Parallel Kinematics Pose Detection Using Reference Markers

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Solution Overview

Problem

Existing methods for determining the pose of parallel kinematics are time-consuming, computationally intensive, and lack accuracy due to sensor limitations and the need for complex reference runs, while external sensors require a large number of devices and limited measuring range, making precise position determination challenging.

Innovation Solution

A parallel kinematic system with a camera and marking area is used, where markings are placed to ensure at least a certain number are always in the camera's field of view, allowing direct pose determination through image analysis without complex numerical methods, detecting influences like misalignment and deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If numerical methods (iterative optimization) are used to determine pose, then measurement precision can be achieved, but computing time and computational intensity increase significantly

Engineering Contradiction:
Improvepose determination accuracyVSAvoidcomputing time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces complex numerical optimization methods with a direct geometric approach using reference markers and camera imaging. Instead of iteratively solving kinematic equations, the system uses marker position detection in images to directly determine pose, substituting computational complexity with optical measurement simplicity.

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

Solution Approach 2:

The patent creates a simplified representation of the kinematic system using reference markers that copy the essential geometric information needed for pose determination. These markers provide a direct visual copy of the platform's position and orientation, eliminating the need for complex calculations while maintaining measurement accuracy.

Inventive Principle:
Principle #26Copying

2Device complexity

If internal sensors are used to measure leg lengths and joint angles, then the system can operate without external equipment, but measurement precision is reduced due to undetected misalignment, deformation, play, and backlash

Engineering Contradiction:
Improvesensor system simplicityVSAvoidpose determination accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces reference markers as an intermediary element that bridges the gap between the physical kinematic system and the measurement system. These markers serve as a mediator that directly reflects the true pose, allowing the camera to detect misalignment, deformation, play, and backlash effects that internal sensors cannot capture.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent substitutes internal mechanical sensors with an optical measurement system using reference markers and a camera. This replacement allows direct observation of the platform's actual position and orientation, capturing real geometric deviations that internal sensors fail to detect due to their inherent limitations in measuring absolute position and orientation.

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

3Measurement precision

If external optical sensors are used to measure pose, then measurement precision improves, but the number of sensors required increases significantly

Engineering Contradiction:
Improvepose determination accuracyVSAvoidnumber of sensors
Core Design Contradiction:
Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent makes a single camera perform multiple functions: it detects reference markers, determines platform position, and measures orientation. Instead of requiring separate sensors for each degree of freedom, one camera system handles all pose measurement tasks through the reference marker framework.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent uses reference markers as information copies that encode pose data. These markers provide a compact visual representation of the platform's state, allowing a single camera to extract multiple pose parameters from the marker images without requiring multiple sensors.

Inventive Principle:
Principle #26Copying

4Measurement precision

If external optical sensors are used, then measurement precision improves, but measuring range is limited due to sensor field of view constraints

Engineering Contradiction:
Improvepose determination accuracyVSAvoidmeasuring range
Core Design Contradiction:
Measurement precisionVSLength of moving object

Solution Approach 1:

The patent divides the marking area into multiple reference markers distributed across a large area. This segmentation allows the camera to maintain a limited field of view while still covering a large measuring range, as multiple markers provide coverage across different spatial regions.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extends the measurement capability by utilizing the spatial distribution of markers in multiple dimensions. By arranging markers across a large area and detecting their positions in the camera image, the system achieves extended measuring range while maintaining precision through the geometric relationships between markers.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 enables high-accuracy, direct pose determination across the robot's working range with a single sensor, eliminating the need for multiple sensors and complex calculations, and allows for precise control of the moving work platform.

Implementation Method 1

a camera (110) and a marking area (150) with mutually distinguishable markings (e.g., AprilTags), wherein the camera (110) is configured to observe the marking area (150) in different poses

Methodology Applied
Scientific EffectLight reflection: Reflection

Data Source

PatentEP4437304B1Pose determination in parallel kinematics systems with reference markers
Publication Date: 2025.12.31 PHYSIK INSTRUMENTE (PI) GMBH & CO KG
  • EP4437304B1 patent drawingFigure 1a~1b
  • EP4437304B1 patent drawingFigure 2a~2b
  • EP4437304B1 patent drawingFigure 3~6

AI summary

The present invention relates to parallel kinematics systems and to a method for producing parallel kinematics systems. A parallel kinematics system according to the invention comprises mutually distinguishable markings which are fixed in a marking region on the parallel kinematics system. The marking region is a region of the kinematics system which is moved together with the pose of the kinematics system. According to one aspect of the present invention, the markings are fixed at a spacing in one direction, which spacing ensures that n markings can be seen completely in the direction at all times, and the pose of the parallel kinematics system can be determined based on an image which is recorded by the camera and contains at least n markings in the direction. According to another aspect of the present invention, the markings are fixed at a spacing in one direction, which spacing ensures that n or more markings can be seen completely in the direction, the markings are fixed in different planes, and the pose of the parallel kinematics system can be determined based on an image which is recorded by the camera and contains at least n arbitrary markings in the direction.