Part Number: DRV8811
Hello TI Team,
I was referring to the slyt482.pdf application note form Jose I. Quinones.
If i have to drive stepper motor for position control. Like in CAR Instrument cluster neddle use to move as per speedometer value.
1> So my question is it will be an position control application of stepper motor. Right ?
2> If suppose PWM register is 8 bit then i can divide full 360 degree sin wave cycle into 256 micro steps.
But instead of using of using 256 microsteps per full 360 degree cycle if i use 48 or 24 micro steps per full 360 degree cycle.
a> For 48 steps per full 360 degree cycle, there will be 48/4 = 12 micro step per full step, i.e 1 micro step = 1/12 full step.
b> For 24 steps per full 360 degree cycle, there will be 24/4 = 6 micro step per full step, i.e 1 micro step = 1/6 full step.
3> Now as per application note "Position control" section "Another option that may result in less tuning is to segment the total number of steps into percentages assigned to each particular region of the acceleration/deceleration profile" if i have to drive stepper motor of Speedometer from 10 Miles per hour to 40 miles per hour. And suppose moving needle from 10 Miles to 40 miles position in speedometer there has to be following electrical steps :--
a> If 1 micro step = 1/6 full step, then total number micro steps are 3000.
b> If 1 micro step = 1/12 full step, then total number micro steps are 6000.
5> Then to achieve smooth profiling as per application note, :--
1> If 1 micro step = 1/6 full step :--
a> Acceleration speed = 20 % of 3000 = 600, so till i reach 600 microstep level i will have to go at an speed of 600 microsteps/sec,
b> Target speed = 60 % of 3000 = 1800, i.e 1800 microsteps/sec till i reach 2400 microstep level,
c> Deceleration speed = 20 % of 3000 = 600, i.e 600 microsteps/sec till i reaches 3000 microstep level to stop the tepper motor.
2> If 1 micro step = 1/12 full step :--
a> Acceleration speed = 20 % of 6000 = 1200, so till i reach 1200 microstep level i will have to go at an speed of 1200 microsteps/sec,
b> Target speed = 60 % of 6000 = 3600, i.e 3600 microsteps/sec till i reach 4800 microstep level,
c> Deacceleration speed = 20 % of 6000 = 1200, i.e 1200 microsteps/sec till i reaches 6000 microstep level to stop the tepper motor.
Have i got the concept of setting acceleration speed & target speed & Deacceleration spped right in point 5 ?
For smooth profile in application like speedometer should i go for 1/6 or 1/12 full step ?
Regards,
Dinesh