A Probabilistic Algorithm to Medium-Term Conflict Detection with Multi-Waypoints

The medium-term conflict detection (MTCD) field trials are an important part of EUROCONTROL's performance enhancement programme for European ATM (EATMP), which consists of 22 (sub)-programmes. One of them, automated support to air traffic services (ASA) programme 2, develops, prototypes, simulates and finally tests in live ATC environment new ATC decision support tools. The ASA programme is developing solutions for ATC challenges, such as complexity detection and management, sequencing and metering, and conflict detection and resolution. The main principle is layered planning; where complex traffic situations are detected and solved by re-routing or metering, and the remaining conflicts are detected and resolved with automation assistance. Use of air-ground integration is considered, as appropriate.

The method used in Austria for calculating building heating and cooling demand is a monthly quasi-steady-state calculation. This method is presented in the European draft ISO/FDIS 13790. The simplified monthly calculation method is based on utilization factors. For these factors there is no specific mathematical derivation. The factor is based on an empirical formula. For increasing the practicability of the simplified calculation methods, the precision of the method is important, as well as the prediction accuracy by modifying the building parameters. Both requirements for a simplified calculation method are verified in this investigation. A simplified investigation of the calculation method precision for the cooling demand for offices leads to a 40 percent margin of error when using the simplified method for Vienna climate. The prediction accuracy of the monthly balanced method for changing the building parameters was verified for a six zone office model. At the end, the precision of the simplified method was quantified for an office model for the heating and cooling demand. Safety factors for the simplified method resulted from the investigation of the office model. The imprecision of the simplified method is greater than the validation of the monthly calculation method, as is exposed in the draft ISO/FDIS 13790. For the cooling demand for Vienna, the safety factor is 1.25 for the one zone method and 1.15 for the multi-zone method. For the heating demand no safety factor is necessary if the simplified method is not used for low air change rates and uncoupled models.

A multilevel Bit Vector minimization method for fast online detection of conflicting flow entries in OpenFlow table

This paper introduces a real-time means to detect and avoid conflicts for a conceptual Free Flight environment. The assumption of this paper is approximately the same as the model given by Lee C.Yang of MIT. The concept assumes that the datalinks (e.g. ADS-B IN) between different aircraft are available and that conflicts are primarily resolved on the flight deck. This paper provides the flight crew multiple ways to avoid the conflicts, including turn, acceleration, deceleration, climb and descent. The alerting logic is based on probabilistic analysis through modeling of aircraft sensors and trajectory uncertainties. Monte Carlo simulations are used to determine conflict probability for every possible encounter situation. The construction of conflict probability database (CPDB) before the aircraft takes off can reduce the computation time of the flight computer. The CPDB records the conflict probability corresponding to every possible air traffic situation in which there are only two aircraft. Due to the integrity of the constructed CPDB, CPDB is suitable to be used to study the characters of the air traffic conflict. The Avoidance Maneuver Database (AMDB) and the Redundant Maneuver Database (RMDB) have been constructed based on the CPDB which is established in advance. AMDB and RMDB are used in resolving conflicts in multiple aircraft scenario.

For the safety problem of flight anti-collision in route area and terminal area, a flight conflict detection method is proposed based on Monte Carlo method. In the method, the ellipsoidal aircraft protection area model is selected and the position of aircraft is predicted through the stochastic differential equation, and then Monte Carlo method is used to calculate the probability of flight conflict in terminal area. The experiments show that the proposed method can obtain a more accurate overall flight conflict probability, thus verifying its feasibility in the application of conflict detection studies.

To support advanced network services, Internet routers must perform packet classification based on a set of rules called packet filters. If two or more filters overlap, a filter conflict will occur and lead to ambiguity in packet classification. Further, it may affect network security or even the correctness of packet routing. Hence, it is necessary to detect conflicts to avoid the above problems. In recent years, many conflict detection algorithms have been proposed, but most of them detect conflicts for only prefix fields (i.e., source/destination IP address fields) of filters. For greater practicality, conflict detection must include non-prefix fields such as source/destination IP port fields and the protocol field. In this study, we propose an efficient conflict detection algorithm for five-dimensional filters, which include both prefix and non-prefix fields. In the proposed algorithm, a tiny lookup table is created for quickly filtering out a large portion of non-conflicting filter pairs, thereby reducing the overall conflict detection time. Experimental results show that our algorithm reduces the detection time by 10% to 28% compared with other conflict detection algorithms for 20 K filter databases. More importantly, our algorithm can be used to extend any existing conflict detection algorithms for two-dimensional filters to support fast conflict detection for five-dimensional filters.

For the structural design of masonry according to Eurocode 6 with the associated German national annex, the simplified method and the further simplified calculation method in Annex A are available. These procedures provide tools that can be used in practice to design standard cases quickly and easily. One feature of the verification of masonry walls under compressive loading is that no bending moments in the walls have to be determined as part of the determination of section forces and moments since the verification of the load‐bearing capacity of the wall is based solely on the acting vertical force. The effects of floor end restraint and buckling are dealt with by simple equations. One new feature of verification according to Eurocode 6 is that the effect of partially supported floors on the load‐bearing capacity of the wall can be included directly. The code is compact and simple to use and the further simplified calculation method is predestined for verification by manual calculation.

Conflict detection algorithms can be broadly classified as state based and intent based algorithms. State based algorithms predict the path of aircraft by projecting their current position and velocity vectors. The path predictions are then used to determine if the aircraft are in conflict within a look ahead time. That is, if loss of separation occurs in the future. Intent based algorithm uses flight plans and other information, which usually resides in a flight management computer, to predict the path of aircraft. Algorithms that use intent information for conflict detection obtain the intent of other aircraft and broadcast their own intent via some type of communication link. Intent information that is exchanged among the aircraft is defined as explicit intent. A conflict detection algorithm can also make use of intent information based on aircraft nominal routes, corridors, published approaches, etc., and in this case, there is no information exchange between aircraft. This kind of intent is defined as implicit intent. Implicit intent can be used very effectively in conflict detection without the added cost and complexity of communication links. The use of implicit intent, in combination with state information, reduces false alarms over a state based conflict detection algorithm and therefore increases the effectiveness of the alerting system. In this paper, conflict detection using implicit intent information is described and its performance is compared with a state based conflict detection algorithm.

Stochastic optimal control for aircraft conflict resolution under wind uncertainty

This paper proposes a new traffic alert and collision avoidance system (TCAS) for general aviation (GA) that uses automatic dependent surveillance-broadcast (ADS-B). The proposed GA-TCAS alerts the pilot of upcoming potential conflicts, which are becoming increasingly common as the number of GA movements increases. Conflict detection and avoidance uses the ADS-B and GA maneuvers. The algorithm selects the angle according to the intruder’s heading and position in order to reduce the nuisance alerts. The detection algorithm has three stages: proximate advisory, traffic advisory, and resolution advisory. The relationship between the turn angle and the horizontal miss distance (HMD) are calculated to determine a resolution when an intruder enters the separation bubble. Using the encounter models for visual flight rule (VFR) to evaluate the performance of this TCAS algorithm, the resolution should follow the VFR and prioritize in different situations. In flight simulations, the proposed GA-TCAS is tested using real ultralight flight data. The system performance is demonstrated using flight trajectories from conflict detection and resolution.

In a distributed separation assurance system, each aircraft is equipped with its own conflict detection and resolution capability. An aircraft that is resolving an initial primary conflict has complete state information of all nearby aircraft, so is able to choose a resolution trajectory that is conflict-free from all other aircraft. However, because the update of state information is not instantaneous, it is possible that two distinct conflicts, if resolved in a near-simultaneous manner, may result in a downstream secondary conflict. Also an intent error in the state information may lead to a potential secondary conflict. This paper presents a methodology and sample results to analyze the frequency of potential secondary conflicts using output from a NAS-wide simulation. The events considered are not secondary conflicts themselves, but rather potential secondary conflicts, or situations in which there is an increased likelihood of a secondary conflict.

4D-trajectory based operations is one of the big enabler for future high-capacity, efficient and environmentally friendly air traffic management. Every aircraft is scheduled to fly along a predicted 4D path that can be calculated from gate to gate pre-flight. 4D trajectories are optimized individually for aircraft taking into account performance models, routes, weather conditions and airline preferences. However, individual calculation of trajectories does not ensure conflict-freeness with surrounding traffic. This work describes an efficient algorithm detecting conflicts for large traffic scenarios. Conflict detection is performed between aircraft trajectories, also taking into account environmental constraints like severe weather zones and restricted areas. Basic idea is an N-dimensional bisection of airspace allowing a significant reduction of complexity. Thus, potential conflicts are identified very fast. A slower high precision conflict check is performed on potential conflicts only. On average, conflicts of one 4D-trajectory can be detected in a European traffic sample holding more than 33 000 flights in less than 2.5 ms on standard PC hardware. Fast detection times are predestined for trial-and-error conflict resolution. Different conflict resolution methods are illustrated, taking into account the major key performance areas in air traffic management, e. g., safety, efficiency, and predictability. As an example, deconfliction is performed on an optimized version of aforementioned European traffic sample holding 33 000 flights.

Purpose. A simplified calculation method development for strengthened split cylindrical drum structures of the mine hoisting machines of the TsR-6.756.2/1.95 type. Methodology. The drum structure for the mine hoisting machines is conventionally divided into several nodes. A simplified averaged model is constructed for the nodes consisting of the shell, frontal, rib strengthening and brake discs (end nodes) based on the analysis of their operation, in particular, the stiffness analysis under different loads. After that, when assembling, the initial drum nodes are replaced with simplified ones and a so-called simplified model for the whole drum is constructed, as well as the displacements of the brake disc edges are determined. Findings. The simplified models for drum nodes have been created based on the analysis of their operation, and then the displacements of the whole drum simplified model have been calculated. Originality. The simplified calculation method error has been estimated: the method of averaging with increased thickness of the frontals. Practical value. For the TsR-6.756.2/1.95 hoisting machine with a drum diameter of 6750 mm, a drum width of 6200 mm and an adjustable part width of 1950 mm, with a groove cutting pitch of 51 mm and a maximum lifting depth of 1477 m, it has been determined that the maximum axial displacements for brake disc edges of the jammed and adjustable parts are 0.854 and 1.921mm, respectively. A simplified calculation method has been developed for strengthened split cylindrical drum structures of the mine hoisting machines of the TsR-6.756.2/1.95 type, available for use in middle-class packages such as SolidWorks Simulation.

1. To predict the depth of a scour depression at the toe of a protected concave bank of a meander in gravel-pebble channels and to determine the rate of this scouring, a simplified calculation method was developed on the basis of analyzing the results of calculation by the complete method of the Institute of Fluid Mechanics, Academy of Science of the Ukrainian SSR. 2. The main conditions making it possible to use the simplified calculation method are: disregard of the balance of the bed load and the nonuniformity of the flow in the scour depression at the protected concave bank of meanders. To perform the calculation it is necessary to have the value of the average slope of the free surface of the water on the axis of the flow, which is assumed constant during deformation of the bottom of the meander. 3. In the calculation one determines the vertically averaged velocity of the nonuniform flow u2 and the friction velocity u*2 in the scour depression, which must be compared with the friction velocity u*p corresponding to the detachment of the erosion pavement of inhomogeneous soil composing the bottom of the meander. By assigning various values of deepening of the bottom Δzb in the scour depression, one finds the value of Δzb for which scouring of the bottom ceases (u*2=U*p). 4. To check whether the calculated deepening of the bottom can occur during the duration of the calcualted flood on the basis of the value of the bed-load discharge calculated by means of Einstein's graph, the rate of deepening of the bottom in the scour depression is determined with the use of the method given in [1] for this purpose. 5. The reliability of the recommended simplified calculation method is confirmed by the results of comparing the calculated and experimental values.

China has been gradually relaxing its ban on the use of low-altitude airspace across the country. To guarantee the high reliability of air traffic management (ATM), conflict detection and conflict resolution (CDR) approaches are indispensable to maintain safe separation between neighbouring small fixed-wing aircraft. In this study, we analyse a temporal and spatial integrated strategy for safety assessment purposes in opening the low-altitude urban airspace of Chinese pilot cities. First, we present a detailed mathematical description of the proposed algorithms based on a spatial grid partitioning system (SGPS). For our system, a conflict detection (CD) algorithm is designed to determine if two trajectories pass through the same grid space within overlapping time windows. A conflict resolution (CR) algorithm integrates a proposed time scheduling-based technique (TST) and vertical change-based technique (VCT), which operate under predetermined basic principles. Then, based on our novel CDR algorithms, a causal model is constructed in graphical modelling and analysis software (GMAS) to generate a state space that can provide a global perspective on scenario dynamics and better understanding of induced conflict occurrences. Finally, simulation results demonstrate that the proposed approach is practical and efficient.