Closed loop control with positional feedback

Hi,

Is there any way that i can control a stepper motor with pwm input for a positional feedback without any extra sensors like encoders?

Thanks

NST1992: Is there any way that i can control a stepper motor with pwm input for a positional feedback without any extra sensors like encoders?

You mentioned without 'extra' sensors. So it will probably depend on what sensors are currently being used.

Im using 9 dof sensor to measure the angle on a stabalising platform, however the 9 dof will not be mounted on the platform so the 9dof could not be used to correct the error itself.

NST1992: Im using 9 dof sensor to measure the angle on a stabalising platform, however the 9 dof will not be mounted on the platform so the 9dof could not be used to correct the error itself.

I see. So this like using a glass thermometer for the purpose of measuring the temperature of water contained in a cup, but the thermometer isn't allowed to touch that particular cup of water in any way (or be anywhere near that cup of water)?

1) Stepper motor is open-loop control - you don't need sensors 2) You don't drive steppers with PWM. 3) If you need feedback, you can't use just open-loop control - in other words a stepper isn't giving you anything useful

How do you determine the attitude of the platform?

(I read that too quick, and saw "How do you determine the attitude of the forum?" and I was thinking, "generally snarky!")

MarkT: 1) Stepper motor is open-loop control - you don't need sensors 2) You don't drive steppers with PWM. 3) If you need feedback, you can't use just open-loop control - in other words a stepper isn't giving you anything useful

I guess that a feedback sensor can at least indicate (immediately and accurately) a shaft position if say an absolute encoder is used. It probably depends on application - whether or not sensors are going to be required or going to be beneficial. And 'chopping' a voltage to provide a particular level of average current is like PWM.