Tunnel Segment Flatness Measurement Using Laser Point-to-Plane Fitting
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Solution Overview
Problem
Existing manual methods for measuring tunnel segment flatness are arbitrary, inefficient, and difficult to implement in spatially constrained tunneling environments, leading to suboptimal target planes and potential damage to tunnel segments due to high local pressures.
Innovation Solution
A calculation method using laser displacement sensors to determine spatial point-plane relations, fitting a reference plane, and translating it to a calibration plane for accurate flatness measurement, facilitated by an automatic guiding system and distance measurement system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If manual measurement with total station is used, then measurement can be performed, but measurement efficiency and timeliness are poor
Solution Approach 1:
The patent replaces the manual mechanical measurement system (total station) with an automatic optical measurement system (laser displacement sensor). The laser sensor automatically captures spatial coordinates of multiple measuring points on tunnel segment end surfaces, eliminating manual intervention and significantly improving measurement efficiency and timeliness while maintaining measurement capability.
Solution Approach 2:
The measurement system performs self-service by automatically acquiring spatial coordinates of measuring points, calculating deviations from the calibration plane, and generating measurement results without human intervention. The system autonomously completes the entire measurement process, from data acquisition to analysis, resolving the efficiency and time loss issues of manual measurement.
2Measurement precision
If three points are selected empirically to calculate target plane, then measurement can be performed, but arbitrariness is high and optimal plane cannot be guaranteed
Solution Approach 1:
The patent replaces the empirical three-point method with a mathematical optimization system based on least squares fitting. The system calculates the calibration plane equation ax+by+cz+d=0 by minimizing the sum of squared deviations from all measuring points, providing a scientifically rigorous and unique optimal plane rather than an arbitrary one based on three selected points.
Solution Approach 2:
The patent transforms the measurement approach from selecting discrete three points to utilizing all available measuring point coordinates. By changing the parameter set from three arbitrary points to multiple measured points and applying least squares optimization, the system achieves a reliable, unique calibration plane that maximizes measurement precision and scientific validity.
3Ease of operation
If manual measurement coordinates are used, then measurement can be performed, but operation is not convenient in spatially constrained tunneling environment
Solution Approach 1:
The patent replaces complex manual total station operations with a simplified laser displacement sensor system. The laser sensor can be positioned on the tunneling shield and automatically measures multiple points without requiring manual coordinate input or complex setup procedures, greatly improving operational convenience in the confined tunneling environment despite the added measurement system.
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 highly efficient and accurate flatness measurement of tunnel segments, reducing manual errors and ensuring timely compensation for deviations, thus enhancing engineering quality and safety.
Implementation Method 1
installing at least one laser displacement sensor on an assembly plane of at least one thrust cylinder of a tunneling shield, with the at least one laser displacement sensor emitting laser beams
Data Source
AI summary
A calculation method for measuring the flatness of cross-section of a tunnel segment, comprising: mounting laser displacement sensors on a thrust cylinder assembly plane of a tunnel boring machine, an emitting laser beam of each sensor being parallel to an axis of a cylinder, being perpendicular to the propulsion cylinder assembly plane, and pointing to the end surface of a segment ring to be tested; the intersection of the straight line where the laser of each laser displacement sensor is located and the propulsion cylinder assembly plane is referred to as a base point Pi; the intersection formed between the laser of each laser displacement sensor and said segment ring is referred to as a measurement point Pi′; the corresponding spatial coordinates of each base point are represented by Pi(xi,yi,zi); the corresponding spatial coordinates of each measurement point are represented by Pi′(xi′,yi′,zi′); a rear shield axis vector nrear shield=(xn,yn,zn).