Train schedule repairer

Details Train schedule repairer Train schedule repairer

1998-05-22

2002-10-01

Nguyen, Tan (Department: 3661)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

Railway vehicle

Reexamination Certificate

active

06459964

ABSTRACT:

BACKGROUND OF THE INVENTION
It is possible to dramatically increase the efficiency of train movements by optimizing the schedule of train movements to account for interactions between trains such as meets, passes, merges, and contention for terminal resources. One approach is embodied in the meet/pass planners incorporated in some current CAD systems. These meet/pass planners are actually decision-aids which assist an operator in making a decision over which train to place on which siding in order to resolve an impending conflict between trains. In Matheson et al. U.S. Pat. No. 5,623,413, issued Apr. 22, 1997, entitled “Scheduling System and Method”, a new approach was proposed which provided a detailed schedule for each trains movements over an entire crew shift. Such a schedule is referred to in this document as a train movement plan. A train movement plan is defined as a detailed schedule for each train identifying each track element and switch that the train moves over and the time that such movement occurs.
Preparing a movement plan is a computationally intensive process which requires significant computer resources. Once the plan is prepared, it may be implemented either automatically or manually. Implementation involves coordination between the train crews operating the trains and the dispatcher (controller) who issues movement authorities and controls remotely controlled switches and signals. A movement plan provides the basis for automatically controlling signals and switches and ultimately forms the basis for automatic operation of the trains themselves. If in the course of implementing a plan, deviations from the plan occur, the movement plan may be damaged and no longer provide a solution to all train conflicts. Railroad operations must continue while a new plan is being prepared. A schedule repairer is a means of providing timely alterations to a damaged movement plan to account for deviations from the plan caused by mechanical failure, human failure, unforeseen activities, and incorrect data.
Generally, in prior art scheduling systems, the schedule of operation of the trains is fixed, often months in advance, based upon historic average trip times. Because the schedules are based upon averages it is not possible to schedule the details of meets and passes unless the rail traffic is very light.
Moreover, typical scheduling systems use a fixed set of priorities and routes resulting in only a minimal amount of flexibility to work around problems. These systems do not have the predictive intelligence to plan beyond the next few blocks as monitored by the signal system.
The typical scheduling system used to generate global movement plans utilize simulation techniques with a form of branch and bound search technique to generate conflict free fine grain schedules for the trains within the scope of the scheduling system. These scheduling systems are not amenable to solving the real time deviations experienced in implementing the movement plan due to time constraints. As such, the prior art scheduling systems can not account for conflicts in the schedule which are created due to deviations from the movement plan. Such conflicts are typically resolved through human intervention of the train dispatchers.
For example, a branch and bound based scheduling system may take several hours to generate a global movement plan. Accordingly, such fine grained movement plans may only be generated daily. Such a scheduling system is not capable of resolving conflicts that arise due to the normal deviations experienced in a railway system. Other approaches use a form of decision support tool in which a dispatcher may propose a solution to a conflict and view the ramifications of his solution. Such an approach is limited by the skill of the dispatcher and does not offer the growth to fully automatic operation.
For a further explanation of the utilization and the difficulties associated with scheduling systems, refer to the Matheson et al. U.S. Pat. No. 5,623,413, issued Apr. 22, 1997, entitled “Scheduling System and Method”, and having some inventors in common with the present application.
The present invention incorporates predictive schedule repairing which will continuously adjust train routes and controls in real time so that system throughput is optimized. One advantage of this look ahead schedule repairer is that intelligent decisions can be made due to the collection of real time data as well as the use of predictive algorithms which are able to estimate potential conflicts, resolve the conflicts and leave the rest of the movement plan undisturbed in a very short amount of time.
One of the benefits of the present schedule repairer system is the improved throughput over the rail that results from planning efficient train movements. Unlike other approaches which require the entire schedule to be regenerated which can not dynamically revise portions of the movement plan, the present invention can rapidly react to changes in predicted needs and create a revised movement plan within thirty seconds. The schedule repairer constantly receives train performance data and compares that to the movement plan. Adjustments to the train movement plan may be accomplished frequently in order to stay current with the activities on the railway system.
A very important aspect with the use of precision scheduling is the ability to handle deviations from the movement plan when they occur. The most common problem with fixed schedules that are set up far in advance is that conflicts occur which cause elements of the network to get off schedule, and those off-scheduled elements will ripple through the system causing other elements to get off-schedule. For example, the late arrival of a train at a siding may delay the progress of another train which was being met at the siding, and this delay may cause the second train to arrive late for a meet with a third train. This cascading of effects, if not promptly addressed, often leads to track congestion with the result that crews exceed their time of service and terminals become congested with serious reductions in train performance. These ripple effects are common and the standard operating procedures for railroads task the dispatcher with manually taking action to minimize the impact. With the increasing traffic levels on today's railroads, this task exceeds the capability of all but the most competent dispatchers. Due to time constraints, other scheduling systems, and decision support systems are unable to revise the movement plan in sufficient time to resolve the conflicts while preventing the propagation effects described earlier.
A key element of the train schedule repairer system as provided by the present invention is that it has continuous monitoring of conflicts as they occur, and allows rescheduling to compensate for the presence of these conflicts in the affected portion of the movement plan in a timely fashion. This exception handling capability begins with the conflict being predicted and the available options for the effected trains identified. The available options for the effected trains are evaluated to determine which option will cause the least impact to the rest of the movement plan. Once an option is selected the schedules for the effected trains are adjusted. The movement plan is then evaluated for any conflicts which may have been caused by the adjusted schedules. If a conflict is predicted, the schedule repair cycle just described repeats itself until the adjusted schedules result in a conflict free movement plan. In order to control the number of iterations required to develop a conflict free movement plan, the schedule repair horizon can be constrained so that any conflicts which arise beyond a set time horizon are not resolved in the current repair cycle.
For example, a given train which has deviated from its plan in excess of a predetermined tolerance could cause a conflict that could be corrected simply by small changes to the adjacent trains. On the other hand, an event of a larger magnitude such as a derailment which fouled a g

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