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A hybrid approach for Mechatronics instruction at the University of Tulsa
Mechatronics Vol. 5, No. 7, pp. 833-843, 1995 Elsevier Science Ltd Printed in Great Britain.
Pergamon 0957-4158 (95) 00050-X
A HYBRID A P P R O A C H FOR M E C H A T R O N I C S INSTRUCTION AT THE UNIVERSITY OF TULSA MARC T I M M E R M A N Mechanical Engineering Department, The University of Tulsa, 600 South College Avenue, Tulsa, OK 74104-3189, U.S.A.
Abstract--Mechatronics instruction has evolved into two paradigms: a high-level paradigm and a low-level paradigm. The high-level paradigm concentrates on PC-based (or other workstation-based) instruction using high-level programming languages like C, C++, PASCAL, or BASIC. The low-level paradigm concentrates on board-level microcontroller (typically the Motorola 68HCll or the Intel 8031)-based instruction and emphasizes the use of assembly or machine language. The various advantages and disadvantages of each paradigm are currently being explored by the Mechatronies education community. Both paradigms are illustrated by examples drawn from the current Mechatronics literature. Classes taught in the Mechanical Engineering program at The University of Tulsa have explored both paradigms. Different classes have been offered using high-level and low-level paradigms. Lessons are drawn from the practical experiences gleaned from these classes. A mixed-level paradigm class, currently under development, is described as a possible combination of the best qualities offered by the high-level and low-level paradigms.
1. I N T R O D U C T I O N AND R E V I E W OF LITERATURE Mechatronics instruction recently has manifested two major trends of curriculum development. Some programs have i m p l e m e n t e d a curriculum based on high-level languages such as C, C + + , B A S I C , F O R T R A N and P A S C A L . Such programs concentrate on PC-based (or other workstation-based) laboratory experiences and often emphasize simulations of devices rather than actual device construction. In contrast, other programs have evolved with a curriculum featuring an emphasis on low-level languages like assembly or machine language and experiments based on Intel, Motorola, or Phillips single-board microprocessor systems. These curricula emphasize real-time p r o g r a m m i n g and simple hands-on experiments with physical systems. This p a p e r explores the advantages and disadvantages of the high-level and low-level paradigms of teaching Mechatronics. Two classes have b e e n taught at The University of Tulsa, M E 4863 Special Topics in Mechatronics offered in Spring of 1993 as a low-level style class and in Spring of 1994 as a high-level style class. These classes target Mechanical Engineering students as the primary audience. Engineering Physics students have taken these classes as a technical elective. O t h e r engineering students (Electrical, Chemical, etc.) are generally unable to take t h e m due to curriculum restrictions. W o r k at The University of Tulsa is continuing (with funding from an N S F - I L I Grant) to develop a curriculum for a mixed-level class to be offered in the Spring of 1995. It is the goal of this new class to combine the best features of the high-level and low-level paradigms into a single hybrid class. 833
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Some recent highlights in the development of Mechatronics education include the following papers. • Bernardis [1, 2] and others have advanced general concepts of the Mechatronics design strategy. Keys [3], Derby [4] and many others have begun to apply the Mechatronics philosophy to the design of robotic and other systems. • Koves [5], Short et al. [6], Sobol [7] and others have discussed the need for cooperation between industry and academia in the planning of microprocessor classes. • Bray et al. [8], Durham [9], Fuhrt and Liu [10], George et al. [11], Herzog [12], Iyenegar and Kinney [13], Johnson [14] and others have stressed the need for a laboratory oriented style of instruction. • Kim and Alexander [15] and Ume and Timmerman [16-18] have stressed the need for an open-ended design project as an integral part of microprocessor classes. • A Mechatronics Education Workshop was held at Stanford University, Stanford, CA, on 21-22 July 1994. The proceedings of this workshop have extensively illustrated the growing trend of a high-level approach and a low-level approach to Mechatronics education [19-31]. The Stanford Workshop featured lively but cordial discussions of the high-level and low-level paradigms and the respective advantages and disadvantages of each paradigm. These discussions illuminated the key point that choice of a particular paradigm rests largely with the circumstances of the instructional environment such as prerequisites in the program, financial constraints, lab space available, if Mechatronics is a required or an elective part of the plan of study, accreditation requirements, and similar issues. Perhaps the challenge presented to instructors developing Mechatronics curricula is to select the best paradigm for the particular instructional situation in which he or she is developing his or her Mechatronics program.
2. LOW-LEVEL INSTRUCTION P A R A D I G M
Universities teaching Mechatronics using the low-level paradigm for instruction include Waikato University in New Zealand, Concordia University in Canada; in the U.S.A. such universities include Stanford University, the University of South Carolina, the Rose-Hulman Institute of Technology, and the Georgia Institute of Technology [21, 22, 25, 26, 28, 31]. The curriculum of instruction in low-level classes features an emphasis on assembly language or machine level code with students often being required to either hand-assemble or at least closely examine machine code. The principal advantages of this style of instruction include the following. • An exposure to registers, bin-hex arithmetic, memory concepts, and digital hardware that is otherwise lacking in the Mechanical Engineering curriculum. • The ability, often very desirable, to control the actions of Mechatronics systems at a minute level. This is often an advantage for Mechatronic engineers working in the automotive and industrial automation worlds where time control in milliseconds is essential for successful designs.
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• Relatively inexpensive laboratory equipment is needed. Self-contained one-board evaluation systems cost in the hundreds of dollars and are widely available. With the addition of a dumb-terminal (often a low-end PC), a power supply, and a few components, a wide variety of experiments can be performed. Software tools (typically an assembler and a communications package) are often available in the public domain or at very low cost. • Perhaps most importantly, students lose the "black box" conceptualization of computer systems in general and begin to grasp some of the underlying details and concepts of the inner working of computer systems. In the Spring of 1993 a class entitled ME 4863 Special Topics--Mechatronics was offered at The University of Tulsa using the low-level philosophy. The Motorola 68HCll EVB one-board microcomputer was used as the basis of this class along with low-level PC hosts (286s), inexpensive plug-in type power supplies, a free Motorola Assembler "AS11" and Kermit (a free terminal emulator). Additionally, the students were required to buy a kit consisting of a breadboard, pre-stripped wires, and components. Included readings were in general textbook literature and applications literature from Motorola [32-37]. No formal textbook was adopted for the class. Selected readings in Peatman's Design with Microcontrollers [33] and Motorola Data Books [35-37] were assigned. The class featured three lecture hours per week. Lecture topics included digital circuits, digital arithmetic, assembly and machine language, timing, I/O, interface electronics, and industrial applications. The emphasis of the material was on register-level programming and applications issues. An assembler was used, but students were required to hand assemble and hand disassemble code. Four experiments were conducted by the students. Each experiment consisted of two or three periods of three hours duration. The experiments were an RS 232 communications lab, a lab that implemented a counter that lighted LEDs in sequence, a strain-gage mounted on a cantilever beam lab that featured A/D conversion, and a lab on the speed control of a D.C. motor using pulse width modulation. More detailed descriptions of this low-level curriculum can be found in previous publications by Ume and Timmerman [16-18, 31]. The most serious complaint of the students in this class and perhaps the main impediment of the low-level approach is that students felt too burdened by the sheer number of details they had to master. It was often difficult for them to get a global view of the problems they needed to solve in the labs as hundreds of registers, syntax rules, arithmetic details, etc. had to be mastered and dealt with constantly. Additionally, the lack of background in electronics (only one Electrical Engineering class is required of Mechanical Engineering students in The University of Tulsa and this class teaches network theory rather than electronics) that is common to many Mechanical Engineering students meant that much basic electronics material had to be included in the class. This added even more to the burden of detail the students had to handle. Although the students praised the experience of being able to work with physical components and were able to appreciate the fine level of control inherent in the assembly language approach, the overall feeling was that the class was too detail heavy, contained more material than was appropriate for a single semester, and that it was difficult to see larger design issues with so many small details absorbing their attention.
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Universities teaching Mechatronics with the high-level paradigm include Colorado State University, the Rensselaer Polytechnic Institute, Iowa State University, and the Ohio State University, all in the United States [20, 23, 27, 29]. The high-level paradigm is similar to other engineering science classes in that it emphasizes formal theory presented in lectures and calculation-based problem solving. High-level languages like C + + , BASIC, or PASCAL are used. Often simulations are performed using mathematical models rather than physical experiments. Experimental tools are usually workstations with A/D and D/A boards driving external devices. Devices are usually pre-constructed for the student. Advantages of this approach include the following. • The student is freed from the drudgery of mastering the details of assembly or machine language and is able to concentrate on concepts rather than details. • The class can be better tailored to the pre-requisite taken by the students. Little or no circuit construction is needed and most of the experimental work consists of writing and debugging software or making observations. • The class is less intimidating to the student. Students are already familiar with workstations and high-level programming languages. The class applies familiar subjects (workstation, high-level language) to a new area of engineering (Mechatronics), rather than having both new subjects (assembly language, microprocessors) and a new area of engineering (Mechatronics). • The students do not need to master electronics in as great a detail as in the low-level approach. The high-level approach is thus well suited to institutions with little or no pre-requisite material in Electrical Engineering. • The use of workstations and pre-constructed experimental apparatus tends to prevent accidental damage of devices and is more robust from a lab equipment point of view. There are three main disadvantages to this high-level paradigm. • A greater financial burden as relatively high-end computers, software and apparatus are needed. • The students keep their "black box" view of computers and never get an idea of how they actually function on a component level. • The students generally do not learn much about assembly code and are unable to tackle problems that require extremely fine levels of control, especially timing. Even with these disadvantages, the high-level paradigm may be the only realistic solution for institutions that offer a single quarter-length Mechatronics class with little or no previous Electrical Engineering instruction. A high-level paradigm class was offered in the Spring of 1994 at The University of Tulsa, entitled ME 4863 Special Topics Mechatronics. A traditional textbook, lecture, homework, exam style course was offered with the three lecture hours per week and no additional lab. The textbook used was Ulsoy and DeVries' Microcomputer Applications in Manufacturing [38]. Program CC, a high-level simulation and calculation package used in classical controls, was used to simulate Mechatronics systems. (Program CC is a trademark of Systems Technology Inc., of Hawthorne, California,
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U.S.A.). No physical experiments were conducted, but extensive case studies were presented of industrial Mechatronics problems; CNC lathes, CNC mills, chemical process controls, and industrial ovens were simulated. The course content consisted of three sections: introduction to digital concepts, electronics, motors, sensors and actuators; assembly language and microcomputer architecture from an engineering science standpoint; and classical and state-space modeling and control of Mechatronics systems. (This information was covered in a survey format emphasizing general concepts rather than details.) No actual experiments were run nor was any real-time runable assembly language code written. Several extended homework problems were given involving simulations of systems on program CC. The class was generally well received and appreciated by students planning industrial careers. The students felt that they had experienced a good survey of the Mechatronics area and they would have an idea of the resources available to solve industrial Mechatronics problems. However, the main failing was that not enough detail was presented to allow the students to solve a Mechatronics problem without some additional independent study. The students did comment that the work load was reasonable (relative to the lab-oriented low-level class taught the year before) and that the traditional textbook/ lecture/homework/exam style of the class made it easy to understand. Perhaps the biggest advantage of the class was that the survey-style of the curriculum allowed the students to get a "big picture" feeling for Mechatronics design and avoided the tendency to get bogged down in too many details.
4. A MIXED PARADIGM
A mixed high-level and low-level paradigm for instruction has been implemented at the University of Delaware and Purdue University, both in the United States, and in various European universities, including Loughborough University of Technology, The University of Dundee, De Montfort University, Cranfield University, and Lancaster University, all in the United Kingdom; the Technical University of Denmark; the University of Twente in the Netherlands; the Swiss Federal Institute of Technology; the Catholic University of Leuven in Belgium; and the Johannes Kepler University of Linz, Austria [19, 24, 30]. Most of the European Universities have implemented degree programs in Mechatronics in which the high-level and low-level paradigms are taught in different classes or series of classes. In these institutions the material presented in these paradigms is spread out in various ways among several classes. In the U.S.A. institutions, the classes feature low-level single-board microcomputers and hands-on experiments, but the programming language used is a high-level language like C or C + + with a cross-compiler to generate assembly language. These classes use a hybrid curriculum with a low-level approach to hardware resources and a high-level approach to software resources. The principal advantages of this approach are as follows. • The ability to select the necessary level of assembly language and microprocessor architecture detail the students need to master. The students may be exposed to all the details of registers, timing, etc., or these details may be hidden in instructorwritten library functions called by the students in their own programs.
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• The ability to avoid much of the tedious detail involved in writing assembly code is very important. To add two numbers in assembly code involves numerous registers and a careful consideration of the hex arithmetic. These details can be easily handled by the C to assembler cross-compiler, thus freeing the student from this drudgery. • The students can be given more complex and challenging experimental problems. The use of instructor-written library functions frees the student from worrying about routine tasks and allows him or her to spend more time on the novel aspects of the experiment. This gives the students a greater sense of accomplishment and increases their interest. • Either pre-constructed or breadboard style experiments can be implemented depending on the curriculum goals. Pin-by-pin register-by-register details of the microprocessor can be hidden from the student as needed. The most important advantage is that the students have a chance to learn the details of the microcomputer architecture needed to work with problems requiring very fine control, while still being allowed to see the global aspect of Mechatronics problems. The level of detail the student has to deal with can be carefully tailored by the instructor to achieve this goal. The main disadvantages of this approach include the following. • The student must have or be given proficiency in a high-level language, usually some version of C. Real-time programming using C involves pointers and other fairly sophisticated programming techniques. Many Mechanical Engineering curricula still do not include C language instruction. • This approach is the most financially intensive as high-level workstations and board-level microcomputers are needed. Additionally, the software development tools needed (principally cross-compilers) tend to be extremely expensive and not user-friendly. Most of these software tools are intended for industrial rather than academic use. • Hiding much of the assembly language detail in library functions may give the student a false sense of confidence as he or she may be able to solve certain types of problems in the class environment that he or she may not be able to handle in a job environment where this type of pre-written library function may not be available. Lectures and laboratory activities for teaching a mixed-level Mechatronics class are currently being developed at The University of Tulsa to be offered in the Spring of 1995. These activities are being developed using an N S F - I L I grant plus University matching funds of a total of about US $57,000. Three experimental stations are under construction to accommodate a class of up to 12 students. This class will feature three hours of lecture and three hours of laboratory activity per week for a 14 week semester. For text material, an introductory level C textbook (with a real-time programming emphasis) will be used along with manufacturer's technical literature and extensive handouts. The lectures will consist of a formal introduction to real-time C programming, an introduction to assembly language from an Intel perspective, and brief applied discussions on basic circuits, introductory digital concepts, I/O tech-
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niques and standards, sensors and actuators, and related topics. Most of the later lectures will be background material for the lab activities rather than theoretical discussions. Grading will be based on three midterm tests, a final, and formal lab reports. The planned laboratory activities consist of seven experiments; three to introduce design components (an introduction to the C language lab, AiD and D/A conversion lab, RS 232 and IEEE 488 digital I/O lab) and four to apply them to actual problems (Programmable Logic Controller (PLC) lab, X - Y table lab, robot control lab, and a robotic Workcell lab). The laboratory activities will incorporate the Mechatronics design philosophy and build upon the concept of integrated, multi-disciplinary education. The laboratory activities begin with an introduction to the basic aspects of C programming from an unstructured FORTRAN-like approach emphasizing realtime programming. The difficult aspects of C involving elaborate data-structures will not be taught, but enough background of introductory C can be covered in a few weeks to allow students to call and use the C and assembly libraries of driver routines and communication routines supplied by makers of automation and instrumentation products and other routines pre-written by the instructor. Intel assembly language will also be explored using simple assemblers and with embedded assembly code within C programs. Not enough detail will be covered to allow the students to master assembly programming, but enough detail will be covered to allow the students to read, understand, and modify pre-written assembly language instrument drivers. The next laboratory activity explores the interface of the PC to the analog world by programming plug-in AiD and D/A converter boards. A Labwindows environment facilitates much of the repetitive tasks associated with this type of programming and has excellent debugging tools. Labwindows (a trademark of National Instruments Inc., of Austin, Texas, U.S.A.) is a high-level instrument interface programming environment with extensive C libraries. IEEE 488 and RS 232 communications standards will be explored. An activity using IEEE 488 and RS 232 controlled instruments will demonstrate these common communication protocols. Students will observe RS 232 and IEEE 488 signals on oscilloscopes. The students will also use a breadboard, logic gates, and LEDs to observe the signals. Many simple industrial automation tasks are solved through stand-alone controllers called PLCs or programmable logic controllers. A temperature controlled oven experiment is being designed using a PLC controller. The thermocouple sensor signal conditioner and heater actuator driving circuits will be breadboarded by the students. The PLC will be programmed by directly typing in machine code to the PLC or by sending control signals through an RS 232 line. Next, the RS 232 interface of an X - Y table will introduce the area of numerically controlled machining in a CNC lab. A robotics lab will use an ESHED Robot driven through an RS 232 interface to pick up an immobile object. The final lab activity uses the robot, the X - Y table and optical sensors constructed by the students on breadboards, to study integration of the sensors and actuators with control programs. The task will be to coordinate the X - Y table and robot to pick up a moving object. More detailed descriptions of the planned laboratories follow. (1) Introduction to C--covered in two weeks of lab. Basic programming and structures in the C language from a viewpoint of unstructured program. Simple Intel assembly language exercises are presented. Introductory material only is covered, no advanced data structure concepts are given.
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(2) AID and D/A--covered in two weeks of lab. Uses an oscilloscope and function generator to study AfD and D/A processes. Students will modify software drivers for standard plug-in PC type Aft) and D/A boards. This experiment will help students to have a better concept of digital and analog signals; the exchange of data between these two signal formats; and the role of sampling rate, resolution, and aliasing in the design of A/D processes. (3) Digital I/O--covered in two weeks of lab. Formatting and observation of RS 232 signals through software modification, oscilloscope observation, and LED and logic gate breadboarded circuits. Study of IEEE 488 signals through programming of test instruments. (4) PLC control through RS 232 interface--covered in two weeks of lab. The use of a computer interface to set a PLC controller through a ramp and soak cycle of an oven. The PLC controller is fitted with a thermocouple and a relay output to a heating unit. The goal of this activity is to have the temperature of the oven track a desired reference temperature signal. The students will breadboard the sensor and actuator interface circuits. (5) Mechanism control of an X - Y table--covered in two weeks of lab. Control of an X - Y table through RS 232 protocols to follow a desired path. This experiment introduces the concept of trajectory planning, point to point path motion, and the related concept of inverse kinematics as applied to numerically controlled motion. (6) Digital control of robot--covered in two weeks of lab. Motion control of an ESHED robot through RS 232 lines and C libraries. The assigned task is to pick up a stationary object. (7) Sensor and motion integration--covered in two weeks of lab. An object is placed on the X - Y table and placed in motion. The ESHED robot is used to pick up the object. Optical sensors mounted on the X - Y table are used to detect the position of the object. The optical sensor circuits will be breadboarded by the students. Independently, each activity has a particular focus and logic to its organization. As can be seen by the experiment inter-relationships in Fig. 1, the experiments build on each other to provide the students with a concurrent design approach to a hands-on solution of Mechatronics design problems. The students will have most of the necessary apparatus constructed for them except for some breadboarded signal conditioner and actuator driver circuits. The hands-on experience of working with electronic components seems to help the students loose their "black box" perception of electronic devices. It is hoped that this planned class will give the students the flavor of assembly code and an appreciation for registers, timing, hex arithmetic, digital logic, etc., while at the same time keeping the level of detail and drudgery to a minimum. The students should get enough experience with physical devices to attack real Mechatronics problems in job situations while at the same time not being unduly frustrated by the sheer mass and detail of the knowledge needed to fully master assembly language. Plug-in PC-based A/D, D/A, and IEEE 488 cards essentially stand in for the single-board microcomputers usually used in the low-level approach. The unfortunate, but very common, need to teach C in the class precludes the inclusion of extensive electronic and instrumentation material. This also predicates the expense of providing the relatively costly experimental devices (robot, X - Y table, PLCs) used in this class. Enough Intel assembly language will be covered to allow the students to read, understand, and modify existing code segments.
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Integration of knowledge Fig. i. Overviewof mixed-levelcurriculum. 5. CONCLUSIONS A trend has appeared recently in Mechatronics instruction with the manifestation of high-level and low-level approaches to teaching. The high-level approach features high-end workstations, high-level languages, typically C or C + + , and emphasizes a global view of Mechatronics design. The low-level approach stresses single-board microcomputers and the use of machine or assembly language. The choice of one approach or another is often dictated by pre-requisite constraints, time available and financial limits placed on the instructor. Ideally, a Mechatronics class should combine enough detail about assembly language and microprocessor architecture to allow the students to handle problems requiring fine levels of program control, but should also be sufficiently free of detail and drudgery to allow the students to get a "big picture"
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view of Mechatronics design. Several programs featuring a mixed-level approach to Mechatronics instruction have been and are being developed to try to reach this goal. Acknowledgenwnts--Fhis work has been funded by an NSF-ILI award, grant number DUE-9350865, plus matching funds from the University of Tulsa and an equipment grant from Motorola University Support. The author acknowledges with extreme gratitude the many contributions made by Professor Charles Ume of the George Woodruff School of Mechanical Engineering at the Georgia Institute of Technology to the Mechatronics classes described m this paper,
REFERENCES l. Bernardis L.. Mechatronics, building better models with fuzzy logic. Machine Des. 64(10), 72-75 (1992). 2. Bernardis L., Mechatronics, A nc~ ~design strategy. Machine Des. 62(8), 50-58 (199(I). 3. Keys L. K.. Mechatronics. Systems and elements. In Proceedings" of' the Ninth I E E E / C H M T International Electronic ManuJacturing Technology Symposium, pp. 329-333. Washington, D.C. (1990). 4. Derby S., Mechatronics for robots. Mech. Engng 112(7), 40-42 (1990). 5. Koves G., Industry-Government--University cooperation to establish CIM education the USA. Comput. htd. 14(3). 193 196 (1990). O. Short K. L., Sarpa E. J. and Shapiro S, D., An innovative program of university/industry cooperation microprocessor education. IEEE Trans. Education E-29. 11 l--114 (1986). 7. Sobol H.. Future directions engineering e d u c a t i o n - a view from industry and academia. IEEE Commun. Mag. 28(12), 25--29 (1990). 8, Bray D. W., Crist S. C. and Meyer R. A.~ A microcomputer laboratory and its courses. IEEE Trans. Education E-24, 149 154 (19811 9. Durham M. O., Microprocessor systems design, a course perspective. In Proceedings of" the Annual Pittsburgh Conference on Modeling and Simulation, 21 (3), 1075-1079 (1990). 10. Furht B. and Liu P. S., A [sic.] advanced laboratory for microprocessor interfacing and communication. IEEE Trans. Education 32(2), 124-128(i989). i1. George A. D. et al., Microprocessor course design at the F A M U / F S U college of Engineering. In Proceedings of the Annual Southwes'tern Symposium on Svsterns Theory, pp. 573-575 (1989). 12. Herzog J. H., Learning by doing, fifteen practical suggestions for implementing a successful microprocessor course for computer engineers. In Proceedings o f the Annual Pittsburgh Conference on Modeling and Simulation, 21(3), 969-973 (1990). 13. Iyenegar S. V. and Kinney I. L . A design oriented microprocessor laboratory. IEEE Trans. Education E-24.43-46 ( 1981 ), 14. Johnson J. J. (ed.), Special issue on microprocessors electrical engineering. IEEE Trans. Education E-24. Feb-May ( 1981 ). 15. Kim Y. and Alexander T., A new project oriented computer course digital electronics and computer design. IEEE Trans. Education E-29. August. 157-165 (1986). 16. Ume C., Timmerman M,. Graham G. and Ezcnekwc D,, Microprocessor design: an integrated multidisciplinary approach. Mechatronic~ 3 . 7 7 - 8 7 (1992), 17. Ume C. and Timmerman M . Microprocessor system design for controls oriented projects. ,L Microcompat. Applic. 15. 24I ~252 (1992). lg. Ume ('. and Timmerman M., Microprocessor design lor non-electrical engineers. IEEE Trans. Education 36(3), 327-333 (19q3). 19, Acar M., Undergraduate and postgraduate mcchatronics education in U.K. universities. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 1-6, Stanford, CA (1994). 2(1. Alciatore D. G. and Histand M. B.. Mechatronics and measurement systems course at Colorado State University. In Proceedings of the Stanford Workshop on Mechatronies Education, pp. 7-11, Stanford, CA (1994). 21, Carnegie D.. Budget Mechatronics. In Proceedinj,,s ~)1 the Stanford Workshop on Mechatronics Education, pp. 12 17, Stanford, CA (19q4). 22. Carryer J. E., The design of laboratory experimcnts and projects in Mechatronics. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 18-23, Stanford, CA (1994). 23. Craig K., Mechatronics system design at Rensselaer. In Proceedings o f the Stan/brd Workshop on Mechatronics Education, pp. 24-27, Stanford, CA (1994). 24. Harwin W. and Foulds R., Teaching Mechatronics at the University of Delaware. In Proceedings of the Staetbrd Workshop on Mechatronics Education, pp. 39-43, Stanford, CA (1994).
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25. Helm J. D. and McNeil S. R., Teaching microprocessors to mechanical engineers. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 44-50, Stanford, CA (1994). 26. Morin D. G., The design and implementation of a first course in microprocessor technology for mechanical engineers. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 68-71, Stanford, CA (1994). 27. Prabhu G. M. and Wright C. T. Jr, The use of microcontrollers in mechatronics education. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 72-77, Stanford, CA (1994). 28. Rajagopalan R. et al., Teaching mechatronics to mechanical engineering students at Concordia University. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 78-84, Stanford, CA (1994). 29. Rizzoni G. and Keyhani A., Design of mechatronics systems: an inter-departmental curriculum. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 85-90, Stanford, CA (1994). 30. Shoureshi R., Foundations for mechatronics education. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 103-106, Stanford, CA (1994). 31. Ume C. and Timmerman M., Mechatronics instruction in mechanical engineering curriculum at Georgia Tech. In Proceedings of the Stanford Workshop on Mechatronics Education, pp. 107-116, Stanford, CA (1994). 32. Staugaard A. C. Jr, 6801, 68701 and 6803 Microcomputer Programming and Interfacing. Sams, Indianapolis, IN (1980). 33. Peatman J. B., Design with Microcontrollers. McGraw-Hill, New York (1988). 34. Lipovski G. J., Single and Multiple-Chip Microprocessor Interfacing. Prentice-Hall, Englewood Cliffs, NJ (1988). 35. Motorola Inc., M68HCll EVB evaluation board user's manual (1986). 36. Motorola Inc., M68HCll HCMOS single-chip microcontroller programmer's reference manual (1986). 37. Motorola Inc., HCMOS single-chip microcontroller, technical data (1988). 38. Ulsoy A. G. and DeVries W. R., Microcomputer Applications in Manufacturing. John Wiley, New York (1989).
Pergamon 0957-4158 (95) 00050-X
A HYBRID A P P R O A C H FOR M E C H A T R O N I C S INSTRUCTION AT THE UNIVERSITY OF TULSA MARC T I M M E R M A N Mechanical Engineering Department, The University of Tulsa, 600 South College Avenue, Tulsa, OK 74104-3189, U.S.A.
Abstract--Mechatronics instruction has evolved into two paradigms: a high-level paradigm and a low-level paradigm. The high-level paradigm concentrates on PC-based (or other workstation-based) instruction using high-level programming languages like C, C++, PASCAL, or BASIC. The low-level paradigm concentrates on board-level microcontroller (typically the Motorola 68HCll or the Intel 8031)-based instruction and emphasizes the use of assembly or machine language. The various advantages and disadvantages of each paradigm are currently being explored by the Mechatronies education community. Both paradigms are illustrated by examples drawn from the current Mechatronics literature. Classes taught in the Mechanical Engineering program at The University of Tulsa have explored both paradigms. Different classes have been offered using high-level and low-level paradigms. Lessons are drawn from the practical experiences gleaned from these classes. A mixed-level paradigm class, currently under development, is described as a possible combination of the best qualities offered by the high-level and low-level paradigms.
1. I N T R O D U C T I O N AND R E V I E W OF LITERATURE Mechatronics instruction recently has manifested two major trends of curriculum development. Some programs have i m p l e m e n t e d a curriculum based on high-level languages such as C, C + + , B A S I C , F O R T R A N and P A S C A L . Such programs concentrate on PC-based (or other workstation-based) laboratory experiences and often emphasize simulations of devices rather than actual device construction. In contrast, other programs have evolved with a curriculum featuring an emphasis on low-level languages like assembly or machine language and experiments based on Intel, Motorola, or Phillips single-board microprocessor systems. These curricula emphasize real-time p r o g r a m m i n g and simple hands-on experiments with physical systems. This p a p e r explores the advantages and disadvantages of the high-level and low-level paradigms of teaching Mechatronics. Two classes have b e e n taught at The University of Tulsa, M E 4863 Special Topics in Mechatronics offered in Spring of 1993 as a low-level style class and in Spring of 1994 as a high-level style class. These classes target Mechanical Engineering students as the primary audience. Engineering Physics students have taken these classes as a technical elective. O t h e r engineering students (Electrical, Chemical, etc.) are generally unable to take t h e m due to curriculum restrictions. W o r k at The University of Tulsa is continuing (with funding from an N S F - I L I Grant) to develop a curriculum for a mixed-level class to be offered in the Spring of 1995. It is the goal of this new class to combine the best features of the high-level and low-level paradigms into a single hybrid class. 833
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Some recent highlights in the development of Mechatronics education include the following papers. • Bernardis [1, 2] and others have advanced general concepts of the Mechatronics design strategy. Keys [3], Derby [4] and many others have begun to apply the Mechatronics philosophy to the design of robotic and other systems. • Koves [5], Short et al. [6], Sobol [7] and others have discussed the need for cooperation between industry and academia in the planning of microprocessor classes. • Bray et al. [8], Durham [9], Fuhrt and Liu [10], George et al. [11], Herzog [12], Iyenegar and Kinney [13], Johnson [14] and others have stressed the need for a laboratory oriented style of instruction. • Kim and Alexander [15] and Ume and Timmerman [16-18] have stressed the need for an open-ended design project as an integral part of microprocessor classes. • A Mechatronics Education Workshop was held at Stanford University, Stanford, CA, on 21-22 July 1994. The proceedings of this workshop have extensively illustrated the growing trend of a high-level approach and a low-level approach to Mechatronics education [19-31]. The Stanford Workshop featured lively but cordial discussions of the high-level and low-level paradigms and the respective advantages and disadvantages of each paradigm. These discussions illuminated the key point that choice of a particular paradigm rests largely with the circumstances of the instructional environment such as prerequisites in the program, financial constraints, lab space available, if Mechatronics is a required or an elective part of the plan of study, accreditation requirements, and similar issues. Perhaps the challenge presented to instructors developing Mechatronics curricula is to select the best paradigm for the particular instructional situation in which he or she is developing his or her Mechatronics program.
2. LOW-LEVEL INSTRUCTION P A R A D I G M
Universities teaching Mechatronics using the low-level paradigm for instruction include Waikato University in New Zealand, Concordia University in Canada; in the U.S.A. such universities include Stanford University, the University of South Carolina, the Rose-Hulman Institute of Technology, and the Georgia Institute of Technology [21, 22, 25, 26, 28, 31]. The curriculum of instruction in low-level classes features an emphasis on assembly language or machine level code with students often being required to either hand-assemble or at least closely examine machine code. The principal advantages of this style of instruction include the following. • An exposure to registers, bin-hex arithmetic, memory concepts, and digital hardware that is otherwise lacking in the Mechanical Engineering curriculum. • The ability, often very desirable, to control the actions of Mechatronics systems at a minute level. This is often an advantage for Mechatronic engineers working in the automotive and industrial automation worlds where time control in milliseconds is essential for successful designs.
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• Relatively inexpensive laboratory equipment is needed. Self-contained one-board evaluation systems cost in the hundreds of dollars and are widely available. With the addition of a dumb-terminal (often a low-end PC), a power supply, and a few components, a wide variety of experiments can be performed. Software tools (typically an assembler and a communications package) are often available in the public domain or at very low cost. • Perhaps most importantly, students lose the "black box" conceptualization of computer systems in general and begin to grasp some of the underlying details and concepts of the inner working of computer systems. In the Spring of 1993 a class entitled ME 4863 Special Topics--Mechatronics was offered at The University of Tulsa using the low-level philosophy. The Motorola 68HCll EVB one-board microcomputer was used as the basis of this class along with low-level PC hosts (286s), inexpensive plug-in type power supplies, a free Motorola Assembler "AS11" and Kermit (a free terminal emulator). Additionally, the students were required to buy a kit consisting of a breadboard, pre-stripped wires, and components. Included readings were in general textbook literature and applications literature from Motorola [32-37]. No formal textbook was adopted for the class. Selected readings in Peatman's Design with Microcontrollers [33] and Motorola Data Books [35-37] were assigned. The class featured three lecture hours per week. Lecture topics included digital circuits, digital arithmetic, assembly and machine language, timing, I/O, interface electronics, and industrial applications. The emphasis of the material was on register-level programming and applications issues. An assembler was used, but students were required to hand assemble and hand disassemble code. Four experiments were conducted by the students. Each experiment consisted of two or three periods of three hours duration. The experiments were an RS 232 communications lab, a lab that implemented a counter that lighted LEDs in sequence, a strain-gage mounted on a cantilever beam lab that featured A/D conversion, and a lab on the speed control of a D.C. motor using pulse width modulation. More detailed descriptions of this low-level curriculum can be found in previous publications by Ume and Timmerman [16-18, 31]. The most serious complaint of the students in this class and perhaps the main impediment of the low-level approach is that students felt too burdened by the sheer number of details they had to master. It was often difficult for them to get a global view of the problems they needed to solve in the labs as hundreds of registers, syntax rules, arithmetic details, etc. had to be mastered and dealt with constantly. Additionally, the lack of background in electronics (only one Electrical Engineering class is required of Mechanical Engineering students in The University of Tulsa and this class teaches network theory rather than electronics) that is common to many Mechanical Engineering students meant that much basic electronics material had to be included in the class. This added even more to the burden of detail the students had to handle. Although the students praised the experience of being able to work with physical components and were able to appreciate the fine level of control inherent in the assembly language approach, the overall feeling was that the class was too detail heavy, contained more material than was appropriate for a single semester, and that it was difficult to see larger design issues with so many small details absorbing their attention.
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Universities teaching Mechatronics with the high-level paradigm include Colorado State University, the Rensselaer Polytechnic Institute, Iowa State University, and the Ohio State University, all in the United States [20, 23, 27, 29]. The high-level paradigm is similar to other engineering science classes in that it emphasizes formal theory presented in lectures and calculation-based problem solving. High-level languages like C + + , BASIC, or PASCAL are used. Often simulations are performed using mathematical models rather than physical experiments. Experimental tools are usually workstations with A/D and D/A boards driving external devices. Devices are usually pre-constructed for the student. Advantages of this approach include the following. • The student is freed from the drudgery of mastering the details of assembly or machine language and is able to concentrate on concepts rather than details. • The class can be better tailored to the pre-requisite taken by the students. Little or no circuit construction is needed and most of the experimental work consists of writing and debugging software or making observations. • The class is less intimidating to the student. Students are already familiar with workstations and high-level programming languages. The class applies familiar subjects (workstation, high-level language) to a new area of engineering (Mechatronics), rather than having both new subjects (assembly language, microprocessors) and a new area of engineering (Mechatronics). • The students do not need to master electronics in as great a detail as in the low-level approach. The high-level approach is thus well suited to institutions with little or no pre-requisite material in Electrical Engineering. • The use of workstations and pre-constructed experimental apparatus tends to prevent accidental damage of devices and is more robust from a lab equipment point of view. There are three main disadvantages to this high-level paradigm. • A greater financial burden as relatively high-end computers, software and apparatus are needed. • The students keep their "black box" view of computers and never get an idea of how they actually function on a component level. • The students generally do not learn much about assembly code and are unable to tackle problems that require extremely fine levels of control, especially timing. Even with these disadvantages, the high-level paradigm may be the only realistic solution for institutions that offer a single quarter-length Mechatronics class with little or no previous Electrical Engineering instruction. A high-level paradigm class was offered in the Spring of 1994 at The University of Tulsa, entitled ME 4863 Special Topics Mechatronics. A traditional textbook, lecture, homework, exam style course was offered with the three lecture hours per week and no additional lab. The textbook used was Ulsoy and DeVries' Microcomputer Applications in Manufacturing [38]. Program CC, a high-level simulation and calculation package used in classical controls, was used to simulate Mechatronics systems. (Program CC is a trademark of Systems Technology Inc., of Hawthorne, California,
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U.S.A.). No physical experiments were conducted, but extensive case studies were presented of industrial Mechatronics problems; CNC lathes, CNC mills, chemical process controls, and industrial ovens were simulated. The course content consisted of three sections: introduction to digital concepts, electronics, motors, sensors and actuators; assembly language and microcomputer architecture from an engineering science standpoint; and classical and state-space modeling and control of Mechatronics systems. (This information was covered in a survey format emphasizing general concepts rather than details.) No actual experiments were run nor was any real-time runable assembly language code written. Several extended homework problems were given involving simulations of systems on program CC. The class was generally well received and appreciated by students planning industrial careers. The students felt that they had experienced a good survey of the Mechatronics area and they would have an idea of the resources available to solve industrial Mechatronics problems. However, the main failing was that not enough detail was presented to allow the students to solve a Mechatronics problem without some additional independent study. The students did comment that the work load was reasonable (relative to the lab-oriented low-level class taught the year before) and that the traditional textbook/ lecture/homework/exam style of the class made it easy to understand. Perhaps the biggest advantage of the class was that the survey-style of the curriculum allowed the students to get a "big picture" feeling for Mechatronics design and avoided the tendency to get bogged down in too many details.
4. A MIXED PARADIGM
A mixed high-level and low-level paradigm for instruction has been implemented at the University of Delaware and Purdue University, both in the United States, and in various European universities, including Loughborough University of Technology, The University of Dundee, De Montfort University, Cranfield University, and Lancaster University, all in the United Kingdom; the Technical University of Denmark; the University of Twente in the Netherlands; the Swiss Federal Institute of Technology; the Catholic University of Leuven in Belgium; and the Johannes Kepler University of Linz, Austria [19, 24, 30]. Most of the European Universities have implemented degree programs in Mechatronics in which the high-level and low-level paradigms are taught in different classes or series of classes. In these institutions the material presented in these paradigms is spread out in various ways among several classes. In the U.S.A. institutions, the classes feature low-level single-board microcomputers and hands-on experiments, but the programming language used is a high-level language like C or C + + with a cross-compiler to generate assembly language. These classes use a hybrid curriculum with a low-level approach to hardware resources and a high-level approach to software resources. The principal advantages of this approach are as follows. • The ability to select the necessary level of assembly language and microprocessor architecture detail the students need to master. The students may be exposed to all the details of registers, timing, etc., or these details may be hidden in instructorwritten library functions called by the students in their own programs.
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• The ability to avoid much of the tedious detail involved in writing assembly code is very important. To add two numbers in assembly code involves numerous registers and a careful consideration of the hex arithmetic. These details can be easily handled by the C to assembler cross-compiler, thus freeing the student from this drudgery. • The students can be given more complex and challenging experimental problems. The use of instructor-written library functions frees the student from worrying about routine tasks and allows him or her to spend more time on the novel aspects of the experiment. This gives the students a greater sense of accomplishment and increases their interest. • Either pre-constructed or breadboard style experiments can be implemented depending on the curriculum goals. Pin-by-pin register-by-register details of the microprocessor can be hidden from the student as needed. The most important advantage is that the students have a chance to learn the details of the microcomputer architecture needed to work with problems requiring very fine control, while still being allowed to see the global aspect of Mechatronics problems. The level of detail the student has to deal with can be carefully tailored by the instructor to achieve this goal. The main disadvantages of this approach include the following. • The student must have or be given proficiency in a high-level language, usually some version of C. Real-time programming using C involves pointers and other fairly sophisticated programming techniques. Many Mechanical Engineering curricula still do not include C language instruction. • This approach is the most financially intensive as high-level workstations and board-level microcomputers are needed. Additionally, the software development tools needed (principally cross-compilers) tend to be extremely expensive and not user-friendly. Most of these software tools are intended for industrial rather than academic use. • Hiding much of the assembly language detail in library functions may give the student a false sense of confidence as he or she may be able to solve certain types of problems in the class environment that he or she may not be able to handle in a job environment where this type of pre-written library function may not be available. Lectures and laboratory activities for teaching a mixed-level Mechatronics class are currently being developed at The University of Tulsa to be offered in the Spring of 1995. These activities are being developed using an N S F - I L I grant plus University matching funds of a total of about US $57,000. Three experimental stations are under construction to accommodate a class of up to 12 students. This class will feature three hours of lecture and three hours of laboratory activity per week for a 14 week semester. For text material, an introductory level C textbook (with a real-time programming emphasis) will be used along with manufacturer's technical literature and extensive handouts. The lectures will consist of a formal introduction to real-time C programming, an introduction to assembly language from an Intel perspective, and brief applied discussions on basic circuits, introductory digital concepts, I/O tech-
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niques and standards, sensors and actuators, and related topics. Most of the later lectures will be background material for the lab activities rather than theoretical discussions. Grading will be based on three midterm tests, a final, and formal lab reports. The planned laboratory activities consist of seven experiments; three to introduce design components (an introduction to the C language lab, AiD and D/A conversion lab, RS 232 and IEEE 488 digital I/O lab) and four to apply them to actual problems (Programmable Logic Controller (PLC) lab, X - Y table lab, robot control lab, and a robotic Workcell lab). The laboratory activities will incorporate the Mechatronics design philosophy and build upon the concept of integrated, multi-disciplinary education. The laboratory activities begin with an introduction to the basic aspects of C programming from an unstructured FORTRAN-like approach emphasizing realtime programming. The difficult aspects of C involving elaborate data-structures will not be taught, but enough background of introductory C can be covered in a few weeks to allow students to call and use the C and assembly libraries of driver routines and communication routines supplied by makers of automation and instrumentation products and other routines pre-written by the instructor. Intel assembly language will also be explored using simple assemblers and with embedded assembly code within C programs. Not enough detail will be covered to allow the students to master assembly programming, but enough detail will be covered to allow the students to read, understand, and modify pre-written assembly language instrument drivers. The next laboratory activity explores the interface of the PC to the analog world by programming plug-in AiD and D/A converter boards. A Labwindows environment facilitates much of the repetitive tasks associated with this type of programming and has excellent debugging tools. Labwindows (a trademark of National Instruments Inc., of Austin, Texas, U.S.A.) is a high-level instrument interface programming environment with extensive C libraries. IEEE 488 and RS 232 communications standards will be explored. An activity using IEEE 488 and RS 232 controlled instruments will demonstrate these common communication protocols. Students will observe RS 232 and IEEE 488 signals on oscilloscopes. The students will also use a breadboard, logic gates, and LEDs to observe the signals. Many simple industrial automation tasks are solved through stand-alone controllers called PLCs or programmable logic controllers. A temperature controlled oven experiment is being designed using a PLC controller. The thermocouple sensor signal conditioner and heater actuator driving circuits will be breadboarded by the students. The PLC will be programmed by directly typing in machine code to the PLC or by sending control signals through an RS 232 line. Next, the RS 232 interface of an X - Y table will introduce the area of numerically controlled machining in a CNC lab. A robotics lab will use an ESHED Robot driven through an RS 232 interface to pick up an immobile object. The final lab activity uses the robot, the X - Y table and optical sensors constructed by the students on breadboards, to study integration of the sensors and actuators with control programs. The task will be to coordinate the X - Y table and robot to pick up a moving object. More detailed descriptions of the planned laboratories follow. (1) Introduction to C--covered in two weeks of lab. Basic programming and structures in the C language from a viewpoint of unstructured program. Simple Intel assembly language exercises are presented. Introductory material only is covered, no advanced data structure concepts are given.
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(2) AID and D/A--covered in two weeks of lab. Uses an oscilloscope and function generator to study AfD and D/A processes. Students will modify software drivers for standard plug-in PC type Aft) and D/A boards. This experiment will help students to have a better concept of digital and analog signals; the exchange of data between these two signal formats; and the role of sampling rate, resolution, and aliasing in the design of A/D processes. (3) Digital I/O--covered in two weeks of lab. Formatting and observation of RS 232 signals through software modification, oscilloscope observation, and LED and logic gate breadboarded circuits. Study of IEEE 488 signals through programming of test instruments. (4) PLC control through RS 232 interface--covered in two weeks of lab. The use of a computer interface to set a PLC controller through a ramp and soak cycle of an oven. The PLC controller is fitted with a thermocouple and a relay output to a heating unit. The goal of this activity is to have the temperature of the oven track a desired reference temperature signal. The students will breadboard the sensor and actuator interface circuits. (5) Mechanism control of an X - Y table--covered in two weeks of lab. Control of an X - Y table through RS 232 protocols to follow a desired path. This experiment introduces the concept of trajectory planning, point to point path motion, and the related concept of inverse kinematics as applied to numerically controlled motion. (6) Digital control of robot--covered in two weeks of lab. Motion control of an ESHED robot through RS 232 lines and C libraries. The assigned task is to pick up a stationary object. (7) Sensor and motion integration--covered in two weeks of lab. An object is placed on the X - Y table and placed in motion. The ESHED robot is used to pick up the object. Optical sensors mounted on the X - Y table are used to detect the position of the object. The optical sensor circuits will be breadboarded by the students. Independently, each activity has a particular focus and logic to its organization. As can be seen by the experiment inter-relationships in Fig. 1, the experiments build on each other to provide the students with a concurrent design approach to a hands-on solution of Mechatronics design problems. The students will have most of the necessary apparatus constructed for them except for some breadboarded signal conditioner and actuator driver circuits. The hands-on experience of working with electronic components seems to help the students loose their "black box" perception of electronic devices. It is hoped that this planned class will give the students the flavor of assembly code and an appreciation for registers, timing, hex arithmetic, digital logic, etc., while at the same time keeping the level of detail and drudgery to a minimum. The students should get enough experience with physical devices to attack real Mechatronics problems in job situations while at the same time not being unduly frustrated by the sheer mass and detail of the knowledge needed to fully master assembly language. Plug-in PC-based A/D, D/A, and IEEE 488 cards essentially stand in for the single-board microcomputers usually used in the low-level approach. The unfortunate, but very common, need to teach C in the class precludes the inclusion of extensive electronic and instrumentation material. This also predicates the expense of providing the relatively costly experimental devices (robot, X - Y table, PLCs) used in this class. Enough Intel assembly language will be covered to allow the students to read, understand, and modify existing code segments.
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C Programming Computer Basics
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Integration of knowledge Fig. i. Overviewof mixed-levelcurriculum. 5. CONCLUSIONS A trend has appeared recently in Mechatronics instruction with the manifestation of high-level and low-level approaches to teaching. The high-level approach features high-end workstations, high-level languages, typically C or C + + , and emphasizes a global view of Mechatronics design. The low-level approach stresses single-board microcomputers and the use of machine or assembly language. The choice of one approach or another is often dictated by pre-requisite constraints, time available and financial limits placed on the instructor. Ideally, a Mechatronics class should combine enough detail about assembly language and microprocessor architecture to allow the students to handle problems requiring fine levels of program control, but should also be sufficiently free of detail and drudgery to allow the students to get a "big picture"
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view of Mechatronics design. Several programs featuring a mixed-level approach to Mechatronics instruction have been and are being developed to try to reach this goal. Acknowledgenwnts--Fhis work has been funded by an NSF-ILI award, grant number DUE-9350865, plus matching funds from the University of Tulsa and an equipment grant from Motorola University Support. The author acknowledges with extreme gratitude the many contributions made by Professor Charles Ume of the George Woodruff School of Mechanical Engineering at the Georgia Institute of Technology to the Mechatronics classes described m this paper,
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