I keep getting this error: Error using vertcat Dimensions of arrays being concatenated are not consistent. Error in ME450_project_linkage (line 16) P5_pos = D*[0;-1+sin(theta)];

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Matthew Palermo 2019-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/494736-i-keep-getting-this-error-error-using-vertcat-dimensions-of-arrays-being-concatenated-are-not-consi

回答： Walter Roberson 2019-12-4

I am trying to model a knuckle linkage system and I keep getting the error that the array dimensions are not consistent fro some reason. Additionally, matlab wont let me model the motion of a certain point (P5_pos). When I try to it gives me the error. Here is the code. It's not finished.

clear 
clc
A = 8.25; %in
B = 48;
C = 42;
D = 20;
t = 0:0.01:20; %sec
omega = 5.0265; %rad/sec
theta = omega*t;
P1_pos = [56.25;43.1];
P2_pos = [56.25-A*cos(theta);43.1-A*sin(theta)];
P4_pos = C*[0;1];
P5_pos = D*[0;-1+sin(theta)];
E = sqrt(A^2 + D^2 - 2*A*D*cos(theta));
a = asin(A*sin(theta)./E);
b = acos(E.^2 + C^2 - B^2)./(2*E*C);
P3_pos = [C + B*cos(a+b); B*sin(a+b)];
P5x = P5_pos(1,:);
P5y = P5_pos(:,1);
P5vx = diff(P5x);
P5vy = diff(P5y);
P5v = sqrt(P5vx^2 + P5vy^2);
for i = length(t)
    ani = subplot(2,1,1);
    P1_pos_cir = viscircles(P1_pos',0.05);
    P2_pos_cir = viscircles(P2_pos(:,i)',0.05);
    P4_pos_cir = viscircles(P4_pos',0.05);
    P5_pos_cir = viscircles(P5_pos',0.05);
    P3_pos_cir = viscircles(P3_pos(:,i)',0.05);
    
    barA = line([P1_pos(1) P2_pos(1,i)],[P1_pos(2) P2_pos(2,i)]);
    barB = line([P2_pos(1,i) P3_pos(1,i)],[P2_pos(2,i) P3_pos(2,i)]);
    barC = line([P3_pos(1,i) P4_pos(1)],[P3_pos(2,i) P4_pos(2)]);
    barD = line([P3_pos(1,i) P5_pos(1)],[P3_pos(2,i) P5_pos(2)]);
    
    axis(ani,'equal');
    set(gca,'XLim',[-10 60],'YLim',[-30 60]);
    pause(0.005);
    
end

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Stephen23 2019-12-4

theta has size 1x2001.

Zero has size 1x1.

On this line you try to vertically concatenate them together:

P5_pos = D*[0;-1+sin(theta)];

Arrays can only be vertically concatenated if they have the same number of columns: do 1x2001 and 1x1 have the same number of columns (hint: no).

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Answer 1

Walter Roberson 2019-12-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/494736-i-keep-getting-this-error-error-using-vertcat-dimensions-of-arrays-being-concatenated-are-not-consi#answer_404647

P5_pos = D*[0;-1+sin(theta)];

Your theta is 1 x 2001, so -1+sin(theta) is 1 x 2001. You are trying to create an array with two rows, one of which is a scalar 0, and the other of which is 1 x 2001 . 1 x 1 (the zero) does not have the same number of columns as 1 x 2001, so the attempt fails.