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insSensor

Inertial navigation system and GNSS/GPS simulation model

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Description

TheinsSensorSystem object™ models a device that fuses measurements from an inertial navigation system (INS) and global navigation satellite system (GNSS) such as a GPS, and outputs the fused measurements.

To output fused INS and GNSS measurements:

  1. Create theinsSensorobject and set its properties.

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

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

Creation

Syntax

INS = insSensor
INS = insSensor(Name,Value)

Description

example

INS= insSensorreturns a System object,INS, that models a device that outputs measurements from an INS and GNSS.

example

INS= insSensor(Name,Value)setspropertiesusing one or more name-value pairs. Unspecified properties have default values. Enclose each property name in quotes.

Properties

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

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

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

Location of the sensor on the platform, in meters, specified as a three-element real-valued vector of the form [xyz]. The vector defines the offset of the sensor origin from the origin of the platform.

Tunable:Yes

Data Types:single|double

Accuracy of the roll measurement of the sensor body, in degrees, specified as a nonnegative real scalar.

Rollis the rotation around thex-axis of the sensor body. Roll noise is modeled as a white noise process.RollAccuracysets the standard deviation of the roll measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the pitch measurement of the sensor body, in degrees, specified as a nonnegative real scalar.

Pitchis the rotation around they-axis of the sensor body. Pitch noise is modeled as a white noise process.PitchAccuracydefines the standard deviation of the pitch measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the yaw measurement of the sensor body, in degrees, specified as a nonnegative real scalar.

Yawis the rotation around thez-axis of the sensor body. Yaw noise is modeled as a white noise process.YawAccuracydefines the standard deviation of the yaw measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the position measurement of the sensor body, in meters, specified as a nonnegative real scalar or a three-element real-valued vector. The elements of the vector set the accuracy of thex-,y-, andz-position measurements, respectively. If you specifyPositionAccuracyas a scalar value, then the object sets the accuracy of all three positions to this value.

Position noise is modeled as a white noise process.PositionAccuracydefines the standard deviation of the position measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the velocity measurement of the sensor body, in meters per second, specified as a nonnegative real scalar.

Velocity noise is modeled as a white noise process.VelocityAccuracydefines the standard deviation of the velocity measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the acceleration measurement of the sensor body, in meters per second, specified as a nonnegative real scalar.

Acceleration noise is modeled as a white noise process.AccelerationAccuracydefines the standard deviation of the acceleration measurement noise.

Tunable:Yes

Data Types:single|double

Accuracy of the angular velocity measurement of the sensor body, in meters per second, specified as a nonnegative real scalar.

Angular velocity is modeled as a white noise process.AngularVelocityAccuracydefines the standard deviation of the acceleration measurement noise.

Tunable:Yes

Data Types:single|double

Enable input of simulation time, specified as a logical0(false) or1(true). Set this property totrueto input the simulation time by using thesimTimeargument.

Tunable:No

Data Types:logical

Enable GNSS fix, specified as a logical1(true) or0(false). Set this property tofalseto simulate the loss of a GNSS receiver fix. When a GNSS receiver fix is lost, position measurements drift at a rate specified by thePositionErrorFactorproperty.

Tunable:Yes

Dependencies

To enable this property, setTimeInputtotrue.

Data Types:logical

Position error factor without GNSS fix, specified as a scalar or a 1-by-3 vector of scalars.

When theHasGNSSFixproperty is set tofalse, the position error grows at a quadratic rate due to constant bias in the accelerometer. The position error for a position componentE(t) can be expressed asE(t) = 1/2αt2, whereαis the position error factor for the corresponding component andtis the time since the GNSS fix is lost. While running, the object computestbased on thesimTimeinput. The computedE(t) values for thex,y, andzcomponents are added to the corresponding position components of thegTruthinput.

Tunable:Yes

Dependencies

To enable this property, setTimeInputtotrueandHasGNSSFixtofalse.

Data Types:single|double

Random number source, specified as one of these options:

  • 'Global stream'–– Generate random numbers using the current global random number stream.

  • 'mt19937ar with seed'–– Generate random numbers using the mt19937ar algorithm, with the seed specified by theSeedproperty.

Data Types:char|string

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

Dependencies

To enable this property, setRandomStreamto'mt19937ar with seed'.

Data Types:single|double|int8|int16|int32|int64|uint8|uint16|uint32|uint64

Usage

Syntax

measurement = INS(gTruth)
measurement = INS(gTruth,simTime)

Description

example

measurement= INS(gTruth)models the data received from an INS sensor reading and GNSS sensor reading. The output measurement is based on the inertial ground-truth state of the sensor body,gTruth.

measurement= INS(gTruth,simTime)additionally specifies the time of simulation,simTime. To enable this syntax, set theTimeInputproperty totrue.

Input Arguments

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Inertial ground-truth state of sensor body, in local Cartesian coordinates, specified as a structure containing these fields:

Field Description
'Position'

Position, in meters, specified as a real, finiteN-by-3 matrix of [xyz] vectors.Nis the number of samples in the current frame.
'Velocity'

Velocity (v), in meters per second, specified as a real, finiteN-by-3 matrix of [vxvyvz] vector.Nis the number of samples in the current frame.
'Orientation'

Orientation with respect to the local Cartesian coordinate system, specified as one of these options:

  • N-element column vector ofquaternionobjects

  • 3-by-3-by-Narray of rotation matrices

  • N-by-3 matrix of [xrollypitchzyaw] angles in degrees

Each quaternion or rotation matrix is a frame rotation from the local Cartesian coordinate system to the current sensor body coordinate system.Nis the number of samples in the current frame.
'Acceleration'

Acceleration (a), in meters per second squared, specified as a real, finiteN-by-3 matrix of [axayaz] vectors.Nis the number of samples in the current frame.
'AngularVelocity'

Angular velocity (ω), in degrees per second squared, specified as a real, finiteN-by-3 matrix of [ωxωyωz] vectors.Nis the number of samples in the current frame.

The field values must be of typedoubleorsingle.

ThePosition,Velocity, andOrientationfields are required. The other fields are optional.

Example:struct('Position',[0 0 0],'Velocity',[0 0 0],'Orientation',quaternion([1 0 0 0]))

Simulation time, in seconds, specified as a nonnegative real scalar.

Data Types:single|double

Output Arguments

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Measurement of the sensor body motion, in local Cartesian coordinates, returned as a structure containing these fields:

Field Description
'Position'

Position, in meters, specified as a real, finiteN-by-3 matrix of [xyz] vectors.Nis the number of samples in the current frame.
'Velocity'

Velocity (v), in meters per second, specified as a real, finiteN-by-3 matrix of [vxvyvz] vector.Nis the number of samples in the current frame.
'Orientation'

Orientation with respect to the local Cartesian coordinate system, specified as one of these options:

  • N-element column vector ofquaternionobjects

  • 3-by-3-by-Narray of rotation matrices

  • N-by-3 matrix of [xrollypitchzyaw] angles in degrees

Each quaternion or rotation matrix is a frame rotation from the local Cartesian coordinate system to the current sensor body coordinate system.Nis the number of samples in the current frame.
'Acceleration'

Acceleration (a), in meters per second squared, specified as a real, finiteN-by-3 matrix of [axayaz] vectors.Nis the number of samples in the current frame.
'AngularVelocity'

Angular velocity (ω), in degrees per second squared, specified as a real, finiteN-by-3 matrix of [ωxωyωz] vectors.Nis the number of samples in the current frame.

The returned field values are of typedoubleorsingleand are of the same type as the corresponding field values in thegTruthinput.

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 namedobj, use this syntax:

release(obj)

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perturbations Perturbation defined on object
perturb Apply perturbations to object
step RunSystem objectalgorithm
clone Create duplicateSystem object
isLocked Determine ifSystem objectis in use
reset Reset internal states ofSystem object
release Release resources and allow changes toSystem objectproperty values and input characteristics

Examples

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Open Live Script

Create a motion structure that defines a stationary position at the local north-east-down (NED) origin. Because the platform is stationary, you need to define only a single sample. Assume the ground-truth motion is sampled for 10 seconds with a 100 Hz sample rate. Create a defaultinsSensorSystem object™. Preallocate variables to hold output from theinsSensorobject.

Fs = 100; duration = 10; numSamples = Fs*duration; motion = struct(...'Position',zeros(1,3),...'Velocity',zeros(1,3),...'Orientation',ones(1,1,'quaternion')); INS = insSensor; positionMeasurements = zeros(numSamples,3); velocityMeasurements = zeros(numSamples,3); orientationMeasurements = zeros(numSamples,1,'quaternion');

In a loop, callINS运动与静止的结构返回position, velocity, and orientation measurements in the local NED coordinate system. Log the position, velocity, and orientation measurements.

fori = 1:numSamples measurements = INS(motion); positionMeasurements(i,:) = measurements.Position; velocityMeasurements(i,:) = measurements.Velocity; orientationMeasurements(i) = measurements.Orientation;end

Convert the orientation from quaternions to Euler angles for visualization purposes. Plot the position, velocity, and orientation measurements over time.

orientationMeasurements = eulerd(orientationMeasurements,'ZYX','frame');t = (0:(numSamples-1))/Fs; subplot(3,1,1) plot(t,positionMeasurements) title('Position') xlabel('Time (s)') ylabel('Position (m)') legend('North','East','Down'次要情节(3、1、2)情节titl (t, velocityMeasurements)e('Velocity') xlabel('Time (s)') ylabel('Velocity (m/s)') legend('North','East','Down') subplot(3,1,3) plot(t,orientationMeasurements) title('Orientation') xlabel('Time (s)') ylabel('Rotation (degrees)') legend('Roll','Pitch','Yaw')

Figure contains 3 axes objects. Axes object 1 with title Position contains 3 objects of type line. These objects represent North, East, Down. Axes object 2 with title Velocity contains 3 objects of type line. These objects represent North, East, Down. Axes object 3 with title Orientation contains 3 objects of type line. These objects represent Roll, Pitch, Yaw.

Open Live Script

Generate INS measurements using theinsSensorSystem object™. UsewaypointTrajectoryto generate the ground-truth path.

Specify a ground-truth orientation that begins with the sensor bodyx-axis aligned with North and ends with the sensor bodyx-axis aligned with East. Specify waypoints for an arc trajectory and a time-of-arrival vector for the corresponding waypoints. Use a 100 Hz sample rate. Create awaypointTrajectorySystem object with the waypoint constraints, and setSamplesPerFrameso that the entire trajectory is output with one call.

eulerAngles = [0,0,0;...0,0,0;...90,0,0;...90,0,0]; orientation = quaternion(eulerAngles,'eulerd','ZYX','frame');r = 20; waypoints = [0,0,0;...100,0,0;...100+r,r,0;...100+r,100+r,0]; toa = [0,10,10+(2*pi*r/4),20+(2*pi*r/4)]; Fs = 100; numSamples = floor(Fs*toa(end)); path = waypointTrajectory('Waypoints',waypoints,...'TimeOfArrival',toa,...'Orientation',orientation,...'SampleRate',Fs,...'SamplesPerFrame',numSamples);

Create aninsSensorSystem object to model receiving INS data. Set thePositionAccuracyto0.1.

ins = insSensor('PositionAccuracy',0.1);

Call the waypoint trajectory object,path, to generate the ground-truth motion. Call the INS simulator,ins, with the ground-truth motion to generate INS measurements.

[motion.Position,motion.Orientation,motion.Velocity] = path(); insMeas = ins(motion);

Convert the orientation returned byinsto Euler angles in degrees for visualization purposes. Plot the full path and orientation over time.

orientationMeasurementEuler = eulerd(insMeas.Orientation,'ZYX','frame');次要情节(2,1,1)情节(insMeas.Position (: 1), insMeas.Position(:,2)); title('Path') xlabel('North (m)') ylabel('East (m)') subplot(2,1,2) t = (0:(numSamples-1)).'/Fs; plot(t,orientationMeasurementEuler(:,1),...t,orientationMeasurementEuler(:,2),...t,orientationMeasurementEuler(:,3)); title('Orientation') legend('Yaw','Pitch','Roll') xlabel('Time (s)') ylabel('Rotation (degrees)')

Figure contains 2 axes objects. Axes object 1 with title Path contains an object of type line. Axes object 2 with title Orientation contains 3 objects of type line. These objects represent Yaw, Pitch, Roll.

Extended Capabilities

Version History

Introduced in R2022a

See Also

Objects