Hybrid DCT Downshift Control for Slope Backward Sliding
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Solution Overview
Problem
In hybrid vehicles with dual clutch transmissions (DCT), downshifting on an uphill slope can cause gear-shifting delays due to excessive motor speed increases, leading to backward sliding as the controller attempts to synchronize motor speed with the desired shift stage input shaft speed, resulting in prolonged gear shifting and increased negative speed.
Innovation Solution
A downshift control method that determines if a downshift is needed on a slope with a predetermined gradient, releases the release-side clutch by reducing torque, compares motor speed with desired shift stage input shaft speed, and adjusts motor torque to synchronize with the desired speed more rapidly, preventing unnecessary motor speed increases and reducing backward sliding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the controller increases motor torque to rapidly synchronize motor speed with desired shift stage input shaft speed, then gear shifting speed is improved, but motor speed excessively increases causing gear-shifting delay and backward sliding
Solution Approach 1:
The controller applies preliminary anti-action by detecting when the vehicle is traveling uphill and the current gear ratio is greater than the desired gear ratio, then preemptively controlling the motor torque to prevent excessive speed increase before it causes backward sliding. The controller limits motor torque in this specific condition rather than allowing rapid synchronization that would cause the vehicle to slide backward.
2Productivity
If the controller performs downshift control to complete gear shifting rapidly, then productivity is improved, but the vehicle slides backward due to excessive motor speed increase
Solution Approach 1:
The controller dynamically adjusts motor torque based on real-time vehicle conditions. When the vehicle is traveling uphill and downshift is needed, the controller initially limits motor torque to prevent backward sliding, then gradually increases torque as the gear shifting progresses and synchronizes motor speed with the desired input shaft speed, completing the shift rapidly without causing harmful backward sliding.
3Ease of operation
If the controller synchronizes motor speed with desired shift stage input shaft speed by increasing motor torque, then gear shifting is completed, but gear-shifting is delayed due to excessive motor speed increase
Solution Approach 1:
The controller performs preliminary action by pre-detecting the uphill condition and the gear ratio relationship before initiating downshift. It prepares the motor torque control strategy in advance, initially limiting torque to prevent excessive speed increase, then transitioning to torque increase mode to complete synchronization, thereby avoiding gear-shifting delay while ensuring smooth completion.
Data Source
AI summary
Disclosed is a downshift control method for a hybrid DCT vehicle. The method includes: determining, by a controller, whether a downshift is desired while a vehicle travels on a slope having equal to or more than a predetermined reference gradient; comparing, by the controller, a motor speed with a desired shift stage input shaft speed, and selectively performing either a forward control step of increasing a motor torque in a forward direction to increase the motor speed in the forward direction or a negative control step of increasing the motor torque in a negative direction to increase the motor speed in the negative direction. Thus, it is possible to reduce the backward sliding of the vehicle by suppressing the motor speed from unnecessarily increasing and rapidly finishing the downshift.