Theo Jansen Mechanism Matlab Code

As promised, here is some of the Matlab code for the Theo Jansen Mechanism we posted a video of a little while back. We begin every Matlab program with the clear all command. Next are the lengths for all of the linkages.

clear all

%Link Lengths

L1=286;

L2=120;

L3=400;

L4=275;

L5=400;

L6=290;

L7=275;

L8=275;

L9=400;

L10=290;

L11=400;

L12=275;

L13=170;


 
%To get the video output:

a=1;

mov=avifile('TheoJansen.avi','COMPRESSION','None');

for theta=0:pi/20:8*pi


 
%Relating all values to theta2 of 4-bar mechanism O2ABO1

theta2=pi-theta;

ssquared=(L2)^2+(L1)^2-(2*L1*L2*cos(theta2));

s=sqrt(ssquared);

beta=asin((L2*sin(theta2))/s);

psi=acos(((L3^2)+(s^2)-(L4^2))/(2*L3*s));

lambda=acos((L4^2+s^2-L3^2)/(2*L4*s));

theta3=pi-psi+beta;

theta4=pi+beta+lambda;

theta5=lambda+beta;


 
%Finding the points relative to the motion of theta2

O1=[0,0];

O2=[-L1,0];

A=[L2*cos(theta) L2*sin(theta)];

B=[A(1)-L3*cos(psi-beta) A(2)+L3*sin(psi-beta)];


 

%Plotting the 4-bar mechanism

plot ([O1(1),A(1)],[O1(2),A(2)],'r','linewidth',3)

hold on

plot ([O2(1),O1(1)],[O2(2),O1(2)],'black','linewidth',3)

plot ([A(1),B(1)],[A(2),B(2)],'g','linewidth',3)

plot ([O2(1),B(1)],[O2(2),B(2)],'r','linewidth',3)

%Bottom triangle DEF

F=[E(1)-L12*cos(lambda+beta) E(2)-L12*sin(lambda+beta)];


 
plot([D(1),F(1)],[D(2),F(2)],'linewidth',3)

plot([E(1),F(1)],[E(2),F(2)],'linewidth',3)


 

%Link FG

G=[F(1)-L13*cos(lambda+beta) F(2)-L13*sin(lambda+beta)];


 

%Trajectory of point G

plot([F(1),G(1)],[F(2),G(2)],'linewidth',3)

Gx(a)=G(1);

Gy(a)=G(2);

plot(Gx,Gy)


 
axis([-800 400 -800 400])

hold off

a=a+1;

pause(.1)

M=getframe;

mov=addframe(mov,M);

end

mov=close(mov);


 
I left out a portion in the middle so you'll just have to figure that out by yourself!