Discussion:
Steady state error
(too old to reply)
Adrian
2012-12-12 08:05:10 UTC
Permalink
The previous response to this is not correct. The steady state error can be calculated in two ways depending on the type of transfer function:

abs(dcgain(sys)-1)
for a closed loop transfer function

If using an openloop transfer function, the function must first be closed
abs(dcgain(feedback(sys,1))-1) % for unity feedback

Alternatively if using an openloop transfer function with unity feedback, then the steady state step error is
1/(1+dcgain(sys))

where dcgain(sys) is the static error constant Kp
Hi
I'm looking to calculate the steady state error of a transfer function
with a unit step input in Matlab. I can do this by using step() to draw
a plot of the response, but is there a function that would tell me the
error without needing to read it off graphically?
Thanks,
--
Jon
A
2012-12-12 08:18:14 UTC
Permalink
Sorry, the closed loop transfer function's steady state error is:

abs(1-dcgain(sys))

If using an openloop transfer function, the function must first be closed
abs(1-dcgain(feedback(sys,1))) % for unity feedback

Alternatively if using an openloop transfer function with unity feedback, then the steady state step error is
1/(1+dcgain(sys))

where dcgain(sys) is the static error constant Kp
Post by Adrian
abs(dcgain(sys)-1)
for a closed loop transfer function
Hi
I'm looking to calculate the steady state error of a transfer function
with a unit step input in Matlab. I can do this by using step() to draw
a plot of the response, but is there a function that would tell me the
error without needing to read it off graphically?
Thanks,
--
Jon
Loading...