Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Patent
1991-05-23
1993-03-09
Raevis, Robert
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
G01M 1900
Patent
active
051917815
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a ratiometric signal correction system for a vehicle electronic control system that may be used for controlling an internal combustion engine, electronic transmission, or other vehicle components.
BACKGROUND OF THE INVENTION
Many electronic control systems in a vehicle use the throttle valve angle as a control signal. For example, an electronic throttle control uses it for a position feedback control of the butterfly valve, and a Motronic system uses it for control of fuel injection, ignition timing and in certain cases of exhaust gas recirculation. Another example is an electronic transmission control which uses a throttle valve angle to detect when to shift gears. As a result there may be a plurality of control units each requiring access to a butterfly valve angular position signal.
When, for cost reasons, only one throttle valve angle sensor is supposed to be read by more than one control unit, problems arise particularly with analog signals, and the magnitude of the signal may suffer and may not be present with the same accuracy in all control units. Variations may arise from manufacturing tolerances in components and from random operating variables such as stray voltages. Such variations can result in the fact that only one electronic control unit (ECU) can sense the throttle angle with sufficient accuracy, whereas the other ECUs will suffer considerable errors. Such errors can be a change in slope and/or a displacement or offset of the characteristic curve of voltage against butterfly valve angular position. Such errors in detection do not promote optimum or efficient operation of the internal combustion engine and other functions of the vehicle. The present invention overcomes these problems as set forth in the remainder of the specification and shown in the attached drawings.
Summary of the Invention
According to the present invention, there is a first or master ECU that determines or reads the throttle valve angle signal with full accuracy and the master ECU generates periodically trigger signals for each of the other control units ("slaves") to mark the feedback signals at two predetermined angular positions of the butterfly valve. This makes it possible for each of the slave control units to bring its characteristic curve into agreement with regard to both slope and position, or offset with those of the characteristic curve of the first or "master" electronic control unit. Any change in slope can be corrected by applying a correcting factor to the incoming analog signal multiplicatively. In most cases, in each control unit, the analog positional feedback signal is applied to an analog-to-digital converter in order to provide a digital signal for further processing and this enables any displacement or offset of the characteristic curve to be readily accommodated.
According to a feature of the present invention, the first or master control unit must have an adaptive algorithm to determine the closed throttle position and to generate an idle signal from the respective angle. The slave ECUs can either have their own idle determining algorithms to detect the idle position or can receive an idle trigger signal from the first or master ECU on an existing interface line. Adaptive determining controls are known to those skilled in the art.
Another feature of the present invention enables the second predetermined angular position of the throttle valve to be so chosen that it can reasonably be expected to be reached under normal driving conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of part of a positional feedback signal system for two control units to illustrate how variations in characteristic curves of signal voltage in relation to angular position of a butterfly valve can arise.
FIG. 2 is a graphical illustration of such variations in characteristic curves referred to in FIG. 1.
FIG. 3 is a block diagram of a set of ECUs with signal correction incorporating the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
REFERENCES:
patent: 4901561 (1990-02-01), Glowczewski
Raevis Robert
Robert & Bosch GmbH
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