Laboratory Experimentation And Real Time Computing: An Integrated Environment

This paper presents an integrated environment for rapid control prototyping that allows rapid realization of novel designs, from the initial design phase until the final steps of code generation. It uses a collection of tools that include both software (MATLAB/Simulink) and an off-the-shelf hardware (dSPACE DSP DS1104). The integrated environment presented in this paper has many educational advantages as compared to multi-environment settings. The main features of this environment are: 1) controller code can be generated automatically for hardware implementation; 2) different languages can be used to describe different parts of the system. In particular, Simulink block diagrams can be used to define the control structure, tune the controller parameters and reference signals online, while the experiments are in progress without having to rebuild and download a new Simulink model to the DS1104 board; and 3) ease of operation especially by means of a simple graphical user interface. The laboratory environment was used in teaching an introductory laboratory control course. The objective is to promote control-systems education with laboratory experimentation. Course assessment showed a high level of students' satisfaction with the course content and its structure. The students stated that the process helped them to apply modern design tools to a real time system. INTRODUCTION The study of control systems has been cited as a subject that is heavily based on abstract mathematical concepts 1 . This theoretical base has been considered a major problem with students unable to apply the coursework that is completed in the classroom to real-life systems. This problem has not gone unnoticed in the field of education today, and there have been great leaps in the creation of more “hands-on” teaching methods that lend themselves to industrial applications 2 . Throughout schools and universities within the United States and internationally, there has been growing interest in the use of practical control concepts in and beyond the classroom. This has been accomplished to a large extent through the use of laboratory courses, with incorporation of technology tools that enable students to work on different real-world control configurations. This adjustment to incorporate the more practical format into the classroom has taken different forms throughout the academic world. In the Technische Universiteit Eindhoven, The Netherlands, the modeling of control systems is an important part of their Bachelor’s in mechanical engineering degree curriculum 3 . There is a gradual introduction to real world systems that begins with a lower level course where the students are introduced to mathematical concepts and A/D conversion and ends with a final year project that incorporates the manipulation of various feedback controllers to accomplish a specific task. In this way the students are transported from the theoretical understanding to actual applications by the end of the degree program. At the Department of Automatic Control at the Lund Institute of Technology in Sweden 4 , all disciplines in their four and a half year Master of Science degree, excluding chemical and biotechnical engineering, must complete a basic control course. The second half of this course involves the assignment of control projects in conjunction with the lectures, which is another clear indication that there is great importance placed on the practical applications of control theory. All control courses have three mandatory four-hour labs that make use of mobile desktop processes and standard computing equipment. The Institute is also P ge 14830.2 2 credited with having “pioneered the teaching of real-time programming and real-time systems,” 4 . At the University of Maryland, College Park 5 , their main focus with regard to the practical application of control systems is a multidisciplinary senior-level course (in the Bachelor’s degree program of computer and electrical, mechanical and aerospace engineering) that combines digital control and networks with information technology. One of the major advantages seen at Maryland is in the use of an all-digital controls lab, which allows controller-implementation using relatively cheap computers. Another article 6 promotes the control-systems laboratory at the University of Illinois at Urbana-Champaign. An appealing quality of this facility is that it is shared among several departments. At Howard University, the study of control has been accelerated by the integration of motion controls laboratory, which affords the student an opportunity to interact and utilize an “embeddable dSPACE digital signal processor (DSP)-based data acquisition and control system 7 . This is seen by Howard University as a solution to the need for a cost effective, “hands on instructional laboratory” which would “adequately provide hands on experience necessary for effective learning.” Another key aspect of this laboratory is the close integration of the conventional simulation tools MATLAB and Simulink TM . These are just some examples of the manner in which the institution of education has modified itself to incorporate the need for practical applications of control concepts. With regard to the software tools that have become popular for the creation and modeling of control systems in the lab, it has been found that many commercial entities offer several products that can be used in the laboratory environment to illustrate control systems. In each lab, there exists some consistency in the tools of choice. The MATLAB software package is undoubtedly the most common and most powerful tool for creating an environment for control systems design and simulation 2-4, 7 . There are several applications under MATLAB that have been used in this design and simulation process. These applications include QadScope and Wintarget 3 . QadScope is a scope-like application for measuring purposes. It supports a wide range of inputs and outputs with built-in frequency-domain analysis, while WinTarget is “a real-time target running under Simulink/Real-Time Workshop”. The two tools work together to create a real-time application that facilitates a simple method for the construction of Simulink TM models 3, 7 . Other software that is used in the experimental process is Linux 2.1.18 (with specific program extensions), and Java applications 4 . The use of MATLAB/Simulink TM overshadows all other mechanisms for control system modeling, as it is seen to generate the code independently, removing the need for Real-Time Workshop and other such software tools that were needed to facilitate coding. Another point in favor of using MATLAB/Simulink TM is in the creation of an environment similar to an ideal real-time control platform. Linux and Java are cited as incapable of producing the best real-time platform because of “the non-determinism caused by the automatic memory management in Java 3 ”. While the speeds of most modern computers minimize this drawback, the Simulink TM model still offers the best real-time applications. A few other software tools that are utilized in laboratories today include RTLinux (Real-Time Linux) 2 and Simulinux-RT 5 . With regard to the types of controllers that have been utilized in the educational arena, there are a number of practical approaches being used for the illustration of the control systems concepts 812 . Regardless of the particular software being used or the specific type of controller being built, it is obvious that educational bodies worldwide have adjusted their structure to facilitate a greater exposure to the application of the abstract theory behind control systems to real-world, real-time processes. With the technology available to various laboratories and schools continuously P ge 14830.3 3 evolving, the students will soon be able to have all the required exposure and ability required to enter the work field with more than just a mere exposure to real-world applications of control theory. They will actually enter with a clear practical understanding. Underlying Educational Objectives Laboratory experiments using real-time systems are necessary in control education. Experiments help the students understand the theoretical concepts and provide important motivation. It is therefore essential for the students to have a thorough understanding of hands-on experimentation and real-time systems. Three fundamental educational objectives are: 1. To apply state-of-the-art knowledge to help students understand what they have learned. 2. To train a new cadre of graduates who value experimentation as an essential and natural part of solving engineering problems. 3. To develop good experimental skills. Hence, the controls engineering education becomes more attractive and meaningful to the students. To achieve these objectives and make it possible for the students to perform experiments, the lead author has developed six novel laboratory workstations using state-of-theart control systems technology. Student Learning Outcomes This paper describes a stimulating educational environment that emphasizes the role of hands-on experiments. The fundamental student learning outcomes of the control laboratory course are to demonstrate the following: 1) An ability to design, build, or assemble a part or product that configures control systems especially adapted to automation applications. 2) An ability to conduct experiments for measurements and analysis of feedback controls, and to write effective laboratory reports. 3) An ability to use MATLAB/ Simulink GUI to build a real-time model. 4) An ability to use dSPACE DSP ControlDesk GUI for real-time control. 5) An ability to achieve adequate learning skills in testing and debugging a prototype using appropriate engineering tools and learn how to be an experimenter. Hardware Selection Primarily, making a decision on a set of hardware to interface between the host computer and the process (system to be controlled