Automatic Transmission Shift Blocking to Eliminate Gear Hunting
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Solution Overview
Problem
Automatic transmissions in vehicles experience a phenomenon known as 'pumping' due to transient gear changes that do not allow sufficient torque transmission, leading to oscillations between gears, which affects vehicle performance and comfort, especially under conditions like steep inclines or strong winds.
Innovation Solution
Implementing a control strategy that freezes the transmission state setpoint during gear changes if the vehicle's speed decreases or if the required performance level exceeds a threshold, and maintaining this freeze until the vehicle regains speed, thereby preventing return to the initial gear and avoiding oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission allows gear changes based on speed thresholds, then the transmission can adapt to varying vehicle speeds, but the vehicle may experience pumping oscillations between gears when resistive forces cause speed to drop below the threshold
Solution Approach 1:
The control method applies a preliminary anti-action by detecting when a gear change is in progress and resistive forces are high, then proactively blocking the reverse gear change before it can occur. This prevents the pumping oscillation from developing in the first place, rather than reacting after the oscillation begins.
Solution Approach 2:
The system uses feedback by continuously monitoring vehicle speed, gear change status, and resistive force levels. When the feedback indicates a gear change is underway and speed drops below the threshold during high resistive conditions, the control logic triggers a block on reverse gear changes to prevent oscillation.
2Productivity
If the transmission completes a gear change even when speed decreases, then the gear change process is simple and fast, but the vehicle may require returning to the initial gear causing oscillation and performance penalty
Solution Approach 1:
The system takes preliminary action by setting a flag during the gear change process that blocks reverse gear changes before they can be initiated. This preliminary blocking action ensures that even if speed drops below the threshold, the transmission will not attempt to return to the previous gear, thereby preventing oscillation while maintaining the forward gear change.
3Stability of the object's composition
If the transmission blocks gear changes when performance threshold is exceeded, then pumping is prevented, but the transmission cannot respond to legitimate acceleration needs
Solution Approach 1:
The control method dynamically adjusts gear change blocking based on real-time conditions. The block is applied selectively only when a gear change is in progress and resistive forces are high, not during normal operation. This dynamic approach maintains stability when needed while preserving adaptability for legitimate acceleration demands under normal conditions.
Data Source
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AI summary
Method for eliminating hunting in an automatic transmission of a vehicle propulsion unit, characterized in that a status setpoint (GBX_TG_RAW) for the drivetrain and imposed on the transmission can be set to a status target (GBX_TG_CS) by: - a first "block" request during the realization of this setpoint by the transmission (BLK_REQ_DRG_SHF), if the speed of travel of the vehicle decreases during this realization, while the level of performance required of the propulsion unit is above a defined threshold, or - by a second "block" request (BLK REQ AFTR SHF) at the end of realization of the setpoint (GBX_TG_CS), if the speed of travel of the vehicle at this instant is lower than its speed of travel during the initial change of setpoint, and if the level of performance required of the propulsion unit (PWT_SP) is still above a defined threshold(PWT_SP_THD).