lejos.navigation
Class Pilot

java.lang.Object
  lejos.navigation.Pilot

Direct Known Subclasses:

CompassPilot

public class Pilot
extends Object

The Pilot class is a software abstraction of the Pilot mechanism of a NXT robot. It contains methods to control robot movents: travel forward or backward in a straight line or a circular path or rotate to a new direction.
Note: this class will only work with two independently controlled Pilot motors to steer differentially, so it can rotate within its own footprint (i.e. turn on one spot).
It can be used with robots that have reversed motor design: the robot moves in the direction opposite to the the dirction of motor rotation. Uses the Motor class, which regulates motor speed using the NXT motor's built in tachometer.
Some methods optionally return immediately so the thread that called the method can monitor sensors and call stop() if necessary.
Uses the smoothAcceleration property of Motors to improve motor symchronication Example:

        Pilot pilot = new Pilot(2.1f,4.4f,Motor.A, Motor.C,true);
   pilot.setSpeed(720);// 2 RPM
        pilot.travel(12);
        pilot.rotate(-90);
        pilot.travel(-12,true);
        while(pilot.isMoving())Thread.yield();
        pilot.rotate(-90);
        pilot.rotateTo(270);
        pilot.steer(-50,180,true);
        while(pilot.isMoving())Thread.yield();
        pilot.steer(100);
        try{Thread.sleep(1000);}
   catch(InterruptedException e){}
        pilot.stop();
 

Field Summary

float	_degPerDistance motor degrees per unit of travel
protected Motor	_left left motor
protected Motor	_right right motor
protected int	_speed motor speed degrees per second.
float	_trackWidth distance between wheels - used in steer()
float	_wheelDiameter diameter of tires

Constructor Summary

Pilot(float wheelDiameter, float trackWidth, Motor leftMotor, Motor rightMotor)
Allocates a Pilot object, and sets the physical parameters of the NXT robot.

Pilot(float wheelDiameter, float trackWidth, Motor leftMotor, Motor rightMotor, boolean reverse)
Allocates a Pilot object, and sets the physical parameters of the NXT robot.

Method Summary

void	backward() Moves the NXT robot backward until stop() is called.
void	forward() Moves the NXT robot forward until stop() is called.
int	getAngle() returns the angle of rotation of the robot since last call to reset of tacho count;
Motor	getLeft() returns left motor
int	getLeftActualSpeed() returns actual speed of left motor in degrees per second; a negative value if motor is rotating backwards Updated avery 100 ms.
int	getLeftCount() returns tachoCount of left motor; Positive value means motor has moved the robot forward;
Motor	getRight() returns right motor
int	getRightActualSpeed() returns actual speed of right motor in deg/sec; a negative value if motor is rotating backwards.
int	getRightCount() returns tachoCount of the right motor; Positive value means motor has moved the robot forward;
int	getSpeed() return current speed setting
float	getTravelDistance() returns distance taveled since last reset of tacho count
float	getTurnRatio() return ratatio of Motor revolutions per 360 degree rotation of the robot
boolean	isMoving() returns true iff the NXT robot is moving
void	regulateSpeed(boolean yes) Sets motor speed regulation on = true (default) or off = false; Allows steer() method to be called by (for example) a line tracker or compass navigator so direction control is from sensor inputs
void	resetTachoCount() resets tacho count for both motors
void	rotate(int angle) Rotates the NXT robot through a specific angle; Rotates left if angle is positive, right if negative, Returns when angle is reached.
void	rotate(int angle, boolean immediateReturn) Rotates the NXT robot through a specific angle; Rotates left if angle is positive, right if negative; Returns immediately iff immediateReturn is true.
void	setSpeed(int speed) Sets speed of both motors, degrees/sec; also sets retulate speed true
void	steer(int turnRate) Moves the NXT robot in a circular path at a specific turn rate.
void	steer(int turnRate, int angle) Moves the NXT robot in a circular path through a specific angle; Negative turnRate means center of turning circle is on right side of the robot; Range of turnRate values : -200 : 200 ; Robot will stop when total rotation equals angle.
void	steer(int turnRate, int angle, boolean immediateReturn) Moves the NXT robot in a circular path, and stops when the direction it is facing has changed by a specific angle; Returns immediately if immediateReturn is true.
void	stop() Stops the NXT robot
void	travel(float distance) Moves the NXT robot a specific distance; A positive distance causes forward motion; negative distance moves backward.
void	travel(float distance, boolean immediateReturn) Moves the NXT robot a specific distance; if immediateReturn is true, method returns immediately.

Methods inherited from class java.lang.Object

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

Field Detail

_left

protected Motor _left

left motor

_right

protected Motor _right

right motor

_degPerDistance

public final float _degPerDistance

motor degrees per unit of travel

_speed

protected int _speed

motor speed degrees per second. Used by all methods that cause movememt

_trackWidth

public final float _trackWidth

distance between wheels - used in steer()

_wheelDiameter

public final float _wheelDiameter

diameter of tires

Constructor Detail

Pilot

public Pilot(float wheelDiameter,
             float trackWidth,
             Motor leftMotor,
             Motor rightMotor)

Allocates a Pilot object, and sets the physical parameters of the NXT robot.
Assumes Motor.forward() causes the robot to move forward);

Parameters:

wheelDiameter - Diameter of the tire, in any convenient units. (The diameter in mm is usually printed on the tire).

trackWidth - Distance between center of right tire and center of left tire, in same units as wheelDiameter

Pilot

public Pilot(float wheelDiameter,
             float trackWidth,
             Motor leftMotor,
             Motor rightMotor,
             boolean reverse)

Allocates a Pilot object, and sets the physical parameters of the NXT robot.

Parameters:

wheelDiameter - Diameter of the tire, in any convenient units. (The diameter in mm is usually printed on the tire).

trackWidth - Distance between center of right tire and center of left tire, in the same units as wheelDiameter

reverse - if true, the NXT robot moves forward when the motors are running backward.

Method Detail

getLeft

public Motor getLeft()

returns left motor

Returns:

left motor

getRight

public Motor getRight()

returns right motor

Returns:

right motor

getLeftCount

public int getLeftCount()

returns tachoCount of left motor; Positive value means motor has moved the robot forward;

getRightCount

public int getRightCount()

returns tachoCount of the right motor; Positive value means motor has moved the robot forward;

getLeftActualSpeed

public int getLeftActualSpeed()

returns actual speed of left motor in degrees per second; a negative value if motor is rotating backwards
Updated avery 100 ms.

getRightActualSpeed

public int getRightActualSpeed()

returns actual speed of right motor in deg/sec; a negative value if motor is rotating backwards.
Updated avery 100 ms.

getTurnRatio

public float getTurnRatio()

return ratatio of Motor revolutions per 360 degree rotation of the robot

getSpeed

public int getSpeed()

return current speed setting

Returns:

current speed

setSpeed

public void setSpeed(int speed)

Sets speed of both motors, degrees/sec; also sets retulate speed true

forward

public void forward()

Moves the NXT robot forward until stop() is called.

backward

public void backward()

Moves the NXT robot backward until stop() is called.

rotate

public void rotate(int angle)

Rotates the NXT robot through a specific angle; Rotates left if angle is positive, right if negative, Returns when angle is reached. Wheels turn in opposite directions producing a zero radius turn.

Parameters:

angle - degrees. Positive angle rotates to the left (clockwise); negative to the right.
Requires correct values for wheel diameter and track width.

rotate

public void rotate(int angle,
                   boolean immediateReturn)

Rotates the NXT robot through a specific angle; Rotates left if angle is positive, right if negative; Returns immediately iff immediateReturn is true. Wheels turn in opposite directions producing a zero radius turn.

Parameters:

angle - degrees. Positive angle rotates to the left; negative to the right.
Requires correct values for wheel diameter and track width.

immediateReturn - if true this method returns immediately

getAngle

public int getAngle()

returns the angle of rotation of the robot since last call to reset of tacho count;

stop

public void stop()

Stops the NXT robot

isMoving

public boolean isMoving()

returns true iff the NXT robot is moving

resetTachoCount

public void resetTachoCount()

resets tacho count for both motors

getTravelDistance

public float getTravelDistance()

returns distance taveled since last reset of tacho count

travel

public void travel(float distance)

Moves the NXT robot a specific distance;
A positive distance causes forward motion; negative distance moves backward.

Parameters:

distance - of robot movement. Unit of measure for distance must be same as wheelDiameter and trackWidth

travel

public void travel(float distance,
                   boolean immediateReturn)

Moves the NXT robot a specific distance; if immediateReturn is true, method returns immediately.
A positive distance causes forward motion; negative distance moves backward.

Parameters:

immediateReturn - If true, method returns immediately, and robot stops after traveling the distance. If false, method returns immediately.

steer

public void steer(int turnRate)

Moves the NXT robot in a circular path at a specific turn rate.
The center of the turning circle is on the right side of the robot iff parameter turnRate is negative;
turnRate values are between -200 and +200;

Parameters:

turnRate - If positive, the left wheel is on the inside of the turn. If negative, the left wheel is on the outside. This parameter determines the ratio of inner wheel speed to outer wheel speed (as a percent).
Formula: ratio = 100 - abs(turnRate). When the ratio is negative, the outer and inner wheels rotate in opposite directions.
Examples:

• steer(25)-> inner wheel turns at 75% of the speed of the outer wheel
  
• steer(100) -> inner wheel stops.
  
• steer(200) -> means that the inner wheel turns at the same speed as the outer wheel - a zero radius turn.
  

steer

public void steer(int turnRate,
                  int angle)

Moves the NXT robot in a circular path through a specific angle;
Negative turnRate means center of turning circle is on right side of the robot;
Range of turnRate values : -200 : 200 ; Robot will stop when total rotation equals angle. If angle is negative, robot will move travel backwards.

Parameters:

turnRate - If positive, the left wheel is on the inside of the turn. If negative, the left wheel is on the outside. This parameter determines the ratio of inner wheel speed to outer wheel speed (as a percent).

angle - the angle through which the robot will rotate and then stop. If negative, robot traces the turning circle backwards.

steer

public void steer(int turnRate,
                  int angle,
                  boolean immediateReturn)

Moves the NXT robot in a circular path, and stops when the direction it is facing has changed by a specific angle;
Returns immediately if immediateReturn is true. The robot will stop automatically when the turm is complete. The center of the turning circle is on right side of the robot iff parameter turnRate is negative
turnRate values are between -200 and +200;

Parameters:

turnRate - If positive, the left wheel is on the inside of the turn. If negative, the left wheel is on the outside. This parameter determines the ratio of inner wheel speed to outer wheel speed (as a percent).

angle - the angle through which the robot will rotate and then stop. If negative, robot traces the turning circle backwards.

immediateReturn - iff true, method returns immedediately.

regulateSpeed

public void regulateSpeed(boolean yes)

Sets motor speed regulation on = true (default) or off = false;
Allows steer() method to be called by (for example) a line tracker or compass navigator so direction control is from sensor inputs