Brake Pressure Control via Differential Slip Monitoring
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Solution Overview
Problem
Existing braking systems face challenges in smoothly adjusting brake pressures during external braking demands, leading to undesirable jerks and reduced safety due to sudden brake pressure increases, especially when antilock braking systems intervene.
Innovation Solution
A method that continuously adjusts brake pressures by monitoring differential slip values between axles, using control signals to bring the differential slip closer to a predefined setpoint, thereby optimizing brake pressure distribution and preventing unnecessary antilock interventions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If external braking demand is implemented by directly increasing brake pressure, then demanded vehicle deceleration is achieved, but sudden brake pressure increases cause undesirable jerks and reduced safety
Solution Approach 1:
The brake pressure is dynamically adjusted based on real-time slip measurements. The system continuously monitors wheel slip and adapts the brake pressure profile accordingly, transitioning from a static pressure increase to a dynamic, feedback-controlled pressure adjustment that prevents sudden changes and maintains safety
Solution Approach 2:
The system implements a feedback mechanism by measuring wheel slip and using this information to adjust brake pressure. The slip measurement provides continuous feedback about the braking state, allowing the control system to modify pressure in real-time to avoid jerks and maintain safety during external braking demands
2Reliability
If antilock braking system is activated during external braking demand, then wheel locking is prevented, but unnecessary antilock interventions occur due to sudden brake pressure increases
Solution Approach 1:
The system performs preliminary action by gradually increasing brake pressure before reaching conditions that would trigger antilock intervention. By controlling the pressure rise rate and monitoring slip in advance, the system prevents the sudden pressure spikes that would otherwise cause unnecessary antilock activations during external braking demands
3Force
If brake pressure is adjusted additively for driver demand and external demand, then total braking force is maximized, but brake pressure becomes difficult to control and may cause instability
Solution Approach 1:
The system uses feedback control to manage the combination of driver and external braking demands. By continuously measuring wheel slip and comparing it to desired slip values, the system automatically adjusts the total brake pressure to maintain stability, making the complex additive control transparent to the operator
Solution Approach 2:
The system changes the control parameter from direct brake pressure specification to slip ratio control. By controlling the slip parameter rather than pressure directly, the system simplifies the control task while maintaining the ability to generate total braking force from both driver and external demands
Data Source
AI summary
A method for adjusting brake pressures at pneumatically actuated wheel brakes of a vehicle includes receiving an external braking demand. The method further includes, in response to the received external braking demand, performing, during each of a plurality of computation cycles: (i) ascertaining control signals for pressure control valves of the pneumatically actuated wheel brakes of the vehicle, (ii) continuously ascertaining a differential slip value, wherein the differential slip value is a difference between a slip of two axles of the vehicle and is determined by measuring signals supplied by speed sensors of wheels of the vehicle, (iii) evaluating the differential slip value with respect to a predefined or adjustable setpoint differential slip value, (iv) based on the evaluation of the differential slip value, adapting the ascertained control signals, and (v) releasing the adapted control signals to the pressure control valves.