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[DPRG] Driving an H-Bridge with a switching power supply

Subject: [DPRG] Driving an H-Bridge with a switching power supply
From: Rick J. Bickle rbickle at swbell.net
Date: Fri Dec 26 18:15:01 CST 2003

Kip,

Even though you have a feedback control system capable of compensating
for the lower voltage, wouldn't the response of the control system still
be reduced with a lower supply voltage? Take the example of David
Anderson's balancing bot - if with a full battery charge the controller
is capable of providing more power/time to the motors, it can then more
quickly compensate for deviations. With a lower battery voltage however,
the same power transfer requires more time, making the response more
sluggish.

Rick

-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of Kipton Moravec
Sent: Friday, December 26, 2003 2:33 PM
To: dprglist at dprg.org
Subject: RE: [DPRG] Driving an H-Bridge with a switching power supply


I disagree with everybody.  :)

I do not think a regulator on the input power to the robot is the
correct 
answer.

There is something wrong with your control loop if it can not compensate

for a battery slowly dropping voltage.  Of course if the battery drops 
enough then the system will not work with or without a regulator.

What you need with a regulator is more head room, so you end up
increasing 
the voltage of the battery pack so you can add a regulator.  If that
fixes 
the problem, then just add more battery voltage without the regulator.
The 
regulator is nothing more than another control loop.  They should be
able 
to be combined.

I really think the problem is that the control loop is too slow.  I
would 
recommend going from 25 Hz to 100 Hz or more.  When I talked to some 
control people they said they do PID for motors at 1000 Hz.

Kip   


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