Manual removal of burrs on castings introduces health, safety, and environmental concerns. Automated removal of highly variable casting burrs could improve safety, but requires a solution based on ...robots, smart sensors, and advanced algorithms to tackle the problem in a flexible and cost-effective way. This paper presents a system for automatic tool trajectory generation for robotic deburring of cast parts with a specific focus on the robotic tool trajectory generation algorithm. The system generates a robotic trajectory adapted to the specific workpiece based on CAD model and 3D scans of the workpiece. The registered 3D scans and CAD model is used to generate a 3D model of each individual workpiece. This is fed into the tool trajectory generation algorithm. The algorithm uses the generated 3D model as well as a priori knowledge of the casting process to generate the tool trajectory. The tool trajectory planning algorithm has been tested on a set of various 3D models of cast parts, and the generated robotic tool path has been both simulated and tested on a KUKA KR 60.
We present an integrated approach for reconstructing high-fidelity three-dimensional (3D) models using consumer RGB-D cameras. RGB-D registration and reconstruction algorithms are prone to errors ...from scanning noise, making it hard to perform 3D reconstruction accurately. The key idea of our method is to assign a probabilistic uncertainty model to each depth measurement, which then guides the scan alignment and depth fusion. This allows us to effectively handle inherent noise and distortion in depth maps while keeping the overall scan registration procedure under the iterative closest point framework for simplicity and efficiency. We further introduce a local-to-global, submap-based, and uncertainty-aware global pose optimization scheme to improve scalability and guarantee global model consistency. Finally, we have implemented the proposed algorithm on the GPU, achieving real-time 3D scanning frame rates and updating the reconstructed model on-the-fly. Experimental results on simulated and real-world data demonstrate that the proposed method outperforms state-of-the-art systems in terms of the accuracy of both recovered camera trajectories and reconstructed models.
Abstract This paper focuses on the Light Detection and Ranging (LiDAR)–Inertial Measurement Unit (IMU) simultaneous localization and mapping (SLAM) problem: How to fuse the sensor measurement from ...the LiDAR and IMU to online estimate robot's poses and build a consistent map of the environment. This paper presents LTA‐OM: an efficient, robust, and accurate LiDAR SLAM system. Employing fast direct LiDAR‐inertial odometry (FAST‐LIO2) and Stable Triangle Descriptor as LiDAR–IMU odometry and the loop detection method, respectively, LTA‐OM is implemented to be functionally complete, including loop detection and correction, false‐positive loop closure rejection, long‐term association (LTA) mapping, and multisession localization and mapping. One novelty of this paper is the real‐time LTA mapping, which exploits the direct scan‐to‐map registration of FAST‐LIO2 and employs the corrected history map to provide direct global constraints to the LIO mapping process. LTA mapping also has the notable advantage of achieving drift‐free odometry at revisit places. Besides, a multisession mode is designed to allow the user to store the current session's results, including the corrected map points, optimized odometry, and descriptor database for future sessions. The benefits of this mode are additional accuracy improvement and consistent map stitching, which is helpful for life‐long mapping. Furthermore, LTA‐OM has valuable features for robot control and path planning, including high‐frequency and real‐time odometry, driftless odometry at revisit places, and fast loop closing convergence. LTA‐OM is versatile as it is applicable to both multiline spinning and solid‐state LiDARs, mobile robots and handheld platforms. In experiments, we exhaustively benchmark LTA‐OM and other state‐of‐the‐art LiDAR systems with 18 data sequences. The results show that LTA‐OM steadily outperforms other systems regarding trajectory accuracy, map consistency, and time consumption. The robustness of LTA‐OM is validated in a challenging scene—a multilevel building having similar structures at different levels. To demonstrate our system, we created a video which can be found on https://youtu.be/DVwppEKlKps .
Surface deterioration of concrete subjected to freezing and thawing in combination with deicing salts is one of the most important factors determining the durability of concrete infrastructure in ...cold climates. The freeze–thaw deicing salt (FTDS) resistance of cementitious materials can be determined by the capillary suction of de‐icing chemicals and freeze–thaw (CDF) test. Specimens are subjected to repeated freeze–thaw cycles with simultaneous addition of deicing salt and the amount of material scaled off near the surface is determined. For concretes with adequate FTDS resistance, this test method works very well. However, specimens with unknown performance often experience increased edge scaling. This leads to a falsification of results and consequently to an underestimation of the actual freeze–thaw resistance. In materials research, however, concretes with high levels of surface deterioration are studied in order to investigate various factors of influence on the freeze–thaw resistance of concretes in a targeted manner. This article presents a novel methodology that delivers new information regarding surface deterioration of CDF samples using high‐resolution 3D scan data. Change of volume is used to support deterioration results of the standard CDF methodology. Increase of surface area is used to estimate change in roughness of samples.
Herein, a novel methodology that investigates the surface deterioration of mortar samples exposed to freeze–thaw cycles in combination with deicing salt agents using a high‐resolution 3D scanner is presented. The changes in volume, sample height, and roughness are used to examine the durability of the samples in comparison with a standard test method.
•The cross-sectional area of corroded steel bars follows a mixed normal distribution.•Both yield and ultimate loads decrease linearly with an increase of corrosion loss.•Corrosion does not change the ...mechanical properties of steel bars significantly.•Elongation and ductility decrease exponentially with an increase of corrosion loss.•Corrosion changes the fracture mode from mixed ductile/brittle to brittle.
This study experimentally investigated the effect of corrosion non-uniformity on the mechanical property degradation of deformed steel bars. Both the average and critical cross-sectional areas were determined using a 3D laser scanner. Tensile test results and statistical analysis showed that both the yield and ultimate loads linearly decreased with an increase of corrosion loss while the elongation and ductility decreased exponentially. Corrosion did not affect the yield and ultimate strength based on the critical cross-sectional area. Mixed brittle and ductile fracture occurred in uncorroded steel bars while brittle fracture initiated at corrosion pits and propagated outwards in corroded steel bars.
•Tailored signal processing tools for processing data from embedded wireless accelerometers for condition monitoring of railway crossing panels.•Novel frequency-domain displacement reconstruction ...method which robustness is tested with acceleration traces from over 100 000 train passages over eight crossing panels.•Application of multibody simulations of the dynamic train–track interaction for interpretation of the measured signals and validation of the developed signal processing tools.•The separation of the track response into quasi-static and dynamic domains based on deformation wavelength regions is proposed as a promising strategy to observe the ballast condition and the crossing geometry condition, respectively.
Railway switches and crossings (S&C, turnouts) connect different track sections and create a railway network by allowing trains to change tracks. This functionality comes at a cost as the load-inducing rail discontinuities in the switch and crossing panels cause much larger degradation rates for S&C compared to regular plain line tracks. The high degradation rates make remote condition monitoring an interesting prospect for infrastructure managers to optimise maintenance and ensure safe operations. To this end, this paper addresses the development of tailored signal processing tools for condition monitoring using embedded accelerometers in crossing panels. Multibody simulations of the dynamic train–track interaction are used to aid the interpretation of the measured signals in a first step towards building a model-based condition monitoring system. An analysis is performed using sleeper acceleration measurement data generated by 100 000 train passages in eight crossing panels. Based on the given data, a novel frequency-domain displacement reconstruction method is developed and the robustness of the method with respect to encountered operational variability of the measured data is demonstrated. The separation of the track response into quasi-static and dynamic domains based on deformation wavelength regions is proposed as a promising strategy to observe the ballast condition and the crossing geometry condition, respectively.
