Wheel Driving Force Estimation With Slip Angle Stiffness Correction
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Solution Overview
Problem
Existing driving force estimation methods for four-wheel drive vehicles are inadequate in accurately determining the drive state, especially when continuously changing driving force distribution between front and rear wheels, leading to insufficient estimation of wheel drive states.
Innovation Solution
A driving force estimation apparatus that includes a free rolling rotation speed output unit, actual rotation speed detector, slip rate calculation unit, driving force estimation unit, slip angle output unit, and stiffness correction unit, which calculates and corrects slip rates and driving forces for both front and rear wheels based on their actual and free rolling speeds, slip angles, and stiffnesses to accurately estimate driving forces and states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional driving force estimation methods are used in four-wheel drive vehicles, then the system structure remains simple, but the estimation accuracy of wheel drive states becomes insufficient, especially during cornering
Solution Approach 1:
The patent introduces a stiffness correction unit as an intermediary component that adjusts the driving stiffness based on slip angle information. This mediator bridges the gap between simple wheel speed measurements and accurate driving force estimation by incorporating the effects of lateral tire forces during cornering, thereby improving measurement precision without substantially increasing system complexity
Solution Approach 2:
The patent dynamically changes the driving stiffness parameter based on slip angle conditions. When slip angles exceed threshold values (indicating cornering), the stiffness parameter is corrected to reflect reduced longitudinal force capacity. This parameter adaptation allows accurate driving force estimation under varying vehicle operating conditions while maintaining a relatively simple estimation framework
2Adaptability or versatility
If driving force distribution between front and rear wheels is continuously changed, then the vehicle's adaptability to different driving conditions improves, but the accuracy of determining drive state deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the estimated driving forces of front and rear wheels are continuously compared to determine the actual drive state. The slip angle information provides feedback about vehicle dynamics conditions, allowing the system to accurately determine drive state even when driving force distribution is continuously changing. This feedback loop ensures that adaptability does not compromise measurement precision
3Measurement precision
If slip angle information is incorporated to correct driving stiffness, then the estimation accuracy during cornering improves, but the computational complexity increases
Solution Approach 1:
The patent applies partial correction action by only adjusting the driving stiffness parameter when slip angles exceed predetermined thresholds indicative of cornering conditions. Rather than continuously calculating complex tire models, the system applies stiffness correction only when needed (during cornering), thereby improving estimation accuracy during critical maneuvers while minimizing computational complexity during normal straight-line driving
Data Source
AI summary
A driving force estimation apparatus includes a free rolling rotation speed output unit, an actual rotation speed detector, a slip rate calculation unit, a driving force estimation unit, a slip angle output unit, and a stiffness correction unit. The free rolling rotation speed output unit outputs free rolling rotation speeds of front and rear wheels in a free rolling state devoid of a braking or driving force. The slip rate calculation unit calculates slip rates of the front and rear wheels, from the free rolling rotation speeds and actual rotation speeds. The driving force estimation unit estimates driving forces of the front and rear wheels, using driving or braking stiffnesses of the front and rear wheels and the slip rates. The slip angle output unit outputs slip angles of the front and rear wheels. The stiffness correction unit corrects the driving or braking stiffnesses based on the slip angles.