SL Sensor: An Open-Source, ROS-Based, Real-Time Structured Light Sensor for High Accuracy Construction Robotic Applications

TL;DR

SL Sensor is an open-source, ROS-based structured light sensor that achieves millimeter-level accuracy in real-time 3D surface reconstruction, surpassing commercial depth cameras and enabling advanced construction robotics tasks.

Contribution

The paper introduces SL Sensor, a high-accuracy, real-time structured light sensing platform with a novel motion compensation strategy, and provides open-source hardware and software for construction robotics.

Findings

SL Sensor outperforms Azure Kinect and RealSense L515 in accuracy and precision.

It operates effectively during linear motion with the developed compensation strategy.

Produces detailed 3D reconstructions of spray plastered surfaces.

Abstract

High accuracy 3D surface information is required for many construction robotics tasks such as automated cement polishing or robotic plaster spraying. However, consumer-grade depth cameras currently found in the market are not accurate enough for these tasks where millimeter (mm)-level accuracy is required. This paper presents SL Sensor, a structured light sensing solution capable of producing high fidelity point clouds at 5 Hz by leveraging on phase shifting profilometry (PSP) codification techniques. The SL Sensor was compared with to two commercial depth cameras - the Azure Kinect and RealSense L515. Experiments showed that the SL Sensor surpasses the two devices in both precision and accuracy for indoor surface reconstruction applications. Furthermore, to demonstrate SL Sensor's ability to be a structured light sensing research platform for robotic applications, a motion compensation strategy was developed that allows the SL Sensor to operate during linear motion when traditional PSP methods only work when the sensor is static. Field experiments show that the SL Sensor is able to produce highly detailed reconstructions of spray plastered surfaces. The robot operating system (ROS)-based software and a sample hardware build of the SL Sensor are made open-source with the objective to make structured light sensing more accessible to the construction robotics community. All documentation and code is available at https://github.com/ethz-asl/sl_sensor/ .