Self-adaptive control method for variable altitude supercharging pressure of two-stage adjustable supercharged diesel engine

Abstract

A two-stage adjustable supercharged diesel engine variable altitude supercharged pressure adaptive adjustment control method, diesel engine ECU combines real-time monitoring of the position of the accelerator pedal, diesel engine speed, altitude query variable altitude diesel engine torque MAP, obtains the expected torque of the current working condition; the expected torque is used to query the torque and intake flow corresponding curve to obtain the expected intake amount of the two-stage supercharging system; according to the expected intake amount, the high and low pressure stage supercharger pressure characteristic MAP diagram is queried to obtain the total pressure of the two-stage supercharging system, the NMPC supercharging pressure controller calculates the high and low pressure stage bypass valve opening degree according to the difference between the expected pressure and the actual pressure, and the diesel engine ECU controls the change of the blade opening degree, so that the actual supercharging pressure is equal to the expected supercharging pressure. By using the method, the two-stage adjustable supercharged diesel engine supercharging pressure variable altitude adaptation can be realized, the high altitude transient response characteristic and acceleration characteristic of the diesel engine are improved, and the influence of altitude rise on the power and economy of the diesel engine is effectively relieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engine control, in particular to a variable-altitude boost pressure self-adaptive regulation control method for a two-stage adjustable supercharged diesel engine. BACKGROUND

[0002] China is a highland country with the largest highland area in the world. The Qinghai-Tibet Plateau is the most representative highland in the world, with an average altitude of more than 4000m and a total area of 2.4 million km2, accounting for about 1 / 4 of the land area. When vehicles drive on highland roads (such as the Qinghai-Tibet Line, Sichuan-Tibet Line and Yunnan-Tibet Line), the intake mass of the diesel engine decreases, leading to deterioration of diesel engine combustion, and obvious degradation of technical performances such as power, fuel consumption rate and thermal load. According to statistics, the power of the diesel engine decreases by 4.0% to 13.0% and the economy decreases by 2.7% to 12.9% for every 1000m increase in altitude, and the pre-vortex exhaust temperature and cylinder head temperature increase by 7% to 10%. The current diesel engine supercharging system has the defect that it cannot automatically adjust the supercharging pressure according to the change in altitude. SUMMARY

[0003] In view of the defect that the current diesel engine supercharging system cannot automatically adjust the supercharging pressure according to the change in altitude, the present application provides a variable-altitude boost pressure self-adaptive regulation control method for a two-stage adjustable supercharged diesel engine. The method can realize variable-altitude self-adaptation of the supercharging pressure of the two-stage adjustable supercharged diesel engine, improve the high-altitude transient response characteristics and acceleration characteristics of the diesel engine, and effectively alleviate the impact of altitude increase on the power and economy of the diesel engine.

[0004] According to the above concept, the technical scheme of the present application is: a variable-altitude boost pressure self-adaptive regulation control method for a two-stage adjustable supercharged diesel engine, characterized by comprising the following steps:

[0005] ①storing a gas pressure-altitude relationship table, a variable-altitude diesel engine torque MAP, a torque-intake flow relationship curve, a high-pressure stage supercharger pressure characteristic MAP graph and a low-pressure stage supercharger pressure characteristic MAP graph in the diesel engine ECU;

[0006] ②acquiring a change signal of the position of the accelerator pedal by the diesel engine ECU in real time;

[0007] ③when detecting the change in the position of the accelerator pedal, acquiring the current atmospheric pressure and the diesel engine speed by the diesel engine ECU, converting the current atmospheric pressure into altitude by querying the gas pressure-altitude relationship table, and obtaining the expected torque of the current operating condition based on the position of the accelerator pedal, the altitude and the speed by querying the variable-altitude diesel engine torque MAP;

[0008] ④obtaining the expected intake amount of the two-stage supercharging system by querying the torque-intake flow relationship curve based on the expected torque by the diesel engine ECU;

[0009] ⑤ The diesel engine ECU queries the high-pressure stage turbocharger compression characteristic MAP diagram and the low-pressure stage turbocharger compression characteristic MAP diagram based on the expected intake air volume of the two-stage turbocharger system, and obtains the expected boost pressure of the high-pressure stage turbocharger and low-pressure stage turbocharger two-stage turbocharger system;

[0010] ⑥ The NMPC boost pressure controller obtains the current actual pressure of the high and low pressure stage turbochargers, calculates the opening adjustment of the high and low pressure stage bypass valves based on the current boost pressure of the high and low pressure stage turbochargers and the expected boost pressure of the high and low pressure stage turbochargers, and sends the opening adjustment of the high and low pressure stage bypass valves to the diesel engine ECU.

[0011] ⑦ The diesel engine ECU controls the opening of the high and low pressure bypass valves to make the actual boost pressure equal to the desired boost pressure.

[0012] Furthermore, the change in the accelerator pedal position can be a change in the accelerator opening or a change in the pedal tilt.

[0013] Furthermore, the table relating air pressure and altitude is provided in the national standard GB / T20969.1-2007.

[0014] Furthermore, the variable altitude diesel engine torque MAP is obtained by conducting variable altitude performance tests on a diesel engine high-altitude performance test bench, resulting in a three-dimensional MAP of the diesel engine's altitude, torque, and throttle pedal under different operating conditions.

[0015] Furthermore, the torque-intake flow rate relationship curve is obtained based on the diesel engine variable altitude performance test conducted on a diesel engine high-altitude performance test bench.

[0016] Furthermore, the NMPC booster pressure controller is a booster pressure controller that employs a nonlinear model predictive control method.

[0017] Furthermore, the NMPC booster pressure controller uses the standard particle swarm optimization algorithm to solve for the optimal performance function and obtain the optimal control sequence of the bypass valve at time k:

[0018] minJ=ρ p Σ[p s (k+j)-p(k+j)] 2 +ρ U Σ[u(k+j-1)-u(k+j-2)] 2

[0019] subject to

[0020] u Hmin (k+j) H (k+j) Hmax (k+j), j=0,1,2,…N u -1 ​​

[0021] u Lmin (k+j) L (k+j) Lmax (k+j), j=0,1,2,…N u -1

[0022] Δu min ≤u(k+j-1)-u(k+j-2)≤Δu max

[0023] Where, ρ p ρ is the pressure error weight. U To control the incremental weights, k represents the current time, and N... u To control the time domain length, u is the control variable for the opening degree of the high and low pressure stage bypass valves, and P s Let p be the desired boost pressure, and p be the boost pressure predicted by the predictive model of the diesel engine boost system.

[0024] u Hmax u is the maximum opening of the high-pressure bypass valve. Hmin For the minimum opening of the high-pressure stage bypass valve, u Lmax For the maximum opening of the low-pressure stage bypass valve, u Lmin Δu is the minimum opening degree of the low-pressure stage bypass valve. max Δu is the upper limit of a single adjustment. min This is the lower limit of a single adjustment.

[0025] Furthermore, the predictive model for the diesel engine turbocharging system is established using a BP neural network. Its inputs include throttle opening, altitude, high-pressure stage bypass valve opening, and low-pressure stage bypass valve opening, while its output includes boost pressure.

[0026] Since changes in accelerator pedal position imply changes in throttle opening, affecting the final fuel injection quantity of the diesel engine, and these changes represent the driver's driving intentions, adjusting the turbocharger system based on these intentions helps establish a rapid and timely dynamic response relationship between the driver and the diesel engine, improving the transient response characteristics of the diesel engine under high-altitude conditions. Therefore, this invention uses the diesel engine ECU to acquire altitude and accelerator pedal position in real time, calculates the desired boost pressure, and coordinates the opening of the high- and low-pressure stage bypass valves to ensure that the actual boost pressure of the diesel engine equals the desired boost pressure. This satisfies the intake air requirements of the diesel engine at different altitudes, minimizing the impact of altitude on the engine's power and fuel economy. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a two-stage adjustable turbocharged diesel engine provided by the present invention;

[0028] Figure 2 This is a control flowchart of the present invention;​​

[0029] Figure 3 Control principle diagram of NMPC booster pressure controller;

[0030] Figure 4 The topology diagram of the neural network prediction model for a two-stage turbocharging system of a diesel engine;

[0031] Figure 5 The control flowchart for the NMPC booster pressure controller.

[0032] In the diagram: 1-Diesel engine; 2-Speed ​​sensor; 3, 7-Intercooler; 4-High-pressure stage turbocharger outlet pressure sensor; 5-High-pressure stage turbocharger inlet pressure sensor; 6, 10-Compressor; 8-Low-pressure stage turbocharger outlet pressure sensor; 9-Atmospheric pressure sensor; 11, 14-Turbine bypass valve opening sensor; 12, 15-Turbine bypass valve; 13, 16-Turbine. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, the present invention provides a method for adjusting and controlling a variable altitude adaptive boost pressure system for a two-stage adjustable turbocharged diesel engine. The adaptive system includes a diesel engine controller (ECU), a speed sensor, a throttle pedal sensor, a high-pressure stage VGT turbocharger, a low-pressure stage VGT turbocharger, a high-pressure stage turbocharger outlet pressure sensor, a high-pressure stage turbocharger inlet pressure sensor, a low-pressure stage turbocharger outlet pressure sensor, an atmospheric pressure sensor, and an NMPC boost pressure controller.

[0035] like Figure 2 As shown, the control flow of the booster pressure adaptive system includes steps S1, S2, S3, S4, S5, and S6. Each step will be described in detail below.

[0036] In step S1, the diesel engine controller (ECU) monitors the changes in the accelerator pedal position in real time. The changes in the accelerator pedal position can be changes in the accelerator opening or changes in the pedal tilt.

[0037] In step S2, when a change in accelerator pedal position is detected, the ECU obtains the current atmospheric pressure and diesel engine speed, queries the pressure-altitude relationship table, converts the current atmospheric pressure into altitude, and queries the diesel engine variable altitude torque MAP based on the accelerator pedal position, altitude, and speed to obtain the expected torque for the current operating condition. The pressure-altitude relationship table is referenced in national standard GB / T20969.1-2007. The variable altitude diesel engine torque MAP is obtained by conducting variable altitude performance tests on a diesel engine high-altitude performance test bench to obtain a three-dimensional MAP of the diesel engine's altitude, torque, and accelerator pedal position under different operating conditions.

[0038] In step S3, the diesel engine controller ECU obtains the secondary supercharging system expected intake air amount based on the torque versus intake air flow rate curve. The torque versus intake air flow rate curve is obtained based on a diesel engine high altitude performance test bench and diesel engine variable altitude performance test.

[0039] In step S4, the diesel engine controller ECU obtains the high and low pressure stage supercharger expected supercharging pressure based on the high and low pressure stage supercharger pressure characteristics MAP and the high and low pressure stage supercharger pressure ratio according to actual needs selected from 6:4, 5:5 and 4:6. The high and low pressure stage supercharger pressure characteristics MAP is provided by the supercharger manufacturer.

[0040] In step S5, the NMPC supercharging pressure controller obtains the current high and low pressure stage supercharging pressure, calculates the high and low pressure stage bypass valve opening degree adjustment amount based on the current high and low pressure stage supercharger supercharging pressure and the expected high and low pressure stage supercharger supercharging pressure, and sends the high and low pressure stage bypass valve opening degree adjustment amount to the ECU. The NMPC supercharging pressure controller is a supercharging pressure controller using a nonlinear model predictive control method, and the control is realized by solving the supercharging system optimal performance function in a rolling manner.

[0041] In step S6, the ECU acts the high and low pressure stage bypass valve opening degree adjustment amount on the high and low pressure stage turbine bypass valve, the NMPC supercharging pressure controller obtains the high and low pressure stage supercharging pressure after the action, and solves the control amount in the next time domain in a rolling optimization cycle in combination with the expected supercharging pressure.

[0042] In step S1, when the accelerator pedal sensor does not detect the accelerator pedal position change, the NMPC supercharging pressure controller and the diesel engine controller ECU control the high and low pressure stage bypass valve opening degree to remain unchanged.

[0043] As shown in FIG. 1, the NMPC supercharging pressure controller obtains the optimal control sequence of the bypass valve at time k by solving the optimal performance function using the standard particle swarm algorithm: Figure 3

[0044] minJ = p p Σ[p s (k+j)-p(k+j)] 2 + p U Σ[u(k+j-1)-u(k+j-2)] 2

[0045] j = 0, 1, 2, … N u -1

[0046] wherein p p is the pressure error weight, p U ​For the control of the incremental weight, k is the current time, N u For the control of the time domain length, u is the high and low pressure stage bypass valve opening control quantity, P s For the desired boost pressure, p is the diesel engine supercharging system neural prediction model boost pressure prediction value.

[0047] In actual control, considering the system stability and execution dynamic response, prevent the regulation quantity too large and valve opening exceeding the actual limit value, the optimization solving process should meet the following restrictions:

[0048] u Hmin (k+j)<u H (k+j)<u Hmax (k+j),j=0,1,2,…N u -1

[0049] u Lmin (k+j)<u L (k+j)<u Lmax (k+j),j=0,1,2,…N u -1

[0050] Δu min ≤u(k+j-1)-u(k+j-2)≤Δu max

[0051] Where u Hmax is the maximum opening of the high pressure stage bypass valve, u Hmin is the minimum opening of the high pressure stage bypass valve, u Lmax is the maximum opening of the low pressure stage bypass valve, u Lmin is the minimum opening of the low pressure stage bypass valve, Δu max is the upper limit of single regulation quantity, Δu min is the lower limit of single regulation quantity.

[0052] The optimization solution of the optimal performance function is based on the diesel engine supercharging system model, the diesel engine two-stage supercharging system has the characteristics of nonlinearity and strong coupling, the traditional average value simulation is difficult to accurately simulate the dynamic characteristics of the supercharging system, therefore, the BP neural network is used to establish the diesel engine two-stage supercharging system performance prediction model, which can be described as:

[0053] y=f bp (u)

[0054] Where y is the neural network response output, u is the simulation control quantity.

[0055] Figure 4 The topology diagram of the diesel engine two-stage supercharging system neural network prediction model, the input includes throttle opening, altitude, high pressure stage bypass valve opening, low pressure stage bypass valve opening; the output includes boost pressure.

[0056] Figure 5 The control flow chart of the NMPC supercharging pressure controller for the nonlinear model predictive control is solved by using the standard particle swarm algorithm to solve the optimal performance function. After the particle swarm algorithm solves the optimal control sequence of the bypass valve at the k time, the NMPC supercharging pressure controller sends the first value of the control sequence to the ECU, and the ECU applies the control quantity to the bypass valve, thus the diesel engine NMPC supercharging pressure controller completes the control at the k time. At the k+1 time, the controller obtains the high and low pressure stage supercharging pressures after the regulating quantity is applied, and combines the expected supercharging pressure obtained at the k+1 time to perform the supercharging pressure control at the k+1 time.

[0057] The present application can realize the self-adaptive change of the diesel engine variable-altitude supercharging pressure, meet the intake air demand of the diesel engine at different altitudes under different working conditions, maintain the air-fuel ratio in the normal range, and relieve the influence of the altitude rise on the power and economy of the diesel engine to the maximum extent.

[0058] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for adaptive control of turbocharged pressure at variable altitudes for a two-stage turbocharged diesel engine, characterized by: The method comprises the following steps: ①storing an air pressure and altitude relationship table, a variable altitude diesel engine torque MAP, a torque and intake flow relationship curve, a high pressure stage supercharger pressure characteristic MAP, and a low pressure stage supercharger pressure characteristic MAP in a diesel engine ECU; ②the diesel engine ECU acquires a throttle pedal position change signal in real time; ③when the throttle pedal position change is detected, the diesel engine ECU acquires the current atmospheric pressure and the diesel engine speed, queries the air pressure and altitude relationship table, converts the current atmospheric pressure into altitude, and queries the variable altitude diesel engine torque MAP based on the throttle pedal position, the altitude, and the speed to obtain the expected torque of the current working condition; ④the diesel engine ECU queries the torque and intake flow relationship curve based on the expected torque to obtain the expected intake amount of the two-stage supercharging system; ⑤the diesel engine ECU queries the high pressure stage supercharger pressure characteristic MAP and the low pressure stage supercharger pressure characteristic MAP according to the expected intake amount of the two-stage supercharging system to obtain the expected supercharging pressure of the high and low pressure stage superchargers of the two-stage supercharging system; ⑥the NMPC supercharging pressure controller acquires the current actual pressure of the high and low pressure stage superchargers, calculates the high and low pressure stage bypass valve opening degree adjustment amount based on the current high and low pressure stage supercharging pressure and the expected supercharging pressure of the high and low pressure stage superchargers, and sends the high and low pressure stage bypass valve opening degree adjustment amount to the diesel engine ECU; ⑦the diesel engine ECU controls the high and low pressure stage bypass valve opening degree to make the actual supercharging pressure equal to the expected supercharging pressure.

2. The method of adaptive control of variable altitude supercharging pressure of a two-stage adjustable supercharged diesel engine according to claim 1, characterized in that: The throttle pedal position change can be a throttle opening degree change or a pedal inclination change.

3. The method of adaptive control of variable altitude supercharging pressure of a two-stage adjustable supercharged diesel engine according to claim 1, characterized in that: The air pressure and altitude relationship table refers to the national standard GB / T20969.1-2007.

4. The method of adaptive control of variable supercharging pressure at variable altitudes for a two-stage supercharged diesel engine with adjustable supercharger according to claim 1, characterized in that: The variable altitude diesel engine torque MAP is obtained through diesel engine variable altitude performance test based on a diesel engine high altitude performance test bench.

5. The method of adaptive adjustment control of variable supercharging pressure at variable altitudes for a two-stage adjustable supercharged diesel engine according to claim 1, characterized in that: The torque and intake flow relationship curve is obtained through diesel engine variable altitude performance test based on a diesel engine high altitude performance test bench.

6. The method of adaptive adjustment control of variable supercharging pressure at variable altitudes for a two-stage adjustable supercharged diesel engine according to claim 1, characterized in that: The NMPC supercharging pressure controller is a supercharging pressure controller adopting a nonlinear model predictive control method.

7. The method of adaptive control of variable altitude supercharging pressure of a two-stage adjustable supercharged diesel engine according to claim 1 or 6, characterized in that: The NMPC supercharging pressure controller adopts a standard particle swarm algorithm to solve an optimal performance function to obtain an optimal control sequence of the bypass valve at the k moment: minJ = p p ∑[p s (k+j)-p(k+j)] 2 + p U ∑[u(k+j-1)-u(k+j-2)] 2 subject to u Hmin (k+j)<u H (k+j)<u Hmax (k+j),j=0,1,2,…N u -1 u Lmin (k+j)<u L (k+j)<u Lmax (k+j),j=0,1,2,…N u -1 Δu min ≤ u(k + j - 1) - u(k + j - 2) ≤ Δu max wherein, p p is a pressure error weight, p U is a control increment weight, k is the current time, N u is a control time domain length, u is a high and low pressure stage bypass valve opening control quantity, P s is a desired boost pressure, p is a turbocharged diesel engine boost system prediction model boost pressure prediction value; u Hmax is the maximum opening of the high-pressure stage bypass valve, u Hmin is the minimum opening of the high-pressure stage bypass valve, u Lmax is the maximum opening of the low-pressure stage bypass valve, u Lmin is the minimum opening of the low-pressure stage bypass valve, Δu max is the upper limit of the single adjustment amount, Δu min is the lower limit of the single adjustment amount.

8. The method of adaptive control of variable supercharging pressure at variable altitudes for a two-stage adjustable supercharged diesel engine according to claim 7, characterized in that: The diesel engine supercharging system prediction model adopts a BP neural network to establish, and the input includes the throttle opening degree, the altitude, the high pressure stage bypass valve opening degree, and the low pressure stage bypass valve opening degree, and the output includes the supercharging pressure.

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