Thermal Protection for Automatic Stop-Start Systems
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Solution Overview
Problem
The implementation of automatic stop/start systems for vehicles with manual gearboxes is challenging due to interpreting driver-specific sensor data, leading to difficulties in reliably restarting the heat engine, and the system may incorrectly initiate restarts resulting in engine stalling and thermal safety activation, causing unavailability.
Innovation Solution
A thermal protection method is implemented by comparing the rotational speed of the electric machine with a speed template, activating thermal protection when the speed remains below a minimum threshold for a cumulative duration, and limiting the machine's operation with a predetermined time delay to prevent overheating and improve system availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermal protection is activated based on a single intrusion of the speed template, then the thermal safety is ensured, but the system availability is reduced due to premature activation
Solution Approach 1:
The patent applies periodic action by requiring multiple successive intrusions of the speed template before activating thermal protection. Instead of a single intrusion triggering immediate thermal safety, the system counts successive intrusions over time, creating a periodic evaluation pattern that distinguishes between temporary speed issues and genuine thermal problems, thereby reducing premature activation while maintaining safety.
Solution Approach 2:
The patent implements preliminary action by introducing a counter that accumulates the number of successive intrusions before thermal protection is activated. This preliminary counting mechanism allows the system to gather sufficient evidence of a genuine thermal problem before taking protective action, preventing premature activation and improving system availability while ensuring reliability when needed.
2Productivity
If the thermal protection is activated more restrictively, then the system availability is improved, but the response time to genuine thermal issues increases
Solution Approach 1:
The patent applies feedback by continuously monitoring the rotational speed and comparing it against the speed template, accumulating intrusion counts in a counter. This feedback mechanism allows the system to adaptively determine when thermal protection should be activated based on the pattern and duration of speed intrusions, balancing responsive protection with avoidance of premature activation.
Solution Approach 2:
The patent implements dynamics by making the thermal protection activation threshold dynamic rather than static. The system adjusts its sensitivity based on the cumulative pattern of speed intrusions, transitioning from a static single-threshold approach to a dynamic multi-condition evaluation that adapts to the specific operational context, thereby optimizing both response time and availability.
3Reliability
If the speed template is applied with a longer cumulative duration threshold, then the false activation is reduced, but the detection sensitivity to genuine thermal issues decreases
Solution Approach 1:
The patent applies parameter changes by adjusting the temporal parameters of the speed template evaluation. Instead of using a fixed single-point-in-time threshold, the system changes the evaluation parameter to a cumulative duration-based threshold, counting the number of successive intrusions over a defined period. This parameter transformation allows the system to distinguish between temporary speed variations and genuine thermal issues, improving both reliability and detection sensitivity.
Data Source
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AI summary
The method involves deciding activation of the thermal protection by an electronic control unit, when the rotation speed (VR) of an electrical machine is lower than predetermined minimum speed set point during cumulative time, where the cumulative time is equal to predetermined threshold decision duration. The operation of the electrical machine e.g. alterno-starter, is limited consecutive to the triggering of the thermal protection. An independent claim is also included for an automatic stop/start system for a heat engine of a motor vehicle.