# State-Feedback Controller

Discrete-time state-feedback controller with integral action

**Libraries:**

Simscape /
Electrical /
Control /
General Control

## Description

The State-Feedback Controller block implements a discrete-time state-feedback controller with integral action. Use this block to control linear systems with single or multiple inputs and single or multiple outputs. The integral action serves to eliminate steady-state error in the controlled outputs. You can define the controller using a precomputed optimal gain or use the state-space model of your system to generate this gain using pole placement.

### Equations

The integral of the tracking error, *x _{i}*,
is an additional state that ensures zero steady-state error for the closed-loop
system. The extended state vector is

${x}_{e}=\left[\begin{array}{c}x\\ {x}_{i}\end{array}\right],$

Where:

*x*is the state vector.*x*is the integral of the tracking error._{i}*x*is the extended state vector._{e}

Therefore, the control action is

$u=K{x}_{e},$

Where:

*K*is the feedback matrix, that is, the pole placement.*u*is the controller output.

### Assumptions

System state measurement and estimation occur outside the controller.

## Examples

## Ports

### Input

**r** — Plant reference

scalar

Plant system reference signal.

**Data Types: **`single`

| `double`

**x** — State vector

vector

Measured or estimated system state vector.

**Data Types: **`single`

| `double`

**Reset** — Integrator reset

scalar

External reset signal (rising edge) for the integrator.

**Data Types: **`Boolean`

**y** — Plant output

scalar

Plant system output signal.

**Data Types: **`single`

| `double`

### Output

**u** — Controller output

scalar

Control system output signal.

**Data Types: **`single`

| `double`

## Parameters

**State-feedback design** — Controller generation

`State-feedback gain`

(default) | `Desired eigenvalues`

Select the strategy for parameterizing controller gain:

`State-feedback gain`

— Specify the controller gain directly`Desired eigenvalues`

— Specify the plant model and desired eigenvalues from which to generate the controller gain

**State-feedback parameterization** — State-feedback parameterization

`Discrete-time`

(default) | `Continuous-time`

Select the strategy for parameterizing the state-space matrices and desired poles for the controller. The block implementation is discrete regardless of this parameterization.

#### Dependencies

To enable this parameter, set **State-feedback
design** to ```
Desired
eigenvalues
```

.

**Controller matrix** — Controller matrix

[1 1] (default) | matrix

Controller feedback matrix. To determine the controller matrix, if you
have a license for Control System Toolbox™, use the `lqr`

or `lqi`

function.

#### Dependencies

To enable this parameter, set **State-feedback
design** to ```
State-feedback
gain
```

.

**Discrete-time A matrix** — A matrix in discrete time

1 (default) | real scalar or matrix

State matrix of the discrete-time state-space model. The A matrix must be square, with the number of rows and columns equal to the order of the system.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Discrete-time`

.

**Discrete-time B matrix** — B matrix in discrete time

1 (default) | real scalar or matrix

Input matrix of the discrete-time state-space model. The B matrix must have the number of rows equal to the order of the system, and the number of columns equal to the number of system inputs.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Discrete-time`

.

**Discrete-time C matrix** — C matrix in discrete time

1 (default) | real scalar or matrix

Output matrix of the discrete-time state-space model. The C matrix must have the number of rows equal the number of outputs of the system, and the number of columns equal to the order of the system.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Discrete-time`

.

**Discrete-time D matrix** — D matrix in discrete time

1 (default) | real scalar or matrix

Feedthrough matrix of the discrete-time state-space model. The D matrix must have the number of rows equal to the number of system outputs, and the number of columns equal to the number of system inputs.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Discrete-time`

.

**Continuous-time A matrix** — A matrix in continuous time

1 (default) | real scalar or matrix

State matrix of the continuous-time state-space model. The A matrix must be square, with the number of rows and columns equal to the order of the system.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Continuous-time`

.

**Continuous-time B matrix** — B matrix in continuous time

1 (default) | real scalar or matrix

Input matrix of the continuous-time state-space model. The B matrix must have the number of rows equal to the order of the system, and the number of columns equal to the number of system inputs.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Continuous-time`

.

**Continuous-time C matrix** — C matrix in continuous time

1 (default) | real scalar or matrix

Output matrix of the continuous-time state-space model. The C matrix must have the number of rows equal the number of outputs of the system, and the number of columns equal to the order of the system.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Continuous-time`

.

**Continuous-time D matrix** — D matrix in continuous time

1 (default) | real scalar or matrix

Feedthrough matrix of the continuous-time state-space model. The D matrix must have the number of rows equal to the number of system outputs, and the number of columns equal to the number of system inputs.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Continuous-time`

.

**Discretization sample time** — Discretization sample time

0.1 (default) | positive real number

Value used to discretize the state space matrices and also approximate the discrete-time eigenvalues.

#### Dependencies

To enable this parameter, set **State-feedback
parameterization** to
`Continuous-time`

and **Sample time
(-1 for inherited)** to `-1`

.

**Desired eigenvalues (discrete)** — Observer eigenvalues

0 (default) | real vector

Specify the location of the eigenvalues to lie within the unit circle. The controller gain is then calculated based on these eigenvalues. The size of the vector must be equal to the system order plus the number of outputs.

**Control action upper limit** — *u*_{max}

`5`

(default) | scalar greater than the value of the **Control action lower
limit** parameter

_{max}

Upper limit for the control output signal.

**Control action lower limit** — *u*_{min}

`0`

(default) | scalar

_{min}

Lower limit for the control output signal.

**Sample time (-1 for inherited)** — Sampling interval

`-1`

(default) | default value or a positive number

Time interval between samples. If the block is
inside a triggered subsystem, inherit the sample time by setting this
parameter to `-1`

. If this block is in a continuous
variable-step model, specify the sample time explicitly. For more
information, see What Is Sample Time? and
Specify Sample Time.

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

## Version History

**Introduced in R2017b**

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