Error using atan2 Inputs must be real.

Error using atan2

Inputs must be real.

how can i fix this?

clc;
clear all;
a1 = 150; alpha1 = pi/2; d1 = 470;
a2 = 600; alpha2 = 0; d2 = 0;
a3 = 120; alpha3 = pi/2; d3 = 720; 
syms c1 c2 c23 c3 c4 c5 c6 s1 c1 s2 s23 s3 s4 s5 s6 R03 R36 th1 th2 th3 th4 th5 th6 Xc Yc Zc R06 ox oz oy d6 r d D r11 r12 r13 r21 r22 r23 r31 r32 r33
c1 = cos(th1)
c2 = cos(th2)
c3 = cos(th3)
s1 = sin(th1)
s2 = sin(th2)
s3 = sin(th3)
c23 = cos(th2+th3)
s23 = sin(th2+th3)

d = a1
d6 = 50

%assume d6 = 5
R = [1 0 0 500;
    0 1 0 100;
    0 0 1 1500;
    0 0 0 1];
r11 = R(1,1)
r12 = R(1,2)
r13 = R(1,3)
r21 = R(2,1)
r22 = R(2,2)
r23 = R(2,3)
r31 = R(3,1)
r32 = R(3,2)
r33 = R(3,3)

ox = R(1,4)
oy = R(2,4)
oz = R(3,4)
Xc = ox - d6*R(1,3)
Yc = oy - d6*R(2,3)
Zc = oz - d6*R(3,3)
D = (Xc^2+Yc^2-d^2+(Zc-d1)^2-a2^2-a3^2)/(2*a2*a3)
%inverse kinematic 

th1 = atan2(Xc,Yc)
th2 = atan2(sqrt(Xc^2+Yc^2-d^2),Zc-d1)-atan2(a2+a3*c3,a3*s3)
th3 = atan2 (D,sqrt((1-d^2)))
th4 = atan2(c1*c23*r13+s1*c23*r23+s23r33,-c1*s23*r13-s1*s23*r23+c23*r33)
th5 = atan2(s1*r13-c1*r23,sqrt(1-(s1*r13-c1*r23)^2))
th6 = atan2(-s1*r11+c1*r21, s1*r12-c1*r22)

[Walter Roberson]

d is 150 so sqrt(1-d^2) is not going to be real.

That appears to be the only place you are using complex numbers, so I recommend you recheck your formula.

[Tony Yu]

oh I was a typo, it should be "D", I updated some parameters but now my th4 is not give me a solution

clc;
clear all;
a1 = 150; alpha1 = pi/2; d1 = 470;
a2 = 600; alpha2 = 0; d2 = 0;
a3 = 120; alpha3 = pi/2; d3 = 720; 
syms c1 c2  c3 c4 c5 c6 s1 c1 s2  s3 s4 s5 s6 R03 R36 th1 th2 th3 th4 th5 th6 Xc Yc Zc R06 ox oz oy d6 r d D r11 r12 r13 r21 r22 r23 r31 r32 r33
c1 = cos(th1)
c2 = cos(th2)
c3 = cos(th3)
s1 = sin(th1)
s2 = sin(th2)
s3 = sin(th3)
c23 = cos(th2+th3)
s23 = sin(th2+th3)

d = a1
d6 = 500

%assume d6 = 500
R = [1 0 0 500;
    0 1 0 100;
    0 0 1 1500;
    0 0 0 1];
r11 = R(1,1)
r12 = R(1,2)
r13 = R(1,3)
r21 = R(2,1)
r22 = R(2,2)
r23 = R(2,3)
r31 = R(3,1)
r32 = R(3,2)
r33 = R(3,3)

ox = R(1,4)
oy = R(2,4)
oz = R(3,4)
Xc = ox - d6*R(1,3)
Yc = oy - d6*R(2,3)
Zc = oz - d6*R(3,3)
D = (Xc^2+Yc^2-d^2+(Zc-d1)^2-a2^2-a3^2)/(2*a2*a3)
%inverse kinematic 

th1 = atan2(Xc,Yc)
th3 = atan2(D,sqrt(1-D^2))
c3 = cos(th3)
s3 = sin(th3)
th2 = atan2(sqrt(Xc^2+Yc^2-d^2),Zc-d1)-atan2(a2+a3*c3,a3*s3)
c23 = cos(th2+th3)
s23 = sin(th2+th3)
th4 = atan2(c1*c23*r13+s1*c23*r23+s23*r33,-c1*s23*r13-s1*s23*r23+c23*r33)
th5 = atan2(s1*r13-c1*r23,sqrt(1-(s1*r13-c1*r23)^2))
c1 = cos(th1)
s1 = sin(th1)
th6 = atan2(-s1*r11+c1*r21, s1*r12-c1*r22)

Answer 1

[Ameer Hamza]

It gives the value of th4, but the output is in the symbolic format. Convert it into a floating-point value by using double(). Change the line like this

th4 = double(atan2(c1*c23*r13+s1*c23*r23+s23*r33,-c1*s23*r13-s1*s23*r23+c23*r33))

[Tony Yu]

Thanks, it works!

Answer 2

[Javed Ahmed]

now way . it doesnt work.

[Walter Roberson]

What code are you using that it is not working for?