Branislava Perunicic

A 3-level autonomous mobile robot navigation system designed by using reasoning/search approaches

This paper describes how soft computing methodologies such as fuzzy logic, genetic algorithms and the Dempster-Shafer theory of evidence can be applied in a mobile robot navigation system. The navigation system that is considered has three navigation subsystems. The lower-level subsystem deals with the control of linear and angular volocities using a multivariable PI controller described with a full matrix. The position control of the mobile robot is at a medium level and is nonlinear. The nonlinear control design is implemented by a backstepping algorithm whose parameters are adjusted by a genetic algorithm. We propose a new extension of the controller mentioned, in order to rapidly decrease the control torques needed to achieve the desired position and orientation of the mobile robot. The high-level subsystem uses fuzzy logic and the Dempster-Shafer evidence theory to design a fusion of sensor data, map building, and path planning tasks. The fuzzy/evidence navigation based on the building of a local map, represented as an occupancy grid, with the time update is proven to be suitable for real-time applications. The path planning algorithm is based on a modified potential field method. In this algorithm, the fuzzy rules for selecting the relevant obstacles for robot motion are introduced. Also, suitable steps are taken to pull the robot out of the local minima. Particular attention is paid to detection of the robots trapped state and its avoidance. One of the main issues in this paper is to reduce the complexity of planning algorithms and minimize the cost of the search. The performance of the proposed system is investigated using a dynamic model of a mobile robot. Simulation results show a good quality of position tracking capabilities and obstacle avoidance behavior of the mobile robot.

Reduction of Control Torques of Mobile Robot Using Hybrid Nonlinear Position Controller

We have previously developed a mobile robot position controller based on backstepping control algorithm. In this paper, we propose the extension of mentioned controller with an aim to rapidly decrease the control torques needed to achieve the desired position and orientation of mobile robot. The parameters of this controller are adjusted by genetic algorithm. The same genetic algorithm was used for evolution of the control parameters of a multivariable PI velocity controller described with a full matrix. The performance of the proposed system is investigated using a dynamic model of a nonholonomic mobile robot with friction. Simulation results show the good quality of both velocity and position tracking capabilities of a mobile robot

Direct Power Control for various topologies of three phase grid-connected Voltage Sources Converters using Sliding Mode Control

This paper presents a new approach to Direct Power Control (DPC) strategy using Space Vector Modulation (SVM) for the three-phase grid connected Voltage Source Converter (VSC) in the Renewable Energy Sources (RESs). The proposed DPC strategy is based on the Sliding Mode Control (SMC) and it is implemented in the dq reference frame. The active and reactive powers are directly controlled by VSC switching states selection based on the instantaneous value of the delivered power error. This strategy may be implemented to various VSC topologies. Moreover, linear controllers and modulators are not necessary. The aim of the control strategy is to inject maximal available active power and a controlled amount of reactive power into grid. The strategy is tested on a simulation model of a multilevel VSC (ML-VSC). Simulation results of the tested VSC topology and harmonic analysis of the output signals are presented at the end.

Parametric identification of plants with multiple delays and internal feedbacks using genetic algorithm

This paper proposes a procedure for parametric identification of plants having multiple sources of the pure time delays and internal feedbacks, which are extremely complicated for the identification. The procedure is based on a genetic algorithm applied to the samples of the frequency response on the plant.

New Concept of the Fast Reactive Mobile Robot Navigation Using Pruning of Relevant Obstacles

The goal of this paper is to develop an approach to increase the mobile robot navigation speed in an a priori unknown environment. The overall navigation system consists of three navigation subsystems. The lower level subsystem deals with the control of the linear and angular volocities using a multivariable PI controller described with a full matrix. The position control of the mobile robot represents the medium level control, which is implemented by a backstepping algorithm whose parameters are adjusted by a genetic algorithm. The high level subsystem uses Dempster-Shafer evidence theory to design the fusion of sensor data and map building processes. Path planning algorithm is based on the modificated potential field method. In this algorithm, the fuzzy rules for selecting the relevant obstacles for robot motion are introduced. The performance of the proposed system is investigated using a dynamic model of a mobile robot with various frictions.

NIDS based on payload word frequencies and anomaly of transitions

This paper presents a novel payload analysis method. Consecutive bytes are separated by boundary symbols and defined as words. The frequencies of word appearance and word to word transitions are used to build a model of normal behavior. A simple anomaly score calculation is designed for fast attack detection. The method was tested using real traffic and recent attacks to demonstrate that it can be used in IDS. Tolerance to small number of attack in training data is shown.

A Simple Extension of Ziegler-Nichols’ Method Based on Damped Oscillations

This paper proposes a simple extension of the well-known Ziegler-Nichols’ (ZN) method. As in the standard ZN method, the experiment may be performed using the controller only, without any extra equipment. But, in opposite to the ZN method, the experiment may be performed using damped oscillations. Also, the proposed method allows more complex models of the plant, so a better tuning may be obtained.

A new discrete-time super twisting control of a first order plant with input saturation

Many real dynamical processes in control engineering practice can be modelled as a first order plant with saturation at its input. This paper proposes a new solution to control such plants, which is a combination of discrete-time first-order sliding mode (SM) control and discrete-time realization of super twisting control algorithm (STA) that is commonly used in second-order SM. A brief mathematical foundation of the proposed controller is given and then demonstrated in induction motor (IM) speed control as an example. A comparative study between conventional PI controller, discretized original STA and the proposed combined STA in tracking of various speed references under action of disturbances. Simulation and experimental results confirm that the proposed simply designed controller provides high quality performance.

Discrete-time sliding mode control system of the grid-connected doubly fed induction generator at the low sampling frequency

A new design of a digital control system for the grid-connected doubly fed induction generator is described in this paper. A discrete-time state-space model of the controlled system is obtained in the stator stationary reference frame. Using this model, a discrete-time sliding mode based control system is designed. Its tasks are the grid synchronization and the direct power control. The discrete-time equivalent control method is applied, and the control vector is calculated from the samples of voltages and currents. The control vector is converted to a switching sequence in a power converter using the space vector modulation. The modulation period is equal to the sampling period. A disturbance compensator is designed to eliminate the influence of the discretization effect and model uncertainties. In this way, a robust control system with a constant switching frequency is designed. Its digital hardware implementation is simple. The performance of the designed control system is tested on a simulation model.

Mobile ad hoc networks: Local distributed algorithms for virtual backbone

Mobile ad hoc networks are temporary, wireless, multi-hop, self-organizing networks in which terminals have weak battery supply, processing power and limited bandwidth. In addition to traditional cellular networks (GSM, 3G, LTE) and increasingly popular WiFi networks, mobile ad hoc networks will be present in many spheres of human activity in the future. Especially important application areas are rescue and disaster recovery missions. In recent years, routing algorithms for mobile ad hoc networks have been popular research topics. This paper represents a survey of local distributed algorithms which are used for virtual backbone-based routing. The virtual backbone transforms an original flat structure of the mobile ad hoc networks into hierarchical, which is more appropriate for routing management. This paper presents various categories of algorithms and can facilitate decision of which algorithm is suitable for particular purpose.