Method for advanced communication-based vehicle control

[0002] This application claims the benefit of U.S. Provisional Application No. 60/268,352, filed Feb. 13, 2001, which is hereby incorporated by reference in its entirety.

[0003] This invention relates generally to train movement, and more particularly to controlling the movement of a plurality of trains over a predetermined track layout.

[0004] Traditional rail traffic signal systems use an extensive array of wayside equipment to control railway traffic and maintain safe train separation. In these traditional systems railway control is achieved by detecting the presence of a train, determining a route availability for each train, conveying the route availability to a train's crew, and controlling the movement of the train in accordance with the route availability.

[0005] The presence of a train is typically detected directly through a sensor device, or track circuit, associated with a specific section of the rails, referred to as a block. The presence of a train causes a short in a block's track circuit. In this manner, the occupancy of each block is determined. Vital decision logic is employed, utilizing the block occupancy information in conjunction with other information provided, such as track switch positions, to determine a clear route availability for trains. The route availability information is then conveyed to a train crew through physical signals installed along the wayside whereupon a train crew encounters the signal and visually interprets the meaning of the displayed aspect. Alternatively, the route availability information is conveyed to train crews by passing information from the wayside to the train through the rails, referred to as continuous cab signaling, or through transponders, referred to as intermittent cab signaling, so that aspect information can be directly displayed in the cab. The train movement is then controlled by crew actions based on displayed aspect information and, in case of failure by the crew to take necessary actions, through optional speed enforcement.

[0006] Traditional railway systems require the installation and maintenance of expensive apparatus on the wayside for communicating route availability to approaching trains. The wayside equipment physically displays signals, or aspects, that are interpreted by a crew on board a train approaching the signaling device.

[0007] Thus, the interpretation of signal aspects can be subject to human error through confusion, inattention or inclement weather conditions.

[0008] An alternative to conventional track circuit-based signaling systems are communication-based train control (CBTC) systems. These train control systems generally include a computer at one or more fixed locations determining the movement authority and/or constraints applicable to each specific train. The computer then transmits this train-specific information in unique messages addressed or directed to each individual train.

[0009] In one embodiment, a method is provided for controlling movement of a plurality of vehicles over a guideway partitioned into a plurality of guideway blocks. The method uses a control system including an onboard computer (OBC) located on board each vehicle, at least one server for communicating with the OBCs, and a vehicle location tracking system. The method comprises the steps of determining a composite block status for all guideway blocks, broadcasting the composite block status to the OBCs, and controlling movement of each vehicle based on the composite block status.

[0010] In another embodiment, a method is provided for controlling movement of a plurality of vehicles over a guideway partitioned into a plurality of guideway blocks. The method uses a control system including an onboard computer (OBC) located on board each vehicle, at least one server for exchanging communication with the OBCs, and a vehicle location tracking system. The method comprises the steps of providing a predetermined mapping data set to each OBC that represents a guideway layout, equivalent block boundaries, and related characteristics of the guideway and utilizing a particular OBC to determine on board a block occupancy for the vehicle including that particular OBC. That particular OBC utilizing the mapping data set.

[0011] In a further embodiment, a system is provided for controlling movement of a plurality of vehicles over a guideway partitioned into a plurality of guideway blocks. The system comprising an onboard computer (OBC) located on board each vehicle, at least one server configured to communicate with the OBCs, and a vehicle location tracking system. The system is configured to utilize each vehicle's OBC to determine a block occupancy for that respective vehicle, determines a composite block status based on the block occupancy of each vehicle, transmits the composite block status to each said OBC, and controls movement of the vehicle including a respective said OBC based on the composite block status.

[0012] FIG. 1 is a block diagram of a system for controlling the movement of a plurality of vehicles on a guideway in accordance with one embodiment of the present invention.

[0013] FIG. 2 is diagram of a portion of a guideway, utilized by the system in FIG. 1, partitioned into equivalent blocks.

[0014] FIG. 3 is an exemplary embodiment of an onboard display of information to a vehicle crew using the system described in FIG. 1.

[0015] FIG. 1 is a block diagram of a system 10 for controlling the movement of a plurality of vehicles on a guideway (not shown) in accordance with one embodiment of the present invention. Each vehicle includes one or more vehicular units linked together to form a single vehicle. System 10 includes an onboard computer 14 (OBC) on each vehicle, a server 18 located at a fixed remote site, and an onboard tracking system 22 for tracking the position of each vehicle. OBC 14 includes a processor 26 that performs vital and non-vital calculations as well as vital coding and decoding of information, and a data storage device 30, such as a database. Additionally, OBC 14 is connected to an OBC display 34 for viewing information, data, and possible graphical representations, and an OBC user interface 38 that allows a user to input information, data, and/or queries to OBC 14, for example a keyboard or a mouse. Likewise, server 18 includes a processor 42 that performs vital and non-vital calculations as well as vital coding and decoding of information, and a data storage device 46, which, in one embodiment, includes a database. Furthermore, server 18 is connected to a server display 50 for viewing information, data, and, in one embodiment, graphical representations. Server 18 is also connected to a server user interface 54 that allows a user to input information, data, and/or queries to server 18, for example a keyboard or a mouse.

[0016] Both OBC 14 and server 18 interface with various control elements (not shown) such as sensors, actuators, alarms, and wayside devices such as guideway switches, i.e., turnouts, for selecting among two or more diverging routes, signals and occupancy detection circuits, e.g., track circuits. OBC 14 exchanges information with server 18 via a communications system such as a mobile radio network. Tracking system 22 includes position sensors (not shown) and devices (not shown), such as a global positioning system (GPS) receiver, a tachometer, a gyroscope, an odometer, location tags along the guideway and an onboard tag reader. In one embodiment, tracking system 22 is separate from OBC 14 and receives inputs from a least one GPS satellite (not shown). The onboard system may optionally receive and utilize differential correction information to improve location determination accuracy and/or integrity. FIG. 1 shows onboard tracking system 22 separate from OBC 14, however, in another embodiment, OBC 14 includes tracking system 22. In yet another embodiment, tracking system 22 has components that are separate from OBC 14 and components that are included in OBC 22. For example, tracking system 22 components, such as, a global positioning system receiver and software algorithms are included in OBC 14, while other tracking system 22 components, such as, a tachometer, a gyroscope, an odometer, and a guideway tag reader are located separate from OBC 14. In still another embodiment, tracking system 22 receives end of vehicle and front of vehicle information, and inputs from an operator, such as a vehicle engineer, containing information and data relating the position of a vehicle, to determine the location of at least one of the front of the vehicle and the end of the vehicle.

[0017] In an alternate embodiment, server 18 is located at a mobile site such as a mobile office structure or a train. In a further embodiment data storage device 30 is not included in OBC 14. Instead data storage device 30 is connected to OBC 14. In addition, data storage device 46 is not included in server 18 but instead is connected to server 18.

[0018] In one embodiment, OBC 14 interface with a front of vehicle device 56, which communicates with an end of vehicle device 58 located at the end of the vehicle. Devices 56 and 58 provide vehicle integrity information by detecting possible vehicle separations. In a further embodiment, devices 56 and 58 provide information regarding the length of the vehicle and the location of the end of the vehicle. Alternative potential sources of vehicle length data are external systems (not shown), such as automatic equipment identification (AEI), hot box detectors, axle counters, track circuits, manual entry, and/or information systems.

[0019] FIG. 2 is diagram of a portion of a guideway 60 partitioned into equivalent blocks 64. Guideway 60 includes a terrestrial based network (not shown) of guideways that vehicles (not shown) use to move across terrestrial areas of varying size. Server 18 (shown in FIG. 1) contains guideway data, such as equivalent block boundaries and signal logic, that relate to a portion of, or all of, guideway 60. In an alternative embodiment, server 18 contains terrain data relating to guideway 60. In a further embodiment, a traditional signal design algorithm is used to partition guideway 60 into equivalent blocks 64, which represent adjacent sections of guideway 60. The algorithm utilizes information such as, the guideway data, weight of a vehicle, speed of a vehicle, length of a vehicle, and desired traffic capacity to define equivalent blocks 64. The algorithm determines the number and length of equivalent blocks 64 such that the equivalent blocks 64 can be of any number, and of differing lengths. In an alternative embodiment, the block lengths change dynamically as the characteristics of vehicles on a particular section of guideway changes. In one embodiment, the guideway blocks are defined to be small. The small defined blocks, in combination with the use of a braking distance calculation based on actual vehicle and guideway characteristic, allows vehicles to be safely operated with separations approaching the theoretical minimum. A further embodiment permits subdividing of existing conventional physical signaling blocks into smaller sections that are treated as equivalent blocks. This subdividing allows safe reduction of vehicle separation distance in areas where conventional signals driven by guideway circuits, e.g., track circuits, already exist and continue to operate. Additionally, FIG. 2 shows guideway 60 including passing sidings 68 and 72, which are partitioned into equivalent blocks 64.

[0020] In one embodiment, server 18 transmits, to each OBC 14, a vitally codified mapping data set containing data related to the characteristics of the guideway. In an alternative embodiment, an off-board source, other than server 18, broadcasts the codified mapping data set to the pertinent OBCs 14. The mapping data set is stored in database 30 and contains information and data such as equivalent block boundaries. In an alternative embodiment, the mapping data set contains related information such as permanent speed restrictions, temporary speed restrictions, grade, and information for interpreting signal aspects. In an alternate embodiment, server 18 transmits a subset of the mapping data set that is specific to a particular section of the guideway or to a particular geographical area. In an alternative embodiment, the mapping data set is predetermined and pre-loaded in database 30. In a further alternative embodiment, locally relevant mapping data is transmitted incrementally as needed from devices in or near the guideway, e.g., tags or distributed servers, so that long term storage and large uploads of mapping data are not required.

[0021] Referring now to FIG. 1, as a vehicle progresses along a route, OBC 14 determines the location of the vehicle based on data received from tracking system 22. Using information obtained by tracking system 22, e.g., vehicle length and integrity information as well as the mapping data set, OBC 14 determines which equivalent blocks 64 (shown in FIG. 2) the vehicle is currently occupying. Whenever a vehicle enters a new equivalent block 64, OBC 14 transmits a message to server 18 identifying which equivalent block 64 the vehicle has just entered, and whenever a vehicle leaves an equivalent block 64, OBC 14 transmits a message to server 18 identifying which equivalent block 64 the vehicle has just left. The messages are then stored in database 46.

[0022] In another embodiment, OBC 14 predicts and reports any equivalent block 64 that a vehicle will likely occupy before the vehicle can be stopped, for example those equivalent blocks 64 within braking distance of the vehicle. In determining predicted equivalent block occupancies, OBC 14 also applies a margin, increasing the predicted occupancy range to account for factors such as system delays resulting in latency before brakes are applied. The predicted equivalent block occupancies are transmitted to server 18 and stored in database 46Server 18 receives occupancy and clearance information from OBC 14 on board all vehicles utilizing the specific zone of guideway 60 (shown in FIG. 2) monitored by server 18. Additionally, server 18 receives information communicated from wayside devices such as switches or human (manual) input on board. Server 18 uses the reported occupancy and other data to derive an equivalent block status for each equivalent block 64 in a manner similar to that of the logic used in conventional wayside signaling equipment for determining signal aspects from connections with guideway circuits and wayside devices such as switches. The status for each equivalent block 64 is dynamic. The equivalent block status for each block 64 is either limited to one of just two possibilities, corresponding to block occupied or block free, or chosen from multiple possibilities. The multiple possibilities dictate various speed restrictions within equivalent block 64. In the simplest case of just two block status possibilities, a zero or low speed restriction applies in a block that is occupied whereas full speed up to the point of braking distance from the next occupied block entrance is allowed in a block that is not occupied. In alternative embodiments, besides additional levels of speed restriction, additional information is conveyed by the block status indications, such as whether more than one vehicle is in a block, and a diverging route where a vehicle has to turn off of the main line at a turnout.

[0023] Server 18 compiles and stores all equivalent block statuses in database 46, then derives a composite equivalent block status containing the equivalent block status information for all equivalent blocks 64 monitored by server 18. Server 18 broadcasts a composite equivalent block status message simultaneously to all vehicles within the zone of server 18 such that each OBC 14 on board every vehicle in the zone of server 18 receives the same information. In one embodiment, server 18 broadcasts composite equivalent block status updates periodically at a predetermined rate. In a further embodiment, server 18 broadcasts the composite equivalent block status updates asynchronously whenever an equivalent block status changes.

[0024] In one embodiment, communications between server 18 and OBC 14 utilize a terrestrial based radio network. Each OBC 14 on all the vehicles on the monitored guideway receive radio transmissions of the composite equivalent block status information originating from server 18. In alternative embodiments, communications between server 18 and OBC 14 utilize at least one of cellular and satellite communications.

[0025] FIG. 3 is an exemplary embodiment of a graphical representation 80 used to display information related to controlling or restricting the movement of a vehicle. Graphical representation 80 includes a current speed indicator 82, a speed limit indicator 84, a current milepost indicator 86, a track name indicator 88, a direction indicator 90, a target speed indicator 92, a distance to target indicator 94, a time to penalty indicator 96, and an absolute stop indicator 98, which are used to convey vehicle movement controls or restrictions. Based on composite equivalent block status messages received by OBC 14 (shown in FIG. 1), equipment on board each vehicle, such as display 34 (shown in FIG. 1), displays information or restrictions necessary to safely control the vehicle. As shown in graphic 80, information necessary to safely control the vehicle includes information pertinent to that vehicle, a target description, limits on the range of movement allowed for the vehicle, and speed restrictions that may be stored on board. In another embodiment, the display shows signal aspects such as red, yellow and green lights instead of target-based movement constraints. In addition, system 10 (shown in FIG. 1) includes an audible alarm unit (not shown), on board the vehicle, that provides warnings of such things as upcoming targets, limits, signal aspect changes to a more restrictive state or when braking action has been taken.

[0026] To react in a safe manner in the event of a communications loss between OBC 14 (shown in FIG. 1) and server 18 (shown in FIG. 1), if more than N, for example N=2, consecutive block status updates are not received by OBC 14, OBC 14 defaults to the most restrictive status for the blocks ahead. Exemplary restrictive statuses for a block include stopping the vehicle, reducing the speed to a low speed, such as about 20 miles per hour (mph) throughout the block, and stopping the vehicle at the entrance to the block and then proceeding at a low speed, such as 20 mph or less.

[0027] OBC 14 scans database 30 (shown in FIG. 1) retrieving static information pertaining to targets ahead, such as, speed restrictions, and dynamic data, such as occupied equivalent blocks. The static information designates whether a target is permanent, temporary, or aspect-related. Using the dynamic information in combination with the static information, OBC 14 determines if a lower speed restriction or any other type of target is being approached. OBC 14 then calculates a braking distance based on current speed, target location, and target speed, which may be zero, equating to a stop. In addition, OBC 18 considers guideway gradient and vehicle braking ability to refine the braking distance calculation. OBC 14 determines which target will first require the vehicle to reduce speed or stop.

[0028] In a further embodiment, based on the data communications infrastructure and data provided to OBC 14, additional information, such as guideway grade, locations of guideway features, for example crossings, defects detectors, and blocks occupied by other vehicles are displayed in graphic 80 in either graphical or textual format. The additional information is stored in database 30 and used in combination with previously described data to determine modifications in movement of a vehicle and provide information to the crew. The infrastructure also supports the transmission and display of other types of messages, for example bulletins, work orders, and e-mail. In one embodiment, the OBC user interface allows the crew to input information or requests for information that is used on board. In an alternative embodiment, the OBC user interface allows the crew to input information or requests for information to be transmitted off board.

[0029] When enforcement braking is used, OBC 14 calculates the distance and time to where braking must start in order to comply with the restrictions associated with each target. If the remaining time for any given target is less than 60 seconds, for example, time to penalty indicator 96 will numerically display the time remaining. If the time remaining is less than one second, for example, and the crew has not taken appropriate action to control the vehicle, the penalty brake will be applied.

[0030] Referring again to FIG. 1, in another embodiment, server 18 interfaces with office computers (not shown), for example a dispatching system, to receive information such as requests for routes to be cleared or switch positions to be changed. Additionally, server 18 furnishes information, such as vehicle locations in the form of equivalent block occupancies, to the office computers. Furthermore, server 18 obtains information used in affecting vehicle movements, for example temporary slow orders, guideway data such as grade, permanent speed restrictions, and equivalent signal locations, and vehicle data, such as vehicle length and weight.

[0031] In yet another embodiment, system 10 includes a plurality of servers 18 located at one or more locations such as various offices or various wayside locations. Thus, each server 18 is associated with specific equivalent blocks, and receives equivalent block occupancy information only from vehicles occupying the zone of equivalent blocks associated with a specific server 18. Therefore, each server 18 determines a composite equivalent block status unique to the equivalent blocks associated with its zone.

[0032] In a further embodiment, OBC 14 uses a conventional onboard cab signal processor (not shown) and an operator interface, such as interface 38. The OBC determines and reports equivalent block occupancies and receives composite equivalent block status information for each equivalent block 64 (shown in FIG. 2). However, OBC 14 synthesizes conventional cab signal codes that are structured like codes from guideway and wayside devices, but are actually communicated to OBC 14 from server 18. The synthesized signal codes are then used to drive the conventional cab signal processor instead of the code signals being detected by conventional cab signal sensors mounted on the vehicle near the guideway.

[0033] In yet another embodiment, conventional guideway blocks, as opposed to equivalent blocks, are used to determine block occupancy, block status, and composite block status. Conventional guideway block sizes are determined by physical divisions in the guideway created by conventional guideway occupancy detection circuit equipment.

[0034] In a still further embodiment, a pacing function is implemented to further improve railway operational efficiency. Movement planning functionality is incorporated into, or interfaced with, a dispatch system (not shown). The movement planner generates a movement plan for all vehicles within its realm of management with the objective of achieving optimal operations efficiency. The movement plan conforms with the laws of physics as well as safety constraints, such as those imposed by the equivalent block statuses. The movement planner transmits a relevant portion of the movement plan, referred to as a trip plan, to each OBC 14. Trip plans include Estimated Time of Arrival (ETA) and Estimated Time of Departure (ETD) for critical waypoints along the trip. Trip plan messages are sent in addition to, not in lieu of, composite equivalent block status messages. Functionality is added to OBC 14 to generate cues, for example, speed instructions for a vehicle driver which, if followed, control the speed of the vehicle in accordance with the plan. Messages transmitted from each OBC 14 in the form of equivalent block occupancy reports or precise location reports are used by the movement planner to determine if each vehicle is on schedule. If a vehicle falls off schedule to the extent of impacting other vehicles, the movement planner updates the movement plan and transmits a revised trip plan to the affected vehicles.

[0035] In another embodiment, a broken guideway detector is mounted on board each vehicle to monitor guideway continuity. Upon detection of a broken guideway, the guideway detector transmits a message to server 18 and notifies the crew who modifies vehicle movement based on the most restrictive aspect for the equivalent block where the break occurred. In an alternative embodiment, the guideway detector transmits a message to server 18 and server 18 notifies the crew. Additionally, notification of detection of a broken rail is transmitted to the OBC's 14 of nearby vehicles in order to inform crews of each vehicle so they may take appropriate action.

[0036] In yet another embodiment, system 10 achieves an automatic or driverless vehicle operation. OBC 14 interfaces with a vehicle throttle (not shown), onboard sensors (not shown), and a brake system (not shown) to automatically control vehicle movement in accordance with the controls and restrictions determined by OBC 14. The movement planner function and pacing function are used to direct vehicle movements. The driverless system controls the throttle and brake to conform with the trip plan but will not exceed the safety constraints dictated by the composite equivalent block status message and other restrictions. Alternatively, movement planner and pacing functions are not used to directly control throttle and brake. In this case, the OBC controls vehicle movements based on speed information in the composite block status received from server 18.

[0037] The system described above provides a method of achieving railway traffic densities or throughput levels commensurate with or better than those achievable with traditional wayside signaling systems without the use of track circuits or wayside signals. In addition, the cost of deploying, maintaining, and modifying signaling equipment, or equivalent equipment, is reduced.

[0038] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.