Find Intersection coordinates of Contour and line plot

Question

Jackson Foley 2020-5-14

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/525425-find-intersection-coordinates-of-contour-and-line-plot

评论： Leilane Passos 2023-2-27

Hello,

I am trying to output the x-values for where the efficiency contour plot intersects the red and blue line. I have used the getContourLineCoordinates function to get the x and y values of the contour plot. I was then trying to find where the the x values of the lines matched those of the contour but ran into some issues. Any help would be much appreciated. Thanks!

clear
clc
clf()
% Motor data from specification
raw_peak=[0 462;2000 462;4000 462;6000 462;8000 462;10000 462;12000 462;14000 399;16000 315];
raw_cont=[0 440;2000 440;4000 440;6000 440;8000 440;10000 440;12000 440;14000 380;16000 300];
N=linspace(0,16000,60); % [rpm]%
Tq=linspace(0,462, 50); % [Nm]%
N_p_rpm_X=raw_peak(:,1); % [rpm]%
Tq_p_Nm_Y=raw_peak(:,2); % [Nm]%
N_c_rpm_X=raw_cont(:,1); % [rpm]%
Tq_c_Nm_Y=raw_cont(:,2); % [Nm]%
kc=0.1; % [W/Nm^2]%
ki=0.0; % [W/(rad/s)]%
kw=1.0e-5; % [W/(rad/s)^3]%
C=500; % [W]%
effMin=0.89; % [-]%
omega=N*pi/30; % [rad/s]
for i=1:length(omega)
    for j=1:length(Tq)
        Pout(i,j)=(omega(i)*Tq(j)); % [W]
        Ploss(i,j)=kc*Tq(j)^2+ki*omega(i)+kw*omega(i)^3+C; % [W]
    end
end
eff=max(effMin,Pout./(Pout+Ploss))*100; % [-]
eff_trans=eff';
V=[70,85,90,91,92,93,94,95,96,97,98,99];
hold on
[C,h]=contour(N,Tq,eff_trans,V);
plot(N_p_rpm_X,Tq_p_Nm_Y,'b','LineWidth', 2);
plot(N_c_rpm_X,Tq_c_Nm_Y,'r','LineWidth', 2);
clabel(C)
contourTable = getContourLineCoordinates(C);
x2=table2array(contourTable(1:end,3));
y2=table2array(contourTable(1:end,4));
N_p_rpm_X_new = [N_p_rpm_X, zeros(size(N_p_rpm_X, 1), size(x2, 2)-size(N_p_rpm_X, 2)); zeros(size(x2, 1)-size(N_p_rpm_X, 1), size(x2, 2))];
Tq_p_Nm_Y_new = [Tq_p_Nm_Y, zeros(size(Tq_p_Nm_Y, 1), size(y2, 2)-size(Tq_p_Nm_Y, 2)); zeros(size(y2, 1)-size(Tq_p_Nm_Y, 1), size(y2, 2))];
Tq_c_Nm_Y_new = [Tq_c_Nm_Y, zeros(size(Tq_c_Nm_Y, 1), size(y2, 2)-size(Tq_c_Nm_Y, 2)); zeros(size(y2, 1)-size(Tq_c_Nm_Y, 1), size(y2, 2))];
x_cord_c = N_p_rpm_X_new(abs(Tq_p_Nm_Y_new - y2)<0.1);
hf=gcf();
ha=gca();
xlim([0 16500]);
ylim([0 500]);
grid on; 
xlabel('Motor Speed [rpm]');
ylabel('Motor Torque [Nm] & Motor efficiency [%]');
title('Motor Efficiency')

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Answer 1

Adam Danz 2020-5-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/525425-find-intersection-coordinates-of-contour-and-line-plot#answer_432462

编辑：Adam Danz 2020-5-14

Jackson Foley, I've just updated the getContourLineCoordinates function, please download the latest version (1.1.0). The (x,y) coordinates in the latest version are in order of proximity which is required to solve this problem easily. You'll also need the intersections() function from the file exchange.

Then, the intersections are as easy as,

[xi,yi] = intersections(contourTable.X, contourTable.Y, N_p_rpm_X, Tq_p_Nm_Y); 
plot(xi, yi, 'ko')

You can repeat that for the red line.

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Jackson Foley 2020-5-14

Amazing, that works! Thank you so much for your help Adam.

Leilane Passos 2023-2-27

Hi, is there a way to pick the indeces as well?

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Answer 2

KSSV 2020-5-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/525425-find-intersection-coordinates-of-contour-and-line-plot#answer_432444

You can use this: https://in.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections?focused=5165138&tab=function

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Jackson Foley 2020-5-14

So I was able to get a matrix of intersection points but its outputting 175 values. From my graph I can visually only see 2 for each efficiency contour curve. Am I missing something?

clear
clc
clf()
% Motor data from specification
raw_peak=[0 462;2000 462;4000 462;6000 462;8000 462;10000 462;12000 462;14000 399;16000 315];
raw_cont=[0 440;2000 440;4000 440;6000 440;8000 440;10000 440;12000 440;14000 380;16000 300];
N=linspace(0,16000,60); % [rpm]%
Tq=linspace(0,462, 50); % [Nm]%
N_p_rpm_X=raw_peak(:,1); % [rpm]%
Tq_p_Nm_Y=raw_peak(:,2); % [Nm]%
N_c_rpm_X=raw_cont(:,1); % [rpm]%
Tq_c_Nm_Y=raw_cont(:,2); % [Nm]%
kc=0.1; % [W/Nm^2]%
ki=0.0; % [W/(rad/s)]%
kw=1.0e-5; % [W/(rad/s)^3]%
C=500; % [W]%
effMin=0.89; % [-]%
omega=N*pi/30; % [rad/s]
for i=1:length(omega)
    for j=1:length(Tq)
        Pout(i,j)=(omega(i)*Tq(j)); % [W]
        Ploss(i,j)=kc*Tq(j)^2+ki*omega(i)+kw*omega(i)^3+C; % [W]
    end
end
eff=max(effMin,Pout./(Pout+Ploss))*100; % [-]
eff_trans=eff';
V=[70,85,90,91,92,93,94,95,96,97,98,99];
hold on
[C,h]=contour(N,Tq,eff_trans,V);
plot(N_p_rpm_X,Tq_p_Nm_Y,'b','LineWidth', 2);
plot(N_c_rpm_X,Tq_c_Nm_Y,'r','LineWidth', 2);
clabel(C)
contourTable = getContourLineCoordinates(C);
x2=table2array(contourTable(1:end,3))';
y2=table2array(contourTable(1:end,4))';
N_p_rpm_X_new = [N_p_rpm_X, zeros(size(N_p_rpm_X, 1), size(x2', 2)-size(N_p_rpm_X, 2)); zeros(size(x2', 1)-size(N_p_rpm_X, 1), size(x2', 2))]';
N_c_rpm_X_new = [N_c_rpm_X, zeros(size(N_c_rpm_X, 1), size(x2', 2)-size(N_c_rpm_X, 2)); zeros(size(x2', 1)-size(N_c_rpm_X, 1), size(x2', 2))]';
Tq_p_Nm_Y_new = [Tq_p_Nm_Y, zeros(size(Tq_p_Nm_Y, 1), size(y2', 2)-size(Tq_p_Nm_Y, 2)); zeros(size(y2', 1)-size(Tq_p_Nm_Y, 1), size(y2', 2))]';
Tq_c_Nm_Y_new = [Tq_c_Nm_Y, zeros(size(Tq_c_Nm_Y, 1), size(y2', 2)-size(Tq_c_Nm_Y, 2)); zeros(size(y2', 1)-size(Tq_c_Nm_Y, 1), size(y2', 2))]';
Peak_cords=[N_p_rpm_X_new;Tq_p_Nm_Y_new];
Cont_cords=[N_c_rpm_X_new;Tq_c_Nm_Y_new];
Contour_cords=[x2;y2];
P=InterX(Cont_cords,Contour_cords);
hf=gcf();
ha=gca();
xlim([0 16500]);
ylim([0 500]);
grid on; 
xlabel('Motor Speed [rpm]');
ylabel('Motor Torque [Nm] & Motor efficiency [%]');
title('Motor Efficiency')