Cruise Control Downshift Suppression Using Actual Acceleration
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Solution Overview
Problem
Existing vehicle control systems, such as Adaptive Cruise Control (ACC), often result in unnecessary downshifts during uphill driving or when the actual vehicle speed is insufficient compared to the target speed, leading to drivability issues like shift shock and increased mechanical load on the transmission.
Innovation Solution
A vehicle control device with a downshift suppression control unit that sets a target driving force and suppresses transmission downshifts based on an allowable acceleration threshold, preventing unnecessary downshifts and maintaining the current gear stage when actual acceleration meets or exceeds this threshold, even if the target driving force exceeds the downshift line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission is downshifted to increase actual vehicle speed during cruise control, then the vehicle speed approaches the target speed, but shift shock occurs and drivability deteriorates
Solution Approach 1:
The system changes the parameter used for downshift control from target driving force to actual acceleration. By comparing actual acceleration against a threshold value, the system determines whether downshift is necessary, preventing unnecessary downshifts that cause shift shock while still allowing downshifts when genuinely needed for speed correction.
2Power
If the transmission is downshifted when target driving force exceeds downshift line, then the drive device output increases, but unnecessary downshift occurs causing mechanical load increase
Solution Approach 1:
The system uses feedback control by continuously monitoring actual acceleration and comparing it with the threshold value. This feedback mechanism allows the system to adjust transmission control dynamically, preventing unnecessary downshifts while ensuring adequate power delivery when needed, thereby simplifying the overall control logic.
3Speed
If cruise control increases output to reach target vehicle speed, then the vehicle accelerates appropriately, but the transmission shifts down unnecessarily
Solution Approach 1:
The system replaces the mechanical feedback mechanism (target driving force based on accelerator opening) with an electronic sensor-based measurement of actual acceleration. This substitution provides more accurate and direct feedback about the vehicle's actual motion state, enabling more precise control decisions.
Data Source
AI summary
To effectively improve drivability during travel control, provided is a vehicle control device comprising a travel control unit configured to set a target acceleration of the vehicle based on a target vehicle speed and an actual vehicle speed, and execute a travel control for automatically controlling travel of the vehicle by operating the drive device based on the target acceleration; a shift control unit configured to set a target driving force, and execute a shift control for operating the transmission device based on the target driving force; and a downshift suppression control unit configured to acquire an actual acceleration during execution of the travel control and suppress execution of downshift of the transmission device by the shift control unit based on an acceleration threshold value.