Northrop Grumman Systems Corporation

Carl L Bose

Dennis C Richman

Rolf Krumes

Edward J Knobbe

A system for sensing objects in the flight path of an aircraft and alerting the pilot to their presence includes a laser radar subsystem for emitting a beam of laser energy, receiving returns from objects, and processing the returns to produce range data related to the range of the objects from the aircraft. A scanning subsystem scans the beam and produces directional information related to the instantaneous direction of the beam relative to the aircraft. Processor circuitry controls operation, processes the range data and directional information with instrumentation data from the avionics system, produces video information related to the range, direction, and type of the objects, and interfaces the video information to the video display system. The processor circuitry may be programmed to (1) overlay video information on existing aircraft video display system, (2) provide acoustical warnings on an aircraft intercom, (3) analyze returns by subdividing the field of regard into a series of analysis windows, performing a statistical analysis of the returns related to each of the analysis windows, and identifying returns that fall into a common range interval, (4) transforming coordinates of objects measured relative to the aircraft to a horizon-stabilized, north-oriented coordinate system which is independent of the attitude of the aircraft, (5) inserting the coordinates of identified objects into a data base so that the coordinates may be used for constructing a video display at a later time and updating the data base to correct for movements of the aircraft, and (6) constructing a window-of-safety display of objects currently within the field of regard by adjusting the displayed position of the objects to compensate for avoidance maneuvers the pilot may execute.

Obstacle avoidance system for helicopters and other aircraft

A strapped down astro-inertial navigator includes a roll outer gimbal, a pitch inner gimbal and a platform coupled to the inner gimbal. An instrument cluster which includes X-axis, Y-axis and Z-axis ring laser gyros (RLGs) and associated accelerometers is mounted to the platform. Also hard mounted to the platform is a stellar sensor which includes a telescope and a solid state focal plane array which views stellar reference objects. In an astro-inertial mode of operation one or more stellar objects are tracked for a period of time. The roll and the pitch gimbals are employed to point the telescope and, periodically, to observe and average out the effects of star sensor and horizontal accelerometer errors. The star sensor error observability is accomplished by periodically rotating the inner and outer gimbals through 180.degree. and the stellar objects once again tracked. Due to the 180.degree. rotation boresight errors within the stellar tracker are observed and compensated for. The 180.degree. rotation also serves to reorient the accelerometer input axes by 180.degree., thereby also beneficially causing accelerometer errors to average out. In a free inertial mode of operation the inner and outer gimbals are both continuously rotated through plus and minus 360.degree. but at different rotational rates to provide 3 axis error averaging of both gyro and accelerometer errors.

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Rancho Palos Verdes, CA, United States of America

Carl L Bose