How to respresent and plot data while on loop in Matlab?

Alexandru Lapusneanu

2018 8 13

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What I'm trying to to is to simulate the position of two satellites and to determine if they will collide. For that I'm using a Rk4 method. As you can see, in the loop I have the drawnow command that adds a point on a 3d graph, after avery iteration. What I'm interested in is to find a way to represent the 3d plot until the condition of collision meets (where I have the message) and also to get the values on the .txt file, while in the loop not outside. When I use the return command, and try to plot or to add text, I have an error "vectors must be the same length" and doesn't let me obtain the data. That happens because lets say sat1=1X200 while tspan=1X201. Is there any other command that I could use instead of return or a better solution?

Here is my code:

    figure(1);
  orbitsat1=animatedline('Color','r');
orbitsat2=animatedline('Color','g');
msat1=124;
msat2=234;
Asat1=2.2;
Asat2=3.2;
sat10(1,1)=   453322.3616  ;
sat10(2,1)=   -2346021.219 ;
sat10(3,1)=     -7894131.349 ;
sat10(4,1)=     2142.38067;
sat10(5,1)=   7487.44895   ;
sat10(6,1)=     -9864.00872;
sat20(1,1)=   543322.3616  ;
sat20(2,1)=   -3246021.219 ;
sat20(3,1)=     -8794131.349 ;
sat20(4,1)=     1242.38067;
sat20(5,1)=   4787.44895   ;
sat20(6,1)=     -8964.00872;
tspan = 0:200;
secpday = 60*60*24;
a1 = 2018;
la1 = 1;
z1 = 2;
o1 = 12;
m1 = 0;
s1 = 0;
n1 = datenum(a1,la1,z1,o1,m1,s1);
n1 = n1 + tspan/secpday;
[an,luna,zi,ora,min,sec] = datevec(n1);
h=1;
sat1 = zeros(6, tspan(end)/h);
sat1(:,1) = sat10;
sat2 = zeros(6, tspan(end)/h);
sat2(:,1) = sat20;
for i=1:(tspan(end)/h)
    k_1 = simsat1(tspan(i), sat1(:,i), msat1, Asat1, sat1(4:6, i));
    k_2 = simsat1(tspan(i)+0.5*h, sat1(:,i)+0.5*h*k_1,msat1, Asat1, sat1(4:6, i));
    k_3 = simsat1((tspan(i)+0.5*h), (sat1(:,i)+0.5*h*k_2),  msat1, Asat1, sat1(4:6, i));        k_4 = simsat1((tspan(i)+h),(sat1(:,i)+k_3*h), msat1, Asat1, sat1(4:6, i));
      k_12 = simsat2(tspan(i), sat2(:,i),  msat2, Asat2, sat2(4:6, i));
      k_22 = simsat2(tspan(i)+0.5*h, sat2(:,i)+0.5*h*k_12,  msat2, Asat2, sat2(4:6, i));
      k_32 = simsat2((tspan(i)+0.5*h), (sat2(:,i)+0.5*h*k_22), msat2, Asat2, sat2(4:6, i));
      k_42 = simsat2((tspan(i)+h),(sat2(:,i)+k_32*h),  msat2, Asat2, sat2(4:6, i));
      sat2(:,i+1) = double(sat2(:,i) + (1/6)*(k_12+2*k_22+2*k_32+k_42)*h);
      sat1(:,i+1) = double(sat1(:,i) + (1/6)*(k_1+2*k_2+2*k_3+k_4)*h);
      addpoints(orbitsat1,sat1(1,i),sat1(2,i),sat1(3,i));
      drawnow update
      hold off
      Rorb = ((sat1(1,i).^2 + sat1(2,i).^2 + sat1(3,i).^2).^0.5);
      Rcsc = ((sat2(1,i).^2 + sat2(2,i).^2 + sat2(3,i).^2).^0.5);
      dif=Rorb-Rcsc;
      if (dif >0.5*10^10 && dif < 2*10^5) && i>350
          Message = sprintf('Data:\nan:%d\nluna:%d\nzi:%d\nora:%d\nminut:%d\nsecunda:%d',an(i),luna(i),zi(i),ora(i),min(i),sec(i));
          msgbox(Message)
          msgbox('Coliziune!','Coliziune','warn',Message);
          return
      end
  end
Pozx=sat1(1,:);
Pozy=sat1(2,:);
Pozz=sat1(3,:);
Tbody=[an; luna; zi ;ora; min; sec; Pozx; Pozy; Pozz];
twobody = fopen('nobody.txt','w');
fprintf(twobody,'Rezultate Twobody (metri) \n\n');
fprintf(twobody,'  An  luna  zi   ora min sec            pozitia pe  x     pozitia pe  y      pozitia pe  z       viteza pe  x    viteza pe  y    viteza pe  z\n\n');
fprintf(twobody,'---------------------------------------------------------------------------------------------------------------------------------------------\n%6d-%3d-%3d\t%3d:%3d:%3d\t\t\t\t%12.6f\t%12.6f\t\t%12.6f\t\t%12.6f\t%\n',Tbody);
fclose(twobody);
where simsat1
function sat1prim=simsat1(t,sat1,msat1,Asat1,vit)
miu=398600.4418*10^9;
magn=(sat1(1)^2+sat1(2)^2+sat1(3)^2)^(3/2);
sat1prim=zeros(6,1);
sat1prim(1,1)=sat1(4);
sat1prim(2,1)=sat1(5);
sat1prim(3,1)=sat1(6);
sat1prim(4,1)=double(-miu*sat1(1)/magn);
sat1prim(5,1)=double(-miu*sat1(2)/magn);
sat1prim(6,1)=double(-miu*sat1(3)/magn);
end
and simsat2
function sat2prim=simsat2(t,sat2,msat2,Asat2,vit)
miu=398600.4418*10^9;
magn=(sat2(1)^2+sat2(2)^2+sat2(3)^2)^(3/2);
sat2prim=zeros(6,1);
sat2prim(1,1)=sat2(4);
sat2prim(2,1)=sat2(5);
sat2prim(3,1)=sat2(6);
sat2prim(4,1)=double(-miu*sat2(1)/magn);
sat2prim(5,1)=double(-miu*sat2(2)/magn);
sat2prim(6,1)=double(-miu*sat2(3)/magn);
end

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James Tursa 2018-8-13

So, is this all supposed to be inside a function, and you want to return the satellite positions up to the point of the collision to the caller? But you are having some type of problem doing that?

Alexandru Lapusneanu 2018-8-13

Indeed , thats the problem. When there is a collision I would want to stop the loop, to display the "collision message" and all the positions over iterated time should be saved in the .txt file.

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