Satellite based collision avoidance system

Details Satellite based collision avoidance system Satellite based collision avoidance system

1994-08-16

2001-11-06

Teska, Kevin J. (Department: 2123)

Data processing: vehicles, navigation, and relative location

Navigation

Determination of travel data based on the start point and...

C701S213000, C342S357490, C342S451000, C455S456500, C340S961000

Reexamination Certificate

active

06314366

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to an automatic collision avoidance control and alert system for tracking and directing aircraft and other vehicles for collision avoidance. More specifically, the invention is an improved collision avoidance system for use in automatically alerting a pilot of a collision threat and coordinating an evasive maneuver between aircraft. The expected advantages of such a system is improved collision avoidance, elimination of false collision alarms and an increased target tracking capacity. The present invention is directed to such an automatic vehicular-based system for automatically providing collision avoidance.
Since the advent of aviation it has been desirable to avoid aircraft collisions and near misses. Traditionally, pilots have used a wholly manual method, i.e. visually identifying other aircraft and flying to avoid a collision. Such a system is susceptible to human error and is wholly unworkable in low visibility conditions or within crowded airspace.
The use of a ground based air traffic control (ATC) system, two-way voice radio communications and RADAR greatly enhance the identification and control of aircraft to avoid collisions. Two-way voice radio communication allows aircraft to communicate with one another and the ATC operator to avoid potential conflicts. RADAR, both on-board aircraft and at ground based ATC facilities provides an operator intensive technique for avoiding aircraft collisions. In the present ATC system the ATC operator coordinates the location, altitude, and track of all aircraft within her assigned control area by communicating with the aircraft over two-way voice radio. Present ATC systems consist of a network of airport terminal area and enroute surveillance radar systems. These systems consist of both primary and secondary RADAR systems and computers that display usable data for the control of air traffic in the national and international airspace systems.
The basic ATC RADAR system consists of Primary RADAR and secondary RADAR. Primary RADAR operates by transmitting a high power, highly directional radio pulse at a known azimuth (direction, in degrees from North) from a rotating antenna and measures the time it takes to receive the reflected signal from an object (aircraft) in space back to the point of transmission. This time factor determines the range in nautical miles from the radar site to the target. The direction of the target is determined by the antenna azimuth from which the signal is received. The limitations of using only this system result in the loss of targets because of the difficulty in detecting weak reflected RADAR return signals attenuated by atmospheric conditions and the difficulty in operating a synchronized height finding radar.
Secondary RADAR known as the Air Traffic Control Radar Beacon System (ATCRBS) utilizes cooperative equipment (a radio receiver/transmitter or transponder) located in the target aircraft to replace the conventional radar's passive reflected return signal with an active reply signal. Like a conventional high power radar, ground based secondary radar transmits a highly directional pulse from a rotating antenna that is usually synchronized with the primary radar antenna. The secondary radar pulse is called the interrogating signal. The interrogating signal requires much less power than conventional radar because secondary radar relies on an active return signal from the target aircraft. In response to receiving the interrogating signal the cooperative aircraft transponder automatically transmits a distinctive reply signal back to the secondary radar's antenna. The secondary radar measures the time between the interrogating signal transmission and the transponder reply signal and, like the reflected return in primary radar, uses this time delay to determine the range of the target aircraft. The direction of the target aircraft is determined by the antenna azimuth from which the reply signal is received. The secondary radar's cooperative transponder improves on the conventional radar's passive reflective return by encoding additional information in the transponder reply signal. The additional information includes an aircraft identification number and the aircraft pressure altitude. For example, Delta flight 195 to Dallas (Dall
95
) is requested by ground based ATC to squawk “4142”. In response, the aircraft pilot manually dials in “41420” at the aircraft transponder control panel. The transponder control logic can now encode the assigned four digit identification, e.g. “4142”, on the transponder reply signal. The aircraft's transponder can also be connected to the aircraft's pressure altimeter to enable the transponder control logic to encode the aircraft pressure altitude on the transponder reply signal. The aircraft transponder reply signal containing the encoded aircraft identification and pressure altitude is processed by ground based computers for display on the ATC operator's radar screen. The ATC operators usually provide specific flight instructions to aircraft to avoid flight conflicts and warn aircraft of other nearby aircraft. In large aircraft, active on-board conventional nose RADAR may also identify aircraft that are in front of the large aircraft.
RADAR, however, has a number of disadvantages. Radar systems, even secondary radar, provides limited range and accuracy in the determination of the location and altitude of an aircraft. The range of radar is inherently limited due to obstacles in the line of sight of the radar, curvature of the earth, atmospheric conditions, etc., and is subject to provide false readings or ghosts. RADAR may also fail to provide sufficient target resolution at the critical near collision phase where target aircraft are close together. Radar coverage is not available in many areas of the world, and is not available at all altitudes in the United States.
The presently used and Federal Aviation Administration (FAA) approved aircraft collision avoidance system is known as the Traffic Alert and Collision Avoidance System (TCAS). The TCAS is an airborne traffic alert and collision avoidance advisory system that operates without support from ATC ground stations. TCAS detects the presence of nearby intruder aircraft equipped with transponders that reply to secondary radar interrogating signals. TCAS tracks and continuously evaluates the threat potential of these aircraft in relation to one's own aircraft, displays the nearby transponder-equipped aircraft on a traffic advisory display, and during threat situations provides traffic advisory alerts and vertical maneuvering resolution advisories (RA) to assist the pilot in avoiding mid-air collisions. A TCAS has a transmitter, a transmit antenna, a transponder, one or two directional receiver antennae, a control interface, display unit(s), and a signal/control processor.
A TCAS determines the location of other aircraft by using the cooperative secondary radar transponders located in other aircraft. A TCAS transmitter asynchronously polls for other aircraft with an active L-band interrogating signal, i.e. at the same frequency as the ground based secondary radar interrogating signal. The TCAS interrogating signal, however, is an omni-directional signal whereas the ground based secondary radar signal is highly directional. When a target aircraft's cooperative transponder receives a TCAS interrogating signal the transponder transmits a reply signal. By using RADAR timing principals, the interrogating TCAS can measure the time between the interrogating signal transmission and transponder reply to determine the approximate range of the intruder aircraft. By using direction finding antenna techniques, the interrogating TICAS determines the relative direction of the transponder reply signal with a fixed directional antenna array and the TCAS signal processor. The TCAS omni-directional interrogating signal causes all secondary radar cooperative transponders within receiving range to reply, therefore, the TCAS signal processor

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