MATLAB: How to convert sine signal into rms signal, using mfile

electrical engineering matlab

I have a sinus fault signal. I need rms signal to relay can work

Best Answer

The RMS function in the Signal Processing Toolbox will give you the RMS value of your entire signal. If you need the RMS within a sliding window, then see this code below and adapt parameters as needed:

% Initialization steps.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Setup: create the signal.
x = linspace(-100, 100, 800); % 800 points from -100 to +100
% Define the period of the sine wave, and it's amplitude
period = 40;
amplitude = 15;
phase = 5;
% Create the signal
y = amplitude * sin(2 * pi * x / period + phase);
subplot(2, 1, 1);
plot(x, y, 'b-', 'LineWidth', 2);
title('Original Signal', 'FontSize', fontSize);
ylabel('y', 'FontSize', fontSize);
xlabel('x', 'FontSize', fontSize);
grid on;
ax = gca;
ax.XAxisLocation = 'origin';
ax.YAxisLocation = 'origin';
xticks(-100:5:100);
% Engine: compute a localized RMS
% Square the signal.
ySquared = y .^ 2;
% Get a moving average within a window
windowWidth = 121;
meanSquareY = movmean(ySquared, windowWidth);
% Take the square root of the mean square signal.
localRMSy = sqrt(meanSquareY);
% Plot those
subplot(2, 1, 2);
plot(x, ySquared, 'b-', 'LineWidth', 2);
hold on;
plot(x, localRMSy, 'r-', 'LineWidth', 2);
caption = sprintf('Local RMS in a moving window of width %d', windowWidth);
title(caption, 'FontSize', fontSize);
ylabel('Signal', 'FontSize', fontSize);
xlabel('x', 'FontSize', fontSize);
grid on;
ax = gca;
ax.XAxisLocation = 'origin';
ax.YAxisLocation = 'origin';
xticks(-100:5:100);
legend('y squared', 'local RMS');
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0, 1, 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')

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Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
%===============================================================================
% Read in a gray scale demo image.
folder = pwd;
baseFileName = 'microgripper_grayscale.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.

subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Crop the image
grayImage = grayImage(1:160,50:250);
% Display the image.
subplot(2, 2, 2);
imshow(grayImage, []);
axis on;
title('Cropped Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 
% Let's compute and display the histogram.
[pixelCount, grayLevels] = imhist(grayImage);
subplot(2, 2, 3); 
bar(grayLevels, pixelCount); % Plot it as a bar chart.
grid on;
title('Histogram of original image', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Gray Level', 'FontSize', fontSize);
ylabel('Pixel Count', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.
% Get the average vertical profile
horizontalProfile = mean(grayImage, 1);
% Plot the profile
subplot(2, 2, 4);
plot(horizontalProfile, 'LineWidth', 2);
grid on;
title('Average Horizontal Profile', 'FontSize', fontSize, 'Interpreter', 'None');
% Get the width of all the bright regions.
% First we need to binarize the profile.
binaryImage = horizontalProfile > 100;
% Label the regions.
labeledRegions = bwlabel(binaryImage);
% Make the area measurements, which is really the length of the region.
measurements = regionprops(labeledRegions, 'Area');
% Get the width of the second region, which is the intergripper gap.
gripperGap = measurements(2).Area;
% Tell user
message = sprintf('The average gap between the gripper fingers is %.3f pixels', gripperGap);
uiwait(helpdlg(message));

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