Problem with passing parameters into system model

jcwj · December 19, 2020, 4:21pm

Hi everyone,

Thanks for developing this toolbox! I’m currently using acados through the MATLAB interface, and am facing issues when I try to pass a vectorial parameter into the system model. I’ve attached some test code to show what I mean.

The attached code implements a simple 3D kinematics model: the agent can move freely in 3D space, but must remain within the conical field-of-view of some cameras on the ground. At first, I hard-coded the camera position inside the dynamics model, and the optimization went well. However, when I tried to pass in the camera position as a model parameter - using the same position value - the NLP solver immediately failed with error status 4. Even so, the solver and sim models still compiled successfully.

In the code, you should be able to reproduce this issue by replacing lines 11-12 with line 10 in debug_model.m:

10  % cam_pos = [0;0;0.1];
11  sym_p = SX.sym('pm',3*num_cams,1);
12  cam_pos = reshape(sym_p,3,num_cams);

My apologies if the issue turns out to be trivial, and thank you in advance!

Best,
Jon

github.com

gitmon/acados_test/blob/main/debug_model.m

function model = debug_model(num_cams)

import casadi.*

%% dims

nx = 6;
nu = 3;

% cam_pos = [0;0;0.1];
sym_p = SX.sym('pm',3*num_cams,1);
cam_pos = reshape(sym_p,3,num_cams);

nobs = num_cams;       % TODO
halfFOV = deg2rad(45);

%% symbolic variables

x_pw = SX.sym('x',3,1);           % world position
x_vw = SX.sym('v',3,1);          % world velocity

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github.com

gitmon/acados_test/blob/main/debug_sim.m

%
% Copyright 2019 Gianluca Frison, Dimitris Kouzoupis, Robin Verschueren,
% Andrea Zanelli, Niels van Duijkeren, Jonathan Frey, Tommaso Sartor,
% Branimir Novoselnik, Rien Quirynen, Rezart Qelibari, Dang Doan,
% Jonas Koenemann, Yutao Chen, Tobias Schöls, Jonas Schlagenhauf, Moritz Diehl
%
% This file is part of acados.
%
% The 2-Clause BSD License
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% Redistribution and use in source and binary forms, with or without
% modification, are permitted provided that the following conditions are met:
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% 1. Redistributions of source code must retain the above copyright notice,
% this list of conditions and the following disclaimer.
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% 2. Redistributions in binary form must reproduce the above copyright notice,
% this list of conditions and the following disclaimer in the documentation
% and/or other materials provided with the distribution.
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FreyJo · December 21, 2020, 11:28am

Hi Jon,

you forgot to set the parameter values at the terminal stage, i.e.

ocp.set('p', [0, 0, 0.1], ocp_N);

Best,
Jonathan