Virtual Automotive Cabin Humidity Sensor Method and System

Abstract

The present invention provides a virtual vehicle cabin humidity sensor method and system, including the following steps: a step of establishing a carriage humidity equation: on the internal volume of the vehicle carriage, a ordinary differential equation is established according to the mass conservation of water vapor to obtain a carriage water vapor mass conservation equation; a step of obtaining the absolute humidity inside the vehicle: inputting conditions, solving the carriage water vapor mass conservation equation, and obtaining the absolute humidity inside the carriage; a step of obtaining humidity parameters: combining the absolute humidity inside the carriage with the air temperature inside the vehicle to calculate the air humidity parameters inside the vehicle. The present invention provides a virtual humidity sensor method that uses a mathematical model to calculate and predict the humidity inside the vehicle. The use of this method can effectively solve the problems of increasing the number of components and raising the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of virtual humidity sensors, and in particular to a method and system for a virtual automobile cabin humidity sensor. Background Art

[0002] The air temperature and humidity in the car determine the thermal comfort of the passengers, so the car air conditioning system focuses on ensuring that the temperature and humidity in the car are within a certain reasonable range. Generally speaking, the human body is more comfortable in an ambient temperature range of 22℃ to 27℃ and a relative humidity range of 40% to 60%.

[0003] The humidity inside the car not only has a great impact on the comfort of passengers, but more importantly, it also plays a decisive role in the safe driving of the car. Under certain ambient temperature, humidity and humidity inside the car, the temperature of the car's front window glass will drop below the dew point of the air inside the car, causing the water vapor in the air to condense on the inner surface of the glass to form a fog layer, making the glass lose its transparency. Obviously, this is very detrimental to safe driving, so the defrosting and defogging ability of the air conditioning system is regulated by automobile safety regulations. During the development of the air conditioning system, there are special experimental procedures to evaluate the defrosting and defogging ability of the air conditioning system. Those with low defrosting and defogging efficiency must be redeveloped and improved until they meet the standards.

[0004] Today, the mileage anxiety of new energy vehicles is an important factor that restricts their acceptance in the market. The air conditioning system of electric vehicles has a great impact on mileage. In summer, the mileage can be reduced by about 20% due to the use of the air conditioning system, while in winter, the mileage loss caused by the heating in the car can be as high as 50% at -20℃. In order to reduce the impact of air conditioning and heating on mileage, automotive thermal system suppliers have made great efforts to improve the energy efficiency caused by automotive thermal comfort and help reduce mileage anxiety. In order to increase the market acceptance of electric vehicles and contribute to environmental protection, among the measures taken, increasing the use share of air conditioning intake internal circulation is the preferred technology to improve the efficiency of the HVAC system because it is simple and easy to operate, and only the position of the air intake valve needs to be electronically controlled. However, the use of the largest share of internal circulation will cause the humidity in the car to rise rapidly, and is restricted by the thermal comfort needs of the human body and the fogging of the front window glass.

[0005] In order to ensure the comfort of the car, reduce the risk of fogging, and maximize the energy efficiency of the HVAC system, automobile OEMs generally introduce in-car humidity sensors in electric vehicles and high-end cars to monitor the humidity in the car, thereby effectively ensuring the comprehensive optimization of comfort, safety and energy efficiency. In terms of installation, the humidity sensor is either integrated into the automatic air conditioning temperature sensor or the front window dew point sensor of the automatic defog system.

[0006] The Chinese invention patent document with the publication number CN107244212A discloses a defrosting control method for a heat pump type electric vehicle air conditioner based on humidity sensor technology. The method includes the following steps: collecting the ambient humidity H during vehicle driving through a temperature and humidity sensor amb , the ambient temperature T amb , and the surface temperature T of the outdoor heat exchanger fins EVAP , and saving the collected data once every set interval time T set ; judging whether the current vehicle driving environment is in the general frosting area or the heavy frosting area in the theoretical frosting area of the air source heat pump according to the ambient humidity H amb and the ambient temperature T amb . If so, execute the next step; if not, return to the previous step; execute the defrosting action for a duration of ΔT; judge whether the current surface temperature T of the outdoor heat exchanger fins EVAP is greater than 0°C. If so, the defrosting control ends; if not, return to the previous step.

[0007] Regarding the above-mentioned prior art, the inventor believes that the introduction of the humidity sensor has led to an increase in the number of automotive parts and the cost. Summary of the Invention

[0008] Aiming at the defects in the prior art, the purpose of the present invention is to provide a virtual vehicle cabin humidity sensor method and system.

[0009] A virtual vehicle cabin humidity sensor method provided by the present invention includes the following steps:

[0010] Step of establishing the carriage humidity equation: On the internal volume of the vehicle carriage, establish an ordinary differential equation according to the law of conservation of water vapor mass to obtain the carriage water vapor mass conservation equation;

[0011] Step of obtaining the absolute humidity inside the vehicle: Input the conditions, solve the carriage water vapor mass conservation equation, and calculate and obtain the absolute humidity inside the carriage;

[0012] Step of obtaining humidity parameters: Combine the absolute humidity inside the carriage with the air temperature inside the carriage to calculate the air humidity parameters inside the carriage.

[0013] Preferably, in the step of establishing the carriage humidity equation, on the internal volume of the vehicle carriage, establish an ordinary differential equation containing a time derivative according to the conservation of water vapor mass to obtain the carriage water vapor mass conservation equation;

[0014] In the step of obtaining the absolute humidity inside the vehicle, solve the carriage water vapor mass conservation equation according to relevant boundary conditions and initial conditions to obtain the absolute humidity inside the carriage at any time;

[0015] In the step of obtaining the humidity parameter, the absolute humidity inside the vehicle compartment is combined with the air temperature inside the vehicle to calculate the relative humidity and the dew point inside the vehicle.

[0016] Preferably, in the step of obtaining the absolute humidity inside the vehicle, the relevant boundary conditions are: taking the air volume inside the vehicle compartment as the control volume and the vehicle compartment shell containing the air volume inside the vehicle compartment as the control volume boundary, then any flow-related parameters of the moist air crossing the control volume boundary are the boundary conditions for solving the water vapor mass conservation equation;

[0017] The initial conditions include the humidity condition of the air inside the vehicle when the vehicle engine is started.

[0018] Preferably, the relevant boundary conditions include the ambient temperature, the ambient humidity, the air temperature inside the vehicle, the proportion of the in-vehicle air circulation, the intrusion flow rate into the vehicle compartment, the air temperature at the evaporator outlet, the exhaust flow rate of the air conditioner box, and the exhaust flow rate of the vehicle compartment of the vehicle.

[0019] The relevant boundary conditions also include other conditions, and the other conditions include the number of people inside the vehicle and the moisture sources related to the weather.

[0020] Preferably, the method further includes a step of obtaining the vehicle compartment temperature: obtaining the data of the in-vehicle temperature sensor of the vehicle automatic air conditioner through the in-vehicle communication network.

[0021] Preferably, in the step of establishing the vehicle compartment humidity equation, there is moist air flowing in and out of the vehicle compartment control volume and in-vehicle moisture sources, and the mass change rate of water vapor in the control volume is expressed by the following balance relationship

[0022]

[0023] Among them, m v,cab represents the total mass of water vapor inside the vehicle compartment; t represents time; V cab represents the internal volume of the vehicle compartment; ρ v,cab represents the absolute humidity inside the vehicle compartment; represents the volume flow rate of the air conditioner box exhaust entering the vehicle compartment; ρ v,hvac represents the absolute humidity of the air conditioner box exhaust entering the vehicle compartment; represents the in-circulation air flow rate; represents the exhaust flow rate of the rear exhaust port of the vehicle compartment; represents the other leakage flow rate of the vehicle; n p represents the number of people inside the vehicle; represents the average moisture amount generated by each person; represents the moisture amount generated by other in-vehicle moisture sources;

[0024] The change rate of the total amount of water vapor in the carriage is determined by the difference between the total mass flow rate of water vapor entering the carriage per unit time and the amount of water vapor generated in the carriage per unit time, and the total mass flow rate of water vapor overflowing outside the carriage per unit time; if the total inflow of water vapor is greater than the total outflow, the total amount of water vapor retained in the carriage increases, resulting in a positive change rate; if the total inflow of water vapor is less than the total outflow, the total amount of water vapor retained in the carriage decreases, resulting in a negative change rate.

[0025] Given that the exhaust, air leakage, and internal circulation air flow of the carriage satisfy the following conservation equations:

[0026]

[0027] Equation (1) is simplified to

[0028]

[0029] In Equation (3), ρ v,cab is the variable to be solved, and ρ v,hvac is the input variable; if ρ v,hvac is known or expressed in terms of known variables, then Equation (3) is solved as an ordinary differential equation using numerical algorithms.

[0030] Preferably, in the step of obtaining the absolute humidity in the carriage, determine the exhaust humidity of the air conditioning box:

[0031] The air discharged from the air conditioning box into the carriage is a mixture of the cold air from the evaporator and the warm air from the heater. The warm air is obtained by partially heating the cold air from the evaporator. The absolute humidity discharged into the carriage is determined by the humidity of the air flow at the outlet of the evaporator; in order to establish the calculation formula for the air humidity at the outlet of the evaporator, first determine the absolute humidity at the inlet of the evaporator.

[0032] The air entering the evaporator consists of two air flows: one is the internal circulation air flow extracted by the air conditioning box from the carriage, and the other is the external air drawn in by the air conditioning box through the external air intake; the absolute humidity after the mixing of the two air flows is obtained from Equation (4):

[0033]

[0034] where ρ v,eia represents the absolute humidity of the air at the inlet of the evaporator; ρ v，oa represents the absolute humidity of the external air drawn in by the external air intake of the air conditioning box; represents the volume flow rate of the external air drawn in by the external air intake of the air conditioning box; represents the volume of the internal circulation air flow extracted by the air conditioning box from the carriage;

[0035] The internal circulation rate of the air conditioning air flow is defined by Equation (5):

[0036]

[0037] Among them, RR represents the proportion of the air conditioner's internal circulation;

[0038] The air temperature and absolute humidity at the evaporator inlet are determined by equations (6) and (7) according to the conservation of energy and mass:

[0039] T eia = T oa (1 - RR) + T cab RR (6)

[0040] ρ v,eia = ρ v,oa (1 - RR) + ρ v，cab RR (7)

[0041] Among them, T eia represents the temperature of the air at the evaporator inlet; T oa represents the temperature of the outside air; T cab represents the temperature of the air inside the vehicle compartment; ρ v，oa represents the absolute humidity of the outside air;

[0042] The partial pressure of water vapor and the air dew point temperature at the evaporator inlet are calculated by the ideal gas state equation (8) and the water vapor saturation curve equation (9) respectively:

[0043] P v，eia = ρ v，eia RT eia (8)

[0044] T d，eia = T s (P v，eia ) (9)

[0045] Among them, P v，eia represents the partial pressure of the water vapor component of the air at the evaporator inlet; R represents the ideal gas constant of water vapor; T d，eia represents the air dew point temperature at the evaporator inlet; T s (P v，eia ) represents the saturation temperature at the partial pressure of the water vapor of the air at the evaporator inlet;

[0046] The evaporator of the air conditioning system absorbs the heat energy of the incoming air and reduces the temperature; if the outlet air temperature of the evaporator drops below the dew point, the moisture in the air flow will condense and precipitate, and the absolute humidity of the air flow will decrease;

[0047] Judge whether the outlet air temperature is lower than the inlet air dew point or higher than the inlet air dew point;

[0048] If the outlet air temperature is higher than the inlet air dew point, no water vapor condensation occurs in the evaporator, and the absolute humidity of the outlet air is equal to the absolute humidity of the inlet air;

[0049] If the outlet air temperature is lower than the inlet air dew point, there must be condensate in the evaporator, and the outlet air is in a saturated state at the outlet air temperature.

[0050] Preferably, in the step of obtaining the absolute humidity inside the vehicle, an outlet air temperature sensor is provided at the outlet of the evaporator; according to the sensor reading and the temperature control target value, the air-conditioning control system adjusts the compressor speed or the compressor displacement to keep the evaporator in the correct operating state.

[0051] Based on the outlet air temperature sensor, determine whether the outlet air temperature is higher than or lower than the inlet air dew point.

[0052] If the outlet air temperature is higher than the inlet air dew point, the following condition is satisfied:

[0053] T eoa >T d，eia (10)

[0054] wherein, T eoa represents the outlet air temperature of the evaporator;

[0055] It is known that there is no condensation in the evaporator, and at this time the absolute humidity of the outlet air is equal to the absolute humidity of the inlet air:

[0056] ρ v,eoa =ρ v,eia =ρ v,oa (1-RR)+ρ v,cab RR (11)

[0057] wherein, ρ v,eoa represents the absolute humidity of the outlet air of the evaporator;

[0058] Obtain the absolute humidity of the air exhausted from the air-conditioning box to the compartment:

[0059] ρ v,hvac =ρ v,oa (1-RR)+ρ v,cab RR (12)

[0060] If the evaporator cools the air flow below the dew point of the inlet air, the condition of Equation (13) is satisfied:

[0061] T eoa <T d，eia (13)

[0062] The evaporator cools the air below the dew point of the inlet air temperature, and condensation occurs in the evaporator. At this time, the outlet air of the evaporator is in a saturated state; therefore, the partial pressure of water vapor in the outlet air is determined according to the outlet air temperature sensor reading and the vapor saturation curve:

[0063] P v，eoa =P s (T eoa) (14)

[0064] Among them, P v，eoa represents the water vapor partial pressure of the air at the outlet of the evaporator; P s (T eoa ) represents the saturated water vapor pressure curve; the absolute humidity of the outlet air is obtained based on the vapor partial pressure of the outlet air, that is, the absolute humidity of the air discharged from the air conditioning box to the carriage is obtained, and it is determined according to the ideal gas equation:

[0065]

[0066] Preferably, in the step of obtaining the absolute humidity inside the vehicle, according to the absolute humidity of the air discharged from the air conditioning box to the carriage, Equation (3) becomes an ordinary differential equation to be solved;

[0067] Corresponding to the two working conditions of evaporator dehumidification and non-dehumidification, the ordinary differential equation of absolute humidity takes different forms:

[0068] In the non-dehumidification working condition, the form of the ordinary differential equation is shown by Equation (16):

[0069]

[0070] In the evaporator dehumidification working condition, the ordinary differential equation takes the form of Equation (17):

[0071]

[0072] According to a virtual vehicle cabin humidity sensor system provided by the present invention, a method for applying a virtual vehicle cabin humidity sensor includes the following modules:

[0073] Carriage humidity equation establishment module: On the internal volume of the vehicle carriage, an ordinary differential equation is established according to the mass conservation of water vapor to obtain the carriage water vapor mass conservation equation;

[0074] Internal vehicle absolute humidity acquisition module: Input conditions, solve the carriage water vapor mass conservation equation, and obtain the internal vehicle absolute humidity inside the carriage;

[0075] Humidity parameter acquisition module: Combine the internal vehicle absolute humidity inside the carriage with the internal vehicle air temperature to calculate the air humidity parameters inside the carriage.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] 1. The present invention provides a virtual humidity sensor method that uses a mathematical model to calculate and predict the humidity inside the vehicle. The use of this method can effectively solve the problems of increasing the number of components and raising the cost;

[0078] 2. The virtual humidity sensor provided by the present invention can provide input parameters for the automatic defogging system of the car compartment, improving driving safety.

[0079] 3. The virtual humidity sensor provided by the present invention can provide input parameters for the automatic air conditioning system of the car compartment, introduce the function of in-vehicle humidity management, and increase passenger comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0081] Figure 1 It is a structural diagram of the virtual humidity sensor system;

[0082] Figure 2 It is a diagram of the wet air flowing in and out of the car compartment control body and the in-vehicle moisture source;

[0083] Figure 3 It is a parallel simulation architecture diagram of the virtual humidity and virtual temperature sensors in the car;

[0084] Figure 4 It is a symbol definition diagram of the virtual humidity sensor;

[0085] Figure 5 It is an application example of the virtual humidity sensor: in-vehicle air conditioner dehumidification diagram;

[0086] Figure 6 It is an application example of the virtual humidity sensor: picking up passengers on a rainy day diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0087] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0088] An embodiment of the present invention discloses a method for a virtual humidity sensor in a car cabin, as Figure 1 shown, including the following steps: The step of establishing the car cabin humidity equation: On the internal volume of the car cabin, a ordinary differential equation is established according to the law of conservation of water vapor mass, and the car cabin water vapor mass conservation equation is obtained. That is, on the internal volume of the car cabin, an ordinary differential equation containing the time derivative is established according to the conservation of water vapor to obtain the car cabin water vapor mass conservation equation.

[0089] Steps for obtaining the absolute humidity inside the vehicle: Given the input conditions, solve the mass conservation equation of water vapor in the vehicle compartment to calculate and obtain the absolute humidity inside the vehicle. That is, solve the mass conservation equation of water vapor in the vehicle compartment according to relevant boundary conditions and initial conditions to obtain the absolute humidity inside the vehicle at any time.

[0090] Steps for obtaining humidity parameters: Combine the absolute humidity inside the vehicle with the air temperature inside the vehicle to calculate the air humidity parameters inside the vehicle. That is, combine the absolute humidity inside the vehicle with the air temperature inside the vehicle to calculate the relative humidity and dew point inside the vehicle.

[0091] Steps for obtaining the vehicle compartment temperature: Obtain the data of the in-vehicle temperature sensor of the automotive automatic air conditioner through the in-vehicle communication network.

[0092] It can also be expressed in this way: The virtual vehicle cabin humidity sensor system essentially establishes an ordinary differential equation containing the time derivative based on the mass conservation of water vapor in the internal volume of the vehicle compartment, and then solves this equation according to relevant boundary conditions and initial conditions, thus obtaining the absolute humidity inside the vehicle at any time. This absolute humidity can then be combined with the air temperature inside the vehicle to calculate the relative humidity, dew point, and other air humidity parameters (in the attached table) inside the vehicle.

[0093] Regarding the relevant boundary conditions, the air volume inside the vehicle compartment is used as the control volume, and the vehicle compartment shell containing the air volume inside the vehicle compartment is used as the control volume boundary. Then, any flow-related parameters of the moist air passing through the control volume boundary are the boundary conditions for solving the mass conservation equation of water vapor; the initial conditions include the humidity condition of the air inside the vehicle when the vehicle engine is started. The boundary conditions include the ambient temperature, ambient humidity, air temperature inside the vehicle, air-conditioning internal circulation ratio, vehicle compartment intrusion flow rate, air temperature at the evaporator outlet, air-conditioning box exhaust flow rate, and exhaust flow rate of the vehicle compartment; the relevant boundary conditions also include other conditions, and the other conditions include the number of people inside the vehicle and weather-related moisture sources.

[0094] Figure 1 Shows the basic structure diagram of the virtual sensor system. It can be seen that the core functional module of this system is the mass conservation equation inside the vehicle compartment. To solve this equation to obtain the transient humidity parameters inside the vehicle, it is still necessary to provide the boundary conditions that affect the humidity change inside the vehicle. Using the air volume inside the vehicle compartment as the control volume and the vehicle compartment shell containing this volume as the control volume boundary, as Figure 2 shown, then any flow-related parameters of the moist air passing through this boundary can be considered as the boundary conditions for solving this equation. Specifically, these boundary conditions include the ambient temperature, humidity, air temperature inside the vehicle, air-conditioning internal circulation ratio, air flow rate intruding into the vehicle compartment through sealing defects ( ignoring the positive pressure in the vehicle compartment), and the air flow rate of the air-conditioning dehumidified air provided by the air-conditioning box to the vehicle compartment ( The mass flow rate of the air discharged from the air conditioner box into the vehicle compartment, and the exhaust flow rate of the vehicle compartment (a dedicated exhaust port is provided above the rear wheels of the compartment). Other conditions include the number of people in the vehicle and weather-related moisture sources, such as water accumulation and snow on shoes. Although strictly speaking these are not boundary conditions, it does no harm to treat them as boundary conditions.

[0095] That is, the relevant boundary conditions include the ambient temperature, ambient humidity, the temperature of the air inside the vehicle (compartment temperature), the proportion of the in-vehicle air circulation (the proportion of the internal air circulation), the intrusion flow rate of the compartment (the air flow rate intruding into the compartment through sealing defects), the air flow rate of the air-conditioning dehumidified air provided by the air conditioner box to the compartment, the air temperature at the outlet of the evaporator, and the exhaust flow rate of the vehicle compartment;

[0096] The relevant boundary conditions also include other conditions, and the other conditions include the number of people in the vehicle (the number of passengers and the number of drivers) and weather-related moisture sources (moisture sources inside the vehicle).

[0097] The solution of the virtual humidity sensor equation also requires suitable initial conditions. The initial conditions refer to the humidity condition of the air inside the vehicle when the passengers get on and the engine starts. Generally speaking, if the vehicle is parked for a long enough time, such as parked in a parking lot for more than 5 to 6 hours, it can be considered that the humidity environment inside the vehicle has reached an equilibrium state with the humidity environment outside the vehicle. Therefore, the absolute humidity outside the vehicle can be used as the initial condition inside the vehicle. If the vehicle only makes a short stop, such as staying at a gas station for 10 minutes, the humidity condition when the vehicle is turned off can be used as the initial condition to restart the simulation. For some special situations, such as water accumulation in the air conditioner box, rainy and snowy days, etc., specific situations need to be treated specifically. This is not difficult for ordinary professionals in the industry.

[0098] As Figure 3 shown, it should be noted that although the present invention takes the virtual humidity sensor as the main invention implementation case, the additional implementation cases of the present invention can include the function of the virtual temperature sensor. As Figure 3 shown, by adding the air energy conservation equation to the core module, in the case of no in-vehicle air temperature sensor, the present invention can simultaneously simulate the humidity and temperature inside the vehicle, so it can simultaneously replace the hardware of the in-vehicle temperature and humidity sensors.

[0099] To further illustrate the specific composition and method of the present invention, Figure 4 a list of the symbols used is provided. As Figure 4 shown.

[0100] Compartment humidity equation:

[0101] Refer to Figure 2 the inflow and outflow of moist air in the compartment control volume and the moisture source inside the vehicle. The mass change rate of water vapor in the control volume can be expressed by the following balance relationship

[0102]

[0103] That is to say, the change rate of the total amount of water vapor in the carriage is determined by the difference between the total amount of the mass flow rate of water vapor entering the carriage and the amount of water vapor generated inside the carriage per unit time and the total mass flow rate of water vapor overflowing outside the carriage. If the total inflow of water vapor is greater than the total outflow, the total amount of water vapor retained in the carriage will increase, resulting in a positive change rate, and vice versa. Among them, m v,cab represents the total mass of water vapor in the carriage; t represents time; V cab represents the internal volume of the carriage; ρ v,cab represents the absolute humidity in the carriage; represents the volume flow rate of the air-conditioning box exhaust entering the carriage; ρ v,hvac represents the absolute humidity of the air-conditioning box exhaust entering the carriage; represents the volume flow rate of the air extracted by the air-conditioning box from the carriage, that is, the internal circulation flow rate of the air-conditioning. represents the exhaust flow rate of the rear exhaust port of the carriage; represents other leakage flow rates of the vehicle, such as the leakage flow rate caused by poor sealing of doors and windows. n p represents the number of people in the vehicle; represents the average amount of moisture generated by each person; represents the amount of moisture generated by other moisture sources inside the vehicle.

[0104] If the air-conditioning system is reasonably designed, generally speaking, the air pressure in the carriage is positive pressure. Therefore, the air flow rate of outside air flowing in through the door gap or other gaps is not considered in the equation.

[0105] Given that the exhaust, air leakage, and internal circulation air flow rates of the carriage satisfy the following conservation equation (ignoring the change in air density caused by temperature change),

[0106]

[0107] Equation (1) can be simplified to,

[0108]

[0109] In equation (3), ρ v,cab is the variable to be solved, and ρ v,hvac is the input variable. If ρ v,hvac is known or can be expressed by known variables, then equation (3) can be solved as an ordinary differential equation using numerical algorithms.

[0110] In equation (3), the term represents the amount of moisture generated by n p passengers. In specific applications, the specific situations such as the driver and other passengers, adults and children can be distinguished for accurate expression, thereby improving the quality of modeling.

[0111] In Equation (3), This term represents other moisture sources inside the vehicle and can be used to describe various special situations, such as the moisture brought into the vehicle by passengers during precipitation, or the instantaneous increase in moisture caused by temporarily opening the door or window during vehicle operation. A more accurate treatment can model this term and use the in-vehicle flow field and temperature field to determine the evaporation rate of moisture.

[0112] Determination of the humidity of the air discharged from the air-conditioning box:

[0113] Although the air discharged from the air-conditioning box into the passenger compartment is a mixture of the cold air from the evaporator and the warm air from the heater, since the warm air is only obtained by heating a part of the cold air from the evaporator, from the perspective of absolute humidity, the absolute humidity discharged into the passenger compartment is completely determined by the air flow at the outlet of the evaporator. In order to establish a calculation method for the air humidity at the outlet of the evaporator, the absolute humidity at the inlet of the evaporator is first established here.

[0114] The air entering the evaporator consists of two airflows: one is the internal circulation airflow extracted by the air-conditioning box from the passenger compartment, and the other is the external air drawn in through the air intake of the air-conditioning box. The absolute humidity after the mixing of the two airflows can be obtained from Equation (4):

[0115]

[0116] where ρ v,eia represents the absolute humidity of the air at the inlet of the evaporator; ρ v,oa represents the absolute humidity of the external air drawn in through the external air intake of the air-conditioning box; represents the volume flow rate of the external air drawn in through the external air intake of the air-conditioning box; represents the volume of the internal circulation airflow extracted by the air-conditioning box from the passenger compartment.

[0117] Ignoring the difference in air density, the in-vehicle air circulation rate can be defined by Equation (5):

[0118]

[0119] where RR represents the in-vehicle air circulation ratio.

[0120] Then the air temperature and absolute humidity at the inlet of the evaporator can be determined by Equations (6) and (7) according to the conservation of energy and mass:

[0121] T eia = T oa (1 - RR)+ T cab RR (6)

[0122] ρ v，eia = ρ v，oa (1 - RR)+ ρ v，cab RR (7)

[0123] Among them, T eia represents the temperature of the air at the inlet of the evaporator; T oa represents the temperature of the outside air; T cab represents the temperature of the air inside the vehicle compartment; ρ v，oa represents the absolute humidity of the outside air.

[0124] Correspondingly, the partial pressure of water vapor at the evaporator inlet and the air dew point temperature can be calculated by the ideal gas state equation (8) and the water vapor saturation curve equation (8) respectively:

[0125] P v，ei a = ρ v，eia R T eia (8)

[0126] T d，eia = T s (P v，eia ) (9)

[0127] Among them, P v，eia represents the partial pressure of water vapor component of the air at the evaporator inlet; R represents the ideal gas constant of water vapor; T d，eia represents the air dew point temperature at the evaporator inlet; T s (P v，eia ) represents the saturation temperature at the partial pressure of water vapor of the air at the evaporator inlet.

[0128] The basic function of the evaporator of the air conditioning system is to absorb the heat energy of the incoming air to reduce its temperature. If the outlet air temperature of the evaporator drops below the dew point, the moisture in the air flow will condense and precipitate, and the absolute humidity of the air flow will decrease. Therefore, a primary judgment is whether the outlet air temperature is lower than or higher than the inlet air dew point. If the outlet air temperature is higher than the inlet air dew point, then no water vapor condensation occurs in the evaporator, and the absolute humidity of the outlet air is equal to that of the inlet air. On the contrary, if the outlet air temperature is lower than the inlet air dew point, then there must be condensed water in the evaporator, and the outlet air must be in a saturated state at the outlet air temperature.

[0129] Generally, in order to control the refrigeration capacity of the air conditioning system and prevent the evaporator from frosting and icing, an outlet air temperature sensor is set at the outlet of the evaporator. According to the sensor reading and the temperature control target value, the air conditioning control system will adjust the compressor speed or the compressor displacement to ensure that the evaporator is in the correct working state.

[0130] Based on the outlet air temperature sensor, the judgment on whether the outlet air temperature is higher or lower than the inlet air dew point can be completed. If it is higher than the inlet air dew point, that is, the following condition holds:

[0131] T eoa > T d，eia (10)

[0132] Among them, T eoa represents the air temperature at the outlet of the evaporator.

[0133] It can be known that no condensation occurs in the evaporator. At this time, the absolute humidity of the outlet air is equal to the absolute humidity of the inlet air:

[0134] ρ v,eoa = ρ v,eia = ρ v,oa (1 - RR) + ρ v,cab RR (11)

[0135] Among them, ρ v，eoa represents the absolute humidity of the air at the outlet of the evaporator.

[0136] Therefore, we can obtain the absolute humidity of the air exhausted from the air handling unit to the carriage:

[0137] ρ v,hvac = ρ v，oa (1 - RR) + ρ v,caB RR (12)

[0138] In the second case, the evaporator cools the air flow below the dew point of the inlet air, that is, it satisfies the condition of equation (13):

[0139] T eoa <T d，eia (13)

[0140] It can be known that the evaporator cools the air below the dew point of the inlet air temperature, and condensation occurs in the evaporator. At this time, the air at the outlet of the evaporator is in a saturated state. Therefore, the partial pressure of water vapor in the outlet air can be determined according to the reading of the outlet air temperature sensor and the steam saturation curve:

[0141] P v，eoa = P s (T eoa ) (14)

[0142] Among them, P v，eoa represents the partial pressure of water vapor in the air at the outlet of the evaporator; P s (T eoa ) represents the saturated water vapor pressure curve.

[0143] With the partial pressure of water vapor in the outlet air, the absolute humidity of the outlet air, that is, the absolute humidity of the air exhausted from the air handling unit to the carriage, can be directly determined according to the ideal gas equation:

[0144]

[0145] The absolute humidity of the carriage can solve the ordinary differential equation:

[0146] The absolute humidity of the air discharged from the air conditioner box to the passenger compartment is determined, and Equation (3) then becomes an ordinary differential equation that can be solved. Corresponding to the two operating conditions of the evaporator with and without dehumidification, the ordinary differential equation for absolute humidity also takes two different forms. In the non-dehumidification operating condition, the form of the solvable equation is shown in Equation (16):

[0147]

[0148] In the evaporator dehumidification operating condition, the solvable equation takes the form of Equation (17):

[0149]

[0150] Specific determination of boundary conditions:

[0151] To accurately predict the humidity inside the vehicle using the virtual humidity sensor system for the passenger compartment defined in the present invention, Figure 1 the relevant boundary conditions listed in the system need to be provided as accurately and completely as possible, whether measured by dedicated sensors or obtained by other means. The following discusses each required parameter one by one.

[0152] The ambient temperature can usually be provided by a dedicated sensor of the automatic air conditioning system, or by the vehicle networking through a weather forecast website. According to the application scenarios of this system, whether it is an electric vehicle or a traditional vehicle, the ambient temperature source data needs to be corrected to some extent before use (standard automatic air conditioning correction method). In traditional vehicles, due to the heat pollution of the engine, the temperature at the air inlet of the air conditioner will be higher than the ambient temperature. The heat pollution of electric vehicles is relatively light.

[0153] Similarly, the ambient humidity can also be provided by the vehicle power system or by the vehicle networking through a weather forecast website.

[0154] The proportion of the air in the internal circulation of the vehicle air conditioner can be determined according to the position of the air inlet valve of the air conditioner box.

[0155] The air temperature at the evaporator outlet is provided by the evaporator outlet temperature sensor. Generally, there are one or two evaporator outlet temperature sensors in the air conditioning system for anti-frosting and high-efficiency air conditioning control. In view of the fact that the present invention requires the average outlet air temperature, while the temperature sensor generally aims for the lowest outlet air temperature, necessary correction of the sensor readings is required to improve the accuracy (deviation correction method).

[0156] The air temperature inside the passenger compartment can generally be provided by the vehicle automatic air conditioning system. As a routine measure of the automatic air conditioning, the readings of the in-vehicle temperature sensors are also corrected to accurately reflect the average temperature inside the vehicle.

[0157] The in-vehicle temperature is obtained through the in-vehicle energy conservation equation: Solve the air energy conservation equation for the passenger compartment to obtain the in-vehicle air temperature inside the passenger compartment.

[0158] As Figure 3 The virtual temperature sensor function included in the additional implementation cases of the present invention shown below can solve the following ordinary differential equations to obtain the air temperature inside the vehicle compartment:

[0159]

[0160] Equation (18) represents the ordinary differential equations obtained by establishing the energy conservation equations for the air inside the vehicle compartment and the heat capacity mass inside the vehicle, including the seat mass. T a and T dp represent the temperatures of the air inside the vehicle and the heat capacity mass inside the vehicle respectively. The functions f and g respectively include various energy flows related to their objects, such as solar radiation, heat conduction of the vehicle compartment, heat exchange between the heat capacity mass and the air, etc. Solving the ordinary differential equations under the correct initial conditions can obtain the temperature value of the air inside the vehicle at any time.

[0161] The number of passengers can be provided by the intelligent seats. The rate of water vapor introduced into the vehicle by each passenger through breathing and sweating can be determined according to body weight, gender, and exercise status.

[0162] The moisture source inside the vehicle, especially the precipitation on rainy and snowy days brought in by passengers, can be modeled to simulate the evaporation rate at the temperature and humidity inside the vehicle.

[0163] As Figure 5 shown, the virtual humidity sensor system provided by the present invention has been verified by Matlab / Simulink modeling. Figure 5 Shows that under a humid weather condition, the virtual humidity sensor accurately and reasonably predicts the process that the relative humidity inside the vehicle gradually decreases and stabilizes under the action of air conditioning dehumidification after the vehicle starts. Before the engine starts, the vehicle compartment and the environment have achieved energy and humidity exchange balance after a long time of static placement. The relative humidity outside the vehicle reaches 90%, and the temperature is 15 degrees Celsius. After the engine starts, the air conditioning starts to work, and the air conditioning box blows air to cool the vehicle compartment. Because the exhaust air temperature of the evaporator in the refrigeration system is saturated air at 4 degrees Celsius, the dew point is 4 degrees, and the water vapor content is relatively low, the air conditioning exhausts dry air into the vehicle. Under the action of the air conditioning, the temperature inside the vehicle quickly reaches the set temperature of 25 degrees Celsius. The air inside the vehicle continuously balances the moisture released by the two occupants inside the vehicle through breathing and sweating under the action of air conditioning dehumidification, and discharges the moisture inside the vehicle outside the vehicle after a certain time, thereby making the air conditioning inside the vehicle become dry. As can be seen from Figure 5 , the relative humidity inside the vehicle reaches 37% at about 300 seconds after the engine starts, which is within the better human comfort humidity range, and then remains at this level. At 1450 seconds, the vehicle air conditioning is turned off, the fan stops blowing air, and the air volume is set to zero. The vehicle continues to drive without air conditioning. Due to the continuous release of water vapor by the occupants inside the vehicle and the intrusion of environmental humid air, the relative humidity inside the vehicle rises rapidly. After 200 seconds, the relative humidity inside the vehicle returns to 90%.

[0164] like Figure 6 As shown, Figure 6 The process of humidity changes in the car cabin caused by picking up passengers on a rainy day as sensed by the virtual humidity sensor is shown. The car's ambient temperature is 25 degrees Celsius; due to the rain, the ambient relative humidity is 100%. The car's air conditioner is set to internal circulation, and the evaporator outlet temperature is 7 degrees Celsius. The dehumidification capacity is reduced in this air conditioning setting state, simulating the condition of moisture accumulation in the car caused by improper use of air conditioning in humid weather, which may cause the car windows to fog up. Figure 6 It can be seen that even when the air conditioning dehumidification capacity is low, the relative humidity in the car still gradually decreases from the initial 80% relative humidity to 60% and stabilizes. At this time, the water vapor released by the two passengers in the car and the air conditioning dehumidification are balanced at a higher relative humidity level. At 1450 seconds, the car stopped on the roadside, opened the door, and two more passengers got on the car. Affected by the rain, the clothes and shoes of the new passengers were wet and brought water into the car. The water vapor evaporation of the four passengers is equivalent to the normal water vapor production of seven people. However, after the drying effect of the air conditioning in the car, the water vapor evaporation gradually decreased to the normal water vapor production of four people. Figure 6 The results show that after the new passenger gets on the bus, the relative humidity in the bus increases rapidly and returns to 80% due to excessive evaporation of water vapor that overcomes the lower air conditioning capacity. After that, the passenger's clothes and shoes gradually dry, the amount of water vapor released decreases, and the relative humidity in the bus decreases under the action of the air conditioning, and finally stabilizes to 72%, which is higher than the 60% stable humidity in the bus before adding passengers.

[0165] Those skilled in the art know that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be considered as structures within the hardware component; the devices, modules, and units for realizing various functions can also be considered as both software modules for realizing the method and structures within the hardware component.

[0166] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for a virtual vehicle cabin humidity sensor, characterized in that, It includes the following steps: Steps for establishing the carriage humidity equation: On the internal volume of the vehicle carriage, establish an ordinary differential equation according to the law of conservation of water vapor mass to obtain the carriage water vapor mass conservation equation; Steps for obtaining the absolute humidity inside the vehicle: Input the conditions, solve the carriage water vapor mass conservation equation, and calculate to obtain the absolute humidity inside the vehicle in the carriage; Steps for obtaining humidity parameters: Combine the absolute humidity inside the vehicle in the carriage with the air temperature inside the vehicle to calculate the air humidity parameters inside the vehicle; In the steps for establishing the carriage humidity equation, on the internal volume of the vehicle carriage, establish an ordinary differential equation containing a time derivative according to the conservation of water vapor to obtain the carriage water vapor mass conservation equation; In the steps for obtaining the absolute humidity inside the vehicle, solve the carriage water vapor mass conservation equation according to relevant boundary conditions and initial conditions to obtain the absolute humidity inside the vehicle at any time in the carriage; In the steps for obtaining humidity parameters, combine the absolute humidity inside the vehicle in the carriage with the air temperature inside the vehicle to calculate the relative humidity and the dew point inside the vehicle; In the steps for obtaining the absolute humidity inside the vehicle, the relevant boundary conditions are taking the air volume inside the carriage as the control volume and the carriage shell containing the air volume inside the carriage as the control volume boundary, then the flow-related parameters of any moist air crossing the control volume boundary are the boundary conditions for solving the water vapor mass conservation equation; The initial conditions include the humidity condition of the air inside the vehicle when the vehicle engine starts; In the steps for establishing the carriage humidity equation, there is inflow and outflow of moist air and internal moisture sources in the carriage control volume, and the mass change rate of water vapor in the control volume is expressed by the following balance relationship Among them, m v,cab represents the total mass of water vapor in the car; t represents time; V cab represents the internal volume of the car; ρ v,cab represents the absolute humidity in the car; represents the volume flow rate of the exhaust air from the air conditioner box entering the car; ρ v,hvac represents the absolute humidity of the air discharged from the air conditioner box to the car; represents the volume of the internal circulation air flow extracted by the air conditioner box from the car; represents the exhaust flow rate of the rear exhaust port of the car; represents the other leakage flow rate of the car; n p represents the number of people in the car; represents the average moisture generated per person; represents the moisture generated by other moisture sources in the car.

2. The virtual vehicle cabin humidity sensor method according to claim 1, wherein The relevant boundary conditions include the ambient temperature, ambient humidity, air temperature inside the vehicle, the proportion of the internal circulation of the air conditioner, the intrusion flow rate into the carriage, the air temperature at the outlet of the evaporator, the exhaust flow rate of the air conditioning box, and the exhaust flow rate of the vehicle carriage; The relevant boundary conditions also include other conditions, and the other conditions include the number of people inside the vehicle and weather-related moisture sources; 3. The virtual vehicle cabin humidity sensor method according to claim 1, wherein This method also includes steps for obtaining the carriage temperature: Obtain the data of the in-vehicle temperature sensor of the vehicle's automatic air conditioner through the in-vehicle communication network; 4. The virtual vehicle cabin humidity sensor method according to claim 1, wherein, In the steps for establishing the carriage humidity equation, The change rate of the total amount of water vapor in the carriage is determined by the total amount of the mass flow rate of water vapor entering the vehicle per unit time and the amount of water vapor produced inside the vehicle per unit time, minus the total mass flow rate of water vapor overflowing outside the vehicle per unit time; If the total inflow of water vapor is greater than the total outflow, the total amount of water vapor retained inside the vehicle becomes larger, and a positive change rate is obtained; If the total inflow of water vapor is less than the total outflow, the total amount of water vapor retained inside the vehicle becomes smaller, and a negative change rate is obtained; In view of the fact that the carriage exhaust, air leakage, and the internal circulation air flow satisfy the following conservation equation: Equation (1) is simplified to ρ in Equation (3) v,cab is the variable to be solved, and ρ v,hvac is the input variable; if ρ v,hvac is known or expressed in terms of known variables, then Equation (3) is solved as an ordinary differential equation using numerical algorithms.

5. The virtual vehicle cabin humidity sensor method according to claim 4, characterized in that, In the steps for obtaining the absolute humidity inside the vehicle, determine the humidity of the air exhausted from the air conditioning box; The air discharged from the air conditioning box into the carriage is a mixture of the cold air from the evaporator and the warm air from the heater. The warm air is obtained by partially heating the cold air from the evaporator, and the absolute humidity discharged into the carriage is determined by the humidity of the air flow at the outlet of the evaporator; In order to establish the calculation formula for the air humidity at the outlet of the evaporator, first determine the absolute humidity at the inlet of the evaporator; The incoming air of the evaporator consists of two airflows: one is the internal circulation airflow extracted by the air conditioner box from the passenger compartment, and the other is the external air drawn in by the air conditioner box through the external air inlet; the absolute humidity after the mixing of the two airflows is obtained by Equation (4): Among them, ρ v,eia represents the absolute humidity of the air at the inlet of the evaporator; ρ v,oa represents the absolute humidity of the outside air drawn in at the outside air inlet of the air handling unit; represents the volume flow rate of the outside air drawn in at the outside air inlet of the air handling unit; The internal circulation rate of the air-conditioning airflow is defined by Equation (5): where RR represents the internal circulation ratio of the air conditioner; The air temperature and absolute humidity at the evaporator inlet are determined by Equations (6) and (7) according to the conservation of energy and mass: T eia = T oa (1 - RR)+T cab RR (6) ρ v,eia = ρ v,oa (1 - RR)+ ρ v,cab RR (7) Among them, T eia represents the temperature of the air at the inlet of the evaporator; T oa represents the temperature of the outside air; T cab represents the temperature of the air inside the vehicle compartment; The partial pressure of water vapor and the air dew point temperature at the evaporator inlet are calculated by the ideal gas state equation (8) and the water vapor saturation curve equation (9) respectively: P v,eia = ρ v,eia RT eia (8) T d,eia = T s (P v,eia ) (9) Among them, P v,eia represents the partial pressure of water vapor component of the air at the inlet of the evaporator; R represents the ideal gas constant of water vapor; T d,eia represents the dew point temperature of the air at the inlet of the evaporator; T s (P v,eia ) represents the saturation temperature at the partial pressure of water vapor of the air at the inlet of the evaporator; The evaporator of the air-conditioning system absorbs the heat energy of the incoming air to reduce the temperature; if the outlet air temperature of the evaporator drops below the dew point, the moisture in the airflow will condense and precipitate, and the absolute humidity of the airflow will decrease; Judge whether the outlet air temperature is lower than the inlet air dew point or higher than the inlet air dew point; If the outlet air temperature is higher than the inlet air dew point, no water vapor condensation occurs in the evaporator, and the absolute humidity of the outlet air is equal to the absolute humidity of the inlet air; If the outlet air temperature is lower than the inlet air dew point, then there must be condensed water in the evaporator, and the outlet air is in a saturated state at the outlet air temperature.

6. The virtual vehicle cabin humidity sensor method according to claim 5, characterized in that, In the step of obtaining the absolute humidity inside the vehicle, an outlet air temperature sensor is arranged at the outlet of the evaporator; according to the sensor reading and the temperature control target value, the air-conditioning control system adjusts the compressor speed or the compressor displacement to make the evaporator in the correct working state; Based on the outlet air temperature sensor, judge whether the outlet air temperature is higher or lower than the inlet air dew point; If the outlet air temperature is higher than the inlet air dew point, make the following conditions hold: T eoa >T d,eia (10) Among them, T eoa represents the air temperature at the outlet of the evaporator; It is known that no condensation occurs in the evaporator, and at this time the absolute humidity of the outlet air is equal to the absolute humidity of the inlet air: ρ v,eoa = ρ v,eia = ρ v,oa (1 - RR)+ ρ v,cab RR (11) Among them, ρ v,eoa represents the absolute humidity of the air at the outlet of the evaporator; Obtain the absolute humidity of the air discharged from the air conditioner box to the passenger compartment: ρ v,hvac = ρ v,oa (1 - RR)+ ρ v,cab RR (12) If the evaporator cools the airflow below the dew point of the inlet air, the condition of Equation (13) is satisfied: T eoa <T d,eia (13) The evaporator cools the air below the dew point of the inlet air temperature, and condensation occurs in the evaporator. At this time, the outlet air of the evaporator is in a saturated state; therefore, the partial pressure of water vapor in the outlet air is determined according to the outlet air temperature sensor reading and the steam saturation curve: P v,eoa = P s (T eoa )(14) Among them, P v,eoa represents the water vapor partial pressure of the air at the evaporator outlet; P s (T eoa ) represents the saturated water vapor pressure curve; Obtain the absolute humidity of the outlet air according to the partial pressure of the outlet steam, that is, obtain the absolute humidity of the air discharged from the air conditioner box to the passenger compartment, and determine it according to the ideal gas equation:

7. The virtual vehicle cabin humidity sensor method according to claim 6, characterized in that In the step of obtaining the absolute humidity inside the vehicle, according to the absolute humidity of the air discharged from the air conditioner box to the passenger compartment, Equation (3) becomes an ordinary differential equation to be solved; Corresponding to the two working conditions of the evaporator dehumidification and non-dehumidification, the ordinary differential equation of absolute humidity takes different forms: In the non-dehumidification working condition, the form of the ordinary differential equation is shown by Equation (16): In the evaporator dehumidification working condition, the ordinary differential equation takes the form of Equation (17):

8. A virtual vehicle cabin humidity sensor system, characterized in that, Applying the virtual vehicle passenger compartment humidity sensor method according to any one of claims 1-7, includes the following modules: Compartment humidity equation establishment module: On the internal volume of the vehicle compartment, establish an ordinary differential equation according to the conservation of water vapor mass to obtain the vehicle compartment water vapor mass conservation equation; Internal vehicle absolute humidity acquisition module: Input conditions, solve the vehicle compartment water vapor mass conservation equation, and obtain the internal vehicle absolute humidity inside the vehicle compartment; Humidity parameter acquisition module: Combine the internal vehicle absolute humidity inside the vehicle compartment with the internal vehicle air temperature to calculate the air humidity parameters inside the vehicle compartment.

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