, (). , . , x 1, x 2, , xn t = t 0. xi , xi xi .
1, 2,..., xN x N - , . , , . , . (1.5) , x F (x), (1.5):
(1.5) :
F (x) - N. . , . , . , , . n (Ν = 2 n).
2.4. . . , , . wi (.. , ki, ) m - ( ). , ( ) , , , .
2.5.
(Higham, Higham 2005 (177-179)). :
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θ .
y 1(t) = θ (t) y 2(t) = dθ (t)/ dt, 2- :
m:
function yprime=pendd(t,y)
yprime=[y(2);-sin(y(1))];
m- 0 < t < 8 yazero=[1;1], ybzero=[-5;2], yczero=[5;-2].
m-. . xlim([-5 5]) .
%ppend
tspan=[0 8];
yazero=[1;1];
ybzero=[-5;2];
yczero=[5;-2];
[ta,ya]=ode45(@pendd,tspan,yazero);
[tb,yb]=ode45(@pendd,tspan,ybzero);
[tc,yc]=ode45(@pendd,tspan,yczero);
hold on
plot(ya(:,1),ya(:,2))
plot(yb(:,1),yb(:,2))
plot(yc(:,1),yc(:,2))
xlim([-5 5])
xlabel(''); ylabel('');
gtext('');gtext('');
hold off
grid on
1.
. 1.
, , , , , (Hunt et al. 2008 (. 216-220)). , 1 , 1 , 0.5. , .
(1) |
t , ( = 0 ), y , 9.81 , , .
g Command Window (CW) (1):
g = @(t,x)[x(2);-0.5*x(2)- 9.81*sin(x(1))];
(0) = 0 (0) = 5 CW :
[t, xa] = ode45(g, [0:0.01:20], [0 5]);
plot(xa(:, 1), xa(:, 2))
grid on
. 2 t 0 < t <20 . ( MATLAB ode45, ode45.)
(0; 5), t, , (0; 0). , , t = 20. , , ( ), , .
. 2.
10.
[t, xa] = ode45(g, [0:0.01:20], [0 10]);
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. 3.
(. 3.) , 14 , , (12.5; 0). , (4π; 0), 4π , 0 . . , , π, . 3π.