288 research outputs found
Model-based estimation of off-highway road geometry using single-axis LADAR and inertial sensing
This paper applies some previously studied extended
Kalman filter techniques for planar road geometry estimation
to the domain of autonomous navigation of off-highway
vehicles. In this work, a clothoid model of the road geometry is
constructed and estimated recursively based on road features
extracted from single-axis LADAR range measurements. We
present a method for feature extraction of the road centerline
in the image plane, and describe its application to recursive
estimation of the road geometry. We analyze the performance of
our method against simulated motion of varied road geometries
and against closed-loop detection, tracking and following of
desert roads. Our method accomodates full 6 DOF motion of
the vehicle as it navigates, constructs consistent estimates of the
road geometry with respect to a fixed global reference frame,
and requires an estimate of the sensor pose for each range
measurement
Development of bent-up triangular tab shear transfer (BTTST) enhancement in cold-formed steel (CFS)-concrete composite beams
Cold-formed steel (CFS) sections, have been recognised as an important
contributor to environmentally responsible and sustainable structures in developed
countries, and CFS framing is considered as a sustainable 'green' construction material
for low rise residential and commercial buildings. However, there is still lacking of data
and information on the behaviour and performance of CFS beam in composite
construction. The use of CFS has been limited to structural roof trusses and a host of nonstructural applications. One of the limiting features of CFS is the thinness of its section
(usually between 1.2 and 3.2 mm thick) that makes it susceptible to torsional,
distortional, lateral-torsional, lateral-distortional and local buckling. Hence, a reasonable
solution is resorting to a composite construction of structural CFS section and reinforced
concrete deck slab, which minimises the distance from the neutral-axis to the top of the
deck and reduces the compressive bending stress in the CFS sections. Also, by arranging
two CFS channel sections back-to-back restores symmetricity and suppresses lateraltorsional and to a lesser extent, lateral-distortional buckling. The two-fold advantages
promised by the system, promote the use of CFS sections in a wider range of structural
applications. An efficient and innovative floor system of built-up CFS sections acting
compositely with a concrete deck slab was developed to provide an alternative composite
system for floors and roofs in buildings. The system, called Precast Cold-Formed SteelConcrete Composite System, is designed to rely on composite actions between the CFS
sections and a reinforced concrete deck where shear forces between them are effectively
transmitted via another innovative shear transfer enhancement mechanism called a bentup triangular tab shear transfer (BTTST). The study mainly comprises two major
components, i.e. experimental and theoretical work. Experimental work involved smallscale and large-scale testing of laboratory tests. Sixty eight push-out test specimens and
fifteen large-scale CFS-concrete composite beams specimens were tested in this program.
In the small-scale test, a push-out test was carried out to determine the strength and
behaviour of the shear transfer enhancement between the CFS and concrete. Four major
parameters were studied, which include compressive strength of concrete, CFS strength,
dimensions (size and angle) of BTTST and CFS thickness. The results from push-out test
were used to develop an expression in order to predict the shear capacity of innovative
shear transfer enhancement mechanism, BTTST in CFS-concrete composite beams. The
value of shear capacity was used to calculate the theoretical moment capacity of CFSconcrete composite beams. The theoretical moment capacities were used to validate the
large-scale test results. The large-scale test specimens were tested by using four-point
load bending test. The results in push-out tests show that specimens employed with
BTTST achieved higher shear capacities compared to those that rely only on a natural
bond between cold-formed steel and concrete and specimens with Lakkavalli and Liu
bent-up tab (LYLB). Load capacities for push-out test specimens with BTTST are
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relatively higher as compared to the equivalent control specimen, i.e. by 91% to 135%.
When compared to LYLB specimens the increment is 12% to 16%. In addition, shear
capacities of BTTST also increase with the increase in dimensions (size and angle) of
BTTST, thickness of CFS and concrete compressive strength. An equation was
developed to determine the shear capacity of BTTST and the value is in good agreement
with the observed test values. The average absolute difference between the test values
and predicted values was found to be 8.07%. The average arithmetic mean of the
test/predicted ratio (n) of this equation is 0.9954. The standard deviation (a) and the
coefficient of variation (CV) for the proposed equation were 0.09682 and 9.7%,
respectively. The proposed equation is recommended for the design of BTTST in CFSconcrete composite beams. In large-scale testing, specimens employed with BTTST
increased the strength capacities and reduced the deflection of the specimens. The
moment capacities, MU ) e X p for all specimens are above Mu>theory and show good agreement
with the calculated ratio (>1.00). It is also found that, strength capacities of CFS-concrete
composite beams also increase with the increase in dimensions (size and angle) of
BTTST, thickness of CFS and concrete compressive strength and a CFS-concrete
composite beam are practically designed with partial shear connection for equal moment
capacity by reducing number of BTTST. It is concluded that the proposed BTTST shear
transfer enhancement in CFS-concrete composite beams has sufficient strength and is
also feasible. Finally, a standard table of characteristic resistance, P t a b of BTTST in
normal weight concrete, was also developed to simplify the design calculation of CFSconcrete composite beams
Laser-camera composite sensing for road detection and tracing
An important feature in most urban roads and similar environments, such as in theme parks, campus sites, industrial estates, science parks, and the like, is the existence of pavements or curbs on either side de?ning the road boundaries. These curbs, which are mostly parallel to the road, can be harnessed to extract useful features of the road for implementing autonomous navigation or driver assistance systems. However, vision-alone methods for extraction of such curbs or road edge features with accurate depth information is a formidable task, as the curb is not conspicuous in the vision image and also requires the use of stereo images. Further, bad lighting, adverse weather conditions, nonlinear lens aberrations, or lens glare due to sun and other bright light sources can severely impair the road image quality and thus the operation of vision-alone methods. In this paper an alternative and novel approach involving the fusion of 2D laser range and monochrome vision image data is proposed to improve the robustness and reliability. Experimental results are presented to demonstrate the viability and effectiveness of the proposed methodology and its robustness to different road configurations and shadows
Curb-intersection feature based Monte Carlo Localization on urban roads
One of the most prominent features on an urban road is the curb, which defines the boundary of a road surface. An intersection is a junction of two or more roads, appearing where no curb exists. The combination of curb and intersection features and their idiosyncrasies carry significant information about the urban road network that can be exploited to improve a vehicle's localization. This paper introduces a Monte Carlo Localization (MCL) method using the curb-intersection features on urban roads. We propose a novel idea of “Virtual LIDAR” to get the measurement models for these features. Under the MCL framework, above road observation is fused with odometry information, which is able to yield precise localization. We implement the system using a single tilted 2D LIDAR on our autonomous test bed and show robust performance in the presence of occlusion from other vehicles and pedestrians
Curb-intersection feature based Monte Carlo Localization on urban roads
One of the most prominent features on an urban road is the curb, which defines the boundary of a road surface. An intersection is a junction of two or more roads, appearing where no curb exists. The combination of curb and intersection features and their idiosyncrasies carry significant information about the urban road network that can be exploited to improve a vehicle's localization. This paper introduces a Monte Carlo Localization (MCL) method using the curb-intersection features on urban roads. We propose a novel idea of “Virtual LIDAR” to get the measurement models for these features. Under the MCL framework, above road observation is fused with odometry information, which is able to yield precise localization. We implement the system using a single tilted 2D LIDAR on our autonomous test bed and show robust performance in the presence of occlusion from other vehicles and pedestrians
Cross Hallway Detection and Indoor Localization Using Flash Laser Detection and Ranging
A flash LADAR is investigated as a source of navigation information to support cross-hallway detection and relative localization. To accomplish this, a dynamic, flexible simulation was developed that simulated the LADAR and the noise of a LADAR system. Using simulated LADAR data, algorithms were developed that were shown to be effective at detecting cross hallways in simulated ideal environments and in simulated environments with noise. Relative position was determined in the same situations. A SwissRanger SR4000 flash LADAR was then used to collect real data and to verify algorithm performance in real environments. Hallway detection was shown to be possible in all real data sets, and the relative position-finding algorithm was shown to be accurate when compared to the absolute accuracy of the LADAR. Thus, flash LADAR is concluded to be an effective source for indoor navigation information
Workshop on Advanced Technologies for Planetary Instruments, part 1
This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. This volume contains papers presented at the Workshop on Advanced Technologies for Planetary Instruments on 28-30 Apr. 1993. This meeting was conceived in response to new challenges facing NASA's robotic solar system exploration program. Over the past several years, SDIO has sponsored a significant technology development program aimed, in part, at the production of instruments with these characteristics. This workshop provided an opportunity for specialists from the planetary science and DoD communities to establish contacts, to explore common technical ground in an open forum, and more specifically, to discuss the applicability of SDIO's technology base to planetary science instruments
Road curb tracking in an urban environment
Road detection and tracking is very useful in the synthesis of driver assistance and intelligent transportation systems. In this paper a methodology is proposed based on the extended Kalman filer for robust road curb detection and tracking using a combination of onboard active and passive sensors. The problem is formulated as detecting and tracking a maneuvering target in clutter using onboard sensors on a moving platform. The primary sensors utilized are a 2 dimensional SICK laser scanner, five encoders and a gyroscope, together with an image sensor (CCD camera). Compared to the active 20 laser scanner the CCD camera is capable of providing observations over an extended horizon, thus making available much useful information about the curb trend, which is exploited in mainly the laser based tracking algorithm. The advantage of the proposed image enhanced laser detection/tracking method, over laser alone detection/tracking, is illustrated using simulations and its robustness to varied road curvatures, branching, turns and scenarios, is demonstrated through experimental results. © 2003 ISlF
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