Pavol Bistak

New Thermo-Optical Plants for Laboratory Experiments

Abstract This paper explains motivation and gives a brief development history of a laboratory model of thermo-optical plant. Then it continues with a short description of linear and nonlinear identification and control experiments that may be carried out with the recently innovated model directly in a classroom from the Matlab/Simulink environment, or remotely via Internet.

Noise attenuation motivated controller design. Part II: Position control

This paper treats a noise attenuation motivated position controller design outlined in [1]. This modular approach to a filtered PD and a disturbance observer based filtered PID (FPD and DO-FPID) control design, including an experimental evaluation of an optimal filter degree choice, is extended to a constrained control grounded in the invariant set approach [2]-[4]. Loop performance is evaluated by recently introduced measures for deviations from monotonic and two-pulse shapes of transients typical for control of plants with dominant 2nd order dynamics. The analysis shows that a simplified disturbance observer (DO) based constrained filtered PID controller (DO-CFPID) derived for a double integrator plant model gives an interesting performance also for constrained integral systems with a stable mode. It remains simple and it offers an excellent performance also from the point of view of the noise attenuation versus speed of transients.

Blended learning course "Constrained PID control"

Abstract In the engineering education we are often confronted with the question, if it is appropriate for using e-learning. This paper brings a brief overview of the blended-learning course “Constrained PID Control”, explains what, why, how and for whom and “zooms in” some circumstances of its development. Finally it leads to a counter-question: Is it even possible to achieve a high quality education without e-learning, just with using a chalk and blackboard?

Matlab and Java based virtual and remote laboratories for control engineering

Virtual and remote laboratories play an important role in the education process of engineers. Their expansion is closely connected to the growth of Internet. The paper deals with the structure of virtual and remote laboratories. It explains the main components of the client server application and describes the data exchange between this application and Matlab/Simulink software based on COM technology.

Advanced remote laboratory for control systems based on Matlab and .NET platform

Virtual and remote laboratories has become a standard part of education and research. Although nowadays there exist many examples how to build them it is still advantageous to create new solutions that are universal, more flexible and comfortable to use. This paper describes features of a new application developed for the purpose of remote laboratories. It has been written in the C# programming language and it is based on the Microsoft .NET technology and Matlab/Simulink platform. In comparison with older versions the new one uses new progressive methods of .NET technology for communication and user interface design. This allows simplification of its construction, easy modification according to new requirements as well as a simple creation of client applications. The new remote laboratory application facilities are demonstrated on several real systems.

Time Sub-Optimal Control of Triple Integrator Applied to Real Three-Tank Hydraulic System

Control of nonlinear systems with input constraints is an interesting topic of control theory that must be solve adequately because of the presence of constraints in almost each real system. There are many authors and several techniques trying to solve this problem (anti-windup structures, positive invariant sets, variable structure systems, global, semi-global and local stabilization of systems with constraints, optimization problems solved by linear matrix inequalities).

Comparing two approaches to nonlinear time-delayed 1st-order plants control

The paper introduces two new approaches to control of simple but frequently considered nonlinear plants with a time-delayed dominant first-order dynamics. To guarantee a consistent performance over a broader operating range, in dealing with nonlinear plants, typically different gain scheduling approaches may be used as e.g. the exact linearization, velocity linearization, flatness-based model-free PID control, control based on generalized transfer functions to nonlinear systems, etc. By considering example of a time delayed one-tank liquid level control in a hydraulic plant the paper introduces a new alternatives to these traditional approaches based on a generalization of the exact linearization by using two types of linearized plant models. They allow to consider unmodelled dynamics and a nonlinear predictive disturbance-observer (NPDO) based integral action. The resulting two-degree-of-freedom model-based control shows new possibilities in designing transients with required monotonicity properties and different degrees of optimization.

Tuning of an iP controller for a time-delayed plant by a performance portrait method

This paper deals with a performance analysis and optimal tuning of an intelligent proportional (iP) controller for the first order time delayed plants. iP control represents the simplest solution used within the so called “model free control”. Although it has been primarily developed for more complex nonlinear plants, its basic performance analysis may preferably be carried out in a simple linear setup by considering an integral time delayed plant with an input (load) disturbance. The corresponding disturbance observer is based on a finite-impulse-response (FIR) filter, which makes an analytical tuning inapplicable. The paper shows, how it may be carried out by the performance portrait method. Inspired by analogous problems solved already in a traditional disturbance observer based control, comparison of both approaches shows new interesting features of the “model free” control under time delays.

Model reference control of a two tank system

This paper deals with a new approach to the control design for a second-order nonlinear plant with time-delays. There are several methods that can solve this problem: the gain scheduling, exact lienarization, generalized transfer functions for nonlinear sysyems, etc., to name just few. The advantage of the solution proposed in this paper consists in its simplicity, modularity that can be used for a broad class of nonlinear systems and relatedness to several well established approaches that can be considered as its limit cases. Starting from a pole-assignment PD controller for the double-integrator plant generalized for a constrained control and equiped by a gain scheduling to respect the nonlinear plant dynamics, its structure is gradually extended by a model reference control and finally, by a nonlinear disturbance observer taking into account filtration of noisy signals and the non-modelled time-delays always present in control circuits. By using an example of a two-tank liquid level control in a hydraulic plant, performance of the resulting two-degree-of-freedom model reference control of nonlinear time-delayed systems with an integral (I) action will be evaluated by standard criterions.

Model reference control of nonlinear time-delayed 1-st order plants

This paper deals with a new approach to the design of a two-degree-of-freedom controller for a first-order nonlinear plant with time-delays. There exist several traditional methods that can solve this problem (gain scheduling, exact linearization, generalized transfer functions for nonlinear systems, etc.). The advantage of the solution proposed in this paper consists in a simple and modular controller design that can be used for a broad class of nonlinear systems. In order to be able to comprise all required steps into a single conference paper, the overall design and the resulting performance of the proposed model reference control of nonlinear time-delayed systems will be documented by an example of a one-tank liquid level control in a real hydraulic plant. Starting from a basic P controller, its structure is gradually extended by a model reference control and finally by a nonlinear disturbance observer taking into account both the filtration of noisy signals and the time-delays always present in control circuits.