CN104049650A - Wet-type DCT clutch temperature control system based on fuzzy control and control method thereof - Google Patents

Abstract

The invention discloses a fuzzy control-based wet DCT clutch temperature control system and a control method thereof. The system consists of a sensor detection module, a signal processing module and a main control module; the method is to collect in real time the temperature of the oil thrown out from the clutch oil outlet of the wet DCT, the speed of the transmission input shaft, the speed of the clutch 1 driven disc, the speed of the clutch 2 driven disc, After clutch 1 pressure and clutch 2 pressure, judge whether the temperature of the oil thrown out of the clutch oil outlet is ≥ the threshold? If _the temperature of the oil thrown out of the clutch oil outlet is less than the threshold value, then switch to the constant current control mode of the cooling solenoid valve; The rate dΔT _c /dt and the sliding friction power P are used as the input variables of the fuzzy control, and the three-input single-output fuzzy control mode is used to obtain the current of the cooling solenoid valve. It is simple and convenient, and realizes fast and accurate control of the clutch temperature.

Description

Wet DCT Clutch Temperature Control System and Control Method Based on Fuzzy Control

technical field

The invention relates to a wet DCT clutch temperature control system and control method, in particular to a wet DCT clutch temperature control system and control method based on fuzzy control.

Background technique

Currently, two types of transmissions are widely used in conventional motor vehicles. One is a manual transmission, which changes the transmission ratio by switching the gear meshing position in the transmission by shifting the gear lever, so as to achieve the purpose of shifting; for this kind of manual transmission, the driver needs to frequently operate the clutch pedal and change gears during driving. Rod, easy to make the driver feel tired, thus affecting the safety of driving. The other is an automatic transmission, which can automatically change the gear ratio according to the state of the vehicle, which reduces the burden on the driver and improves driving safety. At the same time, the automatic transmission can adapt to various driving conditions and driving styles. Therefore, vehicles equipped with automatic transmissions have gradually become one of the development trends in the automotive industry.

Common automotive automatic transmissions can be divided into four types: hydraulic automatic transmission (AT), electromechanical automatic transmission (AMT), continuously variable transmission (CVT) and dual clutch automatic transmission (DCT). Among them, DCT is a new type of automatic transmission that domestic and foreign automobile companies and researchers have paid attention to in recent years. It realizes power shift through the structure of dual clutches that control odd and even gears respectively. Compared with other automatic transmissions, DCT not only inherits the advantages of high fuel efficiency of AMT, but also retains the advantages of smooth shifting of AT and CVT. Therefore, it has a wide range of applications and a good market prospect.

According to the different types of clutches used in the dual-clutch part of the DCT, it can be divided into two categories: dry DCT and wet DCT. Although the dry DCT has the characteristics of compact structure and high transmission efficiency, due to its small heat capacity, no forced cooling device, and poor heat dissipation performance, it is easy to generate local high temperature, resulting in shortened service life. In comparison, although the wet DCT clutch has a uniform pressure distribution, can accurately control the transmission torque of the clutch, and allows a longer period of starting slippery and high-end starting, the technology is relatively mature and widely used, but it needs to be equipped with a cooling oil forced heat dissipation system , and has a large heat capacity.

Due to the large number of friction pairs in the wet DCT, a large amount of heat energy will be generated in the frequent combination and separation process. In addition, due to its large heat capacity, the speed of heat change is slow. In the case of short coupling and separation time, heat accumulation will be caused due to insufficient cooling of the friction pair of the clutch. Excessive temperature will affect the control accuracy of the clutch, accelerate the wear and thermal failure of the clutch, and affect the life of the clutch. At the same time, if the clutch temperature is too high, the cooling oil will deteriorate beyond the temperature range. Therefore, it is very important to be able to effectively control the temperature of the wet DCT clutch.

At present, vehicles equipped with wet DCT actually control the clutch temperature according to the look-up table method, that is, according to the temperature of the oil thrown out of the clutch oil outlet measured by the clutch temperature sensor, the required temperature is obtained by querying the manually set temperature-cooling flow meter. The flow rate of the cooling solenoid valve, and then according to the current-flow characteristic curve of the cooling solenoid valve itself, the corresponding cooling solenoid valve current value is obtained, thereby controlling the clutch temperature. The cooling solenoid valve is an electro-hydraulic proportional valve, and the current of the solenoid valve is inversely proportional to the cooling flow. However, since the clutch temperature sensor used is a thermistor sensor, its approximate transfer function is a first-order inertial link, which has a large hysteresis, that is, the current temperature can be accurately reflected by the sensor after a period of time, and the usual lag time is greater than 0.5 s, it is easy to cause untimely and insufficient cooling of the clutch and damage the friction plate. In addition, because the clutch temperature control system has the characteristics of nonlinearity, complexity, and dynamics, the control method of the above-mentioned look-up table method results in low control accuracy and has no inhibitory effect on the temperature change rate of the clutch, which will cause large temperature fluctuations and affect the normal operation of the clutch. Work.

Therefore, there is a need in the art for a wet DCT clutch temperature control method that can realize fast and accurate clutch temperature control, so as to control the temperature rise of the clutch, prolong its life and improve the working performance of the DCT vehicle.

Contents of the invention

The technical problem to be solved by the present invention is to provide a wet DCT clutch temperature control system based on fuzzy control to overcome the shortcomings of the clutch oil temperature sensor in the prior art, such as response delay and low accuracy of clutch temperature control.

Another technical problem to be solved by the present invention is to provide a control method for the above-mentioned wet DCT clutch temperature control system based on fuzzy control.

In order to solve the technical problem of the present invention, the technical solution adopted is: the wet DCT clutch temperature control system based on fuzzy control includes the collection of the temperature of the oil thrown out of the clutch oil outlet and the output control of the cooling solenoid valve current, especially,

The composition of described control system is,

The sensor detection module is used to obtain the oil temperature of the clutch oil outlet of the wet DCT, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2;

The signal processing module is used to filter and shape the signal collected by the sensor detection module to suppress noise interference, improve signal quality, and output it to the main control module;

The main control module is composed of a computing module and a control module, wherein,

Calculation module, used to calculate according to the temperature of the oil thrown out of the clutch oil outlet processed by the signal processing module, the speed of the transmission input shaft, the speed of the driven plate of clutch 1, the speed of the driven plate of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 Clutch temperature deviation, clutch temperature deviation change rate and slip power,

The control module is used to judge the applicable control mode according to the signal processed by the signal processing module and the calculation result of the calculation module, and calculate and send a corresponding current signal to the cooling solenoid valve.

As a further improvement of the wet DCT clutch temperature control system based on fuzzy control:

The sensor detection module is preferably composed of a clutch oil temperature sensor, a transmission input shaft speed sensor, a clutch 1 driven disc speed sensor, a clutch 2 driven disc speed sensor, a clutch 1 pressure sensor and a clutch 2 pressure sensor.

In order to solve another technical problem of the present invention, another technical solution adopted is: the control method of the above-mentioned wet DCT clutch temperature control system based on fuzzy control includes the real-time collection of the oil temperature thrown out of the clutch oil outlet and the cooling solenoid valve current The output control, in particular the main steps are as follows:

Step 1, set the clutch temperature threshold to ≥70°C;

Step 2: Collect the oil temperature at the clutch oil outlet of the wet DCT in real time, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2, and judge the oil outlet of the clutch Is the thrown oil temperature ≥ threshold? If the temperature of the oil thrown out of the clutch oil outlet is less than the threshold value, then switch to the cooling solenoid valve current constant control mode;

Step 3, the process of three-input single-output fuzzy control mode is,

Step 3.1, from the temperature of the oil thrown out of the clutch oil outlet, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 collected in step 2 in real time, the clutch pressure is calculated. Temperature deviation ΔT _c , clutch temperature deviation change rate dΔT _c /dt and slip power P, and clutch temperature deviation ΔT _c , clutch temperature deviation change rate dΔT _c /dt and slip power P as input variables, cooling solenoid valve current I is used as the output variable, and the fuzzy set of each input and output variable and its scope of discourse are set at the same time.

Step 3.2, first take the clutch temperature deviation ΔT _c , the clutch temperature deviation change rate dΔT _c /dt and the sliding friction power P as the input variables of the fuzzy control, transform them into their respective domains through scale transformation, and then pass the membership degree of normal distribution function to get the respective fuzzy values,

Step 3.3: Firstly, based on the fuzzy value of the input variable and the set fuzzy control rules, fuzzy reasoning is carried out according to the Mamdani reasoning method, and the output variable is obtained through the fuzzy synthesis operation according to the MIN-MAX method, and then the output variable is converted into After accurate measurement, transform it to the actual output range through scale transformation to obtain the cooling solenoid valve current.

As a further improvement of the control method of the wet DCT clutch temperature control system based on fuzzy control:

Preferably, the current of the cooling solenoid valve in the constant current control mode of the cooling solenoid valve is 1100mA.

Preferably, the formula for calculating the clutch temperature deviation ΔT _c is ΔT _c =T _c −T _o , where T _c is the temperature of the oil thrown out from the clutch oil outlet, and T _o is the temperature threshold.

Preferably, the formula for calculating the clutch temperature deviation change rate dΔT _c /dt is

In the formula, ΔT _c (k-1) is the clutch temperature deviation of the k-1th collection, ΔT _c (k) is the clutch temperature deviation of the k-th collection, and Δt is the sampling period of the clutch temperature deviation.

Preferably, the formula for calculating the slip power P is

$P=|T_{q1}\&Center\; Dot;\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c1})|+|T_{q2}\&Center\; Dot;\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c2})|,$ In the formula, T _q1 and T _q2 are the torque transmitted by clutches 1 and 2 in the slipping state, n _i is the transmission input shaft speed, n _c1 and n _c2 are the driven disc speeds of clutches 1 and 2; among them, the slipping state is calculated The formula of lower clutch transmission torque is

In the formula, Δω _cr is the speed difference between the transmission input shaft and the clutch driven disc, and sign(Δω _cr ) is a sign function, $\mathrm{sign}\left({\mathrm{\Δ\ω}}_{\mathrm{cr}}\right)=\left\{\begin{array}{cc}1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}>0\\ -1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}\≤0\end{array}\right.,$ μ _d is the coefficient of dynamic friction of the friction plate of the wet clutch, S is the effective area of the clutch piston, P _n is the applied pressure on the unit area of the piston of the clutch, Z is the number of friction pairs of the clutch, R ₀ and R ₁ are the outer surface of the friction plate of the clutch, respectively. diameter, inner diameter.

Preferably, the fuzzy set of clutch temperature deviation ΔT _c is {VST, ST, RST, MT, RBT, BT, VBT}, and the fuzzy set of clutch temperature deviation change rate dΔT _c /dt is {NB, NM, NS, O, PS, PM, PB}, the fuzzy set of sliding power P is {VSP, SP, MP, RBP, BP, VBP}, the fuzzy set of cooling solenoid valve current I is {VSI, SI, MI, RBI, BI, VBI },

The basic discourse domain of clutch temperature deviation ΔT _c is [0,70], and the discourse domain is [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14] , then the quantization factor k ₁ =14/70=0.2, the basic discourse domain of the clutch temperature deviation change rate dΔT _c /dt is [-20,20], and the discourse domain is [-6,-5,-4,-3, -2,-1,0,1,2,3,4,5,6], then quantization factor k ₂ =6/20=0.3, the basic discourse domain of sliding power P is [0,20], discourse domain is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], then the quantization factor k ₃ =10/20 = 0.5, and the basic discourse domain of the cooling solenoid valve current I is [0, 1200], the domain of discourse is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], then the scaling factor k ₄ =1200/12=100.

Preferably, the membership function of the normal distribution is

Preferably, the fuzzy control rules are shown in the table below,

, the sentence conjunction and of the rule adopts the intersection operation, and the sentence conjunction also adopts the union operation.

The beneficial effects relative to the prior art are:

By using the present invention to control the temperature of the wet DCT clutch in the bench environment, it is confirmed that the present invention overcomes the deficiencies of the delay in response and the low accuracy of clutch temperature control existing in the clutch oil temperature sensor in the prior art, and realizes the control of the wet DCT clutch. Fast and accurate control of wet DCT clutch temperature.

Description of drawings

Fig. 1 is a kind of basic structural schematic diagram of the control system in the present invention.

Fig. 2 is a process diagram of basic steps of the control method in the present invention.

Fig. 3 is a process diagram of fuzzy control in the control method of the present invention.

Fig. 4 is one of the effect diagrams after using the present invention to control the wet DCT clutch. Among them, Figure 4a is the clutch temperature deviation curve; Figure 4b is the clutch slip power curve; Figure 4c is the clutch temperature deviation change rate curve; Figure 4d is the cooling solenoid valve current curve.

Detailed ways

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and are only used to explain the present invention, rather than to limit the present invention.

Referring to Fig. 1, the wet DCT clutch temperature control system based on fuzzy control is placed outside the automatic transmission electronic control unit (TCU), which includes a sensor detection module, a signal processing module, and a main control module, where the main control module contains a calculation module and control module. in,

The sensor detection module is used to obtain the oil temperature of the clutch oil outlet of the wet DCT, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2; usually, The sensor detection module uses clutch oil temperature sensor, transmission input shaft speed sensor, clutch 1 driven disc speed sensor, clutch 2 driven disc speed sensor, clutch 1 pressure sensor and clutch 2 pressure sensor to obtain information. Or, the temperature of the oil thrown out of the clutch oil outlet, the speed of the transmission input shaft, the speed of the driven plate of clutch 1, the speed of the driven plate of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 can also be controlled by the vehicle through the communication bus (such as CAN bus). In this case, a communication module suitable for this bus can be embedded inside the TCU.

The signal processing module is used to filter and shape the signal collected by the sensor detection module to suppress noise interference and improve signal quality, and output the signal to the main control module.

The calculation module in the main control module is used for the temperature of the oil thrown out of the clutch oil outlet, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the clutch 2 Pressure calculation clutch temperature deviation, clutch temperature deviation change rate and slip power. In this embodiment, the sampling period of the temperature deviation of the clutch is 10 ms.

The control module in the main control module mainly involves two control methods, which are cooling solenoid valve current constant control method and three-input single-output fuzzy control method. The three inputs refer to the clutch temperature deviation, the rate of change of the clutch temperature deviation and the sliding friction power, and the single output refers to the cooling solenoid valve current. The above two control methods can be converted to each other under certain conditions.

Referring to Fig. 2 and Fig. 3, the control method of the present invention comprises the real-time acquisition of the temperature of the oil thrown out of the clutch oil outlet and the output control of the cooling solenoid valve current, and its main steps are as follows:

Step 1, set the clutch temperature threshold to be ≥70°C.

Step 2: Collect the oil temperature at the clutch oil outlet of the wet DCT in real time, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2, and judge the oil outlet of the clutch Is the thrown oil temperature ≥ threshold? If the temperature of the oil thrown out of the clutch oil outlet is less than the threshold value, then switch to the cooling solenoid valve current constant control mode, that is, set the current of the cooling solenoid valve to 1100mA. If the temperature of the oil thrown out of the clutch oil outlet is greater than or equal to the threshold value, then switch to the three-input single-output fuzzy control mode.

Step 3, the process of three-input single-output fuzzy control mode is,

In step 3.1, the clutch temperature is obtained by calculating the temperature of the oil thrown out of the clutch oil outlet, the speed of the transmission input shaft, the speed of the driven plate of clutch 1, the speed of the driven plate of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 collected in real time in step 2 deviation ΔT _c , clutch temperature deviation change rate dΔT _c /dt and slip power P; where,

The formula for calculating the clutch temperature deviation ΔT _c is ΔT _c =T _c -T _o , where T _c is the temperature of the oil thrown out from the clutch oil outlet, and T _o is the temperature threshold.

The formula for calculating the clutch temperature deviation change rate dΔT _c /dt is

In the formula, ΔT _c (k-1) is the clutch temperature deviation of the k-1th collection, ΔT _c (k) is the clutch temperature deviation of the k-th collection, and Δt is the sampling period of the clutch temperature deviation.

The formula for calculating the sliding friction power P is

$P=|T_{q1}\·\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c1})|+|T_{q2}\&Center\; Dot;\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c2})|,$ In the formula, T _q1 and T _q2 are the torque transmitted by clutches 1 and 2 in the slipping state, n _i is the transmission input shaft speed, n _c1 and n _c2 are the driven disc speeds of clutches 1 and 2; among them, the slipping state is calculated The formula of lower clutch transmission torque is

In the formula, Δω _cr is the speed difference between the transmission input shaft and the clutch driven disc, and sign(Δω _cr ) is a sign function, $\mathrm{sign}\left({\mathrm{\Δ\ω}}_{\mathrm{cr}}\right)=\left\{\begin{array}{cc}1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}>0\\ -1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}\≤0\end{array}\right.,$ μ _d is the coefficient of dynamic friction of the friction plate of the wet clutch, S is the effective area of the clutch piston, P _n is the applied pressure on the unit area of the piston of the clutch, Z is the number of friction pairs of the clutch, R ₀ and R ₁ are the outer surface of the friction plate of the clutch, respectively. diameter, inner diameter.

The clutch temperature deviation ΔT _c , the clutch temperature deviation change rate dΔT _c /dt and the friction power P are used as input variables, and the cooling solenoid valve current I is used as an output variable. At the same time, the fuzzy set of each input and output variable and its scope of discourse are set . in,

The fuzzy set of clutch temperature deviation ΔT _c is {VST, ST, RST, MT, RBT, BT, VBT}, and the fuzzy set of clutch temperature deviation change rate dΔT _c /dt is {NB, NM, NS, O, PS, PM , PB}, the fuzzy set of sliding power P is {VSP, SP, MP, RBP, BP, VBP}, the fuzzy set of cooling solenoid valve current I is {VSI, SI, MI, RBI, BI, VBI},

The basic discourse domain of clutch temperature deviation ΔT _c is [0,70], and the discourse domain is [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14] , then the quantization factor k ₁ =14/70=0.2, the basic discourse domain of the clutch temperature deviation change rate dΔT _c /dt is [-20,20], and the discourse domain is [-6,-5,-4,-3, -2,-1,0,1,2,3,4,5,6], then quantization factor k ₂ =6/20=0.3, the basic discourse domain of sliding power P is [0,20], discourse domain is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], then the quantization factor k ₃ =10/20 = 0.5, and the basic discourse domain of the cooling solenoid valve current I is [0, 1200], the domain of discourse is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], then the scaling factor k ₄ =1200/12=100.

Step 3.2, first take the clutch temperature deviation ΔT _c , the clutch temperature deviation change rate dΔT _c /dt and the sliding friction power P as the input variables of the fuzzy control, and transform them to their respective domains through scale transformation; then pass the membership degree of the normal distribution function to obtain their respective fuzzy values; among them, the membership function of the normal distribution is $\mathrm{\μ}\left(x\right)=\exp [-\frac{{(x-a)}^2}{2{\mathrm{\σ}}^2}].$

In step 3.3, the fuzzy value of the input variable and the set fuzzy control rules are used to carry out fuzzy inference according to the Mamdani reasoning method, and the fuzzy synthesis operation is carried out according to the MIN-MAX method to obtain the output variable; among them, the fuzzy control rules are shown in the following table ,

, where the regular sentence conjunction and uses the intersection operation, the sentence conjunction also adopts the union operation, and the fuzzy implication relationship of Mamdani reasoning method is represented by the Cartesian product.

After the output variable is converted into an accurate quantity by the center of gravity method, the scale is converted to the actual output range to obtain the cooling solenoid valve current, that is, the center of gravity method is used for defuzzification, and the accurate value of the output quantity is finally obtained, and then multiplied by the value in step 3.1 The proportional factor k ₄ obtains the current value of the cooling solenoid valve.

In order to verify the implementation effect of the present invention, the temperature control of the wet DCT clutch is verified through the control system embedded in the TCU under the bench environment. The control effect diagram shown in Figure 4 is obtained, from which it can be seen that the control method of the present invention has a good inhibitory effect on the clutch temperature change rate and the change of the sliding friction power, and the robustness is strong, and at the same time It can also realize fast and accurate control of clutch temperature.

The structure, features and effects of the present invention have been described in detail above based on the embodiments shown in the drawings, which are only preferred embodiments of the present invention, but the present invention does not limit the scope of implementation as shown in the drawings. Changes made to the idea of the present invention, or modifications to equivalent embodiments that are equivalent changes, and still within the spirit covered by the description and illustrations, shall be within the protection scope of the present invention.

Claims (10)

1. A wet DCT clutch temperature control system based on fuzzy control, comprising the collection of clutch oil outlet throwing off oil temperature and the output control of cooling solenoid valve current, characterized in that: The composition of described control system is, The sensor detection module is used to obtain the oil temperature of the clutch oil outlet of the wet DCT, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2; The signal processing module is used to filter and shape the signal collected by the sensor detection module to suppress noise interference, improve signal quality, and output it to the main control module; The main control module is composed of a computing module and a control module, wherein, Calculation module, used to calculate according to the temperature of the oil thrown out of the clutch oil outlet processed by the signal processing module, the speed of the transmission input shaft, the speed of the driven plate of clutch 1, the speed of the driven plate of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 Clutch temperature deviation, clutch temperature deviation change rate and slip power, The control module is used to judge the applicable control mode according to the signal processed by the signal processing module and the calculation result of the calculation module, and calculate and send a corresponding current signal to the cooling solenoid valve. 2. The wet DCT clutch temperature control system based on fuzzy control according to claim 1, characterized in that the sensor detection module is composed of clutch oil temperature sensor, transmission input shaft speed sensor, clutch 1 driven disc speed sensor, clutch 2 driven Disc speed sensor, clutch 1 pressure sensor and clutch 2 pressure sensor. 3. a control method based on the wet DCT clutch temperature control system of fuzzy control according to claim 1, comprising the real-time collection of clutch oil outlet and the control of cooling solenoid valve current of oil temperature, it is characterized in that main steps are as follows: Step 1, set the clutch temperature threshold to ≥70°C; Step 2: Collect the oil temperature at the clutch oil outlet of the wet DCT in real time, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2, and judge the oil outlet of the clutch Is the thrown oil temperature ≥ threshold? If the temperature of the oil thrown out of the clutch oil outlet is less than the threshold value, then switch to the cooling solenoid valve current constant control mode; Step 3, the process of three-input single-output fuzzy control mode is, Step 3.1, from the temperature of the oil thrown out of the clutch oil outlet, the speed of the transmission input shaft, the speed of the driven disc of clutch 1, the speed of the driven disc of clutch 2, the pressure of clutch 1 and the pressure of clutch 2 collected in step 2 in real time, the clutch pressure is calculated. Temperature deviation ΔT _c , clutch temperature deviation change rate dΔT _c /dt and slip power P, and clutch temperature deviation ΔT _c , clutch temperature deviation change rate dΔT _c /dt and slip power P as input variables, cooling solenoid valve current I is used as the output variable, and the fuzzy set of each input and output variable and its scope of discourse are set at the same time. Step 3.2, first take the clutch temperature deviation ΔT _c , the clutch temperature deviation change rate dΔT _c /dt and the sliding friction power P as the input variables of the fuzzy control, transform them into their respective domains through scale transformation, and then pass the membership degree of normal distribution function to get the respective fuzzy values, Step 3.3: Firstly, based on the fuzzy value of the input variable and the set fuzzy control rules, fuzzy reasoning is carried out according to the Mamdani reasoning method, and the output variable is obtained through the fuzzy synthesis operation according to the MIN-MAX method, and then the output variable is converted into After accurate measurement, the scale is converted to the actual output range to obtain the cooling solenoid valve current. 4. The control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, characterized in that the current of the cooling solenoid valve in the cooling solenoid valve current constant control mode is 1100mA. 5. The control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, wherein the formula for calculating the clutch temperature deviation ΔT _c is ΔT _c =T _c -T _o , and T _c in the formula is The temperature of the oil thrown out of the clutch oil outlet, T _o is the temperature threshold. 6. The control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, wherein the formula for calculating the clutch temperature deviation change rate dΔT _c /dt is: In the formula, ΔT _c (k-1) is the clutch temperature deviation of the k-1th collection, ΔT _c (k) is the clutch temperature deviation of the k-th collection, and Δt is the sampling period of the clutch temperature deviation. 7. the control method of the wet type DCT clutch temperature control system based on fuzzy control according to claim 3, it is characterized in that the formula of calculating slip power P is: $P=|T_{q1}\·\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c1})|+|T_{q2}\&Center\; Dot;\frac{2\mathrm{\π}}{60}({\mathrm{no}}_i-{\mathrm{no}}_{c2})|,$ In the formula, T _q1 and T _q2 are the torque transmitted by clutches 1 and 2 in the slipping state, n _i is the transmission input shaft speed, n _c1 and n _c2 are the driven disc speeds of clutches 1 and 2; among them, the slipping state is calculated The formula of lower clutch transmission torque is In the formula, Δω _cr is the speed difference between the transmission input shaft and the clutch driven disc, and sign(Δω _cr ) is a sign function, $\mathrm{sign}\left({\mathrm{\Δ\ω}}_{\mathrm{cr}}\right)=\left\{\begin{array}{cc}1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}>0\\ -1,& {\mathrm{\Δ\ω}}_{\mathrm{cr}}\≤0\end{array}\right.,$ μ _d is the coefficient of dynamic friction of the friction plate of the wet clutch, S is the effective area of the clutch piston, P _n is the applied pressure on the unit area of the piston of the clutch, Z is the number of friction pairs of the clutch, R ₀ and R ₁ are the outer surface of the friction plate of the clutch, respectively. diameter, inner diameter. 8. the control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, is characterized in that The fuzzy set of clutch temperature deviation ΔT _c is {VST, ST, RST, MT, RBT, BT, VBT}, and the fuzzy set of clutch temperature deviation change rate dΔT _c /dt is {NB, NM, NS, O, PS, PM , PB}, the fuzzy set of sliding power P is {VSP, SP, MP, RBP, BP, VBP}, the fuzzy set of cooling solenoid valve current I is {VSI, SI, MI, RBI, BI, VBI}, The basic discourse domain of clutch temperature deviation ΔT _c is [0,70], and the discourse domain is [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14] , then the quantization factor k ₁ =14/70=0.2, the basic discourse domain of the clutch temperature deviation change rate dΔT _c /dt is [-20,20], and the discourse domain is [-6,-5,-4,-3, -2,-1,0,1,2,3,4,5,6], then quantization factor k ₂ =6/20=0.3, the basic discourse domain of sliding power P is [0,20], discourse domain is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], then the quantization factor k ₃ =10/20 = 0.5, and the basic discourse domain of the cooling solenoid valve current I is [0, 1200], the domain of discourse is [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], then the scaling factor k ₄ =1200/12=100. 9. the control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, it is characterized in that the membership function of normal distribution is 10. The control method of the wet DCT clutch temperature control system based on fuzzy control according to claim 3, characterized in that the fuzzy control rules are as shown in the following table, , the sentence conjunction and of the rule adopts the intersection operation, and the sentence conjunction also adopts the union operation.