Automatic Transmission Downshift Control for NVH Reduction
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Solution Overview
Problem
Conventional automatic transmission control systems suffer from slow downshift times and noise, vibration, and harshness (NVH) caused by clutch engagement during downshifts, which affect the shift quality of vehicles.
Innovation Solution
A control system that adjusts the engine speed request by determining target speeds and torque outputs for the torque generating system, using a transmission control module and a torque generating system control module to optimize downshifts by setting target speeds within acceptable limits and applying torque multipliers based on current and target gear ratios, thereby improving shift quality and reducing NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional automatic transmission control systems execute downshifts, then the transmission gear ratio changes from lower to higher, but the downshift time becomes slow and NVH increases
Solution Approach 1:
The system performs preliminary actions by determining target engine speeds and torque outputs before the actual downshift occurs. The transmission control module calculates the target speed for the torque generating system and the torque generating system control module prepares the target torque output based on current and target gear ratios, enabling faster execution of the downshift command.
Solution Approach 2:
The system changes parameters by dynamically adjusting the target speed and torque output of the torque generating system during the downshift process. The control modules modify engine speed requests and torque outputs based on the current gear ratio and target gear ratio, optimizing the downshift characteristics to reduce time and NVH.
2Ease of operation
If conventional automatic transmission control systems execute downshifts, then the gear ratio changes, but noise, vibration, and harshness (NVH) increase
Solution Approach 1:
The system uses feedback by continuously monitoring the current speed of the torque generating system and comparing it with the target speed. The control modules adjust the target torque output based on the difference between current and target conditions, ensuring smooth downshift execution that minimizes NVH while maintaining good shift quality.
Solution Approach 2:
The system optimizes shift quality by dynamically changing the torque output parameter during downshift. The torque generating system control module calculates the target torque output based on current gear ratio and target gear ratio, adjusting engine torque to match the optimal values for smooth gear transitions and reduce NVH.
Data Source
AI summary
A vehicle control system and method utilize a transmission control module configured to generate a first target speed for a torque generating system for executing a downshift of an automatic transmission and a torque generating system control module configured to determine a second target speed for the torque generating system for executing the downshift of the automatic transmission, determine upper and lower target speed limits for the torque generating system for executing the downshift of the automatic transmission, based on the first and second target speeds and the upper and lower target speed limits, determine a final target speed for the torque generating system for executing the downshift of the automatic transmission, determine a target torque output for the torque generating system based on a current speed of and the final target speed for the torque generating system, and control the torque generating system based on the target torque output.