Automatic Transmission Gear Shift Control Under Derated Conditions
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Solution Overview
Problem
Existing strategies for controlling gear ratio changes in electronically controlled automatic transmissions often result in gear hunting events due to insufficient power during shifts, especially under derated operating conditions such as high altitude or low fuel pressure.
Innovation Solution
A method that identifies upcoming gear ratio changes and adjusts the estimated power output based on current engine speed and derated operating conditions, setting a gear evaluation identifier to either allow or prevent the gear change depending on whether the estimated power output meets or exceeds the current power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gear ratio changes are made according to predetermined shift points, then power management during shifts is improved, but gear hunting events occur when power is insufficient under derated conditions
Solution Approach 1:
The patent applies dynamics by transitioning from static predetermined shift points to dynamic shift point determination. The electronic controller continuously monitors actual engine operating conditions (engine speed, torque, derated conditions) and adjusts shift points in real-time. This allows the transmission to adapt gear ratio changes to the currently available power, preventing gear hunting events that occur when fixed shift points are used under derated conditions.
Solution Approach 2:
The patent implements parameter changes by modifying shift points based on actual engine performance parameters. Instead of using fixed shift points, the system adjusts shift points according to measured engine speed, torque output, and derated operating conditions. This parameter-based adaptation ensures that gear ratio changes occur only when sufficient power is available, resolving the contradiction between power management and gear hunting prevention.
2Reliability
If shift points are adjusted dynamically based on engine conditions, then gear hunting is reduced, but control system complexity increases
Solution Approach 1:
The patent applies feedback by implementing a closed-loop control system where the electronic controller continuously monitors engine operating conditions (speed, torque, derated states) and uses this feedback to dynamically adjust shift points. The controller receives feedback from sensors, processes the information against stored engine performance data, and modifies gear ratio change timing accordingly. This feedback mechanism reduces gear hunting while maintaining manageable complexity through algorithmic decision-making based on pre-stored performance characteristics.
Solution Approach 2:
The system implements self-service by using pre-stored engine performance data and characteristics that enable the controller to autonomously determine appropriate shift points without complex real-time calculations. The engine's own performance characteristics, when stored during manufacturing, serve the control function, allowing the system to self-adjust to varying conditions using inherent engine data rather than requiring external intervention or overly complex control algorithms.
Data Source
AI summary
A method of controlling an automatic transmission of a machine includes a step of identifying an upcoming gear ratio change from a current gear ratio to a proposed gear ratio. An estimated power output value, based on the proposed gear ratio and a current engine speed, is determined. The estimated power output value is adjusted based on a derated operating condition. If the estimated power output value is greater than or equal to a current power output value, a gear evaluation identifier is set to a first value. If the estimated power output value is less than the current power output value, the gear evaluation identifier is set to a second value.