Vladimir Kvrgić

Optimisation of cast pistons made of Al–Si piston alloy

Abstract In this paper, the advantages of applying software packages for the optimisation of the relevant technological parameters of casting and their implementation and control in production processes using the example of a cast piston are presented. The micro- and macrostructural characteristics of two different modes of solidification are given. In previous studies, possible phases in the microstructure of an aluminium alloy piston were identified, and their influences on the physical, chemical and mechanical properties are well known. The aim of this study is to obtain piston alloys with the desired mechanical and physical properties in the appropriate sections by combination of specific phases (share and distribution stages, the optimal size of primary silicon crystals, grain size, etc.) based on modern techniques.

A control algorithm for improving the accuracy of five-axis machine tools

An algorithm for reducing the influence of geometrical, thermal, kinematic and stiffness errors in five-axis machine tool components on the desired tool position and orientation is given. This new algorithm is based on the calculation of the cutting tool error matrix for orthogonal machine tools. In the new model of this matrix, all angular errors of the machine links are considered as infinitesimal rotations. The error matrix is a function of the commanded machine component positions and the errors in these positions. To correct errors in the three translational and two angular tool positions, a matrix of commanded tool position and orientation is multiplied by the inverse error matrix in every period of the tool trajectory interpolation. This corrected matrix of the tool position and orientation provides the inverse kinematics used for calculation of the successive links positions required for achieving the given tool trajectory. The control algorithm for five-axis machine tools with the error compensation is implemented both in the CNC system and in the postprocessor. The proposed algorithm is applied on a vertical five-axis turning centre with two translational and three rotational axes. Twenty-four errors that could cause inaccurate machining are recognised on this machine. The machine links and their coordinate frames are denoted using the Denavit–Hartenberg parameters.

Remote control of industrial robot lola 50 using wireless communication and android device

Android platform based devices are powerful mobile computers with a rich variety of built-in sensors and permanent Internet connectivity. Because of its powerful capabilities, as well as open architecture, they became promising candidates for a number of industrial applications. This paper describes the process of implementation and use of application for remote control of industrial robot Lola 50, in manual mode, using the Android mobile phone and wireless communication.

A proposed approach to the classification of bearing condition using wavelets and random forests

This paper presents a proposed approach to the classification of rolling element bearing faults. The approach consists of vibration signal acquisition, digital signal processing, feature extraction from the vibration signal and classification into functional or defective rolling element bearing. Digital signal processing includes signal decomposition and de-nosing using wavelets. An 18-dimensional vector of the vibration signal feature is obtained as a result of feature extraction. Characterization of each recorded vibration signal is performed by a combination of signals time varying statistical parameters and characteristic rolling element bearing fault frequency components. The classification is performed using random forests algorithm.

3D simulator for human centrifuge motion testing and verification

In the process of defining commands and developing algorithms for movements of complex and massive devices, such as human centrifuge, it is unsafe and demanding to perform testing on the real machine. Getting overview of devices operations might be of great importance especially before the final realization. This paper presents a system for programming and simulation of the human centrifuge motion with integrated 3D motion simulator. The simulator is used for verification of newly defined motion commands and testing the new algorithms for the human centrifuge motion.

Automated testing of L-IRL robot programming language parser

Parser testing represents the basis of compiler testing because the accuracy of parsing execution directly affects the accuracy of semantic analysis, optimization and object code generation. It should include tests for correct and expected, but also for unexpected and invalid cases. In this paper, techniques for testing the parser, as well as algorithms and tools for test sentence generation are discussed. Generation of negative test sentences by modifying the original language grammar is described. Positive and negative test cases generated by Grow algorithm and Purdom algorithm are applied to the testing of L-IRL robot programming language and obtained results are described in this paper.

Optimal Control of Singular Systems. Continuous Time Case

In this paper for the class of singular dynamical systems we present optimal control results. We develop unified framework for feedback optimal and inverse optimal control involving a nonlinear-nonquadratic performance functional. It is shown that the cost functional can be evaluated in closed-form as long as the cost functional considered is related in a specific way to an underlying Lyapunov function that guarantees asymptotic stability of the nonlinear closed-loop singular system. Furthermore, the Lyapunov function is shown to be a solution of a steady-state, Hamilton-Jacobi-Bellman equation.

Dissipativity of Thermodynamical model of process of streaming heated fluids through reservoir

Abstract In this paper we present mathematical model of heated reservoir under the pressure with streaming fluid entering into the reservoir of constant volume, with output. We present dissipativity, passivity, losslessness and nonexpansivity results which can be applied to thermodynamical systems. Further, we apply these theoretical results on concrete thermodynamical model and we give general way how to apply these results.

Singularly impulsive dynamical systems with time delay: Mathematical model and stability

In this paper we introduce new class of system, so called singularly impulsive or generalized impulsive dynamical systems with time delay. Dynamics of this system is characterized by the set of differential and difference equations with time delay, and algebraic equations. They represent the class of hybrid systems, where algebraic equations represent constraints that differential and difference equations with time delay need to satisfy. In this paper we present model, assumptions on the model, two classes of singularly impulsive dynamical systems with delay - time dependent and state dependent. Further, we present Lyapunov and asymptotic stability theorems for nonlinear time-dependent and state-dependent singularly impulsive dynamical systems with time delay.

Optimal Control for Time Delay Singular Systems

Abstract For the class of singular time-delay dynamical systems we present optimal control results. We developed unified framework for feedback optimal and inverse optimal control involving a nonlinear-nonquadratic performance functional. It is shown that the cost functional can be evaluated in closed-form as long as the cost functional considered is related in a specific way to an underlying Lyapunov function that guarantees asymptotic stability of the nonlinear closed-loop singular time-delay system. Furthermore, the Lyapunov function is shown to be a solution of a steady-state, Hamilton-Jacobi-Bellman equation.