Re : MAX direction reversal

[henradrie]

Whenever I use Labview MAX past a certain velocity the servo will move in the opposite direction I intended and a following error will result. For example whenever I set the axis to move too 1500 counts at 1000 counts/s it moves in the negative direction instead of to 1500 counts. However when I slow it down it behaves correctly. 

This behavior even happens when I jog it. No matter which direction I jog the system will go in the opposite direction of what I specified. 

I've tried my usual fix of switching the motor wires but that didn't work. What else can I do to solve this problem.

[ben64]

When the motor is moving in the opposite direction, is it moving at 1000counts/sec or slower. Have you check how the counts/sec value relate to RPM and what is the maximum RPM of the motor? Are you using a DC or stepper motor in the servo?

Ben64

[henradrie]

The motor moves 1000 counts/sec when going in the opposite direction. I don't have any information on the motor so I can't check if I have reached the maximum RPM. However, I can run the motor at higher power levels such as 2000 counts/sec just fine so I assume that 1000 count/sec is reasonable. The motor in the servo is a simple DC motor.

Here are some other facts that might prove useful.

There are no limit switches, movement is relative to the previous position.

The encoder isn't connected to the same shaft as the motor, there is a speed reducing gear train between them.

There is a significant amount of backlash in the servo mechanism.

[ben64]

The only thing I can thing of is that your system is unstable at this velocity. Try playing with the control loop settings.

Ben64

[henradrie]

Do you think installing a larger motor would have a positive effect and help eliminate the problem?