Reference Marker Pose Detection for Parallel Kinematics
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Solution Overview
Problem
Determining the pose of parallel kinematic systems, such as hexapods, is challenging due to the need for time-consuming numerical methods and the inability to account for influences like offset, deformation, and backlash in existing sensor-based approaches, which often result in low accuracy and require complex setups.
Innovation Solution
Attaching reference markers to the parallel kinematic system ensures that at least one marker is always in the camera's field of view, allowing direct pose determination through image analysis without numerical methods, thereby detecting influences like offset and deformation, and using a single camera for 6 degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If numerical methods are used to determine pose, then pose determination is possible for parallel kinematic systems, but the process is time-consuming and computationally intensive
Solution Approach 1:
The patent replaces numerical computation methods with an optical measurement system. Instead of using iterative optimization algorithms to calculate pose from leg lengths and joint angles, the system uses a camera to capture images of reference markers on the movable platform, directly obtaining pose information through image processing. This substitution of mechanical/computational methods with optical measurement eliminates the time-consuming numerical calculations while maintaining accuracy.
2Measurement precision
If internal sensors are used to measure leg lengths and joint angles, then pose information can be obtained, but influences like offset, deformation, play and backlash cannot be detected
Solution Approach 1:
The patent introduces reference markers as intermediaries between the movable platform and the camera. These markers serve as a direct optical reference that is not affected by mechanical influences such as offset, deformation, play, or backlash. By capturing images of these markers and processing them to determine pose, the system obtains accurate position and orientation information without being compromised by the mechanical imperfections that affect internal sensors. The markers act as a pure optical reference that transcends mechanical limitations.
3Measurement precision
If multiple external optical sensors are used to measure all degrees of freedom, then measurement coverage is improved, but the number of sensors increases and measuring range is restricted
Solution Approach 1:
The patent merges the functions of multiple sensors into a single camera system. Instead of using separate sensors for different degrees of freedom, the system uses one camera to capture images of reference markers that encode information about all six degrees of freedom (three positional and three orientational parameters). The image processing algorithm extracts all this information from a single image, effectively combining the measurement capabilities of multiple sensors into one device while maintaining full measurement coverage.
4Measurement precision
If photogrammetry is used with multiple images from different positions, then 3D scan accuracy is improved, but the region captured is large and accuracy decreases
Solution Approach 1:
The patent uses reference markers as simplified optical copies or representations of the movable platform's pose. Instead of capturing the entire platform and performing complex 3D reconstruction from multiple images, the system uses small, distinctive markers that directly encode pose information. The camera captures images of these markers, and the reference marker system provides a direct mapping between image coordinates and pose parameters, eliminating the need for large-field-of-view imaging and complex photogrammetrical reconstruction.
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 method provides high accuracy and simplifies pose determination by eliminating the need for complex sensor alignment and numerical calculations, enabling precise position regulation of the movable work platform.
Implementation Method 1
When using 6D measurement technology by way of photogrammetry
Implementation Method 2
a marking region with mutually distinguishable markings, where the camera is configured to observe the marking region
Data Source
AI summary
A parallel kinematic system comprises mutually distinguishable markings which are attached in a marking region to the parallel kinematic system. The marking region is a region of the kinematic system that moves along with the pose of the kinematic system. The markings can be attached in a direction at a distance that ensures that n markings are always fully visible in the direction, and the pose of the parallel kinematic system can be determined based on an image that is captured by the camera and contains at least n markings in the direction. The markings can be attached in a direction at a distance that ensures that n or more markings are fully visible in the direction, the markings are attached in different planes, and the pose of the parallel kinematic system can be determined based on an image that is captured by the camera and contains at least any n markings in the direction.