Patent Application
20120200433
Ground operations at night, in low-visibility conditions, or at uncontrolled airports (i.e., those without an active traffic control facility) are particularly risky. Unlike during airborne operations, or during take-off and landing operations on a runway, aircraft normally taxi in close proximity to other aircraft and surface vehicles, so that the type of collision avoidance algorithms that are used for Traffic Collision Avoidance System (TCAS) or for runway collision alerting are not suited to surface operations because they would result in a high rate of unwanted alerts.
The advent of Autonomous Dependent Surveillance-Broadcast (ADS-B) systems, by which aircraft and surface vehicles transmit their own state data (identity, classification, position, velocity, track angle, etc.), and by which an aircraft may receive the state data from other aircraft and vehicles, enables the possibility of designing a system that can provide useful alerts against potential collisions. In particular, the availability of position data (latitude, longitude) derived from satellite-based Global Navigation Satellite Systems (GNSS) over the ADS-B data link allows for the prediction of the future position of an aircraft or vehicle to an accuracy which is significantly better than that available with standard TCAS systems.
The present invention provides systems and methods for alerting a flight crew if a taxiing collision condition exists. An exemplary system on a host vehicle includes a receiver that receives information about one or more other vehicles on the ground, memory that stores information about the host vehicle, one or more sensors that determines information about the host vehicle and an output device. The system also includes a processor that determines one or more first protection zones around each of the other vehicles based on the received information about the one or more other vehicles, determines a second protection zone around the host vehicle based on the stored information about the host vehicle and the sensor information and generates an alert, if any of the first protection zones occupies at least a portion of the same geographic area as the second protection zone. The generated alert is outputted via the output device.
In one aspect of the invention, the received information includes state and vehicle type information. The state information includes position, ground speed, and one of heading or track information. The one of the other vehicles and the host vehicle are aircraft and the type information includes size information.
In another aspect of the invention, the protection zones include a width dimension that is based on vehicle size information, a base length dimension that is based on the size information, and a variable component of the length dimension that is based on the ground speed.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings:
The processor 26 sends and receives state information over a data channel via the communications system 32 (i.e., transponder). Using own-ship information (from the GPS or other system) and target (other) vehicle state (e.g., position, velocity, acceleration, track-angle and/or heading from the other vehicles 22 or a ground-based system 24) and vehicle type information, the processor 26 calculates two-dimensional buffer zones (boxes) that surround each of the own-ship 20 and the target vehicles 22. The processor 26 outputs an alert to the output device(s) 40 when the zones intersect.
A situational display of the traffic is provided on the display/user interface device 30 and the status of the traffic (i.e., the potential for a conflict) is depicted and/or an aural alert message is provided to the flight crew via the output device (e.g., headphones, speakers, tactile device) 40.
The present invention uses ADS-B state data received from the other aircraft or vehicles 22 and/or state data that is rebroadcast from a surface installation (the ground-based system 24), own-ship state data, type information, and one or more algorithms, to generate the zones and provide an alert against a potential collision on the surface of the airport that is not part of the runway environment (i.e., against potential collisions at relatively low speeds). For example, the rebroadcast state data includes Autonomous Dependent Surveillance-Report (ADS-R) data or data derived from surface radar and broadcast from a separate surface installation (i.e., Traffic Information Service Broadcast (TIS-B)). The one or more algorithms provide the flight crew with a display of potentially conflicting traffic in the case of a detected conflict. The alerting algorithms are designed such that the rate of unwanted alerts remains acceptably low.
The invention uses position, velocity, and track angle (or heading if speed is below a threshold value) data from the own-ship 20 and the other vehicles 22 to predict future relative positions of the own-ship 20 and the other vehicles 22. A map of airport taxiways is not necessary for performing this analysis.
In one embodiment, the processor 26 generates the buffer zone using physical size information of the own-ship and the traffic target. Size information (e.g., wing span and length) for the own-ship is derived by the system during installation, since the system “has knowledge” of the type of aircraft it is installed on. Size information for a traffic target is derived from the received ADS-B data by examining the “category” parameter transmitted by the target vehicle. This provides rough knowledge of size in the sense of “ground vehicle, small aircraft, medium aircraft, large aircraft”.
In one embodiment, the ADS-B data for ground vehicles contains a “vehicle size” parameter, which is used to more accurately determine the dimensions of the protective box (buffer zone). Alternatively, more precise size information is derived by using the “Mode S” code number, which is transmitted by each aircraft on ADS-B. The Mode S code number is unique to the individual aircraft. The processor 26 determines the physical dimensions of the target aircraft by comparing the Mode S code number to a database of all registered aircraft according to Mode S code numbers to obtain aircraft type. The database is stored in the memory 34.
In one embodiment, the size of the box (buffer zone) has a fixed width dimension that is based on vehicle type information. The length dimension has a base minimum value that is based on vehicle type information. A forward dimension (L) of the length dimension varies according the vehicle's velocity. The following is example equation:
L=K1*velocity2+K2*velocity+K3.
As shown in
In one embodiment, different algorithms are used to define differently sized boundary boxes. Intersection of the differently sized boxes would trigger different types of alert conditions (e.g., caution, warning).
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, the function performed by the present invention is disabled in certain areas of the airport, such as the runways and the gate area in order to reduce nuisance warnings. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
