Showing papers by "Ivan Petrović published in 2006"

Constrained optimal control of an electronic throttle

Abstract: The overall vehicle performance is strongly influenced by the quality of the control of the electronic throttle – a DC motor driven valve that regulates the inflow of air to the vehicle's engine. Designing a controller for the throttle system is a challenging task since one has to cope with two strong non-linearities: the gearbox friction and the so-called “limp-home” non-linearity. In this paper we address these issues by solving a constrained optimal control problem formulated for the discrete-time piecewise affine (PWA) model of the throttle. In an off-line, dynamic programming procedure we obtain the look-up table like solution to the optimal control problem. Such a solution allows the real-time controller implementation that would otherwise be impossible to achieve due to the small sampling time needed for the application at hand. We address the issue of the PWA friction modelling in more detail by considering both static and dynamic friction models. Two different control strategies are studied: cons...

Tensor Product Model Transformation-based Controller Design for Gantry Crane Control System – An Application Approach

Abstract: The Tensor Product (TP) model transformation is a recently proposed technique for transforming given Linear Parameter Varying (LPV) state-space models into polytopic model form, namely, to parameter varying convex combination of Linear Time Invariant (LTI) systems. The main advantage of the TP model transformation is that it is executable in a few minutes and the Linear Matrix Inequality (LMI)-based control design frameworks can immediately be applied to the resulting polytopc models to yield controllers with tractable and guaranteed performance. Various applications of the TP model transformation-based design were studied via academic complex and benchmark problems, but no real experimental environment-based study was published. Thus, the main objective of this paper is to study how the TP model transformation performs in a real world problem and control setup. The laboratory concept for TP model-based controller design, simulation and real time running on an electromechanical system is presented. Development system for TP model-based controller with one hardware/software platform and target system with real-time hardware/ software support are connected in the unique system. Proposed system is based on microprocessor of personal computer (PC) for simulation and software development as well as for real-time control. Control algorithm, designed and simulated in MATLAB/SIMULINK environment, use graphically oriented software interface for real-time code generation. Some specific conflicting industrial tasks in real industrial crane application, such as fast load positioning control and load swing angle minimization, are considered and compared with other controller types.

Discrete-Time Sliding Mode Control of Load Frequency in Power Systems with Input Delay

Abstract: This paper presents a new approach for load-frequency control in large scale power systems. The method uses only samples of area control error signals from which it estimates all states and disturbances in the system. Predictor is used to compensate for the time delay in control signal. A novel approach for designing a sliding surface is presented. Simulation results of three-area power system using designed controller are shown.

Identification of Wind Turbine Model for Controller Design

Abstract: Wind power increases rapidly with increase of wind speed. In order to keep wind turbin running even at strong winds wind power capture has to be constrained. Efficient way for constraining wind power capture is the use of pitchable blades. For pitch controller design a suitable wind turbine model is needed. Finding mathematical model that would be a good representation of wind turbine system and at the same time suitable for controller design is very difficult task since wind turbine system is strongly nonlinear. Description of wind turbine system using many linear models identified at particular operating points is explored in this paper. Effects occurring when switching between models are examined and their repercussions on controller design are discussed. Use of fuzzy logic is proposed as possible solution for avoiding negative effects caused by switching between models.

AMORsim - A Mobile Robot Simulator for Matlab

Abstract: In the development of mobile robot control algorithms the researchers are often faced with the problem of ensuring safety operation of used mobile robot during the real mobile robot experiment phase. For this reason implemented control algorithms have to be firstly tested in various simulation scenarios. Appropriate simulation tools have to enable easy creation of different simulation setups, usage of different sensors, collection and evaluation of sensor measurements, examination of noise influence, etc. This paper describes a developed simulation tool for such a purpose – AMORsim (Autonomous MObile Robots simulator), a mobile robot simulator that’ s able to simulate a three-wheeled user-defined mobile robot in a two-dimensional environment. It’ s written in Matlab, which is a common, and well-known simulation environment.

An Algorithm for Deadlock Prevention Based on Iterative Siphon Control of Petri Net

Abstract: This paper presents a formal calculation method of a deadlock prevention supervisor by the use of Petri nets. The proposed algorithm uses reachability tree to detect deadlock state and iterative siphon control method to synthesize the deadlock prevention supervisor. Such supervisor is maximally permissive and consists of minimal number of control places. The algorithm is intended for reversible or partially reversible P-T Petri net, but it can also be applied to Ordinary Petri nets. The calculation of the supervisor is illustrated by two examples. The first example shows the synthesis of deadlock prevention supervisor in a manufacturing system consisting of three conveyors and three robots, where the deadlock can occur due to concurrent requests of the conveyors for the robot engagements and unpredictable duration of those engagements. The second example shows the synthesis of deadlock prevention supervisor in a marine traffic system, where dangerous vessel deadlock situations may occur in case of vessels’ irregular motion through the system. To avoid this, the vessel traffic is supervised and controlled by traffic lights using the deadlock prevention supervisor, which is responsible for vessels’ stopping only in the case of dangerous situation and until this situation elapses.

Global Vision Based Tracking of Multiple Mobile Robots

Abstract: This paper presents a global vision system for tracking of multiple mobile robots as a part of intelligent space, with special emphasis on the following requirements: (i) the system must have the ability to track unlimited number of robots using images from one or more cameras, (ii) the system must have acceptable price, and (iii) the system must operate in real time, so algorithms with lower computational cost are preferred. In order to fulfill these requirements we used an IEEE 1394 camera with 80 fps, which delivers the image in so called Bayer format. We also designed a specific robot identification mark which enables measurement of robot locations directly in Bayer format image. In this way computational complexity was significantly reduced. Experimental testing demonstrated robust behavior of developed global vision system.

Parquet Sorting and Grading Based on Color and Texture Analyses

Abstract: In this paper a computer vision algorithm for automatic parquet slab sorting is described, as a part of a real time automatic parquet slab sorting system. Various computer vision algorithms and methods for automatic visual inspection and automatic classification have been analyzed. Developed algorithm consists of three main stages: color analysis, texture analysis and defects detection. The color analysis is based on the percentile values obtained from the cumulative histogram of the image and texture analysis is based on the second order statistical features obtained from gray level co-occurrence matrix. Detection of defects is implemented as the segmentation method, based on the adaptive binary threshold algorithm, which is based on a local square regions and connected component analysis methods. This way we have achieved a very accurate classifying process with about 90 percent of accuracy, which greatly outstands results of human inspector, that are about 60-70 percent.

Mobile Robot Localization Using Local Occupancy Grid Maps Transformations

Abstract: Mobile robot localization is the problem of determining the pose (position and orientation) of a mobile robot under complex measurement uncertainties. The algorithm introduced here is based on the modified multiple model and exploits a soft gating of the measurements to reduce the computational requirements of the approach. The position part is based on an x and y histograms scan matching procedure, where x and y histograms are extracted directly from local occupancy grid maps using probability scalar transformation. The orientation part is based on the proposed obstacle vector transformation combined with polar histograms. Proposed algorithms are tested using a Pioneer 2DX mobile robot.

Wind turbine control system

Abstract: U uvjetima kada vjetroelektrane postaju sve važniji cimbenici EES-a javlja se potreba za vrlo pouzdanim radom vjetroagregata. Zbog toga vjetroagregati moraju biti opremljeni sofisticiranim sustavom upravljanja koji je u stanju voditi vjetroagregat kroz vrlo razlicite pogonske uvjete određene vremenskim prilikama. U ovom su radu opisane glavne znacajke sustava upravljanja suvremenih komercijalnih vjetroagregata u klasi snage reda 1 MW. Poseban naglasak stavljen je na upravljanje brzinom vrtnje i snagom generatora. Također je istaknuta velika interakcija sustava upravljanja s konstrukcijom sustava te specificnosti projektiranja sustava vjetroagregata koje iz toga proizlaze.

Vision system design for accurate pose tracking of multiple mobile robots

Abstract: This paper presents a global vision system for tracking of multiple mobile robots, with special emphasis on the following requirements: (i) the system must have the ability to track unlimited number of robots using images from one or more cameras, (ii) the system must operate in real time, and (iii) the system must have acceptable price. In order to fulfill these requirements we used an IEEE 1394 camera with 80 fps, which delivers the image in so called Bayer format. We also designed a specific robot mark which enables measurement of robot locations directly in Bayer format image. In this way computational complexity was significantly reduced. Experimental testing demonstrated robust behavior of developed global vision system.

Praćenje mobilnih robota korištenjem računalnog vida

Abstract: In this paper a global vision scheme applied to a fast dynamic game robot soccer is presented. The process of robots positions and orientations estimation is divided into two steps. In the first step, the Bayer format image is acquired from camera, then the RGB image is interpolated and pixels are classified into a finite number of classes. At the same time, a segmentation algorithm is used to find corresponding regions belonging to one of the classes. In the second step, all the regions are examined. Selection of the ones that are parts of the observed object is made by means of simple logic procedures. A data filtering is used to improve identified noisy data. The novelty is focused on the optimization of the image acquisition algorithm as well as the processing time needed to finish the estimation of possible object positions.

Localisation of Mobile Robots by Tracking Identical Colour Markers

Abstract: A reliable tracking algorithm of multiple mobile robots is addressed in this paper. A central vision system is used to find robots in the environment where robots are marked with identical colour patches mounted on each of them. To distinguish robots a robust tracking algorithm considering robot kinematics is implemented. However, mistakes such as swaps of robots identifications can happen and are unrecoverable, resulting in wrong control. Therefore swaps of robots identifications and initialisation problems are tackled using a supervision algorithm which is based on the correlation of command, and estimated robots velocities.