Vehicle Driving System Slip Point Calculation
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Solution Overview
Problem
Existing vehicle driving systems face challenges in accurately switching between two-wheel drive (2WD) and all-wheel drive (AWD) modes due to variations in road conditions, leading to potential decreases in vehicle stability and fuel efficiency, as they rely solely on cumulative slipping amounts without considering the coefficient of friction.
Innovation Solution
A vehicle driving system that includes a controller with a slip detector, additive/subtractive slip point calculator, and driving mode switcher, which calculates cumulative slip points based on driving force correlation values to switch between 2WD and AWD modes, preventing unnecessary mode changes and optimizing driving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the driving mode is switched based on cumulative slipping amounts alone, then the switching logic is simple, but the vehicle stability decreases on low friction surfaces
Solution Approach 1:
The patent introduces a new parameter (driving force magnitude) to complement the existing slipping amount parameter. By changing from a single-parameter switching criterion to a multi-parameter criterion, the system can distinguish between different road conditions, thereby improving vehicle stability without significantly increasing system complexity
Solution Approach 2:
The controller acts as an intermediary that processes both slipping amount and driving force information, then determines the appropriate driving mode. This intermediary processing allows the system to make more accurate switching decisions by combining multiple pieces of information rather than relying on slipping amount alone
2Device complexity
If the driving mode is switched based on cumulative slipping amounts alone, then the switching control is simple, but the driving efficiency decreases due to unnecessary AWD maintenance
Solution Approach 1:
By adding driving force magnitude as an additional parameter to the switching criterion, the system can identify when slipping occurs on high-friction surfaces during normal operation. This allows the controller to avoid unnecessary AWD mode activation, thereby improving fuel economy and driving efficiency while keeping the control logic relatively simple
Solution Approach 2:
The system applies a more stringent switching criterion (requiring both slipping amount and driving force thresholds) rather than switching on any slipping event. This partial action approach prevents over-reactivity to minor slipping events, reducing unnecessary mode changes and improving overall driving efficiency
Data Source
AI summary
A vehicle driving system includes a slip detector that detects an occurrence of excess slipping; an additive/subtractive slip point calculator that time-discretely calculates an additive/subtractive slip point, which is an additive slip point or a subtractive slip point, on the basis detection or non-detection of an occurrence of excess slipping; a cumulative slip point calculator that sequentially calculates a cumulative slip point that is a cumulative sum of values of the additive/subtractive slip point; and a driving mode switcher that switches between a two-wheel driving mode and an all-wheel driving mode on the basis of the cumulative slip point. When excess slipping is detected, the additive/subtractive slip point calculator calculates the additive slip point on the basis of a driving force correlation value that correlates to a driving force a driving wheel for which the excess slipping has occurred.