Semi-Trailer Braking Control Using Kingpin Force Feedback

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Solution Overview

Problem

Existing braking systems for trailer vehicles in semi-trailer trucks lack redundancy, making them vulnerable to failures in electrical and pneumatic control lines, which can lead to hazardous situations, especially in autonomous driving scenarios.

Innovation Solution

A method for autonomous control of the trailer's braking system that determines the force acting on the kingpin to calculate the required braking force, allowing the trailer to brake independently by adjusting the braking force based on the quotient of horizontal force and vertical load, eliminating the need for additional control lines and ensuring consistent deceleration across all axles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrical and pneumatic control lines are used to transmit braking requests from towing vehicle to trailer, then braking control can be achieved, but system reliability deteriorates due to vulnerability to failures and interruptions

Engineering Contradiction:
Improvebraking system reliabilityVSAvoidcontrol line complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The trailer's braking system determines the required braking force autonomously by evaluating forces acting on the trailer (horizontal force at kingpin, vertical load at fifth wheel) and calculating the braking force needed to achieve consistent deceleration. The trailer serves itself by generating its own braking control signals based on measured physical quantities, eliminating dependence on external control lines for braking requests.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The braking control function is segmented between the towing vehicle and trailer. Instead of relying on continuous control signals through vulnerable control lines, the trailer具有独立 capability to determine and execute braking actions based on its own sensor measurements and calculations, creating functional independence that improves reliability.

Inventive Principle:
Principle #1Segmentation

2Reliability

If additional electrical and pneumatic control lines are added to enable autonomous trailer braking, then braking independence is improved, but device complexity and failure points increase

Engineering Contradiction:
Improvebraking independenceVSAvoidcontrol line quantity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The trailer braking system independently determines the braking force by measuring horizontal force at the kingpin and vertical load at the fifth wheel, then calculating the required braking force using the formula: braking force = (horizontal force / vertical load) × axle load. This self-service capability achieves braking independence without requiring additional control lines or complex communication infrastructure.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces electrical and pneumatic control line systems with a mechanical sensing and calculation system. By using physical sensors to measure forces and applying mechanical principles (force ratios, deceleration calculations), the system achieves autonomous control without relying on vulnerable electrical/pneumatic signaling infrastructure.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If wireless communication is used to transmit braking requests from towing vehicle to trailer, then control line complexity is reduced, but reliability deteriorates due to susceptibility to communication failures

Engineering Contradiction:
Improvecontrol line quantityVSAvoidcommunication reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The trailer braking system does not rely on wireless communication or any external signaling. Instead, it autonomously determines braking requirements by measuring physical forces (horizontal force at kingpin, vertical load at fifth wheel) and calculating the necessary braking force locally. This eliminates communication reliability concerns entirely while maintaining the benefit of reduced control line complexity.

Inventive Principle:
Principle #25Self-service

4Extent of automation

If the trailer braking force is calculated independently based on kingpin force and fifth wheel load, then autonomous control capability is improved, but measurement precision requirements increase

Engineering Contradiction:
Improveautonomous braking controlVSAvoidforce measurement precision
Core Design Contradiction:
Extent of automationVSMeasurement precision

Solution Approach 1:

The patent uses mechanical force measurement and calculation rather than complex electronic sensing. By measuring horizontal force at the kingpin and vertical load at the fifth wheel, then applying the mechanical relationship (braking force ratio = horizontal force / vertical load), the system achieves autonomous control with relatively simple and robust mechanical sensors that do not require extremely high measurement precision.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP4484231B1Method for the autonomous control of a braking system of a trailer vehicle of a semi-trailer
Publication Date: 2026.03.25 ZF CV SYST GLOBAL GMBH
  • EP4484231B1 patent drawingFigure 1
  • EP4484231B1 patent drawingFigure 2~3
  • EP4484231B1 patent drawingFigure 4

AI summary

The invention relates to a method for the autonomous control of a braking system of a trailer of a semi-trailer truck, in which a force (F_hor) acting on a kingpin (16) of the trailer is determined, and a braking signal for setting a braking force in the trailer is determined based on this force. The braking force is set such that the resulting deceleration of the trailer corresponds to a quotient of the horizontal force (F_hor) acting on the kingpin and a vertical load (F_vert) acting on a fifth wheel plate (15) of a fifth wheel coupling.