Brake Control Unit Interaxle Distribution Index for Jerk-Free Pressure Adjustment
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Solution Overview
Problem
Existing brake systems face challenges in ensuring jerk-free and constant braking behavior when adjusting brake pressures in pressure control mode after an external brake request, leading to reduced braking safety and comfort due to sudden pressure increases and frequent anti-lock braking interventions, especially in vehicles with non-ideal load distribution.
Innovation Solution
The method involves determining interaxle brake distribution indices during normal braking mode and using them to weight control signals in pressure control mode, optimizing axle distribution ratios and preventing unwanted anti-lock braking interventions by quantitatively evaluating differential slip changes over evaluation intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake pressure is adjusted in pressure control mode after an external brake request, then braking safety is improved, but sudden pressure increases cause jerks and reduce braking comfort
Solution Approach 1:
The brake distribution indices are determined during normal braking mode (before pressure control mode activates) and stored in a memory element. This preliminary determination allows the system to have optimal brake force distribution ready when external brake requests occur, preventing sudden pressure increases and jerks while maintaining braking safety.
Solution Approach 2:
The system continuously monitors wheel speeds via speed sensors and calculates slip values to determine when anti-lock braking interventions are needed. This feedback mechanism allows the brake control unit to adjust brake pressure distribution in real-time, preventing wheel lockup while avoiding abrupt pressure changes that cause jerks.
2Speed
If brake distribution is not optimized in pressure control mode, then response time to external brake requests is improved, but unwanted anti-lock braking interventions increase
Solution Approach 1:
The brake distribution indices are determined in advance during normal braking mode and stored for later use. When pressure control mode activates, these pre-determined indices are immediately applied, providing optimal brake force distribution without delay. This eliminates the trade-off between response time and braking stability.
3Power
If full reservoir pressures are present at pressure control valves during external braking, then braking power is improved, but frequent anti-lock braking interventions reduce braking comfort
Solution Approach 1:
The system applies different brake pressures to different axles based on pre-determined brake distribution indices. By optimizing the brake force distribution ratio between axles, the system maintains high braking power where needed while preventing excessive brake force on axles prone to wheel lockup, thereby reducing frequent anti-lock interventions.
Data Source
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AI summary
The invention relates to a method for adjusting brake pressures on pneumatically actuated wheel brakes of a vehicle, to a brake system for carrying out the method, and to a vehicle having such a brake system. In a normal braking mode (18) a brake pressure on the wheel brakes is adjusted depending upon a driver brake request (19). For implementation of driving stability functions, i.e. at least one antilock function, and also for implementation of external brake requests (30) a brake control unit (21) undertakes the adjustment of the brake pressure (P) in a pressure control mode (24). In the normal braking mode (18) the brake control unit (21) continually determines at least one differential slip value (42) as the difference between the slippage values (38) of two wheels or axles of the vehicle (2) and, by evaluation (45) of the change in the differential slip value (42) within an evaluation interval (53, 55), determines an inter-axle brake distribution index (41) for the relevant pair of axles (46). In the pressure control mode (24) the brake control unit (21) uses the inter-axle brake distribution index (41) determined in the normal braking mode (18) for weighting (40) of the control signals (31, 32) for the respective pair of axles (46).