Series Hybrid Engine Control for NOx and Aftertreatment Temperature
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Solution Overview
Problem
Series hybrid and range extender powertrain configurations face challenges in minimizing exhaust emissions and optimizing fuel economy, particularly due to the decoupling of the engine from the traction system, which can lead to increased NOx emissions and ineffective aftertreatment temperatures.
Innovation Solution
A controller is implemented in the series or range extender hybrid vehicle drive system that takes input data on power requests, state of charge, exhaust gas oxygen levels, and aftertreatment temperatures to adjust engine and motor/generator torque delivery, optimizing emissions and power output while maintaining independence from traction power requests, using strategies such as capping engine power, maintaining aftertreatment temperatures, and limiting power changes to reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is decoupled from the traction system in series hybrid architecture, then fuel economy and emissions can be improved through independent engine operation, but NOx emissions increase and aftertreatment effectiveness decreases
Solution Approach 1:
The system dynamically adjusts engine operating parameters (torque, speed, power output) based on real-time feedback from oxygen sensors and temperature sensors in the aftertreatment system. The controller continuously modifies engine operation to maintain aftertreatment effectiveness while optimizing fuel economy, rather than using fixed operating modes.
Solution Approach 2:
The system implements closed-loop feedback control using oxygen sensors (pre-cat, mid-cat, post-cat) and temperature sensors to monitor aftertreatment system state. This feedback is used by the controller to adjust engine torque and power output, ensuring emissions are minimized while maintaining fuel efficiency. The feedback mechanism allows the system to respond to changing conditions and maintain optimal operation.
2Power
If engine power is increased to meet power demands, then traction performance is improved, but exhaust emissions increase and aftertreatment temperature control becomes difficult
Solution Approach 1:
The system segments the power delivery function between the combustion engine and the motor/generator. The engine operates independently to generate electrical power, while the motor/generator provides the necessary torque for traction. This segmentation allows the engine to operate in optimized emission modes while the motor/generator handles peak power demands, reducing overall emissions while maintaining traction performance.
Solution Approach 2:
The system changes engine operating parameters (torque, speed, power output) dynamically based on power demands and aftertreatment system state. When high power is needed, the engine adjusts its parameters while the controller coordinates with the motor/generator to meet the total power demand, thereby managing emissions while satisfying traction requirements.
3Loss of energy
If the engine operates with high independence from traction power requests, then fuel economy is improved, but aftertreatment temperature remains ineffective and emissions are not minimized
Solution Approach 1:
The system uses temperature sensors positioned in the aftertreatment system to provide real-time feedback on thermal state. This feedback enables the controller to adjust engine operation to maintain temperatures within the effective range for emissions control, ensuring aftertreatment reliability while preserving fuel economy benefits from independent engine operation.
Solution Approach 2:
The system takes preliminary action by pre-heating the aftertreatment system or maintaining minimum engine power levels to ensure the aftertreatment reaches and maintains effective operating temperature before full independent engine operation begins. This preliminary action prevents temperature inefficiency while allowing subsequent fuel-efficient operation.
4Object-generated harmful factors
If engine torque and speed are adjusted to minimize emissions, then exhaust emissions are reduced, but tracking error of state of charge increases
Solution Approach 1:
The system dynamically balances two control objectives: emissions minimization and state of charge tracking. The controller continuously adjusts engine torque and speed based on real-time conditions, switching between emission-optimized modes and charge-management modes as needed. This dynamic adjustment allows the system to minimize emissions while maintaining acceptable state of charge tracking accuracy.
Solution Approach 2:
The system changes engine operating parameters (torque, speed, power output) based on the priority between emissions control and state of charge management. When emissions are the primary concern, parameters are adjusted to minimize exhaust output. When state of charge tracking error becomes significant, parameters are adjusted to recharge the battery, thereby balancing both objectives through parameter modulation.
Data Source
AI summary
A series or range extender hybrid vehicle drive system is disclosed having a combustion engine with an exhaust aftertreatment device, a motor/generator, an electrical energy storage and a traction motor. The traction motor is driven using power from the energy storage and/or the engine. A controller of the system is operable to receive input data representative of a requested power from the drive system, a state of charge indication of the electrical energy storage and at least one of the oxygen level in exhaust gas from the engine and temperature in the exhaust gas. The controller is also operable to provide output signals to control torque and speed of the engine and motor/generator to minimize exhaust emissions output and any tracking error of the state of charge of the energy storage to a desired target.