What is the control method of using a tachometer motor as a detection device to form a closed-loop control system?

Question

Among the following options, what is the control method of using a tachometer motor as a detection device to form a closed-loop control system?

A. Open loop

B. Closed loop

C. Semi-closed loop

D. Feed-forward

Answer 1

Answer: B. Closed-loop control.

Answer analysis: When discussing the control method of using a tachometer motor as a detection device to form a closed-loop control system, we first need to understand the basic concept of a closed-loop control system and its differences from open-loop, semi-closed-loop, and feedforward control systems.

A closed-loop control system is a control system that monitors the output signal and compares it with the expected input signal, and then adjusts the system behavior based on the comparison result.

As a detection device, the tachometer motor is used in a closed-loop control system to monitor the motor speed in real time. This speed information is then fed back to the control system for comparison with the set speed value.

Based on the comparison result, the control system adjusts the motor input (such as voltage, current, etc.) to ensure that the actual speed of the motor is consistent with the set value.

Now, let's analyze the options one by one:

A. Open-loop control: There is no feedback loop in an open-loop control system, that is, the system does not monitor the output and compare it with the input.

Therefore, the tachometer motor cannot play its role as a detection device in an open-loop control system. Therefore, option A is incorrect.

B. Closed-loop control: A closed-loop control system has a feedback loop that monitors the output in real time and compares it with the input.

As a detection device, the tachometer motor can accurately monitor the motor speed in a closed-loop control system and feed this information back to the control system to achieve precise speed control. Therefore, option B is correct.

C. Semi-closed-loop control: Semi-closed-loop control systems are often used in high-precision equipment such as machine tools, where the feedback loop only contains some system components (such as the position of the lead screw rather than the final workpiece position).

Although the tachometer motor may play a role in these systems, the question clearly mentions that the tachometer motor is a detection device to form a closed-loop control system, so option C is not the most directly relevant answer.

D. Feedforward control: Feedforward control is a predictive control method that predicts future output based on the system's historical input and output data and adjusts the input accordingly to improve the system's performance. Feedforward control does not rely on real-time output feedback, so the tachometer motor has a limited role in it. Therefore, option D is incorrect.

In summary, the control method that uses the tachometer motor as a detection device to form a closed-loop control system is closed-loop control.

This method can ensure that the motor speed is accurately controllable through real-time monitoring and feedback adjustment, and is widely used in various occasions requiring high-precision speed control.

Answer 2

As an important tool for motor control or monitoring, the tachometer plays a key role in many fields. 

The following is a detailed analysis of the tachometer as a motor-related application:

Basic functions of tachometer

The tachometer is mainly used to measure the speed, linear speed or frequency of the motor. 

It is one of the indispensable instruments in the machinery industry and is widely used in manufacturing industries such as motors, electric fans, papermaking, plastics, chemical fibers, washing machines, automobiles, aircraft, and ships.

Working principle of tachometer

The working principle of the tachometer is diverse, but it is mainly based on the magnetic principle or the electric principle. 

Taking the electric tachometer as an example, it usually consists of a small AC generator, a cable, a motor, and a magnetic head. 

The small AC generator generates AC power, which is transmitted through a cable to drive a small AC motor. 

The speed of the motor is consistent with the speed of the measured shaft. 

The magnetic speed head is coaxially connected to the small AC motor to indicate the speed of the measured shaft.

Application of tachometer in motor control

1. Real-time monitoring: The tachometer can monitor the speed of the motor in real time to ensure that the motor operates within the normal working range. This is essential to prevent motor overload, overheating and other faults.

2. Fault warning: By monitoring the change of speed, the tachometer can detect the abnormal situation of the motor in time, providing support for fault warning and preventive maintenance.

3. Closed-loop control: In the closed-loop control system, the tachometer is used as a feedback element to compare the actual speed of the motor with the set value. The control system adjusts the input of the motor according to the comparison result to achieve precise speed control.

4. Performance evaluation: The tachometer can also be used to evaluate the performance of the motor, such as speed stability, response speed, etc., to provide a basis for the optimization design and improvement of the motor.

Types of tachometers

There are many types of tachometers, including portable tachometers (such as mechanical centrifugal tachometers and digital electronic tachometers) and fixed tachometers. 

Portable tachometers are easy to carry and use, suitable for on-site measurement; while fixed tachometers are usually installed on motors to achieve long-term and stable monitoring.

Summary

In summary, as an important tool for motor control and monitoring, the tachometer has multiple functions such as real-time monitoring, fault warning, closed-loop control and performance evaluation. 

In the motor manufacturing industry and related fields, tachometers are widely used and indispensable. 

With the continuous development of technology, the performance and accuracy of tachometers are also constantly improving, providing more reliable support for the optimized design and stable operation of motors.