Communications: electrical – Selective – Intelligence comparison for controlling
Reexamination Certificate
1999-04-14
2001-04-10
Horabik, Michael (Department: 2735)
Communications: electrical
Selective
Intelligence comparison for controlling
C340S005270, C340S442000, C340S447000, C340S448000, C340S443000
Reexamination Certificate
active
06215389
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system and a method for receiving and discriminating unique codes from multiple transmitters. More particularly, the invention relates to an event-based system and method for receiving unique codes from multiple transmitters, such as tire pressure sensors, and building a table of those unique codes so that data received from the remote sources can be identified and validated.
2. Related Art
With the development of systems monitoring equipment for vehicles, it is known to monitor the pressure in a vehicle's tires by installing a transducer within each vehicle tire which can provide a perceptible indication of the pressure to the vehicle operator. These indications have included: a visible signal provided on the tire whereby the tire must be visually inspected by the operator, a magnetic field generated by the transducer which generates a warning on the instrument panel for the operator via a detector hard wired near the tire, and a radio transmitter interconnected to the transducer within each tire which provides a wireless signal to a receiver on the vehicle for providing a warning to the operator.
In the wireless tire pressure sensing and indication system mentioned above, transmitters are mounted within each tire which communicate with a receiver. The receiver is interconnected with a display device which can display whether any of the four tires has a low pressure condition. In order to distinguish between each of the tire-mounted transmitters, each of the transmitters is coded with a unique identification number (ID) indicating a particular tire position. Each of the transmitters thereby transmits a data frame containing both the ID and a signal corresponding to the pressure in the particular tire.
Because vehicles are often located nearby one another during operation, it is conceivable that the receiver could detect a signal from a neighboring vehicle and erroneously record the pressure signal as relating to the vehicle in which the receiver is mounted. Further, erroneous signals could also be recorded when the tires are rotated. Yet, further erroneous signals may result if the ID data is corrupted in a volatile memory location. It has been found to be important that a wireless tire pressure monitoring system be able to “learn” the IDs of the tire pressure transmitters associated with the vehicle.
Various solutions have been proposed to the problem of enabling the receiver to learn the IDs. One solution requires the operator of the vehicle to hold a magnet adjacent to each tire which causes the transmitter associated therewith to “wake up” and send a transmission containing the ID to the receiver. Another solution is proposed in U.S. Pat. No. 5,612,671, issued Mar. 18, 1997, titled “Method of Learning Tire Pressure Transmitter ID” (“the '671 patent”), wherein the receiver includes a microprocessor controller programmed to learn the IDs of the tire senders by recording the IDs in the controller memory as “main” senders presumed to be those on the vehicle wheels wherein subsequent new IDs are accepted as “reserve” senders. The '671 patent, however, detects faulty transmitters by measuring the number of transmission failures over a predetermined time period; transmission failures for every ID during the time period are stored as flags, and detection of faulty transmitters is conducted only after the time period expires for a given cycle. Because different transmitters often send signals at different rates, the predetermined time period selected in the '671 system may not be compatible with a particular set of transmitters, making the system less reliable. Thus, the effectiveness of the '671 system depends on the compatibility between the transmission rate of the transmitters and the predetermined time period in the system. If the predetermined time period is not adjustable by the user, this restriction unduly limits the user's selection of transmitters because the selected transmitter's transmission rate must be compatible with that time period.
There is a need for a time-independent, event-based system that operates independently of the transmission rate of the transmitters being sensed.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method and apparatus for discriminating between ID codes from desired transmitters and ID codes from undesired transmitters using a time-independent, event-based system. An array in memory has registers corresponding to ID codes from a group of desired transmitters. Each register has a corresponding ID code counter. The system also has an event counter. When an ID code is received from a transmitter, the system increments the event counter, and checks to see if the received ID code matches an ID code in the registers. If the received ID code matches an ID code or if the register is clear, the ID code counter corresponding to that register increments. Any register whose associated ID counter is below a predetermined ID counter threshold when the event counter exceeds a predetermined event counter threshold is cleared. Thus, ID codes from undesired transmitter can be cleared from the array.
In another embodiment, an auxiliary array with auxiliary registers and corresponding auxiliary ID code counters is provided, and matching and incrementing is conducted in a similar manner. In this embodiment, ID codes in the auxiliary array are made available to the main array by a checking routine. The system is especially adapted for use with automatically learning the ID codes from tire pressure senders in vehicles.
The auxiliary ID codes and associated code counters are used for main ID code replacement, which can occur, for example, if a car has a replacement tire with a transmitter having a new ID code. The system checks to see if the number of inactive ID codes matches the number of auxiliary ID codes that have counters exceeding a predetermined threshold, indicating an active auxiliary ID code. If so, the system moves the active auxiliary codes to the main array to replace the inactive main ID codes. If the number of inactive ID codes does not match the number of active auxiliary ID codes, the system provides an error message. The invention therefore does not require evaluating the number of event occurrences over a predetermined time period, but instead compares the number of events with time-independent thresholds.
Other objects, features, and advantages of the invention will be apparent from the ensuing description in conjunction with the accompanying drawings.
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Bangachon William L
Gentex Corporation
Horabik Michael
Price Heneveld Cooper DeWitt & Litton
Rees Brian J.
LandOfFree
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