Vehicle Deceleration Control Using Regenerative Braking and Downshift Logic
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Solution Overview
Problem
During vehicle deceleration under driving assistance control, existing control devices experience increased noise and vibration (NV) due to engine speed increases and busy shifting, leading to decreased drivability.
Innovation Solution
A control device with an electronic control unit that restricts downshift of the automatic transmission during gentle deceleration and allows downshift during steep deceleration, using regenerative braking and engine braking to manage deceleration amounts and minimize NV and busy shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If downshift is executed during deceleration to increase deceleration amount through engine braking, then deceleration performance is improved, but noise and vibration (NV) increases and drivability decreases
Solution Approach 1:
The control device changes the control parameter (downshift restriction flag) based on the driving state (manual vs. driving assistance control). During driving assistance control, the system prohibits downshift to maintain low engine speed and reduce NV, while during manual control, downshift is allowed for better deceleration performance. This parameter change resolves the contradiction by adapting the transmission control strategy to the specific driving context.
2Speed
If downshift is repeatedly executed during deceleration to achieve demanded deceleration amount, then deceleration control is improved, but busy shifting occurs and drivability decreases
Solution Approach 1:
The control device performs preliminary action by setting the downshift restriction flag before busy shifting can occur. When driving assistance control is detected, the system proactively prohibits downshift, preventing the condition that would lead to busy shifting. This preliminary restriction stabilizes the shifting pattern and eliminates the oscillation between upshift and downshift that would otherwise occur.
3Loss of energy
If regenerative braking is used during deceleration under driving assistance control, then energy recovery is improved, but deceleration amount may be insufficient without downshift
Solution Approach 1:
The control device dynamically adjusts the deceleration strategy based on the driving state. During driving assistance control, the system prioritizes regenerative braking with downshift prohibition, accepting lower deceleration amounts for the benefit of energy recovery and NV reduction. During manual control, the system dynamically switches to engine braking with downshift for maximum deceleration performance. This dynamic adaptation resolves the contradiction between energy recovery and deceleration amount.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses NV and busy shifting during gentle deceleration while achieving desired deceleration amounts, maintaining drivability and efficiently controlling vehicle speed under driving assistance control.
Implementation Method 1
execute regenerative braking using the rotator
Implementation Method 2
engine braking applied by friction of the engine
Data Source
AI summary
A control device for a vehicle includes an electronic control unit configured to: execute driving assistance control for driving the vehicle at least by automatically controlling a speed irrespective of a driving operation of a driver; execute regenerative braking using a rotator at a time of deceleration during travel under the driving assistance control, and to restrict downshift of an automatic transmission when a demanded deceleration amount for the vehicle is equal to or lower than a predetermined deceleration amount; and execute the regenerative braking using the rotator at the time of deceleration during the travel under the driving assistance control, and not to restrict the downshift when the demanded deceleration amount is higher than the predetermined deceleration amount.