Engine speed control

Details Engine speed control Engine speed control

2000-06-20

2001-10-23

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Engine speed regulator

Idle speed control

C123S339200, C123S352000, C701S110000

Reexamination Certificate

active

06305350

ABSTRACT:

TECHNICAL FIELD
The present invention relates to load compensation for internal combustion engine speed control.
BACKGROUND OF THE INVENTION
Conventional internal combustion engine idle speed control systems make use of a proportional-integral-differential (PID) controller of air and a proportional controller of spark. The bandwidth of a PID controller is limited and, to obtain the required accuracy, idle speed control systems rely mainly on feed-forward airflow compensation. The typical feed-forward controller has tens of lookup tables.
The idle control systems, described in U.S. Pat. No. 5,463,993 to Livshits et al, in U.S. Pat. No. 5,421,302 to Livshits et al, and in U.S. Pat. No. 5,577,474 to Livshiz et al, each being assigned to the assignee of this application, and each being hereby incorporated herein by reference, enable significant improvement of idle speed control performance.
The controller described in U.S. Pat. No. 5,463,993 combines load rejection and steady state control but requires very qualified people to calibrate, must be defined for all environmental conditions, and requires accurate physical based models. In the implementation of the idle speed controllers, described in U.S. Pat. No. 5,463,993 and U.S. Pat. No. 5,421,302, oscillations of engine speed (RPM) were found in different altitudes under multiple park-drive transitions. Furthermore, the controller described in U.S. Pat. No. 5,463,993 does not have separation of mass airflow and throttle position control. This means that every change of the actuator will require a re-calibration of this controller for all altitudes.
The controller described in U.S. Pat. No. 5,577,474 incorporates the effects of slowly varying parameters into the idle speed control system but does not take into account initial operation at different altitudes, takes a long time to adapt the model to slowly varying variables, such as barometric pressure, and contains a multitude of lookup tables.
What is needed is a robust idle speed controller incorporating load rejection with barometric correction for different altitudes.
SUMMARY OF THE INVENTION
The present invention is an idle control system for internal combustion engines providing load rejection and/or load compensation for a given engine speed reference and barometric pressure wherein the present invention accommodates for varying engine speed references and for varying barometric pressures, such as at different altitudes. The present invention consists of a control system incorporating a Load Compensator, including a multitude of sub-control blocks, as depicted in
FIG. 1
, to be described later.
This invention is a method to improve performance, improve repeatability of calibration, and reduce calibration efforts of an idle speed control system. It can be used in both engine speed control and coast-down control. This is achieved through an accurate estimation of mass airflow (MAF) as a function of engine speed, torque, and barometric pressure (B), by a separation of load rejection and steady state control, and increasing engine damping as a function of manifold air pressure (MAP) and B.
The present invention may be used to replace the Torque Controller, MAP Controller, and State Estimator in the idle control system described in U.S. Pat. No. 5,463,993 or as an independent unit as part of any other engine speed or coast-down control incorporated in an idle control system.
The present invention provides both spark advance (S) and throttle control based on MAP and engine speed. The throttle control portion consists of a RPM (engine speed) Controller, Load Compensator, Feed-forward Controller and Mass AirFlow/Idle Air Command (MAF/IAC) Converter. The Load Compensator generates the needed airflow to compensate for the torque of the engine load. The Load Compensator compensates for unexpected loads and works with the Feed-forward Controller to reject anticipated loads.
The calibration procedure is fully automated and is shown in
FIGS. 3
,
4
, and
5
A -
5
D, to be described later. The number of calibration var and the number of lookup tables is reduced by a factor of eight. The automated calibration increases the repeatability of the control system.
It is therefore an object of the present invention to provide improved performance, improved repeatability of calibration, and reduced calibration efforts of an engine idle speed control system.
This and additional objects features of the present invention will become apparent from the following specifications.


REFERENCES:
patent: 5421302 (1995-06-01), Livshits et al.
patent: 5463993 (1995-11-01), Livshits et al.
patent: 5577474 (1996-11-01), Livshiz et al.
patent: 5996553 (1999-12-01), Sanvido et al.
patent: 6016460 (2000-01-01), Olin et al.

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