feedback control in simulation loop?

[Vss]

Hi,

I have a very basic question. we are gonna implement our control scheme to our system,
in short, we use DAQ card to get input from encoders and touch screen, after that we get
the error and then send it to the controller to generate the desired behavior of the
actuator, a very typical feedback control system. We don't have anything like FPGA so we
merely use the computer as the controllers. In this case, is it fine to build the system
block diagram and then implement it to our system in a simulation loop? Do we need to use
anything like Real-time module? The reason why i am puzzled is that the time in a
simulation loop is simulated time rather than real time, and we are also gonna need to
use some indicator to monitor the value variation when the system is running in real
time. so i am not sure if it's fine to use it to control a real system. Thanks a lot!!

XIaofei

[Barp]

XIaofei

The Simulation Loop is capable of syncronizing to a internal or external time source, similar to what Timed Loops are capable of doing. In this case, you just need to deselect "Software Timing" (LabVIEW Simulation 8.0 and 8.2). In doing that, your euler integrator with have better was to perform the controller.

Now, the Real-Time module will help you to avoid your controller to get stuck if the Windows machine hang or if your system would start doing something like defragmentation or accessing another high priority task. As you know, the RT module tries to guarantee the sampling time with as less jitter as possible.

Since you are only interested in developing a controller, the LabVIEW Control Design Toolkit 2.1 (and later) has the capability of implementing discrete controller based of state-space, transfer function or ZPK. To use that, you just need to discretize you controller with functions like "Continuous to Discrete" and upload the result into the implementation VI. In doing this, you can use the Timed Loop to control timing.

Hope this helps.