# Can you help and show if any where ive gone wrong with any codes

6 次查看（过去 30 天）
Daniel Martelli2021-9-13

This code is only for Position Analysis
clc; close all; clear; format compact;
% length of links
r1 = 100;
r2 = 50;
r3 = 780;
r4 = 80;
l4 = 125;
eta = deg2rad(30);
% Angle theta 2
th2 = pi/3:2*pi/36:2*pi+pi/3;
n = length(th2)
% Calculations
L = sqrt(r1^2+r2^2-2*r1*r2.*cos(th2));
Sphi = (r2./L).*sin(th2);
Cphi = (r2^2-r1^2-L.^2)./(-2*r1.*L);
phi = atan2(Sphi, Cphi);
th3 = acos((r4^2-r3^2-L.^2)./(-2*r3.*L))-phi;
Cgamma = (r3^2-r4^2-L.^2)./(-2*r4.*L);
Sgamma = (r3/r4).*sin(th3+phi);
gamma = atan2(Sgamma, Cgamma);
th4 = pi-phi-gamma;
% Use this to find the 3rd join on link 4
all = th4-eta;
% Position of joints
xO2 = 0;
yO2 = 0;
xA = r2*cos(th2);
yA = r2*sin(th2);
xB = xA+r3*cos(th3);
yB = yA+r3*sin(th3);
xO4 = r1;
yO4 = 0;
xC5 = xO4+l4*cos(all);
yC5 = yO4+l4*sin(all);
% These are used to plot the length of each link in the Draw-Linkage
Xcrank = [xO2, xA(1)];
Ycrank = [yO2, yA(1)];
Xcoupler = [xA(1), xB(1)];
Ycoupler = [yA(1), yB(1)];
Xrocker = [xB(1), xO4];
Yrocker = [yB(1), yO4];
Xground = [-1.2*r2, r1+10];
Yground = [yO2, yO4];
XC4C5 = [xO4, xC5(1)];
YC4C5 = [yO4, yC5(1)];
XBC5 = [xB(1), xC5(1)];
YBC5 = [yB(1), yC5(1)];
Draw_linkage = plot(xA, yA, '--r',...
Xcrank, Ycrank, 'r', Xcoupler, Ycoupler, 'b',...
Xrocker, Yrocker, 'g', XC4C5, YC4C5, 'g',...
XBC5, YBC5, 'g', Xground, Yground, '--k', 'linewidth', 1.2);
axis([-r2-r3 2*r2+r3 -2*r2 r4]);
axis equal
for i=1:n
delete(Draw_linkage);
Xcrank = [xO2, xA(i)];
Ycrank = [yO2, yA(i)];
Xcoupler = [xA(i), xB(i)];
Ycoupler = [yA(i), yB(i)];
Xrocker = [xB(i), xO4];
Yrocker = [yB(i), yO4];
Xground = [-1.2*r2, r1+10];
Yground = [yO2, yO4];
XC4C5 = [xO4, xC5(i)];
YC4C5 = [yO4, yC5(i)];
XBC5 = [xB(i), xC5(i)];
YBC4 = [yB(i), yC5(i)];
Draw_linkage = plot(xA, yA, '--r',...
Xcrank, Ycrank, 'r', Xcoupler, Ycoupler, 'b',...
Xrocker, Yrocker, 'g', XC4C5, YC4C5, 'g',...
XBC5, YBC5, 'g', Xground, Yground, '--k', 'linewidth', 1.2);
axis([-r2-r3 2*r2+r3 -2*r2 r4]);
axis equal
F(i) = getframe;
pause(1/20);
end
movie(F, 2);

### 回答（1 个）

Tanmay Das 2021-9-19
Hi,
atan2(Y,X) returns the four-quadrant inverse tangent (tan-1) of Y and X, which must be real. In the given code, Sgamma is a vector of complex quantities. So it generates an error that "Inputs must be real".
##### 2 个评论显示隐藏 1更早的评论
Tanmay Das 2021-12-30，12:30
In your code, you have written these lines:
Sgamma = (r3/r4).*sin(th3+phi);
gamma = atan2(Sgamma, Cgamma);
where Sgamma comes out to be a complex quantity. (You may try printing the value of Sgamma in command window)
However, 'atan2' function only takes real input arguments. So, it gnerated the error that "Inputs must be real"

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