the simple control law u=theta_1***y_p+theta_2***r and tuning law theta_1'=-gamma1***sign(b_p)***e***y_p theta_2'=-gamma2***sign(b_p)***e***r

to make the plant

y_p'=a_p***y_p+b_p***u

to track the output of refrence model y_m'=-4***y_m+4***r

where e=y_p-y_m

It is already shown that when r is a constant, there will be infinite pairs of ultimate values of theta1 and theta2; while r=sin(3*t), the ultimate values of theta1 and theta2 must be fixed.

However, anybody knows is there any difference in the tracking performance when r is different. I find when r=sin(3*t), it takes less time for e to converge to zero. Am I right?