【正文】 樣信號(hào)通過LM358與一固定電壓值比較，當(dāng)電壓的電流過大時(shí)，LM358輸出高電平，送入GAL16V8直接關(guān)斷輸出，進(jìn)行邏輯保護(hù)。電流采樣方式可采取直接采樣兩相電流的方法或采樣直流母線電流的方法。采樣直流母線電流有兩種方法，一種是在待測(cè)電路上串入一個(gè)小電阻，用小電阻上的壓降反映電流的大小；另一種是采用電流傳感器。考慮到本控制系統(tǒng)的成本問題，本系統(tǒng)采用第一種電流采樣方式。過流保護(hù)是控制器的最后防線，過流保護(hù)電阻用的是康銅絲，當(dāng)系統(tǒng)電流超過最大保護(hù)電流值時(shí)，康銅絲會(huì)燒斷，從而起到保護(hù)作用。它的使用范圍包括傳感放大器、直流增益模塊和其他所有可用單電源供電的使用運(yùn)算放大器的場(chǎng)合。當(dāng)電池電壓過低時(shí)給出欠壓信號(hào)，輸出截止，防止電池由于過放而損壞。 電源電路圖317 電源電路圖如圖317所示，36V電池送入U(xiǎn)1U1U15穩(wěn)壓器輸出+15V和+5V給PIC單片機(jī)和IR2110供電。隨后采樣位置傳感器產(chǎn)生霍爾信號(hào), 將該信號(hào)的狀態(tài)與電機(jī)固定的相位序列進(jìn)行比較, 判斷電機(jī)的相位是否正確。欠壓檢測(cè)是根據(jù)需要設(shè)定欠壓值, 然后采樣當(dāng)前電源電壓, 若電壓低于設(shè)定值,則關(guān)閉輸出, 相反, 則進(jìn)行限流保護(hù)檢測(cè)。在運(yùn)行的過程中應(yīng)時(shí)刻檢測(cè)是否有剎車信號(hào)輸人, 若有剎車信號(hào)輸人, 則關(guān)閉輸出。直流無刷電機(jī)的3個(gè)霍爾元件組合起來有8種狀態(tài), 其中6種是有效的, 對(duì)應(yīng)1個(gè)輸出的狀態(tài)。若電機(jī)需要反轉(zhuǎn), 只需增加一個(gè)反轉(zhuǎn)狀態(tài)表即可。2 啟動(dòng)理論上講, 轉(zhuǎn)子位置過磁場(chǎng)換相臨界點(diǎn)時(shí), 電流換相的速度越快越好。但是在電動(dòng)自行車控制場(chǎng)合,這樣的想法是沒有必要的。設(shè)電動(dòng)自行車運(yùn)行在最高速20km/s(這是國家法律規(guī)定的速度限制), , 。這樣做的好處是可以減小中斷程序的執(zhí)行時(shí)間, 程序運(yùn)行更加流暢。定時(shí)器在每個(gè)時(shí)間周期增加1。若想控制定時(shí)器定時(shí)時(shí)間, 可以在其中斷程序里面將定時(shí)器置數(shù), 定時(shí)器便從這個(gè)數(shù)開始計(jì)數(shù)直到溢出。須注意對(duì)有的定時(shí)器計(jì)數(shù)值寄存器寫的時(shí)候, 會(huì)把預(yù)分頻值清除, 因此必須在寫計(jì)數(shù)值的同時(shí)重新寫預(yù)分頻值控制字。因此, 要在中斷程序中控制下次PWM中斷的時(shí)間有兩個(gè)方法:一是改變PR2值, 一是對(duì)TIMER2置數(shù), 改變其初始值。4 剎車控制剎車控制在主程序里面, 主程序時(shí)刻檢測(cè)剎車信號(hào), 當(dāng)有剎車信號(hào), 關(guān)斷波的輸出若沒有剎車信號(hào), 根據(jù)轉(zhuǎn)把輸入的電壓, 控制波的輸出。6 PWM脈寬時(shí)間算法PWM周期和占空比計(jì)算公式為:PWM周期=[(PR2)+l]*4*TOSC*(TMR2預(yù)分頻值)，TOSC為晶振周期:PWM占空比=(CCPRIL:CCPICON5:4)*TOSC*(TMR2預(yù)分頻值)。軟件定時(shí)器根據(jù)調(diào)速要求產(chǎn)生直流斬波電壓，采用中斷方式運(yùn)行，改變斬波電壓只需在對(duì)應(yīng)單元寫入控制值。剎車信號(hào)、過流信號(hào)和欠壓信號(hào)順次讀入，并進(jìn)行相應(yīng)處理。 本文所設(shè)計(jì)的基于PIC單片機(jī)的無刷直流電機(jī)控制器具有硬件結(jié)構(gòu)簡單、保護(hù)功能完善、軟件采用模塊化設(shè)計(jì)易于用戶二次開發(fā)等特點(diǎn)。 由于時(shí)間與能力有限，本文所設(shè)計(jì)的控制系統(tǒng)還有待于進(jìn)一步的改進(jìn)，比如可采用無位置傳感器的控制方法，利用軟件檢測(cè)電機(jī)的反電動(dòng)勢(shì)，從而省去位置傳感器，降低硬件成本，提高可靠性。致 謝在做畢業(yè)設(shè)計(jì)這段時(shí)間里，胡老師給了我很多指導(dǎo)和建議，讓我對(duì)無刷電機(jī)控制系統(tǒng)有了很多了解，并學(xué)到了很多對(duì)我有用的東西。謝謝胡老師！參考文獻(xiàn)1 :科學(xué)出版社，20052 李鐘明,:國防工業(yè)出版社，19993 ，19964 陳清泉，:清華大學(xué)出版社，廣州:暨南大學(xué)出版社，20005 ，2004 6 :江蘇科學(xué)技術(shù)出版社，20017 ，19968 韋敏，20049 盧靜，陳非凡，200210 梁正峰，200411 陳鋼，12 ，200013 謝運(yùn)祥,. 機(jī)械工業(yè)出版社，200714 ，200715 許大中,，200216 王成元,夏加寬,楊俊友,，200617 姚國強(qiáng),錢銳,. 辭學(xué)出版社，200618 . 機(jī)械工業(yè)出版社，200419 [日]，200620 黃俊,. 機(jī)械工業(yè)出版社，200421 余永權(quán),汪明慧, ，200322 ，199623 ，199724 張立,．北京機(jī)械工業(yè)出版社，199525 余永權(quán),李小青,. 北京航空航天大學(xué)出版社,199126 李志民,199527 ．北京機(jī)械工業(yè)出版社,2004附錄1Brushless DC (BLDC) Motor FundamentalsBrushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are used in industries such as Appliances, Automotive,Aerospace, Consumer, Medical, Industrial Automation quipment and the name implies, BLDC motors do not use brushesfor mutation。 however, the windings are distributed in a different manner. Most BLDC motors have three stator windings connected in star fashion. Each of these windings are constructed with numerous coils interconnected to form a winding. One or more coils areplaced in the slots and they are interconnected to make a winding. Each of these windings are distributed over the stator periphery to form an even numbers of poles. There are two types of stator windings variants: trapezoidal and sinusoidal motors. This differentiation is made on the basis of the interconnection of coils in the stator windings to give the different types of back Electromotive Force (EMF). Refer to the “What Is Back EMF” section for more information.As their names indicate, the trapezoidal motor gives a back EMF in trapezoidal fashion and the sinusoidal motor!ˉs back EMF is sinusoidal, as shown in Figure and Figure2. In addition to the back EMF, the phase current also has trapezoidal and sinusoidal variations in the respective types of motor. This makes the torque output by a sinusoidal motor smoother than that of a trapezoidal motor. However, this es with an extra cost, as the sinusoidal motors take extra winding interconnections because of the coils distribution on the stator periphery, thereby increasing the copper intake by the stator windings.Depending upon the control power supply capability, the motor with the correct voltage rating of the stator can be chosen. Fortyeight volts, or less voltage rated motors are used in automotive, robotics, small arm movements and so on. Motors with 100 volts, or higher ratings, are used in appliances, automation and in industrial applications.RotorThe rotor is made of permanent magnet and can vary from two to eight pole pairs with alternate North (N) and South (S) poles.Based on the required magnetic field density in the rotor, the proper magnetic material is chosen to make the rotor. Ferrite magnets are traditionally used to make permanent magnets. As the technology advances, rare earth alloy magnets are gaining popularity. The ferrite magnets are less expensive but they have the disad vantage of low flux density for a given volume. In contrast, the alloy material has high magnetic density per volume and enables the rotor to press further for the same torque. Also, these alloy magnets improve the sizetoweight ratio and give higher torque for the same size motor using ferrite magnets.Neodymium (Nd), Samarium Cobalt (SmCo) and the alloy of Neodymium, Ferrite and Boron (NdFeB) are some examples of rare earth alloy magnets. Continuous research is going on to improve the flux density to press the rotor further.Figure4 shows cross sections of different arrangements of magnets in a rotor.Hall SensorsUnlike a brushed DC motor, the mutation of a BLDC motor is controlled electronically. To rotate the BLDC motor, the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position is sensed using Hall effect sensors embedded into thestator.Note: Hall Effect Theory: If an electric current carrying conductor is kept in a magnetic field, the magnetic field exerts a transverse force on the moving charge carriers which tends to push them to one side of the conductor. This is most evident in a thin flat conductor. A buildup of charge at the sides of the conductors will balance this magnetic influence, producing a measurable voltage between the two sides of the conductor. The presence of this measurable transverse voltage is called the Hall effect after E. H. Hall who discovered it in 1879.