tailieunhanh - Understanding Automotive Electronics 5 Part 6

Tham khảo tài liệu 'understanding automotive electronics 5 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MICROCOMPUTER INSTRUMENTATION AND CONTROL 4 With proper software a microcomputer can replace the error amplifier and control logic used in the closed-loop control system. Closed-Loop Control System Recall the basic closed-loop control system block diagram of Chapter 2. The error amplifier compares the command input with the plant output and sends the error signal to the control logic. The control logic uses the error signal to generate a plant control signal that causes the plant to react with a new output so that the error signal will be reduced toward zero. The control logic is designed so that the plant s output follows or tracks the command input. A microcomputer can replace the error amplifier and the control logic. The computer can compare command input and plant output and perform the computation required to generate a control signal. Limit-Cycle Controller The limit-cycle controller discussed in Chapter 2 can be readily implemented with a microcomputer. Recall that the limit-cycle controller controls the plant output so that it falls somewhere between an upper and lower limit preferably so that its average value is equal to the command input. The controller must read in the command input and the plant output and decide what control signal to send to the plant based on those signals alone. Using a microcomputer the upper and lower limit can be determined from the command input by using a lookup table similar to that discussed later in this chapter. The plant output is compared against these two limits. If the plant output is above the higher limit or below the lower limit the microcomputer outputs the appropriate on off signal to the plant to bring the output back between the two limits. Recall that in Chapter 2 the concept of a feedback control system was introduced. There it was shown that a control system compares the value of some controlled variable with a desired value or set point for that variable. In such a control system the difference between the