Hybrid Vehicle Controller Optimizing Drive Mode Transitions
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Solution Overview
Problem
Hybrid vehicles face challenges in maintaining fuel economy and drivability due to limited gear ratios and battery state-of-charge conditions, leading to inefficient drive mode transitions and potential battery over-discharge.
Innovation Solution
A controller that determines engine start based on battery conditions, driver intention, and vehicle running conditions, using fuzzy reasoning to switch between EV and series drive modes, ensuring optimal fuel consumption and preventing battery overcharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the drive mode is changed from EV drive mode to engine drive mode based on demanded torque, then the vehicle can meet high torque requirements, but the gear ratio is limited and fuel economy deteriorates
Solution Approach 1:
The patent introduces a series drive mode as an intermediary solution between EV drive mode and engine drive mode. In this mode, the engine drives a generator to produce electricity, which then powers the electric motor. This intermediary approach allows the engine to operate at optimal fuel-efficient points while still meeting high torque demands through the electric motor, avoiding the fuel economy deterioration associated with direct engine drive mode.
2Power
If the drive mode is changed based on demanded torque, then high power requirements can be met, but the battery may be discharged excessively when SOC and temperature conditions are unfavorable
Solution Approach 1:
The patent dynamically adjusts the available uppermost outputting value of the battery based on real-time SOC and temperature conditions. When SOC is low or temperature is unfavorable, the system automatically reduces the maximum allowable battery output to prevent excessive discharge. This dynamic adjustment ensures the battery operates within safe parameters while still allowing the vehicle to meet power requirements through coordinated engine-generator operation in series drive mode.
3Reliability
If the engine is started to meet demanded electric power, then the battery can be protected from over-discharge, but unnecessary engine operations may occur
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors demanded electric power, battery SOC, temperature, and engine operation status. The controller compares the demanded power against the available battery output and adjusts engine operation accordingly. When the demanded power exceeds battery capability, the engine starts to generate electricity; when demand is met by the battery alone, the engine remains off. This feedback loop prevents unnecessary engine operations while ensuring battery protection.
4Use of energy by moving object
If fuzzy reasoning is used to determine engine start, then drivability and fuel economy can be optimized, but the control system complexity increases
Solution Approach 1:
The patent employs fuzzy logic control that processes multiple input parameters (SOC, temperature, demanded power, accelerator opening) and transforms them into a decision output for engine start/stop. The fuzzy reasoning system uses predefined membership functions and rule bases to handle the non-linear relationships between parameters, optimizing fuel consumption without requiring complex mechanical modifications. The computational complexity is managed through efficient fuzzy inference algorithms implemented in the controller.
Data Source
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AI summary
There is provided a controller for a hybrid vehicle which can improve fuel consumption performance and driveability. A controller for a hybrid vehicle which can run in an EV drive mode in which an electric motor 101 is driven by electric power of a battery 113 only and a series drive mode in which the electric motor 101 is driven by electric power generated by a generator 107 using power of an engine 109 includes a demanded driving force calculation unit for calculating a demanded driving force for the electric motor 101 based on vehicle speed and accelerator pedal opening, a demanded electric power calculation unit for calculating a demanded electric power demanded of the electric motor 101 based on the demanded driving force and a revolution speed of the electric motor 101, an available uppermost outputting value setting unit for setting an available uppermost outputting value for the battery 113 based on the conditions of the battery 103, and an engine starting determination unit for determining on the starting of the engine 109 based on the demanded electric power demanded of the electric motor 101. The engine starting determination unit starts the engine 109 so that the vehicle runs in the series drive mode when the demanded electric power demanded of the electric motor 101 exceeds the available uppermost outputting value.