Tihomir Zilic

Bio: Tihomir Zilic is an academic researcher from University of Zagreb. The author has contributed to research in topics: Nonholonomic system & Pneumatic actuator. The author has an hindex of 3, co-authored 7 publications receiving 58 citations.

High speed solenoid valves in pneumatic servo applications

Abstract: Pneumatic driving systems are mainly used in industrial applications where the moving parts are usually fixed by the mechanical stops. For flexible and precise positioning tasks of pneumatic drives relatively expensive proportional valves have been implemented. In order to develop cheaper pneumatic servo systems, the employment of low-cost on/off solenoid valves have received considerable attention. But, the traditional technologies used in on/off solenoid valves manifest different problems caused by the electric and thermal effects, inertial forces of their mechanical parts and friction phenomenon. However, it seems that innovative technology used in fast switching solenoid valves gives better possibilities in control of pneumatic systems due to their negligible internal friction and modular architecture. In this paper a control method based on pulse-width-modulation algorithm for position control of a pneumatic actuator with high-speed solenoid valve is considered and experimentally verified.

Simultaneous stabilization and trajectory tracking of underactuated mechanical systems with included actuators dynamics

Abstract: The paper deals with a novel control algorithm for simultaneous stabilization and trajectory tracking of underactuated nonlinear mechanical systems (UNMS) with included actuators dynamics. Simultaneous stabilization and trajectory tracking refer to arbitrary chosen actuated and unactuated degrees of freedom (DOF) of the system. The proposed control approach can be applied both to the second-order nonholonomic systems and the systems with input coupling, while a general model of actuators dynamics includes electrical, pneumatic, and hydraulic drives. Control law is based on linear combination of two control signals, where the first signal is designed to separately control only actuated DOF, and second to separately control only unactuated DOF. Simulation example of rotational inverted pendulum driven by electrical DC motor is presented, showing the effectiveness of the proposed approach.

Frequency-shifting-based stable on-line algebraic parameter identification of linear systems

Abstract: In this paper a new approach to algebraic parameter identification of the linear SISO systems is proposed. The standard approach to the algebraic parameter identification is based on the algebraic derivatives in Laplace domain as the main tool for algebraic manipulations like elimination of the initial conditions and generation of linearly independent equations. This approach leads to the unstable time-varying state-space realization of the filters for the on-line parameter estimation. In this paper, the finite difference and shift operators in combination with the frequency-shifting property of Laplace transform is applied instead of algebraic derivatives. Resulting state-space realization of the estimator filters is asymptotically stable and doesn’t require switch-of mechanism to prevent overflow of the estimator variables. The proposed method is especially suitable for applications in closed-loop on-line identification where the stable behavior of the estimators is a necessary requirement. The efficiency of the proposed algorithm is illustrated on three simulation examples.

A case study in distributed control: Elastically interconnected seesaw-cart systems

Abstract: As the main contribution of the paper, we present a network of electro-mechanical systems as a suitable platform for education, testing and verification of real-life implementation of decentralised and distributed control solutions. The overall system (network) consists of a set of elastically interconnected seesaw-chart systems. Additionally, suitable, control oriented, structured model of the system's dynamics is derived and presented. Results of a case study in distributed control are presented, together with comparison with achievable centralized control behaviour.

Educational Web collaboration system

Abstract: This work describes a set of modules for distance education. These modules have been developed by students as professional applications, and some of them are tested in the technical office. Modules can work as independent applications, but also can work connected and in this case they tend to make a system that enables users to elaborate, publish and exchange documents simultaneously with users communication, write and execute program code online, and to have knowledge testing - Web exams

Decomposition strategy-based hierarchical least mean square algorithm for control systems from the impulse responses

Abstract: In this research, the issue of parameter estimation for control systems is considered to develop a highly efficient estimation approach for the purpose of satisfying the need of industrial process ...

Design and control of a manipulator arm driven by pneumatic muscle actuators

Abstract: It seems that the pneumatic artificial muscles (PAMs) have a very great potential in industrial applications for the actuation of new types of robots and manipulators. Their properties such as compactness, high strength, high power-to-weight ratio, inherent safety and simplicity are worthy features in advanced robotics. In this paper we describe the design, construction and experimental testing of a single-joint manipulator arm actuated by pneumatic muscle actuators. An antagonistic muscle pair is used in a linear translational sense to produce a force or in a rotational sense to produce a required torque on the pulley. The concept, operating principle and elementary properties of pneumatic muscle actuators are explained. A nonlinear mathematical model of the manipulator arm driven by pneumatic artificial muscles and controlled with proportional control valve is derived, which is used in a numerical simulation program. The experiments were carried out on practically realized manipulator actuated by pair of muscle actuators set into antagonism configuration.

Methods and systems for facilitating the distribution, sharing, and commentary of electronically published materials

Abstract: The present invention shows methods and systems for facilitating the distribution, sharing and commentary of electronically published materials such as educational textbooks. The system incorporates a common system for receiving and publishing the documents. Features of the system including layering, iconic mark-up, user notes and comments, user communication and documents/action sharing.

Review on modeling and controller design in pneumatic actuator control system

Abstract: Pneumatic actuators are highly nonlinear characteristics and uncertainties make it difficult to achieve high performances. The objective of this paper is to present a brief overview of pneumatic actuators based on modeling and control strategies that has been proposed by various researchers. Before the main discussion, some background information will be presented in a relation to pneumatic actuators. This review concludes with a short summary INTERNATIONAL JOURNAL ON SMART SENSING AND INTELLIGENT SYSTEMS VOL. 4, NO. 4, DECEMBER 2011

Simulation and experimental control of a 3-RPR parallel robot using optimal fuzzy controller and fast on/off solenoid valves based on the PWM wave.

Abstract: In this paper, a robust optimal fuzzy controller based on the Pulse Width Modulation (PWM) technique is proposed to control a laboratory parallel robot using inexpensive on/off solenoid valves. The controller coefficients are determined using Modified Cuckoo Optimization Algorithm. The objective function of this method is considered such that the results show the position tracking by the robot with less force and more efficiency. Regarding the results of experimental tests, the control strategy with on/off valves indicates good performance such that the maximum value of RMS of error for a circular path with increasing force on the system is 3.1mm. Furthermore, the results show the superiority of the optimal fuzzy controller compared with optimal PID controller in tracking paths with different conditions and uncertainties.