Automatic Transmission Control for Meandering Roads
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Solution Overview
Problem
Existing vehicle automatic transmission control systems struggle to implement downshifts and shift holds at appropriate timings, particularly on non-downhill roads and during continuous deceleration, leading to potential drivability issues and inappropriate shift operations based solely on driver input, regardless of the road environment.
Innovation Solution
A control apparatus for vehicle automatic transmission that includes shift mode switching, downshift determining, brake detecting, deceleration calculating, and vehicle speed detecting means, which calculates a running state estimated value based on accelerator pedal operations and vehicle speed changes to determine optimal downshift timing, allowing for early downshifts on flat roads and during non-sudden deceleration, and uses lateral acceleration averages to decide shift holds, ensuring appropriate drivability and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If downshift is implemented only at sudden deceleration on non-downhill roads, then the conventional control logic is simple, but appropriate downshift and shift hold may not be performed on continuously meandering roads, worsening drivability
Solution Approach 1:
The control apparatus performs preliminary assessment of the running environment (detecting meandering roads through lateral acceleration variations) before deciding on downshift timing. By anticipating the need for downshift on meandering roads rather than waiting for sudden deceleration, the system ensures appropriate shift timing is achieved in advance.
Solution Approach 2:
The system dynamically adjusts downshift determination based on detected running environment characteristics. When meandering roads are detected through lateral acceleration analysis, the downshift logic is adapted to perform early downshift and shift hold, whereas on straight roads the conventional sudden-deceleration-based logic applies.
2Ease of operation
If downshift timing is determined based on accelerator pedal operation variation, then the control responds to driver input, but in violent driving styles downshift occurs at unnecessary timing while in gentle driving styles necessary downshift may be missed
Solution Approach 1:
The control apparatus introduces lateral acceleration as an intermediary parameter between driver input and downshift execution. By detecting meandering road conditions through lateral acceleration variations, the system mediates between the driver's accelerator operations and the actual downshift timing, ensuring shifts occur at appropriate moments regardless of driving style.
Solution Approach 2:
The system adds another dimension (lateral acceleration analysis) to the traditional one-dimensional accelerator-pedal-based control. This dimensional expansion allows the system to distinguish between legitimate downshift requests and unnecessary shifts caused by violent driving styles, improving timing accuracy.
3Speed
If early downshift is implemented in sport running mode, then responsiveness at re-acceleration is improved, but in normal running mode early downshift causes increase in engine revolutions, worsening vibrations, noise, and engine brake
Solution Approach 1:
The control apparatus applies different downshift control characteristics to different running modes. In sport running mode, early downshift is permitted to maximize responsiveness, while in normal running mode, early downshift is suppressed to avoid unnecessary engine revolutions, vibrations, and noise. Each mode receives locally optimized control quality.
Solution Approach 2:
The system dynamically switches between different downshift strategies based on the selected running mode. The downshift determination logic is not fixed but adapts its behavior according to whether sport or normal mode is active, allowing responsiveness when needed and comfort when not required.
Data Source
AI summary
A sport running estimated value LEVELSP obtained by searching a value on a map prepared in advance based on an average values AGYAVE of lateral accelerations GY of a vehicle and on average values of vehicle speed changes is calculated, and a vehicle speed on a shift map is searched based on the sport running estimated value LEVELSP and an estimated value DA of a vehicle gradient, whereby a downshift vehicle speed VA at which a downshift is implemented is calculated. Then, the downshift is implemented in a case where actuation of a brake is detected, deceleration of the vehicle is a predetermined value or more, and a current vehicle speed is a downshift vehicle speed VA or more. In such a way, running on a meandering road, for which the downshift and a subsequent shift hold should be implemented, is sensed appropriately.