TIA - Controlling position of Stepper Motor

Grzesiuk · Feb 3, 2019

Hello,

thing that makes me wonder, its the situation when we move axis from one position to other position with CommandTable. For example, after homing with one sensor, and with conditions on CommandTable's execute input, we want to move axis from 0 to 4500mm, where the other sensor awaits. Axis starts to move, but due to some noises it may loose steps/position and will not reach the sensor (but will reach position 4500mm anyway, but before sensor or after). Is there some method to prevent this? Can we use HSC on one of the inputs, and connect PTO output signal to HSC input and measure it somehow to make precise position? How are managing such problem without encoder?

Steve Bailey · Feb 3, 2019

Connecting the pulse train output to a HSC will only confirm that you output the correct number of pulses. Slippage means the stepper motor failed to move a step for every pulse. Most slippage occurs during acceleration. Try reducing the acceleration rate.

kalabdel · Feb 3, 2019

Grzesiuk said:
Hello,

thing that makes me wonder, its the situation when we move axis from one position to other position with CommandTable. For example, after homing with one sensor, and with conditions on CommandTable's execute input, we want to move axis from 0 to 4500mm, where the other sensor awaits. Axis starts to move, but due to some noises it may loose steps/position and will not reach the sensor (but will reach position 4500mm anyway, but before sensor or after). Is there some method to prevent this? Can we use HSC on one of the inputs, and connect PTO output signal to HSC input and measure it somehow to make precise position? How are managing such problem without encoder?

Noise is used to mean so many things I'm not sure what you mean by it.

As Steve stated and from you description it looks like your motor moves/turns the number of steps it is commanded and not reaching its intended position has to do with mechanical issues which need to be identified and taken into consideration. Connecting the PTO output to an HSC will not add anything new as it will give you information you already have but adding an encoder for closed loop control maybe a solution if you determine , for example, that it is OK to continue to drive the motor at a slower speed after it has reached the 4500 pulsed but not yet reached the sensor.

Grzesiuk · Feb 4, 2019

I understand, its more clear to me now. Moving axis from 0 to 4500mm (thats just an example) give us some specify pulses. So if we set some position like 3000 and write it to MC_MoveAbsolute input, the axis will move to that position, and if we compare position of technology object (there is a Real variable "Position" in axis DB) and compare it to Pulses from HSC, the Position will be 3000, but pulses may differ everytime we go to that position, am I right? I am just wondering how to make certainty that whenever I set some position on the rail from 0 to x, axis will ALWAYS achieve that exact position.

BryanG · Feb 4, 2019

I am just wondering how to make certainty that whenever I set some position on the rail from 0 to x, axis will ALWAYS achieve that exact position.

Without a feedback system you never can be certain, you can only make it more likely. So if it ALWAYS has to be right then you MUST add an encoder to know the position.

TIA - Controlling position of Stepper Motor

Grzesiuk

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Steve Bailey

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kalabdel

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Grzesiuk

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BryanG

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