Set Of Possible Directions Research Articles

Collision-free path planning for multiple robots using efficient turn-angle assignment

The ability to avoid collisions with moving robots is critical in many applications. Moreover, if the robots have limited battery life, the goal is not only to avoid collisions but also to design efficient trajectories in terms of energy consumption and total mission time. This paper proposes a novel strategy for assigning turn angles for collision-free path planning in scenarios where a small team of robots cooperate in a certain mission. The algorithm allows each robot to reach a predetermined destination safely. It establishes consecutive, short time intervals, and at each interval, possible conflicts are solved centrally in an optimal manner. This is done by keeping constant speeds but generating a discrete set of possible directions for each robot, and solving efficiently the turn-angle allocation for a collision-free path that minimizes the path deviation from the shortest one. Due to the discretization, the final paths are not optimal, but the system can react to possible failures during execution, as conflicts are resolved at each time interval. Computational results and Software-In-The-Loop simulations are presented in order to evaluate the proposed algorithm. A comparison with a state-of-the-art approach shows that our algorithm is more energy-efficient and achieves lower mission completion time.

Produkcja oraz rynek rzepaku na Ukrainie i jego perspektywy

The paper presents the main aspects of rapeseed production and processing in Ukraine in the context of Ukraine’s joining EU. Current situation of rapeseed market and some aspects of exporting activity in this sphere were characterized. A set of possible directions of development of the situation in Ukraine including possible influences of UE’s policy in the sphere of alternative energy sources were presented, as well as changes of volumes of rape production. The paper also analyses the activity of Ukrainian government connected to the rapeseed production and processing, including avoidance of possible pathological Ukraine’s transformation into mere Europe’s raw materials’ supplier.

Growth model on (1 + 1) dimensions with local relaxation and discrete number of orientations

We introduced in this work a simple model for studying the texture formation during the electrodeposition process. Monte Carlo simulations were used to describe the formation of the deposits, and scaling concepts were also employed to characterize their growth and roughness properties. Particles are randomly deposited on a substrate, and their main axis can be aligned in a discrete set of possible directions. The final orientation of the deposited particle is determined by the interaction energy with its first neighboring particles and substrate temperature. Particle interactions are chosen according to the q-state ferromagnetic Potts model hamiltonian. Simulations were performed on (1 + 1) dimensions, for different values of temperature and substrate size. We have found different behaviors at low and high temperatures. Only at zero temperature the system reaches an absorbing state with all the layers occupied by particles oriented in the same direction. At this temperature we found the dynamic, roughness and growth exponents of the model, which satisfies the well known Family–Vicsek scaling relation for the self-affine interfaces. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A simplified interferometer design for use with meteor radars

A relatively simple design for a meteor radar interferometer with 4 receiving antennas is described. A basic 3 element interferometer provides a set of possible directions for each radio echo detected. The ambiguity is resolved using a 4th antenna, placed according to the results of a numerical simulation. Details of the procedure are provided. The resolution in echo direction is between ∼1° and ∼2° for altitudes (elevations) above ∼30° at all azimuths. A general purpose meteor radar based on this principle has been in use since 1986 at Grahamstown, South Africa.

Growth model with a finite number of orientations on a linear substrate.

The aim of this work is to present a simple model for studying the texture formation during the electrodeposition process. Monte Carlo simulations are used to describe the formation of the deposits, and the scaling concepts are employed to characterize their growth and roughness properties. In this model particles are randomly deposited with an orientation chosen from a discrete set of possible directions. The final orientation of the deposited particle is determined by its interaction with the first neighboring particles and by the temperature of the substrate. Particle interactions are chosen according to the q-state ferromagnetic Potts model Hamiltonian. Simulations were performed on (1+1) dimensions, and for several values of temperature and substrate size. The results of the simulations lead to different behaviors for the model at low and high temperatures. At high temperatures, the scaling exponent beta=0.5 was found, which characterizes a pure random deposition model. However, at low temperatures, we observed that after a given time interval, particles start orienting in a fixed direction and the interface width saturates just during a time window. Suddenly, a fluctuation makes the interface width increase again, that is, we never observed a full saturation. On the other hand, at zero temperature, the system reaches an absorbing state with all the layers occupied by particles oriented in the same direction. At zero temperature we found z=1.90, alpha=1.80, and beta=0.99 for the dynamic, roughness, and growth exponents, respectively. The scaling exponents are consistent with a self-affine behavior of the model and they are in agreement with the well known Family-Vicsek scaling relation.

A new approach to orientation workspace analysis of 6-DOF parallel manipulators

This paper presents a new discretization method for the computation of the orientation workspace of 6-DOF parallel manipulators, defined as the set of all attainable orientations of the mobile platform about a fixed point. The method is based on the use of a modified set of Euler angles and a particular representation of the orientation workspace. In addition, the projected orientation workspace is introduced for use in 5-axis applications, defined as the set of possible directions of the approach vector of the mobile platform. Alternative ways of computing these two types of workspaces are also discussed.