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Stepper Motor acceleartion

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Raghu

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stepper motor dynamo

I am using a 2.75Nm rated ( Pull out torque ) bipolar stepper motor. This has a winding resistance of 2.3 Ohms per phase; Rated current of 2 Amps / Phase. and Inductance of 14mH/Phase.

I am using the L297 + L298 combination driver as a bipolar chopper for driving the motor in full step mode. The supply is at 12V / 10 A rating.

I am unable to achieve the quoted torque if I increase the clock frequency beyond 500Hz and the motor just stalls. ( the motor data sheet shows the torque drooping only after 1000 Steps/ sec) . The load is just frictional and not inertial.

I currently use a clock source that can be varied between 100 to 1500 Hz but not ramping it . I am told that if I apply the clock with a ramp from 0 Hz to 1000 Hz in a time of say 0.5 Sec, then the stepper will support 2.75 NM at 1000 Hz.

Kinldy advise if my information on ramping the frequency is correct.

( If so I can then use the 555 clock source as a VCO and ramp the frequency )

Thanks.

Raghunathan
 

Raghu

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stepper motor acceleration ramp

Dear Solvarg,

Thanks for the link. It IS useful.

Bye

Raghu
 

mdamdam

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acceleration ramping stepper motor

You motor seems to be made for constant I driver.
Also it is important to build a trapezoidal curve of speed and make some tests ( depend of the charge ) .
Otherwise you will have the same problem for stopping it.
M
 

Raghu

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Yes. I had already switched over to a trapezoidal profile for the clock frequency for starting-running -stopping. Performance is better and close to the data sheets.

Raghu
 

bunalmis

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You must increase the L298 voltage. 12V too low.
 

mgajo

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You can't get 2.75Nm with L298
8) bye
 

cbsirio

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Hi,
when you are using stepper motors, you have to pay attention to several points:
1) look at Voltage: a stepper motor function as a dynamo, and it is speed-related : more is the speed, more is the "dynamo" effect. In this way the torque decrease, so you have to get a more high voltage.
2) have a look to acceleration: you can't go without ramping to the maximum speed!
3) look at half-step/full-step : it also influence the torque.

HTH Sirio
 

lollobrigido

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your acceleration ramp depends upon the mass to move.
However for non too small stepper motors, 0-1000 hz in .5 s is a too higer acceleration, try in 1 sec.
If you want much more torque and a finest step, use the microstep method.

Lollo
 

hobbymat

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Try to increase your supply voltage to 36 volts (about the practical maximum for L298). More voltage means more maximum speed to your stepper.

Another thing to consider is that a stepper alone can't usually rotate very fast, as it needs something as a load to damp the resonant vibrations. A little friction on the shaft or mechanism won't do any harm - on the contrary.

And of course, the acceleration must be related to the voltage used and the inertia of the system. And remember to use a very even pulse stream, as an uneven stream of pulses is seen as a quickly varying speed command by the stepper, which it may or may not be able to obey.

I think that you'd better use two L6203 drivers instead of one L298. The former is a FET based driver that runs cool and can deliver more current than the latter. Usually the reliable maximum current for L298 is about 1.5 amps, with more current it usually fries to death, regardless of the heatsink. Besides, it's slowly becoming an obsolete component.

BTW: I think your motor's rated torque is 2.7 Ncm, not 2.7 Nm...



Happy stepping,

Hobbie
 

nebisman

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dear friends,..

I need information about stepper motor dynamic models and software for simulate it. Please an advice or link related

thanks in advance
 

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