Mild Hybrid Starter Control via Battery SOC and Temperature
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Solution Overview
Problem
Mild hybrid vehicles face challenges in maintaining starting performance and stability, particularly due to variations in ambient air temperature and state of charge of the high voltage battery, which affect the efficient operation of the starter-generator and starter systems.
Innovation Solution
A method for controlling a mild hybrid vehicle that determines the state of charge and ambient air temperature to decide whether to use the starter-generator or the starter alone to start the engine, with specific current levels applied based on these conditions to ensure stable engine starting, using a controller to manage the operation of the starter and starter-generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the starter-generator is used to start the engine, then the starting performance is improved, but the state of charge of the high voltage battery may be insufficient in cold conditions
Solution Approach 1:
The patent combines the starter-generator system (powered by high voltage battery) and the traditional starter system (powered by low voltage battery) into a unified starting system. The controller intelligently selects or combines both starters based on operating conditions, allowing the systems to work together to resolve the contradiction between starting reliability and battery state of charge constraints.
Solution Approach 2:
The controller changes the operating parameters by selecting different starting modes (high voltage starter-generator only, low voltage starter only, or both together) based on the state of charge of the high voltage battery and ambient temperature conditions. This parameter switching allows optimal starting performance while protecting against battery depletion.
2Reliability
If the starter is used alone in cold conditions, then the starting stability is maintained, but the starting performance may be insufficient when high starting torque is required
Solution Approach 1:
The controller enables both the starter-generator and traditional starter to operate simultaneously when high starting torque is required. By merging the output of both starting systems, the patent achieves both high power output and stable starting performance, overcoming the limitations of using either system alone.
3Ease of operation
If the starter-generator operates without temperature consideration, then the starting process is simplified, but the starting stability deteriorates in cold ambient conditions
Solution Approach 1:
The controller changes the starting strategy based on ambient temperature parameters. In cold conditions, the system switches to using the low voltage starter or combines both starters to ensure stable starting. This parameter-based adaptation maintains starting stability while managing the complexity of the starting process automatically.
4Power
If high current is applied to the starter in cold conditions, then the starting performance is improved, but the energy consumption increases
Solution Approach 1:
The system dynamically adjusts the current distribution between the high voltage battery (powering starter-generator) and low voltage battery (powering traditional starter) based on real-time conditions. This dynamic current management optimizes starting power output while minimizing total energy consumption by utilizing the most efficient power source for each operating condition.
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
Improves the starting stability and state of charge of the low voltage battery by optimizing the use of both the starter-generator and starter based on temperature and SOC conditions, enhancing the overall starting performance of the vehicle.
Implementation Method 1
a starter-generator (or a mild hybrid starter and generator) 30 configured to start the engine 205 using power from a first battery 40
Implementation Method 2
a starter 34 configured to start the engine 205 using power from a second battery 42
Implementation Method 3
The starter-generator may be connected to the crankshaft via a belt
Data Source
AI summary
A method for controlling a mild hybrid vehicle is disclosed. The method includes determining, by a controller, whether a state of charge (SOC) of a first battery that supplies electric power to a starter-generator exceeds a reference value. The method further includes operating, by the controller, the starter-generator and a starter that is separate from the starter-generator and receives electric power from a second battery at a voltage lower than that of the first battery. A combustion engine of the mild hybrid vehicle is started using the starter-generator and the starter when it is determined that the state of charge of the first battery exceeds the reference value and it is determined that an ambient air temperature of the engine exceeds a temperature reference value.