3D vector space with 2 open loop and 1 closed loop stepper motors

[Tulio]

Is possible to have two open loop e one closed loop stepper motors in a 3D vector space using contouring mode ?

I'm getting following error in the closed loop axis in some trajectories when using contouring mode (I'm using Motion Assistant's contouring mode). But if I use cycle mode for this axis in Max, with the same parameters (velocity, acceleration, following error value etc), using the same amount of steps that causes the problem in Motion Assistant, it just work fine !

Thanks !

[ColinAE]

Hello.

I have done some experimentation with MAX, LabVIEW, and Motion Assistant, and have found that indeed you should be able to have mixed-type stepper axes in a vector space. I have triend only 2D vector spaces, but I am able to run straight line and contour moves in MAX, LabVIEW using the shipping examples, and in Motion Assistant. I did not receive any unsuspected following errors (NI-Motion 6.1.4 and Motion Assistant 1.2), which means that this should be possible

When you get the following error, do you notice that you 'should' be getting the error (i.e. does the trace/feedback indicate that the motor is not in following error range?) or does the error happen without a good reason?

If you have not tried, I would make sure that you can make a simple straight line move with this vector space, both in LabVIEW (if possible) and in Motion Assistant.

Regards,
Colin C.
Applications Engineering

[Tulio]

Hi Colin,

answering your questions:

1) When I get the follow error the encoder reading is at the following error limit or above this limit. But the follow error doesn't happen if I use this axis alone.

2) I can perform a single straight line and more complex splines shapes. But in this particular shape I'm getting following error that shouldn't happen.

I have done more experimentations too ...

I put encoders in the other two axes (X and Y), and configured to closed loop. Then I run the same data points with the same parameters in Motion Assistant. It work !
Next, I configured the X and Y axes to open loop (keeping the encoders in place and wired to UMI). It work too !!!!
But when I disconnect the X and Y encoders lines from UMI it stop working and I get back the following error at the same position in my data points !

Why this happens ?

I'm attaching my MAX configuration and Motion Assistant file so you can a take a look and try to reproduce the problem at your lab.

Thanks !

[ColinAE]

Hello again.

This definitely sounds like strange behavior. I believe we need a few more clarifications to proceed:

1. When you say But the follow error doesn't happen if I use this axis alone., does this mean that the error is not generated, even though the feedback indicates that there is a problem, or does it mean that the feedback works properly when you use this axis alone?

2. When you are doing the "more complex shapes", do you stay within the following error limits?

Here is my fundamental question: When you have the axes configured as 2 open and 1 closed loop, and you are performing moves, does the closed loop axis correctly display the feedback, or does it remain at 0?

The behavior you described where it works when you have the encoders hooked up is very strange indeed! Again, what does the trajectory feedback info look like in each of these situations? You can look at it in the Step Status tab of Motion Assistant as the step is in progress.

Regards,
Colin C.
Applications Engineering

[Tulio]

Hello Colin,

1)If I use the axis alone in MAX:
- Interactive -> 1-D Interactive;
- Main -> cycle mode;
- Target Position = short moves (for example, 5 or 20 steps);
- Following error = 20;
In this situation the following error read by the feedback are well bellow the configured threshold error (usually 1 to 3 steps). The feedback for this axis is working properly.

2) Yes, except for that shape in the Motion Assistant file that I sent.

3) In the case of 2open and 1 closed, the feedback for the closed loop is reporting correct values. Equal or grater than the value set for the following error.

4) When the encoders are hooked up (no matter if the 2 axes are configured as open or closed loop), the feedback values reported are bellow the following error threshold.