Solving a system of Second Order Equations
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Trying to solve but not able to get an output
Need the equations of x1 to x5.
m1 = 0.17; m2 = 0.17; m3 = 0.114; m4 = 0.114; m5=0.114;
k = 50; k1 = k; k2 = 0.8*k; k3 = 0.7*k; k4 = 0.6*k; k5=0.6*k; k6=0.9*k;
M = [m1 0 0 0 0; 0 m2 0 0 0; 0 0 m3 0 0; 0 0 0 m4 0; 0 0 0 0 m5];
K = [k1+k2 -k2 0 0 0; -k2 k2+k3 -k3 0 0; 0 -k3 k3+k4 -k4 0; 0 0 -k4 k4+k5 -k5; 0 0 0 -k5 k5+k6];
w = 2*pi*40;
syms x1(t) x2(t) x3(t) x4(t) x5(t)
eqn1 = m1*diff(x1,t,2) + (k1+k2)*x1 - k2*x2 == 5*sin(w*t);
eqn2 = m2*diff(x2,t,2) - k2*x1 + (k2+k3)*x2 - k3*x3 == 5*sin(w*t);
eqn3 = m3*diff(x3,t,2) - k3*x2 + (k3+k4)*x3 - k4*x4 == 5*sin(w*t);
eqn4 = m4*diff(x4,t,2) - k4*x3 + (k4+k5)*x4 - k5*x5 == 5*sin(w*t);
eqn5 = m5*diff(x5,t,2) - k5*x4 + (k5+k6)*x5 == 5*sin(w*t);
eqns = [eqn1; eqn2; eqn3; eqn4; eqn5];
S = dsolve(eqns)
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Réponses (1)
Alan Stevens
le 24 Avr 2022
Not sure there is a symbolic solution, but it's easy enough to get a numerical one:
tspan = [0 1]; % Start and end times
% Initial conditions
% x0 = [x1(0), x2(0), x3(0), x4(0), x5(0), v1(0), v2(0), v3(0), v4(0), v5(0)]
x0 = [1, 0, 0, 0, 0, 0, 0, 0, 0, 0];
[t, x] = ode45(@rates, tspan, x0);
plot(t,x(:,1:5)), grid
xlabel('t'), ylabel('x')
legend('x1','x2','x3','x4','x5')
function dxdt = rates(t, x)
m1 = 0.17; m2 = 0.17; m3 = 0.114; m4 = 0.114; m5=0.114;
k = 50; k1 = k; k2 = 0.8*k; k3 = 0.7*k; k4 = 0.6*k; k5=0.6*k; k6=0.9*k;
w = 2*pi*40;
x1 = x(1); x2 = x(2); x3 = x(3); x4 = x(4); x5 = x(5);
v1 = x(6); v2 = x(7); v3 = x(8); v4 = x(9); v5 = x(10);
f = 5*sin(w*t);
dxdt = [v1; v2; v3; v4; v5;
(f - ((k1+k2)*x1 - k2*x2))/m1;
(f - (- k2*x1 + (k2+k3)*x2 - k3*x3))/m2;
(f - (- k3*x2 + (k3+k4)*x3 - k4*x4))/m3;
(f - (- k4*x3 + (k4+k5)*x4 - k5*x5))/m4;
(f - (- k5*x4 + (k5+k6)*x5))/m5];
end
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