Matlab tools: Motor transfer function curves

Tools/Matlab/motors.m

+clear all;
+close all;
+
+% Measurement data
+% 1045 propeller
+% Robbe Roxxy Motor (1100 kV, data collected in 2010)
+data = [ 45, 7.4;...
+         38, 5.6;...
+         33, 4.3;...
+         26, 3.0;...
+         18, 2.0;...
+         10, 1.0 ];
+
+% Normalize the data, as we're operating later
+% anyways in normalized units
+data(:,1) = data(:,1) ./ max(data(:,1));
+data(:,2) = data(:,2) ./ max(data(:,2));
+
+% Fit a 2nd degree polygon to the data and
+% print the x2, x1, x0 coefficients
+p = polyfit(data(:,2), data(:,1),2)
+
+% Override the first coffefficient for testing
+% purposes
+pf = 0.62;
+
+% Generate plotting data
+px1 = linspace(0, max(data(:,2)));
+py1 = polyval(p, px1);
+
+pyt = zeros(size(data, 1), 1);
+corr = zeros(size(data, 1), 1);
+
+% Actual code test
+% the two lines below are the ones needed to be ported to C:
+%   pf: Power factor parameter.
+%   px1(i): The current normalized motor command (-1..1)
+%   corr(i): The required correction. The motor speed is:
+%            px1(i) 
+for i=1:size(px1, 2)
+    
+    % The actual output throttle
+    pyt(i) = -pf * (px1(i) * px1(i)) + (1 + pf) * px1(i);
+    
+    % Solve for input throttle
+    % y = -p * x^2 + (1+p) * x;
+    % 
+end
+
+plot(data(:,2), data(:,1), '*r');
+hold on;
+plot(px1, py1, '*b');
+hold on;
+plot([0 px1(end)], [0 py1(end)], '-k');
+hold on;
+plot(px1, pyt, '-b');
+hold on;
+plot(px1, corr, '-m');