Automatic Control Specialty English

一、专业词汇

（一）基础概念

自动控制（Automatic control）：The process of using control systems to operate equipment or processes without direct human intervention. For example, an automatic temperature control system can adjust the room temperature to a set value automatically.

反馈（Feedback）：A signal that is sent back from the output of a system to its input to influence the system's behavior. Negative feedback is often used to make a system more stable. For instance, in a speed control system of a car, the actual speed information (feedback) is compared with the desired speed, and then adjustments are made to maintain the correct speed.

控制器（Controller）：A device or algorithm that determines the appropriate control action based on the input signals and a control strategy. A PID controller is widely used in industrial control systems.

被控对象（Controlled plant）：The system or process that is to be controlled. In a chemical reactor temperature control system, the chemical reactor is the controlled plant.

（二）系统类型

开环控制系统（Open-loop control system）：A control system in which the control action is independent of the output of the system. For example, a simple timer-based sprinkler system waters the lawn for a set period regardless of the actual moisture level of the lawn.

闭环控制系统（Closed-loop control system）：Also known as a feedback control system. The control action is determined by comparing the output of the system with a reference input and taking corrective actions based on the error. Home thermostats are typical closed-loop control systems that adjust the heating or cooling equipment according to the measured room temperature.

线性系统（Linear system）：A system whose output is directly proportional to its input. Mathematical models of linear systems are relatively easy to analyze and design. For example, a simple resistor-capacitor (RC) circuit can be considered a linear system within a certain range of input values.

非线性系统（Nonlinear system）：A system where the relationship between input and output is not linear. Many real-world systems, such as biological systems and some mechanical systems with friction, are nonlinear systems. Analyzing and controlling nonlinear systems is generally more complex than linear systems.

（三）控制理论相关

传递函数（Transfer function）：A mathematical model that describes the relationship between the Laplace transform of the output and the Laplace transform of the input of a linear time-invariant system. It is widely used in the analysis and design of control systems. For example, for a simple first-order system, the transfer function $G(s)=\frac{1}{Ts + 1}$, where $T$ is the time constant.

稳定性（Stability）：The ability of a system to return to its equilibrium state after being disturbed. A stable control system is essential for reliable operation. There are various methods to analyze the stability of a system, such as the Routh-Hurwitz criterion and the Nyquist stability criterion.

时域分析（Time-domain analysis）：The study of a system's response over time. Parameters like rise time, peak time, and settling time are important indicators in time-domain analysis. For example, when analyzing the step response of a second-order system, these parameters can help evaluate the system's performance.

频域分析（Frequency-domain analysis）：Analyzes a system's behavior in terms of frequency. Bode plots and Nyquist plots are common tools in frequency-domain analysis. They can provide information about a system's gain and phase characteristics at different frequencies.

二、专业语句示例

In an automatic control system, the controller continuously monitors the output of the controlled plant and adjusts its input to keep the output close to the desired value.（在自动控制系统中，控制器持续监测被控对象的输出，并调整其输入，以使输出接近期望值。）

Feedback control can improve the performance and stability of a system by reducing the error between the actual output and the reference input.（反馈控制可以通过减小实际输出与参考输入之间的误差来提高系统的性能和稳定性。）

The transfer function of a system provides a convenient way to analyze its dynamic characteristics and design appropriate controllers.（系统的传递函数为分析其动态特性和设计合适的控制器提供了一种便捷的方法。）

To ensure the stability of a closed-loop control system, various stability criteria need to be satisfied.（为确保闭环控制系统的稳定性，需要满足各种稳定性准则。）

三、专业文献选段示例

Stability Analysis of a Multivariable Control System

In modern industrial applications, multivariable control systems are becoming increasingly important. However, analyzing the stability of such systems is more complex compared to single-variable systems.

Consider a multivariable linear time-invariant system described by the state-space model $\dot{x}(t)=Ax(t)+Bu(t)$, $y(t)=Cx(t)$, where $x(t)$ is the state vector, $u(t)$ is the input vector, $y(t)$ is the output vector, and $A$, $B$, $C$ are matrices of appropriate dimensions.

One common approach to stability analysis is the use of Lyapunov theory. A positive definite function $V(x)$ is defined, and if $\dot{V}(x)<0$ for all non-zero $x$, the system is asymptotically stable. Another method is to transform the system into the frequency domain and use techniques such as the Nyquist stability criterion for multivariable systems. This involves analyzing the behavior of the system's transfer matrix at different frequencies to determine its stability. Understanding the stability of multivariable control systems is crucial for ensuring the reliable operation of complex industrial processes.

（### 多变量控制系统的稳定性分析
在现代工业应用中，多变量控制系统正变得越来越重要。然而，与单变量系统相比，分析此类系统的稳定性更为复杂。

考虑一个由状态空间模型$\dot{x}(t)=Ax(t)+Bu(t)$，$y(t)=Cx(t)$描述的多变量线性时不变系统，其中$x(t)$是状态向量，$u(t)$是输入向量，$y(t)$是输出向量，$A$、$B$、$C$是适当维数的矩阵。

稳定性分析的一种常用方法是使用李雅普诺夫理论。定义一个正定函数$V(x)$，如果对于所有非零$x$都有$\dot{V}(x)<0$，则系统是渐近稳定的。另一种方法是将系统转换到频域，并使用诸如多变量系统的奈奎斯特稳定性准则等技术。这涉及分析系统传递矩阵在不同频率下的行为以确定其稳定性。理解多变量控制系统的稳定性对于确保复杂工业过程的可靠运行至关重要。）