Darrell L. Vines, Dept. of Electrical Engineering
Box 43102, Texas Tech University, Lubbock, TX 79409-3102
(806) 742-1262, (806) 742-1245(Fax), dvines@coe2.coe.ttu.edu
James R. Rowland, Dept. of Electrical Engineering and Computer Science
1013 Learned Hall, The University of Kansas, Lawrence, KS 66045
(913) 864-8822 (913) 864-4971(Fax), jrowland@eecs.ukans.edu
The need for feedback in controlling electromechanical systems has been demonstrated for many applications [1-4]. As an example, pump jacks in the oil field are driven by large electric motors which are assumed to run at constant speeds. The designers may have thought that motors would be able to maintain constant speeds regardless of the mechanical loads placed on the motors. When very large motors were selected, the speeds did not vary excessively. Due to cost-cutting procedures, engineers used smaller motors which changes the speed so dramatically that a portion of the time the mechanical system runs the motor as a generator and the other time the motor is severely loaded. Such a control system may well be described as an ``open loop'' control system. Better ways to control systems with feedback control are currently being used.
Other familiar examples using feedback control are automobile speed-control and home temperature control. ``Cruise control'' allows the driver of a car to set the desired speed and the car automatically maintains this speed. As the car encounters a hill, the cruise control will cause more fuel to be delivered to the engine so that the speed is reduced only slightly. The designer has selected appropriate transducers to measure the air, fuel, temperature, speed, or vacuum to assure that the controller ``knows'' the state of the car when the cruise control is activated. Additionally, actuators are selected to adjust the flow of appropriate fluids and gases to assure that the vehicle maintains the desired speed. Another example is the use of temperature controllers within homes to maintain a comfortable air temperature the year round. The temperature is sensed by a device whose output is interpreted appropriately to cause the heater or the air conditioner to operate. Designers are careful to adjust the threshold of the actuators so that they cause the minimum of cycling of the heater or air conditioner.
In brief, if the electromechanical system can be accurately described and appropriate sensors and actuators selected, then the principles of feedback control should be immediately preferable to open-loop control that does not account for changes in the environment. It would be helpful, then, to describe the teaching process in terms of feedback control so that educators can more effectively cause the learners to achieve at the most appropriate level. The resulting feedback model should be of help to a beginning instructor who has never taught before or to a research professor needing to improve teaching skills.
Let us consider the concepts described in Figure 1, in which relationships between the professor, student, and related resources are illustrated. In this case the professor may well be described as the controller or provider of energy. The student and professor have access to a syllabus or list of course objectives by which they will be guided to determine if the goals have been achieved by the class as a whole, the individual student, and the professor. In an ``open-loop'' control system, the professor might very well lecture and expect the student to listen, do the homework, read from resources, develop computer solutions, and learn the material. At the end of the course, the student would be passed, provided the student met the course objectives. In such a circumstance, the student is not evaluated until the end of the course of study. There is no feedback to the student (system) until the student arrives at the destination, which may or may not be the correct one.
An improvement on the educational system described above is illustrated in Figure 2, in which examinations are provided periodically through the course of study to provide feedback to the professor and the student. Assuming that the faculty member strives to inspire the student to master portions of the syllabus or course objectives, the exams may measure portions of each. Of course, the professor need not measure every detail of the student's achievement to estimate the progress. The student should be given instructions in the form of feedback that indicates how well the student is achieving. In particular, while the class average may be 40%, the student should be told whether the performance will lead to a passing grade at the end of the session. In other words, the student should not have to ``guess or hope'' that the performance is leading to adequate achievement.
Grading exams can be utilized two ways by the faculty member and student. The professor may decide that the lectures or assignments have not been causing the student to utilize the resources appropriately to learn the material. On the other hand, the professor may just use the grade to determine whether the student will pass and, therefore, not modify communications with the student, i.e., not give the system adequate feedback to guide the system to success.
Clearly, the obvious items of the syllabus, course objectives, texts, laboratories, and prepared faculty member are assumed to be in place. The student is also assumed to have mastered the previous material so that learning can be accomplished. What is missing from the model in Figure 2 are other kinds of feedback, including especially the benefits due to office visits between the student and the professor.
Figure 3 illustrates the Instructional Feedback Model that utilizes additional sensors for achievement in the form of timely graded homework assignments to help the student know the relative progress in developing the skills. Additionally, project assignments with other students allows the students to learn from each other and to begin learning how to teach each other[5]. Feedback to the students in this case allows them to sense their progress compared to their colleagues, and it also provides practice in solidifying their understanding of aspects found on the syllabus. Certainly, the opportunity for the students to meet a faculty member in an office for intense review, counsel, encouragement, or motivation will be additional incentive for the student to use as many of the resources as may be available to achieve at the highest level.
What about the actuators? In the feedback systems described in the introduction, the actuators played a significant role in the control system, and none have yet been identified. How will they be modeled? The actuators will likely be built into the system in terms of the student's self-motivation and desire to be successful. It is assumed that students will not subject themselves to such grueling tasks as are encountered in an engineering course unless they are convinced that they want to become engineers. There may well be reason for debate at this point, because some teachers may recognize that additional remedial work is necessary and that additional homework problems can be assigned to enable the student to retrace and better learn the material. Therefore, an ``actuator'' provides correction to the system. No such device was included in the block diagrams in Figures 1 and 2.
Consider the following sensors:
Most faculty and students readily acknowledge that all the items seem appropriate with the possible exception of the office visits. Assume initially that the office visits are not an imposition on either the faculty or the student. What are the real benefits? One might recognize that a student's environment may well change during the course of study. In many cases, a student experiences changes in family situations that are beyond the student's control. In other cases, the family situation may change dramatically and still be within the student's control. Work situations may present problems that temporarily or permanently alter the student's environment. Many times the student may have trouble being convinced that the course of study is appropriate. What does a student do in such a case? Vines [6] indicated that a faculty member who is trusted and respected by the student may be able to function as a Mentor for the student. The faculty member (Mentor) will have had sufficient contact with the student in class, in an office, in the hall, at IEEE meetings, and other such places for interpersonal contact, and the student feels comfortable to express a vulnerability to conditions. The result is a rich opportunity for teaching. A mentor may well believe that the students have within themselves the solution to their environmental problems. Listening to the problem and proposed solution, the faculty member may be able to evaluate the problem-solving process and reflect back to the student the observation.
Students in two senior classes were asked to respond briefly in writing about their experiences with professors outside of the classroom. The first class was asked if their professors are generally available and responsive to their needs. Of 23 students, 20 said professors are available, though complained that professors are sometimes difficult to locate except during office hours and then asked for more office hours. Only 2 students cited cases where professors were not responsive, and many pointed to extra help beyond what they had expected. The second class was asked if they had received help from professors on career decisions or personal situations. Of 22 responses, 18 students cited one or more times when professors had advised them on technical areas of interest, specific companies, or graduate studies. Only a very few mentioned personal situations.
The following samples of interactions with students occurred during the Spring 1995. These examples are presented to illustrate the kinds of interactions that can and do occur for faculty members who are perceived as being open to students.
The Instructional Feedback Model clearly shows what has been obvious to most students and faculty members all along. In fact, many of the current faculty members were subjected to such a feedback system while they were students. The changes in the professors' environment have caused some faculty to change and to stop utilizing the feedback principles that work. Focusing on research and publications in a highly charged ``publish-or-perish'' environment, some professors limit their time and efforts with students as a precious commodity. Such professors appear to have the following views:
The costs both to the professor and to the student are the additional time and effort required for interaction. These visits may only be occasional, but the motivation and support received from an interested professor can be personally significant to a student needing someone who cares, especially at the right moment.
The Instructional Feedback Model is presented to promote not only many kinds of feedback to students in classroom situations but also to urge the student and professor to establish a personal rapport for motivation, encouragement, and support. A pre-mentoring relationship is recommended in which the student begins to know the professor as a person and as a valuable resource now and for the future. It is recommended that the professor take positive steps in the classroom to encourage such interactions, e.g., open discussions, showing a caring attitude, or even posing intriguing/puzzling questions requiring further information or references from the professor outside the classroom. Whatever the stimulus needed to spark these outside visits should be a planned part of the course presentation.
