译 文伺服电机原理及应用电机是如何工作的电动机是将电能转换成机械运动/电机用在家用电器/电动风扇/遥控玩具等各种使用场合电机起源于早期电学上的一个发现- Arago转动/在1824年/ Francois Arago发现悬浮在铜盘上的磁针/在铜盘转动时也跟着转动/第二年/计算机先驱Charles Babbage和天文学家John Herschel向人们展示上述运动可以相逆的/转动一块位于铜盘上方较强的磁铁时/铜盘也转动/在1831年/ Michael Faraday通过试验来解释这一现象发生的原因/在电机实际运用前/半个多世纪来做这些电机些基础研究过了几十年后/许多发明家不断改进发明将电能转换成机械能/其中一个就是1832 Hippolyte Pixii改进了之后称为换向器的发明/它通过改变位于两个或更多的固定电磁石电流方向/以维持一台电机连续运转/ Thomas Davenport是第一个制造出在工业中使用的电机/并是第一个对电机申请专利的/不久电机被用作诸如交通运输等场合/ Moritz-Hermann De Jacobi将一台电机安装在涅瓦河上的一条船上/ Charles G/ Page用电机做了一台小型机车/伴随着19世纪80年代商业性电力供应系统出现/制造出更大的电机也变得有可能/ Edison鼓励在工业中便用电机/并且设计了几一些为工业使用兵新型电机在19世纪80年代到90年代发生了一个重大变化/电力公司开始考虑转成交流电/交流适合于长距离传输/并且在Edison的电灯上工作的很好/但是没有实际的交流电机存在/直到意大利的Galileo Ferraris和美国的Nikola Tesla/ 在今天人们认为Tesla的贡献比Ferraris大部分原因是前者后来受雇于西屋公司/这家公司应用了他自己的及其他人的专利/成了为电气设备一个主要的生产者/随着交流电机成为可能/交流电力的发展/交流电机一直使用到现在。伺服电机伺服电机包括交流电机和直流电机。早期的伺服电机通常是直流电机，因为那时只有通过可控硅才能控制大电流。由于晶体管能够控制大电流/并在更高的频率转换大电流，交流电机使用越来越广泛。早期的伺服电机是特别为伺服放大器设计的。如今电机设计则可应用于伺服放大器或变频***。这意味着，电机一方面可以用于伺服系统，另一方面可以用于变频驱动。一些公司把不使用步进电机的环闭系统称为伺服系统，因此与调速器相连接的交流异步电机也可以被称作为伺服电机。伺服电机还有些地方需要改进，包括在额定转速内运行不过热，电机静止时仍能保证足够的扭矩去承受负载在规定的位置，以及超低速长时间转动不过热。旧型电机***风扇是直接连在接电机主轴上。当电机工作在低速时，风扇不能产生足够的气流来***电机。新一代的电机拥有***的风扇安装在电机上，所以能提供足够的***气流。这个风扇动力来自一个恒压源所以可以使风扇能始终运行在最高转速下，而不管伺服电机的转速如何。在所有伺服电机中，最实用的是永磁电动机。永磁电机的绕组电压可以是交流也可以是直流/这类永磁电机同以前的永磁电机类似。图1-1显示的是一台普通永磁电机的剖示图。图1-2展示的是伺服永磁电机的剖示图。从图中可以看出，新的电机在轴承室，转子，定子上同以前的电机类似。主要的区别只在于这种新类型的电机可以较大的负载从静止状态动作。这类永磁电机同样有一个编码器或变压器被放置在电机内部。这个可以确保设备能更精确的显示电机轴的位置或速度。 图1-1 典型永磁电机图1-2剖视图 永磁伺服电机无刷伺服电机无刷伺服电机可以无碳刷运行，这就意味着它的换向现在需要由电子完成而不是由机械碳刷来完成。电子换向由晶体管以某种周期方式开关来实现的。图1-3显示三条输入到无刷伺服电机的电压和电流波形。图1-4显示一台三相绕组的无刷伺服电机，这种无刷伺服电机的主要特点是可以交流或直流电源驱动。图1-3(a)输入电压、电流方波梯形波表(b)正弦电压和正弦输入电压和方波输出电压波型(c)正玄输入电压和正弦电流波形 这已经成为最流行的无刷式伺服控制图1-3展示三种电压波形来驱动无刷伺服电机。图1-3a展示梯形反电动势电压，方波电流输入，图1-3b显示为一正弦波输入电压和一方波电流波形，图-3c显示一正弦波办公设备电压放一正弦波电流波形/正弦波电压和正弦波电流波形是无刷伺服电机最常用的驱动。图1-4（a）晶体管三相绕阻无刷伺服电机。（b）三相绕阻电机使用三个***的电压波形。（c）波形信号用来控制晶体管的波形序列。（d）反电势波形。图1-4展示三组晶体管/它同变频驱动的输出端很相似/在图1-4a，连接到电机三相绕阻的晶体管同变频驱动基本相同。图1-4b晶体管输出波形图，它是由三组***的正弦波形组成。图1-4c是输入到每个晶体管的控制端的波形。图1-4d显示驱动波形的反电势。伺服电机***伺服电机***使一台伺服电机不只是用于放大器功能。今天的伺服电机***既要能做一定量的判断，也要提供一种方法能接受外部传感器和内部控制的信号，同时也可以在主***，PLCS和伺服系统数据交换。图1-5展示一些伺服电机与放大器。从图中看/这些同其它类型的电机和***比较相似。图1-5 伺服电机与放大器图1-6显示一张伺服电机***的图/你可以从中看出与其它类型电机的不同之处。图中的***用于直流伺服电机。输入电源，伺服电机及转速计连接到***底部的P3端口。可以看出输入电源为115V单相交流电。一个主断路器串联在L1线上。由L1和N经过的电源经过一个隔离的降压变压器/变压器的次级电压可是介于20到85伏的之间的任意电压。***通过引脚8接地/你应该记得在这点接地只是用来对系统的金属部份提供短路保护。图1-6 伺服控制图 （此图显示将数字信号和模拟信号送到***，再由信号***将信号送回给所在的主***或可编程***）伺服电机边接***的4脚和5脚。其中5脚是+，4脚是-。3脚是对电机和***提供一种***接地保护。转速计连接到引脚1和引脚2，其中脚2是+，脚1是-。***线缆同电机外壳连接/连接到这个端口的引线应该比同其它端口的引线要粗，因为他们承受更大的电机电流。如果电机使用额外的散热风扇，它也应该连接到这个端口上，在绝大部分场合，散热风扇由一常规的110V或240V的单相或三相交流电供电。控制信号通过P1端口送到***/控制信号的引脚是1和2/其中1是+/2是-/这是一种非接地常规的信号/同电路中其它部分不共享接地/一些附加的辅助信号也连接到P1。这些信号包括约束，如可以通过外部***来使驱动失效。正反转命令，如要求***给电机通电，使电机按顺时针方向或逆时针方向转动。在某些场合，最大正转行程极限开关和最大反转行程开关连接到一起，以便当机器运行到极限位置时触发另一状态的开关。这时将自动的以反方向重新驱动。P1端品也提供一些数字输出信号/一通常用于送出一些故障信号或其它信息/诸如正在运转/到主***或PLC/P1端口主要是数字(1-0)信号的端口。P2端口是逻辑信口的窗口，总线上的典型信号包括电机电流和电机转速信号由伺服***送出，送入主机或PLC，以便做出正确逻辑判断以确保***能出正确信息到电机上。从主机或PLC上的输入信号也被送到***上来设置驱动的最大电流和转速。在更新的数字驱动中，这些值由编好程序的驱动参数来控制的。脉宽调制伺服放大器脉宽伺服放大器被用作小尺寸的伺服场合，如使用直流有刷伺服电机。图1-7展示这一类型放大器的图。从左下图中可以看到单相交流电源供电给放大器。右上图中交流电经整流后，被送到驱动的输出单元，动输出单元用四个IGBT来产生脉宽调制波形。IGBT连接后以便他们提供30-120V直流电压，高达30A的电流到直流有刷伺服电机。电机的极性由图中显示。在这张图的中间的保留电路显示一些从故障逻辑板上的故障电路，在图的下方提供一路输出信号。可以看到故障输出信号包括过压/过温及过电流。第四个信号作为SSO(系统状态输出)。它显示当故障发生时的系统状态。一个跳线用来设置SSO信号。 在这张图的右下角的输入脚用来显示驱动的的使能控制或抑止，选择是前过放大控制还是向后放大控制。抑制信号作为控制信号。当放大器过高的时抑制输出过程。FAC和RAC信号***电流到放大或缩小5%。左上方显示的是输入信号。VCS(速度控制信号)要求一个+VCS和一个-VCS信号来提供不同的信号。伺服放大器和电机的应用场合可以从伺服电机和放大器一些典型的应用场合延升到其它更好的使用场合。图-8显示的是一台伺服电机被用作控制一个压力切割器。在这个应用表中，薄片材料被送入一个卷压器中，在那儿它被用一把刀刃切长一定长度。薄片材料可以是一个带有切断点标记的商标或是广告纸。带有切断点标记的。在这个场合中，薄片材料的速度和位置司切断点保持同步。反馈传感器可以是一个编码器或是***器/它同一个光电传感器连接在一起，用来判断标记的位置。所提供的操作面板用来使操作者能减慢系统动作，以维护刀刃或是换一卷新的材料。面板上可以进行参数调整以适应每一种原料。系统也可以同一个可编程的***或其它类型的***连接，以便操作面板上可以用来选择每一种材料或产品在运行时的正确的切断点。图1-7图示 脉宽调制放大器直流有刷伺服电机图1-8 由伺服电机控制材料压入的速度来确保尺寸灌装流水线伺服控制应用实例第二个应用如图1-9所示。在这个应用中若干个填充头和瓶子一样排列成一直线向前移动。每个填充头必须与每个瓶子以及瓶子运行的轨道相配合。喷嘴跟着瓶子移动并且填充物料。这里使用把10个喷嘴安装在机架上并通过滚珠丝杠装置来传动。滚珠丝杆也叫做螺杆。当电机转动丝杆轴，机架会水平地沿着丝杆轴长度移动。这个平稳的运动能够使每个喷嘴将物料装入凭中，而且几乎不会有溢出。伺服驱动系统利用一个定位***驱动软件来确定的传送带的位置和速度实现瓶子的移动。主编程轨迹是瓶子沿着传送线向前移动。螺旋流入的方式是利用在进入灌注区域的前点。螺旋流入方式是根据每个瓶子进入灌注区域所保持的间距精确数据计算所得。瓶子都在接近螺旋灌注点被紧紧的固定，但是当瓶子通过螺旋灌注点时位置间距是十分精确的，所以喷嘴和瓶子颈部有足够的空间相配合。传感器联合检测系统确保在瓶子错位，或者瓶子与瓶子之间出现过大距离时，喷嘴不会再喷出物料。伺服驱动系统对来自主编程器的瓶子位置与显示了安装在螺旋丝杆上的填充机架位置的反馈信号进行比较。伺服驱动放大器会增加或减少滚珠丝杠装置的速度/使喷嘴与瓶子的速度准确的匹配。图1-9 应用伺服电机控制的饮料灌装机精确螺旋伺服控制系统应用实例伺服系统第三方面的应用如图110所示。这个应用中使用一个巨大的供应槽来给沿着转送带运动的容器填料。材料被灌入到容器内，可以仅仅放入一种材料也可以是将某一种材料倾倒在搅拌器进行混合搅拌操作后再灌入到容器中。因此，所有灌入到容器内的材料必须被准确的称量过才能装入。伺服系统通过一个丝杆进行控制。反馈传感器在这个系统中是一个称量系统，例如测压元件在前面的章节已经讨论过。命令信号来自一个可编程***或者工作人员可以选择手动控制，在操作终端上进行控制。命令信号来自一个可编程***或者工作人员可以从操作终端上手动选择一个配方。材料的数量多少是根据不同的配方决定。图110 实施精确数字螺旋伺服控制的灌注机螺旋杆的速度是可以调整的，当容器刚开始灌注时，螺旋杆是高速运转的，当达到经过准确计量出容器在最后罐满前适当的刻度时，螺旋杆以额定的低速运转。由于材料价格的增长，精密的灌注设备在使用规定的配方下在相同产品数量下即可以提高节约材料又能保证质量。利用伺服电机打印标签应用实例第四个应用是由伺服电机控制标签打印机的预印标签牵引滚筒的速度，当盒子穿过标签打印机构时把标签印在随着连续传送带系统移动的盒子上。反馈信号由三个装置共同提供，一个能指示传送带位置的 编码器，一个能指示传送带速度的技术发生器，还有个能显示每个标签的注册记号的传感器。由一个微型处理器来控制伺服位置系统设定误差信号， 并由伺服放大器提供功率信号给伺服电机。如图111所示。图111 由伺服电机控制标签打印机的应用伺服电机控制随机定时横切系统应用实例第5中运用在11-94中出现。同时，那页还展示了一个系列的组件设备。这个设备可以分为3个***的机器使用。每个组件系统所在的站点的定时循环周期是与外界相***的。组件系统由infeed传送带，一个定位传送带和一个缠绕站点。infeed传送带和缠绕站点是相互机械连接的，所以它们等速运转。缠绕站点上的组件的位置是被严格控制的，这使得各组件不至于相互过于紧密。一块被称为 飞行的金属 与缠绕站点传送带在某个特定接点连接以保证每个组件各就各位。一个传感器被安装在定位传送带的开始端使得能在组件开始移向定位传送带时确定组件的前边界。另一个传感器被安装在了组件传送带的底部以观察金属的 运行。 所以这些从传感器发出的信号都被发送到辞赋电机以提供信息数据，所以辞赋器可以调节定位传送带的速度。这样可以使每个组件当它移向组件传送带时都能和某个 运行 器排列成一条直线。这种运用说明了辞赋定位***可以应对从2个以上传感器发出的各种不同的信号，原因是它使用了微处理器 。图112伺服电机控制随机定时功能包装系统原文说明原文说明的内容是：文章阐述了电机的工作原理、发展过程、以及伺服电机的工作控制原理。并且举例说明了伺服电机所适用的场合。题名Servomotors Elements and Applications作者 NEWMARKER来源 佳工机电网How Does a Motor Work?An electric motor converts electricity into mechanical motion/ Electric motors are used in household appliances/ electric fans/ remote-controlled toys/ and in thousands of other applications/ The electric motor grew out of one of the earliest discoveries in electric scienceAragos rotations/ In 1824/ Francois Arago discovered that a magnetic needle suspended over a copper disk would rotate when the disc was spun/ The next year/ computer pioneer Charles Babbage and astronomer John Herschel showed that the action could be reversed/ spinning a more powerful magnet above the copper disk would spin the copper disc/ Then/ in 1831/ Michael Faraday conducted experiments that helped explain why this took place/ While this laid the groundwork for the electric motor/ it was another half century before electric motors were doing useful work/ Over the next few decades many inventors made improved devices for turning electricity into motion/ One of these was Hippolyte Pixiis 1832 improvement called the commutator/ which switched the flow of current between two or more sets of stationary electromagnets to keep a motor continuously rotating/ Thomas Davenport was the first to build an electric motor large enough to be used in industry/ and he was also the first to seek a patent on a motor/ Soon electric motors were being used for such things as transportation/ Moritz-Hermann De Jacobi used an electric motor on a boat on the Neva River/ and Charles G/ Page used one to build a small locomotive/ After the appearance of commercial electric power systems in the 1880s/ larger electric motors were possible/ Edison encouraged the use of electric motors in industrial applications and designed several new electric motors for that purpose/ An important change came in the later 1880s and 1890s/ when electric power companies began considering the switch to alternating current/ Alternating current was perfect for the distribution of electric power over long distances/ and it worked well with the Edison electric lamp/ but no practical AC motor existed until the works of Galileo Ferraris in Italy and Nikola Tesla in the United States/ Teslas contributions are remembered today more than Ferraris in part because Tesla was subsequently hired by the Westinghouse corporation/ which used his patents along with many others to become one of the major producers of electric equipment/ With a suitable AC motor available/ AC power took off/ It is still in use today/ServomotorServomotors are available as AC or DC motors/ Early servomotors were generally DC motors because the only type of control for large currents was through SCRs for many years/ As transistors became capable of controlling larger currents and switching the large currents at higher frequencies/ the AC servomotor became used more often/ Early servomotors were specifically designed for servo amplifiers/ Today a class of motors is designed for applications that may use a servo amplifier or a variable-frequency controller/ which means that a motor may be used in a servo system in one application/ and used in a variable-frequency drive in another application/ Some companies also call any closed-loop system that does not use a stepper motor a servo system/ so it is possible for a simple AC induction motor that is connected to a velocity controller to be called a servomotor/Some changes that must be made to any motor that is designed as a servomotor includes the ability to operate at a range of speeds without overheating/ the ability to operate at zero speed and retain sufficient torque to hold a load in position/ and the ability to operate at very low speeds for long periods of time without overheating/ Older-type motors have cooling fans that are connected directly to the motor shaft/ When the motor runs at slow speed/ the fan does not move enough air to cool the motor/ Newer motors have a separate fan mounted so it will provide optimum cooling air/ This fan is powered by a constant voltage source so that it will turn at maximum RPM at all times regardless of the speed of the servomotor/ One of the most usable types of motors in servo systems is the permanent magnet (PM) type motor/ The voltage for the field winding of the permanent magnet type motor can be AC voltage or DC voltage/ The permanent magnet-type motor is similar to other PM type motors presented previously/ Figure-1 shows a cutaway picture of a PM motor and Fig/-2 shows a cutaway diagram of a PM motor/ From the picture and diagram you can see the housing/ rotor and stator all look very similar to the previous type PM motors/ The major difference with this type of motor is that it may have gear reduction to be able to move larger loads quickly from a stand still position/ This type of PM motor also has an encoder or resolver built into the motor housing/ This ensures that the device will accurately indicate the position or velocity of the motor shaft/FIGURE 1-1 Typical PM servomotorsFIGURE 1-2 Cutaway picture of a permanent magnet servomotorBrushless ServomotorsThe brushless servomotor is designed to operate without brushes/ This means that the commutation that the brushes provided must now be provided electronically/ Electronic commutation is provided by switching transistors on and off at appropriate times/ Figure 1-3 shows three examples of the voltage and current waveforms that are sent to the brushless servomotor/ Figure 1-4 shows an example of the three windings of the brushless servomotor/ The main point about the brushless servomotor is that it can be powered by either ac voltage or dc voltage/ FIGURE 1-3 (a) Trapezoidal input voltage and square wave current waveforms/ (b) Sinusoidal input voltage and sinusoidal voltage and square wave output voltage waveforms/ (c) Sinusoidal input voltage and sinusoidal current waveforms/ This has become the most popular type of brushless servomotor control/Figure 1-4 shows three sets of transistors that are similar to the transistors in the output stage of the variable-frequency drive/ In Fig/ l-4a the transistors are connected to the three windings of the motor in a similar manner as in the variable-frequency drive/ In Fig/ l-4b the diagram of the waveforms for the output of the transistors is shown as three separate sinusoidal waves/ The waveforms for the control circuit for the base of each transistor are shown in Fig/ l-4c/ Figure l-4d shows the back EMF for the drive waveforms/ FIGURE 11-86 (a) Transistors connected to the three windings of the brushless servomotor/ (b) Waveforms of the three separate voltages that are used to power the three motor windings/ (c) Waveforms of the signals used to control the transistor sequence that provides the waveforms for the previous diagram/ (d) Waveform of the overall back EMFServomotor Controllers Servomotor controllers have become more than just amplifiers for a servomotor/ Today servomotor controllers must be able to make a number of decisions and provide a means to receive signals from external sensors and controls in the system/ and send signals to host controllers and PLCs that may interface with the servo system/ Figure 1-5 shows a picture of several servomotors and their amplifiers/ The components in this picture look similar to a variety of other types of motors and controllers/ FIGURE 1-5 Example servomotors and amplifiersFigure 1-6 shows a diagram of the servomotor controller so that you can see some of the differences from other types of motor controllers/ The controller in this diagram is for a DC servomotor/ The controller has three ports that bring signals in or send signals out of the controller/ The power supply/ servomotor/ and tachometer are connected to port P3 at the bottom of the controller/ You can see that the supply voltage is 115-volt AC single phase/ A main disconnect is connected in series with the LI wire/ The LI and N lines supply power to an isolation step-down transformer/ The secondary voltage of the trans-former can be any voltage between 20 and 85 volts/ The controller is grounded at terminal 8/ You should remember that the ground at this point is only used to provide protection against short circuits for all metal parts in the system/ The servomotor is connected to the controller at terminals 4 and 5/ Terminal 5 is + and terminal 4 is - / Terminal 3 provides a ground for the shield of the wires that connect the motor and the controller/ The tachometer is connected to terminals 1 and 2/ Terminal 2 is + and terminal 1 is - / The shield for this cable is grounded to the motor case/ The wires connected to this port will be larger than wires connected to the other ports/ since they must be capable of carrying the larger motor current/ If the motor uses an external cooling fan/ it will be connected through this port/ In most cases the cooling fan will be powered by single-phase or three-phase AC voltage that remains at a constant level/ such as 110 volts AC or 240 volts AC/ FIGURE 1-6 Diagram of a servo controller/ This diagram shows the digital (on-off) signals and the analog signals that are sent to the controller/ and the signals the controller sends back to the host controller or PLC/The command signal is sent to the controller through port PI/ The terminals for the command signal are 1 and 2/ Terminal 1 is + and terminal 2 is - / This signal is a type signal/ which means that it is not grounded or does not share a ground potential with any other part of the circuit/ Several additional auxiliary signals are also connected through port 1/ These signals include inhibit (INH)/ which is used to disable the drive from an external controller/ and forward and reverse commands (FAC and RAC)/ which tell the controller to send the voltage to the motor so that it will rotate in the forward or reverse direction/ In some applications/ the forward maximum travel limit switch and reverse maximum travel limit switch are connected so that if the machine travel moves to the extreme position so that it touches the overtravel limit switch/ it will automatically energize the drive to begin travel in the opposite direction/ Port PI also provides several digital output signals that can be used to send fault signals or other information such as drive running back to a host controller or PLC/ Port PI basically is the interface for all digital (on-off) signals/ Port P2 is the interface for analog (0-max) signals/ Typical signals on this bus include motor current and motor velocity signals that are sent from the servo controller back to the host or PLC where they can be used in verification logic to ensure the controller is sending the correct information to the motor/ Input signals from the host or PLC can also be sent to the controller to set maximum current and velocity for the drive/ In newer digital drives/ these values are controlled by drive parameters that are programmed into the drive/ PWM Servo Amplifier The PWM servo amplifier is used on small-size servo applications that use DC brush-type servomotors/ Figure 1-7 shows a diagram for this type of amplifier/ From the diagram you can see that single-phase AC power is provided to the amplifier as the supply at the lower left part of the diagram/ The AC voltage is rectified and sent to the output section of the drive that is shown in the top right comer of the diagram/ The output section of the drive uses four IGBTs to create the pulse-width modulation waveform/ The IGBTs are connected so that they provide 30-120 volts DC and up to 30 A to the brush-type DC servo-motor/ The polarity of the motor is indicated in the diagram/ The remaining circuits show a variety of fault circuits in the middle of the diagram that originate from the fault logic board and provide an output signal at the bottom of the diagram/ You should notice that the fault output signals include overvoltage/ overtemperature/ and overcurrent/ A fourth signal is identified as SSO (system status output)/ which indicates the status of the system as faulted anytime a fault has occurred/ A jumper is used to set the SSO signal as an open collector output with a logic level 1 indicating the drive is re
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