Adaptive PID thermal control method with inverse hysteresis

Abstract

FIELD: automatic control of heating systems.SUBSTANCE: target temperature is adjusted using a proportional controller based on average measured room temperature values for the current time period to the level of the basic setpoint, then the basic setpoint received from the proportional controller is changed according to the inverse hysteresis principle: at the beginning of each time period, set at the level of the maximum deviation from the set temperature, and then linearly decreased to the minimum level by the end of the period, forming the final adjusted target temperature value, which is transmitted to the input of the PID controller, the specified change in the target temperature ensures the guaranteed switching on of the heating device at the beginning of the period and its subsequent switching off by the end of the period, while the repeated supply of the switching on signal for the heating system during this period is blocked.EFFECT: increasing the accuracy of maintaining a set air temperature in the room.1 cl, 2 dwg

Description

[0001] There are known room temperature control systems that use the hysteresis method (USSR Author's Certificate No. 1075089, class G01K 7 / 38, 1981. 2, Sheftel I. Thermistors. Moscow, Nauka, 1973).

[0002] A disadvantage of hysteresis control is its inability to effectively compensate for the heating system's response time, which is especially critical for underfloor heating systems. This leads to significant temperature fluctuations in the room.

[0003] The closest analogue is the PID control method, which provides more accurate temperature regulation (Nikulin, E.A. Fundamentals of the theory of automatic control. Frequency methods of analysis and synthesis of systems: a textbook for universities / E.A. Nikulin. - St. Petersburg: BHV - Petersburg, 2004. - 640 p.: ill. - ISBN 5-94157-440-1. - P. 573-574).

[0004] A disadvantage of standard PID control is its focus on continuous control of the heating element's power. This makes it unsuitable for heating systems controlled discretely—by switching pumps, servo drives, and other similar elements on and off. This increases the load on the control elements and reduces the service life of the system as a whole.

[0005] The technical result of the proposed invention is to increase the accuracy of maintaining a preset room temperature by adapting the setpoint, ensuring a comfortable microclimate and streamlining the on / off cycles of heating devices by limiting the switching frequency. This reduces the load on control elements and increases the service life of the system as a whole. This technical result is particularly suitable for heating systems with high inertia and discrete control of heating elements, such as underfloor heating systems or systems controlled by pumps and servo drives.

[0006] Essence of the invention

[0007] In the temperature maintenance algorithm, the PID controller controls the switching on / off of heating devices, and switching on is allowed only at the beginning of a time period with a positive value of the control action, and no more than once per period.

[0008] The average value of the target temperature (setpoint) is adjusted by the proportional controller based on the average measured values ​​of the air temperature in the room over the specified time period.

[0009] The target temperature (setpoint) adjusted by the proportional controller changes according to the inverse hysteresis principle: at the beginning of each time period, it is set at the level of the maximum deviation from the set temperature, and then decreases linearly to the minimum level by the end of the period.

[0010] The specified change in target temperature ensures that the heating device is turned on at the beginning of the period and then turned off at the end of the period, while the repeated signal to turn on the heating system is blocked during this period.

[0011] This joint operation of the elements ensures high accuracy of temperature maintenance, reduces the load on the control elements and increases the efficiency of the system as a whole.

[0012] The combination of these elements provides a synergistic effect that is not achievable in known solutions.

[0013] Fig. 1 shows the structural diagram of the adaptive temperature control system using a PID controller with inverse hysteresis, combining the following functional blocks: a discrete PID controller (1), a proportional controller (2), and an inverse hysteresis module (3). The system ensures the maintenance of a stable temperature in the controlled object (4) (room) by turning on / off the control device (5).

[0014] The control signal (on / off) for the device (5) is generated by the discrete PID controller (1) by processing the error signal (6) and the two-stage-corrected target temperature value, which serves as the setpoint (7), which ensures precise control of the heating element.

[0015] The first stage of correction is carried out by the proportional controller (2), which, based on the received data from the feedback (error signal) (8), corrects the target temperature value (9) to the level of the basic setpoint (10) based on the average room temperature (4) for the current time period.

[0016] In the second stage, the basic setpoint (10) received from the proportional controller (2) is further changed in the inverse hysteresis module (3) depending on the current position in the time period, forming the final adjusted value of the target temperature (setpoint) (6), which is fed to the input of the PID controller (1)."

[0017] Fig. 2 shows a diagram where the set time period (1), which is 1 hour, is plotted along the abscissa axis, and the temperature values ​​are plotted along the ordinate axis.

[0018] The diagram displays:

[0019] Adjusted base setpoint line (2) generated by proportional controller;

[0020] Zigzag line of the adjusted setpoint (3) generated by the inverse hysteresis module, limited by the upper (4) and lower (5) hysteresis boundaries;

[0021] Direct target temperature (6) set by the user;

[0022] The current room temperature curve (7) measured by the sensor for the purpose of feedback and subsequent adjustment of the target temperature;

[0023] Average value line of the current temperature (8).

[0024] The intersection points of the current room temperature curve (7) and the adjusted setpoint curve (3), generated by the inverse hysteresis module, play a key role in the algorithm's operation. It is at these points that the PID controller modifies the control signal, determining the moments when the heating element is turned on or off, ensuring orderly switching. It also shows how the proportional controller adjusts the setpoint (2) when the average temperature (8) drops below the target temperature (6).

Claims

A method for maintaining a set temperature in a room, including controlling the switching on and off of heating devices by means of a proportional-integral-differential (PID) controller in discrete form, characterized in that the switching on of the heating devices is controlled cyclically in limited time periods, during which the switching on of the heating devices is permitted no more than once, only at the beginning of the time period, provided that the value of the control action calculated by the discrete formula of the PID controller is positive, the value of the target temperature (setpoint) is adjusted by a proportional controller on the basis of average measured values ​​of the temperature in the room for the current time period to the level of the basic setpoint, the basic setpoint received from the proportional controller is changed according to the principle of inverse hysteresis: at the beginning of each time period it is set at the level of the maximum deviation from the set temperature,and then decreases linearly to a minimum level by the end of the period, forming the final adjusted value of the target temperature (setpoint), which is transmitted to the input of the PID controller, the specified change in the target temperature ensures the guaranteed switching on of the heating devices at the beginning of the period and their subsequent switching off by the end of the period, while the repeated supply of the switching on signal for the heating devices during this period is blocked.

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