【正文】 IR2110功能介紹 17 自舉電路原理 19 單片機的選擇 20 PIC單片機特點 20 PIC16F72單片機管腳排列及功能定義 22 PIC16F72單片機的功能特性 22 PWM信號在PIC單片機中的處理 23 時鐘電路 23 復位電路 24 人機接口電路 24 轉把和剎車 24 顯示電路 25 門陣列可編程器件GAL16V8 27 GAL16V8圖及引腳功能 27 傳感器選擇 28 周邊保護電路 30 電流采樣及過電流保護 30 LM358雙運放大電路 31 欠電壓保護 32 電源電路 32第4章 無刷直流電動機軟件設計 33 直流無刷電機控制器程序的設計概況 33 系統(tǒng)各部分功能在軟件中的實現(xiàn) 33 軟件流程圖 34結束語 36致謝 37參考文獻 38附錄1 39附錄2 51第1章 概 述 無刷直流電動機的發(fā)展概況無刷直流電動機是在有刷直流電動機的基礎上發(fā)展起來的，這一淵源關系從其名稱中就可以看出來。隨著人們對無刷直流電動機特性了解的日益深入，無刷直流電動機的理論也逐漸得到了完善。電樞產(chǎn)生的熱量消散在氣隙內(nèi)，這樣增加了氣隙溫度，從而限制了輸出功率/外形尺寸之比轉自慣量低。轉子在空間每轉過60電角度，定子繞組就進行一次換流，定子合成磁場的磁狀態(tài)就發(fā)生一次躍變。本設計選用的是三相無刷永磁直流電動機，其額定電壓UH=36V,電樞額定電流IaH=,電樞峰值電流IaP15A,額定轉速nH=350r/min,額定功率PH=250W。圖15 工作特性在輸出額定轉矩時,電機效率高、損耗低是無刷直流電動機的重要特點之一。轉子位置傳感器是整個驅動系統(tǒng)中最為脆弱的部件，不僅增加了系統(tǒng)的成本和復雜性，而且降低系統(tǒng)的可靠性和抗干擾能力，同時還需要占據(jù)一定的空間位置。減小轉矩脈動是提高無刷直流電動機性能的重要方面。原直流電動機的電刷和機械換向器被逆變器和轉子位置檢測器所代替。綜合以下三個指標有助于我們做出正確的選擇：（1）繞組利用率。相數(shù)越多，逆變器電路使用的開關管越多，成本越高。但是位置傳感器的存在增加了系統(tǒng)的成本和體積，降低了系統(tǒng)可靠性，限制了無刷直流電動機的應用范圍，對電機的制造工藝也帶來了不利的影響。在電機轉速控制方面，絕大多數(shù)場合數(shù)字調(diào)速系統(tǒng)已取代模擬調(diào)速系統(tǒng)?？刂破魇请妱幼孕熊嚨尿寗酉到y(tǒng)，它是電動自行車的大腦。在有位置傳感器的控制方法中，現(xiàn)今，由于霍爾傳感器性價比高，安裝方便，被廣泛應用作為無刷直流電機的位置傳感器。（4）周邊輔助、保護電路主要有電流采樣電路、電壓比較電路、過電流保護電路、調(diào)速信號和制動信號等輸入電路。GTR耐壓高，電流大，開關特性好，通流能力強，飽和壓降低開關速度低，為電流驅動，所需驅動功率大，驅動電路復雜，存在二次擊穿問題采用CMOS 施密特觸發(fā)輸入,以提高電路抗干擾能力。當SD輸入高電平時兩路均關閉。由于每個高電壓DMOS電平轉換器僅在 很狹窄的脈沖持續(xù)期內(nèi)才導通，所以功率很低。(2)安全因素。PIC系列單片機具有高，中，低3個檔次，可以滿足不同用戶開發(fā)的需求，適合在各個領域中的應用。(5)功耗低 由于PIC系列單片機采用CMOS結構，使其功率消耗極低。電池欠壓信號：電池電壓經(jīng)分壓后接單片機管腳3。8位定時器/計數(shù)器TMRO，帶8位預分頻 內(nèi)置自振式(RC振蕩)看門狗 時鐘電路 如圖35所示，單片機的10腳外接16Mhz晶體。同時也有少數(shù)高檔車采用霍爾元件做開關，剎車時輸出高電平給控制器，實現(xiàn)剎車斷電功能，即高電位剎車，也稱之為電子剎把。 引出端符號 CLOCK ：時鐘輸入端。按照霍爾器件的功能可將它們分為:霍爾線性器件和霍爾開關器件。轉子位置傳感器的主要技術指標為：輸出信號的幅值、精度，響應速度，工作溫度，抗干擾能力，損耗，體積重量，安裝方便性以及可靠性等。電角度，永磁體的極弧寬度為180176。圖312 霍爾元件式位置傳感器結構（2）電磁式位置傳感器電磁式位置傳感器的定子由磁芯、高頻激磁繞組和輸出繞組組成。遮光盤處于發(fā)光二極管和光敏三極管中間，盤上開有一定角度的窗口。2 霍爾器件在無刷直流電機中的應用當霍爾傳感器用作無刷直流電機轉子位置信息檢測裝置時，將其安放在電機定子的適當位置，霍爾器件的輸出與控制部分相連。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。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算放大器的場合。欠壓檢測是根據(jù)需要設定欠壓值, 然后采樣當前電源電壓, 若電壓低于設定值,則關閉輸出, 相反, 則進行限流保護檢測。2 啟動理論上講, 轉子位置過磁場換相臨界點時, 電流換相的速度越快越好。定時器在每個時間周期增加1。4 剎車控制剎車控制在主程序里面, 主程序時刻檢測剎車信號, 當有剎車信號, 關斷波的輸出若沒有剎車信號, 根據(jù)轉把輸入的電壓, 控制波的輸出。 本文所設計的基于PIC單片機的無刷直流電機控制器具有硬件結構簡單、保護功能完善、軟件采用模塊化設計易于用戶二次開發(fā)等特點。 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.