lejos.robotics.chassis

Class WheeledChassis

java.lang.Object

lejos.robotics.chassis.WheeledChassis

All Implemented Interfaces:

Chassis

public class WheeledChassis
extends java.lang.Object
implements Chassis

Represents the chassis of a wheeled robot.

The WheeledChassis provides a control system for driving a mobile robot with motorized wheels. Both differential and holonomic robots can be represented by the WheeledChassis class.

How to create a WheeledChassis object
The constructor of the DifferentialChassis class accepts an array of Wheel objects. Each of the wheel objects describes one of the motorized wheels on the chassis. A Description of a wheel consists of its diameter, its position, its motor and the gear train between wheel and motor. Wheel objects can be created using a modeler class. A modeler for traditional wheel can be obtained using the modelWheel(lejos.robotics.RegulatedMotor, double) method. A modeler for a holonomic wheel can be obtained using the modelHolonomicWheel(lejos.robotics.RegulatedMotor, double) method.

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This example creates a WheeledChassis for a differential robot.

 Wheel wheel1 = WheeledChassis.modelWheel(Motor.A, 81.6).offset(-70);
 Wheel wheel2 = WheeledChassis.modelWheel(Motor.D, 81.6).offset(70);
 Chassis chassis = new WheeledChassis(new Wheel[] { wheel1, wheel2 }, WheeledChassis.TYPE_DIFFERENTIAL);
 

This example creates a WheeledChassis for a holonomic robot.

    Wheel wheel1 = WheeledChassis.modelHolonomicWheel(Motor.A, 48).polarPosition(0, 135).gearRatio(2);
    Wheel wheel2 = WheeledChassis.modelHolonomicWheel(Motor.B, 48).polarPosition(120, 135).gearRatio(2);
    Wheel wheel3 = WheeledChassis.modelHolonomicWheel(Motor.C, 48).polarPosition(240, 135).gearRatio(2);
    Chassis chassis = new WheeledChassis(new Wheel[]{wheel1, wheel2, wheel3}, WheeledChassis.TYPE_HOLONOMIC);
 

Please note that a Chassis can have an unlimited number of motorized wheels but a differential robot needs at least two wheels and a holonomic robot needs at least three wheels.

See also the Chassis interface.

*

Author:

Aswin Bouwmeester

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	WheeledChassis.HolonomicModeler The Modeler class helps to model a wheel.
static class	WheeledChassis.Modeler The Modeler class helps to model a wheel.

Field Summary

Fields

Modifier and Type	Field and Description
protected double	angularAcceleration
protected double	angularSpeed
protected int	dummyWheels The program adds a dummy wheel to a differential chassis.
protected Matrix	forward
protected Matrix	forwardAbs
protected double	linearAcceleration
protected double	linearSpeed
protected RegulatedMotor	master
protected static int	MAXSPEED
protected RegulatedMotor[]	motor
protected lejos.robotics.chassis.WheeledChassis.Odometer	odometer
protected Matrix	reverse
protected Matrix	reverseAbs
protected static int	ROTATIONSPEED
protected Matrix	tachoAtMoveStart
protected static int	TACHOCOUNT
static int	TYPE_DIFFERENTIAL
static int	TYPE_HOLONOMIC

Constructor Summary

Constructors

Constructor and Description
WheeledChassis(Wheel[] wheels, int dim)

Method Summary

Modifier and Type	Method and Description
void	arc(double radius, double angle) Moves the chassis in an arc
protected Matrix	copyAbsolute(Matrix in) Make a copy of the source matrix, each of its element being the absolute value of the elements of the source matrix
double	getAngularAcceleration() Gets the setting for angular acceleration as is used in travel, arc, rotate and setvelocity methods
double	getAngularSpeed() Gets the setting for angular speed as is used in travel, arc, and rotate methods
double	getAngularVelocity() Returns the angular component of the current speed of the robot
protected Matrix	getAttribute(int attribute) Helper method to get some dynamic attributes from each motor
Matrix	getCurrentSpeed() Returns a matrix containing the current speed of the robot.
Move	getDisplacement(Move move) Method used by the MovePilot to update a move object that describes the move executed since the last call to startMove.
Matrix	getForward()
double	getLinearAcceleration() Gets the setting for linear acceleration as is used in travel, arc, rotate and setvelocity methods
double	getLinearDirection() Returns the current direction of the linear speed component of the robot
double	getLinearSpeed() Gets the setting for linear speed as is used in moveTo, Arc, and Rotate methods
double	getLinearVelocity() Returns the linear component of the current speed of the robot
protected double	getMax(Matrix a) Gets the biggest value from a matrix
double	getMaxAngularSpeed() Returns how fast the robot can rotate.
double	getMaxLinearSpeed() Returns the maximum speed of the robot.
double	getMinRadius() Returns the smallest possible radius this chassis is able turn
PoseProvider	getPoseProvider() Returns an Pose provider that uses odometry to keep track of the pose of the chassis
Matrix	getReverse()
boolean	isMoving() Returns true if the robot is moving.
boolean	isStalled() Returns true if at least one of the wheels is stalled
static WheeledChassis.HolonomicModeler	modelHolonomicWheel(RegulatedMotor motor, double diameter) Provides a modeler object to model a Holonomic motorized wheel on the chassis
static WheeledChassis.Modeler	modelWheel(RegulatedMotor motor, double diameter) Provides a modeler object to model a Holonomic motorized wheel on the chassis
void	moveStart() Method used by the MovePilot to tell the chassis that a new move has started.
void	rotate(double angular) Rotates the chassis for the specified number of degrees
void	setAcceleration(double linearAcceleration, double angularAcceleration) Sets the acceleration of the chassis for the moveTo and travel methods
void	setAngularAcceleration(double angularAcceleration) Sets the angular acceleration as is used in travel, arc, rotate and setvelocity methods
void	setAngularSpeed(double angularSpeed) Sets the angular speed as is used in travel, arc, and rotate methods
void	setLinearAcceleration(double linearAcceleration) Sets the linear acceleration as is used in travel, arc, rotate and setvelocity methods
void	setLinearSpeed(double linearSpeed) Sets the linear speed as is used in travel, arc, and rotate methods
protected void	setMotors(Matrix motorDelta, Matrix motorSpeed, Matrix motorAcceleration) Utility method to set distance, speed and acceleration for each motor
void	setSpeed(double linearSpeed, double angularSpeed) Sets the speed of the chassis for the moveTo method
void	setVelocity(double linearSpeed, double angularSpeed) Moves the chassis with specified speed
void	setVelocity(double linearSpeed, double direction, double angularSpeed) Moves a holonomic chassis with specified speed
void	stop() Makes the robot stop and returns immediately.
protected Matrix	toCartesianMatrix(double radius, double direction, double angular)
protected Matrix	toMatrix(double x, double y, double angular) Create a Matrix to store linear and angular components
protected Matrix	toPolar(double x, double y, double angular)
void	travel(double linear) Moves the chassis the specified distance
void	travelCartesian(double xSpeed, double ySpeed, double angularSpeed) Moves a holonomic robot with the specified speed.
void	waitComplete() Blocks while the chassis is moving, returns when all wheels have stopped (including stops caused by stalls)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

TACHOCOUNT

protected static final int TACHOCOUNT

See Also:

Constant Field Values

MAXSPEED

protected static final int MAXSPEED

See Also:

Constant Field Values

ROTATIONSPEED

protected static final int ROTATIONSPEED

See Also:

Constant Field Values

TYPE_DIFFERENTIAL

public static final int TYPE_DIFFERENTIAL

See Also:

Constant Field Values

TYPE_HOLONOMIC

public static final int TYPE_HOLONOMIC

See Also:

Constant Field Values

dummyWheels

protected final int dummyWheels

The program adds a dummy wheel to a differential chassis. This dummy wheel makes it possible to use linear algebra on three elements (x, y, angle) for the differential chassis. The y value is always zero for a differential chassis.

motor

protected final RegulatedMotor[] motor

linearSpeed

protected double linearSpeed

angularSpeed

protected double angularSpeed

linearAcceleration

protected double linearAcceleration

angularAcceleration

protected double angularAcceleration

forward

protected final Matrix forward

reverse

protected final Matrix reverse

master

protected RegulatedMotor master

tachoAtMoveStart

protected Matrix tachoAtMoveStart

forwardAbs

protected final Matrix forwardAbs

reverseAbs

protected final Matrix reverseAbs

odometer

protected lejos.robotics.chassis.WheeledChassis.Odometer odometer

Constructor Detail

WheeledChassis

public WheeledChassis(Wheel[] wheels,
                      int dim)

Method Detail

getLinearSpeed

public double getLinearSpeed()

Description copied from interface: Chassis

Gets the setting for linear speed as is used in moveTo, Arc, and Rotate methods

Specified by:

getLinearSpeed in interface Chassis

Returns:

Linear speed in robot units/second

setLinearSpeed

public void setLinearSpeed(double linearSpeed)

Description copied from interface: Chassis

Sets the linear speed as is used in travel, arc, and rotate methods

Specified by:

setLinearSpeed in interface Chassis

Parameters:

linearSpeed - Linear speed in robot units/second

getAngularSpeed

public double getAngularSpeed()

Description copied from interface: Chassis

Gets the setting for angular speed as is used in travel, arc, and rotate methods

Specified by:

getAngularSpeed in interface Chassis

Returns:

Angular speed in degrees/second.

setAngularSpeed

public void setAngularSpeed(double angularSpeed)

Description copied from interface: Chassis

Sets the angular speed as is used in travel, arc, and rotate methods

Specified by:

setAngularSpeed in interface Chassis

Parameters:

angularSpeed - Angular speed in degrees/second.

getLinearAcceleration

public double getLinearAcceleration()

Description copied from interface: Chassis

Gets the setting for linear acceleration as is used in travel, arc, rotate and setvelocity methods

Specified by:

getLinearAcceleration in interface Chassis

Returns:

Linear acceleration in robot units/second^2

setLinearAcceleration

public void setLinearAcceleration(double linearAcceleration)

Description copied from interface: Chassis

Sets the linear acceleration as is used in travel, arc, rotate and setvelocity methods

Specified by:

setLinearAcceleration in interface Chassis

Parameters:

linearAcceleration - Linear acceleration in robot units/second^2

getAngularAcceleration

public double getAngularAcceleration()

Description copied from interface: Chassis

Gets the setting for angular acceleration as is used in travel, arc, rotate and setvelocity methods

Specified by:

getAngularAcceleration in interface Chassis

Returns:

Angular acceleration in degrees/second^2.

setAngularAcceleration

public void setAngularAcceleration(double angularAcceleration)

Description copied from interface: Chassis

Sets the angular acceleration as is used in travel, arc, rotate and setvelocity methods

Specified by:

setAngularAcceleration in interface Chassis

Parameters:

angularAcceleration - Angular Acceleration in degrees/second^2.

getForward

public Matrix getForward()

getReverse

public Matrix getReverse()

setSpeed

public void setSpeed(double linearSpeed,
                     double angularSpeed)

Description copied from interface: Chassis

Sets the speed of the chassis for the moveTo method

Specified by:

setSpeed in interface Chassis

Parameters:

linearSpeed - linear component of the robot speed, expressed in the same unit as the wheel diameter.

angularSpeed - angular component of the robot speed expressed in degrees/second.

setAcceleration

public void setAcceleration(double linearAcceleration,
                            double angularAcceleration)

Description copied from interface: Chassis

Sets the acceleration of the chassis for the moveTo and travel methods

Specified by:

setAcceleration in interface Chassis

Parameters:

linearAcceleration - linear component of the robot acceleration, expressed in robot units/second^2.

angularAcceleration - angular component of the robot speed expressed acceleration, expressed in degrees/second^2.

isMoving

public boolean isMoving()

Description copied from interface: Chassis

Returns true if the robot is moving.

Specified by:

isMoving in interface Chassis

Returns:

true if the robot is moving

waitComplete

public void waitComplete()

Description copied from interface: Chassis

Blocks while the chassis is moving, returns when all wheels have stopped (including stops caused by stalls)

Specified by:

waitComplete in interface Chassis

isStalled

public boolean isStalled()

Description copied from interface: Chassis

Returns true if at least one of the wheels is stalled

Specified by:

isStalled in interface Chassis

Returns:

true if at least one of the wheels is stalled

getMinRadius

public double getMinRadius()

Description copied from interface: Chassis

Returns the smallest possible radius this chassis is able turn

Specified by:

getMinRadius in interface Chassis

Returns:

radius in robot units

stop

public void stop()

Description copied from interface: Chassis

Makes the robot stop and returns immediately.

Specified by:

stop in interface Chassis

setVelocity

public void setVelocity(double linearSpeed,
                        double angularSpeed)

Description copied from interface: Chassis

Moves the chassis with specified speed

Specified by:

setVelocity in interface Chassis

Parameters:

linearSpeed - linear component of the robot speed, expressed in the same unit as the wheel diameter.

angularSpeed - angular component of the robot speed expressed in degrees/second.

travelCartesian

public void travelCartesian(double xSpeed,
                            double ySpeed,
                            double angularSpeed)

Description copied from interface: Chassis

Moves a holonomic robot with the specified speed.
The method will throw an exception when issued on a differential chassis.

Specified by:

travelCartesian in interface Chassis

Parameters:

xSpeed - speed along the robots x-axis

ySpeed - speed along the robots y-axis

angularSpeed - angular component of the robot speed expressed in degrees/second.

setVelocity

public void setVelocity(double linearSpeed,
                        double direction,
                        double angularSpeed)

Description copied from interface: Chassis

Moves a holonomic chassis with specified speed

Specified by:

setVelocity in interface Chassis

Parameters:

linearSpeed - linear component of the robot speed, expressed in the same unit as the wheel diameter.

direction - The direction of the linear speed

angularSpeed - angular component of the robot speed expressed in degrees/second.

travel

public void travel(double linear)

Description copied from interface: Chassis

Moves the chassis the specified distance

Specified by:

travel in interface Chassis

Parameters:

linear - linear component of the robot speed, expressed in the same unit as the wheel diameter.

rotate

public void rotate(double angular)

Description copied from interface: Chassis

Rotates the chassis for the specified number of degrees

Specified by:

rotate in interface Chassis

arc

public void arc(double radius,
                double angle)

Description copied from interface: Chassis

Moves the chassis in an arc

Specified by:

arc in interface Chassis

Parameters:

radius - the radius of the arc. A positive radius means the center of the arc is on the left side of the robot, the center of a negative arc is on the right side of the robot. Infinite radius is not allowed. A radius of 0 makes the robot spin in place.

angle - The number of degrees of the arc. A positive number of degrees makes the robot go forward, a negative number makes it go backward.

setMotors

protected void setMotors(Matrix motorDelta,
                         Matrix motorSpeed,
                         Matrix motorAcceleration)

Utility method to set distance, speed and acceleration for each motor

Parameters:

motorDelta -

motorSpeed -

motorAcceleration -

getMaxLinearSpeed

public double getMaxLinearSpeed()

Description copied from interface: Chassis

Returns the maximum speed of the robot.

Specified by:

getMaxLinearSpeed in interface Chassis

Returns:

Speed in robot units

getMaxAngularSpeed

public double getMaxAngularSpeed()

Description copied from interface: Chassis

Returns how fast the robot can rotate.

Specified by:

getMaxAngularSpeed in interface Chassis

Returns:

Speed in degrees / second

getCurrentSpeed

public Matrix getCurrentSpeed()

Description copied from interface: Chassis

Returns a matrix containing the current speed of the robot.

Specified by:

getCurrentSpeed in interface Chassis

Returns:

A matrix (3x1) containing the current speed of the robot. First row contains linear speed, second row contains direction of linear speed, third row contains angular speed.

getLinearVelocity

public double getLinearVelocity()

Description copied from interface: Chassis

Returns the linear component of the current speed of the robot

Specified by:

getLinearVelocity in interface Chassis

Returns:

linear speed in robot units/second

getLinearDirection

public double getLinearDirection()

Description copied from interface: Chassis

Returns the current direction of the linear speed component of the robot

Specified by:

getLinearDirection in interface Chassis

Returns:

direction in degrees

getAngularVelocity

public double getAngularVelocity()

Description copied from interface: Chassis

Returns the angular component of the current speed of the robot

Specified by:

getAngularVelocity in interface Chassis

Returns:

Angular speed in degrees/second

moveStart

public void moveStart()

Description copied from interface: Chassis

Method used by the MovePilot to tell the chassis that a new move has started. This method is used in conjuction with the getDisplacement method.

Specified by:

moveStart in interface Chassis

getDisplacement

public Move getDisplacement(Move move)

Description copied from interface: Chassis

Method used by the MovePilot to update a move object that describes the move executed since the last call to startMove.

This method is only to be used by applications that apply just moves that meet the following conditions:

• The move must start and end with the robot being motionless
• The speed ratio between the wheels must be constant during the move

Specified by:

getDisplacement in interface Chassis

Parameters:

move - The move object to update

modelHolonomicWheel

public static WheeledChassis.HolonomicModeler modelHolonomicWheel(RegulatedMotor motor,
                                                                  double diameter)

Provides a modeler object to model a Holonomic motorized wheel on the chassis

Parameters:

motor - The regulated motor that drives the wheel

diameter - The diameter of the wheel in a unit of choice.

Returns:

the modeler

modelWheel

public static WheeledChassis.Modeler modelWheel(RegulatedMotor motor,
                                                double diameter)

Provides a modeler object to model a Holonomic motorized wheel on the chassis

Parameters:

motor - The regulated motor that drives the wheel

diameter - The diameter of the wheel in a unit of choice.

Returns:

the modeler

getPoseProvider

public PoseProvider getPoseProvider()

Description copied from interface: Chassis

Returns an Pose provider that uses odometry to keep track of the pose of the chassis

Specified by:

getPoseProvider in interface Chassis

Returns:

an Pose provider that uses odometry to keep track of the pose of the chassis

toMatrix

protected Matrix toMatrix(double x,
                          double y,
                          double angular)

Create a Matrix to store linear and angular components

Parameters:

x -

y -

angular -

Returns:

the modeler

toCartesianMatrix

protected Matrix toCartesianMatrix(double radius,
                                   double direction,
                                   double angular)

toPolar

protected Matrix toPolar(double x,
                         double y,
                         double angular)

getAttribute

protected Matrix getAttribute(int attribute)

Helper method to get some dynamic attributes from each motor

Parameters:

attribute -

Returns:

the mmatrix

getMax

protected double getMax(Matrix a)

Gets the biggest value from a matrix

Parameters:

a -

copyAbsolute

protected Matrix copyAbsolute(Matrix in)

Make a copy of the source matrix, each of its element being the absolute value of the elements of the source matrix

Parameters:

in -

Returns:

the matrix