Electrically Variable Transmission Engine Start Control
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Solution Overview
Problem
Current hybrid electrically variable transmissions face challenges in managing multiple parameters such as clutch, engine, and motor torques, battery power levels, and smooth shifting between gear modes, which affects fuel economy and operational efficiency.
Innovation Solution
An engine start control system comprising a supervisory controller, input speed profiler, constraints evaluator, feedforward controller, and feedback controller to determine and control torque limits, input speed profiles, and motor torques for efficient engine start and stop operations in hybrid electric vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hybrid electrically variable transmission operates in electric mode or hybrid mode with multiple parameters controlled, then fuel economy and operational efficiency are improved, but the complexity of managing clutch, engine and motor torques, battery power levels and smooth shifting between gears increases
Solution Approach 1:
The control system is segmented into distinct functional modules: a supervisory controller that determines torque limits and desired output torque, an input speed profiler that generates speed profiles, a constraints evaluator that manages torque constraints, a feedforward controller that calculates motor torques based on speed profiles, and a feedback controller that adjusts torques based on actual vs. desired speed. This segmentation allows each module to handle specific aspects of the control problem independently, reducing overall system complexity while maintaining comprehensive control over multiple parameters
Solution Approach 2:
The input speed profiler generates desired input speed profiles and accelerations in advance based on the desired output torque and current operating conditions. The feedforward controller uses these pre-calculated profiles to determine the motor torques required to achieve the desired engine start characteristics. This preliminary action allows the system to plan the engine start sequence ahead of time, coordinating multiple parameters smoothly without real-time complexity
2Speed
If the engine is started quickly to improve responsiveness, then the transition time between drive modes is reduced, but the smoothness of the transition and drivability deteriorates
Solution Approach 1:
The system dynamically adjusts the engine start characteristics by modifying the desired input speed profile based on current operating conditions. The feedforward controller calculates motor torques that produce the desired dynamic speed profile, while the feedback controller continuously adjusts these torques to maintain tracking accuracy. This dynamic control allows the engine to start quickly when needed while maintaining smooth torque transitions that preserve drivability
Solution Approach 2:
The feedback controller continuously monitors the actual input speed and compares it to the desired speed profile, generating error signals that adjust the motor torques in real-time. This feedback mechanism ensures that the engine start follows the desired trajectory smoothly, preventing abrupt torque changes that would degrade drivability while still achieving quick start times
3Productivity
If the transmission manages multiple parameters simultaneously including clutch and motor torques and battery power levels, then operational efficiency is improved, but the difficulty of detecting and measuring system state increases
Solution Approach 1:
The supervisory controller serves multiple functions simultaneously: it determines torque limits for both motors, calculates desired output torque based on vehicle operating conditions, generates the optimum engine speed target, and coordinates clutch operation. This multi-functionality reduces the need for separate control algorithms for each parameter, simplifying the overall monitoring and control architecture while maintaining efficient management of all transmission parameters
Data Source
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AI summary
A system and method of controlling first (EMA) and second (EMB)electric motors of a vehicle having an electrically variable transmission during an engine start/stop operation. The system and method determine an input engine speed profile and an input engine acceleration profile based on an optimum engine speed, determine a requested output torque based on a plurality of torque limits and a desired output torque, determine first (TaFF) and second (TbFF) feedforward motor torques based on a requested output torque and the input speed and input acceleration profiles, determine first (TaFB) and second (TbFB) feedback motor torques based on a difference between the input engine speed profile and an actual input engine speed, and using the feedforward and feedback first and second motor torques to controlthe operation of the first and second electric motors when an engine (ICE) is being turned on or off.