SnapAmpCurrents.c

The "pwmc"commands is used to set a current manually to some value.  I don't think that is what you want to do.  The "Output" of the Servo loop is what commands the current to the motor.  By setting the MaxOutput for the axis you can control the Max Current that will ever be commanded.

HTH
Regards
TK





From: "david.m.stevenson@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Monday, August 4, 2014 1:05 PM
Subject: [DynoMotion] DC Servo Current Measurement

 
Hi Tom,

I know there is a way using a SnapAmp to monitor the currents within 3 phase brushless servos to determine when they are against an obstacle. Is there a way to do this with a brushed DC servo as well?

Also, in your example setup of DC brushed servo motors here... http://dynomotion.com/Help/ExampleConfigurations/BrushServoSnapAmp.htm it seems the "pwmc" can be set to drive these DC motors with a certain power. Is this what that variable does? Can it be set for each axis individually within the init file?

Thank you in advance,
David.
 
Group: DynoMotion Message: 9920 From: Tom Kerekes Date: 8/6/2014
Subject: Re: DC Servo Current Measurement
Hi David,

That would make sense if there was some sort of offset.

You are correct.  When the Servo is enabled it is constantly writing pwmc values to SnapAmp.

Regards
TK

Group: DynoMotion Message: 9921 From: David Stevenson Date: 8/6/2014
Subject: Re: DC Servo Current Measurement
Thanks Tom.

With regard to the current measurement, with brushless motors we compared the currents in the A and C phases, did some filtering and determined the axis had stopped. Can I simply watch the amps in the SnapAmp buffer with the brushed motor and call it done when the value exceeds a certain limit?

Thank you,
David.

On 8/6/2014 5:07 PM, Tom Kerekes tk@... [DynoMotion] wrote:
 
Hi David,

That would make sense if there was some sort of offset.

You are correct.  When the Servo is enabled it is constantly writing pwmc values to SnapAmp.

Regards
TK

Group: DynoMotion Message: 9926 From: Tom Kerekes Date: 8/7/2014
Subject: Re: DC Servo Current Measurement
Hi David,

Yes for brush motor there is just one value that is a measurement of the coil current (torque).  So no need to combine the phase like we did for the brushless motor.

HTH
Regards
TK


Group: DynoMotion Message: 9927 From: David Stevenson Date: 8/7/2014
Subject: Re: DC Servo Current Measurement
Thank you Tom.

I will give it a try today.

Best regards,
David.

On 8/7/2014 8:40 AM, Tom Kerekes tk@... [DynoMotion] wrote:
 
Hi David,

Yes for brush motor there is just one value that is a measurement of the coil current (torque).  So no need to combine the phase like we did for the brushless motor.

HTH
Regards
TK