Searching \ for '[PIC]:PIC12F675 Servo motor wobble problem' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: piclist.org/techref/microchip/ios.htm?key=motor
Search entire site for: 'PIC12F675 Servo motor wobble problem'.

Exact match. Not showing close matches.
PICList Thread
'[PIC]:PIC12F675 Servo motor wobble problem'
2012\05\22@231106 by yamanoor sairam

picon face
Hello All,

I had written to the list long time back regarding the drive of servo motor using a potentiometer and a PIC12F675. I was successful in doing driving the same. I got back to working on this project and I am happen to face a new problem.  

When there is no load on the motor, it works perfect. When I load the motor, it keeps wobbling. I think the motor is not able to drive the load or there is a small slippage that is causing the problem. All I wanted to do was that the motor should rotate between 90 and 180 degrees when a switch is toggled.

Should I just switch off the motor when it is near the desired position? It looks like the motor has reached 3 degrees and trying to correct the angle and slipping off to -3 degrees. It keeps repeating this cycle.

 I am posting a snippet of the code:

 if(GPIO & (1<<3))
                   {
                   if(servoVal>=(1499))
                   {
                    servoVal = servoVal-(quotient*10);
                    }
                   // do_servo();
                    }
                 else         if(!(GPIO & (1<<3)))
                                {
                                if(servoVal<=(2300))
                                {
                                servoVal = servoVal+(quotient*10);
                                 }
                                  //do_servo();
                                }

Sai

2012\05\23@003951 by Mike Hord

picon face
It does sound like you have a load problem. Can you reduce the load through
any mechanical means?

"Turning off" the motor is probably not a good solution- it'll lose all its
holding power at that point and
you'll likely be worse than you were.

Mike H.

On Tue, May 22, 2012 at 9:11 PM, yamanoor sairam <spam_OUTyamanoorsaiTakeThisOuTspamyahoo.com>wrote:

{Quote hidden}

>

2012\05\23@005655 by Bob Blick

face
flavicon
face

It sounds like the refresh rate is not fast enough.

Best regards,

Bob

On Tue, May 22, 2012, at 08:11 PM, yamanoor sairam wrote:
{Quote hidden}

--
http://www.fastmail.fm - Faster than the air-speed velocity of an
                         unladen european swallow

2012\05\23@010005 by Sergey Dryga

flavicon
face

yamanoor sairam <yamanoorsai <at> yahoo.com> writes:

>
> Hello All,
>
> I had written to the list long time back regarding the drive of servo motor
using a potentiometer and a
> PIC12F675. I was successful in doing driving the same. I got back to working
on this project and I am happen
> to face a new problem.  
>
> When there is no load on the motor, it works perfect. When I load the motor,
it keeps wobbling. I think the
> motor is not able to drive the load or there is a small slippage that is
causing the problem. All I wanted to do
> was that the motor should rotate between 90 and 180 degrees when a switch is
toggled.

It sounds like the generated pulse width is not stable, check the duration of
the pulse.  I had similar problem when an interrupt unrelated to pwm generation
was firing at random time with respect to the pulse, which resulted in slightly
variable pulse width.  

Sergey Dryga
http://beaglerobotics.com

2012\05\23@065419 by Isaac Marino Bavaresco
flavicon
face
Servo control is not that simple, there a lot in control theory that you
must deal of.
Closed loop instability is common and you must address it with a more
sophisticated algorithm.
It seems that a PID controller may be better suited for your problem.

Have you tried to add a dead-band to your logic (simply tolerate the 3
degree error. If the position is inside the 3 degree band, then stop
trying to correct it).


Isaac



Em 23/5/2012 00:11, yamanoor sairam escreveu:
{Quote hidden}

>

2012\05\23@070651 by yamanoor sairam

picon face
Thanks for all the replies. I am yet to test the suggestions though I have made the changes.

I soldered the board for a statics mechanics class. We design bridges and provide loads using the servo. When the bridge is lighter, the servo wobbles vigorously. 

This is not seen when the bridge is heavy.

Sai


{Original Message removed}

More... (looser matching)
- Last day of these posts
- In 2012 , 2013 only
- Today
- New search...