sonarSensor

Generate detections from sonar emissions

Description

The sonarSensor System object™ creates a statistical model for generating detections from infrared emissions. You can generate detections from active or passive sonar systems. You can use the sonarSensor object in a scenario that models moving and stationary platforms using trackingScenario. The infrared sensor can simulate real detections with added random noise and also generate false alarm detections. In addition, you can use this object to create input to trackers such as trackerGNN or trackerTOMHT.

This object enables you to configure an electronically scanning sonar. A scanning sonar changes the look angle between updates by stepping the electronic position of the beam in increments of the angular span specified in the FieldOfView property. The sonar scans the total region in azimuth and elevation defined by the sonar electronic scan limits, ElectronicScanLimits. If the scanning limits for azimuth or elevation are set to [0 0], no scanning is performed along that dimension for that scan mode. If the maximum electronic scan rate for azimuth or elevation is set to zero, no electronic scanning is performed along that dimension.

To generate sonar detections:

  1. Create the sonarSensor 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? (MATLAB).

Creation

Syntax

sensor = sonarSensor(SensorIndex)
sensor = sonarSensor(SensorIndex,'No scanning')
sensor = sonarSensor(SensorIndex,'Raster')
sensor = sonarSensor(SensorIndex,'Rotator')
sensor = sonarSensor(SensorIndex,'Sector')
sensor = sonarSensor(___,Name,Value)

Description

sensor = sonarSensor(SensorIndex) creates a sonar detection generator object with default property values.

sensor = sonarSensor(SensorIndex,'No scanning') is a convenience syntax that creates a sonarSensor that stares along the sonar transducer boresight direction. No electronic scanning is performed. This syntax sets the ScanMode property to 'No scanning'.

sensor = sonarSensor(SensorIndex,'Raster') is a convenience syntax that creates a sonarSensor object that electronically scans a raster pattern. The raster span is 90° in azimuth from –45° to +45° and in elevation from the horizon to 10° above the horizon. See Convenience Syntaxes for the properties set by this syntax.

sensor = sonarSensor(SensorIndex,'Rotator') is a convenience syntax that creates a sonarSensor object that electronically scans 360° in azimuth by electronically rotating the transducer at a constant rate. When you set HasElevation to true, the sonar transducer electronically points towards the center of the elevation field of view. See Convenience Syntaxes for the properties set by this syntax.

sensor = sonarSensor(SensorIndex,'Sector') is a convenience syntax to create a sonarSensor object that electronically scans a 90° azimuth sector from –45° to +45°. Setting HasElevation to true, points the sonar transducer towards the center of the elevation field of view. Beams are stacked electronically to process the entire elevation spanned by the scan limits in a single dwell. See Convenience Syntaxes for the properties set by this syntax.

example

sensor = sonarSensor(___,Name,Value) sets properties using one or more name-value pairs after all other input arguments. Enclose each property name in quotes. For example, sonarSensor('DetectionCoordinates','Sensor cartesian','MaxRange',200) creates a sonar detection generator that reports detections in the sensor Cartesian coordinate system and has a maximum detection range of 200 meters. If you specify the sensor index using the SensorIndex property, you can omit the SensorIndex input.

Properties

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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 (MATLAB).

Unique sensor identifier, specified as a positive integer. This property distinguishes detections that come from different sensors in a multi-sensor system. When creating a sonarSensor system object, you must either specify the SensorIndex as the first input argument in the creation syntax, or specify it the value for the SensorIndex property in the creation syntax.

Example: 2

Data Types: double

Sensor update rate, specified as a positive scalar. This interval must be an integer multiple of the simulation time interval defined by trackingScenario. The trackingScenario object calls the sonar sensor at simulation time intervals. The sonar generates new detections at intervals defined by the reciprocal of the UpdateRate property. Any update requested to the sensor between update intervals contains no detections. Units are in hertz.

Example: 5

Data Types: double

Detection mode, specified as 'passive' or 'monostatic'. When set to 'passive', the sensor operates passively. When set to 'monostatic', the sensor generates detections from reflected signals originating from a collocated sonar emitter.

Example: 'Monostatic'

Data Types: char | string

Unique monostatic emitter index, specified as a positive integer. The emitter index identifies the monostatic sonar emitter providing the reference signal to the sensor.

Example: 404

Dependencies

Set this property when the DetectionMode property is set to 'monostatic'.

Data Types: double

Sensor location on platform, specified as a 1-by-3 real-valued vector. This property defines the coordinates of the sensor with respect to the platform origin. The default value specifies that the sensor origin is at the origin of its platform. Units are in meters.

Example: [.2 0.1 0]

Data Types: double

Orientation of the sensor with respect to the platform, specified as a three-element real-valued vector. Each element of the vector corresponds to an intrinsic Euler angle rotation that carries the body axes of the platform to the sensor axes. The three elements define the rotations around the z-, y-, and x-axes, in that order. The first rotation rotates the platform axes around the z-axis. The second rotation rotates the carried frame around the rotated y-axis. The final rotation rotates the frame around the carried x-axis. Units are in degrees.

Example: [10 20 -15]

Data Types: double

Fields of view of sensor, specified as a 2-by-1 vector of positive real values, [azfov;elfov]. The field of view defines the total angular extent spanned by the sensor. Each component must lie in the interval (0,180]. Targets outside of the field of view of the sonar are not detected. Units are in degrees.

Example: [14;7]

Data Types: double

Scanning mode of sonar, specified as 'Electronic' or 'No scanning'.

Scan Modes

ScanModePurpose
'Electronic'The sonar scans electronically across the azimuth and elevation limits specified by the ElectronicScanLimits property. The scan direction increments by the sonar field of view angle between dwells.
'No scanning'The sonar beam points along the transducer boresight defined by the mountingAngles property.

Example: 'No scanning'

Data Types: char

This property is read-only.

Current mechanical scan angle of sonar, returned as a scalar or real-valued 2-by-1 vector. When HasElevation is true, the scan angle takes the form [Az; El]. Az and El represent the azimuth and elevation scan angles, respectively, relative to the mounted angle of the sonar on the platform. When HasElevation is false, the scan angle is a scalar representing the azimuth scan angle.

Data Types: double

Angular limits of electronic scan directions of sonar, specified as a real-valued, 1-by-2 row vector or a real-valued 2-by-2 matrix. The electronic scan limits define the minimum and maximum electronic angles the sonar can scan from its current mechanical direction.

When HasElevation is true, the scan limits take the form [minAz maxAz; minEl maxEl]. minAz and maxAz represent the minimum and maximum limits of the azimuth angle scan. minEl and maxEl represent the minimum and maximum limits of the elevation angle scan. When HasElevation is false, the scan limits take the form [minAz maxAz]. If you specify the scan limits as a 2-by-2 matrix but set HasElevation to false, the second row of the matrix is ignored.

Azimuthal scan limits and elevation scan limits must lie within the closed interval [-90° 90°]. Units are in degrees.

Example: [-90 90;0 85]

Dependencies

To enable this property, set the ScanMode property to 'Electronic'.

Data Types: double

This property is read-only.

Current electronic scan angle of sonar, returned as a scalar or 1-by-2 column vector. When HasElevation is true, the scan angle takes the form [Az;El]. Az and El represent the azimuth and elevation scan angles, respectively. When HasElevation is false, the scan angle is a scalar representing the azimuth scan angle.

Dependencies

To enable this property, set the ScanMode property to 'Electronic'.

Data Types: double

This property is read-only.

Look angle of sensor, specified as a scalar or real-valued 2-by-1 vector. Look angle depends on the electronic angle set in the ScanMode property.

ScanModeLookAngle
'Electronic'ElectronicAngle
'No scanning'0

When HasElevation is true, the look angle takes the form [Az;El]. Az and El represent the azimuth and elevation look angles, respectively. When HasElevation is false, the look angle is a scalar representing the azimuth look angle.

Enable the sonar to measure target elevation angles and to scan in elevation, specified as false or true. Set this property to true to model a sonar sensor that can estimate target elevation and scan in elevation.

Data Types: logical

Center frequency of sonar band, specified as a positive scalar. Units are in hertz.

Example: 25.5e3

Data Types: double

Sonar waveform bandwidth, specified as a positive scalar. Units are in hertz.

Example: 1.5e3

Data Types: double

Types of detected waveforms, specified as a nonnegative integer-valued L-element vector.

Example: [1 4 5]

Data Types: double

Probability of correct classification of a detected waveform, specified as a positive scalar, a real-valued nonnegative L-element vector, or a real-valued nonnegative L-by-L matrix. Matrix values range from 0 through 1 and matrix rows must sum to 1. L is the number of waveform types that the sensor can detect, as indicated by the value set in the WaveformTypes property. The (i,j) matrix element represents the probability of classifying the ith waveform as the jth waveform. When specified as a scalar from 0 through 1, the value is expanded along the diagonal of the confusion matrix. When specified as a vector, it must have the same number of elements as the WaveformTypes property. When defined as a scalar or a vector, the off diagonal values are set to (1-val)/(L-1).

Data Types: double

Spectrum-level ambient isotropic noise, specified as a scalar. Units are in dB relative to the intensity of a plane wave with 1 μPa rms pressure in a 1-hertz frequency band.

Example: 25

Data Types: double

False alarm report rate within each resolution cell, specified as a positive scalar in the range [10–7,10–3]. Units are dimensionless. Resolution cells are determined from the AzimuthResolutionproperty and the ElevationResolution property when enabled.

Example: 1e-5

Data Types: double

Azimuth resolution of the sonar, specified as a positive scalar. The azimuth resolution defines the minimum separation in azimuth angle at which the sonar can distinguish two targets. The azimuth resolution is typically the 3-dB downpoint of the azimuth angle beamwidth of the sonar. Units are in degrees.

Data Types: double

Elevation resolution of the sonar, specified as a positive scalar. The elevation resolution defines the minimum separation in elevation angle at which the sonar can distinguish two targets. The elevation resolution is typically the 3-dB downpoint in the elevation angle beamwidth of the sonar. Units are in degrees.

Dependencies

To enable this property, set the HasElevation property to true.

Data Types: double

Range resolution of the sonar, specified as a positive scalar. The range resolution defines the minimum separation in range at which the sonar can distinguish between two targets. Units are in meters.

Data Types: double

Range rate resolution of the sonar, specified as a positive scalar. The range rate resolution defines the minimum separation in range rate at which the sonar can distinguish between two targets. Units are in meters per second.

Dependencies

To enable this property, set the HasRangeRate property to true.

Data Types: double

Azimuth bias fraction of the sonar, specified as a nonnegative scalar. The azimuth bias is expressed as a fraction of the azimuth resolution specified in AzimuthResolution. This value sets a lower bound on the azimuthal accuracy of the sonar. This value is dimensionless.

Data Types: double

Elevation bias fraction of the sonar, specified as a nonnegative scalar. Elevation bias is expressed as a fraction of the elevation resolution specified by the value of the ElevationResolution property. This value sets a lower bound on the elevation accuracy of the sonar. This value is dimensionless.

Dependencies

To enable this property, set the HasElevation property to true.

Data Types: double

Range bias fraction of the sonar, specified as a nonnegative scalar. Range bias is expressed as a fraction of the range resolution specified in RangeResolution. This property sets a lower bound on the range accuracy of the sonar. This value is dimensionless.

Data Types: double

Range rate bias fraction of the sonar, specified as a nonnegative scalar. Range rate bias is expressed as a fraction of the range rate resolution specified in RangeRateResolution. This property sets a lower bound on the range-rate accuracy of the sonar. This value is dimensionless.

Dependencies

To enable this property, set the HasRangeRate property to true.

Data Types: double

Enable the sonar to measure target range rates, specified as false or true. Set this property to true to model a sonar sensor that can measure target range rate. Set this property to false to model a sonar sensor that cannot measure range rate.

Data Types: logical

Enable range ambiguities, specified as false or true. Set this property to true to enable range ambiguities by the sensor. In this case, the sensor cannot resolve range ambiguities for targets at ranges beyond the MaxUnambiguousRange are wrapped into the interval [0 MaxUnambiguousRange]. When false, targets are reported at their unambiguous range.

Data Types: logical

Enable range-rate ambiguities, specified as false or true. Set to true to enable range-rate ambiguities by the sensor. When true, the sensor does not resolve range rate ambiguities and target range rates beyond the MaxUnambiguousRadialSpeed are wrapped into the interval [0,MaxUnambiguousRadialSpeed]. When false, targets are reported at their unambiguous range rate.

Dependencies

To enable this property, set the HasRangeRate property to true.

Data Types: logical

Maximum unambiguous range, specified as a positive scalar. Maximum unambiguous range defines the maximum range for which the sonar can unambiguously resolve the range of a target. When HasRangeAmbiguities is set to true, targets detected at ranges beyond the maximum unambiguous range are wrapped into the range interval [0,MaxUnambiguousRange]. This property applies to true target detections when you set the HasRangeAmbiguities property to true.

This property also applies to false target detections when you set the HasFalseAlarms property to true. In this case, the property defines the maximum range for false alarms.

Units are in meters.

Example: 5e3

Dependencies

To enable this property, set the HasRangeAmbiguities property to true or set the HasFalseAlarms property to true.

Data Types: double

Maximum unambiguous radial speed, specified as a positive scalar. Radial speed is the magnitude of the target range rate. Maximum unambiguous radial speed defines the radial speed for which the sonar can unambiguously resolve the range rate of a target. When HasRangeRateAmbiguities is set to true, targets detected at range rates beyond the maximum unambiguous radial speed are wrapped into the range rate interval [-MaxUnambiguousRadialSpeed, MaxUnambiguousRadialSpeed]. This property applies to true target detections when you set HasRangeRateAmbiguities property to true.

This property also applies to false target detections obtained when you set both the HasRangeRate and HasFalseAlarms properties to true. In this case, the property defines the maximum radial speed for which false alarms can be generated.

Units are in meters per second.

Dependencies

To enable this property, set HasRangeRate and HasRangeRateAmbiguities to true and/or set HasRangeRate and HasFalseAlarms to true.

Data Types: double

Enable the optional input argument that passes the current estimate of the sensor platform pose to the sensor, specified as false or true. When true, pose information is added to the MeasurementParameters structure of the reported detections. Pose information lets tracking and fusion algorithms estimate the state of the target detections in the north-east-down (NED) frame.

Data Types: logical

Enable addition of noise to sonar sensor measurements, specified as true or false. Set this property to true to add noise to the sonar measurements. Otherwise, the measurements have no noise. Even if you set HasNoise to false, the object still computes the MeasurementNoise property of each detection.

Data Types: logical

Enable creating false alarm sonar measurements, specified as true or false. Set this property to true to report false alarms. Otherwise, only actual detections are reported.

Data Types: logical

Source of maximum number of detections reported by the sensor, specified as 'Auto' or 'Property'. When this property is set to 'Auto', the sensor reports all detections. When this property is set to 'Property', the sensor reports up to the number of detections specified by the MaxNumDetections property.

Data Types: char

Maximum number of detections reported by the sensor, specified as a positive integer. Detections are reported in order of distance to the sensor until the maximum number is reached.

Dependencies

To enable this property, set the MaxNumDetectionsSource property to 'Property'.

Data Types: double

Coordinate system of reported detections, specified as:

  • 'Scenario' — Detections are reported in the rectangular scenario coordinate frame. The scenario coordinate system is defined as the local NED frame at simulation start time. To enable this value, set the HasINS property to true.

  • 'Body' — Detections are reported in the rectangular body system of the sensor platform.

  • 'Sensor rectangular' — Detections are reported in the sonar sensor rectangular body coordinate system.

  • 'Sensor spherical' — Detections are reported in a spherical coordinate system derived from the sensor rectangular body coordinate system. This coordinate system is centered at the sonar sensor and aligned with the orientation of the sonar on the platform.

Example: 'Sensor spherical'

Data Types: char

Usage

Syntax

dets = sensor(sonarsigs,simTime)
dets = sensor(sonarsigs,txconfigs,simTime)
dets = sensor(___,ins,simTime)
[dets,numDets,config] = sensor(___)

Description

dets = sensor(sonarsigs,simTime) creates passive detections, dets, from sonar emissions, sonarsigs, at the current simulation time, simTime. The sensor generates detections at the rate defined by the UpdateRate property.

dets = sensor(sonarsigs,txconfigs,simTime) also specifies emitter configurations, txconfigs, at the current simulation time.

dets = sensor(___,ins,simTime) also specifies the inertial navigation system (INS) estimated sensor platform pose, ins. INS information is used by tracking and fusion algorithms to estimate the target positions in the NED frame.

To enable this syntax, set the HasINS property to true.

[dets,numDets,config] = sensor(___) also returns the number of valid detections reported, numValidDets, and the configuration of the sensor, config, at the current simulation time.

Input Arguments

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Sonar emissions, specified as an array of sonarEmission objects.

Emitter configurations, specified as an array of structures. Each structure has these fields:

FieldDescription
EmitterIndex

Unique emitter index

IsValidTime

Valid emission time, returned as 0 or 1. IsValidTime is 0 when emitter updates are requested at times that are between update intervals specified by UpdateInterval.

IsScanDone

IsScanDone is true when the emitter has completed a scan.

FieldOfView

Field of view of emitter.

MeasurementParameters

MeasurementParameters is an array of structures containing the coordinate frame transforms needed to transform positions and velocities in the top-level frame to the current emitter frame.

Data Types: struct

Sensor platform pose obtained from the inertial navigation system (INS), specified as a structure.

Platform pose information from an inertial navigation system (INS) is a structure which has these fields:

FieldDefinition
Position

Position of the GPS receiver in the local NED coordinate system specified as a real-valued 1-by-3 vector. Units are in meters.

Velocity

Velocity of the GPS receiver in the local NED coordinate system specified as a real-valued 1-by-3 vector. Units are in meters per second.

Orientation

Orientation of the INS with respect to the local NED coordinate system specified as a scalar quaternion or a 3-by-3 real-valued orthonormal frame rotation matrix. Defines the frame rotation from the local NED coordinate system to the current INS body coordinate system. This is also referred to as a "parent to child" rotation.

Dependencies

To enable this argument, set the HasINS property to true.

Data Types: struct

Current simulation time, specified as a positive scalar. The trackingScenario object calls the sonar sensor at regular time intervals. The sonar sensor generates new detections at intervals defined by the UpdateInterval property. The value of the UpdateInterval property must be an integer multiple of the simulation time interval. Updates requested from the sensor between update intervals contain no detections. Units are in seconds.

Example: 10.5

Data Types: double

Output Arguments

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Sensor detections, returned as a cell array of objectDetection objects. Each object has these properties:

PropertyDefinition
TimeMeasurement time
MeasurementObject measurements
MeasurementNoiseMeasurement noise covariance matrix
SensorIndexUnique ID of the sensor
ObjectClassIDObject classification
MeasurementParametersParameters used by initialization functions of nonlinear Kalman tracking filters
ObjectAttributesAdditional information passed to tracker

Measurement and MeasurementNoise are reported in the coordinate system specified by the DetectionCoordinates property.

Number of detections reported, returned as a nonnegative integer.

  • When the MaxNumDetectionsSource property is set to 'Auto', numDets is set to the length of dets.

  • When the MaxNumDetectionsSource property is set to 'Property', dets is a cell array with length determined by the MaxNumDetections property. No more than MaxNumDetections number of detections are returned. If the number of detections is fewer than MaxNumDetections, the first numDets elements of dets hold valid detections. The remaining elements of dets are set to the default value.

Data Types: double

Current sensor configuration, specified as a structure. This output can be used to determine which objects fall within the sonar beam during object execution.

FieldDescription
SensorIndex

Unique sensor index

IsValidTime

Valid detection time, returned as 0 or 1. IsValidTime is 0 when detection updates are requested at times that are between update intervals specified by UpdateInterval.

IsScanDone

IsScanDone is true when the sensor has completed a scan.

FieldOfView

Field of view of sensor determines which objects fall within the sensor beam during object execution. The field of view is defined as a 2-by-1 vector of positive real values, [azfov;elfov].

MeasurementParameters

MeasurementParameters is an array of structures containing the coordinate frame transforms needed to transform positions and velocities in the top-level frame to the current sensor frame.

Data Types: struct

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)

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stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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Create a sonar emission and then detect the emission using a sonarSensor object.

First, create a sonar emission.

orient = quaternion([180 0 0],'eulerd','zyx','frame');
sonarSig = sonarEmission('PlatformID',1,'EmitterIndex',1, ...
    'OriginPosition',[30 0 0],'Orientation',orient, ...
    'SourceLevel',140,'TargetStrength',100);

Then create a passive sonar sensor.

sensor = sonarSensor(1,'No scanning');

Detect the sonar emission.

time = 0;
[dets, numDets, config] = sensor(sonarSig,time)
dets =

  1×1 cell array

    {1×1 objectDetection}


numDets =

     1


config = 

  struct with fields:

              SensorIndex: 1
              IsValidTime: 1
               IsScanDone: 1
              FieldOfView: [1 5]
    MeasurementParameters: [1×1 struct]

More About

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Extended Capabilities

See Also

Classes

Functions

System Objects

Introduced in R2018b