Trying to understand dimensions of state estimates output of MPC block in Simulink

I'm running an MPC in Simulink that was defined in a matlab script using the MPC Controller block and I want to inspect the state estimates of the observer which is the default input disturbance observer defined as follows:

setindist(mpcobj,'integrators');

The MPC model has 20 states:

>> size(mpcobj)
MPC controller with 4 measured output(s), 0 unmeasured output(s),
3 manipulated input(s), 0 measured disturbance(s), 3 unmeasured disturbance(s)

I wanted to check the state estimates so I selected the option to include them as an output.

However, the size of the state estimates vector is 24.

>> size(out.X_EST)

ans =

1501          24

I want to compute the estimated outputs (x3), so I need the C matrix for the observer model, which must be 3 x 24 presumably.

Whereas, the size of the plant model C matrix is 4 x 20:

>> size(mpcobj.Model.Plant.C)

ans =

4    20

What are the extra 4 states of the estimator and how do I compute the estimated outputs from these?

Answer 1

[Bill Tubbs]

I figured out that you can use the following to get all the parameters of the Kalman Filter including the augmented model used by the observer:

>> [L, M, A, Cm, Bu, Bv, Dvm] = getEstimator(mpcobj);
>> Cm * out.X_EST(end, :)'

ans =

6.8182
2.2083
1.2348
0.0001

Can I get this Cm matrix in simulink so I can calculate the output estimates during the simulation?

I couldn't find a way so I used a from-workspace block to get the precalculated Cm matrix and used it to copmute the output estimates like this. If anyone knows a simpler way, please let me know!