## Documentation Center |

The Idmodel block simulates a linear model in the MATLAB^{®} workspace.

Input signal to the model.

Simulated output from the model.

**Identified model**Name of an estimated linear model in the MATLAB workspace. The model must be an

`idss`,`idgrey`,`idpoly`,`idtf`, or`idproc`object.The block supports continuous-time or discrete-time models with or without input-output delays.

**Initial states (state space only: idss, idgrey)**Initial states for state-space (

`idss`) and grey-box (`idgrey`) models. Initial states must be a vector of length equal to the order of the model.For models other than

`idss`and`idgrey`, initial conditions are zero.In some situations, you may want to reproduce the results in the Model Output plot window in the System Identification Tool or those of the

`compare`plot. To do so:Convert the identified model into state-space form (

`idss`model), and use the state-space model in the block.Compute the initial state values that produce the best fit between the model output and the measured output signal using

`findstates(idParametric)`.Specify the same input signal for simulation that you used as the validation data in the Tool or in the

`compare`plot.For example:

% Convert to state-space model mss = idss(m); % Estimate initial states from data X0 = findstates(mss,z);

`z`is the data set you used for validating the model`m`. Use the model`mss`and initial states`X0`in the Idmodel block to perform the simulation.

**Add noise**Select to add noise. When selected, Simulink

^{®}derives the noise amplitude from the model property`model.NoiseVariance`and the matrices or polynomials that determine the color of the additive noise.For continuous-time models, the ideal variance of the noise term is infinite. In reality, you see a band-limited noise that takes into account the time constants of the system. You can interpret the resulting simulated output as filtered using a lowpass filter with a passband that does not distort the dynamics from the input.

**Noise seed(s)**Seed, specified as an integer, that forces the simulation to add the same noise to the output every time you simulate the model. Applies only when you select the

**Add noise**check box. For more information about using seeds, see`rand`in the MATLAB documentation.For multi-output models, you can use independent noise realizations that generate the outputs with additive noise. Enter a vector of

`N`entries, where_{y}`N`is the number of output channels._{y}For random restarts that vary from one simulation to another, leave the field empty.

`findstates(idParametric)` | `idpoly` | `idproc` | `idss` | `idtf` | `sim`

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