Transmission Clutch Control for Shift Torque Disturbance Reduction
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Solution Overview
Problem
Automatic transmission clutches experience torque disturbances during shifts, leading to unpleasant vehicle vibrations and noise due to unpredictable changes in friction coefficients and slip speeds, which existing control methods fail to adequately address.
Innovation Solution
A method of controlling transmission clutches by calculating open loop and closed loop pressure commands, where the controlled pressure is adjusted based on clutch slip speed and friction coefficient variations, using a combination of open loop and closed loop terms to maintain a target rate of change of slip speed, thereby reducing torque disturbances during the inertia phase of shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If clutch pressure is increased to reduce slip speed during shift, then shift completion is accelerated, but torque disturbances and vibrations increase due to unpredictable friction coefficient changes
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors clutch slip speed and adjusts clutch apply pressure in real-time. The controller calculates the rate of change of slip speed and modifies pressure commands accordingly, creating a feedback mechanism that maintains stable slip speed reduction without causing torque disturbances or vibrations during the shift process.
Solution Approach 2:
The patent dynamically adjusts clutch pressure based on the instantaneous rate of change of slip speed rather than using fixed pressure profiles. The control system modifies pressure commands in real-time according to how quickly slip speed is changing, allowing the system to adapt to varying friction conditions and maintain smooth shift execution without generating harmful torque disturbances.
2Ease of operation
If clutch pressure is dynamically adjusted based on slip speed rate of change, then shift quality is improved, but control system complexity increases
Solution Approach 1:
The control system uses feedback from slip speed sensors to dynamically adjust clutch pressure, improving shift quality by maintaining optimal pressure levels throughout the shift process. The system monitors the rate of change of slip speed and modifies pressure commands accordingly, ensuring smooth transitions while managing control complexity through algorithmic approaches.
Solution Approach 2:
The patent changes the control parameter from fixed pressure profiles to dynamic pressure adjustment based on slip speed rate of change. By using slip speed and its rate of change as controlling parameters, the system achieves improved shift quality while managing complexity through mathematical relationships rather than requiring additional physical components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively minimizes torque disturbances and maintains shift quality by dynamically adjusting clutch pressure, reducing the discomfort and noise caused by sudden changes in output torque, and ensures smooth transitions between gear ratios.
Implementation Method 1
Automatic transmission clutches experience torque disturbances during shifts, leading to unpleasant vehicle vibrations and noise due to unpredictable changes in friction coefficients and slip speeds
Data Source
AI summary
During the inertia phase of a shift, the oncoming clutch is controlled to alleviate shift quality degradation due variability of clutch friction coefficient. The friction coefficient sometimes increases as the slip speed nears zero. The commanded clutch pressure is a sum of an open loop term and a closed loop term. The open loop term decreases as the clutch slip decreases. Thus, when the friction coefficient increases at the end of the inertia phase, the clutch torque remains nearly constant. When the friction coefficient does not increase at the end of the inertia phase, the closed loop term responds to the resulting decreasing rate of slip speed reduction.