Estimating Stopped Engine Crank Angle via Coast-Down Analysis

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Solution Overview

Problem

Existing crankshaft sensors fail to accurately determine the stopped engine crank angle and direction, especially when the engine is coasting or at low speeds, leading to inaccurate engine restarts and increased emissions due to reliance on predetermined coast-down models that do not account for engine bounce-back and varying operating conditions.

Innovation Solution

An engine control system utilizing a crank sensor and controller to determine crank speed and coast-down characteristics, estimating the stopped engine crank angle based on a coast-down model adjusted during laboratory conditions and tuned during engine operation, which accounts for frictional and pumping torques, and considers bounce-back angles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If variable reluctance sensors are used to determine crank angle and speed, then economical sensor cost is achieved, but the sensors cannot reliably indicate crank angle when the crankshaft is not rotating or at low speeds

Engineering Contradiction:

Improvesensor costVSAvoidcrank angle detection accuracy at low speed

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The system performs preliminary characterization of engine coast-down behavior during laboratory testing before actual engine operation. Coast-down models are developed and stored in advance, allowing the controller to accurately predict stopped crank angle even when sensor signals become unreliable at low speeds, thus maintaining measurement precision without requiring expensive alternative sensors

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If predetermined coast-down models are used to estimate stopped engine crank angle, then real-time computation is simplified, but accuracy is reduced due to inability to account for varying engine conditions and bounce-back

Engineering Contradiction:

Improvecontrol system complexityVSAvoidstopped crank angle estimation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Engine coast-down characteristics are pre-characterized during laboratory testing across various operating conditions, and these data are stored in the controller. During actual operation, the system selects and applies the appropriate pre-characterized model based on current conditions, achieving high accuracy without complex real-time computations

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors actual engine coast-down behavior and compares it with the predetermined model. When discrepancies are detected indicating changed engine conditions, the system updates or selects appropriate coast-down models to maintain accuracy, thus adapting to varying conditions while keeping the control structure relatively simple

Inventive Principle:

Principle #23Feedback

3Device complexity

If engine coasting is monitored using existing sensors, then additional hardware is avoided, but the sensors cannot detect crank direction or provide reliable signals at very low speeds

Engineering Contradiction:

Improvehardware complexityVSAvoidcrank rotation direction information

Core Design Contradiction:

Device complexityVSLoss of information

Solution Approach 1:

The system replaces direct mechanical sensing of crank direction with a computational approach. By analyzing the temporal patterns and frequency characteristics of the crank sensor signals during coast-down, the controller infers rotation direction and predicts the stopped position, thus obtaining direction information without additional mechanical sensors

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for accurate estimation of the stopped engine crank angle, reducing engine cranking time and emissions by accounting for varying engine conditions and bounce-back, without relying on expensive laboratory equipment for real-time adjustments.

Implementation Method 1

Crank angle and crank speed of a running engine are determined using various types of crankshaft sensors including variable reluctance (VR) type sensors

Methodology Applied

Scientific EffectVariable reluctance sensing: Magnetic Reluctance

Implementation Method 2

determine a coast-down characteristic based on the crank signal when the crank speed is greater than a threshold speed. The controller is also configured to estimate the stopped engine crank angle based on the coast-down characteristic

Methodology Applied

Scientific EffectCoast-down analysis:

Data Source

PatentUS8099998B2Apparatus and method for estimating stopped engine crank angle

Publication Date: 2012.01.24 PHINIA JERSEY HOLDINGS LLC

AI summary

An engine control system, controller, and method for estimating a stopped engine crank angle of an internal combustion engine. Typical crank sensors do not output a reliable crank signal when the engine is about to stop, and do not indicate crank direction which is necessary to determine if engine bounce-back occurs. A crank sensor signal is analyzed as the engine coasts to a stop so that a coast-down model can be adjusted to accurately estimate the stopped engine crank angle. A bounce-back model is also used to estimate an engine bounce-back angle and to make further corrections to the estimated stopped engine crank angle.