【正文】 008：197468.[8] 羅艷紅 [M]. 北京：機(jī)械工業(yè)出版社，2009：1247.[9] 西門子（中國(guó)） PLC[M]. 北京：北京航空航天大學(xué)出版社，2004：1208.[10] 高金源 [M]. 北京：清華大學(xué)出版社，2007：128169. 附錄A 英文資料Stepper Motor Basics A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical mand pulses are applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied.Stepper Motor Advantages and DisadvantagesAdvantages 1. The rotation angle of the motor is proportional to the input pulse.2. The motor has full torque at standstill (if the windings are energized)3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step and this error is non cumulative from one step to the next.4. Excellent response to starting/stopping/reversing.5. Very reliable since there are no contact brushes in the motor. Therefore the life of the motor is simply dependant on the life of the bearing.6. The motors response to digital input pulses provides openloop control, making the motor simpler and less costly to control.7. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.8. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.Disadvantages 1. Resonances can occur if not properly controlled.2. Not easy to operate at extremely high speeds.Open Loop OperationOne of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. Open loop control means no feedback information about position is needed. This type of control eliminates the need for expensive sensing and feedback devices such as optical encoders. Your position is known simply by keeping track of the input step pulses.Stepper Motor TypesThere are three basic stepper motor types. They are :? Variablereluctance? Permanentmagnet? HybridVariablereluctance (VR)This type of stepper motor has been around for a long time. It is probably the easiest to understand from a structural point of view. Figure 1 shows a cross section of a typical . stepper motor. This type of motor consists of a soft iron multitoothed rotor and a wound stator. When the stator windings are energized with DC current the poles bee magnetized. Rotation occurs when the rotor teeth are attracted to the energized stator poles.Figure 1 Crosssection of a variablereluctance(VR) motor.Permanent Magnet (PM)Often referred to as a “tin can” or “canstock” motor the permanent magnet step motor is a low cost and low resolution type motor with typical step angles of 176。 2 phases on)? Micro stepping (Continuously varying motor currents)For the following discussions please refer to the figure 3. Figure 3 Unipolar and bipolar wound stepper motors. In Wave Drive only one winding is energized at any given time. The stator is energized according to the sequence A174。AB 174。 A 174。5 174。 3 174。B 174。6. For unipolar and bipolar wound motors with the same winding parameters this excitation mode would result in the same mechanical position. The disadvantage of this drive mode is that in the unipolar wound motor you are only using 25% and in the bipolar motor only 50% of the total motor winding at any given time. This means that you are not getting the maximum torque output from the motor. In Full Step Drive you are energizingtwo phases at any given stator is energized according to the sequence AB 174。 angleto the fingers), then the thumb will point in the direction of the magnetic field.”Figure 2 shows the magnetic flux path developed when phase B is energized with winding current in the direction shown. The rotor then aligns itself so that the flux opposition is minimized. In this case the motor would rotate clockwise so that its south pole aligns with the north pole of the stator B at position 2 and its north pole aligns with the south pole of stator B at position 6. To get the motor to rotate we can now see that we must provide a sequence of energizing the stator windings in such a fashion that provides a rotating magnetic flux field which the rotor follows due to magnetic attraction.Figure 2 Magnetic flux path through a twopole stepper motor with a lag between the rotor and stator.Torque GenerationThe torque produced by a stepper motor depends on several factors.? The step rate? The drive current in the windings? The drive design or typeIn a stepper motor a torque is developed when the magnetic fluxes of the rotor and stator are displaced from each other. The stator is made up of a high permeability magnetic material. The presence of this high permeability material causes the magnetic flux to be confined for the most part to the paths defined by the stator structure in the same fashion that currents are confined to the conductors of an electronic circuit. This serves to concentrate the flux at the stator poles. The torque output produced by the motor is proportional to the intensity of the magnetic flux generated when the winding is energized.The basic relationship which defines the intensity of the magneticflux is defined by:H = (N i) 247。本系統(tǒng)控制靈活，簡(jiǎn)單方便，制作成本低。本文構(gòu)建了一個(gè)步進(jìn)電機(jī)控制系統(tǒng)，系統(tǒng)的硬件組成主要有：51系列單片機(jī)、L298N驅(qū)動(dòng)電路、直流電壓源工作。EA=1。這種程序在執(zhí)行過(guò)程中由于外界的原因而被中間打斷的情況稱為“中斷”。定時(shí)掃描方式只要定時(shí)時(shí)間到，CPU就去掃描鍵盤，工作效率有了一定的提高。 按鍵的確認(rèn)按鍵的確認(rèn)就是判別按鍵是否閉合，反映在電壓上就是和按鍵相連的引腳呈現(xiàn)出高電平或低電平。目前，單片機(jī)應(yīng)用系統(tǒng)中最常見(jiàn)的觸點(diǎn)式開(kāi)關(guān)按鍵。8腳（R1IN）、9腳（R1OUT）、10腳（T1IN）、7腳（T1OUT）為第二數(shù)據(jù)通道。給出了采用MAX232芯片的PC機(jī)和單片