Example 1
Spring-Mass-Damper System
A spring-mass-damper mechanical system is shown in Figure2.2.
Figure 1: Spring-Mass-Damper System
The motion of the mass, denoted by y(t), is described by the differential equation
(1)
The unforced dynamic response y(t) of the spring-mass-damper mechanical system is
(2)
where , , and .
The initial displacement is .
Consider the under-damped case:
Matlab script:
y0=0.15;
wn=sqrt(2); %
zeta=1/(2*sqrt(2)); %
t=[0:0.1:10];
% Compute Unforced Response to an initial condition
c=(y0/sqrt(1-zeta^2)); %
y=c*exp(-zeta*wn*t).*sin(wn*sqrt(1-zeta^2)*t+acos(zeta));
bu=c*exp(-zeta*wn*t); bl=-bu; % envelope -
plot(t,y,t,bu,t,bl), grid on
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