Dry ice temperature control system and method for modem used in ground testing of rotor system

Abstract

The present invention provides a dry ice temperature control system and method for a modem for ground testing of a rotor system, wherein the dry ice temperature control system comprises a portable dry ice thermostat, a fiber grating demodulator and a control system, wherein the thermostat comprises a dry ice room and an equipment room, the dry ice room and the equipment room are isolated by a partition, and a cooling fan is arranged on the partition; a first temperature sensor is arranged in the equipment room; a second temperature sensor is arranged in the dry ice room; the fiber grating demodulator is arranged in the equipment room; the fiber grating demodulator is connected to a fiber grating signal input line, and the fiber grating signal input line is connected to a fiber grating temperature sensor. The present invention adopts dry ice as a cold source, does not require additional energy, reduces the power output burden of a helicopter in the air without ground support, and the temperature control method monitors the dry ice temperature in real time, can adjust the cooling fan in real time according to the dry ice temperature, and the temperature adjustment process is smooth, which can achieve an ideal cooling effect.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature control of electronically controlled test equipment, and in particular to a dry ice temperature control system and method for a modem used for ground testing of a rotor system. Background Art

[0002] The rotor is the core component that provides power and control for the helicopter. Dynamic monitoring of blade structural loads is the main basis for dynamic characteristics analysis and blade design verification of rotor blades, which directly affects the strength, performance and flight characteristics of the helicopter. The dynamic load test of rotor blades has the characteristics of complex distribution, large range, dense measurement points, sensitivity to additional mass, high dynamic response, and is in a complex environment such as rotation and vibration. How to monitor the dynamic load of the blades in flight and analyze and evaluate their operating status in real time is the focus of helicopter measurement technology. The blade bending moment is an important parameter for identifying the blade structural load. It is very important to measure the dynamic bending moment of the rotor blades in real time during operation and realize the dynamic monitoring of the blade structural load.

[0003] Traditional rotor load tests use electrical sensors to obtain measurement data, which has a low signal-to-noise ratio and seriously affects the accuracy of rotor load identification. A large number of strain gauges need to be pasted to access a large number of transmission wires. When measuring multiple points on the surface of composite blades, the smoothness and structure of the blade surface will be destroyed, resulting in a large additional mass, which will affect the aerodynamic flight characteristics of the blade. Fiber Bragg grating sensors have the advantages of small size, light weight, electrical insulation, anti-electromagnetic interference, high precision, high reliability, high sensitivity of fiber Bragg gratings, and easy to achieve high efficiency of distributed measurement. They break through the limitations of traditional electrical sensor-based measurement methods, and fiber Bragg grating sensors can directly measure multiple physical quantities such as strain, degree, vibration, etc., reduce the complexity of the system, simplify the system structure, and facilitate the maintenance characteristics of the monitoring system itself.

[0004] However, due to the process limitations and principle characteristics of existing optoelectronic devices, the operating temperature range of optical devices or optoelectronic devices is relatively narrow. The operating temperature range of the demodulator in the fiber Bragg grating demodulation system used in this experiment is -20℃~60℃. The service conditions of the rotor are -45℃~75℃. Since the demodulator cannot work at low or high temperatures, a constant temperature device is required to ensure the normal operation of the device. In the aerial test of the helicopter, the volume and weight of the demodulator constant temperature box must be strictly controlled. The demodulator needs to be installed in the fairing on the top of the helicopter. Therefore, the constant temperature box needs to have the characteristics of small size, light weight, and good constant temperature effect; in the aerial test of the helicopter, the power supply that the helicopter can provide for the insulation device is relatively low. Using dry ice as a cold source can effectively reduce the requirements for energy supply.

[0005] The rotor is the core component that provides power and control for the helicopter. Dynamic monitoring of blade structural loads is the main basis for dynamic characteristics analysis and blade design verification of rotor blades, which directly affects the strength, performance and flight characteristics of the helicopter. The dynamic load test of rotor blades has the characteristics of complex distribution, large range, dense measurement points, sensitivity to additional mass, high dynamic response, and is in a complex environment such as rotation and vibration. How to monitor the dynamic load of the blades in flight and analyze and evaluate their operating status in real time is the focus of helicopter measurement technology. The blade bending moment is an important parameter for identifying the blade structural load. It is very important to measure the dynamic bending moment of the rotor blades in real time during operation and realize the dynamic monitoring of the blade structural load.

[0006] Traditional rotor load tests use electrical sensors to obtain measurement data, which has a low signal-to-noise ratio and seriously affects the accuracy of rotor load identification. A large number of strain gauges need to be pasted to access a large number of transmission wires. When measuring multiple points on the surface of composite blades, the smoothness and structure of the blade surface will be destroyed, resulting in a large additional mass, which will affect the aerodynamic flight characteristics of the blade. Fiber Bragg grating sensors have the advantages of small size, light weight, electrical insulation, anti-electromagnetic interference, high precision, high reliability, high sensitivity of fiber Bragg gratings, and easy to achieve high efficiency of distributed measurement. They break through the limitations of traditional electrical sensor-based measurement methods, and fiber Bragg grating sensors can directly measure multiple physical quantities such as strain, velocity, and vibration, reduce the complexity of the system, simplify the system structure, and facilitate the maintenance characteristics of the monitoring system itself.

[0007] Using the aerial dynamic test method, the harsh high and low temperature environment puts forward requirements for the fiber Bragg grating demodulator. Due to the process limitations and principle characteristics of existing optoelectronic devices, the operating temperature range of optical devices or optoelectronic devices is relatively narrow. The working temperature range of the demodulator in the fiber Bragg grating demodulator system used in this test is -20℃~60℃. At the same time, during the aerial test of the helicopter, it loses the support of the ground, and the protection equipment of the fiber Bragg grating demodulator should consume as little energy as possible. Therefore, it is more suitable to use dry ice as a cold source. The traditional temperature control method directly controls the refrigeration and heating device to directly cool or heat to adjust the temperature through the feedback of the temperature sensor. For the refrigeration equipment with dry ice as the cold source, the refrigeration efficiency is constantly changing. If the traditional temperature control method is used, there will be a long time span for temperature adjustment and untimely response. The temperature of the helicopter changes dramatically during the movement, and the internal temperature needs to be adjusted in time according to the external environment. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and provide a dry ice temperature control system and method for a modem for ground testing of a rotor system. The dry ice temperature control system has a simple structure, small size, and light weight, and is convenient for improving the operating temperature range of the fiber grating demodulator, the main equipment of the fiber grating demodulation system. The present invention uses dry ice as a cold source, does not require additional energy, and reduces the power output burden of the helicopter in the air without ground support. The temperature control method monitors the dry ice temperature in real time, can adjust the refrigeration fan in real time according to the dry ice temperature, and the temperature adjustment process is smooth, which can achieve an ideal refrigeration effect.

[0009] The technical scheme of the present invention is: a modem dry ice temperature control system for ground testing of a rotor system, comprising a dry ice portable constant temperature box, a fiber grating demodulator and a control system, wherein the constant temperature box comprises a dry ice room and an equipment room, a partition is used between the dry ice room and the equipment room to isolate the air flow of the two spaces, and a cooling fan is arranged on the partition; a first temperature sensor is arranged in the equipment room; a second temperature sensor is arranged in the dry ice room; the fiber grating demodulator is arranged in the equipment room; the control system is arranged in a heat preservation layer arranged on the side wall of the equipment room; the fiber grating demodulator is connected to a fiber grating signal input line, and the fiber grating signal input line is connected to a fiber grating temperature sensor arranged on the outer wall of the constant temperature box.

[0010] The dry ice chamber and the equipment chamber are located in a PU plastic shell, and the insulation layer is located between the side wall of the equipment chamber and the PU plastic shell; the insulation layer is a polyurethane insulation layer.

[0011] The fiber grating demodulator is arranged in the equipment room by means of a fixing fixture.

[0012] A method for controlling a dry ice temperature control system of a modem for ground testing of a rotor system comprises the following steps:

[0013] 1) Detecting the temperature data of each area according to an agreed period, wherein the areas are three areas: the external area of ​​the thermostat corresponding to each grating in each fiber Bragg grating temperature sensor string, the equipment room corresponding to the first temperature sensor, and the dry ice room corresponding to the second temperature sensor; wherein the first temperature sensor corresponds to the temperature value A of the equipment room inside the thermostat, wherein the temperature value A is the temperature collected at each time node; the second temperature sensor corresponds to the temperature value D of the dry ice room inside the thermostat, wherein the temperature value D is the temperature collected at each time node; the fiber Bragg grating temperature sensor corresponds to the external surface temperature of the thermostat; the control system collects the temperature values ​​detected by each temperature sensor according to the agreed period; wherein the information collected by the fiber Bragg grating temperature sensor is analyzed and processed by the fiber Bragg grating demodulator to obtain multiple temperature values ​​B N (N=1, 2, ..., 20), N is the number of gratings in the fiber Bragg grating temperature sensor;

[0014] 2) When receiving the signal from the resistance temperature sensor at each moment, the control system determines the temperature value A inside the thermostat equipment room. When A>60℃ or A<-20℃, an alarm is sounded and the alarm indicator light is on;

[0015] 3) Obtain the heat transfer coefficient C of the outer wall of the constant temperature box corresponding to each grating temperature sensor to the internal environment of the equipment N The method for obtaining the heat transfer coefficient is as follows: when the temperatures inside and outside the thermostat are the same, the position where the grating temperature sensor is set on the outer surface of the thermostat is heated or cooled, the surface temperature of the same part of the inner and outer walls of the thermostat is measured, and the absolute value after subtracting the inner and outer temperatures is taken. The absolute value is the heat transfer coefficient;

[0016] 4) Set the target temperature value S to be maintained in the thermostat, -20℃ <S<60℃;

[0017] 5) Determine the cooling efficiency g of the cooling fan; the cooling efficiency is determined according to the change of the temperature value D in the dry ice chamber, which is the ratio of the temperature difference between the dry ice chamber and the equipment room at the current moment to the starting moment. The initial temperature of the dry ice chamber is -20℃, -20 <D<A,0<g<1;

[0018] 6) Determine the first difference function e(t)=SA between the temperature inside the thermostat equipment room and the target temperature, where the first difference function is a function of the difference between the temperature value A inside the thermostat equipment room and the target temperature value S over time; determine the second difference function between the temperature of the outer wall of the thermostat and the target temperature The calculation method for the second difference function is as follows: first obtain the temperature value B of each grating temperature sensor N And the corresponding heat transfer coefficient C N The average value after multiplication, the difference between the average value and the target temperature as a function of time is the second difference function, and N is the number of outer wall temperature sensor gratings;

[0019] 7) Determining a first output function by the first difference function; obtaining the first output function by accumulating proportional integral calculation, integral calculation and differential calculation; Among them, K p e(t) is a proportional integral calculation, that is, the temperature difference function e(t) inside and outside the constant temperature box at time t is multiplied by a proportional gain K p ,K p =0.65K c ,K c It is a PID control system that minimizes the steady-state error of the control system under the condition of using only proportional control. e(t) =K c K in e(t) c value; by adjusting K pCan control the speed at which the thermostat reaches the target temperature, K p The larger it is, the faster it approaches the target temperature. In the integral calculation phase, taking into account the past errors, the first difference function is integrated from the beginning to the current moment and combined with the integral gain K i multiply; t is the PID control sampling calculation period, T i is the integration time of the control system; The differential calculation phase, that is, taking into account the upcoming error, calculates the first derivative of the first difference function and a positive constant K d Multiply, t is the differential time of the control system; the three parameters are all adaptive parameters and are greater than 0; t is the independent variable of time change;

[0020] 8) Determine the second output function by the second difference function; obtain the second output function by accumulating proportional calculation, integral calculation and differential calculation Among them, the proportional calculation, integral calculation and differential calculation are all obtained based on the second difference function f(t), and the meaning and method are the same as the first output function. The three calculation links and parameter functions are the same as the first output function;

[0021] 9) Determine the output function; the output function μ(t) is obtained by adding the first function and the second function; wherein the output function μ(t) is μ(t)=αPID e(t) +βPID f(t) , where α and β are the adaptation parameters of the first output function and the second output function respectively; α is the proportional parameter corresponding to the difference between the internal ambient temperature of the equipment room and the maximum temperature difference of 40°C, e is the temperature difference between the current internal ambient temperature of the constant temperature box equipment room and the set target temperature when the control system is sampling, when the internal ambient temperature of the equipment room changes within the range of -40°C or above 70°C, α is 1, when the internal ambient temperature of the equipment room is the same as the target temperature, α is 0; β is the proportional parameter corresponding to the external ambient temperature difference and the maximum temperature difference of 55°C, f is the temperature difference between the current external ambient temperature and the set target temperature when the control system is sampling, when the external ambient temperature changes within the range of -20°C or above 60°C, β is 1, when the external ambient temperature is the same as the target temperature, β is 0; the total output function is y(t) = μ(t)*g, y≥0, which is obtained by multiplying the output function μ(t) by the refrigeration efficiency g, the purpose of which is to compensate for the weakening of the dry ice refrigeration effect by increasing the fan output during the temperature change of the dry ice room;

[0022] 10) The control system drives the refrigeration fan to rotate according to the total output y(t); by adjusting the fan voltage and thus the fan speed, the cold air in the dry ice room is transported to the equipment room, thereby reducing the ambient temperature in the equipment room.

[0023] Beneficial effects of the invention: The invention discloses a dry ice temperature control system and method for a modem used for ground testing of a rotor system.

[0024] The dry ice temperature control system of the present invention has the following beneficial effects:

[0025] 1. The working temperature range of the demodulator of the fiber Bragg grating demodulation system is -20°C to 60°C, while the service environment of the device is -45°C to 75°C. Therefore, the present invention provides a constant temperature device for extending the working temperature range of the fiber Bragg grating demodulator.

[0026] 2. During the aerial test of the helicopter, the demodulator is located in the fairing on top of the helicopter rotor. Under this condition, the demodulator will be affected by the rotation and vibration of the rotor during movement. Therefore, the demodulator not only needs a suitable temperature working environment, but also a fixing device to prevent the demodulator from collision damage. The existing demodulator insulation device uses semiconductor refrigeration to maintain the temperature fluctuation in the constant temperature box, and has a large size. Since the fairing on the top of the helicopter is small, this type of device cannot be used for aerial testing of helicopter rotors. This device uses dry ice refrigeration to control the temperature in the constant temperature box, and has the advantages of small size and light weight.

[0027] 3. The existing demodulator insulation device uses semiconductor refrigeration to maintain temperature fluctuations in the constant temperature box. When the ambient temperature is high, the refrigeration efficiency of the semiconductor refrigeration device will decrease after working for a long time, and eventually the constant temperature box cannot maintain the specified working temperature. This device can add dry ice according to the working time of the demodulator to keep the temperature in the constant temperature box within the working temperature range.

[0028] 4. The existing demodulator heat preservation device does not take measures to fix the demodulator, so that the existing constant temperature device can only be used in a static test environment on the ground, and cannot be used for dynamic testing in the air. Therefore, the present invention provides a device for fixing the fiber Bragg grating demodulator, so that it has the ability of dynamic testing in the air.

[0029] 5. The existing thermostat device of the demodulator adjusts the cooling or heating according to the changes of the temperature signal of the internal environment to maintain the stability of the internal environment temperature. There are problems such as untimely adjustment and large internal temperature fluctuations. The device analyzes the signal according to the internal and external temperature signals, and inputs it into the control system. The PID algorithm is used to calculate the cooling capacity required to balance the external and internal influences. At the same time, the temperature sensor of the dry ice chamber determines the cooling capacity, so as to adjust the fan speed to control the internal temperature of the equipment room.

[0030] The temperature control method of the dry ice temperature control system of the present invention has the following technical advantages:

[0031] The present invention adopts an active constant temperature control method. The fiber grating demodulator is a part of the control system, which provides the control system with the temperature parameters outside the constant temperature box; actively controls the cooling or heating power in advance, improves the constant temperature efficiency, prolongs the use time, and reduces the temperature fluctuation in the equipment room. The device solves the problem of drastic temperature fluctuations during the constant temperature box adjustment process under external high and low temperature environments and internal heating conditions by first independently calculating the output required by the two internal and external temperature variables and then synthesizing the required output. At the same time, according to the temperature difference between the dry ice room and the equipment room, the speed of the air conditioning fan is adjusted at any time to ensure the cooling power.

[0032] The present invention adopts an active constant temperature control method, and uses a fiber grating demodulator as a part of the control system. The fiber grating demodulator analyzes the fiber grating sensor signal outside the constant temperature box and outputs the function f(t) of the external temperature change; the temperature control system adjusts the refrigeration power according to f(t) to offset the influence of the external environment of the constant temperature box on the fiber grating demodulator. The temperature sensor in the equipment room provides the temperature information inside the equipment room, and the temperature output function e(t) inside the equipment room; the control system eliminates the influence of the self-generated heating of the fiber grating demodulator inside the constant temperature box equipment room according to e(t). The temperature sensor in the dry ice room provides the temperature information of the dry ice room; the temperature output efficiency of the dry ice room is g; the temperature control system increases or decreases the fan speed according to y(t), thereby achieving the best refrigeration efficiency, extending the use time and reducing the temperature fluctuation in the equipment room. The device solves the problem of drastic temperature fluctuations in the constant temperature box adjustment process under the external high and low temperature environment and internal heating conditions by first independently calculating the output required by the two internal and external temperature variables and then synthesizing the required output. At the same time, according to the temperature change in the dry ice room, the fan speed is reasonably adjusted to maintain the refrigeration power in a reasonable range, thereby extending the use time of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Attached Figure 1 : Schematic diagram of the external structure of the portable dry ice thermostat of the present invention;

[0034] Attached Figure 2 : Schematic diagram of the internal structure distribution of the portable dry ice constant temperature box of the present invention;

[0035] Attached Figure 3 : Schematic diagram of the internal structure of the portable dry ice constant temperature box of the present invention;

[0036] Attached Figure 4 : Schematic diagram of the fixing fixture structure of the present invention Figure 1 ;

[0037] Attached Figure 5 : Schematic diagram of the fixing fixture structure of the present invention Figure 2 ;

[0038] Attached Figure 6: Temperature control process of the temperature control system of the present invention;

[0039] Attached Figure 7 : Schematic diagram of the control relationship principle of the temperature control system of the present invention.

[0040] Explanation of the reference numerals in the accompanying drawings: 1. PU plastic shell; 2. Polyurethane insulation layer; 3. Dry ice chamber; 4. Fan; 5. Partition; 6. Fiber Bragg grating signal line; 7. Network cable; 8. Fiber Bragg grating demodulator power line; 9. Control system power line; 10. Implementation hole; 11. Equipment room; 12. Control system; 13. First temperature sensor; 14. Fiber Bragg grating demodulator; 15. Constant temperature box cover; 16. Buckle; 17. Hinge; 18. Temperature alarm light; 19. Fixing fixture; 20. Ear piece; 21. Nut; 22. Insulation pad; 23. Limit column; 24. Ear piece support; 25. Bottom plate; 26. Second temperature sensor; 27. Fiber Bragg grating temperature sensor. DETAILED DESCRIPTION

[0041] A specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation.

[0042] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the technical solutions of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0043] See also Figure 1-Figure 7The embodiment of the present invention provides a dry ice temperature control system and method for a modem for ground testing of a rotor system. The dry ice temperature control system for a modem for ground testing of a rotor system includes a portable dry ice thermostatic box, the outer shell of the box is made of PU plastic, and a polyurethane insulation layer 2 is used to fill the outer shell and the inner cavity; the interior of the thermostatic box includes a dry ice chamber 3 and an equipment room 11, and a partition is used between the dry ice chamber 3 and the equipment room 11 to isolate the air flow in the two spaces; a first temperature sensor 13 is arranged in the equipment room; a second temperature sensor 26 is arranged in the dry ice chamber; a fiber grating demodulator 14 is placed in the equipment room 11 and fixed by a fixing fixture 19; four fixing fixtures 19 are arranged at the bottom of the thermostatic box, which are connected to the thermostatic box through nuts 21, and the thermostatic box is provided with a fixed fixture 19. The box cover is provided with 4 fixing fixtures 19, which are connected to the thermostat cover 15 through nuts; the fixing fixture 19 is composed of an ear piece 20, a nut 21, a heat insulation pad 22, a limit column 23, an ear piece support 24, and a bottom plate 25. The ear piece 20 has a central axis, and the ear piece support 24 is provided with a rotation hole. The central axis of the ear piece 20 is installed in the rotation hole. A limit column 23 is provided at the bottom of the ear piece 20. The ear piece support 20 and the limit column 23 are welded on the bottom plate 25. The surface of the ear piece 20 is paved with a heat insulation pad 22; the control system 12 is installed in the insulation layer 2 between the equipment room 11 and the shell 1; the fiber grating demodulator 14 is connected to the fiber grating signal line 6, the network cable 7, and the fiber grating demodulator power line 8, and the control system power line 9 is connected to the outside through the implementation hole. The fiber grating signal line 6 is arranged on the outer surface of the thermostat, and the fiber grating signal input line 6 is connected to the fiber grating temperature sensor 27 provided on the outer wall of the thermostat. The thermostat cover 15 is connected to the thermostat by means of a buckle 16 and a hinge 17. The control system 12 is implemented by a PLC controller.

[0044] Working principle: The device first reduces the heat exchange between the internal environment of the thermostat equipment room and the external environment through the polyurethane PU plastic shell and the insulation layer, and reduces the impact of the external high and low temperature environment on the ambient temperature in the thermostat. The dry ice in the dry ice room evaporates to form a cold source, and the air in the dry ice room is cold air with a lower temperature; the demodulator in the equipment room will generate heat when working, and combined with the constant temperature insulation layer, the impact of the low temperature environment is offset, so only the high temperature environment needs to be controlled; the temperature in the thermostat is measured by a resistive temperature sensor. When the temperature in the thermostat exceeds the specified range, the control system 12 controls the fan speed according to the temperature signal of the demodulator, the temperature sensor signal of the dry ice room and the equipment room, and controls the flow of cold air from the dry ice room to the equipment room, so as to maintain the temperature of the equipment room within the working temperature range of the demodulator. When the external environment temperature is low, the heat generated by the combined constant temperature insulation layer and the internal demodulator equipment during operation can offset the impact of the external low temperature.

[0045] When installing the demodulator, the bottom ear will be pressed down by gravity, and the ear will rotate, so that the side ear and the bottom ear will clamp the demodulator, and the horizontal movement of the demodulator will be limited by the four fixing clamps. When closing the thermostatic box cover, the demodulator will press the fixing clamps on the cover, and the horizontal movement of the demodulator will be limited by the side ear and the bottom ear of the fixing clamps. The horizontal and vertical movement of the demodulator will be limited by the joint action of the 8 fixing clamps on the box floor and the box cover. Because the fixing clamps on the box cover are rotatable, there will be no jamming when closing the thermostatic box cover.

[0046] Working process: first install the demodulator in the equipment room, and connect the power cord, network cable and fiber Bragg grating signal line of the demodulator equipment. The fiber Bragg grating temperature sensor and signal line are arranged on the outer surface of the thermostat; close the thermostat door and lock the buckle; in the high and low temperature environment, the polyurethane insulation layer will first weaken the impact of the external high and low temperature environment on the internal environment of the thermostat equipment room; the resistance temperature sensor will always detect the temperature in the thermostat, and the demodulator will always output the external environment temperature signal of the thermostat and transmit it to the control system 12. Through the control system 12, it will continuously compare with the threshold. When the temperature in the thermostat is higher than the set threshold, the control system 12 controls the fan to rotate and deliver the cold air from the dry ice room into the equipment room, and the temperature of the equipment room will be reduced until it reaches the specified value.

[0047] The temperature control process of the device is as follows Figure 6 As shown, input the target temperature that the semiconductor thermostat needs to maintain, the temperature sensors inside and outside the thermostat detect the ambient temperature and input it to the control system, and the control system determines whether the ambient temperature alarms. When the temperature of the thermostat equipment room is lower than the set temperature, the fan does not work, and the equipment room relies on the demodulator's own heat to balance the internal temperature; when the temperature of the thermostat equipment room is higher than the set temperature, the cooling fan starts to work to ensure that the temperature of the equipment room is at the target temperature.

[0048] The input and output control relationship of the temperature control system 12 of the present invention is as follows:

[0049] y(t)=μ(t)*g

[0050] μ(t)=αPID e(t) +βPID f(t)

[0051]

[0052]

[0053] e(t)=SA

[0054]

[0055] Kp =0.65K c ;

[0056] e: Temperature error inside the thermostat equipment room;

[0057] f: external temperature error of the constant temperature box;

[0058] g: refrigeration efficiency;

[0059] S: temperature setting value;

[0060] A: Temperature of the equipment room temperature sensor inside the thermostat;

[0061] B N : The temperature of the thermostat surface temperature sensor;

[0062] C N : The heat transfer coefficient of each grating position of the temperature sensor on the surface of the constant temperature box;

[0063] D: Dry ice room temperature:

[0064] t: PID control sampling calculation period

[0065] T i : Integral time of the control system

[0066] T d : Derivative time of the control system

[0067] Specifically, the temperature control method of the dry ice temperature control system of the modem for ground testing of the rotor system of the present invention comprises the following steps:

[0068] 1) Detecting the temperature data of each area according to an agreed period, the areas are the external area of ​​the thermostat corresponding to each grating in each fiber Bragg grating temperature sensor string, the equipment room corresponding to the first temperature sensor, and the dry ice room corresponding to the second temperature sensor; wherein the first temperature sensor 13 corresponds to the temperature value A of the equipment room 11 inside the thermostat, wherein the temperature value A is the temperature collected at each time node; the second temperature sensor 26 corresponds to the temperature value D of the dry ice room 3 inside the thermostat, wherein the temperature value D is the temperature collected at each time node; the fiber Bragg grating temperature sensor 27 corresponds to the external surface temperature of the thermostat; the control system 12 collects the temperature values ​​detected by each temperature sensor according to the agreed period; wherein the information collected by the fiber Bragg grating temperature sensor is analyzed and processed by the fiber Bragg grating demodulator 14 to obtain multiple temperature values ​​B N (N=1, 2, ..., 20), N is the number of gratings in the fiber Bragg grating temperature sensor 27;

[0069] 2) When receiving the signal from the resistance temperature sensor at each moment, the control system 12 determines the temperature value A inside the thermostat equipment room. When A>60°C or A<-20°C, an alarm is sounded and the alarm indicator light is on;

[0070] 3) Obtain the heat transfer coefficient C of the outer wall of the thermostat corresponding to each grating temperature sensor 27 to the environment inside the device N The method for obtaining the heat transfer coefficient is as follows: when the temperatures inside and outside the thermostat are the same, the position where the grating temperature sensor is set on the outer surface of the thermostat is heated or cooled, the surface temperature of the same part of the inner and outer walls of the thermostat is measured, and the absolute value after subtracting the inner and outer temperatures is taken. The absolute value is the heat transfer coefficient;

[0071] 4) Set the target temperature value S to be maintained in the thermostat, -20℃ <S<60℃;

[0072] 5) Determine the cooling efficiency g of the cooling fan; the cooling efficiency is determined according to the change of the temperature value D in the dry ice chamber, which is the ratio of the temperature difference between the dry ice chamber and the equipment room at the current moment to the starting moment. The initial temperature of the dry ice chamber is -20℃, -20 <D<A,0<g<1;

[0073] 6) Determine the first difference function e(t)=SA between the temperature inside the thermostat equipment room and the target temperature, where the first difference function is a function of the difference between the temperature value A inside the thermostat equipment room and the target temperature value S over time; determine the second difference function between the temperature of the outer wall of the thermostat and the target temperature The calculation method for the second difference function is as follows: first obtain the temperature value B of each grating temperature sensor N And the corresponding heat transfer coefficient C N The average value after multiplication, the difference between the average value and the target temperature as a function of time is the second difference function, and N is the number of outer wall temperature sensor gratings;

[0074] 7) Determining a first output function by the first difference function; obtaining the first output function by accumulating proportional integral calculation, integral calculation and differential calculation; Among them, K p e(t) is a proportional integral calculation, that is, the temperature difference function e(t) inside and outside the constant temperature box at time t is multiplied by a proportional gain K p ,K p =0.65K c ,K c It is a PID control system that minimizes the steady-state error of the control system 12 under the condition of using only the proportional link control. e(t) =K c K in e(t) c value; by adjusting K pCan control the speed at which the thermostat reaches the target temperature, K p The larger it is, the faster it approaches the target temperature. In the integral calculation phase, taking into account the past errors, the first difference function is integrated from the beginning to the current moment and combined with the integral gain K i multiply; t is the PID control sampling calculation period, T i is the integration time of the control system 12; The differential calculation phase, that is, taking into account the upcoming error, calculates the first derivative of the first difference function and a positive constant K d Multiply, t is the differential time of the control system 12; the three parameters are all adaptive parameters and are greater than 0; t is the independent variable of time change;

[0075] 8) Determine the second output function by the second difference function; obtain the second output function by accumulating proportional calculation, integral calculation and differential calculation Among them, the proportional calculation, integral calculation and differential calculation are all obtained based on the second difference function f(t), and the meaning and method are the same as the first output function. The three calculation links and parameter functions are the same as the first output function;

[0076] 9) Determine the output function; the output function μ(t) is obtained by adding the first function and the second function; wherein the output function μ(t) is μ(t)=αPID e(t) +βPID f(t) , where α and β are the adaptation parameters of the first output function and the second output function respectively; α is the proportional parameter corresponding to the difference between the internal ambient temperature of the equipment room and the maximum temperature difference, e is the temperature difference between the current internal ambient temperature of the constant temperature box equipment room and the set target temperature when the control system 12 samples, when the internal ambient temperature of the equipment room varies between -40°C or above 70°C, α is 1, when the internal ambient temperature of the equipment room is the same as the target temperature, α is 0; β is the proportional parameter corresponding to the difference between the external ambient temperature and the maximum temperature difference, f is the temperature difference between the current external ambient temperature and the set target temperature when the control system 12 samples, when the external ambient temperature varies between -20°C or below and 60°C or above, β is 1, when the external ambient temperature is the same as the target temperature, β is 0;

[0077] The total output function is y(t)=μ(t)*g, y≥0, which is obtained by multiplying the output function μ(t) by the refrigeration efficiency g. The purpose is to compensate for the weakening of the dry ice refrigeration effect by increasing the fan output during the temperature change of the dry ice chamber;

[0078] 10) The control system drives the refrigeration fan to rotate according to the total output y(t); by adjusting the fan voltage and thus the fan speed, the cold air in the dry ice room is transported to the equipment room, thereby reducing the ambient temperature in the equipment room.

[0079] The temperature control algorithm of the device is based on the PID algorithm. The parameters of the two temperature sensors inside and outside the thermostat are calculated by PID respectively and then superimposed. The device can adjust the cooling fan in real time according to the influence of the internal and external temperature environment to maintain the temperature environment of the thermostat in balance near the target temperature. When the equipment room is lower than the target temperature, the cooling fan stops working. The temperature control algorithm of the device is based on the PID algorithm. After setting the target temperature, the internal temperature sensor detects the internal temperature, and the detection result A is input into the control system 12 to calculate the difference function e(t) between the current internal ambient temperature and the target temperature. Substitute e(t into the PID algorithm. After superimposing the proportional algorithm, the integral algorithm and the differential algorithm, the output function required internally is obtained as PID. e(t) ; The external temperature sensor detects the external temperature and sends the detection result B N The input is sent to the control system 12, which adds an influence factor C according to the influence of each temperature sensor temperature on the interior of the constant temperature box. N And calculate the temperature difference between the external and internal environments to obtain the temperature difference function f(t). Substitute f(t) into the PID algorithm to obtain the output function PID f(t) , considering the influence of internal heat source and external heat source / cold source on the internal temperature environment, the total output of the heating and cooling system is μ(t) by superimposing the two output functions. K p , K i , K d The parameters are determined through repeated tests. The dry ice room temperature sensor is used to obtain the current dry ice room temperature difference function. At this time, the fan speed y(t) is a function of the total output and the dry ice room temperature difference. The fan rotates, and the cold air is input into the equipment room to reduce the equipment room temperature. The control relationship principle block diagram of the temperature control system of the present invention is as follows: Figure 7 shown.

[0080] The above disclosures are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A dry ice temperature control system for modems used for ground testing of rotor systems, characterized in that: The invention comprises a portable dry ice thermostat, a fiber Bragg grating demodulator (14) and a control system (12), wherein the thermostat comprises a dry ice chamber (3) and an equipment chamber (11), a partition is used between the dry ice chamber (3) and the equipment chamber (11) to isolate the air flow in the two spaces, and a cooling fan (4) is arranged on the partition; a first temperature sensor (13) is arranged in the equipment chamber (11); a second temperature sensor (26) is arranged in the dry ice chamber (3); the fiber Bragg grating demodulator (14) is arranged in the equipment chamber (11); the control system (12) is arranged in a heat preservation layer (2) arranged on the side wall of the equipment chamber (11); the fiber Bragg grating demodulator (14) is connected to a fiber Bragg grating signal input line (6), and the fiber Bragg grating signal input line (6) is connected to a fiber Bragg grating temperature sensor (27) arranged on the outer wall of the thermostat; The temperature control method of the dry ice temperature control system of the modem used for the ground test of the rotor system is characterized by comprising the following steps: 1) Detecting temperature data of each area at an agreed period, wherein the areas are three areas: an external area of ​​a thermostatic box corresponding to each grating in each fiber Bragg grating temperature sensor string, an equipment room corresponding to the first temperature sensor, and a dry ice room corresponding to the second temperature sensor; wherein the first temperature sensor (13) corresponds to a temperature value A of the equipment room (11) inside the thermostatic box, wherein the temperature value A is the temperature collected at each time node; the second temperature sensor (26) corresponds to a temperature value D of the dry ice room (3) inside the thermostatic box, wherein the temperature value D is the temperature collected at each time node; the fiber Bragg grating temperature sensor (27) corresponds to the external surface temperature of the thermostatic box; the control system (12) collects the temperature values ​​detected by each temperature sensor at an agreed period; wherein the information collected by the fiber Bragg grating temperature sensor is analyzed and processed by a fiber Bragg grating demodulator (14) to obtain a plurality of temperature values ​​B N (N=1, 2, ..., 20), N is the number of gratings in the fiber Bragg grating temperature sensor (27); 2) When receiving the signal from the resistance temperature sensor at each moment, the control system (12) determines the temperature value A inside the thermostat equipment room. When A>60°C or A<-20°C, an alarm is sounded and the alarm indicator light is on; 3) Obtain the heat transfer coefficient C of the outer wall of the constant temperature box corresponding to each grating temperature sensor (27) to the environment inside the device N The method for obtaining the heat transfer coefficient is as follows: when the temperatures inside and outside the thermostat are the same, the position where the grating temperature sensor is set on the outer surface of the thermostat is heated or cooled, the surface temperature of the same part of the inner and outer walls of the thermostat is measured, and the absolute value after subtracting the inner and outer temperatures is taken. The absolute value is the heat transfer coefficient; 4) Set the target temperature value S to be maintained in the thermostat, -20℃ <S<60℃; 5) Determine the cooling efficiency g of the cooling fan; the cooling efficiency is determined according to the change of the temperature value D in the dry ice chamber, which is the ratio of the temperature difference between the dry ice chamber and the equipment room at the current moment to the starting moment. The initial temperature of the dry ice chamber is -20℃, -20 <D<A,0<g<1; 6) Determine the first difference function e(t)=SA between the temperature inside the thermostat equipment room and the target temperature, where the first difference function is a function of the difference between the temperature value A inside the thermostat equipment room and the target temperature value S over time; determine the second difference function between the temperature of the outer wall of the thermostat and the target temperature The calculation method for the second difference function is as follows: first obtain the temperature value B of each grating temperature sensor N And the corresponding heat transfer coefficient C N The average value after multiplication, the difference between the average value and the target temperature as a function of time is the second difference function, and N is the number of outer wall temperature sensor gratings; 7) Determining a first output function by the first difference function; obtaining the first output function by accumulating proportional integral calculation, integral calculation and differential calculation; Among them, K p e(t) is a proportional integral calculation, that is, the temperature difference function e(t) inside and outside the constant temperature box at time t is multiplied by a proportional gain K p ,K p =0.65K c ,K c It is a PID control system that minimizes the steady-state error of the control system (12) under the condition of using only proportional control. e(t) =K c K in e(t) c By adjusting K p Can control the speed at which the thermostat reaches the target temperature, K p The larger it is, the faster it approaches the target temperature. In the integral calculation phase, taking into account the past errors, the first difference function is integrated from the beginning to the current moment and combined with the integral gain K i multiply; t is the PID control sampling calculation period, T i is the integration time of the control system (12); The differential calculation phase, that is, taking into account the upcoming error, calculates the first derivative of the first difference function and a positive constant K d Multiply, is the differential time of the control system (12); the three parameters are all adaptive parameters and are greater than 0; t is the independent variable of time variation; 8) Determine the second output function by the second difference function; obtain the second output function by accumulating proportional calculation, integral calculation and differential calculation Among them, the proportional calculation, integral calculation and differential calculation are all obtained based on the second difference function f(t), and the meaning and method are the same as the first output function. The three calculation links and parameter functions are the same as the first output function; 9) Determine the output function; the output function μ(t) is obtained by adding the first function and the second function; wherein the output function μ(t) is μ(t)=αPID e(t) +βPID f(t) , where α and β are the adaptation parameters of the first output function and the second output function respectively; 0<α<1, 0<β<1, α is the proportional parameter corresponding to the difference between the ambient temperature inside the equipment room and the maximum temperature difference of 40°C, e is the temperature difference between the ambient temperature inside the equipment room of the current constant temperature box and the set target temperature when the control system (12) is sampled, when the ambient temperature inside the equipment room varies between -40°C or above 70°C, α is 1, when the ambient temperature inside the equipment room is the same as the target temperature, α is 0; β is the proportional parameter corresponding to the difference between the external ambient temperature and the maximum temperature difference of 55°C, f is the temperature difference between the current external ambient temperature and the set target temperature when the control system (12) is sampled, when the external ambient temperature varies between -20°C or below and above 60°C, β is 1, when the external ambient temperature is the same as the target temperature, β is 0; The total output function is y(t)=μ(t)*g, y≥0, which is obtained by multiplying the output function μ(t) by the refrigeration efficiency g. The purpose is to compensate for the weakening of the dry ice refrigeration effect by increasing the fan output during the temperature change of the dry ice chamber; 10) The control system drives the refrigeration fan to rotate according to the total output y(t); by adjusting the fan voltage and thus the fan speed, the cold air in the dry ice room is transported to the equipment room, thereby reducing the ambient temperature in the equipment room.

2. The dry ice temperature control system for modem used for ground testing of rotor systems according to claim 1, characterized in that: The dry ice chamber (3) and the equipment chamber (11) are located inside the PU plastic shell (1); the thermal insulation layer (2) is located between the side wall of the equipment chamber (11) and the PU plastic shell (1); and the thermal insulation layer (2) is a polyurethane thermal insulation layer.

3. The dry ice temperature control system for modem used for ground testing of rotor systems according to claim 1, characterized in that: The fiber grating demodulator (14) is arranged in the equipment room (11) via a fixing fixture (19).

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