Axis jumps when initializing (BAD)

[Perryg114]

I am doing some motion control using a PCI-7344 control card and a third party servo motor drive. It is configured for velocity mode. I am initializing the 7344 card in a Labview program and more often than not there is a big jump of the axis when I do this. This jump is causing shaft couplers to slip and now my position is off. There must be a way to eliminate this jump. I have tried to adjust the tuning parameters so the servo is well damped with very little overshoot. This seems to have no effect. How to I do a soft initiazation that won't wring things off?

Perry

[Perryg114]

I found the problem. The jump occurs when a limit switch that enables the axis is tripped. Evidently enabling and disabling the axis causes it to jump eventhough it is not being commanded to move when this happens. I am dealing with another problem that causes the motor to move off zero when it is commanded to go to zero.

When I reset the encoder counts to zero and then command the motor to go to zero, the motor moves off zero. The position vi is in absolute mode.

Perry

[Perryg114]

Actually, initializing the axis does cause a problem if the motor is freewheeling when it happens. This is probably a problem unique to servos in velocity mode. So I am finding that I have to disable the axis then initialize the axis then enable the axis.

Perry