1,110 research outputs found
Air pollution modelling using a graphics processing unit with CUDA
The Graphics Processing Unit (GPU) is a powerful tool for parallel computing.
In the past years the performance and capabilities of GPUs have increased, and
the Compute Unified Device Architecture (CUDA) - a parallel computing
architecture - has been developed by NVIDIA to utilize this performance in
general purpose computations. Here we show for the first time a possible
application of GPU for environmental studies serving as a basement for decision
making strategies. A stochastic Lagrangian particle model has been developed on
CUDA to estimate the transport and the transformation of the radionuclides from
a single point source during an accidental release. Our results show that
parallel implementation achieves typical acceleration values in the order of
80-120 times compared to CPU using a single-threaded implementation on a 2.33
GHz desktop computer. Only very small differences have been found between the
results obtained from GPU and CPU simulations, which are comparable with the
effect of stochastic transport phenomena in atmosphere. The relatively high
speedup with no additional costs to maintain this parallel architecture could
result in a wide usage of GPU for diversified environmental applications in the
near future.Comment: 5 figure
Parametric Study of Changes in Human Balancing Skill by Repeated Balancing Trials on Rolling Balance Board
Dynamic balance conditions were realized by asking eight volunteers to stand on uniaxial balance board with adjustable geometry and to carry out 60 s long balancing trials. Four different balance board geometry were used, each associated with different difficulty level. Balancing trials were repeated five times weekly (learning period) in order to test improvement of balancing skill. The measurement was repeated eight weeks after the learning period in order to check the persistence of the balancing skill (confirmation session). Oscillations of ankle angle and hip angle were monitored by OptiTrack motion capture system and four stabilometry parameters were used to characterize improvement in balancing performance, namely, Standard Deviation (STD), Largest Amplitude (LA), Normalized Path Length (NPL) and Mean Power Frequency (MPF). STD and NPL show similar tendency to the preliminary expectations, therefore they can be considered as good measures to describe balancing performance. Results show that subjects used ankle strategy for the less difficult balance board configurations, while for the more difficult tasks, hip strategy was also involved. Changes in STD and NPL during the learning period showed that the improvement and the persistence in balancing skill is more significant for more difficult balancing tasks
Composing Control Barrier Functions for Complex Safety Specifications
The increasing complexity of control systems necessitates control laws that
guarantee safety w.r.t. complex combinations of constraints. In this letter, we
propose a framework to describe compositional safety specifications with
control barrier functions (CBFs). The specifications are formulated as Boolean
compositions of state constraints, and we propose an algorithmic way to create
a single continuously differentiable CBF that captures these constraints and
enables safety-critical control. We describe the properties of the proposed
CBF, and we demonstrate its efficacy by numerical simulations.Comment: Submitted to the IEEE Control System Letters (L-CSS) and the 2024
American Control Conference (ACC). 6 pages, 3 figure
MECHANICAL MODEL FOR HUMAN BALANCING ON ROLLING BALANCE BOARD
A two-degree-of-freedom mechanical model was developed to analyze human balancing on rolling balance board in the frontal plane. The human nervous system is modeled as a proportionalderivative controller with constant feedback delay. The radius R of the wheels and the board distance h measured from the center of the wheel are adjustable parameters. Simulation results using the mechanical model were compared with real balancing trials recorded by an OptiTrack motion capture system. The goal of the paper is to investigate whether the two-degree-of-freedom model is accurate enough to model the balancing task and to introduce a stabilometry parameter in order to characterize balancing skill in case of different set of R and h. The conclusion is that the angle of the upper body and the angle of the head also play an important role in the balancing process therefore a three- or four-degree-of-freedom model is more appropriate
Safety-Critical Traffic Control by Connected Automated Vehicles
Connected automated vehicles (CAVs) have shown great potential in improving
traffic throughput and stability. Although various longitudinal control
strategies have been developed for CAVs to achieve string stability in
mixed-autonomy traffic systems, the potential impact of these controllers on
safety has not yet been fully addressed. This paper proposes safety-critical
traffic control (STC) by CAVs -- a strategy that allows a CAV to stabilize the
traffic behind it, while maintaining safety relative to both the preceding
vehicle and the following connected human-driven vehicles (HDVs). Specifically,
we utilize control barrier functions (CBFs) to impart collision-free behavior
with formal safety guarantees to the closed-loop system. The safety of both the
CAV and HDVs is incorporated into the framework through a quadratic
program-based controller, that minimizes deviation from a nominal stabilizing
traffic controller subject to CBF-based safety constraints. Considering that
some state information of the following HDVs may be unavailable to the CAV, we
employ state observer-based CBFs for STC. Finally, we conduct extensive
numerical simulations -- that include vehicle trajectories from real data -- to
demonstrate the efficacy of the proposed approach in achieving string stable
and, at the same time, provably safe traffic
Connected Cruise and Traffic Control for Pairs of Connected Automated Vehicles
This paper considers mixed traffic consisting of connected automated vehicles
equipped with vehicle-to-everything (V2X) connectivity and human-driven
vehicles. A control strategy is proposed for communicating pairs of connected
automated vehicles, where the two vehicles regulate their longitudinal motion
by responding to each other, and, at the same time, stabilize the human-driven
traffic between them. Stability analysis is conducted to find stabilizing
controllers, and simulations are used to show the efficacy of the proposed
approach. The impact of the penetration of connectivity and automation on the
string stability of traffic is quantified. It is shown that, even with moderate
penetration, connected automated vehicle pairs executing the proposed
controllers achieve significant benefits compared to when these vehicles are
disconnected and controlled independently.Comment: Accepted to the IEEE Transactions on Intelligent Transportation
Systems. 11 pages, 10 figure
On the Safety of Connected Cruise Control: Analysis and Synthesis with Control Barrier Functions
Connected automated vehicles have shown great potential to improve the
efficiency of transportation systems in terms of passenger comfort, fuel
economy, stability of driving behavior and mitigation of traffic congestions.
Yet, to deploy these vehicles and leverage their benefits, the underlying
algorithms must ensure their safe operation. In this paper, we address the
safety of connected cruise control strategies for longitudinal car following
using control barrier function (CBF) theory. In particular, we consider various
safety measures such as minimum distance, time headway and time to conflict,
and provide a formal analysis of these measures through the lens of CBFs.
Additionally, motivated by how stability charts facilitate stable controller
design, we derive safety charts for existing connected cruise controllers to
identify safe choices of controller parameters. Finally, we combine the
analysis of safety measures and the corresponding stability charts to
synthesize safety-critical connected cruise controllers using CBFs. We verify
our theoretical results by numerical simulations.Comment: Accepted to the 62nd IEEE Conference on Decision and Control. 6
pages, 5 figure
Potrebe u ishrani mlađi štuke (esox lucius) gajene u recirkulacionom sistemu
Zahvaljujući napretku tehnologije, danas je moguće intenzivno gajenje juvenilne štuke u recirkulacionom sistemu korišćenjem formulisane komercijalne hrane (Wolnicki i Górny 1997). Komercijalna hrana koja se trenutno koristi za ishranu štuke je formulisana za druge vrste kao što su pastrmka, som i jesetra. Ova hrana se veoma razlikuje po sastavu proteina i sadržaju energije, što može da utiče na parametre proizvodnje. Smanjivanje odnosa svrarljivosti proteina/energetska efikasnost (DP/DE) u smešama može dovesti do većeg zadržavanja proteina, međutim može imati efekte na zdravlje riba i kvalitet proizvoda. Prvi cilj ove studije je bio da se istraži efekat komercijalnih smeša sa različitom koncentracijom proteina i lipida na juvenilne štuke manje od 20g (eksperiment I) i preko 70g (eksperiment II). Današnji trendovi u proizvodnji hrane za ribe su usmereni u pravcu zamene ribljeg brašna alternativnim izvorima proteina kao što su biljke, suvozemne životinje i nus-proizvodi. Ovi trendovi su dirigovani kako ekonomskim tako i etičkim pitanjima (Brinker and Reiter 2011). Drugi cilj ovog rada je bio da se istraži delimična zamena ribljeg brašna u smešama. U trećem eksperimentu, ispitivana je delimična zamena ribljeg brašna sa pšeničnim glutenom i živinskim brašnom
Verifying Safe Transitions between Dynamic Motion Primitives on Legged Robots
Functional autonomous systems often realize complex tasks by utilizing state
machines comprised of discrete primitive behaviors and transitions between
these behaviors. This architecture has been widely studied in the context of
quasi-static and dynamics-independent systems. However, applications of this
concept to dynamical systems are relatively sparse, despite extensive research
on individual dynamic primitive behaviors, which we refer to as "motion
primitives." This paper formalizes a process to determine dynamic-state aware
conditions for transitions between motion primitives in the context of safety.
The result is framed as a "motion primitive graph" that can be traversed by
standard graph search and planning algorithms to realize functional autonomy.
To demonstrate this framework, dynamic motion primitives -- including standing
up, walking, and jumping -- and the transitions between these behaviors are
experimentally realized on a quadrupedal robot
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