Transmission Clutch Control Switching Open-Loop Closed-Loop Phases
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Solution Overview
Problem
Conventional transmissions experience delays during clutch-to-clutch shifts due to inadequate control of clutch pressure changes, particularly during high torque upshifts, where rapid pressurization is required to initiate speed ratio changes effectively.
Innovation Solution
A method that switches between open-loop and closed-loop pressure control logic based on detected clutch responses and shift phases, using a set of clutch fill parameters to optimize clutch pressure control, detecting end-of-fill events, and adjusting fill parameters to prevent overfill or underfill conditions, and correcting pressure anomalies to ensure precise pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional open-loop pressure control is used during clutch fill phase, then the control system is simple, but the clutch pressurization speed is insufficient and shift delays occur
Solution Approach 1:
The patent applies dynamics by switching between open-loop and closed-loop control modes based on the clutch fill phase detection. During the active fill phase, closed-loop control is activated to rapidly increase clutch pressure, while transitioning to open-loop control after fill completion. This dynamic control mode adjustment enables fast pressurization when needed while maintaining system simplicity otherwise, directly resolving the contradiction between pressurization speed and system complexity.
Solution Approach 2:
The patent changes the control parameter from a fixed open-loop mode to a variable mode that switches between open-loop and closed-loop control based on detected clutch response and shift phase. This parameter change allows the system to optimize pressurization speed by using closed-loop control during the critical fill phase while avoiding continuous complexity, thus resolving the speed-complexity contradiction.
2Measurement precision
If closed-loop pressure control is used continuously, then the clutch pressure control precision is high, but the system response delay increases and shift quality deteriorates
Solution Approach 1:
The patent segments the clutch control process into distinct phases: active fill phase and post-fill phase. During the active fill phase, closed-loop control is used for precise pressure control. After detecting the end-of-fill event, the system transitions to open-loop control. This segmentation allows precise control only when necessary, reducing overall shift execution time while maintaining pressure control precision during the critical fill phase, thus resolving the precision-time contradiction.
Solution Approach 2:
The patent detects the active fill phase and initiates closed-loop control in advance during this phase to ensure precise pressure control is established before the clutch engagement is critical. Once the fill phase is complete, the system switches to open-loop control. This preliminary application of closed-loop control during the fill phase ensures precision is achieved when needed most, while avoiding continuous closed-loop operation that would increase overall shift time.
3Speed
If rapid pressurization is applied during high torque upshift, then the shift speed increases, but pressure instability and overfill conditions occur
Solution Approach 1:
The patent implements feedback by continuously monitoring clutch pressure and detecting the active fill phase. When overfill conditions are detected through the feedback mechanism, the system responds by switching from closed-loop to open-loop control and adjusting the commanded clutch pressure. This feedback-based control adjustment stabilizes pressure during rapid pressurization, resolving the contradiction between shift speed and pressure stability.
Solution Approach 2:
The patent applies dynamics by dynamically adjusting the control mode and commanded pressure based on real-time detection of fill phase and pressure conditions. During rapid pressurization, if overfill is detected, the system dynamically switches control modes and adjusts pressure commands to stabilize the system. This dynamic adaptation enables fast shifting while preventing pressure instability, resolving the speed-stability contradiction.
Data Source
AI summary
A method for controlling a clutch assembly includes controlling an actual clutch fill pressure using open-loop pressure controls when an active fill phase is detected, and using closed-loop pressure controls when the active fill phase is complete or when an overfill condition is detected. The method supplies the actual clutch pressure according to a second set of open-loop pressure controls when a step in commanded clutch pressure is detected. The method monitors a fill pressure and time during the step, and applies the clutch pressure according to the closed-loop pressure controls when either value equals a corresponding threshold value. A clutch assembly has a piston for compressing clutch disks to initiate a shift event, an algorithm for controlling the shift event, and a sensor for determining an actual clutch pressure during the shift phases. The algorithm switches between closed-loop and open-loop pressure controls in response to different shift phases.