Hybrid Vehicle Torque Control Transitions
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Solution Overview
Problem
Hybrid vehicle powertrains face inefficiencies due to frequent changes in operating points caused by the limited state of charge of the high voltage traction battery, leading to inefficient use of battery power and fuel during driving maneuvers.
Innovation Solution
A vehicle control system that operates the electric machine and engine based on lookup tables calibrated for transient and steady-state modes, minimizing instantaneous and energy losses respectively, and transitions smoothly between these modes based on driver demand and powertrain speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the powertrain operates at the most efficient operating point by adding or subtracting electric machine torque, then system efficiency is improved, but the limited state of charge of the battery causes frequent changes in operating points leading to overall inefficiency
Solution Approach 1:
The control system dynamically switches between transient and steady-state operating modes based on real-time detection of driver demand and powertrain speed conditions. The system adapts its operating point selection strategy by transitioning from transient lookup tables to steady-state lookup tables when steady-state conditions are detected, optimizing energy management for each operational context
Solution Approach 2:
The system changes the operational parameters by selecting different lookup tables (transient vs. steady-state) based on detected operating conditions. The steady-state lookup table is specifically calibrated to minimize energy losses based on battery state of charge, allowing the system to maintain optimal operating points for extended durations
2Use of energy by moving object
If the system frequently changes operating points to maintain efficiency, then instantaneous efficiency is improved, but overall fuel efficiency deteriorates due to limited battery capacity
Solution Approach 1:
The system dynamically adjusts its operating strategy by detecting when steady-state conditions occur and switching to a mode that prioritizes minimizing overall energy losses. This dynamic adaptation reduces unnecessary operating point changes while maintaining efficiency during transient conditions
Solution Approach 2:
The system changes the optimization parameter from instantaneous efficiency during transient operation to overall energy loss minimization during steady-state operation. The steady-state lookup table is specifically calibrated to minimize energy losses based on battery state of charge, preventing wasteful frequent transitions
3Device complexity
If the system uses a single operating mode lookup table, then system complexity is reduced, but the ability to optimize for both transient and steady-state conditions deteriorates
Solution Approach 1:
The control system is segmented into two distinct operational modes with separate lookup tables: transient operation mode and steady-state operation mode. Each lookup table is optimized for its specific operational context, with the steady-state table calibrated to minimize energy losses based on battery state of charge. The system detects and switches between modes based on driver demand and powertrain speed conditions
Solution Approach 2:
The dual lookup table system provides multi-functionality by handling both transient and steady-state optimization requirements within a single control architecture. The system universally applies the appropriate lookup table based on detected conditions, achieving both transient responsiveness and steady-state efficiency optimization without requiring separate control systems
Data Source
AI summary
A system and method for controlling a hybrid vehicle having an engine, a traction motor, and an automatic step-ratio transmission having a plurality of selectable discrete gear ratios include operating the electric machine to provide output torque associated with a first operating point selected based on driver demand torque and a current powertrain speed during transient operation, operating the electric machine to provide an output torque associated with a second operating point selected based on the driver demand torque and the current powertrain speed during steady state operation, and controlling the engine torque based on a difference between the driver demand torque and the electric machine torque.