45 research outputs found
UAS Simulator for Modeling, Analysis and Control in Free Flight and Physical Interaction
This paper presents the ARCAD simulator for the rapid development of Unmanned
Aerial Systems (UAS), including underactuated and fully-actuated multirotors,
fixed-wing aircraft, and Vertical Take-Off and Landing (VTOL) hybrid vehicles.
The simulator is designed to accelerate these aircraft's modeling and control
design. It provides various analyses of the design and operation, such as
wrench-set computation, controller response, and flight optimization. In
addition to simulating free flight, it can simulate the physical interaction of
the aircraft with its environment. The simulator is written in MATLAB to allow
rapid prototyping and is capable of generating graphical visualization of the
aircraft and the environment in addition to generating the desired plots. It
has been used to develop several real-world multirotor and VTOL applications.
The source code is available at
https://github.com/keipour/aircraft-simulator-matlab.Comment: In proceedings of the 2023 AIAA SciTech Forum, Session: Air and Space
Vehicle Dynamics, Systems, and Environments II
Image-based Visual Servo Control for Aerial Manipulation Using a Fully-Actuated UAV
Using Unmanned Aerial Vehicles (UAVs) to perform high-altitude manipulation
tasks beyond just passive visual application can reduce the time, cost, and
risk of human workers. Prior research on aerial manipulation has relied on
either ground truth state estimate or GPS/total station with some Simultaneous
Localization and Mapping (SLAM) algorithms, which may not be practical for many
applications close to infrastructure with degraded GPS signal or featureless
environments. Visual servo can avoid the need to estimate robot pose. Existing
works on visual servo for aerial manipulation either address solely
end-effector position control or rely on precise velocity measurement and
pre-defined visual visual marker with known pattern. Furthermore, most of
previous work used under-actuated UAVs, resulting in complicated mechanical and
hence control design for the end-effector. This paper develops an image-based
visual servo control strategy for bridge maintenance using a fully-actuated
UAV. The main components are (1) a visual line detection and tracking system,
(2) a hybrid impedance force and motion control system. Our approach does not
rely on either robot pose/velocity estimation from an external localization
system or pre-defined visual markers. The complexity of the mechanical system
and controller architecture is also minimized due to the fully-actuated nature.
Experiments show that the system can effectively execute motion tracking and
force holding using only the visual guidance for the bridge painting. To the
best of our knowledge, this is one of the first studies on aerial manipulation
using visual servo that is capable of achieving both motion and force control
without the need of external pose/velocity information or pre-defined visual
guidance.Comment: Accepted by 2023 IEEE/RSJ International Conference on Intelligent
Robots and Systems (IROS
Intention Aware Robot Crowd Navigation with Attention-Based Interaction Graph
We study the problem of safe and intention-aware robot navigation in dense
and interactive crowds. Most previous reinforcement learning (RL) based methods
fail to consider different types of interactions among all agents or ignore the
intentions of people, which results in performance degradation. In this paper,
we propose a novel recurrent graph neural network with attention mechanisms to
capture heterogeneous interactions among agents through space and time. To
encourage longsighted robot behaviors, we infer the intentions of dynamic
agents by predicting their future trajectories for several timesteps. The
predictions are incorporated into a model-free RL framework to prevent the
robot from intruding into the intended paths of other agents. We demonstrate
that our method enables the robot to achieve good navigation performance and
non-invasiveness in challenging crowd navigation scenarios. We successfully
transfer the policy learned in simulation to a real-world TurtleBot 2i
Transcriptomic profiling suggests candidate molecular responses to waterlogging in cassava
Owing to climate change impacts, waterlogging is a serious abiotic stress that affects crops, resulting in stunted growth and loss of productivity. Cassava (Manihot esculenta Grantz) is usually grown in areas that experience high amounts of rainfall; however, little research has been done on the waterlogging tolerance mechanism of this species. Therefore, we investigated the physiological responses of cassava plants to waterlogging stress and analyzed global gene transcription responses in the leaves and roots of waterlogged cassava plants. The results showed that waterlogging stress significantly decreased the leaf chlorophyll content, caused premature senescence, and increased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the leaves and roots. In total, 2538 differentially expressed genes (DEGs) were detected in the leaves and 13364 in the roots, with
1523 genes shared between the two tissues. Comparative analysis revealed that the DEGs were related mainly to photosynthesis, amino metabolism, RNA transport and degradation. We also summarized the functions of the pathways that respond to waterlogging and are involved in photosynthesis, glycolysis and galactose metabolism. Additionally, many transcription factors (TFs), such as MYBs, AP2/ERFs, WRKYs and NACs, were identified, suggesting that they potentially function in the waterlogging response in cassava. The expression of 12 randomly selected genes evaluated via both quantitative real-time PCR (qRT-PCR) and RNA sequencing (RNA-seq) was highly correlated (R2 = 0.9077), validating the reliability of the RNA-seq results. The potential waterlogging stress-related transcripts identified in this study are representatives of candidate genes and molecular resources for further understanding the molecular mechanisms underlying the waterlogging response in cassava
PyPose: A Library for Robot Learning with Physics-based Optimization
Deep learning has had remarkable success in robotic perception, but its
data-centric nature suffers when it comes to generalizing to ever-changing
environments. By contrast, physics-based optimization generalizes better, but
it does not perform as well in complicated tasks due to the lack of high-level
semantic information and the reliance on manual parametric tuning. To take
advantage of these two complementary worlds, we present PyPose: a
robotics-oriented, PyTorch-based library that combines deep perceptual models
with physics-based optimization techniques. Our design goal for PyPose is to
make it user-friendly, efficient, and interpretable with a tidy and
well-organized architecture. Using an imperative style interface, it can be
easily integrated into real-world robotic applications. Besides, it supports
parallel computing of any order gradients of Lie groups and Lie algebras and
-order optimizers, such as trust region methods. Experiments
show that PyPose achieves 3-20 speedup in computation compared to
state-of-the-art libraries. To boost future research, we provide concrete
examples across several fields of robotics, including SLAM, inertial
navigation, planning, and control
PyPose v0.6: The Imperative Programming Interface for Robotics
PyPose is an open-source library for robot learning. It combines a
learning-based approach with physics-based optimization, which enables seamless
end-to-end robot learning. It has been used in many tasks due to its
meticulously designed application programming interface (API) and efficient
implementation. From its initial launch in early 2022, PyPose has experienced
significant enhancements, incorporating a wide variety of new features into its
platform. To satisfy the growing demand for understanding and utilizing the
library and reduce the learning curve of new users, we present the fundamental
design principle of the imperative programming interface, and showcase the
flexible usage of diverse functionalities and modules using an extremely simple
Dubins car example. We also demonstrate that the PyPose can be easily used to
navigate a real quadruped robot with a few lines of code
Revealing the missing expressed genes beyond the human reference genome by RNA-Seq
<p>Abstract</p> <p>Background</p> <p>The complete and accurate human reference genome is important for functional genomics researches. Therefore, the incomplete reference genome and individual specific sequences have significant effects on various studies.</p> <p>Results</p> <p>we used two RNA-Seq datasets from human brain tissues and 10 mixed cell lines to investigate the completeness of human reference genome. First, we demonstrated that in previously identified ~5 Mb Asian and ~5 Mb African novel sequences that are absent from the human reference genome of NCBI build 36, ~211 kb and ~201 kb of them could be transcribed, respectively. Our results suggest that many of those transcribed regions are not specific to Asian and African, but also present in Caucasian. Then, we found that the expressions of 104 RefSeq genes that are unalignable to NCBI build 37 in brain and cell lines are higher than 0.1 RPKM. 55 of them are conserved across human, chimpanzee and macaque, suggesting that there are still a significant number of functional human genes absent from the human reference genome. Moreover, we identified hundreds of novel transcript contigs that cannot be aligned to NCBI build 37, RefSeq genes and EST sequences. Some of those novel transcript contigs are also conserved among human, chimpanzee and macaque. By positioning those contigs onto the human genome, we identified several large deletions in the reference genome. Several conserved novel transcript contigs were further validated by RT-PCR.</p> <p>Conclusion</p> <p>Our findings demonstrate that a significant number of genes are still absent from the incomplete human reference genome, highlighting the importance of further refining the human reference genome and curating those missing genes. Our study also shows the importance of <it>de novo </it>transcriptome assembly. The comparative approach between reference genome and other related human genomes based on the transcriptome provides an alternative way to refine the human reference genome.</p