HELICOPTER OBSTACLE PROXIMITY SENSOR SYSTEM

THE PROPOSED EFFORT IS TO ANALYZE, DESIGN, AND CONSTRUCT AN OPTICAL RANGE SYSTEM TO BE USED TO SENSE THE PRESENCE OF ANY OBSTACLE WITHIN A 200 FOOT RADIUS OF THE HELICOPTER. WHILE LASER RANGERS HAVE BEEN USED BY THE INDUSTRIAL AND MILITARY COMMUNITITES FOR MANY YEARS, THESE DESIGNS ARE FOR APPLICATIONS DIFFERENT FROM OBSTACLE AVOIDANCE AND THEREFORE MORE COMPLEX AND EXPENSIVE. THE PROPOSED DESIGN USES A GAAS LASER DIODE OPERATING WITH A VERY SHORT PULSE AT A PULSE RATE SUCH THAT RANGE MEASUREMENTS ARE MADE EVERY 3.5 INCHES ON A 400 FOOT DIAMETER CIRCLE ABOUT THE HELICOPTER. THE HORIZONAL SCANNING IS ACCOMPLISHED BY A SIMPLE ROTATING PRISM WITH A SHAFT ENCODER PROVIDING THE AZIMUTHAL ANGLE. THE SENSOR WOULD PROVIDE A COMPLETE NEW PLAN POSITION INDICATOR (PPI) DISPLAY 5 TIMES A SECOND. THE VERY NARROW BEAM AND NARROW PULSE WIDTH WILL PROVIDE GOOD OBSTACLE DEFINITION. THE PROPOSED SYSTEM USES A SIMPLE ANALOG TECHNIQUE FOR MEASURING RANGE WHICH YIELDS HIGH ACCURACY AND ELIMINATES THE MORE COMPLEX, HIGH POWER CONSUMPTION, ULTRA HIGH FREQUENCY DIGITAL COUNTER. THE USE OF AN OPTICAL FIBER DELAY LINE PERMITS THE SYSTEM TO MEASURE THE ZERO RANGE AND ELIMINATES THE TRANSMITTERS MAIN BANG INTERFERENCE WITH THE SENSITIVE OPTICAL RECEIVER.