Hill Start Assist Abnormality Detection
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Solution Overview
Problem
Conventional hill start assist systems fail to accurately determine the vehicle's intended drive direction and drive force, leading to unexpected vehicle behavior and impaired handling when shift position switches detect abnormal conditions, resulting in inappropriate brake activation or deactivation.
Innovation Solution
A vehicle hill start assist system that includes a brake device, an inclined road determining unit, a brake control unit for maintaining a stationary state, and an abnormality determining unit to assess drive direction and drive force abnormalities, adjusting the braking force reduction time based on these assessments to prevent unexpected vehicle behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HSA determines shift position based on switch signals when abnormalities occur, then the system can operate under abnormal conditions, but the vehicle may exhibit unexpected behavior and impaired handling
Solution Approach 1:
The hill start assist control is dynamically adjusted based on the determined drive direction. When an abnormality is detected, the system determines the drive direction from available signals (engine rotation direction, transmission output shaft rotation direction) and applies brake maintaining control only in the appropriate direction, rather than using a fixed control strategy. This dynamic adaptation resolves the contradiction by maintaining reliability through continued operation while preserving handling through context-appropriate control.
Solution Approach 2:
The system changes the control parameters of the brake maintaining control based on the determined drive direction. When driving forward is determined, brake maintaining control is applied; when driving rearward is determined, brake maintaining control is not applied. This parameter change approach allows the system to operate reliably under abnormal conditions while adapting the control behavior to match the actual driving intent, thereby preventing handling impairment.
2Stability of the object's composition
If the HSA maintains brake pressure for a longer duration to ensure vehicle stationary state, then the vehicle stability is improved, but the response time for abnormality detection and correction is extended
Solution Approach 1:
The system performs preliminary determination of the drive direction using available signals (engine rotation direction, transmission output shaft rotation direction, shift lever position) before applying brake maintaining control. This preliminary action allows the system to quickly identify the abnormal condition and determine the appropriate control response, reducing the time loss while still maintaining vehicle stability through targeted brake pressure application.
Solution Approach 2:
The system continuously monitors drive direction determination results and adjusts brake maintaining control accordingly. When the determined drive direction matches the intended direction, brake pressure is maintained; when there is a mismatch indicating an abnormality, the control is adjusted or cancelled. This feedback mechanism ensures vehicle stability is maintained only when appropriate, while enabling quick response to and correction of abnormal conditions.
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
The system effectively prevents unexpected vehicle behavior and improves handling by maintaining a stationary state for a shorter duration when abnormalities are detected, ensuring the vehicle starts as intended, even under abnormal conditions, thereby enhancing safety and convenience.
Implementation Method 1
The inclination of the road surface is typically detected by using a fore and aft G sensor
Data Source
AI summary
Disclosed is a hill start assist for a vehicle capable of suppressing vehicle movement contrary to driver's expectations and capable of improving driving feel even if the magnitude of detected values regarding the driving direction of driving wheels or that of driving force of the driving wheels are abnormal. Specifically disclosed is a hill start assist (1) for a vehicle comprising an ECU (20) that includes a detection state determining unit (25) that determines the detection state of a shift lever position switch (14) and a retention control unit (26) that performs retention control in which a reduction in braking force of a braking device (5) is suppressed when the operation of a brake pedal (2) is stopped. The retention control unit (26) further includes a first retention control performing unit (27) selected when determination results of the detection state determining unit (25) are normal and a second retention control performing unit (29) selected when the determination results of the detection state determining unit (25) are abnormal. The second retention control performing unit (29) performs the retention control in a manner such that the vehicle is retained in a stop state for a second stop retention time (T2) shorter than a first stop retention time (T1) set by the first retention control performing unit (27).