First, the basic principle of feedback control
Feedback control is a closed-loop control mode, and its core lies in the cyclic process of “measurement-comparison-adjustment”. Firstly, the measuring instrument measures a certain physical quantity (such as temperature, pressure, speed, etc.) of the controlled object in real time; Then, compare the measured data with the set value to get the deviation value; Finally, the control system adjusts the actuator according to the deviation value to reduce or eliminate the deviation and make the system tend to set the target.
Second, the role of measuring instruments in feedback control
The measuring instrument is the “sense organ” of the feedback control system, which is responsible for collecting the key data during the operation of the system. Common measuring instruments include temperature sensor, pressure sensor, flowmeter, displacement sensor, voltmeter and ammeter. These devices convert physical quantities into electrical signals or digital signals to provide accurate feedback information for the controller.
The accuracy, response speed and stability of measuring instruments directly affect the performance of the whole feedback control system. For example, in a temperature control system, if the temperature sensor has a large measurement error or response delay, the controller may make a wrong judgment, resulting in a large fluctuation of the system temperature, and it is impossible to achieve accurate control.
Third, the practical application of feedback control
In industrial automation, measuring instruments, controllers and actuators work together to form a complete feedback control system. For example, in the thermostat control system, the thermocouple or PT100 sensor measures the temperature in the thermostat and sends it to the controller. The controller adjusts the power output of the heating element according to the difference between the current temperature and the preset value, so as to keep the temperature constant.
In the field of intelligent manufacturing, the combination of laser displacement sensor and robot control system can realize real-time detection and automatic correction of workpiece position; In chemical production, mass flowmeter can accurately measure material flow, and cooperate with regulating valve to realize accurate flow control.
In addition, feedback control technology has been widely used in smart home, aerospace, automotive electronics and other fields. For example, the engine control system of an automobile monitors the running state of the engine in real time through oxygen sensors, throttle position sensors and other devices, optimizes fuel injection quantity, improves fuel efficiency and reduces emissions.
Fourth, the development trend
With the development of sensor technology, microelectronics technology and communication technology, measuring instruments are developing towards high precision, miniaturization, intelligence and networking. The intelligent sensor has the functions of data processing and communication, and can directly interact with the host computer or cloud platform to realize remote monitoring and control.
At the same time, the application of artificial intelligence (AI) and big data analysis has also brought new changes to the feedback control system. By analyzing historical data through machine learning algorithm, predictive control can be realized and the adaptive ability of the system can be improved.
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In a word, as the core component of the feedback control system, the performance of the measuring instrument directly affects the control effect of
the system. With the continuous progress of science and technology, measuring instruments will play a more critical role in feedback control, promote the continuous improvement of automation and intelligence, and bring more convenience and efficiency to modern industry and life.