PC s and Micro-Controllers in Mechatronics Education Santosh Devasia and Sanford Meek Department of Mechanical Engineering The University of Utah Salt Lake City, Utah 84112 Abstract The mechanical engineering department at the University of Utah is developing a certificate program in mechatronics, which includes a three-quarter mechatronics sequence. This mechatronics sequence is required for all mechanical engineering students -- this paper describes the mechatronics curriculum and discusses the extent to which students will use PCs and microcontrollers. The extend to which microcontroller are included in the curriculum is of particular significance to a mechanical engineering curriculum which may need an introduction to them but do not, however, require the low-level-language programming based teaching of microcontrollers. Introduction Goals of Mechatronics Education The course in Mechatronics is in response to the demand for engineers who are proficient in multiple disciplines and not constrained by the traditional definition of a mechanical engineer (Hang and Lee, 1990). From our standpoint as a mechanical engineering department, this means teaching students about the options available in the electronic and information systems domain so that they might be better informed in selecting the most appropriate solution in terms of cost, performance, and reliability for a given task. Our aim is to demonstrate the combination of the three elements of mechanical, electrical, and information systems to yield well-designed systems. Thus, although the new mechatronics sequence retains the content of previous courses in system modeling and basic control courses, it will now emphasize an integrated laboratory with extensive use of automated data acquisition and control implementation, allowing students to design intelligent mechatronic systems (Nelson et. al., 1995). Development of a New Mechatronics Course At the University of Utah's Mechanical Engineering Department, as at other schools, the concepts of mechatronics such as: actuators, sensors, measurement systems, controller design etc. were scattered in several courses. The department had three courses in the area of mechatronics, Modeling of Physical Systems (ME280), Introduction to Controls (ME320), and Design of Machine elements (ME382). There was also a lack of continuity between these classes and a lack of a unified education in electro-mechanical design. Also, the students did not have a required course addressing instrumentation and automated data collection. Recently the department integrated these several courses into a unified three-quarter sequence
where the students will be able to obtain an integrated design experience in the mechatronics area (Nelson et. al., 1995). This required sequence in mechatronics (ME318, ME319, ME320) fits into the junior year of the standard undergraduate program; at a point where students will have acquired, or will be taking concurrently, the necessary background in such topics as mechanics of materials, electronics, thermodynamics, fluid dynamics, and programming to comprehend the variety of devices they will encounter. The course also precedes senior elective courses, such as State- Space Controls and Digital Signal Processing, where the concepts of mechatronics will be applied in advanced designs and project construction. New Mechatronics Certificate Program In addition to the development of the new year long course on mechatronics, the department is also in the process of creating an interdisciplinary certificate program in mechatronics. Thus Mechatronics education is being offered at two levels in the Department of Mechanical Engineering at the University of Utah. First the concepts are being introduced in the junior year to all mechanical engineering undergraduates in a required course sequence. Second, the certificate program offers electives for senior undergraduates. A holistic approach of modeling, instrumentation, actuators, control, and computers is the pedagogical philosophy in both levels of courses. It will emphasize the need for a harmonious integration of computational tools, electronic hardware, and electro-mechanical systems to successfully apply modern control theories to practical engineering systems. Combined with integrated hands-on laboratories this experience will include: basic electronics (EE108 and EE109); model development, simulation and verification in (Mechatronics ME318), design of mechanisms and choice of proper actuators and sensors (Mechatronics ME319), design and analysis of controllers (Mechatronics ME320), control system implementation (ME320 and Digital and Analog Interfaces EE566). Further, electives will also be offered in robotics (CS 531 and CS 532), and advanced control theory and implementation (ME/EE520, ME/EE521, ME/EE522, EE566). This integrated approach (Levine et. al., 1993) will provide: instruction in applied electronics; unified analytical and experimental methods in modeling, analysis and simulation of dynamical systems; and both - analog and digital - control system design, analysis and implementation. Laboratory Development The mechanical and electrical engineering departments at the University of Utah are collaborating to integrate laboratories into the courses under the mechatronics option. This goal -- integrated experimental work with the controls courses -- is also consistent with the overall emphasis to have practical design experience integrated into the entire undergraduate curriculum. The experiments we develop will introduce industrial applications and real-life control design/analysis issues like handling of nonlinearity, multiloop design and trajectory tracking (Hang and Lee, 1990). These experiments will aid the students to assimilate some of the more abstract concepts covered in the controls courses. Further, they will also develop an appreciation for the potentials of control as well as its limitations in practical applications. PCs and Micro-Controllers The question is - what is the most suitable way to teach students, in the mechatronics laboratories, about automated data acquisition and control implementation? There has been two main approaches: (1) PC based experimentation; and (2) Micro-controller based experimentation. Many schools interpret Mechatronics to be more oriented toward lower level (Levine et. al.,
1993) micro-controller programming and application (for example, Meckl and Shoureshi, 1993). Other schools concentrate on a more higher level PC-based teaching the subject (see for example, Astrom, 1991, and other references in Thompson et. al., 1995). The advantages and disadvantages of both approaches are explored next. Later, we present our attempt to balance the emphasis between the two approaches -- we use PC-based and higherlevel language based microcontrollers. We will, however, offer advanced microprocessor courses as electives (EE563/CS563 and EE564/CS564). This approach, we believe, is suited for students in a mechanical engineering department, where we do not wish to require all students to have an in-depth exposure to intensive micro-controller programming. PCs Availability of PCs that are reasonably priced along with powerful software for data collection and analysis like LABVIEW, and design tools like MATLAB have substantially affected the used of PCs in undergraduate laboratories (Schaufelberger, 1990). Therefore PCs play a significant role in the development of mechatronics laboratories, in particular, these tools facilitate hands-on experimentation with sensors and actuators, and in control of electromechanical systems. In some control laboratories most experiments have been based completely on PCs (see for example, Astrom 1991). The major advantages of a PC based experiments are the flexibility, user friendliness, use of higher level programming, ability to store larger programs, and the availability of pre-existing software. This availability of software allows the student to perform on-line simulations and compare, to develop controllers, and for postprocessing of data (Thompson et. al., 1995). On the negative side, PCs tend to be bulky, and have been difficult to use in individual projects. In a recent final project to build and control automated basket ball shooting robots, tethers to the computer were needed causing inconvenience and interference with the wires. Although it can be argued that PCs do not provide the real-life experience of working with microcontrollers, we find that there is no substitute for the PC s flexibility -- at least in the beginning stages where the student is being introduced to the rudiments of data acquisition, sensors and actuators. This flexibility along with the user friendliness of the typical software enables the students to explore what-if type experimentation making it a valuable tool to provide hands-on experience to the students. Micro-Controllers Micro-Controllers are becoming essential in industrial products (as opposed to PCs) since they provide functionality at lower costs. They are portable and cheaper, and most importantly provide real-life experience to the students. They are, however, several problems, when microcontrollers are used in the laboratory setting. Since most mechatronic systems have been the typical forte of electrical engineering and computer science students, the intensive programming required by micro-controllers hasn t been a problem. This intense emphasis on microcontrollers and programming has been typically emphasized in most mechatronics education. We believe that the emphasis on programming tends to distract from conveying the main analysis and design concepts -- especially from a mechanical engineering curriculums perspective. Thus, we prefer to use the recently available Handy-Boards that allow PC-based higher-level programming of the micro-controller. Note that the micro-controller programming is C based- which we also used for data acquisition and control using the PC -- thus the students only need to know one programming language. This common use of C in PC and micro-controller was the motivation to use the C-programming approach for LABVIEW rather than graphical-programming.
They are, however, several other problems, when micro-controllers are used in the laboratory setting. Presently available microcontrollers have low memory, have low resolutions, are programming intensive, and are not user-friendly. Another problem is speed. Even with PCs, typical sampling and control times are around 1000 Hz -- in fact, experiments have to be specially designed to run with these low sampling (and control) rates. The problem is compounded with the use of slow microcontrollers. Some of these problems will be (and have been) mitigated over time with advances in micro-controllers, for example, the advent of 16 Bit micro-controllers, and the ability to program in C with a PC with automated conversion before down-loading. However, the limiting factors are the lack of pre-existing software for data-analysis and the memory limitations that prevent larger programs. Thus most microcontrollers in the teaching environment will require a host PC for post-processing of data. Our Approach It has been the extensive use of micro-controllers that has lead to the explosion of mechatronics systems and hence the need to teach it. Definitely students the students will get a better appreciation of higher-level programming, and real-life experience working with microcontrollers. The question before us is not whether or not micro-controller are to be used in teaching mechatronics to mechanical engineering students - rather is to what extent should the students be exposed, to micro-controllers, in required course sequences. While the emphasis of many mechatronics curriculum have focused in on low-level programming of microcontrollers, we believe that it tends to distract the students from the main concepts being introduced. Further, the lack of flexibility hinders self-experimentation by the student. The need for PC in control education is well appreciated -- even in schools which have extensive use of micro-controllers in laboratories (Meckl and Shoureshi, 1993), senior control systems laboratories still exploit the advantages provided by PCs (Lyon et. al., 1994). Our approach is to use both, PCs and microcontrollers. We use PC s in the first two quarters as the students are becoming familiar with data acquisition, actuators and controller, in conjunction with high level software like LABVIEW. In the final quarter of the three quarter mechatronics sequence we introduce microcontrollers that can be used in the final projects. We, however, choose Handy-boards that allow higher-level programming in C on a PC which is then down-loaded into the microcontroller. Thus the students have an exposure to micro-controller based projects, but we do not require all students to take these low-level programming intensive classes but rather offer them to the interested students as electives, in particular, the Digital and Analog Interfaces EE566 which is offered through the electrical engineering department. Conclusion Use of micro-controllers and PCs are both necessary to facilitate mechatronics education. As a mechanical engineering department we have provided a balance between the understanding of design concepts and the knowledge of real-life implementation of data acquisition and control in mechatronics. This was done by (1) providing flexibility and user friendliness of the PCs in beginning classes in mechatronics and later using the microcontrollers; (2) Using high-level language based micro-controller implementation; and (3) maintaining a continuity in the programming language - C is used in both PC and microcontroller based data acquisition and control. This allowed mechatronics concepts to
be conveyed easily in the required mechatronics course sequence; advanced concepts are then taught in specialized micro-controller courses, which are offered as electives. Curriculum, Proceedings of the ACC, pp. 34-38, 1995. Bibliography Astrom, K.J., Education in Automatic Control at Lund Institute of Technology, Proceedings of the ACC, pp. 306-311, 1991. Hang, C.C., and Lee T.H., Incorporating Practical Contents in Control Engineering Courses, IEEE Transactions on Education, Vol. 33, No. 3, pp. 279-284, August 1990. Levine, W.S., Leonard, N.E., and Dayawasana, W.P., An Integrated Undergraduate Controls Experience, Proceedings of the ACC, pp. 1236-1239, 1993. Lyon, D.E., Meckl, P.H., and Nwokah, O.D.I., Senior Control Systems Laboratory at Purdue University, IEEE Transactions on Education, Vol. 37, No. 1, pp. 71-76, February 1990. Meckl, P.H., and Shoureshi, R., Laboratory Project in Semi-Active Vibration Control, Proceedings of the ACC, pp. 1240-1243, 1993. Nelson, D., Yampanis, M., Devasia, S., and Meek, S., "Mechatronics Education at the University of Utah," Design Engineering Session 11, ASME International Mechanical Engineering Congress and Exposition, November 1995. Schaufelberger, W., Design and Implementation of Software for Control Education, IEEE Transactions on Education, Vol. 33, No. 3, pp. 291-297, August 1990. Thompson, J.G., Gorder, P.J., and White, W.N., Integration of Flexible Embedded Control System Design into the Mechanical Engineering