CN204347631U - Based on the tank level control system of fuzzy - Google Patents

Abstract

The utility model discloses a liquid level control system based on fuzzy PID, which comprises a fuzzy PID controller, a liquid level setter, a D/A conversion circuit, a water pump, a driving circuit for driving the water pump, and a device for detecting the liquid level. Liquid level sensor, A/D conversion circuit; the output end of the liquid level setter is connected to the preset signal input end of the fuzzy PID controller, and the fuzzy PID controller, D/A conversion circuit, drive circuit, and water pump are connected in sequence, The liquid level sensor is used to collect the liquid level of the water pump, the output end of the liquid level sensor is connected to the A/D conversion circuit, and the output end of the A/D conversion circuit is connected to the measured signal input end of the fuzzy PID controller. The utility model constitutes a closed-loop system, which not only retains the advantages of traditional PID, but also combines the advantages of fuzzy control to achieve higher precision and stability. It is suitable for environments that require high measurement accuracy, and the measurement is convenient, and real-time data can be obtained from the LED display.

Description

Liquid Level Control System Based on Fuzzy PID

technical field

The utility model relates to the field of liquid level control, in particular to a liquid level control system based on fuzzy PID.

Background technique

Generally, water pumps cannot directly and accurately control the liquid level. The common method now is to use a PID controller to control the water pressure change, but the PID controller requires the design of an accurate mathematical model. The charging of the pressure is relatively slow, so the water pump liquid level control system in the prior art is a large lagging system, and it is very difficult to deal with complex systems such as time-varying and nonlinear systems.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art. The utility model provides a liquid level control system based on fuzzy PID. While retaining the advantages of traditional PID control, combined with the advantages of fuzzy control, the liquid level can be controlled in real time. control to achieve higher precision and stability.

The purpose of this utility model and its technical solution are to adopt the following technical solutions to achieve.

Fuzzy PID-based liquid level control system, including fuzzy PID controller, liquid level setter, D/A conversion circuit, water pump, driving circuit for driving the water pump, liquid level sensor for detecting liquid level, A/D conversion circuit.

The output end of the liquid level setter is connected to the preset signal input end of the fuzzy PID controller, the fuzzy PID controller, the D/A conversion circuit, the drive circuit, and the water pump are connected in sequence, and the liquid level sensor is set in the water pump for The liquid level of the water pump is collected, the output end of the liquid level sensor is connected to the A/D conversion circuit, and the output end of the A/D conversion circuit is connected to the actual measurement signal input end of the fuzzy PID controller.

The liquid level sensor collects the liquid level of the water pump in real time, and the output end of the liquid level sensor is processed by the A/D conversion circuit into a digital liquid level height, and then connected to the actual measurement signal input end of the fuzzy PID controller;

The fuzzy PID controller takes the difference between the digital liquid level height and the set liquid level height as the input quantity of the fuzzy PID controller. After the fuzzy PID controller performs proportional, differential and integral algorithms, it outputs the control signal. The output end is connected to the drive circuit through the D/A conversion circuit to control the liquid level of the water pump.

When in use, first provide the preset value of the liquid level height to the fuzzy PID controller through the liquid level setter; then measure the actual liquid level height signal through the liquid level sensor, and provide it to the fuzzy PID controller after being processed by the A/D conversion circuit Due to the difference between the preset value and the measured value of the liquid level height, the control signal for the water pump can be obtained after the fuzzy PID controller performs proportional, differential and integral algorithms on the obtained signal; finally, the fuzzy PID control The controller provides the obtained control signal to the driving circuit through the D/A conversion circuit to drive the water pump to control the liquid level; the liquid level control system based on fuzzy PID in the utility model is a closed-loop system with online parameter self-tuning ability. It is worth pointing out that the fuzzy PID control algorithm used in the control process of the fuzzy PID controller of the present invention is the proportional, differential and integral algorithm of the prior art. connection structure.

The fuzzy PID controller is designed with single-chip microcomputer or DSP as the base, and can choose different single-chip microcomputer or DSP according to the requirements of different measurement accuracy; because DSP has the advantages of high measurement control precision, low cost, small size, and low power consumption, it can Made into a stand-alone machine, it is widely used in chemical industry, farmland and other industries to precisely control the liquid level.

The liquid level setter includes a keyboard. The liquid level is set through the keyboard input, and the set liquid level is transmitted to the fuzzy PID controller. The keyboard input is a traditional and commonly used input tool, which is cheap and easy to use.

The D/A conversion circuit and the A/D conversion circuit select different resolutions according to the actual measurement accuracy requirements, and select the operating frequency of the D/A conversion circuit and the A/D conversion circuit.

Preferably, the liquid level sensor is a pressure sensor for measuring liquid level, including an isolated diffused silicon sensitive element or a ceramic capacitor pressure sensitive sensor. The signal measured by the liquid level sensor is processed by the A/D conversion circuit and then converted into a digital quantity and sent to a single-chip microcomputer or DSP.

Preferably, the utility model also includes an LED display, the signal display output of the fuzzy PID controller is connected to an LED display, and the LED display is used to display the liquid level height set by the liquid level setter and the actual measurement The digital liquid level height. The detection data can be intuitively provided to the user through the LED display, which is convenient for the user to analyze and monitor the system.

Compared with the prior art, the utility model has the advantages that:

The liquid level control system based on fuzzy PID provided by the utility model constitutes a closed-loop system, which not only retains the advantages of traditional PID, but also combines the advantages of fuzzy control. Level height, and then through the fuzzy PID controller to realize the real-time adjustment and control of the liquid level, to achieve the same height as the set liquid level, and to control the liquid level in real time to achieve higher accuracy and stability. It is suitable for environments that require high measurement accuracy, and the measurement is convenient, and real-time data can be obtained from the LED display.

Description of drawings

Fig. 1 is the basic structural representation of the liquid level control system based on fuzzy PID that the utility model provides;

Fig. 2 is a schematic structural diagram of the specific implementation of the fuzzy PID-based liquid level control system provided by the present invention.

detailed description

Below in conjunction with accompanying drawing, the utility model is described further.

Below in conjunction with accompanying drawing, the utility model is further described. The following examples are only used to illustrate the technical solution of the utility model more clearly, but not to limit the protection scope of the utility model.

As shown in Figure 1, the liquid level control system based on fuzzy PID includes a fuzzy PID controller, a liquid level setter, a D/A conversion circuit, a water pump, a driving circuit for driving the water pump, and a liquid level detector for detecting the liquid level. Bit sensor, A/D conversion circuit.

The output end of the liquid level setter is connected to the preset signal input end of the fuzzy PID controller, and the fuzzy PID controller, D/A conversion circuit, drive circuit, and water pump are connected in sequence, and the liquid level sensor is used to collect the liquid level of the water pump , the output end of the liquid level sensor is connected to the A/D conversion circuit, and the output end of the A/D conversion circuit is connected to the measured signal input end of the fuzzy PID controller.

The liquid level sensor collects the liquid level of the water pump in real time, and the output end of the liquid level sensor is processed by the A/D conversion circuit into a digital liquid level height, and then connected to the actual measurement signal input end of the fuzzy PID controller;

The fuzzy PID controller takes the difference between the digital liquid level height and the set liquid level height as the input quantity of the fuzzy PID controller. After the fuzzy PID controller performs proportional, differential and integral algorithms, it outputs the control signal. The output end is connected to the drive circuit through the D/A conversion circuit to control the liquid level of the water pump.

In Fig. 1, the module structure diagram of the liquid level control system based on the fuzzy PID of the present invention, the liquid level sensor detects the actual liquid level height, after being processed by the A/D conversion circuit, it is sent to the interface of the fuzzy PID controller. The liquid level height is set by typing in the keyboard. There is a certain difference between this value and the liquid level height signal converted by the A/D conversion circuit. After the proportional, differential and integral algorithms are performed by the fuzzy PID controller, the output signal passes through The D/A conversion circuit and the drive circuit control the liquid level of the water pump. The liquid level entered by the keyboard and the actual liquid level detected during the control process can be displayed on the LED display in real time.

Fig. 2 is another preferred embodiment of the present utility model, and the liquid level sensor in Fig. 2 and A/D conversion circuit constitute the liquid level height signal acquisition in the embodiment, after filtering, amplifying, sampling and A/D conversion Send it to a single-chip microcomputer or DSP, compare it with a given voltage signal and calculate the deviation. The single-chip microcomputer or DSP completes the function of the fuzzy PID controller, and its output signal controls the liquid level of the water pump through the D/A conversion circuit and the driving circuit, thereby completing the dynamic adjustment of the liquid level. The whole system constitutes a closed-loop system, so the liquid level control system based on fuzzy PID of the utility model has better online parameter self-tuning ability, better anti-interference performance, better dynamic characteristics, and better Strong adaptive ability.

The D/A conversion circuit and the A/D conversion circuit select different resolutions according to the actual measurement accuracy requirements, and select the operating frequency of the D/A and A/D conversion circuits at the same time. In order to improve the accuracy, the highest possible operating frequency can be selected.

The liquid level sensor is a pressure sensor for measuring liquid level, including isolated diffused silicon sensitive elements or ceramic capacitance pressure sensitive sensors. After the measured signal is processed by the A/D conversion circuit, it becomes digital and sent to the microcontroller or DSP.

Single-chip or DSP external memory to store codes and data that still needs to be saved after power failure can be used as a data exchange unit, and the memory is connected to a power-down protection circuit to solve the problem of long-term storage of real-time parameters after power-off; at the same time, single-chip or DSP through The serial port RS232 is connected with the upper computer, and the serial port RS232 can realize the data communication collected between the single-chip microcomputer or DSP and the upper computer, and strengthen the storage, analysis and processing of data.

In this embodiment, the fuzzy PID controller mainly involves three PID parameters Kp (proportional coefficient), Ki (integral coefficient) and Kd (differential coefficient), determine the fuzzy inference rule table through fuzzy control rules and fuzzy reasoning, and then through fuzzy reasoning The rule table sets these 3 control parameters in the fuzzy PID controller. Both fuzzy control rules and fuzzy reasoning are mature technologies in the field of fuzzy control.

Generally, increasing the open-loop proportional coefficient Kp during the debugging process will speed up the response speed of the system, and it will also help reduce the static error when there is a static error, but an excessively large proportional coefficient will increase the system overshoot, or even Oscillation occurs, making the system unstable; therefore, in the field experiment setting method, it is necessary to implement repeated adjustments of proportion first, then integral, and then differential. The integral time is inversely proportional to the proportional time, the larger the integral coefficient is, the shorter the integral time will be, resulting in excessive overshoot. The differential coefficient is directly proportional to the differential time, and if the differential coefficient is too large, that is, the differential time is too large, resulting in system instability.

The above are only preferred embodiments of the present utility model, and it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present utility model, some improvements and modifications can also be made. It should be regarded as the protection scope of the present utility model.

Claims (7)

1. based on the tank level control system of fuzzy, it is characterized in that: comprise fuzzy controller, level set device, D/A change-over circuit, water pump, the driving circuit that water pump is driven, liquid level sensor, A/D change-over circuit that liquid level is detected;

The preset signals input end of the output terminal access fuzzy controller of described level set device, fuzzy controller, D/A change-over circuit, driving circuit, water pump are linked in sequence successively, described liquid level sensor is for gathering the liquid level of described water pump, the output terminal of liquid level sensor connects A/D change-over circuit, the measured signal input end of the output terminal access fuzzy controller of A/D change-over circuit.

2., according to the tank level control system based on fuzzy described in claim 1, it is characterized in that: described fuzzy controller with single-chip microcomputer or DSP for substrate.

3. according to the tank level control system based on fuzzy described in claim 1, it is characterized in that: described level set device comprises keyboard, by described keyboard for inputting the setting liquid level of water pump, and described setting liquid level is transferred to described fuzzy controller.

4. according to the tank level control system based on fuzzy described in claim 1, it is characterized in that: also comprise light-emitting diode display, the Signal aspects output terminal of described fuzzy controller connects light-emitting diode display.

5. the tank level control system based on fuzzy according to claim 4, is characterized in that: described light-emitting diode display is for showing liquid level and the digital quantity liquid level of actual measurement of the setting of level set device.

6. the tank level control system based on fuzzy according to claim 1, is characterized in that: described liquid level sensor is the pressure transducer measuring liquid level.

7. the tank level control system based on fuzzy according to claim 6, is characterized in that: described liquid level sensor comprises isolated form diffuse si sensitive element or ceramic capacitive pressure sensitive sensor.