128 research outputs found
Real-Time Simultaneous Localization and Mapping with LiDAR intensity
We propose a novel real-time LiDAR intensity image-based simultaneous
localization and mapping method , which addresses the geometry degeneracy
problem in unstructured environments. Traditional LiDAR-based front-end
odometry mostly relies on geometric features such as points, lines and planes.
A lack of these features in the environment can lead to the failure of the
entire odometry system. To avoid this problem, we extract feature points from
the LiDAR-generated point cloud that match features identified in LiDAR
intensity images. We then use the extracted feature points to perform scan
registration and estimate the robot ego-movement. For the back-end, we jointly
optimize the distance between the corresponding feature points, and the point
to plane distance for planes identified in the map. In addition, we use the
features extracted from intensity images to detect loop closure candidates from
previous scans and perform pose graph optimization. Our experiments show that
our method can run in real time with high accuracy and works well with
illumination changes, low-texture, and unstructured environments
An Adaptive Particle Swarm Optimization Algorithm Based on Directed Weighted Complex Network
The disadvantages of particle swarm optimization (PSO) algorithm are that it is easy to fall into local optimum in high-dimensional space and has a low convergence rate in the iterative process. To deal with these problems, an adaptive particle swarm optimization algorithm based on directed weighted complex network (DWCNPSO) is proposed. Particles can be scattered uniformly over the search space by using the topology of small-world network to initialize the particles position. At the same time, an evolutionary mechanism of the directed dynamic network is employed to make the particles evolve into the scale-free network when the in-degree obeys power-law distribution. In the proposed method, not only the diversity of the algorithm was improved, but also particles’ falling into local optimum was avoided. The simulation results indicate that the proposed algorithm can effectively avoid the premature convergence problem. Compared with other algorithms, the convergence rate is faster
TacIPC: Intersection- and Inversion-free FEM-based Elastomer Simulation For Optical Tactile Sensors
Tactile perception stands as a critical sensory modality for human
interaction with the environment. Among various tactile sensor techniques,
optical sensor-based approaches have gained traction, notably for producing
high-resolution tactile images. This work explores gel elastomer deformation
simulation through a physics-based approach. While previous works in this
direction usually adopt the explicit material point method (MPM), which has
certain limitations in force simulation and rendering, we adopt the finite
element method (FEM) and address the challenges in penetration and mesh
distortion with incremental potential contact (IPC) method. As a result, we
present a simulator named TacIPC, which can ensure numerically stable
simulations while accommodating direct rendering and friction modeling. To
evaluate TacIPC, we conduct three tasks: pseudo-image quality assessment,
deformed geometry estimation, and marker displacement prediction. These tasks
show its superior efficacy in reducing the sim-to-real gap. Our method can also
seamlessly integrate with existing simulators. More experiments and videos can
be found in the supplementary materials and on the website:
https://sites.google.com/view/tac-ipc
Intersection-free Robot Manipulation with Soft-Rigid Coupled Incremental Potential Contact
This paper presents a novel simulation platform, ZeMa, designed for robotic
manipulation tasks concerning soft objects. Such simulation ideally requires
three properties: two-way soft-rigid coupling, intersection-free guarantees,
and frictional contact modeling, with acceptable runtime suitable for deep and
reinforcement learning tasks. Current simulators often satisfy only a subset of
these needs, primarily focusing on distinct rigid-rigid or soft-soft
interactions. The proposed ZeMa prioritizes physical accuracy and integrates
the incremental potential contact method, offering unified dynamics simulation
for both soft and rigid objects. It efficiently manages soft-rigid contact,
operating 75x faster than baseline tools with similar methodologies like
IPC-GraspSim. To demonstrate its applicability, we employ it for parallel grasp
generation, penetrated grasp repair, and reinforcement learning for grasping,
successfully transferring the trained RL policy to real-world scenarios
Research on the development law of karst caves on water conducting fractures under the influence of mining in Southwest Karst Mining Areas
Southwest Guizhou mining area is a typical karst development mining area in China. Under the influence of mining, the height of karst roof water conducting cracks is abnormally developed. During the rainy season, atmospheric precipitation is extremely easy to enter the underground working face through ultra-high water conducting channels, causing water inrush disasters at the working face, seriously affecting the normal production of the mine. Therefore, based on the analysis of the occurrence characteristics of karst caves in Xintian Coal Mine, the development rules of karst roof water conducting fracture zones during mining were studied by means of on-site measurement, indoor simulation, and theoretical analysis. The development mechanism of ultra-high water conducting fractures was revealed. The results show that: ①The roof karst caves in the study area have obvious zonation phenomenon from top to bottom in the layers such as the surface, the Yulongshan section, and the Changxing Formation. The surface water holes develop along the gullies, and the karst caves in the upper and middle parts of the strong aquifer in the Yulongshan section develop, presenting different forms of beads. The Changxing Formation only locally hosts karst caves with smaller diameters; ② Karst caves in karst aquifers have an important impact on water conducting fractures. Without karst caves, the development height of water conducting fractures is 43.1 m, and the fracture mining ratio is 14.4. Under karst caves, the development of water conducting fractures is abnormal, with a height of 173.1 m, and a fracture mining ratio of 57.7, which communicates with the strong limestone aquifer in the Yulong Mountain section; ③ Karst roof water conducting fissures consist of two parts: mining upward fissures and karst cave instability downward fissures. Under the influence of mining, karst caves become unstable under the combined action of concentrated stress and mining additional stress, and are prone to form downward fissures, which communicate with mining upward fissures, ultimately forming a special ultra-high water conducting fissure in southwestern Guizhou mining area
Thickness-dependent magnetic properties in Pt[CoNi]n multilayers with perpendicular magnetic anisotropy
We systematically investigated the Ni and Co thickness-dependent
perpendicular magnetic anisotropy (PMA) coefficient, magnetic domain
structures, and magnetization dynamics of Pt(5 nm)/[Co(t_Co nm)/Ni(t_Ni
nm)]5/Pt(1 nm) multilayers by combining the four standard magnetic
characterization techniques. The magnetic-related hysteresis loops obtained
from the field-dependent magnetization M and anomalous Hall resistivity (AHR)
\r{ho}_xy found that the two serial multilayers with t_Co = 0.2 and 0.3 nm have
the optimum PMA coefficient K_U well as the highest coercivity H_C at the Ni
thickness t_Ni = 0.6 nm. Additionally, the magnetic domain structures obtained
by Magneto-optic Kerr effect (MOKE) microscopy also significantly depend on the
thickness and K_U of the films. Furthermore, the thickness-dependent linewidth
of ferromagnetic resonance is inversely proportional to K_U and H_C, indicating
that inhomogeneous magnetic properties dominate the linewidth. However, the
intrinsic Gilbert damping constant determined by a linear fitting of
frequency-dependent linewidth does not depend on Ni thickness and K_U. Our
results could help promote the PMA [Co/Ni] multilayer applications in various
spintronic and spin-orbitronic devices.Comment: 17 pages, 4 figure
- …