ABS Braking Pressure Control for Stable Vehicle Deceleration
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Solution Overview
Problem
Existing ABS braking systems in commercial vehicles experience restless and uncertain braking behavior due to early activation of the ABS control, leading to unpleasant braking experiences, especially at high target vehicle decelerations, and inadequate load-dependent brake pressure distribution.
Innovation Solution
A method for electronically controlling vehicle deceleration by adjusting brake pressures on the front and rear axles based on actual vehicle deceleration, differential slip, and load conditions, using maximum and minimum deceleration characteristics to regulate brake pressure and prevent premature wheel locking, while ensuring comfortable and safe braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target differential slip is increased at high vehicle target deceleration to ensure more sensitive transition to ABS control, then the ABS control activates earlier, but the braking behavior becomes more unstable and unsafe
Solution Approach 1:
The patent changes the parameter of target differential slip from a constant value to a variable that depends on vehicle deceleration. At low deceleration, a higher target differential slip (e.g., 2%) is used for sensitive ABS activation. At high deceleration, the target differential slip is reduced (e.g., to 0.5% or lower) to prevent premature ABS activation and maintain stable braking behavior. This dynamic parameter adjustment resolves the contradiction between sensitivity and stability.
2Reliability
If brake pressure on rear wheel brakes is limited based on difference in wheel speeds or brake slip, then rear wheel lock-up is prevented, but the braking behavior appears unstable and unpleasant above maximum deceleration
Solution Approach 1:
The patent introduces dynamic adaptation of the maximum deceleration threshold based on vehicle load conditions. The system determines whether the vehicle is loaded or unloaded and adjusts the maximum deceleration value accordingly. For loaded vehicles, a higher maximum deceleration is permitted, while for unloaded vehicles, a lower threshold is applied. This dynamic adjustment smooths the braking behavior above maximum deceleration and eliminates the unstable feel, while still preventing rear wheel lock-up through differential slip control.
3Measurement precision
If mechanical displacement sensor or pressure sensor is used to measure load, then accurate load-dependent brake pressure limitation is achieved, but the system complexity increases
Solution Approach 1:
The patent enables the braking system to determine its own load condition using existing sensors already present in the vehicle (wheel speed sensors, brake slip sensors). By analyzing the difference in wheel speeds or brake slip between axles, the system infers the load condition without requiring additional mechanical displacement sensors or pressure sensors. This self-service approach achieves accurate load-dependent brake pressure limitation while avoiding increased system complexity.
Data Source
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AI summary
The invention relates to a method for controlling a deceleration of a vehicle (200) with an ABS braking system (100), comprising at least the following steps: detecting a setpoint vehicle deceleration predetermined by the driver, determining a maximum deceleration and a minimum deceleration, in each case as a function of the detected setpoint vehicle deceleration, detecting an actual vehicle deceleration and controlling a braking pressure (pHA, pVA) on wheel brakes (5, 6, 7, 8) of a first and a second vehicle axle (HA, VA) as a function of the detected actual vehicle deceleration by controlling ABS brake valves (11, 12, 13, 14, 21, 22, 23, 24) such that the braking pressure (pHA, pVA) on the wheel brakes (5, 6, 7, 8) of the first and second vehicle axle (HA, VA) is increased if the actual vehicle deceleration is smaller than the minimum deceleration for reaching a minimum braking effect, and the braking pressure (pHA, pVA) on the wheel brakes (5, 6, 7, 8) of the first and second vehicle axle (HA, VA) is limited if the actual vehicle deceleration is greater than the maximum deceleration for limiting the braking effect of the first and second vehicle axle (HA, VA), and the braking pressure (pHA, pVA) on the wheel brakes (5, 6, 7, 8) of the second vehicle axle (HA, VA) is additionally controlled as a function of a detected actual differential slip if the actual vehicle deceleration is smaller than the maximum deceleration and greater than the minimum deceleration, the actual differential slip indicating the difference in a rotational behavior of the first vehicle axle (HA, VA) with respect to the second vehicle axle (HA, VA).