Crane Grapple Skew Detection Using Laser Reflectors
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Solution Overview
Problem
Current systems for determining the horizontal location and skew of a crane grappling member are inefficient due to high complexity and cost, and inaccuracies in measurement, particularly when handling containers under automated conditions where precision and reliability are critical.
Innovation Solution
A system utilizing a scanning laser distance sensor and reflectors with distinct shapes on the grappling member to accurately measure the horizontal location and skew, allowing for precise positioning and vertical trim, thereby reducing costs and improving calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple cameras and active infrared beacons are mounted on the container grapple to determine location and position, then measurement capability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The positioning system is segmented into two distinct functional components: passive reflectors mounted on the container grapple and an active scanning laser sensor mounted on the crane. This segmentation allows the complex measurement task to be divided into simpler sub-tasks, reducing the number of components needed on the grapple itself while maintaining measurement precision.
Solution Approach 2:
Passive reflectors serve as intermediaries between the container grapple and the scanning laser sensor. These reflectors reflect the laser beam back to the sensor without requiring active power sources or complex electronics on the grapple, thereby simplifying the device while enabling precise location and orientation measurement through the laser-reflector-sensor interaction.
2Measurement precision
If multiple beacons are mounted on the container grapple to determine elevation and trim, then measurement capability is improved, but cost and device complexity increase
Solution Approach 1:
The scanning laser sensor mounted on the crane performs multiple measurement functions simultaneously: it determines both the horizontal position (through reflector location) and the vertical orientation (through reflector orientation and spacing). This multi-functionality eliminates the need for separate beacon systems for elevation and trim measurement, reducing overall device complexity while maintaining comprehensive measurement capability.
Solution Approach 2:
The system transitions from using multiple discrete beacons in three-dimensional space to using a single scanning laser sensor that measures reflector positions angularly. By scanning the laser beam across different angles and measuring the reflected light, the system determines spatial coordinates and orientation through angular measurements rather than requiring multiple physical beacons at different heights and positions.
3Manufacturing precision
If conventional positioning systems are used on oscillating suspended container grapple, then basic positioning is achieved, but measurement accuracy is insufficient for automated stacking
Solution Approach 1:
The system replaces mechanical positioning methods (such as physical alignment tools or contact-based measurement devices) with an optical measurement system. The scanning laser sensor non-contactly measures the position and orientation of passive reflectors on the grapple, providing high-precision data for automated control without mechanical interference or wear, thereby achieving the required 5 cm precision for automated container stacking.
Solution Approach 2:
The system establishes a feedback loop where the scanning laser sensor continuously measures the actual position and orientation of the container grapple and its reflectors, and this measurement data is fed back to the control system. The control system uses this feedback information to calculate corrections and adjust the grapple's position and orientation in real-time, enabling precise automated stacking despite the oscillating and suspended nature of the grapple.
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
Enables precise and cost-effective determination of the grappling member's position and skew, enhancing automation and precision in container handling operations.
Implementation Method 1
A system utilizing a scanning laser distance sensor and reflectors with distinct shapes on the grappling member to accurately measure the horizontal location and skew
Implementation Method 2
scanning laser distance sensor mounted on said container crane and to reflectors in said container grapple
Data Source
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AI summary
The invention relates to a system for determining the horizontal location and skew of a grappling member (2) of a crane, the system comprising at least two types of reflectors (5, 6) arranged on the grappling member (2), the relative locations and shapes of which are known; at least one scanning distance sensor (7) mounted on the crane to measure the distance (R) and direction (a) from the crane to the reflectors; and a data processing device arranged to store in its memory the relative locations and shapes of the reflectors; and to determine the horizontal location and skew of the grappling member (2) on the basis of at least the relative locations and shapes of the reflectors and measured distances and directions from the crane to the reflectors.