Grade-Based Anti-Hunt Timer for Automatic Transmission Shift Control
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Solution Overview
Problem
Existing transmission systems experience gear hunting due to abrupt gear ratio changes, leading to rapid repeated shifts between adjacent gears, causing operator discomfort and unnecessary wear, and existing solutions like shift timers can result in engine lugging or over-speeding when actual machine conditions require gear changes.
Innovation Solution
A grade-based anti-hunt shift control system that sets an anti-hunt timer to prevent shifts back to a previous gear and a secondary timer to allow downshifts when significant load or grade changes are detected, ensuring optimal gear operation and preventing premature clearing of the anti-hunt timer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a shift timer is used to prevent rapid shifts between adjacent gears, then gear hunting is prevented, but engine lugging or over-speeding occurs when legitimate gear ratio changes are required
Solution Approach 1:
The system changes the parameter of timer override based on detected operating conditions. When a change in operating conditions is detected (such as load changes, grade changes, or vehicle speed changes), the controller overrides the anti-hunt timer to allow necessary gear shifts. This resolves the contradiction by making the timer's restrictive effect conditional rather than absolute, maintaining stability during normal operation while enabling adaptability when needed.
2Adaptability or versatility
If the anti-hunt timer is overridden frequently to allow gear shifts, then engine lugging is prevented, but lower frequency shift oscillations occur
Solution Approach 1:
The system introduces an intermediary condition-based override mechanism between the anti-hunt timer and gear shift execution. The controller acts as an intermediary that selectively permits or blocks timer overrides based on detected operating conditions. This prevents direct and frequent overrides while still allowing necessary shifts, thus reducing shift oscillations while maintaining engine performance.
3Stability of the object's composition
If a lock-out timer is set after upshift to prevent subsequent shifts, then high-frequency hunting is prevented, but legitimate gear ratio changes are blocked
Solution Approach 1:
The system makes the lock-out timer dynamic by allowing condition-based overrides. Rather than a fixed, immutable timer, the anti-hunt timer can be overridden when specific operating conditions are detected (such as significant load changes, grade changes, or vehicle speed changes). This dynamic approach maintains the timer's stabilizing effect during normal operation while ensuring reliability when legitimate gear changes are required by actual driving conditions.
Data Source
AI summary
A system and method are provided for grade-based anti-hunt shift control of an automatic transmission powering a machine. A shift controller determines a recommended gear in which to operate the transmission and sets an anti-hunt timer upon recommending a shift from a first gear to a second gear. The anti-hunt timer prevents a subsequent shift back to the first gear while the anti-hunt timer is running. A grade-based controller is configured to track machine operation and to determine when the machine operational factors change such that an estimated steady state gear differs from the second gear. When such a change is encountered, the grade-based controller clears the anti-hunt timer and sets a secondary timer. The clearing of the anti-hunt timer allows a downshift to accommodate the detected grade while the setting of the secondary timer prevents a subsequent clearing of the anti-hunt timer while the secondary timer is running.