altimeterSensor

Altimeter simulation model

Description

The altimeterSensor System object™ models receiving data from an altimeter sensor.

To model an altimeter:

1. Create the altimeterSensor object and set its properties.

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

altimeter = altimeterSensor

altimeter = altimeterSensor('ReferenceFrame',RF)

altimeter = altimeterSensor(___,Name,Value)

Description

altimeter = altimeterSensor returns an altimeterSensor System object that simulates altimeter readings.

altimeter = altimeterSensor('ReferenceFrame',RF) returns an altimeterSensor System object that simulates altimeter readings relative to the reference frame RF. Specify RF as 'NED' (North-East-Down) or 'ENU' (East-North-Up). The default value is 'NED'.

altimeter = altimeterSensor(___,Name,Value) sets each property Name to the specified Value. Unspecified properties have default values.

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

SampleRate — Update rate of sensor (Hz)

1 (default) | positive scalar

Update rate of sensor in Hz, specified as a positive scalar.

Data Types: single | double

ConstantBias — Constant offset bias (m)

0 (default) | scalar

Constant offset bias in meters, specified as a scalar.

Tunable: Yes

Data Types: single | double

NoiseDensity — Power spectral density of sensor noise (m/√Hz)

0 (default) | nonnegative scalar

Power spectral density of sensor noise in m/√Hz, specified as a nonnegative scalar.

Tunable: Yes

Data Types: single | double

BiasInstability — Instability of bias offset (m)

0 (default) | nonnegative scalar

Instability of the bias offset in meters, specified as a nonnegative scalar.

Tunable: Yes

Data Types: single | double

DecayFactor — Bias instability noise decay factor

0 (default) | scalar in the range [0,1]

Bias instability noise decay factor, specified as a scalar in the range [0,1]. A decay factor of 0 models the bias instability noise as a white noise process. A decay factor of 1 models the bias instability noise as a random walk process.

Tunable: Yes

Data Types: single | double

RandomStream — Random number source

'Global stream' (default) | 'mt19937ar with seed'

Random number source, specified as a character vector or string:

• 'Global stream' –– Random numbers are generated using the current global random number stream.

• 'mt19937ar with seed' –– Random numbers are generated using the mt19937ar algorithm with the seed specified by the Seed property.

Data Types: char | string

Seed — Initial seed

67 (default) | nonnegative integer scalar

Initial seed of an mt19937ar random number generator algorithm, specified as a nonnegative integer scalar.

Dependencies

To enable this property, set RandomStream to 'mt19937ar with seed'.

Data Types: single | double

Usage

Syntax

altimeterReadings = altimeter(position)

Description

altimeterReadings = altimeter(position) generates an altimeter sensor altitude reading from the position input.

Input Arguments

position — Position of sensor in local navigation coordinate system (m)

N-by-3 matrix

Position of sensor in the local navigation coordinate system, specified as an N-by-3 matrix with elements measured in meters. N is the number of samples in the current frame.

Data Types: single | double

Output Arguments

altimeterReadings — Altitude of sensor relative to local navigation coordinate system (m)

N-element column vector

Altitude of sensor relative to the local navigation coordinate system in meters, returned as an N-element column vector. N is the number of samples in the current frame.

Data Types: single | double

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Generate Noisy Altimeter Readings from Stationary Input

Create an altimeterSensor System object™ to model receiving altimeter sensor data. Assume a typical one Hz sample rate and a 10 minute simulation time. Set ConstantBias to 0.01, NoiseDensity to 0.05, BiasInstability to 0.05, and DecayFactor to 0.5.

Fs = 1;
duration = 60*10;
numSamples = duration*Fs;


altimeter = altimeterSensor('SampleRate',Fs, ...
                            'ConstantBias',0.01, ...
                            'NoiseDensity',0.05, ...
                            'BiasInstability',0.05, ...
                            'DecayFactor',0.5);

truePosition = zeros(numSamples,3);

Call altimeter with the specified truePosition to model noisy altimeter readings from a stationary platform.

altimeterReadings = altimeter(truePosition);

Plot the true position and the altimeter sensor readings for height.

t = (0:(numSamples-1))/Fs;

plot(t,altimeterReadings)
hold on
plot(t,truePosition(:,3),'LineWidth',2)
hold off
title('Altimeter Readings')
xlabel('Time (s)')
ylabel('Height (m)')
legend('Altimeter Readings','Ground Truth')

Extended Capabilities

C/C++ Code Generation

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

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).

Version History

Introduced in R2019a