% Generate transfer functions for loop shaping performance requirements
% from parameters specified in uav_params.m
%
% Copyright (C) 2024, Naoki Sean Pross, ETH Zürich
% This work is distributed under a permissive license, see LICENSE.txt
%
% Arguments:
%   PARAMS  Struct of design parameters and constants generated by uav_params
%   PLOT    When set to 'true' it plots the inverse magnitude of the
%           performance transfer function
%
% Return value:
%   PERF    Struct performance transfer functions


function [perf] = uav_performance_musyn(params, do_plots)

% Laplace variable
s = tf('s');

% Bandwitdhs
bw_alpha = .7 * params.actuators.ServoNominalAngularVelocity;
bw_omega = 8;

bw_xy = .1;
bw_z = .4;

bw_xydot = .5;
bw_zdot = .1;

bw_phitheta = bw_xy;
bw_psi = .08;

% Inverse performance functions
W_Palpha = .25 / (s / bw_alpha + 1); 
W_Pomega = .1 / (s / bw_omega + 1);

W_Pxy = 2 * bw_xy^2 / (s^2 + 2 * .9 * bw_xy * s + bw_xy^2);
W_Pz = bw_z^2 / (s^2  + 2 * 1 * bw_z * s + bw_z^2);

W_Pxydot = tf(.1); % .2 / (s / bw_xydot + 1);
W_Pzdot = tf(.1); % .5 / (s / bw_zdot + 1);
 
W_Pphitheta = .01 / (s / bw_phitheta + 1);
W_Ppsi = tf(.1); % .1 / (s / bw_psi + 1);

% Construct performance vector by combining xy and z
W_PP = blkdiag(W_Pxy * eye(2), W_Pz);
W_PPdot = blkdiag(W_Pxydot * eye(2), W_Pzdot);
W_PTheta = blkdiag(W_Pphitheta * eye(2), W_Ppsi);

perf = struct(...
  'FlapAngle', W_Palpha * eye(4), ...
  'Thrust', W_Pomega, ...
  'Position', W_PP, ...
  'Velocity', W_PPdot, ...
  'Angles', W_PTheta);

if do_plots
  % Bode plots of performance requirements
  figure; hold on;

  bodemag(1/W_Palpha);
  bodemag(1/W_Pomega);
  bodemag(1/W_Pxy);
  bodemag(1/W_Pz);
  bodemag(1/W_Pxydot);
  bodemag(1/W_Pzdot);
  bodemag(1/W_Pphitheta);
  bodemag(1/W_Ppsi);

  grid on;
  legend('$W_{P,\alpha}$', '$W_{P,\omega}$', ...
    '$W_{P,xy}$', '$W_{P,z}$', ...
    '$W_{P,\dot{x}\dot{y}}$', '$W_{P,\dot{z}}$', ...
    '$W_{P,\phi\theta}$', '$W_{P,\psi}$', ...
    'interpreter', 'latex', 'fontSize', 8);
  title('\bfseries Inverse Performance Requirements', ...
    'interpreter', 'latex');

  % Step response of position requirements
  figure; hold on;

  step(W_Palpha);
  step(W_Pomega);
  step(W_Pxy);
  step(W_Pz);
  step(W_Pxydot);
  step(W_Pzdot);
  step(W_Pphitheta);
  step(W_Ppsi);

  grid on;
  legend('$W_{P,\alpha}$', '$W_{P,\omega}$', ...
    '$W_{P,xy}$', '$W_{P,z}$', ...
    '$W_{P,\dot{x}\dot{y}}$', '$W_{P,\dot{z}}$', ...
    '$W_{P,\phi\theta}$', '$W_{P,\psi}$', ...
    'interpreter', 'latex', 'fontSize', 8);
  title('Step responses of performance requirements');
end

end
% vim: ts=2 sw=2 et: