Cam Angle Sensor Error Handling in Mild Hybrid Start-Up
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Solution Overview
Problem
In mild hybrid systems, errors in cam angle sensors prevent accurate fuel injection timing, leading to engine stall and start-up failure, as existing backup crank logic cannot be used due to the high RPM range exceeded by the Mild Hybrid Starter and Generator (MHSG) beyond the capabilities of the 12V starter motor.
Innovation Solution
A start-up method and apparatus that forcibly decreases the RPM of the MHSG to the available range of a 12V starter motor, allowing the execution of existing backup crank logic for test injection and fuel injection time correction, using a controller to determine engine state and adjust RPM through duty control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the MHSG is used for start-up, then the engine can achieve higher starting RPM (up to 1200 rpm), but the existing backup crank logic cannot be used when cam angle sensor errors occur because it requires RPM to be maintained at 200-250 rpm
Solution Approach 1:
The system dynamically adjusts the MHSG control mode based on operational conditions. During normal start-up, the MHSG operates in standard mode achieving up to 1200 rpm. When cam angle sensor errors are detected and backup crank logic is activated, the system dynamically transitions the MHSG to a restricted mode that limits RPM to the 200-250 range, enabling compatibility with the backup logic while maintaining the ability to operate at higher speeds when needed
Solution Approach 2:
The invention changes the operational parameters of the MHSG by introducing a restricted RPM range mode. The controller modifies the target RPM parameter from the normal high-speed range (up to 1200 rpm) to a restricted low-speed range (200-250 rpm) when backup crank logic is required, allowing the system to adapt its performance characteristics to match the requirements of different operational modes
2Measurement precision
If the backup crank logic is used to correct fuel injection time, then fuel injection timing can be accurately corrected, but the engine RPM must be maintained at 200-250 rpm which limits the start-up capability
Solution Approach 1:
The system dynamically switches between two operational modes: normal start-up mode where MHSG can reach up to 1200 rpm, and backup crank mode where RPM is restricted to 200-250 rpm for accurate fuel injection timing correction. This dynamic mode switching allows the system to achieve both high starting capability and precise timing correction as needed
Data Source
AI summary
A start-up method of a mild hybrid system determines whether start-up is attempted through an MHSG in accordance with a request for start-up from a driver, compares an engine rpm at the end of cranking with a reference rpm in start-up using the MHSG, determines whether an engine rpm immediately after start-up follows an idle target rpm when the engine rpm at the end of cranking exceeds the reference rpm, checks whether there is an error in a cam angle sensor when poor following in which the engine rpm immediately after start-up does not follow the idle target rpm is generated, forcibly changes an engine state into cranking when the cam angle sensor has an error, and executes an existing backup crank logic that decreases a target rpm of the MHSG and finds out a fuel injection time while performing test injection using a signal from an crank angle sensor.