Halt causes jerk movement

[Tammy]

Using PCI-7344 and MID-7604 and FLEXMOTION.
3-Axis control, stepper motors, closed loop with optical linear encoders.

1) When I am stationary and command a Halt, there is a resulting jerk movement, sometimes up to a few 1000 servo steps. Why?

2) The MAX PID Tune does not work at all. Is there a way to use the LabView PID VIs, including the Auto-Tune VI to tune the PID parameters? Do you have an example or documentation on how to do this?

3) I am having trouble with getting the move complete to complete. I realize one factor is the PID parameters. I have attempted to tune them manually with the Capture and Read Trajectory data (this is a very cool tool) but so far am not very successful at finding the correct PID parameters. Can I get more documentation on what factors are included in the move complete.

4) The pull-in moves at the end of the move do not appear to be limited by the commanded velocity and acceleration. Using the high rate data, I am often seeing velocities 4-5X the defined velocities, which then would throw-off the PID controller. Is this a design flaw? Why is this? The pull-in moves are usually completely un-successful at correcting the endpoint.

5) I am using a 3-D contour move to perform a curve. To define the geometery of the move, I need about 170 points. I would like the speed of this move to be approx 6000 steps/second. Due to the definition of the speed of a contour move to be dependant on the following parameters:
1) Distance between points
2) Time delay between points, limited to intervals
of PID rate which can be btwn 10-45 msec for the
fastest PID rate, or btwn 10-90 msec for slowest

This requies me to have a contour defined as 3500 points. This is a big drain on the system due to this restriction.
1) Why is this restriction here? Is there an work around?
2) When you change the PID update rate, what does that effect? High speed capture rate? All card processing?
3) There does not appear to be a way in LabView to change the PID rate? Am I missing it?

[algames]

This is a bit confusing. Are you suing steppers or servos? Stepper motors can not be tuned. They are discrete systems that do not require the board PID loop to be controlled. How many times are you calling halt in a sequence. Halt should only be called once duirng any motion move as it takes the position at the time it is called as the new target position of the trajectory. If your encoders are noisy every time you hit halt the position might be different and that's where the jump is coming from. Otherwise the first time you hit halt the motor should stop and hold position. No new calls to halt should be done unless a new move has been started or the axis gets killed. To poperly deinfe the velocities and accelerations for your move I would recommend using Motion Assistant
. this is a tool that lets you design your move from a higher level (accel-velocity-decel) view and then generate the contouring array for your move. The PID rate will affect stepper motors as it basically determines whether a move between two consecutive points within the requested interval is possible or not. refer to the NI-Motion software reference manual for help on determining this interval.Motion Assistant takes care of this for you so that you don't need to calculate this interval for every two points in your contour.