第4章 频率法校正实验
Chapter 4 FrequencyCompensation Experiment

用频率法校正设计校正装置，主要是改变频率特性曲线的形状，使之具有合适的高频、中频、低频特性和稳定裕度，以得到满意的闭环品质。用频率法校正控制系统时，通常是以频域指标如相位裕度、增益裕度、谐振峰值和频带宽度来衡量和调整控制系统动态响应性能，而不是按照时域指标如超调量、调节时间和稳态误差等来进行。所以，频率法是一种间接的控制系统设计与分析方法，该方法所利用的工具为伯德图分析法。

Use frequency method to design a compensator，mainly by changing the shape of frequency characteristics curves，to make sure that it has suitable high-frequency，intermediate frequency，low-frequency char-acteristics and stable margin，so that the system will give out closed-loop output of high quality. The main frequency index of performance are adopted as phase margin，gain margin，the resonance peak and the frequency bandwidth，instead of percent overshoot，settling time etc.，which are used in time domain. Therefore，the frequency method is an indirect method for control system design and analysis. A useful tool is Bode diagram analysis method.

本章使用单自由度机械臂为被控对象，学生们可学习如何运用频率法设计校正装置。其控制系统方框图的构成与图3.1是相同的，实物图的构成则与图3.2相同。本章实验包括两类串联校正系统——超前和滞后校正。

In this chapter，POFR-Arm is used as the controlled plant，students should study how to design an compensator by the frequency method. Its block diagram is the same as in Figure 3.1，and the real control system is shown as Figure 3.2. Experiments in this chapter include two types of series compensator——lead and lag compensation.