Cooling fan control system and method based on air conditioner pressure sensor

Abstract

The invention provides a cooling fan control system and method based on an air conditioner pressure sensor, and belongs to the technical field of cooling fan control. The input end of the engine control unit is connected with an air conditioner pressure sensor, a water temperature sensor and a wheel speed sensor, and the output end of the engine control unit is connected with a cooling fan controller. The cooling fan controller is also connected with a cooling fan; the engine control unit obtains air conditioner load state information through an air conditioner pressure sensor, obtains cooling liquid temperature information of an engine cooling system through a water temperature sensor and obtains vehicle running state information through a wheel speed sensor. And a rotating speed control signal of the cooling fan required under the current vehicle condition is obtained through fuzzy reasoning in combination with a fuzzy control strategy, so that the cooling fan is controlled. Real-time continuous adjustment of the cooling fan is achieved, and the purposes of saving oil, reducing consumption and improving the NVH performance of the automobile are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle cooling fan control, and in particular relates to a cooling fan control system and method based on an air-conditioning pressure sensor. Background Art

[0002] The cooling fan is an important part of the automobile cooling system and is crucial to maintaining the normal operation of the automobile engine and air-conditioning system. Most traditional cooling fan control methods rely on detecting the engine water temperature and the pressure status of the air-conditioning system, and realizing multi-gear adjustment of the cooling fan by controlling the on and off of the relay. For example, a pressure switch is used to detect the pressure status and load status of the air-conditioning system in real time. When the air-conditioning system pressure is greater than a certain pressure and the air-conditioning system is in a high-load operating state, the medium-pressure switch will open, and the cooling fan will be controlled to run at a higher speed through the relay; when the air-conditioning system pressure is less than a certain pressure and the air-conditioning system is in a low-load operating state, the medium-pressure switch will be closed, and the cooling fan will be controlled to run at a lower speed through the relay. However, this control method has obvious defects: First, the speed of the cooling fan cannot be adjusted accurately and continuously according to the current vehicle conditions, resulting in low efficiency of the cooling fan, which is not conducive to fuel saving and consumption reduction. Second, when the pressure of the air conditioning system suddenly changes, the speed of the cooling fan changes suddenly, which will increase the noise and vibration of the vehicle and affect the NVH performance of the vehicle.

[0003] This is a shortcoming of the prior art. Therefore, in view of the above defects in the prior art, it is very necessary to provide a cooling fan control system and method based on an air conditioning pressure sensor. Summary of the invention

[0004] In view of the defects that the traditional cooling fan control method relies on detecting the engine water temperature and the pressure state of the air-conditioning system, and realizes multi-speed adjustment of the cooling fan by controlling the on and off of the relay, it is impossible to achieve continuous adjustment, the cooling efficiency is low, and the cooling fan speed changes suddenly, which affects the vehicle NVH performance. The present invention provides a cooling fan control system and method based on an air-conditioning pressure sensor to solve the above technical problems.

[0005] In a first aspect, the present invention provides a cooling fan control system based on an air conditioning pressure sensor, comprising an engine control unit; The input end of the engine control unit is connected to an air conditioning pressure sensor, a water temperature sensor and a wheel speed sensor, and the output end of the engine control unit is connected to a cooling fan controller; The cooling fan controller is also connected to a cooling fan; The engine control unit obtains the air-conditioning load status information through the air-conditioning pressure sensor, obtains the coolant temperature information of the engine cooling system through the water temperature sensor, and obtains the vehicle driving status information through the wheel speed sensor. Based on the air-conditioning load status information, coolant temperature information, and vehicle driving status information, combined with the fuzzy control strategy, fuzzy inference is performed to derive the speed control signal of the cooling fan required under the current vehicle condition, thereby controlling the cooling fan. Furthermore, the air conditioning pressure sensor is arranged on the high-pressure pipeline of the vehicle air conditioning system, and collects the refrigerant pressure in the vehicle air conditioning system as the air conditioning load status information and provides it to the engine control unit. The air conditioning pressure sensor has the advantage of fast dynamic response characteristics, and can dynamically respond to the load of the air conditioning system in real time, ensuring that the subsequent adjustment of the cooling fan speed can be controlled in real time; the air conditioning pressure sensor detects the refrigerant pressure of the air conditioning system in real time, and can detect the slow leakage of the air conditioning refrigerant, which can prevent the occurrence of air conditioning system failure; the air conditioning pressure sensor has better accuracy, service life and reliability than traditional pressure switches, and is more suitable for vehicle system applications.

[0006] Furthermore, a water temperature sensor is arranged on the thermostat of the engine to collect coolant temperature information of the engine cooling system and provide it to the engine control unit.

[0007] Furthermore, a wheel speed sensor is arranged at the wheel hub of the vehicle to collect the vehicle's running speed and provide it to the engine control unit as vehicle running state information.

[0008] In a second aspect, the present invention provides a cooling fan control method based on an air conditioning pressure sensor, comprising the following steps: S1. The engine control unit obtains the air conditioning load state signal through the air conditioning pressure sensor, obtains the coolant temperature signal of the engine cooling system through the water temperature sensor, and obtains the vehicle driving state signal through the wheel speed sensor; S2. The engine control unit fuzzily infers the speed control signal of the cooling fan required under the current vehicle condition based on the air conditioning load state signal, the coolant temperature signal, and the vehicle driving state signal, combined with the fuzzy control strategy, so as to control the cooling fan.

[0009] Furthermore, the specific steps of step S2 are as follows: S21. The engine control unit pre-stores the high pressure limit value Ph and the low pressure limit value Pl of the air conditioning system pressure, the high gear speed nh and the low gear speed nl of the cooling fan, the duty cycle Hh of the pulse width modulation signal corresponding to the high gear speed nh and the duty cycle Hl of the pulse width modulation signal corresponding to the low gear speed nl; S22. The engine control unit pre - determines the fuzzy subsets, natural domain, universe of discourse, and membership functions of the pressure value of the air - conditioning system, the coolant temperature of the engine cooling system, and the pulse - width modulation signal of the cooling fan, pre - saves the divided vehicle speed ranges, and formulates a fuzzy rule table for each vehicle speed range with the pressure of the air - conditioning system and the coolant temperature of the engine cooling system as inputs and the duty cycle of the pulse - width modulation signal of the cooling fan as the output; S23. The engine control unit detects whether the real - time pressure P of the air - conditioning system is between the extreme high - pressure value Ph and the extreme low - pressure value Pl; If so, proceed to step S25; If not, proceed to step S24; S24. The engine control unit detects the relationship between the real - time pressure P of the air - conditioning system and the extreme high - pressure value Ph and the extreme low - pressure value Pl; If P < Pl, it is determined that there is a risk of refrigerant leakage in the air - conditioning system, the air - conditioning compressor is disconnected, and the duty cycle Hl of the pulse - width modulation signal for controlling the cooling fan to use the low - gear speed nl is output until the air - conditioning system pressure Pl ≤ P ≤ Ph, and then proceed to step S25; If P > Ph, it is determined that there is too much refrigerant in the air - conditioning system or the condenser has poor heat dissipation, the air - conditioning compressor is disconnected, and the duty cycle Hh of the pulse - width modulation signal for controlling the cooling fan to use the high - gear speed nh is output until the air - conditioning system pressure Pl ≤ P ≤ Ph, and then proceed to step S25; S25. The engine control unit judges the real - time driving vehicle speed signal v of the vehicle, identifies the vehicle speed range to which the vehicle belongs, and simultaneously performs normalization processing and fuzzy processing on the pressure signal of the air - conditioning system and the temperature signal of the engine coolant; S26. The engine control unit inputs the fuzzified pressure value of the air - conditioning system and the coolant temperature of the engine cooling system corresponding to a fuzzy rule table according to the vehicle speed range to which the vehicle belongs, and obtains the fuzzy output of the duty cycle of the pulse - width modulation signal of the cooling fan; S27. The engine control unit performs fuzzy processing on the fuzzy output of the duty cycle of the pulse - width modulation signal of the cooling fan using the membership function to obtain a control signal, and then amplifies it using the pre - formulated scale factor to obtain the pulse - width modulation signal required for cooling fan control.

[0010] Further, the specific steps of step S22 are as follows: S221. The engine control unit determines the natural domain of the pressure value of the air - conditioning system, defines and sets the pressure median value, defines the air - conditioning system pressure deviation value as the difference between the pressure value and the pressure median value, sets the natural domain C1, universe of discourse B1, and fuzzy set W1 with N1 fuzzy subsets of the air - conditioning system pressure deviation value, and sets the trigonometric function as the membership function of the deviation of the air - conditioning pressure value; S222. The engine control unit determines the natural domain C2 and the domain B2 of the coolant temperature of the engine cooling system as a fuzzy set W2 having N2 fuzzy subsets, and sets a trigonometric function as a membership function of the coolant temperature of the engine cooling system; S223. The engine control unit determines the natural domain C3, the domain B3 and the fuzzy set W3 having N3 fuzzy subsets of the pulse width modulation signal of the cooling fan, and sets the trigonometric function as the membership function of the pulse width modulation signal of the cooling fan; S224. Pre-store the divided N4 vehicle speed ranges, and determine all possible combinations of the air conditioning system pressure deviation value and the coolant temperature of the engine cooling system under each vehicle speed range; S225. For each combination, based on experience or experimental data, determine the fuzzy subset of the pulse width modulation signal of the output cooling fan; S226. Arrange the fuzzy subsets of the pulse width modulation signals of the cooling fans of each combination under each vehicle speed range into a table form to obtain N4 fuzzy rule tables.

[0011] Furthermore, the specific steps of step S25 are as follows: S251. The engine control unit determines the speed range of the vehicle according to the real-time vehicle speed signal v; S252. The engine control unit calculates the current air-conditioning system pressure deviation value according to the current air-conditioning system pressure value and the set pressure median value, and then maps it to the domain B1 through the natural domain C1, and determines which fuzzy subset of the fuzzy set W1 the air-conditioning system pressure deviation value belongs to according to the trigonometric function, thereby taking it as the fuzzy value of the air-conditioning system pressure deviation value; S253. The engine control unit maps the coolant temperature of the current engine cooling system to the domain B2 through the natural domain C2 to which it belongs, and then determines which fuzzy subset of the fuzzy set W2 the coolant temperature of the current engine cooling system belongs to based on the trigonometric function, thereby using it as the fuzzy value of the coolant temperature of the engine cooling system.

[0012] Furthermore, the specific steps of step S26 are as follows: S261. The engine control unit determines an adapted fuzzy rule table according to the speed range of the vehicle and the pre-established fuzzy rules; S262. The engine control unit inputs the fuzzy value of the air conditioning system pressure deviation value and the fuzzy value of the coolant temperature of the engine cooling system into the adaptive fuzzy rule table to obtain the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan.

[0013] Furthermore, the specific steps of step S27 are as follows: S271. The engine control unit performs a defuzzification operation on the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan using the maximum membership method, and then maps it from the domain B3 to the natural domain C3 to obtain the actual pulse width modulation signal of the cooling fan; S272. The engine control unit outputs the actual cooling fan pulse width modulation signal to the cooling fan through the cooling fan controller.

[0014] The beneficial effects of the present invention are: The cooling fan control system and method based on the air-conditioning pressure sensor provided by the present invention adopt a fuzzy control strategy to fuzzily infer the cooling fan speed required for cooling and heat dissipation under the current vehicle condition through the current vehicle condition information of the vehicle, and realize real-time continuous adjustment of the cooling fan by adjusting the duty cycle of the pulse width modulation signal. Compared with the traditional method of adjusting the cooling fan speed by controlling the on-off switching gear of the relay, the fuzzy control strategy can realize continuous adjustment of the cooling fan speed, thereby achieving the purpose of saving fuel and reducing consumption and improving the NVH performance of the vehicle.

[0015] The present invention uses an air-conditioning pressure sensor with higher accuracy, better reliability and faster response to detect the pressure of the air-conditioning system. Compared with the traditional method of using a pressure switch to detect the pressure of the air-conditioning system, it can detect the refrigerant pressure in the air-conditioning system in real time and dynamically reflect the load of the air-conditioning system. The present invention adjusts the fan speed of the cooling fan by comprehensively judging the pressure of the air-conditioning system, the water temperature of the engine coolant and the real-time speed of the vehicle. Compared with adjusting and controlling the fan speed by only a single environmental variable, it has better reliability.

[0016] It can be seen that compared with the prior art, the present invention has outstanding substantive features and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a schematic diagram of a cooling fan control system based on an air conditioning pressure sensor of the present invention.

[0019] Figure 2 It is a flow chart of an embodiment of a cooling fan control method based on an air conditioning pressure sensor of the present invention.

[0020] Figure 3It is a flow chart of another embodiment of a cooling fan control method based on an air conditioning pressure sensor of the present invention.

[0021] Figure 4 It is a schematic representation of fuzzy rules in an embodiment of a cooling fan control method based on an air conditioning pressure sensor of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0023] See also Figure 1 Shown is a cooling fan control system based on an air conditioning pressure sensor in a specific implementation, including an engine control unit; The input end of the engine control unit is connected to an air conditioning pressure sensor, a water temperature sensor and a wheel speed sensor, and the output end of the engine control unit is connected to a cooling fan controller; The cooling fan controller is also connected to a cooling fan; The engine control unit obtains the air-conditioning load status information through the air-conditioning pressure sensor, obtains the coolant temperature information of the engine cooling system through the water temperature sensor, and obtains the vehicle driving status information through the wheel speed sensor. Based on the air-conditioning load status information, coolant temperature information, and vehicle driving status information, combined with the fuzzy control strategy, fuzzy inference is performed to derive the speed control signal of the cooling fan required under the current vehicle condition, thereby controlling the cooling fan.

[0024] In this embodiment, the air conditioning pressure sensor is arranged on the high-pressure pipeline of the vehicle air conditioning system, and collects the refrigerant pressure in the vehicle air conditioning system as the air conditioning load state information and provides it to the engine control unit; The water temperature sensor is installed on the engine's thermostat to collect the coolant temperature information of the engine cooling system and provide it to the engine control unit; The wheel speed sensor is installed at the wheel hub of the vehicle to collect the vehicle's driving speed as vehicle driving status information and provide it to the engine control unit.

[0025] The following is an embodiment of a cooling fan control method based on an air conditioning pressure sensor provided in an embodiment of the present disclosure. This method and the cooling fan control systems based on an air conditioning pressure sensor in the above-mentioned embodiments belong to the same inventive concept. For details not fully described in the embodiment of the cooling fan control method based on an air conditioning pressure sensor, reference can be made to the above-mentioned embodiment of the cooling fan control system based on an air conditioning pressure sensor.

[0026] As Figure 2 shown, the method includes the following steps: S1. The engine control unit obtains the air-conditioning load status signal through the air-conditioning pressure sensor, obtains the coolant temperature signal of the engine cooling system through the water temperature sensor, and obtains the vehicle driving status signal through the wheel speed sensor; S2. The engine control unit fuzzily infers the rotation speed control signal of the cooling fan required under the current vehicle condition according to the air-conditioning load status signal, the coolant temperature signal, and the vehicle driving status signal, and combines the fuzzy control strategy, so as to control the cooling fan.

[0027] The fuzzy control strategy formulated by the present invention can realize the precise continuous control of the cooling fan by adjusting the duty ratio of the pulse width modulation signal according to the current state information of the vehicle running, and can achieve the purpose of saving fuel, reducing consumption, reducing noise and vibration.

[0028] In this embodiment, as Figure 3 shown, the specific steps of step S2 are as follows: S21. The engine control unit pre-saves the extreme high pressure value Ph and extreme low pressure value Pl of the air-conditioning system pressure, the high gear rotation speed nh and low gear rotation speed nl of the cooling fan, the duty ratio Hh of the pulse width modulation signal corresponding to the high gear rotation speed nh, and the duty ratio Hl of the pulse width modulation signal corresponding to the low gear rotation speed nl; for example, Pl is set to 0.19 Mpa, Ph is set to 3.1 Mpa, Hl is set to 20%, and Hh is set to 100%; S22. The engine control unit pre-determines the fuzzy subsets, natural domains, universes of discourse, and membership functions of the pressure value of the air-conditioning system, the coolant temperature of the engine cooling system, and the pulse width modulation signal of the cooling fan, pre-saves the divided vehicle speed ranges, and formulates a fuzzy rule table with the pressure of the air-conditioning system and the coolant temperature of the engine cooling system as inputs and the duty ratio of the pulse width modulation signal of the cooling fan as the output for each vehicle speed range; S23. The engine control unit detects whether the real-time pressure P of the air-conditioning system is between the extreme high pressure value Ph and the extreme low pressure value Pl; If so, go to step S25; If not, go to step S24; S24. The engine control unit detects the relationship between the real-time pressure P of the air-conditioning system and the extreme high pressure value Ph and the extreme low pressure value Pl; If P < Pl, it is determined that there is a risk of refrigerant leakage in the air-conditioning system, the air-conditioning compressor is disconnected, and the duty ratio Hl of the pulse width modulation signal for controlling the cooling fan to use the low gear rotation speed nl is output until the air-conditioning system pressure Pl ≤ P ≤ Ph, and then go to step S25; If P>Ph, it is determined that the air conditioning system is overcharged with refrigerant or the condenser has poor heat dissipation, the air conditioning compressor is disconnected, and a duty cycle Hh of a pulse width modulation signal for controlling the cooling fan to use a high gear speed nh is output until the air conditioning system pressure Pl≤P≤Ph, and the process proceeds to step S25; S25. The engine control unit determines the real-time vehicle speed signal v, identifies the speed range to which the vehicle belongs, and normalizes and fuzzifies the pressure signal of the air conditioning system and the temperature signal of the engine coolant; S26. The engine control unit inputs the fuzzy air conditioning system pressure value and the coolant temperature of the engine cooling system into a fuzzy rule table according to the speed range of the vehicle, and obtains the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan; S27. The engine control unit uses a membership function to perform fuzzy processing on the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan to obtain a control signal, and then uses a pre-determined proportional factor to amplify the pulse width modulation signal required for cooling fan control.

[0029] It should be noted that, in some embodiments, the specific steps of step S22 are as follows: S221. The engine control unit determines the natural domain of the pressure value of the air conditioning system, defines and sets the median pressure value, defines the pressure deviation value of the air conditioning system as the difference between the pressure value and the median pressure value, sets the natural domain C1, the domain B1 and the fuzzy set W1 with N1 fuzzy subsets of the pressure deviation value of the air conditioning system, and sets the trigonometric function as the membership function of the deviation of the air conditioning pressure value; For example, the natural domain of the air-conditioning system pressure value is [0.2, 3]. At this time, the median pressure value P0 of the air-conditioning system is defined, and P0 is set to 1.6Mpa. P' is defined as the air-conditioning system pressure value deviation P'=P-P0. At this time, the natural domain of the air-conditioning pressure value deviation is [-1.4, 1.4], and the domain of the air-conditioning system pressure value deviation is set to [-1, 1]. At the same time, seven fuzzy subsets are set for the pressure value deviation P', namely NB, NM, NS, ZE, PS, PM, PB, and a triangular function is set as the membership function of the pressure value deviation P'; S222. The engine control unit determines the natural domain C2 and the domain B2 of the coolant temperature of the engine cooling system as a fuzzy set W2 having N2 fuzzy subsets, and sets a trigonometric function as a membership function of the coolant temperature of the engine cooling system; For example, the natural domain of the engine water temperature value T is [88, 112], the domain of the engine water temperature value is set to [0, 1], and four fuzzy subsets are set for the engine water temperature value T, namely ZE, S, M, and B, and a triangular function is set as the membership function of the engine water temperature value T; S223. The engine control unit determines the natural domain C3, the universe of discourse B3, and the fuzzy set W3 with N3 fuzzy subsets of the pulse width modulation signal of the cooling fan, and sets the trigonometric function as the membership function of the pulse width modulation signal of the cooling fan; For example, the natural domain of the pulse width modulation signal H output by the engine control unit is defined as [20, 100], the universe of discourse of the pulse width modulation signal output by the engine control unit is set to [0, 1], and at the same time, four fuzzy subsets are set for the pulse width modulation signal H output by the engine control unit, namely ZE, S, M, and B, and the triangular function is set as the membership function of the pulse width modulation signal H output by the engine control unit; S224. Pre-save the N4 divided vehicle speed ranges, and determine all possible combinations of the air conditioning system pressure deviation value and the coolant temperature of the engine cooling system under each vehicle speed range; For example, divide four vehicle speed ranges: ultra-low speed 0 < v < v1, low speed v1 < v < v2, medium speed v2 < v < v3, high speed v > v3, where v1 is set to 20 km / h, v2 is set to 40 km / h, and v3 is set to 80 km / h; S225. For each combination, determine the fuzzy subset of the pulse width modulation signal of the output cooling fan according to experience or experimental data; S226. Organize the fuzzy subsets of the pulse width modulation signal of the cooling fan for each combination under each vehicle speed range into a table form to obtain N4 fuzzy rule tables; Four fuzzy rule tables A1, A2, A3, and A4 set for the four vehicle speed ranges are as follows Figure 4 shown; The specific steps of step S25 are as follows: S251. The engine control unit determines the vehicle speed range to which the vehicle belongs according to the real-time driving vehicle speed signal v of the vehicle; S252. The engine control unit calculates the current air conditioning system pressure deviation value according to the current pressure value of the air conditioning system and the set pressure median value, then maps it to the universe of discourse B1 through the natural domain C1, and determines which fuzzy subset of the fuzzy set W1 the air conditioning system pressure deviation value belongs to according to the trigonometric function, so as to be used as the fuzzy value of the air conditioning system pressure deviation value; S253. The engine control unit maps the current coolant temperature of the engine cooling system to the universe of discourse B2 through the natural domain C2, and then determines which fuzzy subset of the fuzzy set W2 the current coolant temperature of the engine cooling system belongs to according to the trigonometric function, so as to be used as the fuzzy value of the coolant temperature of the engine cooling system; The specific steps of step S26 are as follows: S261. The engine control unit determines an adapted fuzzy rule table according to the speed range of the vehicle and the pre-established fuzzy rules; If the car is driving at an ultra-low speed, then the fuzzy rule table A1 is used; if the car is driving at a low speed, then the fuzzy rule table A2 is used; if the car is driving at a medium speed, then the fuzzy rule table A3 is used; if the car is driving at a high speed, then the fuzzy rule table A4 is used; S262. The engine control unit inputs the fuzzy value of the air conditioning system pressure deviation value and the fuzzy value of the coolant temperature of the engine cooling system into the adapted fuzzy rule table to obtain the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan; The specific steps of step S27 are as follows: S271. The engine control unit performs a defuzzification operation on the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan using the maximum membership method, and then maps it from the domain B3 to the natural domain C3 to obtain the actual pulse width modulation signal of the cooling fan; S272. The engine control unit outputs the actual cooling fan pulse width modulation signal to the cooling fan through the cooling fan controller.

[0030] It should be understood that the order of execution of the steps in the above embodiment does not mean that the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0031] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person skilled in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and they shall be within the scope of protection of the present invention.

Claims

1. A cooling fan control system based on an air conditioning pressure sensor, characterized in that: including an engine control unit; The input end of the engine control unit is connected with an air-conditioning pressure sensor, a water temperature sensor and a wheel speed sensor, and the output end of the engine control unit is connected with a cooling fan controller; The cooling fan controller is also connected with a cooling fan; The engine control unit obtains the air-conditioning load state information through the air-conditioning pressure sensor, obtains the coolant temperature information of the engine cooling system through the water temperature sensor, and obtains the vehicle driving state information through the wheel speed sensor, and based on the air-conditioning load state information, the coolant temperature information, and the vehicle driving state information, combines with the fuzzy control strategy to perform fuzzy inference on the rotation speed control signal of the cooling fan required under the current vehicle condition, so as to control the cooling fan.

2. The cooling fan control system based on the air conditioning pressure sensor according to claim 1, characterized in that: The air-conditioning pressure sensor is arranged on the high-pressure pipeline of the vehicle air-conditioning system, and collects the refrigerant pressure in the vehicle air-conditioning system as the air-conditioning load state information and provides it to the engine control unit.

3. The cooling fan control system based on the air conditioning pressure sensor according to claim 1, characterized in that: The water temperature sensor is arranged on the thermostat of the engine, and collects the coolant temperature information of the engine cooling system and provides it to the engine control unit.

4. The cooling fan control system based on the air conditioning pressure sensor according to claim 1, characterized in that: The wheel speed sensor is arranged at the vehicle hub, and collects the driving speed of the vehicle as the vehicle driving state information and provides it to the engine control unit.

5. A cooling fan control method based on an air conditioning pressure sensor, characterized in that: including the following steps: S1. The engine control unit obtains the air-conditioning load state signal through the air-conditioning pressure sensor, obtains the coolant temperature signal of the engine cooling system through the water temperature sensor, and obtains the vehicle driving state signal through the wheel speed sensor; S2. The engine control unit combines with the fuzzy control strategy to perform fuzzy inference on the rotation speed control signal of the cooling fan required under the current vehicle condition according to the air-conditioning load state signal, the coolant temperature signal, and the vehicle driving state signal, so as to control the cooling fan.

6. The cooling fan control method based on the air conditioning pressure sensor according to claim 5, characterized in that: The specific steps of step S2 are as follows: S21. The engine control unit pre-saves the extreme high pressure value Ph and extreme low pressure value Pl of the air-conditioning system pressure, the high gear rotation speed nh and low gear rotation speed nl of the cooling fan, the duty ratio Hh of the pulse width modulation signal corresponding to the high gear rotation speed nh, and the duty ratio Hl of the pulse width modulation signal corresponding to the low gear rotation speed nl; S22. The engine control unit pre-determines the fuzzy subsets, natural domains, universes of discourse, and membership functions of the pressure value of the air-conditioning system, the coolant temperature of the engine cooling system, and the pulse width modulation signal of the cooling fan, pre-saves the divided vehicle speed ranges, and formulates a fuzzy rule table with the pressure of the air-conditioning system and the coolant temperature of the engine cooling system as inputs and the duty ratio of the pulse width modulation signal of the cooling fan as the output for each vehicle speed range; S23. The engine control unit detects whether the real-time pressure P of the air-conditioning system is between the extreme high pressure value Ph and the extreme low pressure value Pl; If so, go to step S25; If not, go to step S24; S24. The engine control unit detects the relationship between the real-time pressure P of the air-conditioning system and the extreme high pressure value Ph and the extreme low pressure value Pl; If P < Pl, it is determined that there is a risk of refrigerant leakage in the air-conditioning system, the air-conditioning compressor is disconnected, and the duty ratio Hl of the pulse width modulation signal for controlling the cooling fan to use the low gear rotation speed nl is output until the air-conditioning system pressure Pl ≤ P ≤ Ph, and then go to step S25; If P>Ph, it is determined that the air conditioning system is overcharged with refrigerant or the condenser has poor heat dissipation, the air conditioning compressor is disconnected, and a duty cycle Hh of a pulse width modulation signal for controlling the cooling fan to use a high gear speed nh is output until the air conditioning system pressure Pl≤P≤Ph, and the process proceeds to step S25; S25. The engine control unit determines the real-time vehicle speed signal v, identifies the speed range to which the vehicle belongs, and normalizes and fuzzifies the pressure signal of the air conditioning system and the temperature signal of the engine coolant; S26. The engine control unit inputs the fuzzy air conditioning system pressure value and the coolant temperature of the engine cooling system into a fuzzy rule table according to the speed range of the vehicle, and obtains the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan; S27. The engine control unit uses a membership function to perform fuzzy processing on the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan to obtain a control signal, and then uses a pre-determined proportional factor to amplify the pulse width modulation signal required for cooling fan control.

7. The cooling fan control method based on the air conditioning pressure sensor according to claim 6, characterized in that: The specific steps of step S22 are as follows: S221. The engine control unit determines the natural domain of the pressure value of the air conditioning system, defines and sets the median pressure value, defines the pressure deviation value of the air conditioning system as the difference between the pressure value and the median pressure value, sets the natural domain C1, the domain B1 and the fuzzy set W1 with N1 fuzzy subsets of the pressure deviation value of the air conditioning system, and sets the trigonometric function as the membership function of the deviation of the air conditioning pressure value; S222. The engine control unit determines the natural domain C2 and the domain B2 of the coolant temperature of the engine cooling system as a fuzzy set W2 having N2 fuzzy subsets, and sets a trigonometric function as a membership function of the coolant temperature of the engine cooling system; S223. The engine control unit determines the natural domain C3, the domain B3 and the fuzzy set W3 having N3 fuzzy subsets of the pulse width modulation signal of the cooling fan, and sets the trigonometric function as the membership function of the pulse width modulation signal of the cooling fan; S224. Pre-store the divided N4 vehicle speed ranges, and determine all possible combinations of the air conditioning system pressure deviation value and the coolant temperature of the engine cooling system under each vehicle speed range; S225. For each combination, based on experience or experimental data, determine the fuzzy subset of the pulse width modulation signal of the output cooling fan; S226. Arrange the fuzzy subsets of the pulse width modulation signals of the cooling fans of each combination under each vehicle speed range into a table form to obtain N4 fuzzy rule tables.

8. The cooling fan control method based on the air conditioning pressure sensor according to claim 7, characterized in that: The specific steps of step S25 are as follows: S251. The engine control unit determines the speed range of the vehicle according to the real-time vehicle speed signal v; S252. The engine control unit calculates the current air-conditioning system pressure deviation value according to the current air-conditioning system pressure value and the set pressure median value, and then maps it to the domain B1 through the natural domain C1, and determines which fuzzy subset of the fuzzy set W1 the air-conditioning system pressure deviation value belongs to according to the trigonometric function, thereby taking it as the fuzzy value of the air-conditioning system pressure deviation value; S253. The engine control unit maps the coolant temperature of the current engine cooling system to the domain B2 through the natural domain C2 to which it belongs, and then determines which fuzzy subset of the fuzzy set W2 the coolant temperature of the current engine cooling system belongs to based on the trigonometric function, thereby using it as the fuzzy value of the coolant temperature of the engine cooling system.

9. The cooling fan control method based on the air conditioning pressure sensor according to claim 8, characterized in that: The specific steps of step S26 are as follows: S261. The engine control unit determines an adapted fuzzy rule table according to the vehicle speed range and the pre-established fuzzy rules; S262. The engine control unit inputs the fuzzy value of the air conditioning system pressure deviation value and the fuzzy value of the coolant temperature of the engine cooling system into the adaptive fuzzy rule table to obtain the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan.

10. The cooling fan control method based on the air conditioning pressure sensor according to claim 9, characterized in that: The specific steps of step S27 are as follows: S271. The engine control unit performs a defuzzification operation on the fuzzy output of the duty cycle of the pulse width modulation signal of the cooling fan using the maximum membership method, and then maps it from the domain B3 to the natural domain C3 to obtain the actual pulse width modulation signal of the cooling fan; S272. The engine control unit outputs the actual cooling fan pulse width modulation signal to the cooling fan through the cooling fan controller.

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