steady state error command

Is there a command that will give the steady state error of the the response of a transfer function

Answer 1

[Paulo Silva]

SP=5; %input value, if you put 1 then is the same as step(sys)
[y,t]=step(SP*sys); %get the response of the system to a step with amplitude SP
sserror=abs(SP-y(end)) %get the steady state error

[Naufal Indrastoto]

I have already tried this and it says undefined function or variable 'sys'. Could please you explain more about it?

[Eric Chua]

sys is your transfer function

[HanJie Chong]

The result of this code is already in %?

EXP: 0.4= 40% or 0.4%

[Walter Roberson]

No, sserror would be absolute value, not relative value. You would have to divide by SP to get relative value as a fraction, which you could then multiply by 100 to get percentage.

[Mohammad Hosein Forghani]

Thanks, it worked for me

[irshad maz]

what is SP stand for Sir

[JAMES KEEN]

@irshad maz I believe it means setpoint i.e. the point of which you want the system response to settles at.

Answer 2

[Mohammad Hosein Forghani]

Another approach theoretically would be final value theorem, I might also implement that in MATLAB.

Answer 3

[Anish Mitra]

Assuming your system is stable, you can use the dcgain command to compute the low frequency gain for an LTI system. Based on final value theorem (as mentioned above) this is the steady-state value of the step response.