Hybrid Vehicle Shifting Control Method for Stability
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Solution Overview
Problem
Hybrid vehicle shifting control methods face instability and shifting shock when transitioning to lower gear stages, particularly at low vehicle speeds and varying road gradients, due to insufficient inertia phase and excessive clutch engagement.
Innovation Solution
A shifting control method that dualizes the strategy based on road gradient and vehicle speed, involving a controller to release the clutch, synchronize motor speed with the input shaft speed, and engage the clutch, with motor torque control to minimize slipping and ensure smooth transitions by performing a torque phase without an inertia phase at low gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power off down-shifting is made from second stage to first stage at low vehicle speed (2-3 KPH), then fuel efficiency is improved by minimizing inertia phase, but shifting stability is reduced due to small difference between release and applying input shaft speeds
Solution Approach 1:
The control method changes the shifting strategy parameters based on vehicle speed and road gradient conditions. At low speeds with small shaft speed differences, it performs only torque phase without inertia phase to save fuel. At higher speeds with large differences, it performs both inertia and torque phases to ensure stability, thus adapting parameters to operating conditions
Solution Approach 2:
The system dynamically adjusts the shifting control strategy based on real-time vehicle speed and road gradient measurements. The controller selects between different shifting modes (inertia phase only, torque phase only, or both phases) depending on the current operating conditions, making the system flexible and adaptive
2Power
If 1-stage gear ratio is required at relatively high vehicle speed for tip-in preparation on inclined roads, then driving force readiness is improved, but shifting shock occurs due to excessively long inertia phase and excessive clutch engagement
Solution Approach 1:
The control method adjusts the inertia phase duration parameter based on vehicle speed and gradient conditions. At high speeds on inclines where tip-in preparation is needed, it performs both inertia and torque phases. At lower speeds or on flat/downhill roads, it performs only torque phase, thus optimizing the balance between power readiness and shock reduction
Solution Approach 2:
The system applies partial action by performing only the necessary phase (inertia or torque) depending on conditions, rather than always performing both phases. This prevents excessive clutch engagement and reduces shifting shock while still achieving the required driving force readiness
Data Source
AI summary
A shifting control method for hybrid vehicles may include shifting request determining, by a controller, of determining whether power off down shifting to a lowest stage is requested, clutch releasing, by the controller, of controlling a release clutch to be released, when it is determined that a gradient of a road exceeds a reference value and a vehicle speed exceeds a reference vehicle speed when the shifting is requested as the shifting request determination result, synchronizing, by the controller, of controlling a motor speed to be synchronized with an applying input shaft speed, and clutch engaging, by the controller, of controlling an applying clutch to be engaged.