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In this paper, a new concept of the fuzzy logic controller is presented. The proposed concept is called fuzzy ontology controller and it's based on an ontology description of the Fuzzy Logic Controller (FLC). In this concept, the SPARQL query sent to the ontology replaced the fuzzification process, fuzzy interface, and rules of the fuzzy controller while defuzzification is done on an obtained response. Fuzzy ontology is designed with Prot'{;e};g'{;e}; and hosted in the Virtuoso database on a remote server. Simulation results obtained with the proposed fuzzy ontology controller are compared to ones obtained with the classical fuzzy logic controller. Both controllers obtained the same simulation results due to the same membership function and defuzzification process. The results showed that this concept can be used as a part of some IoT solution within the vision of Industry 4.0. Also, results confirmed that the ontology-based controller works properly and gives the same output as FLC. The experiment is carried out on a heat exchange process controlled with a PLC. Modbus TCP protocol is used for communication between the server PC and a PLC. Experimental results show that only slow processes are controllable for now due to slow communication between PLC and server and the time needed for execution of SPARQL queries.

Increasing demands in terms of reducing the cost of running forestry machines along with the regulatory pressures for lower exhaust emissions encourages the usage of hybrid powertrains in field applications. Hybrid power-trains consist of two or more different energy sources, which leads to many open questions in terms of energy management control, which have significant influence on the power-train, efficiency, fuel consumption and consequently on the operating cost and emissions of greenhouse gasses. Therefore, this paper proposes the optimal energy management control strategy intended to be used in hybridized articulated forestry tractor, also known as skidder. The proposed control strategy is verified on the previously developed skidder model by a comprehensive simulations over realistically recorded field data. The simulation results are used to gain insights about the possible advantages of proposed optimal control strategy in terms of feasible reduction of fuel consumption and related CO2 emissions.

By using built-in or cartridge valves, it is possible to realize cheaper hydraulic systems, which need less space, have a short switching time and less fluid leakage, less time for assembly and installation, and give a better appearance of the hydraulic system, because they are usually installed in an aluminium block. The paper presents a laboratory setup of a hydraulic servo system using cartridge 2/2 valves to achieve precise positioning of the hydraulic cylinder, with the aim of clearly demonstrating the application of these valves in industrial plants, as well as their use in various mobile systems. The article describes the implementation of a control algorithm for the realization of manual and automatic mode of operation of the system and several ways to realize the precise movement of the hydraulic cylinder and simulation of the actuator load.

Forestry vehicles have been increasingly equipped with hybrid electric power-trains in order to provide significant gains in fuel economy, and also to facilitate reductions in greenhouse gases emissions. Due to the fact that hybrid power-trains consist of two or more different energy sources, many questions in terms of power-train components sizing and energy management control are opened, and all of them have influence on the power-train purchase cost and operating efficiency. Therefore, this paper propose an combined optimization approach of powertrain components size along with energy management rules. The hybrid skidder powertrain components are optimized by parametric optimization algorithm with the aim to minimize their size while maintain comparable traction characteristics as conventional forestry vehicle. Optimal control rules are also optimized by recently introduced cascade optimization algorithm with the aim to reduce powertrain fuel consumption. The obtained optimization results are verified by a comprehensive computer simulations, and are also used to gain insights about the possible advantages of optimized powertrain in terms of fuel consumption reduction and related CO2 emissions. The optimization results are also used to provide recommendations for design of a realistic (online) control strategy.

In this paper, a novel energy-efficient Direct Driven Hydraulic (DDH) drive is made in parallel with a classical valve-controlled proportional electrohydraulic system. In the proposed concept asymmetrical hydraulic cylinder is controlled with two reversible pumps directly connected to a servo motor. Due to direct control of the oil flow, such system provides higher energy efficiency in comparison to a valve-controlled hydraulic system. The experimental setup is designed with the possibility of easy switching between both systems, which enables an exact comparison of the experimental results. Sliding Mode Controller (SMC) is designed for the DDH system and also for the classical proportional electro-hydraulic system. A comparison study of two systems is done based on the experimental results obtained with the SMC while reference results are obtained with a widely used PID controller. Parameters for the PID controller are obtained with the Ziegler-Nichols method. The same parameters are used for both controllers in all test cases. The performance and energy efficiency of the proposed system is evaluated through a step and sine wave reference signal with different payloads varying from 0 to 200 kg with 20 kg increments. Additionally, system performance is evaluated based on six parameters calculated from the system response while energy efficiency is calculated based on input and output powers of the systems.

Nowadays there are increasing demands in terms of reducing the cost of running forestry machines along with the regulatory pressures for lower exhaust emissions to improve the ecological indices and reduction of acoustic noise in order to comply with increasingly more stringent industry ergonomic guidelines. Therefore, the producers of forestry equipment are increasingly interested to make such heavy machinery more efficient, which can already be seen with the emergence of certain hybrid and electric powertrain-based forestry vehicles. However, many tools and accessories used by these heavy vehicles are still powered by hydraulics systems. For example, articulated forestry tractor known as skidder uses hydraulic steering, hydraulic lifting for front pushing plate or rear protection plate, and also uses a hydraulic double-drum winch. Having this in mind, this paper investigates the possible use of direct driven electro-hydraulic system instead of the classical one in order to increase the skidder’s operating efficiency. Both the classical and direct driven electro-hydraulic systems are modeled, simulated and experimentally verified for the purpose of comparative analysis of their efficiency. Experiments are carried out under laboratory conditions and experimental results are obtained both for the unloaded cylinder and different payloads. The obtained simulation results are used to gain insights about the possible advantages of the directly driven electro-hydraulic system.

Hybrid powertrain presents a viable solution for reducing fuel consumption achieved by a powertrain electrification while maintaining the independence from the electric grid or a charging station. Due to the fact that skidders belong to the class of forestry machinery which is intended for field use, this operating independence is very important. A simple backward-looking model of a series hybrid powertrain skidder is developed and presented in this paper. The model is then simulated over a number of previously-defined operating missions which include realistic track slopes and variable loads. The results are compared with the results of conventional and parallel hybrid powertrains proposed in previous works. Simulation results show that 17% fuel efficiency improvement is obtainable with the proposed series configuration over the conventional skidder in skid trail driving. Finally, the return of investment period of series hybrid and parallel-hybrid configurations are compared, and their respective advantages and disadvantages are listed and discussed.

Nowadays there are increasing demands in terms of reducing the cost of running forestry machines along with the regulatory pressures for lower exhaust emissions to improve the ecological indices and reduction of acoustic noise in order to better comply with industry ergonomic guidelines. Therefore, the producers of forestry equipment are increasingly interested in electrification of heavy machinery, which can already be seen as appearance of the certain hybrid and electric forestry vehicles. The hybrid power-train apparently offers a favourable solution that can meet the above requirements for the propulsion of articulated forestry tractors, also known as skidders, due to the possibility of using a lower-power diesel engine, along with an additional energy storage system (e.g. battery) and driveline power source (i.e. electric motor). This allows the considered hybrid power-train configuration to operate with higher overall energy efficiency and higher mechanical performance indices over the conventional (diesel engine-based) propulsion system, and notably extended autonomy compared to fully-electrified power-trains. Moreover, hybrid power-train requires a smaller battery with less energy then its purely electric counterpart, which results in lower power-train weight and total installation cost. The precise determination of the energy consumption of different types of forest vehicles working in different operating regimes and under different terrain conditions is necessary to select the proper power-train for a specific application. The future development of electrified forestry vehicles is also a very important research topic in the field of sustainable forestry engineering. Having this in mind, this paper presents a literature review on existing solutions for hybrid forestry vehicle propulsion.

Fluid power networks : proceedings : 19th - 21th March 2018 : 11th International Fluid Power Conference / editor: Hubertus Murrenhoff 11th International Fluid Power Conference, 11. IFK, Aachen, Germany, 19 Mar 2018 - 21 Mar 2018; Aachen : [Mainz], 386-395 (2018)., Published by [Mainz], Aachen

The mobile hydraulic platform is a device used for providing temporary access to people and/or equipment in inaccessible locations and often at higher altitudes. Crane control is conducted from a work platform, which frequently causes a problem since the crane operator disturbs the work of the rest of staff (in case of movie recording, construction work, etc.). Wires are connecting the operator console and the operator computers with each other through a telescope, and due to inevitable cable bending there is a frequent presence of expensive malfunctioning. Wiring malfunctioning is directly connected to the crane reliability, so it is of high importance to reduce it to a minimum. In order to increase the system efficacy, the reconstruction of the mobile hydraulic platform which enables automatic leveling of the work platform and wireless basket control with prevention of capsizing, was designed. The operating program is implemented using the programmable logic controller (PLC), which provides additional system functions implementation.

Pneumatic artificial muscles (PAMs) as soft, lightweight and compliant actuators have great potential in applications for the actuations of new types of robots and manipulators. The favourable characteristics of fluidic muscles, such as high power-to-weight ratio and safe interaction with humans are also very suitable during the process of musculoskeletally rehabilitating patients and are often used in making artificial orthoses. This technology, despite the problems of control relating to nonlinear phenomena, may also have wide future applications within industrial and mechatronic systems. This paper presents several experimental systems actuated by PAMs, which have been designed as test models within the fields of mobile robots, mechatronics, fluid power systems and the feedback control education of mechanical engineering students. This paper first presents the design and construction of a four legged walking robot actuated by pneumatic muscles. The robot is a fully autonomous system with a wireless application platform and can be controlled using a cell phone. Then the paper describes the design and construction of the prototype of an actively-powered ankle foot orthosis. This orthosis device actuated by a single PAM is able to provide the appropriate functions required during the rehabilitations of patients and the loss of mobility. Then the paper focuses on the design and control of a ball and beam system with an antagonistic muscle pair for generating the necessary torque for beam rotation. This mechatronic balancing mechanism falls into the category of unstable, under- actuated, multivariable systems with highly nonlinear dynamics. The final section of the article presents the design and control of a single-joint manipulator arm with pneumatic muscle actuators that enable some new features for the controlled systems.

Mobile robotics is a multidisciplinary engineering field involving knowledge from many research areas, including mechanical and electrical technologies, electronic and software engineering, cognitive and social sciences. Therefore, mobile robotics is one of the most complex and most interesting engineering disciplines, because the people are especially fascinated by machines that can emulate certain human behaviors or devices that mimic natural systems. The system considered in this paper is a four-legged walking robot driven by pneumatic artificial muscles, called WRAPAM, developed in our laboratory to study the dynamic problems related with walking machines, wireless control of mobile systems and application of intelligent control for the robot orientation in an unknown environment with obstacles. Walking robots has added a new dimension as well as posed many new challenges in the mobile robot research because of the problems associated with legged locomotion and achieving system stability. It seems that pneumatic muscles have a great potential for the actuation of new types of robots and manipulators. Pneumatic muscles have a natural elasticity which makes them suitable for use in bionic systems, i.e. biologically inspired design of modern technical systems, applying the process of developing engineering products and devices by taking inspiration found in nature. The realized robot is a fully autonomous system, equipped with Bluetooth function and USB connection for communication with a microcontroller and uses a cell phone or tablet computer based remote control technology. The robot frame is made mainly using square aluminum tubing in order to reduce weight and also a number of hand-made components are machined. The construction of robotic system includes a power unit for supplying compressed air, then pneumatic muscles as actuators for driving the robot joints, control and electronic part of the system and measuring equipment. All components are mounted on the quadruped robot in such a way that maintains the center of gravity of the system. Testing has been performed on the robotic system for the different directions of motion and implementation of walking with the ability to avoid obstacles.

The dynamic characteristics of an electro- hydraulic servo-system are complex and highly nonlinear and, these features significantly add uncertainty to the controller design procedure. Therefore, it is a demanding task to obtain a precise mathematical model of controlled hydraulic drives. In this work, the PID controller parameters have been optimized using Genetic Algorithm (GA) for the position control task of a single-rod hydraulic cylinder. To demonstrate the effectiveness of the control algorithm the experiments have been performed and evaluated on the laboratory model for translational motion control.

This paper focuses on the design and robust nonlinear controller synthesis based on the backstepping approach for force real-time control of a 50-kN hydraulic press. The main feature of the test system is its open hardware structure and easy programmability using different control devices and appropriate control strategies. A nonlinear dynamic model of the hydraulic system interacting with environment has been developed. The press contains a servo-solenoid pressure- control valve for regulating the pressure in the cylinder chamber. The press is equipped with a pressure transducer installed in the cylinder chamber for indirectly measuring the pressing force as well as with a load cell inserted below the piston rod and environment for directly measuring the applied force. On the press is also possible to measure the position of the upper plate by using a micro-pulse linear transducer. The experimental results illustrate that the proposed control technique enables a better tracking performance compared to the conventional PI controllers and guarantees the convergence of the tracking error.

Selection of an appropriate control system is an important decision in the process of designing an electro-hydraulic servomechanism. Nowadays, end- users have a number of options for the choice of control systems and it can sometimes be a bit confusing. The most common applied control system today are the Programmable Logic Controller (PLC), the industrial PC-based Data Acquisition (DAQ) system, and more recently the Programmable Automation Controller (PAC). In this paper, all three of these control methods will be discussed on the example of position control of electro- hydraulic servo mechanisms. The experimental system consists of a main cylinder which is controlled by using a proportional directional control valve, while disturbance (i.e. reaction force) is generated by using a load cylinder with a pressure control valve.

Commercial software for real-time system control is costly and often customized for industrial applications. A clear majority of education institutions and all size companies are turning to open source software instead of using commercial software packages to reduce IT costs. This paper attempts to explore ways to design and implement real-time control of a hydraulic system using open source software (OSS) which includes a Linux-based operating system, the Scilab/Xcos modelling software and associated Real-Time Application Interface (RTAI) and necessary drivers for control and measurement devices. The article reports technical description of the experimental system for translational motion control of hydraulic actuator. The system structure can be divided into the main part, which represents a hydraulic cylinder which is controlled by using a proportional directional control valve and on the part that allows setting different amount of load. The simulation results for position control of hydraulic actuator obtained using Scilab/Xcos free open source software and the experimental results with commercial based platforms using the same set of hardware are given. In order to compare the control characteristics three following devices have been used: CompactRIO system programmed using graphical program LabVIEW, programmable logic controller – PLC using WinCC flexible software and PC with DAQ card using Matlab/ Simulink/RTW program. Also, the other requirements that make up a useful real time application such as reliability, ease of programming and robustness will be discussed. The experimental system presented in this paper consists of reconfigurable components, providing the possibility of performing various control devices which give insight into the physical behavior of the real system and provides great opportunities for education and research in the field of electrohydraulic systems control.

In this work are compared performances of five different robot control algorithms. The following controllers under consideration are: PD controller, PID controller, analytical fuzzy controller, classical adaptive controller and adaptive controller based on neural network. The mentioned controllers are used to control two different robot configurations with two rotational degrees of freedom (in horizontal and vertical plane). The basic performances for control algorithms comparisons are: tracking error, rate of convergence, robustness on structural changes of control object, complexity of stability criterion and complexity of implementation.

The paper presents several experimental systems with pneumatic drive, which have been designed as test models in the field of fluid power systems and feedback control education of mechanical engineering students. Feedback control is one of the most theoretical and mathematically complex engineering subjects and therefore it is of particular importance to demonstrate such abstract concepts using familiar, but interesting physical systems. The paper first reviews different strategies to control the position of pneumatic actuator using various types of valves such as: proportional directional control valves, proportional pressure valves and on-off solenoid valves. Then the paper focuses on three balancing mechanisms driven by pneumatics which are used as experimental systems for the explanation of the effectiveness of advanced control techniques. These balancing mechanisms are the inverted pendulum, the inverted wedge and the ball and beam system, that fall into a category of unstable systems with highly nonlinear dynamics, under- actuated, multivariable systems with non-minimum phase characteristic. The particularity of these balancing mechanisms is their pneumatic drive, which makes them more interesting for education and offers great opportunities to learn design in a mechatronic way. The final section of the article presents an experimental system with pneumatic muscles as actuators that enable some new features of the controlled systems. The paper is accompanied with the typical experimental results obtained during the testing process.

The paper presents three experimental electrohydraulic servomechanisms made with the intention of conducting research and for education’s purpose in the field of conventional, proportional and servo hydraulics and shows some typical experimental results. All three systems have the characteristics of general industrial plants and also include the necessary measuring equipment for realization of control algorithms. The first system is a module for translational motion control of hydraulic actuator. This system consists of a main cylinder which is controlled by using a proportional directional control valve, while the reaction force (i.e. disturbance) is generated by using a load cylinder and a pressure control valve. The rods of these cylinders are coupled by a steel joint. The experimental test rig can also be used to demonstrate the working principle of a conventional hydraulic system. In that case the proportional valve should be replaced with a directional control valve using flexible hydraulic hoses. The second system is a module for the control of force, i.e. a hydraulic press where it is possible to regulate the pressing force. To hold pressure in the cylinder’s chamber and thereby the cylinder’s force to a desired value, a pressure type servo valve is used. The third system is a module for rotational motion control of hydraulic actuator. In this system a hydraulic motor as a control object is used, while the disturbance is generated by using a hydraulic pump whose output pressure is adjusted with a proportional pressure valve. The rods of motor and load pump are tightly connected. The hydraulic motor speed can be controlled both by using a servo valve (throttling control principle) or by controlling the speed of induction motor and supply pump by means of a frequency converter (volumetric control principle). For the implementation of the control process various control devices were used, such as CompactRIO system programmed using graphical program LabVIEW, PLC (programmable logic controller) and a control computer with DAQ card using Matlab/Simulink/RTW program.

This paper reports the design and control of a 50 kN hydraulic press which is made for experimental verification of control algorithms as well as for educational purposes. The press contains a servo-solenoid pressure control valve for regulating the pressure in the cylinder chamber and thus the force of hydraulic press. The system is equipped with a pressure sensor installed in the cylinder chamber for indirectly measuring the pressing force. At the considered press it is also possible to measure position of the upper plate by using a micro-pulse linear transducer. This created conditions for the realization of a position/force hybrid control algorithm. The control algorithms and monitoring process are implemented on a real-time hardware board. They are programmed in Matlab/Simulink environment using Real-Time Workshop tool for generating the C code and building an executive program. Based on the experimental results it can be concluded that electrically actuated control components supported by appropriate computer programs enable the realization of improved characteristics of systems required in modern industrial plants.

This paper presents a conjugate gradient-based algorithm for feedback min-max optimal control of nonlinear systems. The algorithm has a backward- in-time recurrent structure similar to the back propagation through time (BPTT) algorithm. The control law is given as the output of the one- layer neural network. Main contribution of the paper includes the integration of BPTT techniques, conjugate gradient methods, Adams method for solving ODEs and automatic differentiation (AD), to provide an effective, novel algorithm for solving numerically optimally min-max control problems. The proposed algorithm is applied to the rotational/translational actuator (RTAC) nonlinear benchmark problem with control and state vector constraints.

The main principles for motion control in modern machinery design that use hydraulic energy are throttling principle by using constant displacement pump and proportional or servo valve in line with the actuator, and volumetric control principle by using constant-speed electric motor in combination with a variable displacement pump or variable-speed induction motor in combination with a constant displacement pump. By using a directional control valve in the hydraulic circuit for controlling the flow to and from the hydraulic actuator a constant quantity of oil is always required which leads to the oil being more heated and more electrically energy is consumed. Thus, regularly occur problems with heating oil and usually a separate heat exchanger is used in the hydraulic system. This conventional control principle is associated with significant loss of energy ; however a good dynamic behavior of the control system can be achieved. Increased use of volumetrically controlled hydraulic energy where speed of the induction motor is adjusted by the frequency converter in a closed loop control is motivated by its large range of the system overall efficiency and its favorable price, which is enabled by using modern microprocessor technology and digital control theory. In the case of frequency controlled drive only the amount of fluid required to achieve the desired speed has to be supplied, and this smaller flow of fluid means lower energy consumption, which makes an example of modern solution in electro-hydraulic technology application. The aim of this article is the comparison of these two control concepts on the example of hydraulic motor speed control. The actuator speed can be controlled both by using a servo valve and by controlling the speed of the induction motor and pump by means of the frequency converter and control computer with digital electronic card. The control strategies will be experimentally validated on a rotary hydraulic system, which is designed at our Laboratory. The controller is tuned according to damping optimum method in order to achieve precise speed control of the hydraulic motor. The control algorithms and monitoring process are implemented on a real-time hardware board that is programmed in Matlab/Simulink environment using Real-Time Workshop program. The experimental results show that the displacement-controlled system can produce satisfactory response characteristics and yield an effective trade-off between control performance and energy efficiency of the control system.

Rad objašnjava nastanak i izvedbe umjetnih pneumatskih mišića, te daje primjere njihove primjene u području robotike, fizioterapije i industrijske automatizacije. Način rada pneumatskih mišića objašnjen je na primjeru originalno konstruirane ruke manipulatora koji koristi pneumatske mišiće kao aktuatore za ostvarenje reguliranog gibanja ruke.

The article presents three experimental systems made for the purpose of conducting research in the field of proportional and servo hydraulics, as well as the purpose of training students. The first system is a module for controlling linear motion of hydraulic actuator. The control system consists of a main cylinder which is controlled by using a proportional directional control valve that can supply the cylinder with hydraulic fluid. Disturbance is generated by using a pressure control valve and a load cylinder, which produces a reaction force. Two cylinder rods are coupled by a steel joint. The second system is a module for the control of force, i.e. a hydraulic press where it is possible to regulate the force of compressing. To hold pressure in the cylinder’ s chamber and thereby the cylinder’ s force to the desired value, a pressure type servo valve is used. The third system is a module for controlling rotational motion of hydraulic actuator. In this system a hydraulic motor as a control object is used, where the disturbance is generated by using a hydraulic pump whose output pressure is adjusted using the proportional pressure valve. Motor and pump rods are tightly connected. The hydraulic motor speed can be controlled both by using a servo valve (throttling principle) and by controlling the speed of the induction motor and supply pump by means of the frequency converter and control computer with digital electronic card (volumetric control principle). All three systems also include measurement and control equipment for the realization of control algorithm. The experimental verifications are made using these three experimental systems – the module for linear motion control, the module for control of force and the module for rotational motion control that have been made at our Laboratory. The experimental results for controlling the position of hydraulic cylinder, for controlling the force of hydraulic press, as well as for controlling the speed rotation of hydraulic motor are displayed. The control algorithms and monitoring process are implemented on a real-time hardware board that is programmed in Matlab/Simulink environment using Real-Time Workshop program.

This paper deals with the position control of a hydraulic actuator regulated by a proportional directional control valve. The control algorithms based on the proportional-derivative controller have been applied to a specially designed two-channel electro-hydraulic servo system, which has the capacity to experimentally simulate common circumstances of a typical fluid power circuit. The first system includes the positioning hydraulic cylinder controlled using the proportional valve, a displacement measuring system and a control device in a closed-loop system. In order to add further realism in the control system a second double acting hydraulic cylinder is used to generate the disturbing load. The effectiveness of the proposed control algorithms is demonstrated for both moving directions as well as for both unloaded and loaded system. The results of the experimental testing have shown that for some industrial applications a relatively good motion control performances can be achieved using a proportional valve as a control component with a simple control algorithm, but for the case of changing operating conditions, some advanced control approaches should be used.

Many WEB sites offer different approaches for learning engineering and scientific topics, but is there such an online system that offers the way for collaborative solving of benchmark problems in engineering and scientific domain. Here we describe a novel online system that enables large teams of engineers to solve their problems. In order to describe and solve the problems, programming languages like Matlab, C++, Python, and PHP etc. are used. Insight into solving efficiency is achieved by comparing different programming algorithms for the same benchmark problem, so the best algorithm can be determined.

The object of this poster presentation is to render an educational manual on numerical integration which is stored in a separately developed PDF format with interactive forms. The novelty consists in the following: a student reads the mathematical contents (author's diploma work) individual topics on numerical integration and studies the examples of every algorithm. If he/she is online, he/she is o ered the possibility to perform each and every pro- gram example (written in Python) over Internet. A special computer system Scriptrunner serves for this purpose ; however, the user/reader needs not to be familiar with the program. The program is executed by the Scriptrunner and results are returned to the sender. In this way, the new educational possibility is accomplished: every reader reads the manual in his own way, i.e. instead of only one example arbitrarily many examples are available, depending on the input data sent for the program. The reader of the PDF document needs not to have any program installed on his computer except the PDF viewer and an Internet browser. This manual includes algorithms and programs for Newton-Cotes formulas ; simple, composite and recursive trapezoidal rule ; Simpson's rules, Romberg in- tegration, Gaussian integration formulas (Gauss-Chebyshev, Gauss-Laguerre and Gauss-Hermite quadrature) etc. Likewise, many other manuals may be rendered available, too ; the manuals from all mathematical elds using com- puter and algorithms for them may be solved in any programming language. This novelty provides a new dimension for the future digital textbooks.

The main focus in this paper is on modeling and computer simulations of hydraulic systems for achieving a linear or rotary actuator motion, which are mostly used for high-power industrial applications. The hydraulic servo systems are very important systems for control applications because they take the advantages of both the large output power of traditional hydraulic systems and a high servo control response of electric systems. A nonlinear dynamic model for both translational and rotational motion of hydraulic actuator has been derived, which can be used in simulation studies of dynamic behavior of system and for advanced controller design. The hydraulic control system model has been derived as coupled sets of nonlinear algebraic and differential equations, which includes the main phenomena of physical system. This form of modeling equations has been resulted in a block-oriented system model. The simulation model includes the flow and force equations necessary to describe dynamic behavior of the control system and allows the prediction of performance of hydraulic system through computer simulation. A simulation model depicting the two control systems has been built, which may be used for an easy comparison of dynamical behavior of common hydraulic systems in industry. The model also contains several important dynamic characteristics those substantially influence the performance of the system within the operation range. Model development and preliminary experimental testing on laboratory setup are in progress.

The distance educational tools have been developing with the fact that the topics for simulations can demand special approach. The only thing required to use the full power of it is a Web browser which supports frames and JavaScript. Interface is straight-forward and simple, which facilitates interaction between a professor and student. Using teaching experience the simulation toolbox will offer easy learning of simulations with the approach by example. Two approaches of simulation learning are available: the first one per which a student has to write for the partly set assignment one part of the program code and the second one per which student analyzes and learns by modification of parameters (input data) the obtained simulation results.

The paper presents three balancing mechanisms, which have been utilized as experimental systems in the control education of mechanical engineering students. Their uniqueness is the pneumatic drive, which makes them more affordable, simpler and more interesting to control. These balancing mechanisms are the inverted pendulum, the inverted wedge and the ball and beam, while the pneumatic infrastructure includes variety of valves. The paper describes these experimental systems and some methods applied to control them.