test-bench-apa/index.org

Test Bench APA

• Parameters
• Filter White Noise
• Load Data
• Time Domain Data
• Compute TF estimate and Coherence
• Coherence
• Transfer Function

Parameters

  Ts = 1e-4;

Filter White Noise

  Glpf = 1/(1 + s/2/pi/500);

  Gz = c2d(Glpf, Ts, 'tustin');

Load Data

  data = SimulinkRealTime.utils.getFileScopeData('data/apa95ml_5kg.dat').data;

Time Domain Data

  figure;

  subplot(1,2,1);
  plot(data(:, 3), data(:, 1))
  ylabel('Input Voltage [V]'); xlabel('Time [s]');


  subplot(1,2,2);
  plot(data(:, 3), data(:, 2))
  ylabel('Output Displacement [m]'); xlabel('Time [s]');

Compute TF estimate and Coherence

  win = hann(ceil(1/Ts));

  [tf_est, f] = tfestimate(data(:, 1), -data(:, 2), win, [], [], 1/Ts);
  [co_est, ~] = mscohere(  data(:, 1), -data(:, 2), win, [], [], 1/Ts);

Coherence

  figure;

  hold on;
  plot(f, co_est, 'k-')
  set(gca, 'Xscale', 'log'); set(gca, 'Yscale', 'lin');
  ylabel('Coherence'); xlabel('Frequency [Hz]');
  hold off;

Transfer Function

  figure;
  ax1 = subplot(2, 1, 1);
  hold on;
  plot(f, abs(tf_est), 'k-')
  set(gca, 'Xscale', 'log'); set(gca, 'Yscale', 'log');
  ylabel('Amplitude'); xlabel('Frequency [Hz]');
  hold off;

  ax2 = subplot(2, 1, 2);
  hold on;
  plot(f, 180/pi*angle(tf_est), 'k-')
  set(gca, 'Xscale', 'log'); set(gca, 'Yscale', 'lin');
  ylabel('Phase'); xlabel('Frequency [Hz]');
  legend();
  hold off;

  linkaxes([ax1,ax2], 'x');
  xlim([10, 5000]);