Dragan Prsic - Academia.edu (original) (raw)

Papers by Dragan Prsic

Numerical Solution for the Deflection of the Column-Mounted Jib Crane Structure

Mechanics Transport Communications - Academic journal,, 2019

International Conference on Information Society, 2017

To increase energy efficiency, heat pumps are becoming part of an integral solution for residenti... more To increase energy efficiency, heat pumps are becoming part of an integral solution for residential heating, ventilation, and airconditioning. Depending on the electricity tariff, coefficient of performance (COP) and thermal load, the heat pump can also be combined with other heat sources (smart grid). All these new possibilities additionally complicate the heat pump control. In On-Off control, special attention is paid to start-up/shut-down sequences which repeat periodically during the entire life of the heat pump. For the design of control logic for startup/shut-down sequences, the paper uses the model-driven approach instead of the traditional method. The design is organized around the model which is developed iteratively and incrementally through several use cases. Harel's statecharts implemented by Matlab tool Stateflow are used in all phases of development: from the specification of requirements up to implementation.

Materials Letters, Feb 1, 2016

Cubic SiC nano-powder particles were synthesized by a sol-gel process with an average grains size... more Cubic SiC nano-powder particles were synthesized by a sol-gel process with an average grains size of 9.5 nm which were subsequently densified by using a high-pressure "anvil-type with hollows" apparatus at a pressure of 4 GPa in order to obtain nanostructured bulk ceramic compacts. The density obtained was 4 98% at a sintering temperature of 1500°C with a holding time of only 60 s. The calculation of the average crystallite size (D) was performed on the basis of the full width at half maximum intensity (FWHM) of the XRD peaks. Williamson-Hall plots were used to separate the effect of the size and strain in the nanostructured SiC compacts. Sintered nanostructured SiC ceramic exhibits hardness and elastic modulus of 32-420 GPa respectively. Wear properties were investigated and the average value of dynamic friction coefficient obtained was 0.16.

IMK-14, 2019

Fakultet za mašinstvo i građevinarstvo u Kraljevu, Katedra za automatsko upravljanje, robotiku i ... more Fakultet za mašinstvo i građevinarstvo u Kraljevu, Katedra za automatsko upravljanje, robotiku i fluidnu tehniku, Univerzitet u Kragujevcu, Kraljevo (Srbija) Procena stanja i vremenski promenljivih parametara linearnih modela u prostoru stanja je od praktičnog značaja za dijagnostiku otkaza i upravljanje koje je tolerantno na otkaze. Ovaj rad razmatra robusnu identifikaciju linearnih modela u prostoru stanja u prisustvu otkaza komponenti i senzora. Sa druge strane, prethodni radovi na ovu temu nisu razmatrali procenu stanja i parametara linearnih sistema u prisustvu autlajera. Oni mogu značajno pokvariti karakteristike linearnih rekurzivnih algoritama, koji su projektovani da rade u prisustvu Gausovih šumova. Zbog svojih dobrih osobina u robusnoj filtraciji, modifikovani Masreliez-Martinov filtar predstavlјa kamen temelјac za realizaciju robusnog algoritma za procenu stanja i parametara linearnih vremenski promenlјivih stohastičkih sistema u prisustvu negausovih šumova. Dobre karakteristike predloženog robusnog algoritma za procenu stanja i parametara linearnih vremenski promenlјivih stohastičkih sistema ilustrovane su simulacijama. Ključne reči: linearni modeli u prostoru stanja, procena parametara i stanja, robusna identifikacija, vremenski promenljivi parametri, negausovi šumovi IMK-14-Istraživanje i razvoj u teškoj mašinogradnji

Journal of Control Science and Engineering, 2016

The multilinear model control design approach is based on the approximation of the nonlinear mode... more The multilinear model control design approach is based on the approximation of the nonlinear model of the system by a set of linear models. The paper presents the method of creation of a bank of linear models of the two-pass shell and tube heat exchanger. The nonlinear model is assumed to have a Hammerstein structure. The set of linear models is formed by decomposition of the nonlinear steady-state characteristic by using the modified Included Angle Dividing method. Two modifications of this method are proposed. The first one refers to the addition to the algorithm for decomposition, which reduces the number of linear segments. The second one refers to determination of the threshold value. The dependence between decomposition of the nonlinear characteristic and the linear dynamics of the closed-loop system is established. The decoupling process is more formal and it can be easily implemented by using software tools. Due to its simplicity, the method is particularly suitable in complex systems, such as heat exchanger networks.

Mathematical Problems in Engineering, 2013

The paper proposes a procedure for design of PI controllers for hydraulic systems with long trans... more The paper proposes a procedure for design of PI controllers for hydraulic systems with long transmission lines which are described by models of high order. Design is based on the combination of the IE criterion and engineering specifications (settling time and relative stability) as well as on the application of D-decomposition. In comparison with some known results, the method is of graphical character, and it is very simple (solving nonlinear algebraic equations is eliminated). The paper presents the algorithm of software procedure for design of the controller. The method is compared with other methods at the level of simulation, and its superiority is shown. By applying the Nyquist criterion, it is shown that the method possesses robustness in relation to non modelled dynamics.

A nature inspired optimal control of pneumatic-driven parallel robot platform

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Oct 3, 2016

Woodworking industry is increasingly characterized by processing complex spatial forms with high ... more Woodworking industry is increasingly characterized by processing complex spatial forms with high accuracy and high speeds. The use of parallel robot platforms with six degrees of freedom gains more significance. Due to stricter requirements regarding energy consumption, easy maintenance and environmental safety, parallel platforms with pneumatic drives become more and more interesting. However, the high precision tracking control of such systems represents a serious challenge for designers. The reason is found in complex dynamics of the mechanical system and strong nonlinearity of the pneumatic system. This paper presents an optimal control design for a pneumatically driven parallel robot platform. The Proportional-Integral-Derivative (PID) algorithm with feedback linearization is used for control. The parameter search method is based on a firefly algorithm due to the empirical evidence of its superiority in solving various nonconvex problems. The simulation results show that the proposed optimal tuned cascade control is effective and efficient. These results clearly demonstrate that the proposed control techniques exhibit significant performance improvement over classical and widely used control techniques.

Nonlinear Dynamics, May 1, 2020

Intensive research in the field of mathematical modeling of hydraulic servo systems has shown tha... more Intensive research in the field of mathematical modeling of hydraulic servo systems has shown that their mathematical models have many important details which cannot be included in the model. Due to impossibility of direct measurement or calculation of dimensions of certain components, leakage coefficients or friction coefficients, it was supposed that parameters of the hydraulic servo system are random. On the other side, it has been well known that the hydraulic servo system can be approximated by a linear model with time-varying parameters. An estimation of states and time-varying parameters of linear state-space models is of practical importance for fault diagnosis and fault-tolerant control. Previous works on this topic consider estimation in Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of parameter-state robust estimation of linear state-space models in the presence of all possible faults and non-Gaussian noises. Because of its good features in robust filtering, Masreliez-Martin filter represents a cornerstone for realization of the robust algorithm. The good features of the proposed robust algorithm to identification of the hydraulic servo system are illustrated by intensive simulations.

IFAC Proceedings Volumes, May 1, 1997

A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become v... more A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become very significant with time varying motion. One way to overcome these problems is to develop some kind of control algorithm. Having in mind the task of these systems, a control algorithm based on the trackability concept seems logical. The special kind of control algorithm based on this concept has been investigated on time variable speed control of pump controlled hydraulic motor. Experimental and simulation results are shown.

Optimal experiment design for identification of ARX models with constrained output in non-Gaussian noise

Applied Mathematical Modelling, Jul 1, 2016

Abstract The identification of ARX models with constrained output variance in the presence of non... more Abstract The identification of ARX models with constrained output variance in the presence of non-Gaussian distribution of measurements is proposed in this paper. In the presence of non-Gaussian noise, the Masreliez–Martin filter (robust Kalman filter) is the natural frame for identification of model parameters. For the purpose of increasing the practical value of the filter, a heuristic modification is performed. Also, an optimal input is obtained by a minimum variance controller with a Gaussian reference signal. A fundamental issue in experiment design is that the optimal input in general depends on system parameters to be estimated. In order to realize obtained optimal input, authors have proposed a two-stage adaptive procedure, where one iterates between parameter estimation, on the one side, and experiment design using the current parameter estimates, on the other. The practical behavior of new approach to optimal input design for robust identification of ARX models is shown by intensive simulations.

Application of cuckoo search algorithm to constrained control problem of a parallel robot platform

The International Journal of Advanced Manufacturing Technology, Mar 31, 2016

This paper presents a cascade load force control design for a parallel robot platform. A paramete... more This paper presents a cascade load force control design for a parallel robot platform. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on cuckoo search (CS) is suggested to effectively search parameters of the cascade controllers. The control design problem is formulated as an optimization problem under constraints. Typical constraints, such as mechanical limits on positions and maximal velocities of hydraulic actuators as well as on servo-valve positions, are included in the proposed algorithm. The optimal results are compared to the state-of-the-art algorithms for these problem instances (NP-hard and constrained optimization problems). Simulation results also show that applied optimal tuned cascade control algorithm exhibits a significant performance improvement over classical tuning methods.

Facta Universitatis, Jan 27, 2020

Joint estimation of states and time-varying parameters of linear state space models is of practic... more Joint estimation of states and time-varying parameters of linear state space models is of practical importance for the fault diagnosis and fault tolerant control. Previous works on this topic consider the joint estimation in the Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of the joint parameter-state robust estimation of linear state space models in the presence of non-Gaussian noises. The case of parameterdependent matrices is considered. Because of its good features in robust filtering, the extended Masreliez-Martin filter represents a cornerstone for realization of the robust algorithms for joint state-parameter estimation of linear time-varying stochastic systems in the presence of non-Gaussian noises. The good features of the proposed robust algorithm for joint estimation of linear time-varying stochastic systems are illustrated by intensive simulations.

The International Journal of Advanced Manufacturing Technology, Mar 11, 2014

A new cascade load force control design for a parallel robot platform is proposed. A parameter se... more A new cascade load force control design for a parallel robot platform is proposed. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on particle swarm optimization (PSO) is suggested to effectively search the parameters of the cascade controller. We used a unified mathematical model of a hydraulic actuator of parallel robot platform. These equations are readily applicable to various types of proportional valves, and they unify the cases of critical center, overlapped, and underlapped valves. These unified model equations are useful for nonlinear controller design. Simulation results show the advantages of the proposed optimal tuned cascade controller to solve the formulated tracking problem in relation to the classical proportional-integral (PI) controller.

Scientific Technical Review, 2019

Intensive research in the field of mathematical modeling of hydraulic servo systems has shown tha... more Intensive research in the field of mathematical modeling of hydraulic servo systems has shown that their mathematical models have many important details which cannot be included in the model. Due to impossibility of direct measurement or calculation of dimensions of certain components, leakage coefficients or friction coefficients, it was supposed that parameters of the hydraulic servo system are random (stochastic nature). On the other side, it has been well known that the hydraulic servo cylinder can be approximated by a linear model with time-varying parameters. An estimation of states and time-varying parameters of linear state space models is of practical importance for fault diagnosis and fault tolerant control. Previous works on this topic consider estimation in Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of parameter-state robust estimation of linear state space models in presence of non-Gaussian noises. The case of robust estimation of states and parameters of linear systems with parameter faults is considered. Because of its good features in robust filtering, the extended Masreliez-Martin filter represents a cornerstone for realization of the robust algorithm. The good features of the proposed robust algorithm to identification of the hydraulic servo cylinder are illustrated by intensive simulations.

Materiali in tehnologije, 2019

The increase in wear resistance of cast irons after laser treatment is due not only to the corres... more The increase in wear resistance of cast irons after laser treatment is due not only to the corresponding structural and phase composition, but also to the improvement in the friction conditions due to the graphite retained in the laser impact zone. Also, laser hardening increases the wear resistance of steels and some other alloys in terms of the friction in alkaline and acidic environments. In this article we present a new method for a hybrid system of machine learning using a new method for statistical pattern recognition through network theory in robot laser hardening (RLH). We combined the method of multiple regression, the method of a support vector machine and the method of a neural network. For statistical pattern recognition we use the topological properties of network theory. The even distribution of the topological property16-300 triads throughout the various levels of the organization and network in the microstructure of RLH indicates that there is a strong linkage across the network and an active connection among the needles of martensite. Keyword: hybrid machine learning, statistical pattern recognition, network theory, fractals Pove~anje obrabne odpornosti litega`eleza po laserski obdelavi je posledica ne le ustrezne strukturne in fazne sestave, temvet udi izbolj{anja pogojev trenja zaradi grafita v obmo~ju laserja. Lasersko kaljenje pove~a tudi odpornost proti obrabi jekel in nekaterih drugih zlitin s stali{~a trenja v kislem in alkalnih okoljih. Avtorji predstavljajo novo metodo hibridnega sistema strojnega u~enja z uporabo nove metode za prepoznavanje statisti~nih vzorcev s teorijo omre`ja pri robotnem laserskem kaljenju (RLH). Zdru`ili so metodo multiple regresije, metode podpornih vektorjev in metodo nevronskih mre`. Za prepoznavanje statisti~nih vzorcev so uporabili topolo{ke lastnosti teorije omre`ja. Enakomerna porazdelitev topolo{kih lastnih 16-300 triad v razli~nih ravneh organizacije in mre`e v mikrostrukturi RLH ka`e, da obstaja mo~na povezava preko omre`ja in aktivna povezava med iglicami martenzita. Klju~ne besede: hibridno strojno u~enje, statisti~no razpoznavanje vzorcev, teorija omre`ij, fraktali

Engineering Today

In this paper, the mechanism for the fault estimation (FE) problem for a steer-by-wire (SBW) vehi... more In this paper, the mechanism for the fault estimation (FE) problem for a steer-by-wire (SBW) vehicle with sensor and actuator faults is investigated. To deal with the design issues, we transformed the nonlinear model of SBW vehicle into a new coordinate system to jointly estimate the sensor and actuator faults. In the new coordinate system, the Lipschitz conditions and system uncertainties are also considered. The proposed schemes essentially transform the original system into two subsystems, where subsystem-1 includes the effects of actuator faults but is free from sensor faults and subsystem-2 only has sensor faults. Then two sliding mode observers (SMOs) are designed to estimate actuator and sensor faults, respectively. The sufficient conditions for the existence of the proposed observers with FI°o performance are derived and expressed as an LMI optimization problem such that the upper bounds of the state and fault estimation errors can be minimized. Finally, the numerical exampl...

Sensor fault estimation for hydraulic servo actuator based on sliding mode observer

Mathematical Modelling and Control

In this paper, the mechanism for the fault estimation (FE) problem for a hydraulic servo actuator... more In this paper, the mechanism for the fault estimation (FE) problem for a hydraulic servo actuator (HSA) with sensor faults is investigated. To deal with the design issues, we transformed the nonlinear model of HSA into a new coordinate system to estimate the sensor faults. In the new coordinate system, the Lipschitz conditions and system uncertainties are also considered. Then, we implement a sliding mode observer (SMO) approach to introduce the transformation scheme to make the system rational. The proposed fault estimation scheme essentially transforms the original system into two subsystems where the first one includes system uncertainties, but is free from sensor faults and the second one has sensor faults but without uncertainties. The effects of system uncertainties on the estimation errors of states and faults are minimized by integrating an $ H_\infty $ uncertainty attenuation level into the observer. The sufficient conditions for the state estimation error to be bounded and...

Describing function of the pneumatic flapper-nozzle valve

Mechanical Systems and Signal Processing

Abstract This paper addresses the mass flow rate characteristic of a pneumatic valve set in the f... more Abstract This paper addresses the mass flow rate characteristic of a pneumatic valve set in the frequency domain. The valve set consists of a flapper-nozzle type valve and a constant isothermal volume chamber. It represents a part of the control system of the pneumatic parallel robot platform. Different flow regimes are analyzed because of air compressibility. The nonlinearity originating from the mass flow rate characteristic is approximated by the sinusoidal input describing function. Analytical determination of the describing function in a general case is not possible. However, the equivalent nonlinearity and the corresponding Hammerstein model can be introduced for a certain flow regime. In that case, the describing function of nonlinearity can be determined analytically. Amplitude and frequency responses show that the nonlinearity becomes more prominent at smaller frequencies and higher amplitudes of the exogenous signal. Analytical results show good agreement with the experimental results.

Simulation of hydraulic check valve for forestry equipment

International Journal of Heavy Vehicle Systems

Modelling and simulating complex systems, such as forestry equipment, are often the only way for ... more Modelling and simulating complex systems, such as forestry equipment, are often the only way for their full analysis and design. This problem may lead to a stiff set of equations that are followed by numerical problems. In this paper two alternative approaches are investigated. The first one refers to the use of a variable step of integration by continuous models adjusted to the fastest processes. The second one refers to the approximation of fast transitions by ideal instantaneous mode-transitions and hybrid models. These two approaches are analysed in the framework of bond graph. The classical bond graph is adopted for description of the continuous models, and the switched bond graph is preferred for description of the hybrid models. The model of check valve is used as a working example for illustration of results. Matlab/Simulink tools are used for modelling and simulation.

Time Variable Speed Control of Pump Controlled Hydraulic Motor Using Natural Tracking Control

IFAC Proceedings Volumes

Abstract A pump controlled hydraulic motor meets problems with speed and accuracy. These problems... more Abstract A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become very significant with time varying motion. One way to overcome these problems is to develop some kind of control algorithm. Having in mind the task of these systems, a control algorithm based on the trackability concept seems logical. The special kind of control algorithm based on this concept has been investigated on time variable speed control of pump controlled hydraulic motor. Experimental and simulation results are shown.

Numerical Solution for the Deflection of the Column-Mounted Jib Crane Structure

Mechanics Transport Communications - Academic journal,, 2019

International Conference on Information Society, 2017

To increase energy efficiency, heat pumps are becoming part of an integral solution for residenti... more To increase energy efficiency, heat pumps are becoming part of an integral solution for residential heating, ventilation, and airconditioning. Depending on the electricity tariff, coefficient of performance (COP) and thermal load, the heat pump can also be combined with other heat sources (smart grid). All these new possibilities additionally complicate the heat pump control. In On-Off control, special attention is paid to start-up/shut-down sequences which repeat periodically during the entire life of the heat pump. For the design of control logic for startup/shut-down sequences, the paper uses the model-driven approach instead of the traditional method. The design is organized around the model which is developed iteratively and incrementally through several use cases. Harel's statecharts implemented by Matlab tool Stateflow are used in all phases of development: from the specification of requirements up to implementation.

Materials Letters, Feb 1, 2016

Cubic SiC nano-powder particles were synthesized by a sol-gel process with an average grains size... more Cubic SiC nano-powder particles were synthesized by a sol-gel process with an average grains size of 9.5 nm which were subsequently densified by using a high-pressure "anvil-type with hollows" apparatus at a pressure of 4 GPa in order to obtain nanostructured bulk ceramic compacts. The density obtained was 4 98% at a sintering temperature of 1500°C with a holding time of only 60 s. The calculation of the average crystallite size (D) was performed on the basis of the full width at half maximum intensity (FWHM) of the XRD peaks. Williamson-Hall plots were used to separate the effect of the size and strain in the nanostructured SiC compacts. Sintered nanostructured SiC ceramic exhibits hardness and elastic modulus of 32-420 GPa respectively. Wear properties were investigated and the average value of dynamic friction coefficient obtained was 0.16.

IMK-14, 2019

Fakultet za mašinstvo i građevinarstvo u Kraljevu, Katedra za automatsko upravljanje, robotiku i ... more Fakultet za mašinstvo i građevinarstvo u Kraljevu, Katedra za automatsko upravljanje, robotiku i fluidnu tehniku, Univerzitet u Kragujevcu, Kraljevo (Srbija) Procena stanja i vremenski promenljivih parametara linearnih modela u prostoru stanja je od praktičnog značaja za dijagnostiku otkaza i upravljanje koje je tolerantno na otkaze. Ovaj rad razmatra robusnu identifikaciju linearnih modela u prostoru stanja u prisustvu otkaza komponenti i senzora. Sa druge strane, prethodni radovi na ovu temu nisu razmatrali procenu stanja i parametara linearnih sistema u prisustvu autlajera. Oni mogu značajno pokvariti karakteristike linearnih rekurzivnih algoritama, koji su projektovani da rade u prisustvu Gausovih šumova. Zbog svojih dobrih osobina u robusnoj filtraciji, modifikovani Masreliez-Martinov filtar predstavlјa kamen temelјac za realizaciju robusnog algoritma za procenu stanja i parametara linearnih vremenski promenlјivih stohastičkih sistema u prisustvu negausovih šumova. Dobre karakteristike predloženog robusnog algoritma za procenu stanja i parametara linearnih vremenski promenlјivih stohastičkih sistema ilustrovane su simulacijama. Ključne reči: linearni modeli u prostoru stanja, procena parametara i stanja, robusna identifikacija, vremenski promenljivi parametri, negausovi šumovi IMK-14-Istraživanje i razvoj u teškoj mašinogradnji

Journal of Control Science and Engineering, 2016

The multilinear model control design approach is based on the approximation of the nonlinear mode... more The multilinear model control design approach is based on the approximation of the nonlinear model of the system by a set of linear models. The paper presents the method of creation of a bank of linear models of the two-pass shell and tube heat exchanger. The nonlinear model is assumed to have a Hammerstein structure. The set of linear models is formed by decomposition of the nonlinear steady-state characteristic by using the modified Included Angle Dividing method. Two modifications of this method are proposed. The first one refers to the addition to the algorithm for decomposition, which reduces the number of linear segments. The second one refers to determination of the threshold value. The dependence between decomposition of the nonlinear characteristic and the linear dynamics of the closed-loop system is established. The decoupling process is more formal and it can be easily implemented by using software tools. Due to its simplicity, the method is particularly suitable in complex systems, such as heat exchanger networks.

Mathematical Problems in Engineering, 2013

The paper proposes a procedure for design of PI controllers for hydraulic systems with long trans... more The paper proposes a procedure for design of PI controllers for hydraulic systems with long transmission lines which are described by models of high order. Design is based on the combination of the IE criterion and engineering specifications (settling time and relative stability) as well as on the application of D-decomposition. In comparison with some known results, the method is of graphical character, and it is very simple (solving nonlinear algebraic equations is eliminated). The paper presents the algorithm of software procedure for design of the controller. The method is compared with other methods at the level of simulation, and its superiority is shown. By applying the Nyquist criterion, it is shown that the method possesses robustness in relation to non modelled dynamics.

A nature inspired optimal control of pneumatic-driven parallel robot platform

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Oct 3, 2016

Woodworking industry is increasingly characterized by processing complex spatial forms with high ... more Woodworking industry is increasingly characterized by processing complex spatial forms with high accuracy and high speeds. The use of parallel robot platforms with six degrees of freedom gains more significance. Due to stricter requirements regarding energy consumption, easy maintenance and environmental safety, parallel platforms with pneumatic drives become more and more interesting. However, the high precision tracking control of such systems represents a serious challenge for designers. The reason is found in complex dynamics of the mechanical system and strong nonlinearity of the pneumatic system. This paper presents an optimal control design for a pneumatically driven parallel robot platform. The Proportional-Integral-Derivative (PID) algorithm with feedback linearization is used for control. The parameter search method is based on a firefly algorithm due to the empirical evidence of its superiority in solving various nonconvex problems. The simulation results show that the proposed optimal tuned cascade control is effective and efficient. These results clearly demonstrate that the proposed control techniques exhibit significant performance improvement over classical and widely used control techniques.

Nonlinear Dynamics, May 1, 2020

Intensive research in the field of mathematical modeling of hydraulic servo systems has shown tha... more Intensive research in the field of mathematical modeling of hydraulic servo systems has shown that their mathematical models have many important details which cannot be included in the model. Due to impossibility of direct measurement or calculation of dimensions of certain components, leakage coefficients or friction coefficients, it was supposed that parameters of the hydraulic servo system are random. On the other side, it has been well known that the hydraulic servo system can be approximated by a linear model with time-varying parameters. An estimation of states and time-varying parameters of linear state-space models is of practical importance for fault diagnosis and fault-tolerant control. Previous works on this topic consider estimation in Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of parameter-state robust estimation of linear state-space models in the presence of all possible faults and non-Gaussian noises. Because of its good features in robust filtering, Masreliez-Martin filter represents a cornerstone for realization of the robust algorithm. The good features of the proposed robust algorithm to identification of the hydraulic servo system are illustrated by intensive simulations.

IFAC Proceedings Volumes, May 1, 1997

A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become v... more A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become very significant with time varying motion. One way to overcome these problems is to develop some kind of control algorithm. Having in mind the task of these systems, a control algorithm based on the trackability concept seems logical. The special kind of control algorithm based on this concept has been investigated on time variable speed control of pump controlled hydraulic motor. Experimental and simulation results are shown.

Optimal experiment design for identification of ARX models with constrained output in non-Gaussian noise

Applied Mathematical Modelling, Jul 1, 2016

Abstract The identification of ARX models with constrained output variance in the presence of non... more Abstract The identification of ARX models with constrained output variance in the presence of non-Gaussian distribution of measurements is proposed in this paper. In the presence of non-Gaussian noise, the Masreliez–Martin filter (robust Kalman filter) is the natural frame for identification of model parameters. For the purpose of increasing the practical value of the filter, a heuristic modification is performed. Also, an optimal input is obtained by a minimum variance controller with a Gaussian reference signal. A fundamental issue in experiment design is that the optimal input in general depends on system parameters to be estimated. In order to realize obtained optimal input, authors have proposed a two-stage adaptive procedure, where one iterates between parameter estimation, on the one side, and experiment design using the current parameter estimates, on the other. The practical behavior of new approach to optimal input design for robust identification of ARX models is shown by intensive simulations.

Application of cuckoo search algorithm to constrained control problem of a parallel robot platform

The International Journal of Advanced Manufacturing Technology, Mar 31, 2016

This paper presents a cascade load force control design for a parallel robot platform. A paramete... more This paper presents a cascade load force control design for a parallel robot platform. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on cuckoo search (CS) is suggested to effectively search parameters of the cascade controllers. The control design problem is formulated as an optimization problem under constraints. Typical constraints, such as mechanical limits on positions and maximal velocities of hydraulic actuators as well as on servo-valve positions, are included in the proposed algorithm. The optimal results are compared to the state-of-the-art algorithms for these problem instances (NP-hard and constrained optimization problems). Simulation results also show that applied optimal tuned cascade control algorithm exhibits a significant performance improvement over classical tuning methods.

Facta Universitatis, Jan 27, 2020

Joint estimation of states and time-varying parameters of linear state space models is of practic... more Joint estimation of states and time-varying parameters of linear state space models is of practical importance for the fault diagnosis and fault tolerant control. Previous works on this topic consider the joint estimation in the Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of the joint parameter-state robust estimation of linear state space models in the presence of non-Gaussian noises. The case of parameterdependent matrices is considered. Because of its good features in robust filtering, the extended Masreliez-Martin filter represents a cornerstone for realization of the robust algorithms for joint state-parameter estimation of linear time-varying stochastic systems in the presence of non-Gaussian noises. The good features of the proposed robust algorithm for joint estimation of linear time-varying stochastic systems are illustrated by intensive simulations.

The International Journal of Advanced Manufacturing Technology, Mar 11, 2014

A new cascade load force control design for a parallel robot platform is proposed. A parameter se... more A new cascade load force control design for a parallel robot platform is proposed. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on particle swarm optimization (PSO) is suggested to effectively search the parameters of the cascade controller. We used a unified mathematical model of a hydraulic actuator of parallel robot platform. These equations are readily applicable to various types of proportional valves, and they unify the cases of critical center, overlapped, and underlapped valves. These unified model equations are useful for nonlinear controller design. Simulation results show the advantages of the proposed optimal tuned cascade controller to solve the formulated tracking problem in relation to the classical proportional-integral (PI) controller.

Scientific Technical Review, 2019

Intensive research in the field of mathematical modeling of hydraulic servo systems has shown tha... more Intensive research in the field of mathematical modeling of hydraulic servo systems has shown that their mathematical models have many important details which cannot be included in the model. Due to impossibility of direct measurement or calculation of dimensions of certain components, leakage coefficients or friction coefficients, it was supposed that parameters of the hydraulic servo system are random (stochastic nature). On the other side, it has been well known that the hydraulic servo cylinder can be approximated by a linear model with time-varying parameters. An estimation of states and time-varying parameters of linear state space models is of practical importance for fault diagnosis and fault tolerant control. Previous works on this topic consider estimation in Gaussian noise environment, but not in the presence of outliers. The known fact is that the measurements have inconsistent observations with the largest part of the observation population (outliers). They can significantly make worse the properties of linearly recursive algorithms which are designed to work in the presence of Gaussian noises. This paper proposes the strategy of parameter-state robust estimation of linear state space models in presence of non-Gaussian noises. The case of robust estimation of states and parameters of linear systems with parameter faults is considered. Because of its good features in robust filtering, the extended Masreliez-Martin filter represents a cornerstone for realization of the robust algorithm. The good features of the proposed robust algorithm to identification of the hydraulic servo cylinder are illustrated by intensive simulations.

Materiali in tehnologije, 2019

The increase in wear resistance of cast irons after laser treatment is due not only to the corres... more The increase in wear resistance of cast irons after laser treatment is due not only to the corresponding structural and phase composition, but also to the improvement in the friction conditions due to the graphite retained in the laser impact zone. Also, laser hardening increases the wear resistance of steels and some other alloys in terms of the friction in alkaline and acidic environments. In this article we present a new method for a hybrid system of machine learning using a new method for statistical pattern recognition through network theory in robot laser hardening (RLH). We combined the method of multiple regression, the method of a support vector machine and the method of a neural network. For statistical pattern recognition we use the topological properties of network theory. The even distribution of the topological property16-300 triads throughout the various levels of the organization and network in the microstructure of RLH indicates that there is a strong linkage across the network and an active connection among the needles of martensite. Keyword: hybrid machine learning, statistical pattern recognition, network theory, fractals Pove~anje obrabne odpornosti litega`eleza po laserski obdelavi je posledica ne le ustrezne strukturne in fazne sestave, temvet udi izbolj{anja pogojev trenja zaradi grafita v obmo~ju laserja. Lasersko kaljenje pove~a tudi odpornost proti obrabi jekel in nekaterih drugih zlitin s stali{~a trenja v kislem in alkalnih okoljih. Avtorji predstavljajo novo metodo hibridnega sistema strojnega u~enja z uporabo nove metode za prepoznavanje statisti~nih vzorcev s teorijo omre`ja pri robotnem laserskem kaljenju (RLH). Zdru`ili so metodo multiple regresije, metode podpornih vektorjev in metodo nevronskih mre`. Za prepoznavanje statisti~nih vzorcev so uporabili topolo{ke lastnosti teorije omre`ja. Enakomerna porazdelitev topolo{kih lastnih 16-300 triad v razli~nih ravneh organizacije in mre`e v mikrostrukturi RLH ka`e, da obstaja mo~na povezava preko omre`ja in aktivna povezava med iglicami martenzita. Klju~ne besede: hibridno strojno u~enje, statisti~no razpoznavanje vzorcev, teorija omre`ij, fraktali

Engineering Today

In this paper, the mechanism for the fault estimation (FE) problem for a steer-by-wire (SBW) vehi... more In this paper, the mechanism for the fault estimation (FE) problem for a steer-by-wire (SBW) vehicle with sensor and actuator faults is investigated. To deal with the design issues, we transformed the nonlinear model of SBW vehicle into a new coordinate system to jointly estimate the sensor and actuator faults. In the new coordinate system, the Lipschitz conditions and system uncertainties are also considered. The proposed schemes essentially transform the original system into two subsystems, where subsystem-1 includes the effects of actuator faults but is free from sensor faults and subsystem-2 only has sensor faults. Then two sliding mode observers (SMOs) are designed to estimate actuator and sensor faults, respectively. The sufficient conditions for the existence of the proposed observers with FI°o performance are derived and expressed as an LMI optimization problem such that the upper bounds of the state and fault estimation errors can be minimized. Finally, the numerical exampl...

Sensor fault estimation for hydraulic servo actuator based on sliding mode observer

Mathematical Modelling and Control

In this paper, the mechanism for the fault estimation (FE) problem for a hydraulic servo actuator... more In this paper, the mechanism for the fault estimation (FE) problem for a hydraulic servo actuator (HSA) with sensor faults is investigated. To deal with the design issues, we transformed the nonlinear model of HSA into a new coordinate system to estimate the sensor faults. In the new coordinate system, the Lipschitz conditions and system uncertainties are also considered. Then, we implement a sliding mode observer (SMO) approach to introduce the transformation scheme to make the system rational. The proposed fault estimation scheme essentially transforms the original system into two subsystems where the first one includes system uncertainties, but is free from sensor faults and the second one has sensor faults but without uncertainties. The effects of system uncertainties on the estimation errors of states and faults are minimized by integrating an $ H_\infty $ uncertainty attenuation level into the observer. The sufficient conditions for the state estimation error to be bounded and...

Describing function of the pneumatic flapper-nozzle valve

Mechanical Systems and Signal Processing

Abstract This paper addresses the mass flow rate characteristic of a pneumatic valve set in the f... more Abstract This paper addresses the mass flow rate characteristic of a pneumatic valve set in the frequency domain. The valve set consists of a flapper-nozzle type valve and a constant isothermal volume chamber. It represents a part of the control system of the pneumatic parallel robot platform. Different flow regimes are analyzed because of air compressibility. The nonlinearity originating from the mass flow rate characteristic is approximated by the sinusoidal input describing function. Analytical determination of the describing function in a general case is not possible. However, the equivalent nonlinearity and the corresponding Hammerstein model can be introduced for a certain flow regime. In that case, the describing function of nonlinearity can be determined analytically. Amplitude and frequency responses show that the nonlinearity becomes more prominent at smaller frequencies and higher amplitudes of the exogenous signal. Analytical results show good agreement with the experimental results.

Simulation of hydraulic check valve for forestry equipment

International Journal of Heavy Vehicle Systems

Modelling and simulating complex systems, such as forestry equipment, are often the only way for ... more Modelling and simulating complex systems, such as forestry equipment, are often the only way for their full analysis and design. This problem may lead to a stiff set of equations that are followed by numerical problems. In this paper two alternative approaches are investigated. The first one refers to the use of a variable step of integration by continuous models adjusted to the fastest processes. The second one refers to the approximation of fast transitions by ideal instantaneous mode-transitions and hybrid models. These two approaches are analysed in the framework of bond graph. The classical bond graph is adopted for description of the continuous models, and the switched bond graph is preferred for description of the hybrid models. The model of check valve is used as a working example for illustration of results. Matlab/Simulink tools are used for modelling and simulation.

Time Variable Speed Control of Pump Controlled Hydraulic Motor Using Natural Tracking Control

IFAC Proceedings Volumes

Abstract A pump controlled hydraulic motor meets problems with speed and accuracy. These problems... more Abstract A pump controlled hydraulic motor meets problems with speed and accuracy. These problems become very significant with time varying motion. One way to overcome these problems is to develop some kind of control algorithm. Having in mind the task of these systems, a control algorithm based on the trackability concept seems logical. The special kind of control algorithm based on this concept has been investigated on time variable speed control of pump controlled hydraulic motor. Experimental and simulation results are shown.