Index in position 1 is invalid. Array indices must be positive integers or logical values.

Hi everyone, I am getting the following error,

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in reversepuma (line 44)

c71 = dot(S7_f, S1_f)

lin44: c71 = dot(S7_f, S1_f)

I created a function to give 6 outputs based on 4 inputs ,( Reverse kinematic analysis)

To test the function i gave some sample values and i got that error,

Any help would be greatly appreciated ,

TIA

%close-the-loop analysis of Puma Robot
%Following paramters are given
%function [a71, S7, S1, al71, th7, gam1] = close_loop_puma ( P_tool_6, P_tool_f, S6_f , a67_f)
P_tool_6 = [5; 3; 7];
P_tool_f = [ 25; 23; 24];
S6_f = [ 0.177; 0.884; -0.433];
a67_f = [-0.153; 0.459; 0.875];
S1_f = [ 0; 0; 1];

P_x = P_tool_6(1)
P_y = P_tool_6(2)
P_z = P_tool_6(3)
a56 = 0

%Twist angle
al12 = 90
al23 = 0
al34 = 270
al45 = 90
al56 = 90

%Joint Offset
S2 = 5.9
S3 = 0
S4 = 17
S5 = 0

R6_f = [ a67_f cross(S6_f, a67_f) S6_f]
P_6orig_f = P_tool_f -(P_x * a67_f)-cross(P_y*S6_f, a67_f)-P_z*S6_f

T6_f = [ R6_f P_6orig_f ; 0 0 0 1]

%Hypotehtical closure link

S7_f = cross(a67_f, S6_f)
%Determination of close loop parameters
a71_cross = cross(S7_f , S1_f)%crossproduct
premag = a71_cross.*a71_cross   %Finding the magnitude of the vector
mag = sqrt( premag(1)+premag(2)+premag(3))%Finding the magnitude of vector

a71_f = a71_cross / mag %unit vector

%twist angle
c71 = dot(S7_f, S1_f)
s71 = dot(cross(S7_f,S1_f),a71_f)
al71= atan2(s71,c)

%Joint angle
c7  = dot(a67_f,a71_f)
s7  = dot(cross(a67_f,a71_f),S7_f)
th7 = atan2(s7,c7)

%The angle gam1 is t n e angle between the vector a7i and the X axis of the fixed coordinate system 
cos(gam1) = dot( a71_f, [1;0;0])
sin(gam1) = dot(cross(a71_f, [1; 0; 0]), S1_f)
gam1      = atan2( sin(gam1), cos(gam1))

S7  = (dot(cross(S1_f,P_6orig_f),a71_f))/s71
a71 = (dot(cross(P_6orig_f,S1_f),S7_f))/s71
S1  = (dot(cross(P_6orig_f,S1_f),a71_f))/s71

%end 

Answer 1

[the cyclist]

Just a guess, but I think you probably named a variable dot, which is being used instead of the function you want.

What does

which dot

give as output?

[Defrauxche]

Yeah, even after changing the variable name , it was left in the workspace so that caused the error. Thank you