Hybrid Vehicle Deceleration Control for Consistent Overrun Response
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Solution Overview
Problem
Hybrid vehicles face challenges in providing consistent deceleration feedback to drivers, especially when the battery is fully charged, as the motor control system prevents the motor from acting as a generator, and existing methods do not account for external vehicle conditions like gradient and transmission speed ratio.
Innovation Solution
A method that determines a target deceleration based on vehicle speed, transmission speed ratio, gradient, and vehicle mode, and adjusts engine and motor torque to maintain consistent deceleration by continually measuring real-time deceleration and commanding necessary negative torque, with dynamic control of deceleration torque to mimic engine-only mode, using electronic controllers and deceleration maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the motor acts as a generator to provide deceleration torque when the battery is fully charged, then regenerative braking is enabled, but the motor control system prevents the motor from acting as a generator, so normal deceleration cannot be achieved
Solution Approach 1:
The system dynamically adjusts the deceleration torque parameter based on battery state of charge. When the battery is fully charged, the control system modifies the target deceleration torque to account for the inability of the motor to provide regenerative braking, ensuring consistent deceleration feedback to the driver while preventing energy recovery attempts that would fail
Solution Approach 2:
The control system continuously monitors battery state of charge and adjusts the deceleration torque command in real-time. When the battery reaches full charge, the system detects this condition and modifies the motor torque command to maintain expected deceleration characteristics, providing feedback-based adaptation to maintain driver expectation consistency
2Device complexity
If the deceleration torque is based solely on engine friction and pumping losses, then the calculation is simple, but external vehicle conditions such as gradient, speed ratio, and vehicle mass are not accounted for, causing inconsistent deceleration profiles
Solution Approach 1:
The system transitions from a static deceleration torque model (based only on engine friction) to a dynamic model that continuously adapts to changing vehicle conditions. The target deceleration torque is recalculated based on real-time inputs including gradient, transmission speed ratio, and vehicle mass, allowing the control system to maintain consistent deceleration profiles across varying operating conditions
Solution Approach 2:
The control system modifies the deceleration torque parameter by incorporating multiple vehicle condition parameters (gradient, speed ratio, mass) into the torque calculation. This parameter expansion allows the system to compensate for external conditions that affect deceleration, maintaining consistency without requiring overly complex hardware modifications
3Adaptability or versatility
If the motor provides only a portion of the negative torque with the engine providing the remainder via a slipping clutch, then torque distribution flexibility is achieved, but consistent deceleration becomes more difficult to provide
Solution Approach 1:
The control system uses feedback from the actual deceleration rate and battery state of charge to dynamically adjust the torque distribution between the motor and engine. When the battery is full, the system reduces motor regenerative torque and compensates with engine braking torque, continuously monitoring to maintain the target deceleration profile despite the changing torque source mix
Solution Approach 2:
The system dynamically changes the torque contribution parameter of each power source based on battery state of charge. When the battery is fully charged, the motor's regenerative torque contribution is reduced or eliminated, and the engine's braking torque contribution is increased to compensate, maintaining the overall deceleration target while adapting to energy storage constraints
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
Ensures a consistent overrun response for drivers across various conditions, utilizing engine braking when regenerative braking is limited, and dynamically adjusts deceleration torque to match internal combustion engine behavior, providing smooth transitions and optimized fuel economy.
Implementation Method 1
the motor acting as a generator... the motor may be driven by the wheels (regenerative braking)
Implementation Method 2
an internal combustion engine and an electric motor each capable of driving vehicle wheels
Implementation Method 3
determine empirically the deceleration torque applied by the engine (the torque to overcome friction and pumping losses)
Data Source
Figure 1~2
Figure 3
AI summary
A hybrid electric vehicle is capable of direct drive by internal combustion engine, electric motor, or both. In order to provide a consistent overrun response, a torque controller determines an appropriate deceleration characteristic according to, for example, transmission speed ratio, vehicle gradient and vehicle mass, and commands the electric motor and the engine to contribute a negative torque which meets the required deceleration characteristic. A 'tip' function modifies the characteristic in the event of a change commanded by the vehicle driver, for example a change of speed ratio.