Package lejos.robotics

Class LightScanner

  • public class LightScanner
extends java.lang.Object
    Software abstraction of a light sensor rotating in a horizontal plane, driven by a motor. Records the raw light value and bearing of beacons seen during a scan, This class assumes that the motor tacho count corresponds to the angle of the sensor in the navigational plane.
    After a forward scan is complete, the scan is repeated in the reverse direction and the data are averaged. This averages out the gear backlash error. The results of a scan are returned as a set of RangeReadings, not a good name but this class does have enough fields to do the job. If used in MCL however, a different class name should be used because the algorithm for calculation of particle weights is very different if the basic is angles rather than ranges.
    Author:
    Roger Glassey

    • Constructor Summary

      Constructors 
      Constructor Description
      LightScanner​(RegulatedMotor headMotor, LightDetector lightDetector, int minBeaconLight, int background)
      Specify the hardware for this object.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      RegulatedMotor getMotor()  
      void halt()  
      RangeReadings scanLight​(float startAngle, float endAngle, int direction, int numReadings)
      Perform a scan for a number of light beacons within the arc defined by the start and end angles in the specified direction.
      void setSpeed​(int speed)  

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • LightScanner

        public LightScanner​(RegulatedMotor headMotor,
                    LightDetector lightDetector,
                    int minBeaconLight,
                    int background)
        Specify the hardware for this object. Light values less than background are ignored. When a light value larger than minBeaconLight is sensed, it is within the field of view of the light sensor. As scanning continues, when the light value drops below background, it is assumed that the beacon has been passed, and the angle at which the maximum occurred is the angle of the beacon.
        Parameters:
        headMotor -
        lightDetector -
        minBeaconLight -
        background -

    • Method Detail

      • setSpeed

        public void setSpeed​(int speed)

      • halt

        public void halt()

      • scanLight

        public RangeReadings scanLight​(float startAngle,
                               float endAngle,
                               int direction,
                               int numReadings)
        Perform a scan for a number of light beacons within the arc defined by the start and end angles in the specified direction. Scan in both directions and use the average of the angles. Assumes the scanner hardware is built so that increasing tacho count of the motor corresponds to increasing angle in the navigation plane.
        Parameters:
        startAngle - of the arc
        endAngle - of the arc
        direction - of the scan. +1 = increasing tacho count of motor.
        numReadings -
        Returns:
        the set of range readings, containing the light intensity and angle of each beacon