Hybrid Vehicle Launch Control Using Electric Machine Torque
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Solution Overview
Problem
Conventional powershift transmission vehicles face challenges in providing consistent and acceptable vehicle launch performance due to the lack of a torque converter, leading to issues like engine stall, excessive clutch slip, reduced clutch durability, and inconsistent response during vehicle launch conditions, especially in hybrid electric vehicles with multiple propulsion paths and power sources.
Innovation Solution
A control strategy that utilizes additional propulsion paths and torque actuators to improve vehicle launch performance by supporting torque blending, enhancing clutch durability, and reducing clutch load through coordinated control of engine and electric machine torque, applicable to any powershift transmission architecture with wet or dry clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional powershift transmission control is used during vehicle launch, then the transmission can operate with basic clutch engagement, but engine stall and excessive clutch slip occur due to lack of torque converter
Solution Approach 1:
The electric machine acts as an intermediary between the engine and transmission during launch, providing supplemental torque to prevent engine stall and reduce clutch slip. The electric machine responds rapidly to fill torque gaps that would otherwise cause harmful effects during the transient launch condition.
Solution Approach 2:
The control system dynamically changes torque parameters by coordinating engine torque with electric machine torque output. This parameter coordination allows the system to maintain optimal torque delivery during launch, preventing engine stall and excessive clutch slip while improving launch consistency.
2Speed
If high clutch torque capacity is used during vehicle launch, then the desired vehicle response can be achieved, but clutch durability is reduced due to excessive load
Solution Approach 1:
The electric machine provides partial torque during launch, allowing the clutch to operate at lower torque capacity than would be required in a conventional vehicle. This partial action by the electric machine reduces clutch load and extends durability while still achieving the desired vehicle launch response.
Solution Approach 2:
The electric machine serves as a torque intermediary that shares the launch torque demand with the clutch. By providing supplemental torque during the transient launch phase, the electric machine reduces the peak torque burden on the clutch, thereby improving clutch durability without sacrificing launch performance.
3Reliability
If multiple propulsion paths are used in HEV during vehicle launch, then torque blending can improve performance, but control complexity increases due to multiple power sources
Solution Approach 1:
The control system uses feedback from engine torque, electric machine torque, and transmission input torque to dynamically coordinate the multiple propulsion paths. This feedback-based coordination enables effective torque blending across the engine and electric machine, achieving consistent launch performance while managing control complexity through adaptive control strategies.
Data Source
AI summary
A method for controlling a vehicle launch using a transmission having an input, a current gear, an input clutch associated with a target gear and an output, an engine and an electric machine for driving the input, includes the steps of determining a desired magnitude of torque to be produced at the transmission output, producing a predetermined magnitude of torque capacity of the input clutch, operating the engine such that a magnitude of torque at the transmission output is substantially equal to the desired transmission output torque, determining an crankshaft speed error, determining a desired change in torque at the transmission input that will reduce the crankshaft speed error, adjusting a magnitude of torque produced by the first electric machine such that the magnitude of torque at the transmission input is substantially equal to the desired torque at the transmission input, and engaging the input clutch.