Hi @Nguyen Hieu
Instead of using the If-Else statement, I took the pure math approach of describing the shapes of the road bumps.
By the way, I think there is an error in the 
profile, where the profile should be defined over the interval 
.
profile, where the profile should be defined over the interval .a = 0.11; % (m)
V = 20; % (m/s)
lambda = 5; % (m)
lf = 1;
lr = 1.5;
Tspan = 5; % Can be changed to 20 seconds
Tf = linspace(0, Tspan, 1000*Tspan+1);
T1 = 1;
T2 = T1 + lambda/V;
wf = (a/2)*(1 - cos((2*pi*V*Tf)/lambda)).*(heaviside(Tf - T1) - heaviside(Tf - T2));
Td = T1 + (lf + lr)/V;
Tr = Tf + Td;
T3 = Td + lambda/V;
wr = (a/2)*(1 - cos((2*pi*V*Tr)/lambda)).*(heaviside(Tf - Td) - heaviside(Tf - T3));
plot(Tf, wf), hold on
plot(Tf, wr, '--'), grid on
xlabel('Time, (sec)'),
ylabel('Road Disturbance, w (m)')
title('Road Profiles')
annotation('textarrow', [1/5 1.45/5], [0.08/0.12 0.07/0.12], 'String', 'w_{f}')
annotation('textarrow', [2/5 1.65/5], [0.08/0.12 0.07/0.12], 'String', 'w_{r}')
