【正文】 [ 2 ]摩托羅拉公司，鳳凰城，亞利桑那，溫度測量和使用它的顯示mc68hc05b4和mc14489，1990。印刷電路板一個簡單的（雖然布局絕對不平凡）印刷電路板是這個工程提供的另一個現(xiàn)實學習的機會。部分問題是各種外圍設備（例如，應該使用哪種顯示驅(qū)動程序？）連接方法的選擇。圖7Simulink仿真閉環(huán)系統(tǒng)框圖顯示了Simulink情況下的閉環(huán)系統(tǒng)框圖，其中包括A/D轉換和使用標準Simulink量化飽和塊建立的飽和量化模型。因此，開環(huán)系可以寫成：(下標p1已經(jīng)被去掉了)過初始溫度和熱量值大范圍內(nèi)的設置，簡單的開環(huán)階躍響應實驗結果表明，K≈，τ≈295S。集總元件熱系統(tǒng)符合線性控制，適用于載玻片干燥機的問題。其中一個重要的功能是進行模式切換。1176。第二個氣筒（電子圍繞元件）設有一個電阻加熱器、一個溫度控制器以及一個安裝在干燥機上的風扇，是為了把風吹過加熱器，把熱量帶到載玻片氣室。tracking step changes in setpoint temperature with acceptable rise time, steadystate error, and overshoot.Although not explicitly a part of the specifications in Table 1, it was clear that the customer desired digital displays of setpoint and actual temperatures, and that setpoint temperature entry should be digital as well (as opposed to, say, through a potentiometer setting).3 System DesignThe requirements for digital temperature displays and setpoint entry alone are enough to dictate that a microcontrollerbased design is likely the most appropriate. Figure 2 shows a block diagram of the students’ design. The microcontroller, a MotorolaMC68HC705B16 (6805 for short), is the heart of the system. It accepts inputs from a simple fourkey keypad which allow specification of the setpoint temperature, and it displays both setpoint and measured chamber temperatures using twodigit sevensegment LED displays controlled by a display driver. All these inputs and outputs are acmodated by parallel ports on the 6805. Chamber temperature is sensed using a precalibrated thermistor and input via one of the 6805’s analogtodigital inputs. Finally, a pulsewidth modulation (PWM) output on the 6805 is used to drive a relay which switches line power to the resistive heater off and on.Figure 3 shows a more detailed schematic of the electronics and their interfacing to the 6805. The keypad, a Storm 3K041103, has four keys which are interfaced to pins PA0{ PA3 of Port A, configured as inputs. One key functions as a mode switch. Two modes are supported: set mode and run mode. In set mode two of the other keys are used to specify the setpoint temperature: one increments it and one decrements. The fourth key is unused at present. The LED displays are driven by a Harris Semiconductor ICM7212 display driver interfaced to pins PB0{PB6 of Port B, configured as outputs. The temperaturesensing thermistor drives, through a voltage divider, pin AN0 (one of eight analog inputs). Finally, pin PLMA (one of two PWM outputs) drives the heater relay.Software on the 6805 implements the temperature control algorithm, maintains the temperature displays, and alters the setpoint in response to keypad inputs. Because it is not plete at this writing, software will not be discussed in detail in this paper. The control algorithm in particular has not been determined, but it is likely to be a simple proportional controller and certainly not more plex than a PID. Some control design issues will be discussed in Section 4, however.4 The Design ProcessAlthough essentially the project is just to build a thermostat, it presents many nice pedagogical opportunities. The knowledge and experience base of a senior engineering undergraduate are just enough to bring him or her to the brink of a solution to various aspects of the problem. Yet, in each case, realworld considerations plicate the situation significantly.Fortunately these plications are not insurmountable, and the result is a very beneficial design experience. The remainder of this section looks at a few aspects of the problem which present the type of learning opportunity just described. Section discusses some of the features of a simplified mathematical model of the thermal properties of the system and how it can be easily validated experimentally. Section describes how realistic control algorithm designs can be arrived at using introductory concepts in control design. Section points out some important deficiencies of such a simplified modeling/control design process and how they can be overe through simulation. Finally, Section gives an overview of some of the microcontrollerrelated design issues which arise and learning opportunities offered. MathematicalModelLumpedelement thermal systems are described in almost any introductory linear control systems text, and just this sort of model is applicable to the slide dryer problem. Figure 4 shows a secondorder lumpedelement thermal model of the slide dryer. The state variables are the temperatures Ta of the air in the box and Tb of the box itself. The inputs to the system are the power output q(t) of the heater and the ambient temperature T165。本組學生開發(fā)設計是基于摩托羅拉MC68HC05系列單片機。溫度時通常保持在一個穩(wěn)定的常數(shù)，但重要的是階躍變化可以被“合理”的跟蹤。圖22 溫度控制器硬件結構圖摩托羅拉MC68HC705B16（簡稱6805），是系統(tǒng)的核心。4 設計過程雖然該項目的本質(zhì)是建立一個恒溫器，但它有許多很好的契機可以供教學借鑒