feedback system design

[Bhuvanesh123]

i am little bit late to the course,my question is how making the vehicle to get into almost desired speed equation is u=ke.
e=r-y
if on speed of vehicle is 30 km/hr.my reference speed is 70 km/hr.
for the first time we get e=40 as feedback.and further this 40 is carried out in what way in order to get the vehicle to 70 km/hr speed.please help me.thank you in advance

r -reference speed
y-output feed back to input
k-time instant

 

[FvM]

I y is the actual speed, what is u, what's the meaning of u=ke?

 

[Bhuvanesh123]

u is reference signal.Focus of my question is why error should be zero and how it could be zero and why error should be zero a.explain detailly please.thank you in advance