# Why we use Transfer Function to represent/describe a Dynamic Model?

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Bob on 6 May 2016
Answered: Azzi Abdelmalek on 6 May 2016
Why we use Transfer Function to represent/describe a Dynamic Model?
%%Parameters
m1 = 2500; % Sprung Mass (kg)
m2 = 320; % Unsprung Mass (kg)
k1 = 80000; % Suspension Stiffness (N/m)
k2 = 500000; % Wheel and Tire Stiffness (N/m)
b1 = 350; % Suspension Damping Coefficient (N*s/m)
b2 = 15020; % Wheel and Tire Damping Coefficient (N*s/m)
%%Dynamic Model
% Displacement of Mass 1, G1(s) = X1(s)/W(s)
num1 = [(0) (0) (b1*b2) (b1*k2+b2*k1) (k1*k2)]; % Output X1(s)
den1 = [(m1*m2) (m1*b1+m1*b2+m2*b1) (m1*k1+m1*k2+m2*k1+b1*b2) (b1*k2+k1*b2) (k1*k2)]; % Input W(s)
G1 = tf(num1,den1);
% Displacement of Mass 2, G2(s) = X2(s)/W(s)
num2 = [(0) (m1*b2) (m1*k2+b1*b2) (b1*k2+b2*k1) (k1*k2)]; % Output X2(s)
den2 = [(m1*m2) (m1*b1+m1*b2+m2*b1) (m1*k1+m1*k2+m2*k1+b1*b2) (b1*k2+k1*b2) (k1*k2)]; % Input W(s)
G2 = tf(num2,den2);

Azzi Abdelmalek on 6 May 2016