dcgain

Low-frequency (DC) gain of LTI system

Syntax

``k = dcgain(sys) ``

Description

example

````k = dcgain(sys) ` computes the DC gain `k` of the LTI model `sys`.Continuous TimeThe continuous-time DC gain is the transfer function value at the frequency s = 0. For state-space models with matrices (A, B, C, D), this value is K = D – CA–1B(1)Discrete TimeThe discrete-time DC gain is the transfer function value at z = 1. For state-space models with matrices (A, B, C, D), this value isK = D + C(I – A)–1B(2)```

Examples

collapse all

`load iddata1 z1`

`z1` is an `iddata` object containing the input-output estimation data.

Estimate a process model from the data. Specify that the model has one pole and a time delay term.

`sys = procest(z1,'P1D')`
```sys = Process model with transfer function: Kp G(s) = ---------- * exp(-Td*s) 1+Tp1*s Kp = 9.0754 Tp1 = 0.25655 Td = 0.068 Parameterization: {'P1D'} Number of free coefficients: 3 Use "getpvec", "getcov" for parameters and their uncertainties. Status: Estimated using PROCEST on time domain data "z1". Fit to estimation data: 44.85% FPE: 6.02, MSE: 5.901 ```

Compute the DC gain of the model.

`K = dcgain(sys)`
```K = 9.0754 ```

This DC gain value is stored in the `Kp` property of `sys`.

`sys.Kp`
```ans = 9.0754 ```

Tips

The DC gain is infinite for systems with integrators.

Version History

Introduced before R2006a