Code covered by the BSD License  

Highlights from
Hydraulic Valve Parameters From Data Sheets and Experimental Data

image thumbnail

Hydraulic Valve Parameters From Data Sheets and Experimental Data


Steve Miller (view profile)


16 Apr 2010 (Updated )

Models and white paper on obtaining realistic parameter values from data sheets and measured data.

function F  = ...
% Computes objective function for determination of basic parameters of
% the proportional valve actuator that match the requirted frequency
% response. The required and actual frequency responses are compared by
% the frequency at which phase shift in -90 deg takes place. The frequency 
% response of a nonlinear system is obtained by processing the pulse 
% transient characteristic with the FFT algorythm. 
% Copyright 2010 MathWorks, Inc.

% frequency_20   - frequency (Hz) at phase shift in -pi/2 at 20% input signal
% frequency_100  - frequency (Hz) at phase shift in -pi/2 at 100% input signal

model = 'actuator_freq_testrig_pulse_FFT_method';

assignin('base','act_gain', x(1));
assignin('base','time_const', x(2));
assignin('base','act_saturation', x(3));


y_20 = yout(:,2);               % Pulse transient characteristic at 20% input
y_100 = yout(:,1);              % Pulse transient characteristic at 100% input
fs = 1000;                      % Sampling frequency
n = length(y_20);               % Window length = Transform length
y_20_fft = fft(y_20,n);         % Discrete Fourier Transform
y_100_fft = fft(y_100,n);       % Discrete Fourier Transform
f0 = (0:n/2-1)*(fs/n);          % Shifted frequency range, positive range
y_20_0 = fftshift(y_20_fft);    % Shifted DFT at 20% input
y_100_0 = fftshift(y_100_fft);  % Shifted DFT at 100% input
% Phase characteristic at 20% input for positive frequencies after unwrap
phase_20 = unwrap(angle(y_20_0(257:end))); 
% Phase characteristic at 100% input for positive frequencies after unwrap
phase_100 = unwrap(angle(y_100_0(257:end)));

% Computing frequency at 90 deg phase shift by interpolation of phase
% characteristics
frq_20 = interp1(phase_20,f0,-pi/2);
frq_100 = interp1(phase_100,f0,-pi/2);

% Objective function as a sum of squared differences between the specified
% and computed frequencies at phase shift angle in -pi/2
F = (frequency_20 - frq_20)^2 + (frequency_100 - frq_100)^2; 



Contact us