Can we change the Constraints in MPC ?

Hello,

I'm using the Online feature of mpc block .i.e varying the MV constraints with simulation time.

Is it posible to change the inequality of the constraints in mpc block in matlab/simulink?

For example:

If ECR values (V) is 0 and scale factor is 1, then

default constraint is : u_min <= u <= u_max

and I would like to change to : u_min < u < u_max

Answer 1

[Sam Chak]

Hi @Kripanshu

If you wish to define the bounds on the manipulated variable, u, such that , can you accept the following workaround?

umin  = -1;         % lower bound
umax  =  1;         % upper bound
delta = 0.0001;     % user-defined, ideally should be eps(1) for double precision
MV    = struct(Min = umin+delta, Max = umax-delta)

MV = struct with fields:
    Min: -0.9999
    Max: 0.9999

[Kripanshu]

Hi @Sam Chak,

Thanks for your answer.

This would work in my case by adding a Bias block, but I was looking for some other alternative option.

Because if I use delta in my case, then i have to iterate it to get optimum value according to the model and add other block like switches to make it work.

[Torsten]

If ECR values (V) is 0 and scale factor is 1, then

default constraint is : u_min <= u <= u_max

and I would like to change to : u_min < u < u_max

Strict constraints ( >, < ) cannot be imposed in any kind of optimization.

Consider the simple example

min: x
0 < x < 1

I think you are able to see the problem.

[Kripanshu]

Hi @Torsten,

Thanks for your answer.

I understood the problem with this example

[Sam Chak]

Hi @Kripanshu

I'm not familiar with the specifics of your MPC implementation. When you mentioned performing iterations on the delta to get an optimum value according to the system model and adding other blocks like switches to make it work, this sounds more like an optimization problem rather than a generic MPC problem.