Step response in z-domain (ZOH)

 

s = tf('s');
k=6.95   % from root locus plots in s domain
G = (k*100)/((s + 10)*(s + 20));
Gd = c2d(G, 0.1) % zoh is the default method
sys_cl = feedback(G,1)
sys_cld = feedback(Gd,1)
step(sys_cl,'--',sys_cld,'-')

Sampling time = 0.1 sec





Sampling time = 0.01 sec






Sampling time = 0.001 sec



MATLAB’s “c2d” command convert from continuous to discrete transfer functions. The methods of conversion include the Tustin approximation and a zero-order hold on the input to the transfer function.