The nonlinear, unstable controlled member is a freely hovering metal body which is held at the highest point by an electromagnet. The position of the metal body, corresponding to the distance between the body and the magnet, is measured by an inductive distance sensor (LVDT = Linear Variable Differential Transformer) and is passed to the controller as the actual value. The controller passes the actuating signal to the control member which then provides the required change of position. The position setpoint can be varied in the range 0-5mm.
In the standard version the MS40 Laboratory Setup is supplied with a special analog controller. The controller is integrated as an operational amplifier circuit together with the necessary electronics in a 19" housing. Basic control principles can be demonstrated with the standard version. It can be shown that the unstable system can be stabilized by the application of a suitable controller. Furthermore, the effect of the control parameters on the behaviour of the system (disturbance/setpoint step response) can be impressively displayed.
System variables such as the position, external control signal, current (monitored) and analog setpoint are directly accessible at the measurement outputs. In addition by means of a switch the control signal is connectable to an arbitrary external controller like an analog controller or a PC with an A/D-D/A-converter-card. The documentation includes sections for assembly and start-up, the theoretical background, the description of the system with the mathematical model of the plant, the technical data, background of the PIDT controller, the operating instructions for the controller program as well as the guidelines for the practical course with solutions. The MS40 Laboratory Setup is therefore suitable for teaching and demonstration purposes in all fields of control engineering.
A PC version is available with the option 40-02 alternative to the built-in analog controller. It contains the plug-in card MF634 for a PC with PCIe slot.The associated practical course program running under WINDOWS (WINDOWS 7-10) is designed for engineering student laboratories or demonstrations. The adjustment of controller parameters, the determination of characteristics or the recording of step responses with respect to set point changes or disturbances can be selected by means of a menu.
The graphic output of recorded data may be sent to a window. Its content may be printed, saved as a WMF file or copied into the clipboard.
The controller program provides a PIDT controller. Pull down menus which are activated by a mouse and/or by keyboard are used for a comfortable adjustment of controller parameters, set points, measurement acquisition as well as plant identification. In addition the program allows to store the adjusted or measured plant and controller parameters to a file. Those data can be loaded later on. The included practical course is carried out with analog/digital PID controllers. The influence of the controller parameters on the behavior of the closed control loop is evaluated. The examination of stability is based on the root locus method and the bode diagram.
By means of the PC plug-in card MF634 of Humusoft the laboratory experiment "MS40 Magnetic Suspension" can easily be integrated in Matlab/Simulink with real-time environment. The user now has the opportunity to test its own controller designs under Matlab/Simulink.
With the option 40-03 a standard controller program in C++source in combination with library routines for graphic output, controlling the sampling period as well as controlling the PC adapter card is available. The controller program can be modified by the user for research purposes. The input/output routines contain among other things the driver for the A/D-D/A converter card which comes with option 40-02. The range of functions and operating possibilities of the standard controller program is equivalent to the above mentioned practical course program. The Embarcadero C++ Builder V10 is required.
Technical data are subject to change (Date 4-December-2017)