Multistage MPC?

charleskhazoom · November 1, 2022, 4:37am

Hi,

Is it possible to use time-varying dynamics and constraints along the MPC horizon with acados?
Like a multistage MPC ?

FreyJo · November 2, 2022, 10:05am

Hi Charles,

in C this is for sure possible, i.e. you can use a separate nonlinear function for every shooting node (cost constraints) / shooting node gap (dynamics).
In the high-level interfaces (Python, Matlab, Octave), it is only possible by setting different parameters for some shooting nodes.

charleskhazoom · November 12, 2022, 12:14am

Hi,

is there an example where I can give different values of a parameter for different stages (matlab interface) ? For instance, to modify a constraint at different stages ?

Thank you,

Charles

FreyJo · November 14, 2022, 12:43pm

Here is an example:

github.com

acados/acados/blob/78eec1f0012c05a21b90f8907bb64e5f4c02248e/examples/acados_matlab_octave/wind_turbine_nx6/example_closed_loop.m#L380


      
          for ii=1:n_sim
          
          
%    fprintf('\nsimulation step %d\n', ii);
          
          
    tic
          
          
    % set x0
              ocp.set('constr_x0', x_sim(:,ii));
              % set parameter
              for jj=0:ocp_N-1
                  ocp.set('p', wind0_ref(:,ii+jj), jj);
              end
          
          
    % set reference (different at each stage)
              for jj=0:ocp_N-1
                  ocp.set('cost_y_ref', y_ref(:,ii+jj), jj);
              end
              ocp.set('cost_y_ref_e', y_ref(1:ny_e,ii+ocp_N));
          
          
    % set trajectory initialization (if not, set internally using previous solution)
              ocp.set('init_x', x_traj_init);

Cheers!