FIGURE 11-90 Appli-cation of a servomotor controlling the speed of material as it enters a press for cutting pieces to size.
11.11.8.1 An Example of a Servo Controlled In-Line Bottle-Filling Application
A second application is shown in Fig. 11-91. In this application multiple filling heads line up with bottles as they move along a continuous line. Each of the filling heads must match up with a bottle and track the bottle while it is moving. Product is dispensed as the nozzles move with the bottles. In this application 10 nozzles are mounted on a carriage that is driven by a ball-screw mechanism. The ball-screw mechanism is also called a lead screw. When the motor turns the shaft of the ball screw, the carriage will move horizontally along the length of the ball-screw shaft. This movement will be smooth so that each of the nozzles can dis-pense product into the bottles with little spillage.
The servo drive system utilizes a positioning drive controller with software that allows the position and velocity to be tracked as the conveyor line moves the bottles. A master encoder tracks the bottles as they move along the conveyor line. An auger feed system is also used just prior to the point where the bottles enter the filling station. The auger causes a specific amount of space to be set between each bottle as it enters the filling station. The bottles may be packed tightly as they approach the auger, but as they pass through the auger their space is set exactly so that the necks of the bottles will match the spacing of the filling nozzles. A detector is also in conjunction with the dispensing system to ensure that no product is dispensed from a nozzle if a bottle is missing or large spaces appear between bottles.
FIGURE 11-91 Applica tion of a beverage-filling station controlled by a servomotor. The servo drive system compares the position of the bottles from the master encoder to the feedback signal that indicates the position of the filling carriage that is mounted to the ball screw. The servo drive amplifier will increase or decrease the speed of the ball-screw mechanism so that the nozzles will match the speed of the bottles exactly.
11.11.8.2 An Example of a Servo Controlled Precision Auger Filling System
A third application for a servo system is provided in Fig. 11-92. In this application a large filling tank is used to fill containers as they pass along a conveyor line. The material that is dispensed into the containers can be a single material fill or it can be one of several mate-rials added to a container that is dumped into a mixer for a blending operation. Since the amount of material that is dispensed into the container must be accurately weighed and metered into the box, an auger that is controlled by a servo system is used. The feedback sensor for this system can be a weighing system such as the load cell discussed in earlier chapters. The command signal can come from a programmable controller or the operator can enter it manually by selecting a recipe from the operator's terminal. The amount of ma-terial can be different from recipe to recipe.
FIGURE 11-92 Applica-tion of a precision auger filling station controlled by a servomotor. The speed of the auger can be adjusted so that it runs at high speed when the con-tainer is first being filled, and the speed can be slowed to a point where the final grams of material can be metered precisely as the container is filled to the proper point. As the price of material increases, precision filling equipment can provide savings as well as quality in the amount of product used in the recipe.
11.11.8.3 An Example of a Label Application Using Servomotors
The fourth appli-cation has a servomotor controlling the speed of a label-feed mechanism that pulls preprinted labels from a roll and applies them to packages as they move on a continuous conveyor system past the labeling mechanism. The feedback signals are provided by an encoder that indicates the location of the conveyor, tach generator that indicates the speed of the conveyor, and a sensor that indicates the registration mark on each label. The servo positioning system is controlled by a microprocessor that sets the error signal, and the servo amplifier that provides power signals to the servomotor. This application is shown in Fig. 11-93.
11.11.8.4 An Example of a Random Timing Infeed System Controlled by a Servomotor The fifth application is presented in Fig. 11-94, and it shows a series of packaging equipment that operates as three separate machines. The timing cycle of each station of the packaging system is independent from the others. The packaging system consists of an infeed conveyor, a positioning conveyor, and a wrapping station. The infeed conveyor and the wrapping station are mechanically connected so that they run at the same speed. The position of the packages on the wrapping station
must be strictly controlled so that the packages do not become too close to each other. A piece of metal called a flight is con-nected to the wrapping station conveyor at specific points to ensure each package stays in position. A sensor is mounted at the beginning of the positioning conveyor to determine the front edge of the package when it starts to move onto the positioning conveyor. A second sensor is positioned at the bottom of the packaging conveyor to detect the flights. Both of these signals from the sensors are sent to the servomotor to provide information so the servo can adjust the speed of the positioning conveyor so that each package aligns with one of the flights as it moves onto the packaging conveyor. This application shows that the servo positioning controller can handle a variety of different signals from more than one sensor because the controller uses a microprocessor.
FIGURE 11-93 Example of a labeling application controlled by a servomo-tor.
FIGURE 11-94 Example of a packaging system with random timing func-tions controlled by a
servo-motor.
AC交流电机的发展和类型
电机发明的早期都是被应用在工业方面的领域。最早以直流（DC）电机应用的范围最广，其中以60年代至80年代中期使用最为旺盛，但其因碳刷的关系所产生的种种问题至今一直存在，所以在1980年代中期以后，传统直流电机即渐渐被淘汰，取而代之的是AC电机。
从传统AC电机的模拟控制进化到现今数字控制电机的出现，各种电机的技术不断演化、改进，至目前为止，AC电机在现阶段，仍为工业动力上使用最为普遍的电机类型。
AC电机的种类
AC电机的种类非常多，如依其用途来做区分，大致可分为以下3种类型： 1.动力用电机
2.定位控制用（具剎车机能）电机 3.速度控制用电机
以下，我们将针对第一项、也是目前市面上使用最普遍的AC动力用电机作介绍。
所谓的动力用电机，也就是以动力的方式，来取代传统人工的搬运，进而达到物体运送的目的，特别是在只须单纯搬运、不需其它特殊动作要求的场合下，选用动力电机最为恰当。
依据使用、应用场合的不同，AC动力用电机又可分为以下几种： ■感应电机
为AC小型电机最具代表性的机种。 特性：
? 单一方向运转用（不可做瞬间逆转的切换，须待电机完全停止后才
能作逆转切换的动作。） ? 连续定格
? 过转量约30-40回转
目前市面上常见的有电容运转型单相110V/220V电机和三相220V电机3种，主要适合单一方向连续运转的场合，如：一般单纯的搬运动作。
■可逆电机 特性：
? 频繁正逆转及瞬间起动、停止用 ? 30分钟定格