Post by thread: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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Mon, 5 Aug 2002, Francisco Ares wrote: >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. For each 'step' of acceleration you compute Time1 = Time0 - dt and set the timer to that. dt is set previously = (Starttime - Fasttime)/Numsteps, where Numsteps is the number of intermediate speeds you need and Starttime a timer value that corresponds to a minimum safe starting speed. When Time0 == Fasttime you have arrived to max speed. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 removed}