MPC constraints - initial/final limits

[FelipeC]

What is the difference between initial and final limits of the constraints of LabVIEW MPC implementation? Are they the soft and hard constraints of classical MPC design? I could not find this information in the control design manual.

Thanks,

Felipe

[Abel_Souza]

Hi Felipe,

Your doubt is not so clear for me, but on LabVIEW Help said that its represent the initial and final limits of control action.

http://zone.ni.com/reference/en-XX/help/371894H-01/lvctrldsgn/cd_creatempc/

Regards,

[Barp]

Hello Filipe,

The Initial and Final Values are the constraints specified at the 'initial' and 'final' window of the 'control horizon' for the specific timestep. So, when you apply a timestep, the Controller will use the "Prediction Horizon" and the "Control Horizon" to define the next timestep and the initial and final constraits define the values used in the solver for that timestep.

In general, those values are the same and, internally, you just need to set one of the them and we will consider the limits to be the same.

The Constraints are 'soft' constraints. If you really need to enforce hard constraints on the output, you need to use a 'limiter' and feed the 'measured control action' to properly compute the values.

Here are some examples demonstrating what I said:

C:\Program Files (x86)\National Instruments\LabVIEW 2013\examples\Control and Simulation\Algorithms\Model Predictive Control (MPC)\CDEx Model Predictive Control for MIMO.vi

C:\Program Files (x86)\National Instruments\LabVIEW 2013\examples\Control and Simulation\Control Design\MPC\CDEx MPC Dual vs Barrier Constraints.vi