PID Torque Phase Control for Power Downshift Synchronization
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Solution Overview
Problem
Existing automatic transmission systems face challenges in smoothly transitioning through the torque phase of a power downshift, requiring complex calibration and lacking effective self-correction mechanisms for clutch synchronization.
Innovation Solution
Implementing proportional-integral-derivative (PID)-based closed-loop feedback control during the near-sync boost state of the torque phase, in conjunction with open-loop feed-forward clutch pressure control, to achieve and maintain clutch synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex calibration methods are used for clutch synchronization control, then synchronization precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a closed-loop feedback control system using PID (Proportional-Integral-Derivative) control during the near-sync boost state. The system continuously monitors the speed difference between oncoming and offgoing clutches and adjusts the clutch pressure command in real-time to achieve precise synchronization. This feedback mechanism eliminates the need for complex pre-calibration by dynamically correcting synchronization errors during the actual shift event.
Solution Approach 2:
The control system performs self-adjustment during the torque phase by automatically detecting when clutches are near synchronization and activating PID control only during this specific near-sync boost state. The system serves itself by identifying the critical synchronization moment and applying corrective pressure adjustments without requiring external calibration input, thereby simplifying the overall control architecture.
2Device complexity
If open-loop feed-forward control is used for clutch pressure, then device complexity is reduced, but synchronization precision deteriorates
Solution Approach 1:
The patent segments the clutch control process into distinct phases: an initial open-loop feed-forward phase for basic pressure application, and a closed-loop PID phase for precise synchronization. By dividing the control strategy into these segments and activating PID control only during the critical near-sync boost state, the system achieves high synchronization precision without requiring complex control throughout the entire shift event, thus maintaining relative simplicity.
Solution Approach 2:
The control system dynamically transitions from open-loop feed-forward control to closed-loop PID control based on the real-time state of the clutches. When the speed difference between clutches indicates the near-sync boost state, the system dynamically activates PID control with appropriate gain values. This dynamic adaptation allows the system to use simple control when precision is less critical and complex control only when synchronization precision is most needed.
Data Source
AI summary
A method for controlling the torque phase of a clutch-to-clutch power downshift in a vehicle includes determining, during a near-sync boost (NSB) state of the power downshift, a synchronization speed. The method includes estimating, via a controller, a feed-forward clutch pressure that holds a speed of the turbine at the synchronous speed, and then ramping a clutch pressure command to the oncoming clutch to the calculated feed-forward clutch pressure. Closed-loop proportional-integral-derivative (PID) control is initiated over the clutch pressure command during the NSB phase in response to a predetermined PID activation event. A vehicle includes an engine, transmission, torque converter, and a controller. The controller has a processor and memory on which instructions embodying the above method are recorded. Execution of the instructions by the processor causes the controller to execute the method.