HIGH SCHOOL SCI-TECH PROJECT - AN INSIGHT INTO ENGINEERING I. Verner, S. Waks and E. Kolberg Technion - Israel Institute of Technology E-mail:
[email protected] Abstract There is general acceptance that an advanced Technology curriculum is needed at the high school level in order to attract students to Technology studies, and in order to promote an insight into the engineering profession. This paper deals with a pilot two-year course “An Introduction to Robotics and Real Time Control”, and describes its framework, curriculum and learning strategy. The course has been given since 1994 in three Israeli high schools and is now officially recommended for wider implementation. Results of a student questionnaire concerning their attitudes towards the course and towards technology as a knowledge and occupational area are presented and discussed.
Introduction Technological education in high school is undergoing a reform in relation to its status, goals and teaching/learning strategies. Rapid development of integrated sciencetechnology curricula is supported by national educational programs such as Project 2061 and the Israeli program, Tomorrow 98. Interdisciplinary approaches are expected to become a part of new educational standards [1,2]. Meanwhile, most general high school interdisciplinary curricula are dominated by science. The embodied technological fragments are used to illustrate “real world” applications of science methods. Technology educators believe that these curricula should be complemented by systematic technology studies that are accessible to any interested student [3,4]. In contrast to the vocational education approach, such a technology course should eliminate the confined professional bias and provide an insight into engineering science. It should be optional and focused both on stimulating technological perception and practical thinking as well as increasing motivation to major in this profession. Therefore new approaches are needed to design the appropriate curricula and teaching/learning strategies [5]. One of the possible approaches to designing and implementing an advanced technology course in a general high school is proposed and discussed in this paper.
The pilot optional course “An Introduction to Robotics and Real Time Control” presents a two-year program, which includes: theoretical studies, lab experiments and construction work as well as a practical mini-project and a theoretical mini-research. The program started in 1994 at the Ohel-Shem general high-school. Blich school has joined since 1995, and an additional school that is associated with the Hebrew University joined in 1996. By the 1996-97 school year a total of 122 students (grades 1012) has participated in the program: 17 students in 1994-96, 43 in 1995-97 and 62 students enrolled in 1996. The program is currently recommended by the Israeli Ministry of Education for wider implementation. Teacher training courses for the program have been conducted since 1996. The course grade is based on an oral presentation and a portfolio. The grade is included in the advanced disciplines section of the student matriculation certificate under the title “Machine control”. It provides the graduates with a considerable bonus when applying for engineering university studies. In this paper the course curriculum and it’s implementation will be discussed in relation to the following questions: 1. To what extent may an optional technology course be attractive for general high school students? 2. What objectives should be central for the course curriculum? 3. What teaching methods are most relevant? 4. What changes in student’s perceptions and behavior may be stimulated by the course? It should be mentioned, that the principles of designing an interdisciplinary robotics curricula for general high schools, which were implemented in the course, were assessed in our former research on training spatial ability through manipulating robot movements [6,7].
Course plan The course includes basic studies of electronics, computers, mechanics, control and design in the robot system context. In the creative part of the course (a practical mini project and a theoretical mini research) the
students are involved in constructing hardware components and developing software modules for the robot system for the practical mini project. They also investigate a technology problem that is central for the theoretical mini research. The optional course curriculum for “An Introduction to Robotics and Real-Time Control” is given in Table 1. The main subjects taught and their sub-topics which appear in Table 1 are detailed below. Electronics studies include definitions of voltage, current and resistance, Ohm’s and Kirchhoff’s laws, DC
circuits and components: capacitors, inductors and their applications, diodes, bipolar junction transistor amplifying and switch modes, multiplexers, decoders, flip-flops, data sheet reading, H-bridge circuit, PWM, PFM. Computers studies are focused on the basics of binary logic and Boolean algebra, logic gates, Karnaugh maps[8], computer structure and its functioning, address bus, data bus and control bus, RS-232 serial communication [9].
Table 1: Course curriculum Learning Contents and Activities Electronics Fundamental concepts and electronic circuits Components and integrated circuits Digital electronics Motor control circuits Computers Logic and Boolean algebra Computer components Serial communication, address, data and control buses Assembly language and robot programming Microprocessor structure and addressing modes Assembly language instructions and commands, interpreter, “high language” application Input/output, interrupts and communication implementation by software Robot control Mechanics Materials, forces and torque Motors and gears Control Control types Motor control Robot movement closed loop control Robotics Robot design considerations Integrating hardware and software for emergency situations escape Sensor’s types Laboratory Electronic P.C.B. construction Designing and building a robot Final tests, troubleshooting, debugging and fixing Creative projects Practical mini project Theoretical mini research
Learning hours 4 6 15 5 6 14 5 5 16 9 10 5 10 7 5 8 9 6 5 12 23 5 40 80
The Assembly language subject includes computer components interface and addressing modes, application of commands and instructions for implementing I/O, interrupts, communication functions and for robot monitoring [9,10]. The Mechanics chapter deals with materials, forces and torques, robot frame and motor shaft loading, DC servo and stepping motors. The Control section relates to open and closed loop modes, DC motor and stepping motor position and speed control, robot motion and collision avoidance [10,11]. The Robotics study is focused on factors influencing robot design such as weight, stability, loads, collisions recovery, functionality. In addition to general factors, specific requirements are considered for providing applications of basic robot configuration that are necessary for implementing different tasks. These factors are motor selection and reevaluation of loads, emergency situation escape and sensor feedback configuration. Laboratory workshops include PCB construction, building the designed robot system, testing, troubleshooting and fixing. Creative projects provide students with the challenge of self-supporting theoretical and practical activities. Team tasks given for the practical mini project relate to adapting and extending the robot for executing various assignments in an automated mode. These assignments may be vacuum cleaning, dynamic video monitoring, transporting and manipulating objects. The purpose of the individual theoretical mini research-work is to investigate some specific problems arising in technology that are not necessarily associated with the mini project. Two examples for such activities are a sensor-based method for
avoiding robot collisions, recognition for robot control.
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Learning strategy Our learning strategy is compatible with the framework of an optional course, in which students meet technology for the first time; therefore it is based on: streamlining learning through pragmatic activities; concentrating on studies of modern technology basics, operating technological systems and design activities; attracting students towards technological issues through diverse theoretical, hands-on and creative team-tasks; providing the students with opportunities to apply and evaluate knowledge and methods acquired in mathematics and science. Special attention is paid to an introductory talk with potentially interested students, which is aimed at presenting the proposed technology course in an attractive way. On this occasion the rational, curriculum and benefits of the course are specified, together with displaying practical learning activities and demonstrating robot systems developed by former students. Our threeyear experience and students’ feedback indicate the importance and influence of this educational strategy. The course time schedule, selected in the form of once-a-week 4-hours workshops, provides a suitable setting in which we turn students’ attention to learning technology. Parallel study of several different subjects in each workshop, instead of a single disciplinary subject-bysubject approach, provides the students with diverse learning activities options, performing design and construction tasks. A time-table, typical for the first year workshops, is given in Table 2.
Table 2: A typical time-table for a weekly meeting Hour 1st 2nd 3rd 4th
Learning subject Electronics and Mechanics hardware Computers and control Assembly language (experimenting using development system) Robot construction
The second year studies are concentrated on performing creative tasks. The practical mini project and theoretical mini research are carried out in parallel. Combined, they provide the students with relatively broad experience in the technology area. The main features of our approach to learning through the projects is summarized in Table 3.
Example As an example, we will consider the issue of DC-motor speed control. As part of the studies, the students learn to produce a process of 4-stepped speed control for a set-up of DC motors. The scheme of H-bridge DC motor direction control is given in Fig. 1a. The method of direct potentiometer-based voltage control that is familiar to the students from the physics course,
does not provide an appropriate solution. The idea is to use the pulse width modulation (PWM) method for speed control. This method enables voltage control by means of pulses supplied to terminal A for modulation purposes (see Fig.1). Modulation is carried out by means of changing the duty cycle. While learning the subject, the students become familiar with the principles of wave superposition. At the next stage, they acquire the preliminary experience of applying the PWM method through practice with the microprocessor control instructional module. PWM and other methods of microprocessor control, are learned in three stages:
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theoretical studies; experience with the microprocessor control instructional module (MCIM); - practice in robot motion control. MCIM is an instructional package including hardware and software components that we developed in order to simulate the process of peripheral device control. It is connected to a computer through a RS-232 serial communication port for program downloading and debugging, and the peripherals are connected to the module parallel ports.
Table 3: Creative projects goals and activities Features Didactic goals The assignment
Learning activities:
Practical Mini Project Practical problem solving Adapting the robot for automatic task execution
Theoretical Mini Research Qualitative reasoning and research practice (inf. id. & analysis) Investigation of a problem arising in technology
x Defining the outcome
x Problem definition
x Work planning
x Bibliographic search
x Constructing the robot set-up
x Subject matter studies & functional analysis
x Functional operating the outcome
x Findings interpretation
Fig. 1: H-bridge DC motor rotation-direction control
************************************************** * 68HC11 PWM routine * * Signal frequency is 100 Hz, three speeds. * * Duty cycles: slow - 80%, medium - 90%, fast -100%. * * AccB contains desired speed: $00 for slow, * * $01 for medium and $02 for fast. IY contains * * no. of pulses. TOC1 holds period time and * * TOC2 holds Ton time. IX
