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1

Application of predictive control for manipulator mounted on a satellite

Rybus T., Seweryn K., Sąsiadek J. Z.

Archives of Control Sciences

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2018

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Vol. 28, No. 1

105--118

EN

Specific conditions of on-orbit environment are taken into account in the design of all devices intended to be used in space. Despite this fact malfunctions of satellites occur and sometimes lead to shortening of the satellite operational lifetime. It is considered to use unmanned servicing satellite, that could perform repairs of other satellites. Such satellites equipped with a manipulator, could be used to capture and remove from orbit large space debris. The critical part of planned missions is the capture manoeuvre. In this paper a concept of the control system for the manipulator mounted on the satellite is presented. This control system is composed of the trajectory planning module and model predictive controller (the latter is responsible for ensuring precise realization of the planned trajectory). Numerical simulations performed for the simplified planar case with a 2 DoF manipulator show that the results obtained with the predictive control are better than the results obtained with adaptive control method.

2

Simulation-based sailboat trajectory optimization using on-board heterogeneous computers

Dębski R.

Computer Science

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2016

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Vol. 17 (4)

461--481

EN

A dynamic programming-based algorithm adapted to on-board heterogeneous computers for simulation-based trajectory optimization was studied in the context of high-performance sailing. The algorithm can efficiently utilize all OpenCL-capable devices, starting the computation (if necessary, in single precision) on a GPU and finalizing it (if necessary, in double-precision) with the use of a CPU. The serial and parallel versions of the algorithm are presented in detail. Possible extensions of the basic algorithm are also described. The experimental results show that contemporary heterogeneous on-board/mobile computers can be treated as micro HPC platforms. They offer high performance (the OpenCL-capable GPU was found to accelerate the optimization routine 41 fold) while remaining energy and cost efficient. The simulation-based approach has the potential to give very accurate results, as the mathematical model upon which the simulator is based may be as complex as required. The black-box represented performance measure and the use of OpenCL make the presented approach applicable to many trajectory optimization problems.

3

Gradient-Based Algorithms in the Brachistochrone Problem Having a Black-Box Represented Mathematical Model

Dębski R.

Journal of Telecommunications and Information Technology

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2014

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nr 1

32--40

EN

Trajectory optimization problems with black-box represented objective functions are often solved with the use of some meta-heuristic algorithms. The aim of this paper is to show that gradient-based algorithms, when applied correctly, can be effective for such problems as well. One of the key aspects of successful application is choosing, in the search space, a basis appropriate for the problem. In an experiment to demonstrate this, three simple adaptations of gradient-based algorithms were executed in the forty-dimensional search space to solve the brachistochrone problem having a blackbox represented mathematical model. This experiment was repeated for two different bases spanning the search space. The best of the algorithms, despite its very basic implementation, needed only about 100 iterations to find very accurate solutions. 100 iterations means about 2000 objective functional evaluations (simulations). This corresponds to about 20 iterations of a typical evolutionary algorithm, e.g. ES(μ,l ).

4

High-performance simulation-based algorithms for an alpine ski racer’s trajectory optimization in heterogeneous computer systems

Dębski R.

International Journal of Applied Mathematics and Computer Science

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2014

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Vol. 24, no. 3

551--566

EN

Effective, simulation-based trajectory optimization algorithms adapted to heterogeneous computers are studied with reference to the problem taken from alpine ski racing (the presented solution is probably the most general one published so far). The key idea behind these algorithms is to use a grid-based discretization scheme to transform the continuous optimization problem into a search problem over a specially constructed finite graph, and then to apply dynamic programming to find an approximation of the global solution. In the analyzed example it is the minimum-time ski line, represented as a piecewise-linear function (a method of elimination of unfeasible solutions is proposed). Serial and parallel versions of the basic optimization algorithm are presented in detail (pseudo-code, time and memory complexity). Possible extensions of the basic algorithm are also described. The implementation of these algorithms is based on OpenCL. The included experimental results show that contemporary heterogeneous computers can be treated as μ-HPC platforms—they offer high performance (the best speedup was equal to 128) while remaining energy and cost efficient (which is crucial in embedded systems, e.g., trajectory planners of autonomous robots). The presented algorithms can be applied to many trajectory optimization problems, including those having a black-box represented performance measure.

5

System wyznaczania ścieżek przemieszczeń dla grupy autonomicznych mobilnych robotów-agentów rozpoznawczo-inspekcyjnych

Szatkiewicz T.

Pomiary Automatyka Kontrola

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2013

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R. 59, nr 11

1155--1159

PL

W artykule opisano oryginalny system wieloagentowy, którego podstawowym celem jest rozpoznanie, a następnie przeprowadzanie inspekcji nieznanego obszaru przy wykorzystaniu grupy autonomicznych mobilnych robotów-agentów. Wnioski z przeprowadzonych symulacji systemu pozwalają na rozpoznanie obszaru wiedzy, dotyczącego szczególnych aspektów systemów wieloagentowych takich jak min: metody ustalania ścieżek przemieszczeń agentów mobilnych czy wpływ liczby agentów na globalną efektywność systemu.

EN

The paper describes an original multi-agent system [1, 2, 10, 11] whose primary purpose is to recognize and, subsequently, to inspect continuously a limited area. The agents are autonomous mobile robots, equipped with a set of sensors that are capable of scanning the examined area and collecting information on significant features. The main decision problem necessary to be solved in the system is to determine the paths for the robotic agents in such a way that the area is recognized in the shortest time, and the inspection process is the most effective from the point of view of the state of knowledge about the significant features of the examined area. The agents should act collectively in such a way as to balance their load and, hence, to optimize the system performance. In the paper there are described in detail the consecutive steps of the algorithm (Fig. 1), and, in particular, the methodology for determining the direction of motion of robotic agents (Subsections 5.3 and 5.4). The presented multi-agent system was implemented in the Webots environment [4]. Educational robots of the e-puck class were used as robots-agents (Fig. 2), [3]. Implementation of the system made it possible to perform a series of experiments which allowed drawing interesting conclusions (Section 6) on the effectiveness of the system in achieving its primary objectives. At the end of the paper the experiment is illustrated (Fig. 7), and also the growth chart of recognition of the area for each robotic agent is presented (Fig. 8).

6

Flight path optimization of an aircraft aided during take-off by maglev system

Majka A.

Journal of KONES

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2013

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Vol. 20, No. 2

261--268

EN

Very high air traffic density in the largest airports and in their vicinity involves that the air traffic in the largest airports and their areas of operations approaches the capacity limits. Such high density of the air traffic adversely influences the natural environment in the vicinity of the airports due to the increasing cumulative noise level and the concentration of environmentally hazardous substances. One of the possibilities to improve the situation is to work out innovative solutions aimed at decreasing the aircraft pollution and improving the transport effectiveness. One of the major concepts is using magnetic levitation (MAGLEV) technology to support aircraft take-off and landing. If the aircraft could take-off and start the initial climb phase with the ground power, the installed power may be reduced, resulting in less weight, less drag and less overall fuel consumption which leads to emission reduction. These advantages, the lower fuel consumption and emissions, increase sustainability of the transportation system. Different conditions of the take-off give possibilities to shape the trajectory after the take-off in order to decrease the negative influence on the environment. The aim of the present work was to determine the optimal conditions of the take-off and the optimal climb trajectory of the aircraft aided in the ground phase of the take-off by the system using the MAGLEV technology, minimizing the fuel consumption. The simplified algorithm of optimization of the flight trajectory was used in this work; it uses the method of approximation of the flight path by the third degree polynomial.

7

Analysis and optimization of the spatial mechanism

Frantisek O., Szweda J., Poruba Z.

Modelling and Optimization of Physical Systems

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2010

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z. 9

21--28

EN

The paper deals with an analysis and an optimization of the truck shifting mechanisms. The aim of the work is to optimize the trajectory of a shifting lever hand-grip in order to obtain an acceptable ergonomic trajectory. A mathematical surrogate of the shifting mechanism has been constructed and the following use of the optimization algorithms resulted in several modifications of mechanism dimensions.

8

Time-optimal control of hydraulic manipulators with path constraints

Hołobut P.

Journal of Theoretical and Applied Mechanics

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2005

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Vol. 43 nr 3

523--538

EN

A method of optimization intended to speed up motions of non-redundant hydraulic manipulators along prescribed paths of their end-effectors is presented. A parametric path of the end-effector of a non-redundant manipulator determines the corresponding path in the manipulator joint-space. The optimization problem therefore reduces to finding the optimum distribution of the parameter of the path in time. The proposed optimization scheme is based on discretization of the distribution of the parameter into a fixed number of points, and finding their optimum locations by methods of constrained nonlinear programming. Incompressibility of the hydraulic fluid is assumed throughout for greater effectiveness of the procedure. Results of sample optimizations performed on a three-link hydraulic excavator are presented.

PL

Praca przedstawia metodę optymalizacji minimalno-czasowej ruchów manipulatorów hydraulicznych, po zadanej ścieżce członu roboczego. Zakładane jest, że ścieżka członu roboczego jednoznacznie określa odpowiadającą jej ścieżkę manipulatora w zmiennych uogólnionych. Optymalizacja sprowadza się wówczas do znalezienia optymalnego rozkładu parametru ścieżki w czasie. Proponowana metoda optymalizacji polega na przybliżeniu ciągłego rozkładu parametru zbiorem punktów, a następnie znalezieniu ich optymalnych położeń metodami programowania nieliniowego z ograniczeniami. Zakładana jest przy tym nieściśliwość cieczy hydraulicznej, w celu przyspieszenia obliczeń. Załączone są wyniki przykładowych optymalizacji, wykonanych na modelu trójczłonowej koparki hydraulicznej.

9

Flying between obstacles - formulation and solution to the problem

Bunakov A., Grevtsov N., Efimov O., Melts I., Sazonov D., Tegin A.

Research Bulletin / Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics

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2001

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nr 11

29-39

EN

The paper presents a short description of two approaches to solving of the fly-around-obstacles problem. This problem consists in finding of a global optimal flying object trajectory or route for a flight over an area with obstacles of natural or artificial type. The trajectory length or fuel consumption is limited. The paper contains two parts corresponding to the combinatory and variational approaches, respectively.

10

Analysis of regular and singular solutions to the problem of aircraft optimal thrust control

Sazonov D.

Research Bulletin / Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics

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2001

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nr 12

73-78

EN

The paper deals with the problem of optimal thrust control for a given trajectory when flying through dangerous zones with obstacles. The obstacles are represented by the probability function that determines the level of safety of the mission or the probability of aircraft failure. The flight at a constant altitude is considered, along the rectilinear trajectories that correspond to the evolvent of curvilinear trajectories of small curvatures. The problem under consideration is the determination of optimal thrust that ensures the minimum of failure probability for the flight at a given distance with a limit imposed on fuel consumption. A solution to this problem is based on the maximum principle approach. The main difficulty of this problem consists in the existence of singular solutions. The accepted approach enables calculation of singular thrust control and appropriate trajectories in the phase space (velocity and range).