A New Multidimensional Repulsive Potential Field to Avoid Obstacles by Nonholonomic UAVs in Dynamic Environments

The ability of autonomous flight with obstacle avoidance should be a fundamental feature of all modern unmanned aerial vehicles (UAVs). The complexity and difficulty of such a task, however, significantly increase in cases combining moving obstacles and nonholonomic UAVs. Additionally, since they assume the symmetrical distribution of repulsive forces around obstacles, traditional repulsive potential fields are not well suited for nonholonomic vehicles. The limited maneuverability of these types of UAVs, including fixed-wing aircraft, requires consideration not only of their relative position, but also their speed as well as the direction in which the obstacles are moving. To address this issue, the following work presents a novel multidimensional repulsive potential field dedicated to nonholonomic UAVs. This field generates forces that repulse the UAV not from the obstacle’s geometrical center, but from areas immediately behind and in front of it located along a line defined by the obstacle’s velocity vector. The strength of the repulsive force depends on the UAV’s distance to the line representing the obstacle’s movement direction, distance to the obstacle along that line, and the relative speed between the UAV and the obstacle projected to the line, making the proposed repulsive potential field multidimensional. Numerical simulations presented within the paper prove the effectiveness of the proposed novel repulsive potential field in controlling the flight of nonholonomic UAVs.

Implementation of QR Code Recognition Technology Using Smartphone Camera for Indoor Positioning

Numerous studies on positioning technology are ongoing for recognizing the positions of objects accurately. Vision-, sensor-, and signal-based technologies are combined for recognizing the positions of objects outdoors and indoors. While positioning technologies involving wireless communication based on sensors and signals are commonly used in outdoor environments, the performance becomes degraded in indoor environments. Therefore, a vision-based indoor positioning method using a QR code is proposed in this study. A user’s position is measured by determining the current position of a smartphone device accurately based on the QR code recognized with a smartphone camera. The direction, distance, and position are acquired using the relationship between the three-dimensional spatial coordinate information of the camera and the center point coordinates of a two-dimensional planar QR code obtained through camera calibration.

Direction/Distance/Velocity Measurements Deeply Integrated Navigation for Venus Capture Period

In the Venus capture period, it is difficult for celestial autonomous navigation to satisfy the requirement of high precision. To improve autonomous navigation performance, a Direction, Distance and Velocity (DDV) measurements deeply integrated navigation method is proposed. The “deeply” integrated navigation reflects the fact that the direction and velocity measurements suppress the Doppler effects in the pulsar signals. In the pulsar observation period, the direction and velocity measurements are utilised to compensate for Doppler effects in the pulsar signals. By these means, the residual effects can be ignored. When the direction, distance or velocity measurements are obtained, they are fused to improve the navigation performance. Simulation results demonstrate that the DDV measurements deeply integrated navigation filter converges very well, and provides highly accurate position estimation without a high quality requirement on navigation sensors.

Determination of Heat and Flow Characteristics in Spray Cooling with Rectangular Finned Heat Sink

Spray cooling process has many parameters such as extended surface, angle of inclination, effect of gravity, diameter of nozzle, angle of spray, mass flux, geometry of cooled surface, thermal performance and critical heat flux of spray etc. Many effective parameters to carry out the experiments with conventional test methods are both expensive and time consuming. As a solution in these circumstances, Taguchi method, which is one of the modern experimental design and optimization methods and very effective in solving such problems, was used in this study. Taguchi method, as well as being in effective to improve the quality of products, also gives the opportunity to achieve better results with much less experiment. Using Taguchi method, as well as to reach the target value exactly, the sensitivity of the design against uncontrollable factors is reduced to a minimum. Thus, the optimum tolerance range in cost and quality factors is determined. When compared to conventional experimental design methods, Taguchi method has many advantages. One of them is that the test costs are minimized and the deviation around the target is kept to a minimum while in bringing targeted level of the average value of performance. Another advantage is that the obtained results in the laboratory can be obtained in the real production environment and also saved a time of production. Nowadays, the planning of the multi-factorial experiments can be provided with great flexibility and simplicity by Taguchi method. In these experiments with using rectangular pin fin heat sinks, the effects of the longitudinal and lateral distances of the consecutively arranged nozzle or diffuser-like fin pairs, widths of the fins, angle of fins, heights of fins, spraying time, air flow rate, liquid flow rate (ALR, the ratio of air-liquid flow rate) and the ratio of the nozzle-heat sink distance to the nozzle diameter (h/d) on heat and flow characteristics have been investigated by using Taguchi experimental design method. For this reason, characteristics of flow and heat transfer are considered separately. Nusselt number considered as performance statistic, L27(311) orthogonal array has been selected as an experimental design plan for the eleven parameters mentioned above. The Nusselt number was calculated by taking into account the characteristic length of heat sink and the optimized results were found to be fin width of 45 mm, fin angle of 45o, fin height of 15 mm, x direction distance between fins of 20 mm, y direction distance between fins of 20 mm, x direction distance between slices of 15 mm, y direction distances between slices of 20 mm, air flow rate of 10-3 m3/s, liquid flow rate of 5,83*10-6 m3/s, spraying time of 5 s and the ratio of the nozzle-heat sink distance to the nozzle diameter (h/d) of 667.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4596

Discussion on a New Calculation Method for Missing True Formation Thickness - A Case Study from YM32 Area in Northern Tarim Basin

The true formation thickness missed in the geologic borehole has important sense for understanding the strata of borehole and position of target layer. Nevertheless, there had not been enough effective technologies and calculation methods to calculate the missing true formation thickness at present. To solve this problem, this paper focuses on mathematical formula combining with the actual geological conditions, collects various useful geologic data and parameters, such as stratigraphic dip, dip direction, distance from drilling well to formation’s pinchout boundary along the dip direction and difference in height between drilling well and pinchout boundary, sets a reasonable calculation method, derives a complete set of new expression to calculate the missing true formation thicknesses. The typical region, YM32 Area in Tarim Basin, was taken as the case study to prove the accuracy and practicability of the calculation method. The result was inspected by the actual data of neighbor boreholes.