I have come up with a perfect acceleration routine that works good for
me.  It allows me to get my steppers turning at 30rev/s

I use three timers.  One for the acceleration, one for a constant speed
after acceleration and one for a constant time interval of 1ms which I
use to update the acceleration timer.

On every 1ms interval, I increase accelerations timer values by 0x60
(30"/sec^2) of acceleration. Once, the acceleration timer value =
constant speed, then I disable timer 3, 0 and enable the constant speed
timer of

The acceleration value was calculated as follows:
30"/sec^2*0.001 = 0.03"/1ms
On my system 1" = 3200 steps so 0.03*3200 = 96 or 0x60.

So for every millisecond, I add 0x60 to the acceleration timer, until
it's value has reached the desired constant speed value of the
corresponding timer.

Regards,

James


-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Francisco Ares
Sent: Monday, August 05, 2002 5:25 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: stepper motor de/acceleration

Hi all PIClisters.

Can someone point me to an algorithim to do accelaration for a stepper
motor controller?

My controller uses one timer overflow ISR to switch the phases of the
motor, so the speed is calculated through the period register of this
timer.

I need to calculate different values for the period register for a
constant (or close to constant) acceleration, preferably "on-the-fly",
inside the same ISR.

My first atempts resulted in that the final speed was never reached
because of accumulating errors in calculations.

Any hints?

Thank you all.
Francisco

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