# A Combined Sensor Design Applied to Large-Scale Measurement Systems

## TL;DR

This paper introduces a new sensor design that improves the accuracy of large-scale measurements, especially for hidden points and complex surfaces.

## Contribution

A multi-node fusion sensor design with nonlinear calibration and adaptive circuitry for enhanced large-space measurement accuracy.

## Key findings

- The sensor achieves a standard deviation better than 0.026 mm in a 7000 mm × 7000 mm × 3000 mm measurement area.
- Measurement accuracy for hidden points and free-form surfaces is better than 0.26 mm.
- The design meets most industrial measurement needs and expands the application of large-space systems.

## Abstract

The photoelectric sensing unit in a large-space measurement system primarily determines the measurement accuracy of the system. Aiming to resolve the problem whereby existing sensing units have difficulty accurately measuring the hidden points and free-form surfaces in large components, in this study, we designed a multi-node fusion of a combined sensor. Firstly, a multi-node fusion hidden-point measurement model and a solution model are established, and the measurement results converge after the number of nodes is simulated to be nine. Secondly, an adaptive front-end photoelectric conditioning circuit, including signal amplification, filtering, and adjustable level is designed, and the accuracy of the circuit function is verified. Then, a nonlinear least-squares calibration method is proposed by combining the constraints of the multi-position vector cones, and the internal parameters of the probe, in relation to the various detection nodes, are calibrated. Finally, a distributed system and laser tracking system are introduced to establish a fusion experimental validation platform, and the results show that the standard deviation and accuracy of the three-axis measurement of the test point of the combined sensor in the measurement area of 7000 mm × 7000 mm × 3000 mm are better than 0.026 mm and 0.24 mm, respectively, and the accuracy of the length measurement is within 0.28 mm. Further, the measurement accuracy of the hidden point of the aircraft hood and the free-form surface is better than 0.26 mm, which can meet most of the industrial measurement needs and expand the application field of large-space measurement systems.