pi = 3.14;
y = @(x) (50*pi*x) .* (0<x & x<1/150) +  (pi/3) .* ((1/150<=x) & (x<=3001/150)) + ((3002*pi/3-50*pi*x) .* ((3001/150 <= x) & (x < 1501/75)));%r(t)
x = 0:(1/150):(1501/75);
eqn ='0.7274 * v = 0.00072*D3y + 0.07206*D2y + 0.44244*Dy';
inits = 'y(0)=0, Dy(0) = 0, Dy(0.01) = 50';
v=dsolve(eqn,inits,'x');
z=eval(vectorize(v));
plot(x,v,'g'),grid on