【正文】 方法可觀測并計(jì)算得到系統(tǒng)的臨界例增益K、和臨界振蕩周期T，應(yīng)用這兩個(gè)參數(shù)變量設(shè)計(jì)了基于給定的幅值度和相角裕度的PID控制器。 （7）中斷控制系統(tǒng)。（1）、5V、12V 的固定電壓輸出和可調(diào)電壓輸出 （2）可調(diào)輸出電壓范圍 ～37V177。該驅(qū)動(dòng)方式的優(yōu)點(diǎn)是驅(qū)動(dòng)電機(jī)的力矩紋波很小，可應(yīng)用于對電機(jī)轉(zhuǎn)速要求非常高的場合；缺點(diǎn)是該方式通常比較復(fù)雜，成本較高，尤其是要提高驅(qū)動(dòng)的功率時(shí)相應(yīng)的電路成本將提升很多。在很多電路中除非作一個(gè)升壓電路否則是比較困難得到的。原理圖如圖411 所示。編碼器的接口電路如圖414所示。 主控程序:主控程序負(fù)責(zé)控制整個(gè)系統(tǒng)的工作流程，判斷按鍵值、控制數(shù)碼管顯示，以及控制電機(jī)轉(zhuǎn)動(dòng)等。PWM模塊的初始化設(shè)置過程為：PWME=0X00。PWMPER45=20000。 圖56 利用4KHZ時(shí)基實(shí)現(xiàn)電機(jī)測速 在直流電機(jī)調(diào)速系統(tǒng)中，數(shù)字PID是一種比較成熟的算法。其程序流程圖為圖57所示:圖57 PID計(jì)算流程主程序在系統(tǒng)初始化（初始化時(shí)鐘、中斷、變量等）之后，顯示默認(rèn)的電機(jī)轉(zhuǎn)速設(shè)定值，并等待按鍵輸入。電機(jī)啟動(dòng)子程序控制電機(jī)按照設(shè)定的方式轉(zhuǎn)動(dòng)。 本設(shè)計(jì)在硬采用了基于PWM技術(shù)的驅(qū)動(dòng)電路，解決了電機(jī)驅(qū)動(dòng)的效率問題，在軟件上也采用較為合理的系統(tǒng)結(jié)構(gòu)和算法，提高了單片機(jī)的使用效率，并且具有一定的防飛能力。 A temperature regulator must maintain the temperature of say, an oven constant despite the heat loss in the oven. A voltage regulator must also maintain must output voltage constant despite variation in the load current. For any system to provide an output, ., speed, temperature, voltage, etc, an error signal must exist under steadystate conditions.electrical brakingIn many speed control system, ., rolling mills mine winders, etc., the load has to be frequently brought to a standstill and reversed. The rate at which the speed reduces following a reduced speed demand is dcpdent on the stored crgy and the braking system used. A small speed control system (sometimes known as a velodyne) can employ mechanical braking, but this is not feasible with large speed controllers since it is difficult and costly to remove the heat generated.The various methods of electrical braking avaiable are:(I)Regenerative braking.(2) Eddy current braking(3) Dynamic braking.(4) Reverse current braking(plugging).Regenerative braking is the best method, though not necessarily the most economic. The stored energy in the load is converted into electrical energy by the work motor(acting temporarily，a gcrator) and is returned to the power supply system, The supply system thus acts as a sink into which the unwanted energy is delivered. Providing the supply system has adequate capacity, the consequent rise in terminal voltage will be small during the short periods of regeneration. In the WardLeonard method of speed control of DC motors, regenerative braking is inherent, but thyristor drives have to be arranged to invert to regenerate. Induction motor driver can regcrate if the rotar shaft is driven faster than speed of the field. The advent of lowcost variable variablefrequency supplies from rotating Thyristor inverters have brought about considerable charges in the use of induction motors in variable speed drives. Eddy current braking can be applied to any machine, simply by mounting a copper or aluminium disc on the shaft and rotating it in a magnetic field. The problem of removing the heat generated is severe in large system as the temperature of the shaft, bearing, and motor will be raised if prolonged braking is applied.In dynamic breaking, the stored energy is a resistor in the circuit. When applied to small DC machines, the armature supply is disconnected and a resistor is connected across the armature (usually by a relay, contactor, or thyristor). The field voltage is maintained, and braking is applied down to the lowest speed. Induction motors require a somewhat more plex arrangement, the stator windings being disconnected from the AC supply and reconnected to a DC supply. The electrical energy generated isthen dissipated in the rotor circuit. bynamic braking is applied to many large AC hoist system where the braking duty is Goth severe and prolonged.Any electrical motor can be brought to a standstill by suddenly reconnecting the supply to rcvcssc the direction of rotation (reverse current braking). Applied under controlled conditions, this method of braking is satisfactory for ail drivers. lts major disadvantabe is that the electrical energy consumed by the machine when braking is equal to tho stored orgy in the load. This increases the running cost significantly in large drives.Equal pulse width PWM law VVVF (Variable Voltage Variable Frequency) installs in the early time is uses PAM (Pulse Amplitude Modulation) to control, its inventor part which the technology realizes but only can output the frequency adjustable squarewave voltag。 s Guide .1987.[17]Astrom K J, Hang C C, Persson and Ho W K,Towards Intelligent PID Control. Automation, 1992, 28 (1):19[18]Ho WK, Lim and Xu Wen, Optimal gain and phase margin tuning for PID controllers Automation, 1998,vo1，34,No,8:10091011[19]M Zhuang, ，Automatic tuning of optimum PID controllers[J]， IEE proceedings Control and Application, 140:216224[20]D. F. Geiger Phaselocks Loops for DC Motor Speed Control[M].John Wileyamp。達(dá)到了要求系統(tǒng)具有下列功能：1：通過三個(gè)按鍵設(shè)定電機(jī)的轉(zhuǎn)速，并顯示設(shè)定值；2：可實(shí)時(shí)測量電機(jī)的實(shí)際轉(zhuǎn)速，并在LED數(shù)碼管上顯示出來；3：可對電機(jī)進(jìn)行以繼電反饋的PID自整定轉(zhuǎn)速調(diào)節(jié)，當(dāng)電機(jī)參數(shù)發(fā)生變化時(shí)，繼電反饋工作，測得需要用到的PID值，使其轉(zhuǎn)速趨近于設(shè)定值。圖58 主程序流程圖在轉(zhuǎn)速設(shè)定子程序中，數(shù)碼管閃爍顯示當(dāng)前設(shè)定轉(zhuǎn)速，并通過Keyl和Key2鍵對轉(zhuǎn)速進(jìn)行增減設(shè)置。、和可通過實(shí)際測試調(diào)整獲得，經(jīng)實(shí)測，當(dāng)=1/2, =3/16, =1/16時(shí)，轉(zhuǎn)速波動(dòng)幅度可控制在士1轉(zhuǎn)/秒以內(nèi)。以4KHz為采樣頻率，檢測該I/0端口的電平狀態(tài)并計(jì)數(shù)，即可通過一段時(shí)間內(nèi)的計(jì)數(shù)值計(jì)算出電機(jī)轉(zhuǎn)速。 所有PWM為左對齊PWMCTL=OXFO。通過配置寄存器可設(shè)置PWM的使能與否、每個(gè)通道的工作脈沖極性、每個(gè)通道輸出的對齊方式、時(shí)鐘源以及使用方式(八個(gè)8位通道還是四個(gè)16位通道)。繼電反饋：通過單片機(jī)輸出一個(gè)開關(guān)量，系統(tǒng)產(chǎn)生等幅振蕩，獲取臨界狀態(tài)，單片機(jī)判斷反饋的值和輸出值進(jìn)行比較計(jì)算出PID的值，打開PID控制器開關(guān)時(shí)，由計(jì)算出的PID值由系統(tǒng)進(jìn)行動(dòng)態(tài)調(diào)節(jié)。由于MOS管柵極導(dǎo)通需要14V的導(dǎo)通電壓，所以需要一個(gè)升壓模塊： 圖412 升壓電路下面是MOS管電機(jī)驅(qū)動(dòng)的實(shí)物圖： 圖413 MOS管驅(qū)動(dòng)實(shí)物圖測量電機(jī)轉(zhuǎn)速需要用到光電編碼器，我選用歐姆龍200線編碼器，編碼器（encoder）是將信號(hào)（如比特流）或數(shù)據(jù)進(jìn)行編制、轉(zhuǎn)換為可用以通訊、傳輸和存儲(chǔ)的信號(hào)形式的設(shè)備。下面是我之前和別人一起做的7960PCB板以及實(shí)物圖： 圖48 7960PCB圖 圖49 7960電路圖 圖410 7960實(shí)物圖采用4個(gè)LR7843,該驅(qū)動(dòng)內(nèi)阻小，開關(guān)速度快，驅(qū)動(dòng)電流大。因此S4 電壓應(yīng)該高于Q4 的源極電壓，S1 電壓應(yīng)該高于Q1 的源極電壓。 圖46 按鍵電路目前直流電機(jī)的驅(qū)動(dòng)方式主要有2種形式：線性驅(qū)動(dòng)方式和開關(guān)驅(qū)動(dòng)方式。如圖44所示。 （5）四個(gè)8位可編程的并行I/O端口，每個(gè)端口既可作輸入，也可作輸出。設(shè)Q點(diǎn)坐標(biāo)為Q（,），再結(jié)合式（313），得到， （314）當(dāng)圖34中的開關(guān)。 基于繼電反饋控制的PID參數(shù)整定基于Astrom法的繼電整定：利用繼電振蕩的結(jié)果可以辨識(shí)出開環(huán)對象的Nyquist曲線上的臨界點(diǎn)，被控對象在PID控制下的開環(huán)傳遞函數(shù)可表示為： （35）開環(huán)頻率特性為： （36）由式(35)可以看出，Nyquist曲線上任意一個(gè)給定點(diǎn)可通過改變控制器的比例增益、積分時(shí)間、微分時(shí)間，從而被移動(dòng)到S半平面內(nèi)的任意位置處。利用臨界信息設(shè)計(jì)控制器，還有很多學(xué)者結(jié)合建模理論，根據(jù)臨界信息建立完善的系統(tǒng)模型，然后在此模型基礎(chǔ)上設(shè)計(jì)最