Vehicle Body Speed Calculation for Anti-Skid Control
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Solution Overview
Problem
In four-wheel drive vehicles, existing anti-skid control systems fail to accurately calculate vehicle body speed due to acceleration slip, leading to inappropriate braking torque adjustments and potential deceleration issues.
Innovation Solution
An anti-skid control device that uses wheel speed sensors and a controller to differentiate between acceleration slip and true vehicle speed, selectively switching between reduction and increase modes of braking torque based on wheel speed comparisons to accurately estimate vehicle body speed and execute suitable anti-skid control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the vehicle body speed is calculated based on the maximum wheel speed, then the calculation is simple, but the accuracy deteriorates due to acceleration slip
Solution Approach 1:
The patent dynamically switches between maximum wheel speed and minimum wheel speed based on the detected acceleration slip condition. When acceleration slip is detected, the system switches to using minimum wheel speed for calculation; when no acceleration slip is present, it uses maximum wheel speed. This dynamic adaptation resolves the contradiction by selecting the appropriate calculation method based on real-time vehicle operating conditions.
Solution Approach 2:
The patent changes the parameter used for vehicle body speed calculation from a fixed maximum wheel speed to a conditional selection between maximum and minimum wheel speeds. By monitoring acceleration slip and adjusting the selection criterion, the system maintains calculation simplicity while improving accuracy under acceleration conditions.
2Speed
If the braking torque is reduced based on inaccurate vehicle body speed, then the control response is fast, but the deceleration performance deteriorates
Solution Approach 1:
The patent introduces feedback by continuously monitoring wheel speed changes to detect acceleration slip conditions. Based on this feedback, the system adjusts the vehicle body speed calculation method in real-time, ensuring that braking torque control is based on accurate speed information. This prevents premature braking torque reduction and maintains effective deceleration performance.
Solution Approach 2:
The patent performs preliminary detection of acceleration slip conditions before executing braking torque control. By detecting the acceleration slip state in advance and adjusting the speed calculation method accordingly, the system ensures that subsequent braking torque adjustments are based on accurate vehicle body speed, preventing inappropriate control actions.
Data Source
AI summary
Anti-skid control is performed by switching between a reduction mode for reducing braking torque and an increase mode for increasing braking torque based on a comparison between four wheel speeds and vehicle body speed. A controller calculates wheel accelerations based on wheel speeds and includes a control mode condition where the reduction mode is selected at each wheel and a wheel acceleration condition where each wheel acceleration is within a predetermined value range. If a state in which the control mode condition and the wheel acceleration condition are simultaneously satisfied is maintained over a predetermined time period, the controller determines that a residual state is satisfied. When the residual state is not satisfied, the controller calculates vehicle body speed based on the maximum value of the wheel speeds, whereas when the residual state is satisfied, the controller calculates vehicle body speed based on the minimum value of the wheel speeds.