Communications: electrical – Continuously variable indicating – With meter reading
Reexamination Certificate
1998-12-31
2001-05-08
Crosland, Donnie L. (Department: 2736)
Communications: electrical
Continuously variable indicating
With meter reading
C340S933000, C340S010330, C340S010340, C701S019000, C246S00100C, C246S16700M, C303S128000
Reexamination Certificate
active
06229452
ABSTRACT:
BACKGROUND
This invention relates generally to ECP freight train braking systems and, more particularly, to a method for implementing low power ECP trainline communications whereby power consumption is reduced to a level such that sufficient power can be provided by a standard locomotive battery to indefinitely power the ECP equipment on each car.
The AAR has defined rail industry specifications for Electrically Controlled Pneumatic (ECP) braking based upon use of Echelon LonWorks, PLT-10A power line overlay transceiver version, as the means to communicate between cars and the lead locomotive. The communication specifications, as presently defined, require the Echelon transceiver to be “on” at all times, in order to be ready to receive brake commands from the locomotive, as well as to respond to routine status polling requests.
The Echelon transceiver has a power demand of approximately 300 mW when in receive mode and 2.5 W when transmitting. Message lengths for transmissions are typically on the order of 20 ms long. The average car transmission duty cycle is on the order of two times per minute (except for the last car in the train, which transmits each second). Therefore, the average power demand associated with the Echelon transceiver is on the order of 320 mW.
The AAR specifications allow an average power budget of 10 W per car. To supply this level of power, it is necessary to provide a nominal 230 VDC trainline, for a 160-car train, with a 12,000-foot length. This has resulted in the need for a 74 to 230 VDC DC-DC power supply on a locomotive in the consist, with a power rating of 2,500 W, to provide sufficient ECP power for 160 cars and losses due to cable resistance.
A low-power ECP system emulation system with an average power requirement budget under 500 mW in “emulation” mode is disclosed in commonly owned copending U.S. patent application Ser. No. 09/224,540, titled “RAILWAY EMULATION BRAKE,” filed on Dec. 31, 1998, and is hereby incorporated herein by reference. That system provides for powering an “all electric” ECP valve system using the 74 VDC from the locomotive, while emulating a conventional pneumatic service valve operation. The power budget for that system is based upon use of the Echelon transceiver only for system set-up and alarm reporting. It does not allow for the full ECP functionality of electrically activated brake application and graduated release of brakes. The addition of approximately 320 mW associated with having the Echelon continuously on for full ECP functionality cannot be afforded in a power budget low enough to operate on 74 VDC.
Additionally, commonly owned copending U.S. patent application Ser. No. 09/224,541, titled “RAILWAY LOCOMOTIVE ECP TRAINLINE CONTROL,” filed on Dec. 31, 1998, is also hereby incorporated herein by reference.
In a very low power ECP trainline type of system the Echelon receiver cannot be powered all the time, as it is in a conventional system, since the Echelon receiver consumes too much power. Thus it is necessary to provide for a “Master Controller” (“MC”) on the locomotive, i.e. the HEU, to tell each freight car in the train to turn its Echelon receiver “on” so that the MC can issue commands to the freight cars. Also, in a low power ECP system, since the communications device, i.e. the Echelon transceiver, is normally turned off, it is necessary to provide for each car to periodically report their status to the MC. Moreover, failure conditions need to be handled in a safe manner.
Accordingly, there is a need for a low power ECP communication system wherein the Echelon transceiver is operated on an intermittent basis, as needed to reduce the average power demand under 100 mW, while still providing full functionality, per AAR ECP specifications. Thus, a fully functional ECP system can be provided with the power supplied by the standard 74 VDC locomotive battery along with the safe management of failure conditions.
SUMMARY
A low power ECP trainline communication method is provided wherein power consumption by each freight car's on-board ECP transceiver, typically the Echelon transceiver, is minimized to a level where the system can be reliably and indefinitely powered by a standard, normally 74 VDC, locomotive battery. As a result, it is not necessary to always provide a 230 VDC trainline and all of the requisite associated electrical equipment in order to operate a train in an ECP environment. For versatility, the ECP freight cars can be equipped to operate in dual modes. Upon initial train start up, each ECP freight car can detect the prevailing ECP trainline power. If 100 to 230 VDC is detected, normal AAR standard ECP protocol with the associated higher power limits is implemented. However, if less than 100 VDC is detected, a low power ECP communications mode according to the invention is implemented. The low power communication method includes placing the Echelon transceiver in a sleep mode during normal operation and waking it up when desired. The locomotive MC can control a device, or circuitry, on each ECP freight car to put to sleep or wake up the Echelon transceiver. Control over waking up the Echelon transceiver can be instituted by making the wake-up command sensitive to the length of the message sent out by the MC. For example, routine status messages sent by the MC to each car are normally on the order of 20 ms. Therefore, the wake-up command can be made substantially longer, for example 50 ms. Similarly, a series of shorter messages spanning the 50 ms time period can also be used to issue the wake-up command. To return the Echelon is to sleep mode after it has been turned “on,” the MC can issue a specific command to return the Echelon to sleep. Alternatively, if no message is received after a set time period, for example 2 minutes, the device, or circuitry, on the freight car can automatically return the Echelon to sleep. Additionally, the signal strength of the message sent by the MC can be utilized to identify the wake-up command. Another alternative for controlling the sleep/awake status of the Echelon transceiver is by also making the wake-up command sensitive to ECP trainline power status. Specifically, detection of zero trainline power is a signal to wake-up the Echelon transceiver. The latter type of control also provides a degree of protection in failure circumstances.
Other details, objects, and advantages of the invention will become apparent from the following detailed description and the accompanying drawings figures of certain embodiments thereof.
REFERENCES:
patent: 4344238 (1982-08-01), Frasier
patent: 5064251 (1991-11-01), Romansky
patent: 5681015 (1997-10-01), Kull
patent: 5856788 (1999-01-01), Walter et al.
patent: 5959568 (1999-09-01), Woolley
patent: 5984427 (1999-11-01), Kettle, Jr.
Buchanan Ingersoll P.C.
Crosland Donnie L.
Westinghouse Air Brake Technologies Corporation
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