Boost pressure control method for exhaust gas turbocharger system

Abstract

The present invention discloses a method for controlling the boost pressure of an exhaust gas turbocharger system, which obtains the boost pressure difference and the rate of change of the boost pressure difference of the exhaust gas turbocharger system; the boost pressure difference is the difference between the target boost pressure of the exhaust gas turbocharger system and the actual boost pressure, and the rate of change of the boost pressure difference is the first-order derivative of the boost pressure difference with time; the boost pressure difference and the rate of change of the boost pressure difference are fuzzy processed to obtain a first fuzzy quantity and a second fuzzy quantity respectively; the first fuzzy quantity and the second fuzzy quantity are input into a preset fuzzy rule table to obtain a fuzzy control quantity; the fuzzy control quantity is defuzzified to obtain a fuzzy control target opening; the fuzzy control target opening is used to control a boost actuator of the exhaust gas turbocharger system.

Description

Technical Field

[0001] The invention relates to the field of engine control, and in particular to a boost pressure control method for an exhaust gas turbocharger system. Background Art

[0002] In order to respond to the engine intake boost and engine torque increase request, a boost system is used to achieve more exhaust energy to achieve intake boost. The boost control adopts a closed-loop control method. The current conventional method is to use the PID control method, but as the accuracy of engine torque responsiveness becomes higher and higher, it is necessary to further improve the accuracy and stability of boost control. Summary of the invention

[0003] The object of the present invention is to provide a boost pressure control method for an exhaust gas turbocharger system to improve the accuracy and stability of boost pressure control.

[0004] In order to solve the above technical problems, the present invention provides a technical solution: a method for controlling the boost pressure of an exhaust gas turbocharger system, the method comprising the following steps:

[0005] Obtaining a boost pressure difference and a rate of change of the boost pressure difference of the exhaust gas turbocharger system; the boost pressure difference is the difference between a target boost pressure and an actual boost pressure of the exhaust gas turbocharger system, and the rate of change of the boost pressure difference is the first-order derivative of the boost pressure difference with time;

[0006] Performing fuzzy processing on the boost pressure difference and the rate of change of the boost pressure difference to obtain a first fuzzy value and a second fuzzy value respectively;

[0007] Inputting the first fuzzy quantity and the second fuzzy quantity into a preset fuzzy rule table to obtain a fuzzy control quantity;

[0008] The fuzzy control quantity is defuzzified to obtain a fuzzy control target opening; the fuzzy control target opening is used to control a boost actuator of an exhaust gas turbocharger system.

[0009] According to the above scheme, the process of fuzzy processing of the boost pressure difference to obtain the first fuzzy quantity is as follows;

[0010] The domain of boost pressure difference is set to [-A, A], the unit is kPa, and A is a preset value; the first fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB, which represent negative large, negative small, zero, positive small, and positive large, respectively;

[0011] Determining the corresponding relationship between the boost pressure difference and the first fuzzy quantity and establishing a first membership function;

[0012] The process of fuzzy processing the boost pressure difference change rate to obtain the second fuzzy quantity is as follows;

[0013] The domain of the boost pressure difference change rate is set to [-B, B], the unit is kPa / s, and B is a preset value; the second fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB, which represent negative large, negative small, zero, positive small, and positive large, respectively;

[0014] The corresponding relationship between the boost pressure difference change rate and the second fuzzy quantity is determined and a second membership function is established.

[0015] According to the above scheme, the corresponding relationship between the first fuzzy quantity, the second fuzzy quantity and the fuzzy control quantity in the preset fuzzy rule table is as follows;

[0016] When the first fuzzy amount is NB and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0017] When the first fuzzy amount is NB and the second fuzzy amount is NS, the fuzzy control amount is NB;

[0018] When the first fuzzy amount is NB and the second fuzzy amount is ZO, the fuzzy control amount is NB;

[0019] When the first fuzzy amount is NB and the second fuzzy amount is PS, the fuzzy control amount is NM;

[0020] When the first fuzzy amount is NB and the second fuzzy amount is PB, the fuzzy control amount is NS;

[0021] When the first fuzzy amount is NS and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0022] When the first fuzzy amount is NS and the second fuzzy amount is NS, the fuzzy control amount is NM;

[0023] When the first fuzzy amount is NS and the second fuzzy amount is ZO, the fuzzy control amount is NS;

[0024] When the first fuzzy value is NS and the second fuzzy value is PS, the fuzzy control value is ZO;

[0025] When the first fuzzy quantity is NS and the second fuzzy quantity is PB, the fuzzy control quantity is PS;

[0026] When the first fuzzy amount is ZO and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0027] When the first fuzzy amount is ZO and the second fuzzy amount is NS, the fuzzy control amount is NS;

[0028] When the first fuzzy amount is ZO and the second fuzzy amount is ZO, the fuzzy control amount is ZO;

[0029] When the first fuzzy amount is ZO and the second fuzzy amount is PS, the fuzzy control amount is PS;

[0030] When the first fuzzy quantity is ZO and the second fuzzy quantity is PB, the fuzzy control quantity is PM;

[0031] When the first fuzzy amount is PS and the second fuzzy amount is NB, the fuzzy control amount is ZO;

[0032] When the first fuzzy amount is PS and the second fuzzy amount is NS, the fuzzy control amount is PS;

[0033] When the first fuzzy amount is PS and the second fuzzy amount is ZO, the fuzzy control amount is PM;

[0034] When the first fuzzy quantity is PS and the second fuzzy quantity is PS, the fuzzy control quantity is PM;

[0035] When the first fuzzy quantity is PS and the second fuzzy quantity is PB, the fuzzy control quantity is PB;

[0036] When the first fuzzy amount is PB and the second fuzzy amount is NB, the fuzzy control amount is NS;

[0037] When the first fuzzy quantity is PB and the second fuzzy quantity is NS, the fuzzy control quantity is PS;

[0038] When the first fuzzy quantity is PB and the second fuzzy quantity is ZO, the fuzzy control quantity is PM;

[0039] When the first fuzzy quantity is PB and the second fuzzy quantity is PS, the fuzzy control quantity is PM;

[0040] When the first fuzzy quantity is PB and the second fuzzy quantity is PB, the fuzzy control quantity is PB;

[0041] Among them, NB, NM, NS, ZO, PS, PM, and PB represent large negative, medium negative, small negative, zero, small positive, medium positive, and large positive, respectively.

[0042] According to the above scheme, the defuzzification method adopts the centroid method.

[0043] According to the above scheme, if the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 10 kPa, and the boost pressure difference change rate dp Err The duration of maintaining no less than 20kPa / s exceeds the preset time t 1 , then get t 1 The target boost pressure ratio average value r BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0044] Then the average engine speed will be the same as n Avg 、The average value of target boost pressure ratio rBoostRatioAvg The domain of the boost pressure difference under the working conditions, the domain of the boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset first update rule.

[0045] According to the above scheme, if the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 2 kPa, and the boost pressure difference change rate dp Err The duration of maintaining no less than 8kPa / s exceeds the preset time t 2 , then get t 2 The target boost pressure ratio average value r BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0046] Then, the average engine speed n will be the same Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of the boost pressure difference under the working conditions, the domain of the boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset second update rule.

[0047] According to the above scheme, if the boost pressure difference p Err The absolute value of the boost pressure difference is always kept less than 2kPa, and the boost pressure difference change rate dp Err If the pressure is always kept below 8 kPa / s, the average value of the target boost pressure ratio r within the duration is obtained. BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0048] Then the average engine speed will be the same as n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of boost pressure difference under the working condition, the domain of boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset third update rule.

[0049] According to the above scheme, the first updating rule is as follows:

[0050] 1) Update the boost pressure difference domain to [-10, p ErrAvg], the domain of the boost pressure difference change rate is updated to [-20, dp ErrAvg ];

[0051] 2) Update PB and NB in ​​the first membership function to,

[0052] PB=k1×PB(Z)+(1-k1)×p ErrAvg

[0053] NB=k1×NB(Z)+(1-k1)×p ErrAvg

[0054] Where PB(Z) is the PB before updating, NB(Z) is the NB before updating, and k1 is a preset constant;

[0055] 3) Update PB and NB in ​​the second membership function to,

[0056] PB=k2×PB(Z)+(1-k2)×dp ErrAvg

[0057] NB=k2×NB(Z)+(1-k2)×dp ErrAvg

[0058] Where k2 is a preset constant.

[0059] According to the above scheme, the second update rule is as follows:

[0060] 1) Update NS and PS in the first membership function to,

[0061] NS=k3×NS(Z)+(1-k3)×p ErrAvg

[0062] PS=k3×PS(Z)+(1-k3)×p ErrAvg

[0063] Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k3 is a preset constant;

[0064] 2) Update NS and PS in the second membership function to,

[0065] PS=k4×PS(Z)+(1-k4)×dp ErrAvg

[0066] NS=k4×NS(Z)+(1-k4)×dp ErrrAvg

[0067] Among them, k4 is a preset constant.

[0068] According to the above scheme, the third update rule is as follows:

[0069] 1) Update NS and PS in the first membership function to,

[0070] NS=k5×NS(Z)+(1-k5)×p ErrAvg

[0071] PS=k5×PS(Z)+(1-k5)×p ErrAvg

[0072] Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k5 is a preset constant;

[0073] 2) Update NS and PS in the second membership function to:

[0074] NS=k6×NS(Z)+(1-k6)×dp ErrAvg

[0075] PS=k6×PS(Z)+(1-k6)×dp ErrAvg

[0076] Among them, k6 is a preset constant.

[0077] The beneficial effects of the present invention are as follows: through the fuzzy control strategy, the knowledge and thinking, learning and reasoning, association and decision-making process of relevant experts are identified and modeled by computers, and controlled, thereby further improving the control accuracy and stability of supercharging. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is a flow chart of a method for controlling boost pressure of an exhaust gas turbocharger system according to a first embodiment of the present invention;

[0079] Figure 2 This is a schematic diagram of a first membership function in accordance with the first embodiment of the present invention;

[0080] Figure 3 This is a schematic diagram of a second membership function in accordance with the first embodiment of the present invention;

[0081] Figure 4 Schematic diagram of the membership function between the fuzzy control amount and the fuzzy control target opening degree according to the first embodiment of the present invention;

[0082] Figure 5 Schematic diagram of a fuzzy controller according to an embodiment of the present invention. DETAILED DESCRIPTION

[0083] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0084] Embodiment 1:

[0085] A method for controlling boost pressure of an exhaust gas turbocharger system, the method comprising the following steps:

[0086] Obtaining the boost pressure difference and the rate of change of the boost pressure difference of the exhaust gas turbocharger system (the method for obtaining the boost pressure difference and the rate of change of the boost pressure difference is disclosed in the prior art CN201910988050.8 "Exhaust Gas Turbine Engine Boost Closed-Loop Adaptive System and Control Method"); the boost pressure difference is the difference between the target boost pressure and the actual boost pressure of the exhaust gas turbocharger system, and the rate of change of the boost pressure difference is the first-order derivative of the boost pressure difference with time;

[0087] Performing fuzzy processing on the boost pressure difference and the rate of change of the boost pressure difference to obtain a first fuzzy value and a second fuzzy value respectively;

[0088] Inputting the first fuzzy quantity and the second fuzzy quantity into a preset fuzzy rule table to obtain a fuzzy control quantity;

[0089] The fuzzy control quantity is defuzzified to obtain a fuzzy control target opening; the fuzzy control target opening is used to control a boost actuator of an exhaust gas turbocharger system.

[0090] It is understandable that the realization of fuzzy control requires the establishment of a membership function. There are certain principles for the establishment of a membership function. Since the fuzzy control process is not sensitive to the shape of the membership function of the linguistic variable value, but is only sensitive to the range of the membership degree, in this embodiment, a triangular or trapezoidal membership function can be used, which is conducive to calculating the membership degree.

[0091] Before executing the above steps, the preset fuzzy control rules can be preliminarily organized into a fuzzy control rule table and stored. The construction process of the fuzzy control rule table is described below with a specific example. Of course, in the specific implementation process, the number of fuzzy sets divided and the setting range of the domain can be set according to actual needs and multiple experiments.

[0092] Further, see Figure 2 , the process of fuzzifying the boost pressure difference to obtain the first fuzzy quantity is as follows;

[0093] The domain of the boost pressure difference is set to [-10, 10], with the unit being kPa (it should be noted that the domain is selected as [-10, 10] because the control rules are adjusted only when the boost pressure difference is between -10kPa and 10kPa, thereby improving the control accuracy. When the boost pressure difference is lower than -10kPa or higher than 10kPa, the pressure difference range is relatively large, and standard conventional PID control is adopted); a large boost pressure difference adopts "large step" to improve the control response rate, and a small boost pressure difference adopts "small step" to control the response accuracy); the first fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB;

[0094] When the boost pressure difference is about -8 kPa, the corresponding first fuzzy quantity is NB;

[0095] When the boost pressure difference is about -2 kPa, the corresponding first fuzzy quantity is NS;

[0096] When the boost pressure difference is about 0 kPa, the corresponding first fuzzy quantity is ZO;

[0097] When the boost pressure difference is about 2 kPa, the corresponding first fuzzy quantity is PS;

[0098] When the boost pressure difference is about 8 kPa, the corresponding first fuzzy quantity is PB;

[0099] Establishing a first membership function based on the corresponding relationship between the boost pressure difference and the first fuzzy quantity;

[0100] See also Figure 3 , the process of fuzzy processing the boost pressure difference change rate to obtain the second fuzzy quantity is as follows;

[0101] The domain of the boost pressure difference change rate is set to [-20, 20], with the unit of kPa / s (the reason for selecting the domain as [-20, 20] is that the control rule is adjusted only when the boost pressure difference change rate is between -20kPa / s and 20kPa / s (the boost pressure difference change rate is not large), thereby improving the control accuracy. When the boost pressure difference change rate is large, a "large step" is used to improve the control response time, and when the boost pressure difference change rate is small, a "small step" is used to control the response accuracy). When the boost pressure difference change rate is lower than -20kPa / s or higher than 20kPa / s, the pressure difference range is large, and standard conventional PID control is adopted.); The second fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB;

[0102] When the boost pressure difference change rate is about -15 kPa / s, the corresponding second fuzzy quantity is NB;

[0103] When the boost pressure difference change rate is about -8 kPa / s, the corresponding second fuzzy quantity is NS;

[0104] When the boost pressure difference change rate is about 0 kPa / s, the corresponding second fuzzy quantity is ZO;

[0105] When the boost pressure difference change rate is about 8 kPa / s, the corresponding second fuzzy quantity is PS;

[0106] When the boost pressure difference change rate is about 15 kPa / s, the corresponding second fuzzy quantity is PB;

[0107] A second membership function is established based on the corresponding relationship between the boost pressure difference change rate and the second fuzzy quantity.

[0108] Furthermore, the corresponding relationship between the first fuzzy quantity, the second fuzzy quantity and the fuzzy control quantity in the preset fuzzy rule table is as follows;

[0109] When the first fuzzy amount is NB and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0110] When the first fuzzy amount is NB and the second fuzzy amount is NS, the fuzzy control amount is NB;

[0111] When the first fuzzy amount is NB and the second fuzzy amount is ZO, the fuzzy control amount is NB;

[0112] When the first fuzzy amount is NB and the second fuzzy amount is PS, the fuzzy control amount is NM;

[0113] When the first fuzzy amount is NB and the second fuzzy amount is PB, the fuzzy control amount is NS;

[0114] When the first fuzzy amount is NS and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0115] When the first fuzzy amount is NS and the second fuzzy amount is NS, the fuzzy control amount is NM;

[0116] When the first fuzzy amount is NS and the second fuzzy amount is ZO, the fuzzy control amount is NS;

[0117] When the first fuzzy value is NS and the second fuzzy value is PS, the fuzzy control value is ZO;

[0118] When the first fuzzy quantity is NS and the second fuzzy quantity is PB, the fuzzy control quantity is PS;

[0119] When the first fuzzy amount is ZO and the second fuzzy amount is NB, the fuzzy control amount is NB;

[0120] When the first fuzzy amount is ZO and the second fuzzy amount is NS, the fuzzy control amount is NS;

[0121] When the first fuzzy amount is ZO and the second fuzzy amount is ZO, the fuzzy control amount is ZO;

[0122] When the first fuzzy amount is ZO and the second fuzzy amount is PS, the fuzzy control amount is PS;

[0123] When the first fuzzy quantity is ZO and the second fuzzy quantity is PB, the fuzzy control quantity is PM;

[0124] When the first fuzzy amount is PS and the second fuzzy amount is NB, the fuzzy control amount is ZO;

[0125] When the first fuzzy amount is PS and the second fuzzy amount is NS, the fuzzy control amount is PS;

[0126] When the first fuzzy amount is PS and the second fuzzy amount is ZO, the fuzzy control amount is PM;

[0127] When the first fuzzy quantity is PS and the second fuzzy quantity is PS, the fuzzy control quantity is PM;

[0128] When the first fuzzy quantity is PS and the second fuzzy quantity is PB, the fuzzy control quantity is PB;

[0129] When the first fuzzy amount is PB and the second fuzzy amount is NB, the fuzzy control amount is NS;

[0130] When the first fuzzy quantity is PB and the second fuzzy quantity is NS, the fuzzy control quantity is PS;

[0131] When the first fuzzy quantity is PB and the second fuzzy quantity is ZO, the fuzzy control quantity is PM;

[0132] When the first fuzzy quantity is PB and the second fuzzy quantity is PS, the fuzzy control quantity is PM;

[0133] When the first fuzzy quantity is PB and the second fuzzy quantity is PB, the fuzzy control quantity is PB;

[0134] As shown in the following table:

[0135]

[0136] NB, NM, NS, ZO, PS, PM, and PB respectively represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large.

[0137] For example, the standard for designing fuzzy control rules is: "The more the target boost pressure is higher than the actual boost pressure and the faster the boost pressure rises, the greater the increase in the fuzzy control amount"; "The target boost pressure is close to the actual boost pressure and the boost pressure does not change much, and the fuzzy control amount remains basically unchanged"; "The more the target boost pressure is lower than the actual boost pressure and the faster the boost pressure drops, the greater the decrease in the fuzzy control amount".

[0138] The corresponding 25 fuzzy control rules are as follows:

[0139] Rule 1: if the target boost pressure is much smaller than the actual boost pressure (i.e. the first fuzzy value is NB) and the boost pressure drops rapidly (the second fuzzy value is NB), then the fuzzy control value is greatly reduced (the fuzzy control value is NB);

[0140] Rule 2: if the target boost pressure is much smaller than the actual boost pressure (i.e. the first fuzzy value is NB) and the boost pressure decreases slowly (the second fuzzy value is NS), then the fuzzy control value is greatly reduced (the fuzzy control value is NB);

[0141] Rule 3: if the target boost pressure is much smaller than the actual boost pressure and the boost pressure is basically unchanged (the second fuzzy value is ZO), then greatly reduce the fuzzy control value;

[0142] Rule 4: if the target boost pressure is much lower than the actual boost pressure and the boost pressure rises slowly (the second fuzzy value is PS), then moderately reduce the fuzzy control value (the fuzzy control value is NM);

[0143] Rule 5: if the target boost pressure is much lower than the actual boost pressure and the boost pressure rises rapidly (the second fuzzy value is PB), then slightly reduce the fuzzy control value (the fuzzy control value is NS);

[0144] Rule 6: if the target boost pressure is slightly lower than the actual boost pressure (the first fuzzy value is NS) and the boost pressure drops rapidly, then greatly reduce the fuzzy control value;

[0145] Rule 7: If the target boost pressure is slightly lower than the actual boost pressure and the boost pressure decreases slowly, then moderately reduce the fuzzy control amount;

[0146] Rule 8: If the target boost pressure is slightly lower than the actual boost pressure and the boost pressure remains basically unchanged, then slightly reduce the fuzzy control amount;

[0147] Rule 9: If the target boost pressure is slightly lower than the actual boost pressure and the boost pressure rises slowly, then the fuzzy control amount is basically maintained;

[0148] Rule 10: If the target boost pressure is slightly lower than the actual boost pressure and the boost pressure rises quickly, then slightly increase the fuzzy control amount;

[0149] Rule 11: If the target boost pressure is basically equal to the actual boost pressure and the boost pressure drops rapidly, then the fuzzy control amount is greatly reduced;

[0150] Rule 12: If the target boost pressure is basically equal to the actual boost pressure and the boost pressure decreases slowly, then slightly reduce the fuzzy control amount;

[0151] Rule 13: If the target boost pressure is substantially equal to the actual boost pressure and the boost pressure is substantially unchanged, then the fuzzy control amount is substantially maintained;

[0152] Rule 14: If the target boost pressure is basically equal to the actual boost pressure and the boost pressure rises slowly, then slightly increase the fuzzy control amount;

[0153] Rule 15: If the target boost pressure is basically equal to the actual boost pressure and the boost pressure rises quickly, then increase the fuzzy control amount moderately;

[0154] Rule 16: If the target boost pressure is slightly higher than the actual boost pressure and the boost pressure drops rapidly, then moderately reduce the fuzzy control amount;

[0155] Rule 17: If the target boost pressure is slightly higher than the actual boost pressure and the boost pressure decreases slowly, then the fuzzy control amount is basically maintained;

[0156] Rule 18: If the target boost pressure is slightly higher than the actual boost pressure and the boost pressure remains basically unchanged, then slightly increase the fuzzy control amount;

[0157] Rule 19: If the target boost pressure is slightly higher than the actual boost pressure and the boost pressure rises slowly, then increase the fuzzy control amount moderately;

[0158] Rule 20: If the target boost pressure is slightly higher than the actual boost pressure and the boost pressure rises quickly, then increase the fuzzy control amount moderately;

[0159] Rule 21: If the target boost pressure is much higher than the actual boost pressure and the boost pressure drops rapidly, then slightly reduce the fuzzy control amount;

[0160] Rule 22: If the target boost pressure is much higher than the actual boost pressure and the boost pressure decreases slowly, then slightly increase the fuzzy control amount;

[0161] Rule 23: If the target boost pressure is much higher than the actual boost pressure and the boost pressure remains basically unchanged, then increase the fuzzy control amount moderately;

[0162] Rule 24: If the target boost pressure is much higher than the actual boost pressure and the boost pressure rises slowly, then increase the fuzzy control amount moderately;

[0163] Rule 25: If the target boost pressure is much higher than the actual boost pressure and the boost pressure rises rapidly, then greatly increase the fuzzy control amount.

[0164] Further, see Figure 4 , the defuzzification method adopts the centroid method (other embodiments of the present invention adopt the maximum membership method or the centroid method or the weighted average method); specifically,

[0165] The following formula is used to calculate the fuzzy control output u corresponding to the boost pressure difference and the boost pressure difference change rate. The fuzzy control output u is the fuzzy control correction coefficient r fuzzy .

[0166]

[0167] In the formula, μ c (u i ) is u i The membership degree, u i Represents the i-th fuzzy control input (i.e., boost pressure difference, and boost pressure difference change rate); it should be noted that the centroid method is an existing defuzzification method, and the specific calculation method can refer to the relevant description in the prior art, which will not be described in detail here.

[0168] Since the intake system structure of the engine is complex and has the characteristics of nonlinearity, time-varying and large delay, it is difficult to control the boost pressure using conventional PID control. The embodiment of this specification adopts a fuzzy control strategy to achieve closed-loop control, which can imitate human control to a certain extent. It does not require an accurate control object model and can identify and model the knowledge and thinking, learning and reasoning, association and decision-making processes of relevant experts by computers, and control and achieve self-tuning, thereby further improving the control accuracy of the boost pressure.

[0169] In the above fuzzy control process, since the boost pressure is a parameter in the fuzzy control strategy, it has a certain flexibility. In actual application, the boost pressure can be set to a variable value to adapt to the requirements of the internal combustion engine for boost pressure under different working conditions.

[0170] The knowledge and thinking, learning and reasoning, association and decision-making processes of relevant experts can be identified and modeled by computers, and controlled to achieve self-tuning. This can further upgrade the intelligent control of boost pressure and compensate for the deviation between the actual boost pressure and the target boost pressure, which is conducive to achieving accurate control of the boost pressure. It can control the action of the boost actuator based on the actual boost pressure under various working conditions, thereby achieving the technical effect of the actual boost pressure quickly and stably following the target boost pressure.

[0171] Furthermore, in the process of boost closed-loop control, if the engine speed fluctuation range is within ±15rpm, and the target boost pressure ratio fluctuation range is within ±1kPa, and the time for both to be satisfied exceeds t0 (2s in this example). Only after the above conditions are met will the three update rules be used to update the boost pressure difference domain, the boost pressure difference change rate domain, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function. Note that the first update rule has a higher priority than the second update rule, and the second update rule has a higher priority than the third update rule. That is to say, if the first update rule is satisfied, the update of the second and third update rules will not be completed, and so on. Only when the first update rule is not satisfied, it is determined whether the second update rule is satisfied; if the first and second update rules are not satisfied, it is determined whether the third update rule is satisfied. If all three are not satisfied, no update is performed. When the update is satisfied, only the domain of boost pressure difference, domain of boost pressure difference change rate, relationship between boost pressure difference and first fuzzy quantity in the first membership function, and relationship between boost pressure difference change rate and second fuzzy quantity in the second membership function under the same working condition are updated. The working conditions are the same only when the engine speed is equal to the average engine speed that satisfies the update conditions and the target boost pressure ratio is equal to the average target boost pressure ratio that satisfies the conditions. The following three update rules have methods for calculating the average engine speed and the average target boost pressure ratio.

[0172] 1) If the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 10 kPa, and the boost pressure difference change rate dp Err The duration of maintaining no less than 20kPa / s exceeds the preset time t 1 (This example takes 0.5s), then get t 1 The target boost pressure ratio average value r BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0173] Then, the average engine speed n will be the same Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of the boost pressure difference under the working conditions, the domain of the boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset first update rule.

[0174] 2) If the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 2 kPa, and the boost pressure difference change rate dp ErrThe duration of maintaining no less than 8kPa / s exceeds the preset time t 2 (0.5s is taken in this embodiment), then t 2 The target boost pressure ratio average value r BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0175] Then the average engine speed will be the same as n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of the boost pressure difference under the working conditions, the domain of the boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset second update rule.

[0176] 3) If the boost pressure difference p Err The absolute value of the boost pressure difference is always kept less than 2kPa, and the boost pressure difference change rate dp Err If the pressure is always kept below 8 kPa / s, the average value of the target boost pressure ratio r within the duration is obtained. BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ;

[0177] Then the average engine speed will be the same as n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of boost pressure difference under the working condition, the domain of boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to the preset third update rule.

[0178] Furthermore, the first updating rule is as follows:

[0179] 1) Update the boost pressure difference domain to [-10, p ErrAvg ], the domain of the boost pressure difference change rate is updated to [-20, dp ErrAvg ];

[0180] 2) Update PB and NB in ​​the first membership function to,

[0181] PB=k1×PB(Z)+(1-k1)×p ErrAvg

[0182] NB=k1×NB(Z)+(1-k1)×pErrAvg

[0183] Wherein PB(Z) is the PB before updating, NB(Z) is the NB before updating, and k1 (0.2 in this embodiment) is a preset constant;

[0184] For example: the first time PB = 8, which means that when the boost pressure difference is higher than 8kPa, the module control rule belongs to positive big (PB). Assume that after the update PB = 9, which means that when the boost pressure difference is higher than 9kPa, the module control rule belongs to positive big (PB).

[0185] 3) Update PB and NB in ​​the second membership function to,

[0186] PB=k2×PB(Z)+(1-k2)×dp ErrAvg

[0187] NB=k2×NB(Z)+(1-k2)×dp ErrAvg

[0188] Wherein k2 (0.2 in this embodiment) is a preset constant;

[0189] For example: the first time PB = 15, which means that when the boost pressure difference is higher than 15kPa / s, the module control rule belongs to positive big (PB). Assume that after the update PB = 18, which means that when the boost pressure difference is higher than 18kPa / s, the module control rule belongs to positive big (PB).

[0190] Furthermore, the second update rule is as follows:

[0191] 1) Update NS and PS in the first membership function to,

[0192] NS=k3×NS(Z)+(1-k3)×p ErrAvg

[0193] PS=k3×PS(Z)+(1-k3)×p ErrAvg

[0194] Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k3 (0.3 in this embodiment) is a preset constant;

[0195] For example: PS = 2 for the first time, which means that when the boost pressure difference is higher than 2kPa, the module control rule belongs to positive small (PS). Assume that after the update, PS = 3, which means that when the boost pressure difference is higher than 3kPa, the module control rule belongs to positive small (PS);

[0196] 2) Update NS and PS in the second membership function to,

[0197] PS=k4×PS(Z)+(1-k4)×dp ErrAvg

[0198] NS=k4×NS(Z)+(1-k4)×dp ErrrAvg

[0199] Wherein, k4 (in this embodiment, 0.3) is a preset constant;

[0200] For example: PS=8 for the first time, which means that when the boost pressure difference is higher than 8kPa / s, the module control rule belongs to positive small (PS). Assume that after the update, PS=10, which means that when the boost pressure difference is higher than 10kPa / s, the module control rule belongs to positive small (PS).

[0201] Furthermore, the third updating rule is as follows:

[0202] 1) Update NS and PS in the first membership function to,

[0203] NS=k5×NS(Z)+(1-k5)×p ErrAvg

[0204] PS=k5×PS(Z)+(1-k5)×p ErrAvg

[0205] Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k5 (0.1 in this embodiment) is a preset constant;

[0206] For example: the first time PS = 2, which means that when the boost pressure difference is higher than 2kPa, the module control rule belongs to positive small (PS). Assume that after the update, PS = 1, which means that when the boost pressure difference is higher than 1kPa, the module control rule belongs to positive small (PS)

[0207] 2) Update NS and PS in the second membership function to:

[0208] NS=k6×NS(Z)+(1-k6)×dp ErrAvg

[0209] PS=k6×PS(Z)+(1-k6)×dp ErrAvg

[0210] Wherein, k6 (taken as 0.1 in this embodiment) is a preset constant;

[0211] For example: PS=8 for the first time, which means that when the boost pressure difference is higher than 8kPa / s, the module control rule belongs to positive small (PS). Assume that after the update, PS=6, which means that when the boost pressure difference is higher than 6kPa / s, the module control rule belongs to positive small (PS).

[0212] In other cases, the domain of the boost pressure difference and the domain of the boost pressure difference change rate are not updated, the PB, NB, PS, and NS of the boost pressure difference are not updated, and the PB, NB, PS, and NS of the boost pressure difference change rate are not updated.

[0213] It should be noted that the concept of the target boost pressure ratio described above can be found in the prior art CN201910988050.8 "Exhaust gas turbine engine boost closed-loop adaptive system and control method".

[0214] Embodiment 2:

[0215] See also Figure 5 This embodiment discloses a fuzzy controller, which is used to execute the boost pressure control method described in Example 1.

[0216] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for controlling boost pressure of an exhaust gas turbocharger system, characterized in that: Obtaining a boost pressure difference and a rate of change of the boost pressure difference of the exhaust gas turbocharger system; the boost pressure difference is the difference between a target boost pressure and an actual boost pressure of the exhaust gas turbocharger system, and the rate of change of the boost pressure difference is the first-order derivative of the boost pressure difference with time; Performing fuzzy processing on the boost pressure difference and the rate of change of the boost pressure difference to obtain a first fuzzy value and a second fuzzy value respectively; Inputting the first fuzzy quantity and the second fuzzy quantity into a preset fuzzy rule table to obtain a fuzzy control quantity; Defuzzifying the fuzzy control quantity to obtain a fuzzy control target opening; the fuzzy control target opening is used to control the boost actuator of the exhaust gas turbocharger system; If the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 10 kPa, and the boost pressure difference change rate dp Err If the duration of maintaining no less than 20 kPa / s exceeds the preset time t1, the average value of the target boost pressure ratio r within t1 is obtained. BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ; Then the same average engine speed n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of boost pressure difference under the working condition, the domain of boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to a preset first updating rule; If the boost pressure difference p Err The absolute value of the boost pressure difference is kept at no less than 2 kPa, and the boost pressure difference change rate dp Err If the duration of maintaining no less than 8 kPa / s exceeds the preset time t2, the average value of the target boost pressure ratio r within t2 is obtained. BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ; Then the same average engine speed n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of boost pressure difference under the working condition, the domain of boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to a preset second updating rule; If the boost pressure difference p Err The absolute value of the boost pressure difference is always kept less than 2kPa, and the boost pressure difference change rate dp Err If the pressure is always kept below 8 kPa / s, the target boost pressure ratio average value r is obtained. BoostRatioAvg , average engine speed n Avg , average value of boost pressure difference p ErrAvg , average value of boost pressure difference change rate dp ErrAvg ; Then the average engine speed will be the same as n Avg 、The average value of target boost pressure ratio r BoostRatioAvg The domain of boost pressure difference under the working condition, the domain of boost pressure difference change rate, the relationship between the boost pressure difference and the first fuzzy quantity in the first membership function, and the relationship between the boost pressure difference change rate and the second fuzzy quantity in the second membership function are updated according to a preset third updating rule; The first update rule is as follows: Update the boost pressure difference domain to [-10, p ErrAvg ], the domain of the boost pressure difference change rate is updated to [-20, dp ErrAvg ]; Update PB and NB in ​​the first membership function to, PB=k1×PB(Z)+(1-k1)×p ErrAvg NB=k1×NB(Z)+(1-k1)×p ErrAvg Where PB(Z) is the PB before updating, NB(Z) is the NB before updating, and k1 is a preset constant; Update PB and NB in ​​the second membership function to, PB=k2×PB(Z)+(1-k2)×dp ErrAvg NB=k2×NB(Z)+(1-k2)×dp ErrAvg Where k2 is a preset constant; The second update rule is as follows, Update NS and PS in the first membership function to, NS=k3×NS(Z)+(1-k3)×p ErrAvg PS=k3×PS(Z)+(1-k3)×p ErrAvg Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k3 is a preset constant; Update NS and PS in the second membership function to, PS=k4×PS(Z)+(1-k4)×dp ErrAvg NS=k4×NS(Z)+(1-k4)×dp ErrrAvg Among them, k4 is a preset constant; The third update rule is as follows, Update NS and PS in the first membership function to: NS=k5×NS(Z)+(1-k5)×p ErrAvg PS=k5×PS(Z)+(1-k5)×p ErrAvg Wherein, NS(Z) is the NS before updating, PS(Z) is the PS before updating, and k5 is a preset constant; Update NS and PS in the second membership function to: NS=k6×NS(Z)+(1-k6)×dp ErrAvg PS=k6×PS(Z)+(1-k6)×dp ErrAvg Among them, k6 is a preset constant.

2. The boost pressure control method of the exhaust gas turbocharger system according to claim 1, characterized in that: The process of fuzzifying the boost pressure difference to obtain the first fuzzy quantity is as follows; The domain of boost pressure difference is set to [-A, A], the unit is kPa, and A is a preset value; the first fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB, which represent five fuzzy ranges: negative large, negative small, zero, positive small, and positive large, respectively; Determining the corresponding relationship between the boost pressure difference and the first fuzzy quantity and establishing a first membership function; The process of fuzzy processing the boost pressure difference change rate to obtain the second fuzzy quantity is as follows; The domain of the boost pressure difference change rate is set to [-B, B], the unit is kPa / s, and B is a preset value; the second fuzzy quantity is divided into five fuzzy sets: NB, NS, ZO, PS, and PB, which represent negative large, negative small, zero, positive small, and positive large, respectively; The corresponding relationship between the boost pressure difference change rate and the second fuzzy quantity is determined and a second membership function is established.

3. The boost pressure control method of the exhaust gas turbocharger system according to claim 1, characterized in that: The corresponding relationship between the first fuzzy quantity, the second fuzzy quantity and the fuzzy control quantity in the preset fuzzy rule table is as follows; When the first fuzzy amount is NB and the second fuzzy amount is NB, the fuzzy control amount is NB; When the first fuzzy amount is NB and the second fuzzy amount is NS, the fuzzy control amount is NB; When the first fuzzy amount is NB and the second fuzzy amount is ZO, the fuzzy control amount is NB; When the first fuzzy amount is NB and the second fuzzy amount is PS, the fuzzy control amount is NM; When the first fuzzy amount is NB and the second fuzzy amount is PB, the fuzzy control amount is NS; When the first fuzzy amount is NS and the second fuzzy amount is NB, the fuzzy control amount is NB; When the first fuzzy amount is NS and the second fuzzy amount is NS, the fuzzy control amount is NM; When the first fuzzy amount is NS and the second fuzzy amount is ZO, the fuzzy control amount is NS; When the first fuzzy value is NS and the second fuzzy value is PS, the fuzzy control value is ZO; When the first fuzzy quantity is NS and the second fuzzy quantity is PB, the fuzzy control quantity is PS; When the first fuzzy amount is ZO and the second fuzzy amount is NB, the fuzzy control amount is NB; When the first fuzzy amount is ZO and the second fuzzy amount is NS, the fuzzy control amount is NS; When the first fuzzy amount is ZO and the second fuzzy amount is ZO, the fuzzy control amount is ZO; When the first fuzzy amount is ZO and the second fuzzy amount is PS, the fuzzy control amount is PS; When the first fuzzy quantity is ZO and the second fuzzy quantity is PB, the fuzzy control quantity is PM; When the first fuzzy amount is PS and the second fuzzy amount is NB, the fuzzy control amount is ZO; When the first fuzzy amount is PS and the second fuzzy amount is NS, the fuzzy control amount is PS; When the first fuzzy amount is PS and the second fuzzy amount is ZO, the fuzzy control amount is PM; When the first fuzzy quantity is PS and the second fuzzy quantity is PS, the fuzzy control quantity is PM; When the first fuzzy quantity is PS and the second fuzzy quantity is PB, the fuzzy control quantity is PB; When the first fuzzy amount is PB and the second fuzzy amount is NB, the fuzzy control amount is NS; When the first fuzzy quantity is PB and the second fuzzy quantity is NS, the fuzzy control quantity is PS; When the first fuzzy quantity is PB and the second fuzzy quantity is ZO, the fuzzy control quantity is PM; When the first fuzzy quantity is PB and the second fuzzy quantity is PS, the fuzzy control quantity is PM; When the first fuzzy quantity is PB and the second fuzzy quantity is PB, the fuzzy control quantity is PB; Among them, NB, NM, NS, ZO, PS, PM, and PB represent large negative, medium negative, small negative, zero, small positive, medium positive, and large positive, respectively.

4. The boost pressure control method of the exhaust gas turbocharger system according to claim 1, characterized in that: The defuzzification method adopts the centroid method.

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