Mario Essert

Robust H∞ position control synthesis of an electro-hydraulic servo system

This paper focuses on the use of the techniques based on linear matrix inequalities for robust H(infinity) position control synthesis of an electro-hydraulic servo system. A nonlinear dynamic model of the hydraulic cylindrical actuator with a proportional valve has been developed. For the purpose of the feedback control an uncertain linearized mathematical model of the system has been derived. The structured (parametric) perturbations in the electro-hydraulic coefficients are taken into account. H(infinity) controller extended with an integral action is proposed. To estimate internal states of the electro-hydraulic servo system an observer is designed. Developed control algorithms have been tested experimentally in the laboratory model of an electro-hydraulic servo system.

High speed solenoid valves in pneumatic servo applications

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.

Application of SSTT control algorithm for underactuated: surface vessel, PPR manipulator and pneumatically actuated slider-inverted pendulum

The paper deals with verifications and validation of the control algorithm for simultaneous stabilization and trajectory tracking of underactuated nonlinear mechanical systems. A simplicity, universality, and effectiveness of the control law are shown on simulations to the both multibody second-order nonholonomic systems (a planar PPR manipulator and an inverted pendulum) and underactuated systems with forces/moments input coupling (a surface vessel). An experimental verification has been made on the novel pneumatically actuated slider-inverted pendulum with included friction effects. Also, an actuator compensator is constructed and implemented for this highly nonlinear experimental setup to avoid the increase of the system’s relative degree in the closed control loop, and to avoid the unnecessary time derivation of the system’s functions with non-differentiable Coulomb friction effects. Graphical Abstract

Educational Web collaboration system

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