伺服电机
1.伺服电机的定义
伺服电动机又称执行电动机，在自动控制系统中，用作执行元件，把所收到的电信号转换成电动机轴上的角位移或角速度输出。分为直流和交流伺服电动机两大类，其主要特点是，当信号电压为零时无自转现象，转速随着转矩的增加而匀速下降。伺服电机在伺服系统中控制机械元件运转的发动机.是一种补助马达间接变速装置。伺服电机可使控制速度,位置精度非常准确。将电压信号转化为转矩和转速以驱动控制对象。转子转速受输入信号控制，并能快速反应，在自动控制系统中作执行元件，且具有机电时间常数小、线性度高、始动电压低等特点。
2.伺服电机工作原理
1.伺服主要靠脉冲来定位，基本上可以这样理解，伺服电机接收到1个脉冲，就会旋转1个脉冲对应的角度，从而实现位移，因为，伺服电机本身具备发出脉冲的功能，所以伺服电机每旋转一个角度，都会发出对应数量的脉冲，这样，和伺服电机接受的脉冲形成了呼应，或者叫闭环，如此一来，系统就会知道发了多少脉冲给伺服电机，同时又收了多少脉冲回来，这样，就能够很精确的控制电机的转动，从而实现精确的定位，可以达到0.001mm。有刷电机成本低，结构简单，启动转矩大，调速范围宽，控制容易，需要维护，但维护方便（换碳刷），产生电磁干扰，对环境有要求。无刷电机体积小，重量轻，出力大，响应快，速度高，惯量小，转动平滑，力矩稳定。控制复杂，容易实现智能化，其电子换相方式灵活，可以方波换相或正弦波换相。电机免维护，效率很高，运行温度低，电磁辐射很小，长寿命，可用于各种环境。
2.交流伺服电机也是无刷电机，分为同步和异步电机，目前运动控制中一般都用同步电机，它的功率范围大，可以做到很大的功率。大惯量，最高转动速度低，且随着功率增大而快速降低。因而适合做低速平稳运行的应用。
3.永磁交流伺服电动机简介
20世纪80年代以来，随着集成电路、电力电子技术和交流可变速驱动技术的发展，永磁交流伺服驱动技术有了突出的发展，各国著名电气厂商相继推出各自的交流伺服电动机和伺服驱动器系列产品并不断完善和更新。交流伺服系统已成为当代高性能伺服系统的主要发展方向，使原来的直流伺服面临被淘汰的危机。90年代以后，世界各国已经商品化了的交流伺服系统是采用全数字控制的正弦波电动机伺服驱动。交流伺服驱动装置在传动领域的发展日新月异。永磁交流伺服电动机同直流伺服电动机比较，主要优点有：⑴无电刷和换向器，因此工作可靠，对维护和保养要求低。⑵定子绕组散热比较方便。⑶惯量小，易于提高系统的快速性。⑷适应于高速大力矩工作状态。⑸同功率下有较小的体积和重量。自从德国MANNESMANN的Rexroth公司的Indramat分部在1978年汉诺威贸易博览会上正式推出MAC永磁交流伺服电动机和驱动系统，这标志着此种新一代交流伺服技术已进入实用化阶段。到20世纪80年代中后期，各公司都已有完整的系列产品。整个伺服装置市场都转向了交流系统。早期的模拟系统在诸如零漂、抗干扰、可靠性、精度和柔性等方面存在不足，尚不能完全满足运动控制的要求，近年来随着微处理器、新型数字信号处理器（DSP）的应用，出现了数字控制系统，控制部分可完全由软件进行，分别称为摪胧只瘮或抟旌鲜綌、撊只瘮的永磁交流伺服系统。到目前为止，高性能的电伺服系统大多采用永磁同步型交流伺服电动机，控制驱动器多采用快速、准确定位的全数字位置伺服系统。日本安川电机制作所推出的小型交流伺服电动机和驱动器，其中D系列适用于数控机床（最高转速为1000r/min，力矩为0.25～2.8N.m），R系列适用于机器人（最高转速为3000r/min，力矩为0.016～0.16N.m）。之后又推出M、F、S、H、C、G 六个系列。20世纪90年代先后推出了新的D系列和R系列。这样，只用了几年时间形成了八个系列（功率范围为0.05～6kW）较完整的体系，满足了工作机械、搬运机构、焊接机械人、装配机器人、电子部件、加工机械、印刷机、高速卷绕机、绕线机等的不同需要。以生产机床数控装置而著名的日本法那克（Fanuc）公司，在20世纪80年代中期也推出了S系列（13个规格）和L系列（5个规格）的永磁交流伺服电动机。L系列有较小的转动惯量和机械时间常数，适用于要求特别快速响应的位置伺服系统。日本其他厂商，例如：三菱电动机（HC-KFS、HC-MFS、HC-SFS、HC-RFS和HC-UFS系列）、东芝精机（SM系列）、大隈铁工所(BL系列）、三洋电气（BL系列）、立石电机（S系列）等众多厂商也进入了永磁交流伺服系统的竞争行列。美国著名的伺服装置生产公司Gettys曾一度作为Gould 电子公司一个分部（Motion Control Division），生产M600系列的交流伺服电动机和A600 系列的伺服驱动器。后合并到AEG，恢复了Gettys名称，推出A700全数字化的交流伺服系统。I.D.（Industrial Drives）是美国著名的科尔摩根（Kollmorgen）的工业驱动分部，曾生产BR-210、BR-310、BR-510 三个系列共41个规格的无刷伺服电动机和BDS3型伺服驱动器。自1989年起推出了全新系列设计的掺鹣盗袛（Goldline）永磁交流伺服电动机，包括B（小惯量）、M（中惯量）和EB（防爆型）三大类，有10、20、40、60、80五种机座号，每大类有42个规格，全部采用钕铁硼永磁材料，力矩范围为0.84～111.2N.m，功率范围为0.54～15.7kW。配套的驱动器有BDS4（模拟型）、BDS5（数字型、含位置控制）和Smart Drive（数字型）三个系列，最大连续电流55A。法国Alsthom集团在巴黎的Parvex工厂生产LC系列（长型）和GC系列（短型）交流伺服电动机共14个规格，并生产AXODYN系列驱动器。原苏联为数控机床和机器人伺服控制开发了两个系列的交流伺服电动机。其中ДBy系列采用铁氧体永磁，有两个机座号，每个机座号有3种铁心长度，各有两种绕组数据，共12个规格，连续力矩范围为7～35N.m。2ДBy系列采用稀土永磁，6个机座号17个规格，力矩范围为0.1～170N.m，配套的是3ДБ型控制器。近年日本松下公司推出的全数字型MINAS系列交流伺服系统，其中永磁交流伺服电动机有MSMA系列小惯量型，功率从0.03～5kW，共18种规格；中惯量型有MDMA、MGMA、MFMA三个系列，功率从0.75～4.5kW，共23种规格,MHMA系列大惯量电动机的功率范围从0.5～5kW，有7种规格。
伺服电机原理
1.交流伺服电动机
交流伺服电动机定子的构造基本上与电容分相式单相异步电动机相似.其定子上装有两个位置互差90°的绕组，一个是励磁绕组Rf，它始终接在交流电压Uf上；另一个是控制绕组L，联接控制信号电压Uc。所以交流伺服电动机又称两个伺服电动机。交流伺服电动机的转子通常做成鼠笼式，但为了使伺服电动机具有较宽的调速范围、线性的机械特性，无“自转”现象和快速响应的性能，它与普通电动机相比，应具有转子电阻大和转动惯量小这两个特点。目前应用较多的转子结构有两种形式：一种是采用高电阻率的导电材料做成的高电阻率导条的鼠笼转子，为了减小转子的转动惯量，转子做得细长；另一种是采用铝合金制成的空心杯形转子，杯壁很薄，仅0.2-0.3mm，为了减小磁路的磁阻，要在空心杯形转子内放置固定的内定子.空心杯形转子的转动惯量很小，反应迅速，而且运转平稳，因此被广泛采用。交流伺服电动机在没有控制电压时，定子内只有励磁绕组产生的脉动磁场，转子静止不动。当有控制电压时，定子内便产生一个旋转磁场，转子沿旋转磁场的方向旋转，在负载恒定的情况下，电动机的转速随控制电压的大小而变化，当控制电压的相位相反时，伺服电动机将反转。交流伺服电动机的工作原理与分相式单相异步电动机虽然相似，但前者的转子电阻比后者大得多，所以伺服电动机与单机异步电动机相比，有三个显著特点：1、起动转矩大 由于转子电阻大，与它可使临界转差率S0＞1，这样不仅使转矩特性（机械特性）更接近于线性，而且具有较大的起动转矩。因此，当定子一有控制电压，转子立即转动，即具有起动快、灵敏度高的特点。2、运行范围较广 3、无自转现象，正常运转的伺服电动机，只要失去控制电压，电机立即停止运转。当伺服电动机失去控制电压后，它处于单相运行状态，由于转子电阻大，定子中两个相反方向旋转的旋转磁场与转子作用所产生的两个转矩特性（T1－S1、T2－S2曲线）以及合成转矩特性（T－S曲线）交流伺服电动机的输出功率一般是0.1-100W。交流伺服电动机运行平稳、噪音小。但控制特性是非线性，并且由于转子电阻大，损耗大，效率低，因此与同容量直流伺服电动机相比，体积大、重量重，所以只适用于0.5-100W的小功率控制系统。
2.伺服电机选型方法
1.与步进电机的性能比较
步进电机作为一种开环控制的系统，和现代数字控制技术有着本质的联系。在目前国内的数字控制系统中，步进电机的应用十分广泛。随着全数字式交流伺服系统的出现，交流伺服电机也越来越多地应用于数字控制系统中。为了适应数字控制的发展趋势，运动控制系统中大多采用步进电机或全数字式交流伺服电机作为执行电动机。虽然两者在控制方式上相似（脉冲串和方向信号），但在使用性能和应用场合上存在着较大的差异。现就二者的使用性能作一比较。
一、控制精度不同：两相混合式步进电机步距角一般为 1.8°、0.9°，五相混合式步进电机步距角一般为0.72 °、0.36°。也有一些高性能的步进电机通过细分后步距角更小。如三洋公司（SANYO DENKI）生产的二相混合式步进电机其步距角可通过拨码开关设置为1.8°、0.9°、0.72°、0.36°、0.18°、0.09°、0.072°、0.036°，兼容了两相和五相混合式步进电机的步距角。 交流伺服电机的控制精度由电机轴后端的旋转编码器保证。以三洋全数字式交流伺服电机为例，对于带标准2000线编码器的电机而言，由于驱动器内部采用了四倍频技术，其脉冲当量为360°/8000=0.045°。对于带17位编码器的电机而言，驱动器每接收131072个脉冲电机转一圈，即其脉冲当量为360°/131072=0.0027466°，是步距角为1.8°的步进电机的脉冲当量的1/655。
二、低频特性不同，步进电机在低速时易出现低频振动现象。振动频率与负载情况和驱动器性能有关，一般认为振动频率为电机空载起跳频率的一半。这种由步进电机的工作原理所决定的低频振动现象对于机器的正常运转非常不利。当步进电机工作在低速时，一般应采用阻尼技术来克服低频振动现象，比如在电机上加阻尼器，或驱动器上采用细分技术等。交流伺服电机为恒力矩输出，即在其额定转速（一般为2000RPM或3000RPM）以内，都能输出额定转矩，在额定转速以上为恒功率输出。
三、过载能力不同 步进电机一般不具有过载能力。交流伺服电机具有较强的过载能力。以山洋交流伺服系统为例，它具有速度过载和转矩过载能力。其最大转矩为额定转矩的二到三倍，可用于克服惯性负载在启动瞬间的惯性力矩。步进电机因为没有这种过载能力，在选型时为了克服这种惯性力矩，往往需要选取较大转矩的电机，而机器在正常工作期间又不需要那么大的转矩，便出现了力矩浪费的现象。
四．运行性能不同步进电机的控制为开环控制，启动频率过高或负载过大易出现丢步或堵转的现象，停止时转速过高易出现过冲的现象，所以为保证其控制精度，应处理好升、降速问题。交流伺服驱动系统为闭环控制，驱动器可直接对电机编码器反馈信号进行采样，内部构成位置环和速度环，一般不会出现步进电机的丢步或过冲的现象，控制性能更为可靠。
五、2.选型计算方法
一、转速和编码器分辨率的确认。
二、电机轴上负载力矩的折算和加减速力矩的计算。
三、计算负载惯量，惯量的匹配，安川伺服电机为例，部分产品惯量匹配可达50倍，但实际越小越好，这样对精度和响应速度好。
四、再生电阻的计算和选择，对于伺服，一般2kw以上，要外配置。
五、电缆选择，编码器电缆双绞屏蔽的，对于安川伺服等日系产品绝对值编码器是6芯，增量式是4芯。
3.伺服电机安装注意事项
1、伺服电机油和水的保护 A：伺服电机可以用在会受水或油滴侵袭的场所，但是它不是全防水或防油的。因此，伺服电机不应当放置或使用在水中或油侵的环境中。B：如果伺服电机连接到一个减速齿轮，使用伺服电机时应当加油封，以防止减速齿轮的油进入伺服电机C：伺服电机的电缆不要浸没在油或水中。
2、伺服电机电缆→减轻应力 A：确保电缆不因外部弯曲力或自身重量而受到力矩或垂直负荷，尤其是在电缆出口处或连接处。B：在伺服电机移动的情况下，应把电缆（就是随电机配置的那根）牢固地固定到一个静止的部分（相对电机），并且应当用一个装在电缆支座里的附加电缆来延长它，这样弯曲应力可以减到最小。C：电缆的弯头半径做到尽可能大。
3、伺服电机允许的轴端负载 A：确保在安装和运转时加到伺服电机轴上的径向和轴向负载控制在每种型号的规定值以内。B：在安装一个刚性联轴器时要格外小心，特别是过度的弯曲负载可能导致轴端和轴承的损坏或磨损C：最好用柔性联轴器，以便使径向负载低于允许值，此物是专为高机械强度的伺服电机设计的。D：关于允许轴负载，请参阅“允许的轴负荷表”（使用说明书）。
4.直流伺服电机特点
一、直流无刷电机特点：
1.转动惯量小、启动电压低、空载电流小；
2.弃接触式换向系统，大大提高电机转速，最高转速高达100 000rpm；
3.无刷伺服电机在执行伺服控制时，无须编码器也可实现速度、位置、扭矩等的控制；
4.不存在电刷磨损情况，除转速高之外，还具有寿命长、噪音低、无电磁干扰等特点；
二、直流有刷伺服电机特点：
1.体积小、动作快反应快、过载能力大、调速范围宽；
2.低速力矩大, 波动小，运行平稳；
3..低噪音,高效率；
4.后端编码器反馈（选配）构成直流伺服等优点；
使用范围：直流伺服电机可应用在是火花机、机械手、精确的机器等。可同时配置2500P/R高分析度的标准编码器及测速器，更能加配减速箱、令机械设备带来可靠的准确性及高扭力。 调速性好，单位重量和体积下，输出功率最高，大于交流电机，更远远超过步进电机。多级结构的力矩波动小。
Servo motor
1. Servo motor definition
Also known as the implementation of the motor servo motor, the automatic control system for the implementation of components to convert signals received from the motor shaft angular displacement or angular velocity output.DC and AC servo motor is divided into two categories, the main feature is that when the signal voltage is zero, no rotation of the phenomenon, the increasing speed with uniform torque decreased.Servo motors to control mechanical servo system in the operation of the engine components. Is a servomotors device.Servo motor can control the speed, position accuracy is very accurate.The voltage signal into a torque and speed to drive the control object.Rotor speed by the input signal control, and can respond rapidly, in the automatic control system for the implementation of components, and has electrical and mechanical time constant, linear and high initiating voltage low.
2. Servo motor works
1. Servo mainly rely on impulse to locate, basically can be understood, the servo motor receives a pulse, a pulse will rotate the corresponding point of view, in order to achieve the displacement, because the servo motor itself has issued a pulse function, so the servoEach motor to rotate a point of view, is issued by the corresponding number of pulses, so that the pulse and servo motors to accept the formation of the echo, or called closed-loop, this way, the system will know the number of pulses sent to the servo motor, while the number of receivedpulse came back, so that we can very accurately control the motor rotation, in order to achieve accurate positioning, can reach 0.001mm.DC servo motor into brush and brushless motors.Brush motor low cost, simple structure, starting torque, wide speed range, easy control, need to maintain, but easy to maintain (replacement carbon brushes), generate electromagnetic interference, the environment requirements.So it can be used for cost-sensitive general industrial and civil applications.Brushless motor, small size, light weight, large output, fast response, high speed, small inertia, rotational smoothness, torque and stability.Control complex, easy to implement intelligent, flexible way of their electronic commutation, the commutation can be square wave or sinusoidal commutation.Motor maintenance-free, high efficiency, low operating temperature, electromagnetic radiation is very small, long-life, can be used for a variety of environments.
2. Brushless AC servo motor is divided into synchronous and asynchronous motors, motion control in the current synchronous motor is generally used, and its power range, can do a lot of power.Large inertia, the maximum rotation speed is low, and with the power increases rapidly decreased.Thus suitable for applications that run on low speed steady.
3. Servo motor rotor is permanent magnet, the drive control of the U / V / W three-phase power to form fields, the rotor in the magnetic field under the rotation, while the motor comes with encoder feedback signal to the drive, the drive according to the feedback valuecompared with the target value, adjusting the angle of the rotor rotation.Depends on the accuracy of the servo motor encoder accuracy (lines).
Question:
AC servo motors and brushless DC servo motor function, what is the difference?
A: AC servo better because a sine wave control, torque ripple small.DC servo is a trapezoidal wave.But the DC servo is relatively simple, cheap.
3. Introduction permanent magnet AC servo motor
80 years since the 20th century, with the integrated circuits, power electronics and AC variable speed drive technology, permanent magnet AC servo drive technology with outstanding development, national electrical manufacturers have launched their own well-known AC servo motor and servo drive seriesand continue to improve and update products.AC servo system has become a contemporary high-performance servo systems the main development direction, so that the original DC servo facing the crisis of being eliminated.90 years later, the world has been commercialized by AC servo digital control system is a sine wave motor servo drive.AC servo drive the rapid development of the field in the transmission.Permanent magnet AC servo motor compared with DC servo motor, the main advantages are: ⑴ without brush and commutator, it is reliable and maintenance requirements for maintenance and low.⑵ cooling the stator winding more convenient.⑶ inertia is small, easy-to improve the system fast.⑷ adapted to high-speed high torque working condition.⑸ under the same power, smaller size and weight.Since the German MANNESMANN of Rexroth Indramat division in the company's Hanover Trade Fair 1978 was officially launched MAC permanent magnet AC servo motor and drive system, which marks this new generation of AC servo technology has entered the practical stage.To the late 20th century, 80 years, the company has a complete line of products.The servo-device market are turning to the exchange system.Early analog systems such as zero-drift, interference, reliability, accuracy and flexibility in areas such as lack of motion control is still not fully meet the requirements, in recent years with the microprocessor, the new digital signal processor (DSP) applicationsthe emergence of digital control system, the control section can be carried out entirely by the software, called Jiang hazy or Tuan Shen Jing only fresh coarse hempen fabric, valiant only Shen of the permanent magnet AC servo system.So far, high-performance servo systems mostly use electrical permanent magnet synchronous AC servo motor, control the drive to use more fast, accurate positioning of the all-digital servo system.Typical manufacturers such as Siemens of Germany, the United States and Japan Kollmorgen companies such as Panasonic and Yaskawa.Yaskawa Electric has launched a small-scale production of AC servo motors and drives, in which D series for CNC machine tools (maximum speed of 1000r/min, torque is 0.25 ~ 2.8Nm), R series is suitable for the robot (the highest speed of 3000r/min, torque is 0.016 ~ 0.16Nm).Launched after the M, F, S, H, C, G six series.90 20th century, has introduced a new D-series and R series.Rectangular wave drive from the old series, 8051 to control the sine wave drive, 80C, 154CPU and gate array chip control, torque ripple from 24% to 7%, and improved reliability.Thus, the formation of only a few years, eight series (power range of 0.05 ~ 6kW) more complete system to meet the working machinery, transportation agencies, welding robots, assembly robots, electronic components, processing machinery, printing presses, high speed winding machine, winding machines for different needs.CNC equipment to produce the famous Japanese law that g (Fanuc) company, in the 20th century has introduced the mid-80s S series (13 specifications), and L series (5 specifications) of the permanent magnet AC servo motor.L Series has a smaller moment of inertia and the mechanical time constant, particularly for applications that require fast response servo system.Other Japanese manufacturers, such as: Mitsubishi Motors (HC-KFS, HC-MFS, HC-SFS, HC-RFS and HC-UFS series), Toshiba Seiki (SM series), Okuma Iron Works (BL series), Sanyo Electric(BL series), standing stones motor (S series) and many other manufacturers have entered the permanent magnet AC servo system fray.Germany Rexroth (Rexroth) The MAC Indramat Division Series AC servo motor Total 7 Frame 92 specifications.Germany's Siemens (Siemens)'s IFT5 series three-phase permanent magnet AC servo motor standard and short form is divided into two categories, a total of 98 species of 8 frame size specifications.Allegedly the same series AC servo motor and DC servo motor output torque compared IHU series, which weighs only 1 / 2, supporting the transistor PWM drive 6SC61 series, the most for 6-axis motor control.Bosch (BOSCH) ferrite magnets produced the SD series (17 standard) and rare earth permanent magnet of the SE series (8 specs) AC servo motor and drive controller Servodyn SM series.American production companies Gettys servo device as Gould Electronics, once a division of (Motion Control Division), production of M600 series A600 series AC servo motor and servo drives.After the merger to the AEG, Gettys name restored, the introduction of A700 all-digital AC servo system.U.S. AB (ALLEN-BRADLEY) 1326-based production company driver division ferrite permanent magnet AC servo motor and servo controller PWM AC 1391.Frame size motors including 3 of 30 specifications.ID (Industrial Drives) is a famous Cole Morgan (Kollmorgen) of industrial drives division, has produced BR-210, BR-310, BR-510 a total of 41 specifications of the three series of brushless servo motor and servo BDS3drive.Since 1989, launched a new series designed solely doped Jian Pirates (Goldline) permanent magnet AC servo motor, including the B (small inertia), M (Middle Inertia) and EB (explosion proof) three categories, 10,20,40,60,80 five frame sizes, each of 42 categories of specifications, all using NdFeB permanent magnet, torque range of 0.84 ~ 111.2Nm, a power range of 0.54 ~ 15.7kW.Supporting the drive has BDS4 (analog), BDS5 (digital type, with position control) and the Smart Drive (digital type) of three series, the maximum continuous current of 55A.Goldline Series represents contemporary art in permanent magnet AC servo technology.Ireland's Inland formerly a division of Kollmorgen abroad, now merged into the AEG, the production of DC servo motors, DC torque motor and servo amplifier is known.Production BHT1100, 2200,3300 three frame sizes of 17 kinds of specifications of SmCo permanent magnet AC servo motor and eight controllers.French Alsthom Group factory in Paris Parvex LC series (long form) and GC series (short) 14 AC servo motor specifications, and production AXODYN series of drives.The former Soviet Union for the CNC machine tools and robots servo control developed two series of AC servo motor.One ДBy series uses ferrite magnets, there are two frame sizes, frame sizes are 3 for each core length, each with two winding data, a total of 12 specifications, a continuous torque range of 7 ~ 35N.m.2ДBy series uses rare earth permanent magnet, 6 frame size 17 specifications, the torque range is 0.1 ~ 170N.m, supporting the 3ДБ controller.In recent years, Panasonic has introduced the all-digital AC servo system based MINAS series, in which permanent magnet AC servo motor with MSMA series of small inertia-type, power from 0.03 ~ 5kW, a total of 18 kinds of specifications; the inertia type with MDMA, MGMA, MFMA threeseries, the power from 0.75 ~ 4.5kW, 23 kinds of specifications, MHMA series of large inertia motor power range from 0.5 ~ 5kW, 7 kinds of specifications.Samsung developed in recent years, all-digital AC servo motor and drive system, which FAGA AC servo motor series of CSM, CSMG, CSMZ, CSMD, CSMF, CSMS, CSMH, CSMN, CSMX a variety of models, the power from 15W ~ 5kW.Now often used (Powerrate) This comprehensive index as the servo motor quality factor, measuring a variety of AC and DC servo motor contrast and dynamic response performance stepper motor.Continuous motor power, said the rate of change (rated) torque and rotor inertia ratio.Change rate is calculated by power analysis, the permanent magnet AC servo motor technology indicators for the United States ID, Goldline Series is the best, followed by Germany's Siemens in IFT5 series.
Principle of the servo motor
1. AC servo motor
AC servo motor stator phase structure is essentially single-phase capacitor induction motor similar. The stator is equipped with 90 ° difference between the two locations each winding, one field winding Rf, it is always connected to the AC voltage Uf; anotheris the control winding L, link control signal voltage Uc.Therefore, the two AC servo motor servo motors, also known as.AC servo motors are usually made of squirrel-cage rotor, but in order to make the servo motor has a wide speed range, the mechanical properties of the linear, no "rotation" phenomenon and the rapid response of the performance, it is compared with ordinary motor should bewith the rotor resistance and a small moment of inertia of these two characteristics.Rotor structure is currently used more often in two forms: one is the use of high resistivity conductive material made of high resistivity conducting bar of squirrel cage rotor, in order to reduce the rotational inertia of the rotor, rotor do slender; otherOne is made of aluminum alloy hollow cup-shaped rotor, Beibi thin, only 0.2-0.3mm, in order to reduce the reluctance of magnetic circuit, to be placed inside the hollow cup-shaped rotor fixed stator. hollow cupRotor moment of inertia is small, responsive, and smooth operation, so it is widely used.AC servo motor in the absence of control voltage, the stator field windings, only the magnetic field pulse generated by the rotor stationary.When a control voltage, the stator generates a rotating magnetic field, rotating magnetic field along the direction of the rotor rotation, in the case of constant load, the motor speed with the size of the control voltage changes, when the control voltage of the opposite phase, the servo motorwill be reversed.The working principle of AC servo motor with split phase single phase induction motor although similar, but the former is much greater than the latter of rotor resistance, so the induction motor servo motor, compared with stand-alone, there are three significant features: 1, high starting torqueAs a large rotor resistance, the torque curve shown in Figure 3, curve 1, with ordinary asynchronous motor torque curve than 2, a marked difference.It will enable the critical slip S0> 1, so that not only the torque characteristics (mechanical properties) is closer to linear, and has a larger starting torque.Therefore, when one has control of stator voltage, rotor turning once, that has a quick start, high sensitivity.2, 3, wide operating range, no rotation of the phenomenon, the normal operation of the servo motor, as long as the loss of control voltage, the motor stop running.When the voltage of the servo motor control is lost, it is running single-phase, due to a large rotor resistance, stator rotating in the opposite direction of the role of rotating magnetic field generated by the rotor torque characteristics of the two (T1-S1, T2-S2 curves) and the synthesis of torque characteristics (T-S curve) AC servo motor output power is generally 0.1-100W.When the power frequency is 50Hz, voltage 36V, 110V, 220,380 V; when the power frequency is 400Hz, voltage 20V, 26V, 36V, 115V and other.AC servo motor to run smoothly, low noise.However, non-linear control characteristics, and because a large rotor resistance, loss, low efficiency, and is therefore compared with the capacity of DC servo motor, bulky, heavy weight, it applies only to a small 0.5-100W power control system.
2. Servo motor selection method
1. And compare the performance of the stepper motor
As an open-loop stepper motor control system, and modern digital control technology are intrinsically linked.In the current domestic digital control system, the stepper motor is widely used.With the all-digital AC servo-systems, AC servo motor also increasingly used in digital control systems.In order to meet the development trend of digital control, motion control systems they use digital stepper motors or AC servo motor as the implementation of the motor.While both are similar in the control (pulse train and direction signal), but in applications where performance and there are big differences.Performance of both is to make a comparison.
Control accuracy are different: two-phase hybrid step motor step angle is generally 1.8 °, 0.9 °, five-phase hybrid stepping motor step angle is usually 0.72 °, 0.36 °.There are also some high-performance stepper motor through after the breakdown of a smaller step angle.Such as Sanyo (SANYO DENKI) production of two-phase hybrid step motor step angle by its DIP switch is set to 1.8 °, 0.9 °, 0.72 °, 0.36 °, 0.18 °, 0.09 °, 0.072 °, 0.036 °compatible with the two-phase and five-phase hybrid stepping motor step angle.Precision AC servo motor control back from the motor shaft rotary encoder guarantee.To Sanyo all-digital AC servo motor, for example, the standard for the 2000 line encoder with the motor, since the internal drive, four-frequency technology using a pulse equivalent to 360 ° / 8000 = 0.045 °.For the encoder with the motor 17, the driver receives 131 072 pulses per motor revolution, that is, a pulse equivalent to 360 ° / 131072 = 0.0027466 °, a step angle of 1.8 ° stepper motor pulse equivalent1 / 655.
Different frequency characteristics, the stepper motor at low speeds prone to low frequency vibration.Vibration frequency and load conditions and drive performance, generally considered no-load off the motor frequency half the frequency.This works by the stepper motor vibration frequency determined by the normal operation of the machine is very negative.When the stepper motor in low speed, generally should be used to overcome the low frequency vibration damping phenomena, such as additional damper on the motor, or drive with subdivision techniques.AC servo motor is running very smoothly, even if it does not appear in the low-speed vibration.AC servo system with resonance suppression, can cover the lack of mechanical stiffness, and function within the system has a frequency analysis (FFT), can detect mechanical resonance point, easy system tuning.
The different torque-frequency characteristics, the stepper motor output torque decreases with speed increases, and at higher speeds would drop dramatically, so its maximum operating speed is generally at 300 ~ 600RPM.AC servo motor for constant torque output, which in its rated speed (typically 2000RPM or 3000RPM) or less, can output rated torque above the rated speed constant power output.Fourth, generally do not overload with various stepper motor overload.AC servo motor with a strong overload.AC servo system to Sanyo, for example, it has the speed and torque overload overload.Its maximum torque is two to three times the rated torque can be used to overcome the inertia of the load moment of inertia at the start moment.Stepper motor because there is no such overload, in the selection order to overcome this moment of inertia, often need to select a larger motor torque, while the machine during normal operation and does not require so much torque, giving rise to a torquewasting phenomenon.
Five different operating performance stepper motor control for the open-loop control, start frequency is too high or too prone to lose the load step or the phenomenon of stall, stop rotating speed is too high when the phenomenon prone to overshoot, so as to ensure their controlaccuracy, should handle up, spin-down problem.AC servo drive system for closed loop control, the drive can be directly on the motor encoder feedback signal is sampled, the internal structure of the position loop and speed loop, generally will not be lost step or stepper motor overshoot phenomenon, the control performance more reliable.Six-speed response performance of different stepper motors to accelerate from standstill to operating speed (typically several hundred per minute, rpm) 200 ~ 400 ms.AC servo system is better acceleration performance to Sanyo 400W AC servo motor, for example, accelerates from zero to its rated speed of 3000RPM is only a few milliseconds, fast start and stop can be used to control the situation requires.In summary, the AC servo system is superior in many performance stepper motor.But in some less demanding situations are often to do with the implementation of the stepper motor motor.Therefore, the control system design process control requirements to be taken into account, costs, and many other factors, the choice of the appropriate motor control.
2. Selection method
First, the speed and encoder resolution of confirmation.
Second, the motor shaft load torque conversion and processing gear torque calculations.
Third, calculate the load inertia, inertia of the match, Yaskawa servo motors, for example, some products match up to 50 times the inertia, but the actual smaller the better, so good on the accuracy and response speed.
Fourth, the calculation of resistance and choice of regeneration, for the server, usually more than 2kw to external configuration.
Fifth, cable selection, the encoder cable shielded twisted pair, and for other Japanese Yaskawa servo system product is 6-cell absolute encoder, incremental is 4 core.
3. Servo Motor Installation Notes
1, the servo motor oil and water conservation A: servo motor can be used in water or oil droplets will be affected by the invasion of the place, but it is not fully waterproof or anti-oil.Therefore, the servo motor should not be placed or used in water or oil intrusion in the environment.B: If the servo motor connected to a reduction gear, use the servo motor fuel should be sealed to prevent the reduction gear oil into the servo motor C: servo motor cable not immersed in oil or water.
2, servo motor cable to reduce stress → A: Make sure the cable is not due to external bending moment, or by their own weight or vertical load, especially in the cable outlet or connection.B: In the case of the servo motor moves, should the cable (that is configured with the motor Flanagan) is firmly fixed to a stationary part of the (relative motor), and should be installed in the cable with a bearing in the attached cables to extendit, so the bending stress can be minimized .C: cable bend radius be as large as possible.
3, the servo motor allows the shaft load A: make sure when you add in the installation and operation of the servo motor shaft in radial and axial load control within the specified value for each model.B: When installing a rigid coupling to be cautious, especially over the curved shaft and bearing load may cause damage or wear C: best to use a flexible coupling, so that the radial load below the allowable value,This material is designed for high mechanical strength of the servo motor design.D: axial load on the permit, please refer to the "permissible axle load table" (Manual).
4, the servo motor is installed Note A: In the install / remove components to the servo motor shaft coupling, do not directly tap with a hammer shaft.(Direct beat hammer shaft, the other side of the servo motor shaft encoder to be knocked bad) B: strive to align the shaft to the best state (on a bad vibration or bearing damage may result.)
4. DC servo motor characteristics
First, the DC brushless motor features:
1. A small moment of inertia, low starting voltage, load current is small;
2. Disposable contact change to the system, greatly improving the motor speed, maximum speed up to 100 000rpm;
3. Brushless servo motor servo control in the implementation, the encoder can also be achieved without the speed, position, torque control;
4. There is no brush wear, in addition to high speed, but also has a long life, low noise, electromagnetic interference and other characteristics;
Second, the DC brush servo motor characteristics:
1. The volume is small, the fast response quick, overloading capacity, wide speed range;
2. Low-speed torque, and fluctuations in small, smooth;
3 .. low noise, high efficiency;
4. Backend encoder feedback (optional) constitute the advantages of the DC servo;
Use: DC servo motor can be used in a spark machine, robot, precise machinery.Can also configure the 2500P / R analysis of the degree of high standard encoder and tachometer, with gear box plus more, so that the accuracy of machinery and equipment to bring reliable and high torque.Speed is good, unit weight and volume, the output power of the highest, more than AC motors, and much higher than the stepper motor.Multi-level structure of the torque ripple small.
