| 1. |
- Jiang, Xu, et al.
(author)
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Real-Time Scheduling and Analysis of Processing Chains on Multi-threaded Executor in ROS 2
- 2022
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In: 2022 IEEE Real-Time Systems Symposium (RTSS 2022). - : IEEE. - 9781665453462 - 9781665453479 ; , s. 27-39
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Conference paper (peer-reviewed)abstract
- ROS (Robot Operating System) is currently one of the most popular development frameworks for robotic software, which is usually subject to hard real-time constraints in safe-critical domains. Designers must formally model and analyze its timing behaviors to guarantee that real-time constraints are always honored at run-time. This paper studies real-time scheduling and analysis under a multi-threaded executor in ROS 2. We present a formal description of the scheduling model of multi-threaded executors, and develop response time analysis techniques for processing chains executing on it. Moreover, we identify a risk of increasing the response time of chains that may be caused by improper design when deploying systems on multi-threaded executors, which provides a useful guidance to designers. We conduct experiments with both randomly generated workloads and case studies on a realistic ROS 2 platform to evaluate and demonstrate our results.
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| 2. |
- Liagkouridis, Ioannis, et al.
(author)
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Physical-chemical properties and evaluative fate modelling of 'emerging' and 'novel' brominated and organophosphorus flame retardants in the indoor and outdoor environment
- 2015
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 524, s. 416-426
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Journal article (peer-reviewed)abstract
- Several groups of flame retardants (FRs) have entered the market in recent years as replacements for polybrominated diphenyl ethers (PBDEs), but little is known about their physical-chemical properties or their environmental transport and fate. Here we make best estimates of the physical-chemical properties and undertake evaluative modelling assessments (indoors and outdoors) for 35 so-called 'novel' and 'emerging' brominated flame retardants (BFRs) and 22 organophosphorus flame retardants (OPFRs). A QSPR (Quantitative Structure-Property Relationship) based technique is used to reduce uncertainty in physical-chemical properties and to aid property selection for modelling, but it is evident that more, high quality property data are required for improving future assessments. Evaluative modelling results show that many of the alternative FRs, mainly alternative BFRs and some of the halogenated OPFRs, behave similarly to the PBDEs both indoors and outdoors. These alternative FRs exhibit high overall persistence (Pov), long-range transport potential (LRTP) and POP-like behaviour and on that basis cannot be regarded as suitable replacements to PBDEs. A group of low molecular weight alternative BFRs and non-halogenated OPFRs show a potentially better environmental performance based on Pov and LRTP metrics. Results must be interpreted with caution though since there are significant uncertainties and limited data to allow for thorough model evaluation. Additional environmental parameters such as toxicity and bioaccumulative potential as well as functionality issues should be considered in an industrial substitution strategy.
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| 3. |
- Remouit, Flore, 1988-
(author)
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Underwater Electrical Connections and Remotely Operated Vehicles
- 2016
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Licentiate thesis (other academic/artistic)abstract
- Remotely Operated Vehicles (ROVs) are underwater robots that perform different kind of operations, from observation to heavier tasks like drilling, carrying and pulling cables, etc. Those ROVs are costly and require skilled personal to operate it as well as equipment for transportation and deployment (boats, cranes, etc.).The division for electricity at Uppsala University, is developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation that is located on the seabed, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.Cable connection is a big challenge in the project because the WEC concept is small and many units are necessary to create a rentable farm. Nowadays this operation is performed by divers but using Observation Class ROV (OCROV) could be an interesting alternative since they are affordable at lower costs and easier to operate. Cable connection is however a heavy task and requires force that an OCROV does not have. It will need a docking system from which the vehicle will take its force. It would then go to the station, dock itself to this support plate, grab the cables and connect them together. This procedure cannot be done by the ROV operator because it requires accurate displacement and quick adjustment of the robot’s behavior.An autopilot was created in Matlab Simulink that consists of three units: the path following, the ROV, and the positioning unit. The first one uses the vehicle’s position and computes the speed and heading to be applied on the ROV in order to guide it on the desired path. The second one contains a controller that will adapt the thrust of each propeller to the force needed to reach the desired heading and speed from the path following unit. It also contains the model of the ROV that computes its position and speed. The last unit consists of a Kalman filter that estimates the ROV position and will be used in case of delay or failure in the communication with the positioning sensors.The autopilot model is used with a positioning system that utilizes green lasers and image processing. Two green lasers are used as fixed points in each camera picture and from their distance on the image, the actual distance between the ROV and the docking platform can be computed. In addition, optical odometry is used. The idea behind is to estimate how the ROV is behaving by evaluating the changes between two pictures of the camera. Those two systems, laser and odometry, work together in order to get more accurate results.The laser system has so far been tested in air. The distance measurements gave interesting results with an error inferior to 3%, and angle measurements gave less than 10% error for a distance of one meter. One advantage with the system is that it gets more accurate as the vehicle gets closer to the docking point.In addition to the ROV project, a review study was conducted on the variability of wave energy compared with other resources such as tidal, solar, and wind power. An analysis of the different tools and models that are used to forecast the power generation of those sources was done. There is a need for collaboration between the different areas because the future will aggregate those different sources to the grid and requires a unification of the models and methods.
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| 4. |
- Zheng, Jie Sharon, et al.
(author)
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Unequal Directivity Orders Between Two Figure-8 Sensors Perpendicularly Colocated with a Pressure Sensor – Their “Spatial Matched Filter” Beam Steering
- 2024
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In: IEEE Transactions on Aerospace and Electronic Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9251 .- 1557-9603.
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Journal article (peer-reviewed)abstract
- Unequal “directivity orders” between two figure8 directional microphones/hydrophones are proposed and analyzed in this paper for beamforming. Specifically, two figure 8 sensors here, possibly of different “directivity orders”, are (i) orthogonally oriented to facilitate spatial filtering in both the azimuth and the elevation, and (ii) spatially colocated with an isotropic sensor (thereby decoupling the incident source's azimuth-elevation-radial dimensions from the impinging signal's time-frequency dimensions). This versatility (in the sensors’ diverse “directivity orders”) contrasts with all prior open literature on beamforming using a colocated triad of possibly directional sensors. Instead, this paper analytically explores how unequal directivity orders between two perpendicularly colocated figure-8 acoustic sensors would affect the triad array's “spatial matched filter” beam steering. The resulting “actionable” insights show which directivity-order combinations allow the beam of full maneuverability toward any azimuthal direction, and which directivity-order combinations only partial maneuverability.
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