7344 Motion board stop command causing system to drop

[bdpudlo]

I have a hydrolic system(in closed loop mode) controlled by a 7344s analog output.

a value changes depending on the voltage from the 7344:

positive voltage lets water into the system

negative voltage lets water out of the system.

due to the design of the system, water has to be constintly fed into it to hold position.

Now if I call a stop command while holding position(encoder counts are not moving) the voltage drops to zero before going back to its previous value(1-1.5v) only issue is that the system drops until the voltage gets back up.

In contrast, a halt stop is immediate and abrupt. The target position is set to the position of the axis at the moment the VI is executed. On servo axes, full torque is applied to stop the motor(s) as quickly as possible. On stepper axes, the step pulses are immediately ceased.

I am using a halt stop(1) would a decelerate stop(0) be better for this application?

[s_a_s]

The behavior you are describing sounds like the response of a halt stop when a following error exists in a closed loop stepper.  When a halt stop is performed on an axis the following error is cleared and the holding force on the motor is removed.  This is a known issure for NI-Motion drivers prior to 7.2, and is fixed in that release.  You can download the NI-Motion 7.2 driver here:


NI-Motion Version 7.2 for Windows 2000/XP
http://digital.ni.com/softlib.nsf/websearch/a38d3ad4a8b0f200862570f100758773 

[bdpudlo]

Thank you for your response.

I tried a decelerate stop and it produced the same effects.

We aren't using a stepper motor but a value(which acts like a servo motor) would the responeses between the two(servo vs stepper) be the same?

~Bryan

[s_a_s]

Yes,  The same holds true for servo motors.  The following error is cleared on a Halt Stop in versions prior to 7.2.