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stepper motor smooth running ...

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jit_singh_tara

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Hello friends,

Can we have a discussion on how do we implement the smooth acceleration and deceleration of stepper motor.
I have seen the videos on youtube that all the stepper motor used in professional machines like wire cutting and stripping , other high speed stepper driving projects , that they run very smoothly after starting they slowly accelerate and similarly they decelerate before stop .they run at a very high speed.I want to know how do they implement this algorithm that is when should the timing between pulses be increased or decreased .do they count the pulses for changing the time between them:

For example ;

do they count pulses before changing the time between the pulses or what.Doesnt this method gives some kind of a jerk to motor?

any knowledge regarding how to implement this thing in professional and actual way would be helpful.


Thanks and regards
Jitender Singh
 

FvM

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Apart from smooth appearance, ramps are required to avoid getting out of step. It refers to the maximum torque versus step frequency curve and inertia of the stepper motor and connected load. You can calculate maximum fast acceleration and deceleration ramps from this data. Or acquire them by test, if you are missing the information.

Preferably, the step-to-step time interval will be changed for each step for a smooth ramp. The time delta can be read from a table or calculated.
 

ayhampic

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hi ,
actually , I have the same problem in dealing with a stepper smoothly , but I've discovered that if you want to use smooth rotation you should use 'Micro stepping' , it makes the movement smooth , but it doesn't affect on accuracy in lower speed.
you can achieve what you want by using a stepper motor drivers (expensive ) or check :

PIC Linear Stepper Motor Controller
Microstep
Stepper Motor Microstepping Tutorial - a knol by Zaber Technologies

the whole problem represents in sending the current gradually through the windings
regards
 

audiomik

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Did a design some years ago which required 'smooth' running in half step mode of an 8 pole stepper motor for tape transports which needed to be synchronised to film and have very minimal step 'jitter'.
The most effective results were using switched current limited sources for each pole.

Unfortunately I don't have the circuits for this any longer but the principle used should be easy to work out.

apology for limited information
Mik
 

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