Need help for discrete time motion in matlab

Constantine

hello for all, I am trying to write some code by myself and I found out it is hard!! I am trying to create the motion using matlab and to control the motion within certain boundary. In my case, the starting point is (0,1250), and it should have some forward speed and heading angle for the point to move. After some time intervals, the point must have moving out of the boundary (y=1000 or y=1500), and in that case, I have to decide an angle to drag the point back to the boundaries specified (between y=1000 and y=1500). The simulation should stop when the point is moving beyond x=1590. I know there must be hundreds of errors that I may have done when writing the codes. I also well aware that my knowledge in matlab is terribly limited.Thus, I hereby asking help for those who can understand my situation and willing to help me, thanks a lot.....:)

The code that I have written is as below (please don't laugh if u think that I have written something ridiculous.....haha)

clc
clear
xmin=[0; 0];         % Set edges of region want to search in
xmax=[3000;3000];
c=3.0E8; % m/s light travel speed
f=300E6; % MHz signal frequency GSM900MHz
w=2*pi*f;
lambda=2*pi*c/w;
V=40;
delta=5;
figure(1)
clf
% Plot initial and final positions
plot(0,1250,'s')
axis([0 3000 0 3000])
hold on
xlabel('x');
ylabel('y');
title('initial vehicle (square) position');
%starting point of ship
x0=0;
y0=1250;
position=[x0,y0];
for t=1:1:100; %assume for 100 timesteps
   h(t)=10;
   x(t)=x0;
   x(t+1)= x(t)+ delta*V*sin(h(t));
   y(t)=y0;
   y(t+1)= y(t)+ delta*V*cos(h(t));
   %To move within the boundary of y=1500 and y=1000
   if y(t) < y==1500;
       h(t)=10;
   elseif y(t) > y==1000;
       h(t)=10;
   else
       new = [x(t+1), y(t+1)];
       old = [x(t), y(t)];
       dest = [ (x(t+1)+delta*V), 1250]; 
       a= new-old;
       b= dest-new;
       theta= sign(b(1)*a(2)-b(2)*a(1))*acos (dot(a,b)/(norm(a)*norm(b)));
       h(t)= theta;
   end
   %To halt the system when the point exceed x=1590
   if x(t)> x==1590;
       sprintf('the signal is too weak')
      x(t+1)=x(t);
      y(t+1)=y(t);
   end
end
warning off

shwaip

First and foremost:
Why do you have warnings off? There are many bugs in your code that would be indicated by the warning messages, but you turned them off.

Remove that line from your script, type 'warning on' and re-run it. Fix all the warning that come up.

Constantine

I have tried to modify the code that I have written. The main concept is juz to make the point moving out of the specified boundaries (between y=1500 and y=1000) and then guide the point come back to the specified area. There is no certain target or destination set. The code I have modified is like these:-

clc
clear

V= 40; %m/s
delta= 5; %s
t= 1 ;
x(t)= 0; 
y(t)= 1250;
position= [x(t),y(t)];

if y(t) > 1500
    h(t)=-15;
else
    if y(t) < 1000
        h(t)=15;
    else
        h(t)=10;
    end
end

x(t)= x(t)+ delta*V*sin(h(t));
y(t)= y(t)+ delta*V*cos(h(t));
t=t+1;

if x(t)>= 1590
    sprintf('the signal is too weak')
end

figure
plot(x(t),y(t),'s')
axis([0 2000 0 2000])
hold on
xlabel('');
ylabel('');
title('Ship Path');

The main problem is I don't know how to put a stop when x(t) is > than 1590. And also, nothing show up in my graph. I think I might have done some serious mistakes. Hope that you can guide me through these things. Thanks a lot.

Addition: the goal or target can be set as x=1590, y=1250.

shwaip

1. You only change t once, and then you don't recalculate anything.

I've added a while loop that stops after tMax or if the x value gets out of the range. I've also updated the code so that the new calculated value of x is stored in the next time step. It is now doing what you think your code should be doing. However, I think your values for h are not necessarily correct.

clc
clear

V= 40; %m/s
delta= 5; %s
tMax = 20;
t= 1 ;
x(t)= 0;
y(t)= 1250;
while (t < tMax ) && (x(t) < 1590)
    
    position= [x(t),y(t)];
    
    if y(t) > 1500
        h =-15;
    else
        if y(t) < 1000
            h =15;
        else
            h =10;
        end
    end
    
    x(t+1)= x(t)+ delta*V*sin(h);
    y(t+1)= y(t)+ delta*V*cos(h);
    t=t+1;
    
    if x(t)>= 1590
        sprintf('the signal is too weak')
    end
    
end

figure
plot(x,y)
%axis([0 2000 0 2000])
hold on
xlabel('');
ylabel('');
title('Ship Path');

Constantine

Thank you so much for your help!!! shwaip.....really appreciate it........i think there is something wrong with my angle...i will try to modified it...thank you....