# realp

Real tunable parameter

## Syntax

p = realp(paramname,initvalue)

## Description

p = realp(paramname,initvalue) creates a tunable real-valued parameter with name specified by paramname and initial value initvalue. Tunable real parameters can be scalar- or matrix- valued.

## Input Arguments

 paramname Name of the realp parameter p, specified as a character vector such as 'a' or 'zeta'. This input argument sets the value of the Name property of p. initvalue Initial numeric value of the parameter p. initvalue can be a real scalar value or a 2-dimensional matrix.

## Output Arguments

 p realp parameter object.

## Properties

 Name Name of the realp parameter object, stored as a character vector. The value of Name is set by the paramname input argument to realp and cannot be changed. Value Value of the tunable parameter. Value can be a real scalar value or a 2-dimensional matrix. The initial value is set by the initvalue input argument. The dimensions of Value are fixed on creation of the realp object. Minimum Lower bound for the parameter value. The dimension of the Minimum property matches the dimension of the Value property. For matrix-valued parameters, use indexing to specify lower bounds on individual elements: p = realp('K',eye(2)); p.Minimum([1 4]) = -5; Use scalar expansion to set the same lower bound for all matrix elements: p.Minimum = -5; Default: -Inf for all entries Maximum Upper bound for the parameter value. The dimension of the Maximum property matches the dimension of the Value property. For matrix-valued parameters, use indexing to specify upper bounds on individual elements: p = realp('K',eye(2)); p.Maximum([1 4]) = 5; Use scalar expansion to set the same upper bound for all matrix elements: p.Maximum = 5; Default: Inf for all entries Free Boolean value specifying whether the parameter is free to be tuned. Set the Free property to 1 (true) for tunable parameters, and 0 (false) for fixed parameters. The dimension of the Free property matches the dimension of the Value property. Default: 1 (true) for all entries

## Examples

collapse all

In this example, you will create a low-pass filter with one tunable parameter a:

$F=\frac{a}{s+a}$

Since the numerator and denominator coefficients of a tunableTF block are independent, you cannot use tunableTF to represent F. Instead, construct F using the tunable real parameter object realp.

Create a real tunable parameter with an initial value of 10.

a = realp('a',10)
a =
Name: 'a'
Value: 10
Minimum: -Inf
Maximum: Inf
Free: 1

Real scalar parameter.

Use tf to create the tunable low-pass filter F.

numerator = a;
denominator = [1,a];
F = tf(numerator,denominator)
F =

Generalized continuous-time state-space model with 1 outputs, 1 inputs, 1 states, and the following blocks:
a: Scalar parameter, 2 occurrences.

Type "ss(F)" to see the current value, "get(F)" to see all properties, and "F.Blocks" to interact with the blocks.

F is a genss object which has the tunable parameter a in its Blocks property. You can connect F with other tunable or numeric models to create more complex control system models. For an example, see Control System with Tunable Components.

Create a matrix with tunable diagonal elements and with off-diagonal elements fixed to zero.

Create a parametric matrix whose initial value is the identity matrix.

p = realp('P',eye(2));

p is a 2-by-2 parametric matrix. Since the initial value is the identity matrix, the off-diagonal initial values are zero.

Fix the values of the off-diagonal elements by setting the Free property to false.

p.Free(1,2) = false;
p.Free(2,1) = false;

## Tips

• Use arithmetic operators (+, -, *, /, \, and ^) to combine realp objects into rational expressions or matrix expressions. You can use the resulting expressions in model-creation functions such as tf, zpk, and ss to create tunable models. For more information about tunable models, see Models with Tunable Coefficients in the Control System Toolbox™ User's Guide.