XXIX. ASR '2004 Seminar, Instruments and Control, Ostrava, April 30, 2004 333 Laboratory of Advanced Simulations WAGNEROVÁ, Renata Ing., Ph.D., Katedra ATŘ-352, VŠB-TU Ostrava, 17. listopadu, Ostrava - Poruba, 708 33 renata.wagnerova@vsb.cz Abstract: This contribution describes laboratory models and types of experiments at the Laboratory of Advanced Simulations on Department of Control Systems and Instrumentation, the VŠB-Technical University of Ostrava. The lab contains five models; three of them are produced by the Humusoft firm (helicopter, ball and plate, levitation in magnetic field), remaining two models were designed as diploma works for position control of levitating systems in magnetic field. Keywords: simulations, control in real time, MATLAB 1 Introduction The laboratory of advanced simulations contains five models and is used for individual students work in the field of automatic control. It allows not only the simulations experiments but also verification of different kinds of control (convectional PID controllers, robust control, sliding modes control, ) directly on real systems. The control algorithms are realized in program system MATLAB. It is a powerful technical language for scientific computing, modeling, simulation, data visualization and data analysis. The MATLAB can be used also for laboratory systems control, if there is REAL TIME TOOLBOX installed. This toolbox allows immediate access to external analog and digital signals, data acquisition and their further processing. It is possible to experiment with signal processing, control system design and similar tasks directly from MATLAB command window or the SIMULINK environment using a block library. The connection is realized with data acquisition cards (AD 512) or the serial communication port (RS-232). 2 Levitation in magnetic field There are two laboratory models (Figure 1), which were realized as diploma works, the following part gives a shortly presentation of those models and experiments, which they allow. Both models are one-dimensional strongly nonlinear unstable system. The first system (according to the scheme a) consists of a coil, levitating a steel cylinder in a magnetic field. The position of the steel cylinder is sensed by a fibre optic position sensor connected to an A/D converter. The second structure (scheme b) consists of coil, steel solid connected to the basis and levitating in magnetic field. In this case position is measured by inductive sensor Micropulse connected to the A/D converter. In both structures the coil is driven by a power amplifier connected to a D/A converter. The basic control task is to control the position of the cylinder/flap freely levitating in the magnetic field of the coil. The models are connected to PC by data acquisition card AD512, for which driver is installed in REAL TIME TOOLBOX. This card enables work with a sampling frequency up to 100 khz and output/input ranges. The laboratory models work with the output/input range 0 10V and sampling frequency 1 khz.
XXIX. ASR '2004 Seminar, Instruments and Control, Ostrava, April 30, 2004 334 U 6 5 Legend: 1 - stand, 2 fiber optic position sensor, 3 steel bar, 4 tube ensuring the vertical movement, 5 pole piece of core coil, 6 - electromagnet. 4 3 2 a.) 1 Legend: 1. stand 2. position sensor 3. electromagnet 4. levitating subject 5. subject guidance ensuring one degree of freedom 6. initial position b.) Figure 1 Scheme of models for levitation in magnetic field For user-friendly experiments a control module was created in the environment MATLAB 5.3/REAL TIME TOOLBOX 2.61 and allows experimenting with a number of different control algorithms based on classical and modern control theory. For properly starting of module, first of all, the path to working directory must be ordered and then the program started up with typing model at the MATLAB prompt. The main window (Figure 2) opens. It contains these buttons: Grafy setting window with graphs (choice of represented variables). Parametry setting control algorithms and its parameters. Uložit saving chosen variables (setting file name, type, variables). Nápověda help. Nastavení setting experiment parameters (time, sample period). Start - run position control. Konec closing module.
XXIX. ASR '2004 Seminar, Instruments and Control, Ostrava, April 30, 2004 335 Figure 2 MATLAB support for control in real time 3 Helicopter model The system consists of a body, carrying two propellers driven by DC motors, and a massive support. The body has two degrees of freedom. Both body position angles (elevation and azimuth) are influenced by rotation of propellers. The axes of a body rotation are perpendicular. DC motors are driven by power amplifiers using pulse width modulation. Both angles are measured by IRC sensors. Centre of gravity is changed by moving small weight along the main horizontal axis of helicopter by a servomotor. The mathematical model of the helicopter system is a typical MIMO system (two inputs, two outputs) with significant crosscouplings. As the third input can be considered high speed moving of centre of gravity controlled by servo system. The system is designed to be controlled by digital controllers with help of program module (exe file) or Simulink. Figure 3 Laboratory model of Helicopter
XXIX. ASR '2004 Seminar, Instruments and Control, Ostrava, April 30, 2004 336 4 Ball and Plate model The scale model demonstrates control problems associated with unstable systems. The system consists of a plate pivoted at its centre such that the slope of the plate can be manipulated in two perpendicular directions. A servo system consisting of motor controller card (MF614) and two stepper motors is used for tilting the plate. Intelligent vision system is used for measurement of a ball position (CCD camera, digital image processing with 256x256 pixel resolution; standard PC ISA car, fast gray scale frame grabber FG 201, input: composite PAL video signal, resolution: 256x256 or 512x512, 256 levels of gray). The basic control task is to control the position of a ball freely rolling on a plate. The Ball&Plate system is a dynamic system with two inputs and two outputs. Both coordinates can be controlled independently as their mutual interactions are negligible due to low velocity and acceleration rate of the ball movement. The system is naturally sampled as both actuators and sensor are of a digital, discrete time nature. The system is designed to be controlled by digital controllers (PID controllers) with help of program module (exe file) or Simulink. Figure 4 Laboratory model Ball and Plate
XXIX. ASR '2004 Seminar, Instruments and Control, Ostrava, April 30, 2004 337 5 Conclusions The laboratory models for levitation in a magnetic field are control by a module created in the environment MATLAB/REAL TIME TOOLBOX. The created module facilitates an experiment with laboratory model, while users (students) can control the position of the levitating steel cylinder/steel solid without knowledge of communication protocols or programming in the environment MATLAB. They can learn how to design parameters of conventional PID controllers and also a non-standard control algorithm (sliding mode controls). The laboratory models Helicopter and Ball and Plate are controlled by module or simulink file, both allow experiments with conventional PID controllers. Students can learn how to design parameters of conventional PID controllers for MIMO systems (two inputs/two outputs). In this year the experiments will be expend of using non-conventional control algorithms like as robust control, sliding mode control, fuzzy control. The presented results have been obtained during the solving of research project MSM272300012. References DANISZ, R. Design and realisation of laboratory control system for ploblem Levitation of steel solid. Ostrava: Department of Control Systems and Instrumentation, Technical University of Ostrava, 2002. 62 pages. Final thesis, Supervisor: Wagnerová, R. KLANER, P. Control Systems Synthesis by Using Experimental Models. Ostrava: Department of Control Systems And Instrumentation, Technical University of Ostrava, 2000. 64 pages. Final thesis, Supervisor: Wagnerová, R. WAGNEROVÁ, R. Synthesis of Complex Nonlinear Control Systems. In: Proceedings of 5 th International Scientific Technical Conference Process Control 2002. Kouty nad Desnou, Czech Republic, Univerzita Pardubice. 9. 12. 6. 2002, pp. 156 (plný text na CD 148/1-148/6). ISBN 80-7149-452-1. WAGNEROVÁ, R. Nonlinear Control Systems Synthesis. In Proceedings of 3 rd International Carpathian Control Conference. Ostrava : VŠB-TU Ostrava, 27. - 30. 5. 2002, p. 751-756. ISBN 80-248-0089-6.