Trailer Hitch Angle Calculation Using Corrected Camera Coordinates

Solution Overview

Problem

Existing hitch angle calculation methods, such as those described in PTL 1, may inaccurately determine the hitch angle due to errors in visual features that are not corrected during coordinate system transformation, leading to inappropriate calculations.

Innovation Solution

A hitch angle calculation device and method that involves acquiring images from a camera mounted on a vehicle towing a trailer, transforming coordinates to a world coordinate system, calculating average distances between trailer ends and the hitch ball, removing coordinates that do not meet specific conditions, and correcting coordinates in images to align with calculated averages, thereby ensuring accurate hitch angle determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If coordinate system transformation is performed on images to calculate hitch angle, then the hitch angle can be determined from camera images, but visual features including errors remain after transformation leading to inaccurate hitch angle calculation

Engineering Contradiction:

Improvehitch angle calculation accuracyVSAvoidvisual feature accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by performing coordinate system transformation and error correction on visual features before calculating the hitch angle. The system transforms coordinates from image space to world coordinate system, identifies and corrects errors in visual features (such as incorrect identification of trailer corners or hitch ball position) before these erroneous features are used in the final angle calculation, thereby ensuring accurate results.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary error correction mechanism between coordinate transformation and hitch angle calculation. This intermediary step includes filtering visual features based on geometric constraints (e.g., verifying that transformed coordinates actually represent trailer corners or hitch ball), removing outliers, and validating feature positions before they are used in the final calculation, thus mediating between raw visual data and reliable angle measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If visual features are used directly without correction after coordinate transformation, then the calculation process is simple, but the hitch angle may be calculated inappropriately

Engineering Contradiction:

Improvecalculation process complexityVSAvoidhitch angle accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by performing coordinate system transformation and error correction on visual features before calculating the hitch angle. The system transforms coordinates from image space to world coordinate system, identifies and corrects errors in visual features (such as incorrect identification of trailer corners or hitch ball position) before these erroneous features are used in the final angle calculation, thereby ensuring accurate results.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary error correction mechanism between coordinate transformation and hitch angle calculation. This intermediary step includes filtering visual features based on geometric constraints (e.g., verifying that transformed coordinates actually represent trailer corners or hitch ball), removing outliers, and validating feature positions before they are used in the final calculation, thus mediating between raw visual data and reliable angle measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250375989A1Hitch angle calculation device, hitch angle calculation method, and non-transitory recording medium

Publication Date: 2025.12.11 TOYOTA JIDOSHA KK

AI summary

A hitch angle calculation device calculates coordinates of left and right lower ends of a trailer and hitch ball included in an image shot by a vehicle-mounted camera after calibration travel of a vehicle towing the trailer via a tow bar, transforms them to coordinates in a world coordinate system, calculates distance between the left lower end and the hitch ball and distance between the right lower end and the hitch ball, corrects the coordinate of the left lower end so that the distance between the left lower end and the hitch ball is equal to an average value, corrects the coordinate of the right lower end so that the distance between the right lower end and the hitch ball is equal to the average value, and calculates a hitch angle of the trailer based on the corrected coordinates of the left and the right lower ends.