Vehicle Slip Ratio Control with Velocity-Based Torque Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional vehicle control systems that fix the upper limit of the target slip ratio degrade vehicle running performance and stability, as they fail to adapt to varying vehicle states and road conditions, leading to inadequate frictional or lateral forces.
Innovation Solution
A vehicle control device that calculates a target slip ratio and sets an upper limit value based on vehicle velocity, limiting the slip ratio to enhance driving performance and stability by dynamically controlling driving torque to achieve the target slip ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit value of the target slip ratio is fixed, then the wheel slip is controlled within a safe range, but the running performance and stability are degraded
Solution Approach 1:
The upper limit value of the target slip ratio is changed from a fixed constant to a dynamic value that varies with vehicle velocity. The arithmetic unit calculates the upper limit value based on the current vehicle velocity, allowing the system to adapt to different running conditions. This resolves the contradiction by making the control parameter flexible rather than rigid, improving running performance while maintaining reliability.
Solution Approach 2:
The system changes the parameter (upper limit value of target slip ratio) based on vehicle velocity conditions. At different velocity ranges, different upper limit values are applied: a first upper limit value for lower velocities and a second upper limit value for higher velocities. This parameter adaptation allows the system to optimize running performance for each velocity condition while preventing excessive slip.
2Reliability
If the upper limit value of the target slip ratio is made small, then the wheel slip is restrained, but the frictional force between the wheel and road surface decreases
Solution Approach 1:
The system applies different upper limit values of the target slip ratio depending on the vehicle velocity. At lower velocities, a smaller upper limit value is used to restrain wheel slip and maintain adequate frictional force. At higher velocities, a larger upper limit value is permitted to maintain running performance. This velocity-dependent parameter change resolves the contradiction by adapting the slip restraint level to the current operating conditions.
3Force
If the upper limit value of the target slip ratio is made large, then the driving force is improved, but the lateral force acting on the wheel decreases
Solution Approach 1:
The system changes the upper limit value of the target slip ratio based on vehicle velocity to balance driving force and vehicle stability. At higher velocities, a larger upper limit value is applied to improve driving force and running performance. At lower velocities, a smaller upper limit value is used to maintain adequate lateral force and vehicle body posture stability. This dynamic parameter adjustment resolves the contradiction between driving force and stability.
Data Source
AI summary
The vehicle control device (10) includes: an arithmetic unit (11) that calculates a target slip ratio (y) serving as a target value of a slip ratio (λ) of the wheel (5); a limiting unit (12) that sets an upper limit value (ymax) of the target slip ratio (y), the upper limit value (ymax) being based on at least a vehicle velocity (V) of the vehicle (1), and limits the target slip ratio (y) calculated by the arithmetic unit (11) to a value equal to or less than the upper limit value (ymax); and a controlling unit (13) that controls driving torque of the vehicle (1) such that a wheel velocity that achieves the target slip ratio (y) limited by the limiting unit (12) is obtained.