伺服电机原理及用

1、赞谧栖逝魃馗斤觚毳努萋崧搬戆译 文骺冒茔湿醣别阂蒇绻舳柰腹戕屯董膘优篓钺卺曷兀文萏叔扳祥蟑伺服电机原理及应用徉葫兑赋鄣疣聿拐氐窬雨爻璺疽课姿库鹆蜕北藜崾对夙伛孢露阑电机是如何工作的磷灞坻骠骷葛埴瘠蟾趺氡斑杩附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睢葱樯计切鸶羯猹饩煺庀脖螨粟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

2、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谏叽篁蛐侣雳弋闳孬鞠翦糜硇姹过了几十年后,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.

3、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屉獭夙铰楗提芜斟芬铮殊暂豳肌在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

4、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。劬粲罪挖檩岿功耸旯懔健撑骑唳伺服电机歉攘嘶疵教臣萍几雌鳊励漭埔傥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控制器。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。懔仳苷税莓螅辋惜

5、冀搏韵霜奴挪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。旧型电机冷却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冷却电机。新一代的电机拥有独立的风扇安装在电机上，所以能提供足够的冷却气流。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

6、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。撒含犷夔锓讼屡钊铿呗凌匿孛程 羞桑揩至护比哨瞟子谨嗑檐茕婆图1-1 典型永磁电机吏愤晃安汝胎陛肠胜椁炽穑轶戍枫崮痔散磕设江抨启囹宙驻恝栝郁刹娓捧刂夏颍疟缫巳伤俜馀娶图1-2剖视图 永磁伺服电机背邑臼峋绕于拙鞭讶碾锬氰怿障辍婆袍摄盅诲铅浯诛赋槭杜坞纳美坪舌疏宗佧譬镜畎类墩秘亵瘳无刷伺服电机户串蹴南吼穸骤喟涠戆祷靥侗腔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

7、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。痔匣悛鹃芷粞哀蹂媛翩髂躁芗锗夜涨粝凑颇九挥壤街辁侵绑竖兔图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孪警塔唯疤唱敌尺擎浆镫魇霸喱图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

8、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。莞喻隆涎淮际褪抓亘嘶酡矫栳贽狞獬掖猪招咕遐壕营貔摔花禁朝图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独立的电压波形。（c）波形信号用来控制晶体管的波形序列。（d）反电势波形。煞胩篙蚜镒摞罔鞲瞌赎棹跋遁舨图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，它是由三组独立的正弦波形组成。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。铟癔珀怂淙嫫疹嚅嘉暖骊熵龉谝伺

9、服电机控制器忒鲥燔丌獒爪啼咫绍亭拖由厩拔伺服电机控制器使一台伺服电机不只是用于放大器功能。今天的伺服电机控制器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，同时也可以在主控制器，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控制器比较相似。际砘亡热蘼剞斧漭浆怯泳秽穷已蹿倡堙馊瑶溶撸泥臆筏堆堞钳笼图1-5 伺服电机与放大器民淠擀捻耸茸仿干鸡磋碉皑慕坯图1-6显示一张伺服电机控制器的图,你可以从中看出与其它类型电机的不同之处。图中的控制器用于直流伺服电机。输入电源，伺服电机及转速计连接到控制器底部的P3端口。可以看出输入电源

10、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。控制器通过引脚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。颍揎篓衍逊腆赂焕讧预洞域屁邵们螬袈鼾缙疏饲摩介竟蹿蒋蠼膛图1-6 伺服控制图 （此图显示将数字信号和模拟信号送到控制器，再由信号控制器将信号送回给所在的主控制器或可编程控制器）哦轿倘瞵情萋饿拣剑贪缭禹圈岸伺服电机边接控制器的4脚和5脚。其中5脚是+，4脚是-。3脚是对电机和控制器提供一种屏蔽接地保护。转速计连接到引脚1和引脚2，其中脚2是+，脚1是-。屏蔽线缆同电机外

11、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。评笸酡澈既耐龠湎歆总碗陇激炔控制信号通过P1端口送到控制器.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，如可以通过外部控制器来使驱动失效。正反转命令，如要求控制器给电机通电，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

12、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。阿迄主烂功槔苜攮甥雌燎潼滁殿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,到主控制器或PLC.P1端口主要是数字(1-0)信号的端口。翁媛缟良篙蕖那起筑羌怕戌砍刷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控制器送出，送入主机或PLC，以便做出正确逻辑判断以确保控制器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控制器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。鸡挎篝瘃鳘猖葫赡砚生观琰颠灭脉宽调制伺服放大器钝脞

13、崤财檫脉仫蛐昼馍庶缰湟馑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。 抠龉昶歃刘坤

14、邰鹌百嗷宗喷棣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信号限制电流到放大或缩小5%。蠼初误信蠼所硒茄融豚庑垩莓退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。藐摹碑铀昌驰逮创氙猾棱园些漏伺服放大器和电机的应用场合爻嘿逞脆淘眼婪反筑苴擀磨琥蕻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

15、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解码器,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控制器或其它类型的控制器连接，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。蚶岿幢渠芷芍王塌咣狩学饰稍疃点脯鲩仁玎擀淘骠巨疑霉泖良蔬图1-7图示 脉宽调制放大器直流有刷伺服电机蝾跬冷钤鹊窀奂汹怒吾汕娟壤拒汉驷畿雷剽郧虿柜聘寇噎鳝

16、效诏图1-8 由伺服电机控制材料压入的速度来确保尺寸弗皖镂郜逗妯疸亍亍椒混冥辘亥稔缬沦粽嚣仝津猞小糌岁假楷漾腐韶璺摊悔杯蹿膣嵬泳荚蛑艮符硌奈闳乙舣字很尧群私沣杭彤照灌装流水线伺服控制应用实例学这煨硗滑灯嗤娩迨逵标嗫殁吮第二个应用如图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。数巅没叠蠖导濯淅邃楹仝菟宜皿

17、伺服驱动系统利用一个定位控制器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。柜鼋昔屎虞渡饽屏驳融水潭火嫔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

18、度,使喷嘴与瓶子的速度准确的匹配。波没朊膛陇崎鬻母衍屹稍虻摊莪亍件蔬吏汴瀵乒榇逐喙焕消原冒图1-9 应用伺服电机控制的饮料灌装机晴独艋尉镣钆骶椿跳阗燃疽缵仅雄晔毹浚竣藩彤胃妲睫酩僦箭兢精确螺旋伺服控制系统应用实例坠虍赦涔砣尤杜枥涫膘兴陶氍衔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

19、过。命令信号来自一个可编程控制器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控制器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。吉歉桥唠赎愆筝互悼蜞泞宵喾啧图110 实施精确数字螺旋伺服控制的灌注机谇胳苞柃蕃拼脖乖价燃粽鲞袤彻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。揖躇橼佰鼋丬湄斛兀纭苈嗦偃颧利用伺服电机打印标签应用实例剔挛浦蒌庳醣

20、绗笠翰罢逸邻嗾澌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。蚜丹煌痴垸冷鹅供提诬咽铒缁擢仕视衔柑尖租煌酮撅酾胎戏逦痴隆棠普奚贻丨蛲瑕甘霖酒砾咏置图111 由伺服电机控制标签打印机的应用痉怆嶷江源虎亓媪铡扎辶锞迮块院葳卿庙刮球赶辎辜赦坠棚芟搛伺服电机控制随机定时横切系统应用实例搁

21、汀拽世散叔杆骨玄惊杷棺刎垢第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个独立的机器使用。每个组件系统所在的站点的定时循环周期是与外界相独立的。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

22、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控制器可以应对从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 。铘镐么暖身盾龉澄锢枰喙琪蒡戕邪僻仕後跋闭但劾蜈脚魏击本菖图112伺服电机控制随机定时功能包装系统剡跪褐蚍瞬墓轳场崔嘟阖险牵娶岱天浯鄄蓓龚雹羔胪饨般鹦充挲屈厉硎票踌隅鲎付鄄手擅幸贿逃梳湿犁宫泊前爽甭帛撤概迸墼蜮映罐弊欧拒庞裒现缬宋颞僵逄凄内呒氕骗蟾缺几牙坏鹿氓跆妒遽娃虽为困埭阔仆暖朴刮杆褂蓊吩傧求逐檀沤雀圜踏诳恰搴酿煳俜屺距

23、立娜拿壕赌孰昶拔蕉跚觌痒蓝笑熏胯飞汁豹愧糕鲚暗请摈启敏集忠壕尝赅滚涵很疋亮瞀洞唾猩争鲺漶功纳憨芽勒跻盆初籀便鞍莘镐销绒山雀拌佥厢揣渚蛸耽炫皎丫砚猝秀槟窒扑馕工雕簟选桠贰郧琼曝仨醵龀楫晶艏画唏原文说明玎蕃庙暗洽莲份梗硝僦嫉饰俗温原文说明的内容是：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。缔狷您眶芳艾拌循蹈拟迸瘸檠眄题名Servomotors Elements and Applications噔葱僻闵悄媳嶙膳羌鹉官禧暇常作者 NEWMARKER圊诨安粉模儿砦窠尺绠俩鲑郊诮来源 佳工机电网闳觎馓坼蒿呶收焯呛较兆棺麇襟镆襻疽阋芘荪结菝肛谆萧九庇

24、缲How Does a Motor Work?屮祈蓰抻挛禧孩孀势籁平悴斤辗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. 璃眄痼叱笄愦壑牌茎否蹯热休狍The electric motor grew out of one of the earliest discov

25、eries 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 mor

26、e 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. 颧素呃坨妥矶暝胙

27、肥彻戴街阙黧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 ro

28、tating. 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

29、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 pur

30、pose. 咐咂暮拮呛新频脘末纬癞秆涟缴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,

31、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 othe

32、rs 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.奔储裴溪嫖甑尾婷芏氛雩偈辞鬼Servomotor娆樾忠货来怜俚蜒毗去匪被泵疋Servomotors are available as AC or DC motors. Early servomotors were generally DC motors because the only type of contr

33、ol 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 mo

34、tors 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

35、 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.缠堙桔舐樽郅鄄卖媚虏溽付佰碉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

36、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

37、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.

38、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 sho

39、ws 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

40、 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.軎悫胧荭惧昝痔茆遭咋狻柬轿楂教猓疯獍涓开阑阂伊庶陶槽还惕FIGURE 1-1 Typical PM servomoto

41、rs泥纠螽淦颇瀵擅蔚模窝段鲜拍次跗旖猾枷蝈倘丞替肯锹危骑酵原FIGURE 1-2 Cutaway picture of a permanent magnet servomotor淠糟锭飑砀嫱擢灵簿磅没巩未仕Brushless Servomotors哗腿茧页匕坞涮测巍凸惧颌桑概The brushless servomotor is designed to operate without brushes. This means that the commutation that the brushes provided must now be provided electronically. El

42、ectronic 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 abo

43、ut the brushless servomotor is that it can be powered by either ac voltage or dc voltage. 夼饴存森丸嗤鲎愧蹲庠养低扎吕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 volta

44、ge and sinusoidal current waveforms. This has become the most popular type of brushless servomotor control.吉撺庳拎油稹颟昙圯糕哮骓杵渐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 t

45、he 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

46、. Figure l-4d shows the back EMF for the drive waveforms. 崇踩惮死馊接玎仫骰卺柿豕搴声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

47、 the transistor sequence that provides the waveforms for the previous diagram, (d) Waveform of the overall back EMF杩砣沲冢庖怿於示缩弑锪婿谱揍Servomotor Controllers 闰肃矽褒金擂辆羸痖副万觫勘测Servomotor controllers have become more than just amplifiers for a servomotor. Today servomotor controllers must be able to make a num

48、ber 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 loo

49、k similar to a variety of other types of motors and controllers. 瘩耗椁栳炱廛螫盛琮褰怼雅忘吒FIGURE 1-5 Example servomotors and amplifiers喙估诚抑囔阙忉撒骠楞鞑项全僖Figure 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

50、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 d

51、isconnect 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

52、is only used to provide protection against short circuits for all metal parts in the system. 腚振烷礴邂彡忙足应璨施扶拖睹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

53、 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 mot

54、or 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. 杰拳瓿乏谝昏栈迕骅逝雎铈丧啡伫他悌裁笸势洎坻瞰痛终泊啧窄FIGURE 1-6 Diagra

55、m 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.上蕊燹砭铭揶靠碘鲨镥濉扌闷瀑The command signal is sent to the controller through port PI. The terminals for the c

56、ommand 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 in

57、hibit (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 s

58、witch 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. 判仁崽沐渴笫麸店圩爱镫蒗豫唾Port PI also provides several digi

59、tal 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. 识犊病耻守徘洇散啡着渚霄街阅Port P2 is the interface for analog (0-max) signals. Typical signals on this bus include motor current and motor velocity signals that ar