DCT Creep Control via Feed-Forward Torque
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Solution Overview
Problem
Dual clutch transmissions (DCTs) without torque converters face challenges in providing consistent and smooth vehicle launch performance and vehicle creep, as they lack the predictive control offered by torque converters.
Innovation Solution
A method for controlling vehicle creep by operating the input clutch at a desired torque capacity, using feed-forward engine torque to minimize engine speed fluctuations and achieve desired clutch slip, simulating the torque converter function and limiting energy transmission through a torque-based approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a dual clutch transmission is used without a torque converter, then the transmission structure is simplified and shift speed is improved, but vehicle creep performance becomes inconsistent and difficult to control
Solution Approach 1:
The control system performs preliminary actions by predicting driver intent based on brake pedal position and other sensor data before the actual launch occurs. The system pre-calculates the required clutch torque and engine torque adjustments to achieve smooth creep and launch performance, eliminating the need for a torque converter while maintaining predictable vehicle behavior.
Solution Approach 2:
The system continuously monitors vehicle speed, clutch slip, engine speed, and brake pedal position, using this feedback to dynamically adjust clutch torque capacity and engine torque. This closed-loop control ensures consistent creep performance and smooth launches despite the absence of a torque converter, resolving the reliability issue while maintaining structural simplicity.
2Speed
If clutch torque capacity is increased to provide vehicle creep, then vehicle speed is improved, but engine speed dips or flares occur
Solution Approach 1:
The system applies preliminary anti-action by using feed-forward control to anticipate the engine speed dip that will occur when clutch torque is increased. The control system pre-adjusts engine torque and idle speed in opposition to the expected speed drop, canceling out the destabilizing effect before it occurs. This allows the clutch to transmit sufficient torque for vehicle creep while maintaining stable engine speed throughout the launch process.
Data Source
AI summary
A method for controlling creep in a vehicle having no transmission torque converter, includes operating an input clutch of the transmission at a desired clutch torque capacity, using a feed-forward engine torque to minimize the impact on the engine speed when additional load on the engine occurs from increasing the clutch torque capacity, producing a desired clutch slip by controlling engine idle speed, and achieving a desired vehicle speed by controlling the input clutch torque capacity.