Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-11-11
2001-04-10
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S035000, C340S008100, C324S115000, C324S166000, 36
Reexamination Certificate
active
06216062
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to vehicle instrumentation including speedometers and tachometers, and in particular to a display system allowing for the smooth display of changing but irregularly transmitted data.
Driver display data that was once transmitted as analog voltages (e.g., fuel level) or mechanically (e.g., road speed) is now transmitted as digital words in serial fashion on a digital communications network within the vehicle. The digital words representing data from different sources may be interleaved to be transmitted on a single cable (“time multiplexed”) thereby substantially reducing wiring weight and costs. Display devices may be attached to this network to receive and display data related to their function. Such displays may include those providing numeric outputs (“digital displays”) or those having a moving pointer (“analog displays”).
Efficiencies in circuitry may be obtained if several vehicle sensors communicate with a single network interface card. The interface card converts data from the sensors to the proper format for transmission on the network and handles the necessary network protocols.
Often a network interface card will process both engine control data such as that from oxygen, air mass and fuel flow sensors, as well as driver display information from speedometer and tachometer senders. During certain times of rapidly changing engine conditions, such as during acceleration, the transmission of higher priority engine control data may interfere with the regular transmission of driver display information. This can result in a “stepping” or jerkiness in the operations of displays such as the speedometer or tachometer, which are also receiving rapidly changing data.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method of sending display data on an irregular interval without producing steps or jumps in the resultant display. This allows display data to be easily integrated with higher priority data on a common network interface. In the invention, if a digital word is not received within the regular interval, the display uses an extrapolated value based on the previously received digital word plus a fraction of the difference between the last two previously received digital words. The extrapolated digital word prevents sudden jumps in the display at limes when the displayed value is rapidly changing. Because, the extrapolation uses a simple fixed fraction of the difference between previously received digital word values, it does not require a recording of the time at which the previous digital words arrived or complex calculations such as would be required for linear extrapolation techniques.
Specifically then, the present invention provides a display system for use with a time-multiplexed digital communication network. The system includes a data sender attached to the network and associated with a physical object such as a rotating shaft to communicate on the network on an irregular interval, a series of first digital words representing a measurement of the physical object. A data receiver receive, the digital words on the irregular interval and produces second digital words on a periodic interval, the second digital words having values extrapolated from the first digital words. A display system receives the second digital words and provides a human readable display of the data of the second digital words.
It is thus one object of the invention to provide a display system that may accommodate irregular transmission rates inherent in the efficient use of network communication resources.
The extrapolation may extrapolate a current second digital word from the first digital word by calculating a difference between a previous first digital word prior to the current second digital word and a preceding first digital word prior to the previous first digital word. The current second digital word may be set to a value equal to the sum of a portion of the difference and the previous first digital word.
Thus it is another object of the invention to provide an extrapolation method that does not require recording times of receipt of the digital words or complex arithmetic operations necessary for true linear extrapolation.
The receiver may include a timer generating a periodic interrupt signal and a microprocessor responding to the periodic interrupt signal to extrapolate a current second digital word.
Thus it is another object of the invention to provide a simple method of producing a regular periodic series of digital words to the display unit such as may prevent perceivable stepping in the display.
The data receiver may further provide a filtering of the rate of change with time of the second digital words prior to their receipt by the display system. This may be done, for example, by creating a series of current filtered second digital words, each current filtered second digital word equal to the sum of a current second digital word times 1/m plus a previous filtered second digital word prior to the current filtered second digital word times (m−1)/m where m is an arbitrary factor controlling the amount of filtering.
Thus it is another object of the invention to provide flexible adjustment in the trade-off between elimination of jumps in the display and fast response of the display to changes in the displayed data. Adjustment of the filter constant m controls the amount of filtering.
A subsequent filtering stage may be provided in which a set of twice filtered second digital words are created, each current twice filtered second digital word equal to the sum of a current filtered second digital word time, 1
and a previous twice filtered second digital word prior to the current filtered second digital word times (n−1)
where n is an arbitrary factor independent of m controlling the amount of filtering. Further, a series of blended filtered second digital words may be created, each being a combination in a predetermined proportion of the current filtered second digital word minus the current twice-filtered second digital word.
Thus it is another object of the invention to provide a filter that allows control of overshoot as is represented by the second filtered digital words.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessary represent the full scope of the invention, however, and reference must be made to the claims herein for interpreting the scope of the invention.
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Cwik Terry Thomas
Kanoza Jeffrey Todd
Schnoes John Edward
Smith Richard Stanley
Cuchlinski Jr. William A.
Quarles & Brady
To Tuan C.
Visteon Global Technologies Inc.
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