A generic infrared sensor. More...

#include <IRSensor.h>

Inheritance diagram for Enki::IRSensor:

Public Member Functions
	IRSensor (Robot *owner, Vector pos, double height, double orientation, double range, double m, double x0, double c, double noiseSd=0.)
	Constructor. More...

void	init (double dt, World *w)
	Reset distance values.

void	objectStep (double dt, World w, PhysicalObject po)
	Check for all potential intersections using smartRadius of sensor and calculate and find closest distance for each ray.

void	wallsStep (double dt, World *w)
	Separated from objectStep because it is much simpler.

void	finalize (double dt, World *w)
	Applies the SensorResponseFunction to each ray and combines all rays using weights defined in the rayCombinationKernel.

double	getValue (void) const
	Return the final sensor value.

double	getDist (void) const
	Return the distance through the inverse response of the final sensor value.

double	getRayValue (unsigned i) const
	Return the value of a ray.

double	getRayDist (unsigned i) const
	Return the distance of a ray.

Point	getAbsolutePosition (void) const
	Return the absolute position of the IR sensor, updated at each time step on init()

double	getAbsoluteOrientation (void) const
	Return the absolute orientation of the IR sensor, updated at each time step on init()

unsigned	getRayCount (void) const
	Return the number of rays.

double	getAperture (void) const
	Return the aperture of the sensor.

double	getRange (void) const
	Return the range of the sensor.

double	getSmartRadius (void) const
	Return the radius for the smallest circle enclosing all rays.

Point	getAbsSmartPos (void) const
	Return current position of the center of the smartRadius, i.e. center of the smallest circle enclosing all rays in relative (robot) coordinates.

Public Member Functions inherited from Enki::LocalInteraction
	LocalInteraction ()
	Constructor.

	LocalInteraction (double range, Robot *owner)
	Constructor.

virtual	~LocalInteraction ()
	Destructor.

double	getRange () const
	Return the range of the interaction.

Protected Member Functions
void	updateRay (size_t i, double dist)
	If dist is smaller than current ray distance, update distance and response value.

double	responseFunction (double x) const
	Return the response for a given distance.

double	inverseResponseFunction (double v) const
	Return the inverse response for a given distance.

double	distanceToPolygon (double rayAngle, const Polygone &p) const
	Returns distance to PhysicalObject po for angle rayAngle. More...

Protected Attributes
Vector	absPos
	Absolute position in the world, updated on init()

double	absOrientation
	Absolute orientation in the world, updated on init()

const Vector	pos
	Relative position on the robot.

const double	height
	Height above ground, the sensor will not see any object of smaller height.

const double	orientation
	Relative orientation on the robot.

const double	range
	Actual detection range.

const double	aperture
	Aperture angle.

const double	alpha
	1/cos(aperture)

const unsigned	rayCount
	Number of rays used, each ray has an aperture of aperture/rayCount to the next one. Rays are assembled from right to left (i.e. counterclockwise)

const double	m
	Maximum possible response value, might be inside the robot if x0<0, first parameter of response function.

const double	x0
	Position of the maximum of response (might be negative, inside the robot), second parametere of response function.

const double	c
	Third parameter of response function.

const double	noiseSd
	Standard deviation of Gaussian noise in the response space.

double	smartRadius
	Radius for the smallest circle enclosing all rays.

Point	smartPos
	Current position of the center of the smartRadius, i.e. center of the smallest circle enclosing all rays in relative (robot) coordinates.

Vector	absSmartPos
	Current position of the center of the smartRadius in absolute (world) coordinates, updated on init()

std::vector< double >	rayDists
	Temporary ray values containing the lowest distance found up to now.

std::vector< double >	rayValues
	Temporary ray values containing the response value of the closest object found up to now.

std::vector< double >	rayAngles
	The angle for each ray relative to the sensor orientation in relative (robot) coordinates.

std::vector< double >	absRayAngles
	The angle for each ray relative to the sensor orientation in absolute (world) coordinates.

double	finalValue
	Final sensor value.

double	finalDist
	Final computed distance.

Protected Attributes inherited from Enki::LocalInteraction
double	r
	Radius of the local interaction.

Robot *	owner
	The physical object that owns the interaction.

Detailed Description

A generic infrared sensor.

This sensor is based on a inverse square response function and three casted rays.

During objectStep() and wallsStep() it casts the three rays, separated by an angle of 15 degrees. Distances are in cm. For negative distance values, i.e. a sensor inside an object, wall, etc., the value of the sensor response function at distance 0 will be used. If a ray fails to touch the object, the distance returned will be HUGE_VAL; the sensor response function will return a 0 sensor response for this case.

Upon finalize(), it computes finalValue and finalDist. It does so first using the following equation for each ray:

               m * (c - x0*x0)
value = F(x) = ----------------
               x*x - 2*x0*x + c

where x is the distance to the obstacle.

It then combines the three rays with this equation:

finalValue = F(d_center) + F(d_left) + F(d_right) - 2*F(d_center*alpha)

where d_R is the distance of ray R, and alpha is 1/cos(15 degrees).

Finally, it computes the final distance using:

finalDist = F-1(finalValue)

where: m F-1(v) = x0 + sqrt( (x0*x0-c) * ( 1 - — ) ) v

TODO SensorResponseFunctors translate the distances stored in the rayValues[] into actual sensor activations. An appropriate noise model (if realistic modelling is desired) should be included in the sensor response function.

Constructor & Destructor Documentation

Enki::IRSensor::IRSensor	(	Robot *	owner,
		Vector	pos,
		double	height,
		double	orientation,
		double	range,
		double	m,
		double	x0,
		double	c,
		double	noiseSd = `0.`
	)

Constructor.

Parameters

owner	robot which embeds this sensor
pos	relative position (x,y) on the robot
height	height above ground, the sensor will not see any object of smaller height
orientation	relative orientation on the robot
range	detection range, objects over this range will not be seen
m	maximum possible response value, might be inside the robot if x0<0, first parameter of response function
x0	position of the maximum of response (might be negative, inside the robot), second parametere of response function
c	third parameter of response function
noiseSd	standard deviation of Gaussian noise in the response space

References absRayAngles, Enki::Vector::angle(), aperture, finalDist, finalValue, Enki::Vector::norm(), Enki::Vector::norm2(), Enki::LocalInteraction::owner, Enki::LocalInteraction::r, range, rayAngles, rayCount, rayDists, rayValues, smartPos, and smartRadius.

Member Function Documentation

double Enki::IRSensor::distanceToPolygon	(	double	rayAngle,
		const Polygone &	p
	)		const

protected

Returns distance to PhysicalObject po for angle rayAngle.

Note: The polygon MUST be convex and have vertices oriented counterclockwise (ccw). This code does not check for and verify these conditions. Returns distance to shortest intersection point or HUGE_VAL if there is no intersection

References Enki::Segment::a, absPos, Enki::Segment::b, Enki::Vector::cross(), range, Enki::Vector::x, and Enki::Vector::y.

Referenced by getAbsSmartPos(), and objectStep().

The documentation for this class was generated from the following files:

enki/interactions/IRSensor.h
enki/interactions/IRSensor.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation