Trailer Brake Pressure Differential Control
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Solution Overview
Problem
Heavy goods vehicles with trailers and dollies face challenges in maintaining directional stability and effective braking on split friction surfaces due to the limitations of category B ABS systems, which reduce braking force on wheels with high friction, affecting stopping distance and causing brake torque steer.
Innovation Solution
A method for operating a trailer braking system that allows independent control of brake pressure on each side of the trailer, limiting the pressure differential to minimize brake torque steer while maintaining roll-over stability control, by using a brake actuator assembly and an electrical braking controller to manage braking interventions based on vehicle speed and turning conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If category B ABS system reduces braking force on all wheels when one wheel locks, then wheel lock is prevented, but stopping distance increases due to unnecessary reduction on high friction wheels
Solution Approach 1:
The braking system is divided into independent left and right side control groups. When a wheel lock is detected on one side, only the brakes on that same side are modulated, while the other side maintains full braking force. This segmentation allows the system to prevent wheel lock on the affected side without unnecessarily reducing braking force on the high-friction side, thereby maintaining shorter stopping distances.
2Loss of time
If category A ABS system applies braking control only to wheels on the same side as the locked wheel, then stopping distance is improved, but directional stability deteriorates due to brake torque steer
Solution Approach 1:
The system applies different braking control strategies to different sides of the vehicle based on local friction conditions. When a wheel lock is detected, braking force is selectively reduced only on the affected side (local quality change), rather than uniformly across all wheels. This localized adjustment prevents wheel lock while minimizing the torque differential that causes directional instability.
3Manufacturing precision
If independent brake control is provided for each wheel, then braking precision is improved, but system complexity increases due to additional modulators
Solution Approach 1:
The system merges the control functions by grouping wheels into left and right side assemblies, each controlled by a single modulator. This allows independent control of each side while sharing modulators between wheels on the same side, thereby achieving sufficient braking precision without requiring a separate modulator for each individual wheel, thus reducing overall system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach minimizes the impact of brake torque steer on directional stability, allows optimal use of friction during emergency braking, and reduces the risk of roll-over by ensuring balanced braking pressure distribution across the trailer, thereby improving the vehicle's stopping distance and stability on split friction surfaces.
Implementation Method 1
The aim of the ABS is to prevent the vehicle wheels from locking during braking when the frictional forces between the tyre and the road surface are not adequate to transmit the braking force from the tyre to the road.
Implementation Method 2
ABS uses an electronic braking control unit, which receives a wheel speed signal from one or more wheel speed sensors, and at least one modulator to reduce momentarily the braking pressure applied to one or more of the vehicle wheels if wheel lock is detected.
Data Source
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AI summary
A method of operating a braking system for a trailer (16) having at least one axle on which are mounted two ground-engaging wheels (26, 26', 28, 28'), one of which is provided on a first side of the trailer (16) whilst the other is provided on a second side of the trailer (16), each wheel (26, 26', 28, 28') having a brake which is operable independently of the other by means of a brake actuator assembly (26b, 26b', 28b, 28b', 46, 46'), the method including controlling the difference between the brake pressure applied by the brake to the wheel (26, 28)on the first side of the trailer (16) and the brake pressure applied by the brake to the wheel (26', 28') on the second side of the trailer (16) so that it does not exceed a predetermined maximum pressure differential.