I need someone to look at this code for a robotics simulation

When I run my code I get this error:

Undefined function or variable 'Link'.

Error in RCDC (line 26) L(1)=Link([0,0,0.5,0,0]);

Heres my code:

clear all
syms q1 q2 q4 a1 a2 d3 d4 t
% q1, q2, d3, q4 variable angle
% a1, a2, d4 length robot
assume(a1, 'real');assume(a1>0);
assume(a2, 'real');assume(a2>0);
assume(d3, 'real');assume(d3>0);
assume(d4, 'real');assume(d4>0);
assume(q1, 'real');
assume(q2, 'real');
assume(q4, 'real');
% Input Matrix 
A_01 = [cos(q1) -sin(q1) 0 a1*cos(q1); sin(q1)  cos(q1) 0 a1*sin(q1); 0 0  1 0;0 0 0 1]
A_12 = [cos(q2)  sin(q2) 0 a2*cos(q2); sin(q2) -cos(q2) 0 a2*sin(q2); 0 0 -1 0;0 0 0 1]
A_23 = [1 0 0 0; 0 1 0 0; 0 0 1 d3; 0 0 0 1]
A_34 = [cos(q4) -sin(q4) 0  0; sin(q4) cos(q4) 0 0; 0 0 1 d4; 0 0 0 1]
% Matrix Last
A_04=A_01*A_12*A_23*A_34;
A_02=simplify(A_01*A_12);
A_03=simplify(A_02*A_23);
disp('Matrix Last:')
A_04=simplify(A_04)
rE=A_04(1:3,4) % Final Point

% Robotics System Toolbox
L(1)=Link([0,0,0.5,0,0]);
L(2)=Link([0,0,0.4,pi,0]);
L(3)=Link([0,0,0,0,1]);
L(4)=Link([0,0.1,0,0,0]);
rob=SerialLink(L);

t=[0:0.005:4];
j=length(t);
for i=1:j
    %%%%%%%%%%%%%%%%
    xE(i)=0.3+0.2*(1+sin(5*t(i))*cos(t(i)));
    yE(i)=0.3+0.2*(1+sin(5*t(i))*sin(t(i)));
    zE(i)=-0.3;
    %%%%%%%%%%%%%%%%
    A=2*0.5*xE(i);
    B=2*0.5*yE(i);
    D=-0.4^2+xE(i).^2+yE(i).^2+0.5^2;
    s1=(D.*B-A.*sqrt(A.^2+B.^2-D.^2))./(A.^2+B.^2);
    c1=(D.*A+B.*sqrt(A.^2+B.^2-D.^2))./(A.^2+B.^2);
    q1_num(:,i)=atan2(s1,c1);
    s2=(yE(i)-0.5.*sin(q1_num(:,i)));
    c2=(xE(i)-0.5.*cos(q1_num(:,i)));
    q2_num(:,i)=atan2(s2,c2)-q1_num(:,i);
    d3_num(:,i)=-zE(i)-0.1;
    q4_num(:,i)=q1_num(:,i)+q2_num(:,i);
end
figure
clf
hold on
grid on
axis([-1,1,-1,1,-1,1])
for i=1:length(t)
    plot(rob,[q1_num(1,i),q2_num(1,i),d3_num(1,i),q4_num(1,i)])
    plot3(xE(i),yE(i),zE(i),'b.')
    pause(1/1000)
end

Answer 1

[Walter Roberson]

Despite the comment, Link is not part of the Robotics System Toolbox. It is part of the third party Robotics Toolbox by Peter Corke.

https://www.mathworks.com/matlabcentral/linkexchange/links/2961-robotics-toolbox-for-matlab

[Nick Haufler]

Oh ok thank you. I must have got the wrong one. Is there any way I could replace Link with something in the Robotics System Toolbox.

[Walter Roberson]

Sorry I do not know enough about either package to suggest a corresponding function.