《自动化专业英语课程第二版翻译.doc》由会员分享，可在线阅读，更多相关《自动化专业英语课程第二版翻译.doc（9页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、,Closed-loop Control of DC Drivers直流传动的闭环控制A basic scheme of closed-loop speed control system employing current limit control, also known as parallel current control, is shown in Fig.1-5b-1. m*sets the speed reference. A signal proportional to the motor speed is obtained from the speed is obtained f
2、rom the sped sensor. 应用限流控制，也称为并联电流控制的闭环速度控制系统的基本示意图如图1-5B-1所示。m* 为速度参考值。正比于电机速度的信号可从速度传感器获得。The speed sensor output is filtered to remove the AC ripple and compared with the speed reference. The speed error is processed through a speed controller. The output of the speed controller Uc adjusts the r
3、ectifier firing angle a to make the actual speed close to the reference speed. 速度传感器的输出滤除交流波，并与速度参考值比较，速度误差被速度控制器处理，速度控制器的输出uc 调整整流器的触发角，以使实际的速度接近于参考速度。The speed controller is usually a PI(proportional and integral ) controller and serves three purpose-stabilizes the drive and adjusts the damping ra
4、tio at the desired valued, makes the steady-state speed-error close to zero by integral action, and filters out noise again due to the integral action.速度控制器通常是PI (比例积分)控制器，具有三种作用 稳定驱动，调整阻尼比到期望值；通过积分作用，使稳态速度误差接近于零；还是由于积分作用，可滤除噪音 The drive employs current limit control, the purpose of which is to prev
5、ent the current from exceeding safe values. As long as IaIx, where Ix is the maximum permissible value of Ia, the current control loop does not affect the drive operation. 传动装置采用限流控制，其目的在于防止电流超出安全值。只要IAIx，其Ix 是IA 的最大允许值，电流控制回路并不影响驱动。If Ia exceeds Ix, even by a small amount, a large output signal is
6、produced by the threshold circuit, the current control overrides the speed control, and the speed error is corrected essentially at a constant current equal to the maximum permissible value. 如果 IA 超出 Ix，哪0怕一点点，阈值电路也会产生一个大的输出信号，电流环代替速度环起主要调节作用，电枢电流等于电机所允许的最大电流，并在此恒定电流下对速度误差进行调整。When the speed reaches
7、 close to the desired valued. When the speed reaches close to the desired value, Ia falls below Ix, the current control goes out of action and speed control takes over. Thus in this scheme, at any given time the operation of the drive is mainly controlled either by the speed control loop or the curr
8、ent control loop, and hence it is also called parallel current control.当速度接近于期望值时，IA 下降到Ix以下， 电流控制失效，速度控制接替。因此，在此示意图中，在任意给定时间，传动装置主要由速度控制回路或电流控制回路控制，所以，也叫并联电流控制。Another scheme of close-loop speed control is show in Fig.5B-2. It employs an inner current control loop within an outer speed loop. The ou
9、t of the speed controller e is applied to a current controller u adjusts the converter firing angle such that the actual speed is brought to a value set by speed commandm*.闭环速度控制的另一种示意图如图1-5B-2所示。 在外环速度回路中采用内环电流控制回路。速度控制器的输出ec 用于电流控制器，为内环电流控制回路设置电流参考值Ia* 。电流控制器的输出uc 调整逆变器的触发角，以便使实际速度达到速度给定值m*所设置的值。A
10、ny positive speed error, caused by either an increase in the speed command or an increase in the load torque, produce a higher current reference I*.The motor accelerates due to an increase in Ia, to correct the speed error and finally settles at a new Ia* which makes the motor torque equal to the lo
11、ad torque and the speed error close to zero.由速度给定或负载转矩的增加所引起的任何正的速度偏差，都会产生更大的参考电流值Ia* 。由于Ia 增加，电机加速，以调整速度误差，最终停留在新的Ia*值上，使电机转矩与负载转矩相同，速度误差接近于零。For any large positive speed error, the current limiter saturate and the current reference Ia*,is limited to a value Iam*,and the drive current not allowed t
12、o exceed the maximum permissible value. The speed error is corrected at the maximum permissible armature current until the speed error becomes small and the current limiter comes out of saturation .Now the speed error is corrected with Ia less than the permissible value.对于任何大的正的速度误差，限流装置饱和，且电流参考值Ia*
13、 限制为Iam*，传动装置的电流不允许超过最大允许值。在最大允许电枢电流下纠正速度误差，直到速度偏差减小且限流装置退出饱和状态。现在，速度误差在Ia小于最大允许电流值的情况下进纠正。A negative speed error will set the correct reference Ia* at a negative value .Since the motors current cannot reverse, a negative Ia* is of no use. It will however ”charge” the PI controller. When the speed e
14、rror becomes positive the “charge” PI controller will take a longer time to respond, causing unnecessary delay in the control action. The current limiter is therefore arranged to set a zero-current reference for negative speed error.负的速度误差将设置负的电流参考值Ia* 。因为电机电流不能反向，负的Ia*是没用的。然而，它将“掌管”PI控制器。当速度误差变正时，“
15、被掌管”的PI控制器将花费较长时间响应，造成控制中不必要的延迟。因此，对于负的速度误差，限流器的电流给定值被设为零。 Since the speed control loop and the current control loop are in cascade, the inner current control is also known an cascade control. It is also called current guided control. It is more commonly used than the current limit control because o
16、f the following advantages.因为速度控制回路和电流控制回路串联，因此内环电流控制也被称为串联控制。整体也被称为电流操纵控制。由于具有如下优势，其应用比限流控制更为普遍：1. It provides faster response to any supply voltage disturbance .The can be explained by considering the response of two drives to a decrease in the supply voltage .A decrease in the supply voltage redu
17、ce the motor current and torque .In the current-limiter control, the speed falls became the motor torque is less than the load torque that has not changed. The resulting speed error is brought to the original value by setting the rectifier firing angle at a lower value. 1. 对于任何电源电压扰动，提供更快的响应。这可通过考虑两
18、个传动装置对于电源电压降低的响应来解释。电源电压的降低将减少电机电流和转矩。在限流控制中，由于电机转矩小于未改变的负载转矩，速度下降，造成的速度误差通过设置较小的整流器触发角达到原值。In the case of inner current control, the decrease in motor current, due to the decrease in the supply voltage, produces a current error which changes the rectifier firing angle to bring the armature current
19、back to the original value. The transient response is now governed by the electrical time constant of the motor. Since the electrical time constant of a drive is much smaller compared to the mechanical time constant, the inner current control provides a faster response to the supply voltage disturba
20、nces. 在内环电流控制的情况下，由于电源电压的降低，电机电流的减少将产生电流误差，改变整流器的触发角，使电枢电流返回到原值。现在，暂态响应由电机的电时间常数控制，因为与机械时间常数相比，传动装置的电时间常数要小的多，所以对于电源电压扰动，内环电流控制将提供较快的响应。 2. For certain firing schemes, the rectifier and the control circuit together have a constant gain under continuous conduction. The drive is designed for this gain
21、 to set the damping ratio at 0.707, which gives an overshoot of 5 percent. Under discontinuous conduction, the gain reduces. The higher the reduction is in the conduction angel, the greater the reduction is in the gain.2. 对于确定的触发形式，整流器和控制电路一起在连续导电下，具有恒定增益。为此增益而设计的传动装置设置的阻尼比为0.707，给出了百分之五的超调量。在不连续导电的
22、情况下，增益下降。导电角减少越多，增益下降越大。The drive response becomes sluggish in discontinuous conduction and progressively deteriorates as the conduction angle reduces. If an attempt is made to design the drive for discontinuous conduction operation, the drive is likely to be oscillatory or even unstable for continu
23、ous conduction. The inner current control loop provides a close loop around the rectifier and the control circuit, and therefore, the variation of their gain has much less affect on the drive performance. Hence the transient response of the drive with the inner current loop is superior to that with
24、the current-limit control.在不连续导电的情况下，传动装置响应缓慢，当导电角减小时，响应日益恶化。如果企图设计应用于不连续导电操作的传动装置，那么此传动装置可能对于连续导电都是振荡的，甚至是不稳定的。内环电流控制回路提供了一个具有整流器和控制电路的闭环，所以增益的变化对于传动装置的性能影响较小。因此，带有内环电流回路的传动装置的暂态响应优于限流控制。3. In the current-limit control, the current must first exceed the permissible value before the current-limit ac
25、tion can be initiated. Since the firing angle can be changed only at discrete intervals, substantial current overshoot can occur before the current limiting becomes effective.3. 限流控制中，在限流开始作用前，电流首先必须超过允许值。因为触发角只有在离散的间隔中才可改变，所以只有在限流有效前，实际的电流超调才会发生。Small motors are more tolerant to high transient curr
26、ent. Therefore, to obtain a fast transient response, much higher transient currents are allowed by selecting a larger size rectifier. The current regulation is then needed only for abnormal values of current. In such cases because of the simplicity, current-limit control is employed.小电机更能承受大的暂态电流，因此
27、，为获得快速的暂态响应，通过选择较大尺寸的整流器, 即可允许出现更大的暂态电流。只有当电流值反常时，才会需要电流调节。在这样的情况下，由于简化，限流控制被应用。Both the schemes have different response for the increase and decrease in the speed command. A decrease in speed command at the most can make the motor torque zero; it cannot be reversed as braking is not possible. The d
28、rive decelerates mainly due to the load torque. When load torque is low, the response to a decrease in the speed command will be slow. These drives are therefore suitable for applications with large load torque, such as paper and printing machines, pumps, and blowers.这两种形式对速度给定的增与降有不同的响应。速度给定的减少至多可使电机转矩为零；由于不可能制动，所以转矩不能反向。传动装置减速主要是由于负载转矩，当负载转矩很小时，对速度给定减少的响应将很慢，因此，这些传动装置适合带有大的负载转矩的应用场合，例如纸张打印机、泵和吹风机。