【正文】 MotorolaSemiconductor Application Note AN1239.[5] Motorola, Inc., Phoenix, AZ, RAPID Integrated DevelopmentEnvironment User’s Manual, 1993. (RAPID wasdeveloped by P amp。tp2 _ 0 are good approximations. Thus the openloop system is essentially firstorder and can therefore be written (where the subscript p1 has been dropped).Simple openloop step response experiments show that,for a wide range of initial temperatures and heat inputs, K _0:14 _=W and t _ 295 Control System DesignUsing the firstorder model of (4) for the openloop transfer function Gaq(s) and assuming for the moment that linear control of the heater power output q(t) is possible, the block diagram of Figure 6 represents the closedloop system. Td(s) is the desired, or setpoint, temperature,C(s) is the pensator transfer function, and Q(s) is the heater output in watts.Given this simple situation, introductory linear control design tools such as the root locus method can be used to arrive at a C(s) which meets the step response requirements on rise time, steadystate error, and overshoot specified in Table 1. The upshot, of course, is that a proportional controller with sufficient gain can meet all specifications. Overshoot is impossible, and increasing gains decreases both steadystate error and rise time.Unfortunately, sufficient gain to meet the specifications may require larger heat outputs than the heater is capable of producing. This was indeed the case for this system, and the result is that the rise time specification cannot be met. It is quite revealing to the student how useful such an oversimplified model, carefully arrived at, can be in determining overall performance limitations. Simulation ModelGross performance and its limitations can be determined using the simplified model of Figure 6, but there are a number of other aspects of the closedloop system whose effects on performance are not so simply modeled. Chief among these are. ma and mb are the masses of the air and the box, respectively, and Ca and Cb their specific heats. μ1 and μ2 are heat transfer coefficients from the air to the box and from the box to the external world, respectively.It’s not hard to show that the (linearized) state equationscorresponding to Figure 4 areTaking Laplace transforms of (1) and (2) and solving for Ta(s), which is the output of interest, gives the following openloop model of the thermal system:where K is a constant and D(s) is a secondorder , tz, and the coefficients of D(s) are functions of the variousparameters appearing in (1) and (2).Of course the various parameters in (1) and (2) are pletely unknown, but it’s not hard to show that, regardless of their values, D(s) has two real zeros. Therefore the main transfer function of interest (which is the one from Q(s), since we’ll assume constant ambient temperature) can be writtenMoreover, it’s not too hard to show that 1=tp1 1=tz 1=tp2, ., that the zero lies between the two poles. Both of these are excellent exercises for the student, and the result is the openloop polezero diagram of Figure 5.Obtaining a plete thermal model, then, is reduced to identifying the constant K and the three unknown time constants in (3). Four unknown parameters is quite a few, but simple experiments show that 1=tp1 _ 1=tz。displaying both setpoint and actual temperatures, andTemperature Control Using a Microcontroller:An Interdisciplinary Undergraduate Engineering Design ProjectJames S. McDonaldDepartment of Engineering ScienceTrinity UniversitySan Antonio, TX 78212AbstractThis paper describes an interdisciplinary design project which was done under the author’s supervision by a group of four senior students in the Department of Engineering Science at Trinity University. The objective of the project was to develop a temperature control system for an airfilled chamber. The system was to allow entry of a desired chamber temperature in a prescribed range and to exhibit overshoot and steadystate temperature error of less than 1 degree Kelvin in the actual chamber temperature step response. The details of the design developed by this group of students, based on a Motorola MC68HC05 family microcontroller, are described. The pedagogical value of the problem is also discussed through a description of some of the key steps in the design process. It is shown that the solution requires broad knowledge drawn from several engineering disciplines including electrical, mechanical, and control systems engineering.1 IntroductionThe design project which is the subject of this paper originated from a realworld application. A prototype of a microscope slide dryer had been developed around an OmegaTM model CN390 temperature controller, and the objective was to