This paper presents the use of place/transition petri nets (PNs) for the recognition and evaluation of complex multi-agent activities. The PNs were built automatically from the activity templates that are routinely used by experts to encode domain-specific knowledge. The PNs were built in such a way that they encoded the complex temporal relations between the individual activity actions. We extended the original PN formalism to handle the propagation of evidence using net tokens. The evaluation of the spatial and temporal properties of the actions was carried out using trajectory-based action detectors and probabilistic models of the action durations. The presented approach was evaluated using several examples of real basketball activities. The obtained experimental results suggest that this approach can be used to determine the type of activity that a team has performed as well as the stage at which the activity ended. 相似文献
This work proposes an adaptive control scheme applied to single link-flexible manipulators, which combines a feedback controller of the joint angle with an adaptive input shaper updated by an algebraic non-asymptotic identification. The feedback controller is designed to guarantee trajectory tracking of the joint angle, simplifying thus the input shaper, which can be designed for the arm dynamics only. The input shaper is updated by an algebraic identification of the natural frequency corresponding to the first vibration mode of the arm. In addition, the influence of the assumptions adopted to derive the algebraic identification on the performance of the estimation is studied. Finally, the proposed adaptive control strategy is implemented in practice. 相似文献
An aerosol sampling site based on a single-stage streaker sampler with four-hour time resolution was established in 1993 at Brandt-se-Baai, on the north-western coast of South Africa (31.5°S 18°E, 50 m asl). The site was deployed to monitor the generation of dust from the local mining operations and in part to test the hypothesis of large-scale air mass recirculation over Southern Africa. Streaker samples were analysed by PIXE for the usual crustal derived elements and sulphur. Sulphate aerosols over southern Africa are produced in the atmosphere by oxidation of SO2, from industry, or DMS, from the ocean. Industrial related sulphate plays a key role in tracing long-range transport of anthropogenic pollutants.
We present results from selected monthly samples collected during 1996. Measured particulate sulphur has been apportioned between contributions from sea spray and non-sea salt sulphate (NSS) aerosols. Marine particulate sulphur, present in the regional background, was traced by its correlation with Na and Cl, which were routinely detected. The NSS content of these air masses was enriched with respect to the expected sea salt sulphur by two orders of magnitude. Al, Si, K, Ca, Ti and Fe, the major crustal elements, were measured only episodically with the occurrence of strong south-easterly winds. These winds are associated with wind blown dust from a mine located 4 km from the site.
These results are the first direct aerosol characterisation of the remote region of the western seaboard of southern Africa. Specifically the sulphur measurements at this site provide insights into relative contributions of natural DMS, industrial and sea salt contributions of particulate sulphate. 相似文献
The Cranfield University torpedo-shaped underwater vehicle has been modified to accommodate a laser stripe illumination system. As well as providing enhanced viewing capabilities, this system derives real-time navigational data during the mission and gathers images to produce a post mission enhanced optical waterfall image of a surveyed area.
This paper describes a preliminary set of constrained motion trials at the IFREMER wave basin in Brest, where the system was towed through the 50 m test tank at different altitudes and orientations whilst the true trajectory was measured. A comparison is made between ground truth trajectory generated from these external measurements and that derived from the video camera and rotation sensors internal to the vehicle. 相似文献
This paper presents a complete system for analyzing a vehicle׳s behavior in the context of real-time traffic video surveillance applications. To obtain the best possible results, it is fundamental to exploit the scene characteristics and the predefined traffic rules. For that purpose, an initial training step is performed that involves estimating the geometrical structure of the road, i.e., the depth relative to the camera, the vanishing points, the road areas itself, the road decomposition (into normal and forbidden traffic lanes or areas), the traffic rules, the typical vehicle trajectories and speeds, and the lane-changing rules. This process leads to a scene model, which is used together with a simple vehicle geometrical model during the vehicle detection, tracking and trajectory estimation phases to improve the robustness against the perspective and occlusion effects. Shadow effects are also accounted for during the moving object detection phase. Finally, this spatio-temporal analysis is used to obtain information that concerns the vehicles׳ behaviors. Experiments show that the information obtained is reliable and can be computed in real time. 相似文献
Despite improvements in vehicle design and safety technologies, frontal automotive collisions continue to result in a substantial number of injuries and fatalities each year. Although a considerable amount of research has been performed on PMHSs and ATDs, matched dynamic whole-body frontal testing with PMHSs and the current ATD aimed at quantifying both kinetic and kinematic data in a single controlled study is lacking in the literature. Therefore, a total of 4 dynamic matched frontal sled tests were performed with three male PMHSs and a Hybrid III 50th percentile male ATD (28.6 g, Δv = 40 kph). Each subject was restrained using a 4 kN load limiting, driver-side, 3-point seatbelt. Belt force was measured for the lap belt and shoulder belt. Reaction forces were measured at the seat pan, seat back, independent foot plates, and steering column. Linear head acceleration, angular head acceleration, and pelvic acceleration were measured for all subjects. Acceleration of C7, T7, T12, both femurs, and both tibias were also measured for the PMHSs. A Vicon motion analysis system, consisting of 12 MX-T20 2 megapixel cameras, was used to quantify subject 3D motion (±1 mm) at a rate of 1 kHz. Excursions of select anatomical regions were normalized to their respective initial positions and compared by test condition and between subject types. Notable discrepancies were observed in the responses of the PMHSs and the ATD. The reaction forces and belt loading for the ATD, particularly foot plate, seat back, steering column, and lap belt forces, were not in agreement with those of the PMHSs. The forward excursions of the ATD were consistently within those of the PMHSs with the exception of the left upper extremity. This could potentially be due to the known limitations of the Hybrid III ATD shoulder and chest. The results presented herein demonstrate that there are some limitations to the current Hybrid III ATD under the loading conditions evaluated in the current study. Overall, this study presents a comprehensive data set of belt forces, reaction forces, accelerations, and bilateral displacement data that can be used to evaluate the performance of ATDs and validate computational models. 相似文献
In this paper, we present a new approach to measuring the similarity between 3D-curves. Our approach allows the possibility of using strings, where each element is a vector rather than just a symbol. We present two different approaches for representing 3D-curves. One possibility is to represent a 3D-curve as two 2D-curves, one being the projection of the 3D-curve in the XY-plane, and the other one in the YZ-plane. For the case that we need geometric rotation invariance, we have used a second approach to the symbolic representation of the 3D-curve using the curvature and the tension as their symbolic representation. We validate this approach through experiments using synthetic and digitalized data. 相似文献