Tham khảo tài liệu 'anatomy of a robot part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 26 CHAPTER TWO Open your eyes and see how well you did. Likely as not you won t be satisfied with the light level because the steady state error will be too large. You will have to make a correction in the light intensity to be comfortable reading under the light. The corrections you have made in these two experiments by finally using your eyes illustrates an important concept. An open-loop control system can be improved if it is told how well its output matches the input requirements. With that somewhat broad statement we ll introduce another type of control system. Closed-Loop Control Closed-loop control systems are also referred to as feedback control systems because information flows backwards at some point within the control system. Generally this reverse information flows from the output of the control system backward toward the input. The information that flows backwards allows the control system to make corrections in its output. Figure 2-5 is a generalized diagram of a simple closed-loop control system. Information flows backwards in the system from the output signal to somewhere near the input. I ve labelled this reverse information flow feedback. In this simple version of a close-loop control system the output signal is sent back and directly compared to the requirements set by the input signal. The circle shows an arithmetic computation subtraction . If the output does not directly match the input the actuator will receive a nonzero signal at its input and provide corrections at the output so its input returns to zero. In practice many different kinds of closed-loop control systems exist and as such one could make many variations to this diagram. Many control systems do not have outputs that are directly comparable to the inputs the circle in Figure 2-5 must be much more complex than a simple subtraction element. Often the output signal must be transformed before it can be compared to the input sig- FIGURE 2-5 Closed-loop control systems use feedback. .
