A control method for a VGT

Abstract

The application relates to the technical field of automobile control, and provides a control method of a VGT, the control method comprising the following steps: determining a pre-control control item opening degree and a gain factor of PID control according to an engine speed and a target supercharging pressure; determining PID basic parameters according to the engine speed, the target supercharging pressure and an actual supercharging pressure; determining a feedback control item opening degree according to the PID basic parameters and the gain factor; and determining an initial target opening degree according to the pre-control control item opening degree and the feedback control item opening degree. The control method of the VGT provided by the embodiment of the application can improve the supercharging pressure control precision of the VGT. The actual supercharging pressure of the VGT in different supercharging regions can be ensured to be quickly adjusted and stably adjusted towards the target supercharging pressure, and the problems of slow or fast supercharging pressure adjustment of the VGT in different supercharging regions due to large differences in turbine MAP characteristics can be avoided.

Description

Technical Field

[0001] This application relates to the field of automotive control technology, and in particular to a control method for a VGT. Background Technology

[0002] With the rapid development of the automotive and internal combustion engine industries, turbocharging and miniaturization are the main development trends of current internal combustion gasoline engines. By installing a turbocharger, a larger intake volume can be provided to the engine, increasing engine power. Among related technologies, compared to the already mass-produced WGT (Waste Gate Turbocharger), VGT (Variable Geometry Turbocharger) can adjust the turbine's flow cross-section according to engine needs. It can provide higher efficiency in both low-speed, low-flow and high-speed, high-flow conditions, as well as in low-speed, high-torque and high-speed, high-power conditions. Moreover, to achieve the same intake pressure, VGT has less loss and lower turbine inlet pressure, further reducing engine pumping losses.

[0003] However, the turbine MAP (map) characteristics of VGT are different from those of WGT. Because VGT adjusts the nozzle ring angle through variable cross section technology to obtain different turbine MAPs, and the different turbine MAP characteristics are quite different, the same amount of boost pressure change will result in a large difference in the turbocharger opening requirement in different boost pressure ranges. If WGT's control technology is used, the problem of boost pressure adjustment being too slow or too fast will occur. Summary of the Invention

[0004] In view of this, embodiments of this application provide a VGT control method that can avoid the problem of VGT boost pressure adjustment being too slow or too fast.

[0005] To achieve the above objectives, the technical solution of this application embodiment is implemented as follows:

[0006] This application provides a VGT control method, the control method comprising:

[0007] The opening degree of the pre-control term and the gain factor of the PID control are determined based on the engine speed and the target boost pressure.

[0008] The PID basic parameters are determined based on the engine speed, the target boost pressure, and the actual boost pressure.

[0009] The opening degree of the feedback control term is determined based on the PID basic parameters and the gain factor.

[0010] The initial target opening is determined based on the opening degree of the pre-control item and the opening degree of the feedback control item.

[0011] In some implementation schemes, the opening degree of the pre-control item is determined based on engine speed and target boost pressure, including:

[0012] Query the first relation table, wherein the first relation table includes at least one set of correspondences between calibrated engine speed, calibrated boost pressure and calibrated booster opening;

[0013] When the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, the corresponding calibrated booster opening is determined as the pre-control item opening.

[0014] In some implementations, a bench calibration test is performed on the VGT to obtain at least one set of correspondences between the calibrated engine speed, the calibrated boost pressure, and the calibrated booster opening, and the correspondences of the three are added to the first relationship table.

[0015] In some implementations, the gain factor of the PID control is determined based on engine speed and target boost pressure, including:

[0016] Query the second relation table, wherein the second relation table includes at least one set of correspondences between calibrated engine speed, calibrated boost pressure and calibrated gain factor;

[0017] When the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, the corresponding calibration gain factor is determined as the gain factor.

[0018] In some implementations, a bench calibration test is performed on the VGT, and the calibration gain factor is determined based on the correspondence between the change in the calibration turbocharger opening and the change in the calibration boost pressure. At least one set of correspondences between the calibration engine speed, the calibration boost pressure and the calibration gain factor is obtained, and the correspondences of the three are added to the second relationship table.

[0019] In some implementation schemes, the opening degree of the feedback control term is determined based on the PID basic parameters and the gain factor; wherein, the PID basic parameters include P term, I term and D term; the gain factor includes Kp term, Ki term and Kd term; and the opening degree of the feedback control term is Kp term × P term + Ki term × I term + Kd term × D term.

[0020] In some implementation schemes, an initial target opening is determined based on the opening degree of the pre-control item and the opening degree of the feedback control item; wherein, the initial target opening degree is the sum of the opening degree of the pre-control item and the opening degree of the feedback control item.

[0021] In some implementations, the opening limit of the VGT and the initial target opening are determined as the final target opening.

[0022] In some implementations, the opening limit is determined based on the engine speed and engine load.

[0023] In some implementations, a third relation table is queried, wherein the third relation table includes at least one set of correspondences between the inflection point opening of the calibrated engine speed, calibrated engine load, and calibrated boost pressure;

[0024] When the engine speed is the same as the calibrated engine speed and the engine load is the same as the calibrated engine load, the corresponding inflection point opening is determined as the opening limit value.

[0025] In some implementations, a bench calibration test is performed on the VGT, keeping the calibration engine speed and the calibration engine load constant, and gradually increasing the turbocharger opening to determine the inflection point opening under the calibration engine speed and the calibration engine load conditions;

[0026] Obtain at least one set of correspondences between the calibrated engine speed, the calibrated engine load, and the inflection point opening, and add the correspondences of the three to the third relationship table.

[0027] In some implementations, the initial target opening is determined as the final target opening, provided that the initial target opening is not greater than the opening limit.

[0028] In some implementations, the opening limit is determined to be the final target opening, provided that the initial target opening is greater than the opening limit.

[0029] In some implementations, the actual boost pressure is adjusted according to the final target opening to achieve closed-loop control.

[0030] This application provides a VGT control method that improves the boost pressure control accuracy of the VGT. A gain factor for adjusting the PID basic parameters is determined based on engine speed and target boost pressure. The gain factor is set with different parameter values ​​under different engine speeds and target boost pressures. This allows the VGT to have different feedback control term openings under different boost pressure regions after combining the gain factor with the PID control parameters. This ensures that the VGT has a high-precision feedback control term opening in different boost pressure regions. Finally, the pre-control term opening and the feedback control term opening are combined to determine the initial target opening of the VGT. This ensures that the actual boost pressure of the VGT adjusts rapidly and smoothly towards the target boost pressure in different boost pressure regions, improving the boost pressure control accuracy of the VGT and avoiding the problem of excessively slow or fast boost pressure adjustment due to large differences in turbine MAP characteristics in different boost pressure regions. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a VGT control method according to an embodiment of this application;

[0032] Figure 2 This is a graph showing the relationship between boost pressure and booster opening in VGT and WGT. Detailed Implementation

[0033] It should be noted that the various embodiments / implementations provided in this application can be combined with each other without creating contradictions. The detailed descriptions in the specific embodiments should be understood as explanations of the spirit of this application and should not be regarded as undue limitations on this application.

[0034] The following is in conjunction with the appendix Figure 1 The present application will be further described in detail below with reference to specific embodiments. The terms "first," "second," etc., used in the embodiments of this application are only used to distinguish different objects and are not used to describe a specific order, and should not be construed as indicating or implying their relative importance or implicitly including at least one feature. In the description of the embodiments of this application, the term "comprising" and any variations thereof are intended to cover non-exclusive protection.

[0035] In related technologies, the turbocharger opening of the WGT is controlled by a wastegate valve, which regulates the amount of exhaust gas passing through the WGT turbine. The wastegate valve is located on the side of the WGT turbine's intake passage. Part of the engine's exhaust gas enters the turbine, while the other part passes directly into the vehicle's exhaust pipe through the wastegate valve. Therefore, the WGT can adjust the amount of exhaust gas entering the turbine by controlling the opening of the wastegate valve. When the wastegate valve is fully open, the WGT's turbocharger opening is 100%; when the wastegate valve is fully closed, the WGT's turbocharger opening is 0%.

[0036] The turbocharger opening adjustment of a VGT differs from that of a WGT. A VGT is a variable geometry turbocharger; the turbocharger opening is adjusted by changing the angle of the guide vanes on the nozzle ring using variable geometry technology, thereby controlling the airflow entering the turbocharger. When the guide vanes are perpendicular to the airflow direction entering the turbine, the VGT's turbocharger opening is 100%; when the guide vanes are parallel to the airflow direction entering the turbine, the VGT's turbocharger opening is 0%.

[0037] Because the wastegate valve only changes the intake air volume into the WGT turbine and does not alter the turbine's MAP characteristics, the turbocharger opening of the WGT will change identically across all boost regions as long as the difference in boost pressure is the same. However, in the VGT, adjusting the turbocharger opening by changing the angle of the guide vanes on the nozzle ring will alter the VGT's turbine MAP characteristics, resulting in significant differences in turbine MAP characteristics across different boost regions.

[0038] For example, in one embodiment, under the condition of engine speed of 2000 r / min, within the boost pressure range of increasing VGT from 110 kPa to 120 kPa, the turbocharger opening needs to be adjusted from 20% to 30%, a change of 10%. Within the boost pressure range of increasing VGT from 200 kPa to 210 kPa, the turbocharger opening only needs to be adjusted from 70% to 72%, a change of 2%. That is to say, the same amount of boost pressure change requires a significantly different turbocharger opening in different boost pressure ranges.

[0039] Therefore, if the opening control method of WGT is directly applied to VGT, problems such as excessively slow or excessively fast boost pressure adjustment will occur.

[0040] To resolve the above issues, please refer to [link / reference]. Figure 1 This application provides a VGT control method, including the following steps:

[0041] S1. Determine the opening degree of the pre-control item and the gain factor of the PID control based on the engine speed and the target boost pressure;

[0042] S2. Determine the basic parameters of the PID controller based on the engine speed, target boost pressure and actual boost pressure.

[0043] S3. Determine the opening degree of the feedback control term based on the PID basic parameters and gain factor;

[0044] S4. Determine the initial target opening based on the opening of the pre-control item and the opening of the feedback control item.

[0045] Here, engine speed is the engine speed measured in real time during vehicle operation; target boost pressure is the target boost pressure determined based on the torque required by the driver; and actual boost pressure is the actual boost pressure measured in real time during the current vehicle operation. PID control refers to proportional-integral-derivative control. PID basic parameters are the fundamental parameters used to implement PID control. The initial target opening can be used to adjust the actual boost pressure to bring it closer to the target boost pressure.

[0046] The VGT control method described in this application improves the boost pressure control accuracy of the VGT. A gain factor is determined based on engine speed and target boost pressure to adjust the PID basic parameters. Different parameter values ​​are set for the gain factor under different engine speeds and target boost pressures. This allows the VGT to have different feedback control term openings under different boost pressure regions after combining the gain factor with the PID control parameters. This ensures that the VGT has a high-precision feedback control term opening in different boost pressure regions. Finally, the pre-control term opening and the feedback control term opening are combined to determine the initial target opening of the VGT. This ensures rapid and smooth adjustment of the actual boost pressure towards the target boost pressure in different boost pressure regions, improving the boost pressure control accuracy of the VGT and avoiding problems such as excessively slow or fast boost pressure adjustment due to significant differences in turbine MAP characteristics in different boost pressure regions.

[0047] The steps of a VGT control method provided in this application embodiment are described in detail below:

[0048] In one embodiment, step S1, determining the opening degree of the pre-control term and the gain factor of the PID control based on the engine speed and the target boost pressure, includes:

[0049] S11. Determine the opening degree of the pre-control item based on the engine speed and target boost pressure.

[0050] S12. Determine the gain factor of PID control based on engine speed and target boost pressure.

[0051] The order of S11 and S12 is not particularly restricted. S11 can be performed first and then S12, or S12 can be performed first and then S11, or S11 and S12 can be performed simultaneously.

[0052] In one embodiment, step S11, determining the opening degree of the pre-control item based on engine speed and target boost pressure, includes:

[0053] Query the first relationship table, which includes at least one set of correspondences between calibrated engine speed, calibrated boost pressure and calibrated turbocharger opening; when the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, determine the corresponding calibrated turbocharger opening as the pre-control item opening.

[0054] In other words, we can use a first relational table to store the correspondence between the calibrated engine speed, the calibrated boost pressure, and the calibrated turbocharger opening. If the engine speed measured in real time during vehicle operation is the same as the calibrated engine speed, and the target boost pressure determined based on the torque demanded by the driver is also the same as the calibrated boost pressure, then we can set the corresponding calibrated turbocharger opening as the VGT's pre-control item opening according to the first relational table.

[0055] In one embodiment, step S12, determining the gain factor of the PID control based on the engine speed and the target boost pressure, includes:

[0056] The second relationship table is queried, which includes at least one set of correspondences between the calibrated engine speed, the calibrated boost pressure, and the calibrated gain factor; when the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, the corresponding calibrated gain factor is determined as the gain factor.

[0057] In other words, we can use a second relational table to store the correspondence between the calibrated engine speed, the calibrated boost pressure, and the calibrated gain factor. If the engine speed measured in real time during vehicle operation is the same as the calibrated engine speed, and the target boost pressure determined based on the driver's required torque is also the same as the calibrated boost pressure, then we can set the corresponding calibrated gain factor as the gain factor of VGT according to the second relational table.

[0058] In one embodiment, step S2 involves determining the PID basic parameters based on engine speed, target boost pressure, and actual boost pressure. Specifically, at engine speeds measured in real-time during vehicle operation, PID control is applied to the actual difference between the target boost pressure and the actual boost pressure to obtain the PID basic parameters. Specifically, bench calibration tests can be performed on the VGT (Vehicle GT) to calculate and adjust the boost pressure response at various calibrated engine speeds, obtaining at least one set of correspondence tables between the calibrated engine speed, target boost pressure, and actual boost pressure, and the calibrated PID basic parameters. By querying the above correspondence table, if the engine speed measured in real-time during vehicle operation is the same as the calibrated engine speed, and the calibrated difference is also the same as the actual difference, the corresponding calibrated PID basic parameters are used as the PID basic parameters.

[0059] The order of S1 and S2 is not particularly restricted. S1 can be performed first and then S2, or S2 can be performed first and then S1, or S1 and S2 can be performed simultaneously.

[0060] In one embodiment, step S3 involves determining the feedback control term opening based on the PID basic parameters and the gain factor. The PID basic parameters include P, I, and D terms; the gain factor includes Kp, Ki, and Kd terms; and the feedback control term opening is calculated as Kp × P + Ki × I + Kd × D. In other words, the VGT's PID basic control parameters are adjusted based on three parameters: P, I, and D, which represent the strength of proportional, integral, and derivative control, respectively. Correspondingly, the gain factor also includes three parameters: Kp, Ki, and Kd, which represent the gain of proportional, integral, and derivative control, respectively. The Kp, Ki, and Kd terms of the gain factor can individually compensate for the P, I, and D terms of the PID basic control parameters. This results in the feedback control term opening as Kp × P + Ki × I + Kd × D. By adjusting any one of the three terms, Kp, Ki, and Kd, the magnitude of the feedback control term opening of VGT in PID control can be finely adjusted.

[0061] In one embodiment, step S4, determining the initial target opening based on the pre-control term opening and the feedback control term opening, specifically means that the initial target opening is the sum of the pre-control term opening and the feedback control term opening. That is, the initial target opening is the opening of the pre-control term after correction by the feedback control term opening. Since the feedback control term opening is a parameter compensated by the PID basic parameters and gain factor, adding the feedback control term opening to the pre-control term opening can further correct the initial target opening. This initial target opening can then be used to adjust the actual boost pressure, resulting in higher control accuracy of the initial target opening over the actual boost pressure.

[0062] The acquisition of the first relationship table includes, but is not limited to, bench calibration tests on the VGT. For example, in one embodiment, a bench calibration test is performed on the VGT to obtain at least one set of correspondences between calibrated engine speed, calibrated boost pressure, and calibrated turbocharger opening, and these correspondences are added to the first relationship table. Specifically, a bench calibration test is first prepared by installing the VGT in a laboratory or test bench and running it with the engine, and preparing sensors for measuring and recording the calibrated engine speed, calibrated boost pressure, and calibrated turbocharger opening. Then, the bench calibration test is performed by starting the engine and bringing it to a predetermined calibrated speed. Then, the boost pressure or turbocharger opening is controlled by adjusting the boost pressure or turbocharger opening to obtain the desired calibrated boost pressure and turbocharger opening. The above test is repeated, and the calibrated boost pressure and turbocharger opening measured by the sensors are recorded at multiple calibrated engine speeds. These data can be recorded and processed by computer, and then analyzed to determine at least one set of correspondences between calibrated engine speed, calibrated boost pressure, and calibrated turbocharger opening. These correspondences are then added to a first relationship table. Establishing this first relationship table facilitates the subsequent retrieval of pre-control item openings, shortens data acquisition time, and improves the control efficiency of the VGT.

[0063] The acquisition of the second relationship table includes, but is not limited to, bench calibration tests on the VGT. For example, in one embodiment, a bench calibration test is performed on the VGT, and the calibration gain factor is determined based on the correspondence between the change in the calibration turbocharger opening and the change in the calibration boost pressure. At least one set of correspondences between the calibration engine speed, calibration boost pressure, and calibration gain factor is acquired, and these correspondences are added to the second relationship table. Specifically, a bench calibration test is first prepared by installing the VGT in a laboratory or test bench and running it with the engine, and preparing sensors for measuring and recording the calibration engine speed and calibration boost pressure. Then, the bench calibration test is performed by starting the engine and bringing it to a predetermined calibration speed, gradually increasing the calibration turbocharger opening in certain increments, and observing and recording the change in the calibration boost pressure; or, gradually increasing the calibration turbocharger pressure in certain increments, and observing and recording the change in the calibration boost opening, to obtain the proportional correspondence between the change in the turbocharger opening and the change in the calibration boost pressure, and determining the magnitude of the gain factor through this proportional correspondence. Finally, these data are analyzed and processed to determine at least one set of correspondences between calibrated engine speed, calibrated boost pressure, and calibrated gain factor, and these correspondences are added to the second relationship table.

[0064] For example, in one embodiment, a bench calibration test is performed on the VGT. Under the condition of a calibrated engine speed of 2000 r / min, the change in calibrated boost pressure is 10 kPa within the boost pressure range from 110 kPa to 120 kPa; the calibrated turbocharger opening needs to be adjusted from 20% to 30%, and the change in calibrated turbocharger opening is 10%.

[0065] At this point, although the change in the calibrated boost pressure is 10 kPa, the change in the calibrated booster opening is 10%. Therefore, we can set a larger gain factor. A larger gain factor, combined with the PID basic parameters, will result in a larger feedback control term opening, thereby increasing the correction of the feedback control term opening to the pre-control term opening. Then, by adding the feedback control term opening to the pre-control term opening, we can further correct the initial target opening to avoid the problem of slow boost pressure adjustment.

[0066] In another embodiment, the VGT was also subjected to bench calibration tests. Under the condition of a calibrated engine speed of 2000 r / min, within the boost pressure range of increasing the calibrated boost pressure of the VGT from 200 kPa to 210 kPa, the change in calibrated boost pressure was 10 kPa; the calibrated turbocharger opening only needed to be adjusted from 70% to 72%, and the change in calibrated turbocharger opening was 2%.

[0067] At this point, although the change in the calibrated boost pressure is also 10 kPa, the change in the calibrated booster opening is only 2%. Therefore, we can set a smaller gain factor, and the smaller gain factor, combined with the PID basic parameters, will result in a smaller feedback control term opening, thereby reducing the correction amount of the feedback control term opening to the pre-control term opening. Then, by adding the feedback control term opening to the pre-control term opening, we can further correct the initial target opening to avoid the problem of excessively rapid boost pressure adjustment.

[0068] In related technologies, compared to WGT, the boost pressure in the turbine MAP characteristic of VGT is non-monotonic. For an example, please refer to... Figure 2 The turbine MAP characteristics of VGT in the middle are determined by Figure 2It can be seen that at a certain engine speed, as the turbocharger opening gradually increases from 0% to 100%, the boost pressure initially increases with the increase in turbocharger opening. When the turbocharger opening increases to a certain value, the boost pressure reaches its maximum value, point P. Subsequently, the boost pressure decreases rapidly as the turbocharger opening continues to increase. Therefore, the boost pressure of the VGT does not increase indefinitely with the increase in turbocharger opening, but rather has an inflection point with a maximum value. Since PID control itself also has monotonicity—that is, if the boost pressure is too high, the turbocharger opening is reduced; if the boost pressure is insufficient, the turbocharger opening is increased—based on the turbine MAP characteristic of the VGT, if the VGT's turbocharger opening overshoots to the point where the boost pressure exceeds the inflection point of the maximum value P, a problem will arise where the boost pressure cannot be corrected back.

[0069] To address the issue of boost pressure failing to recover after exceeding its maximum inflection point, in one embodiment, after determining the initial target opening based on the pre-control term opening and the feedback control term opening in step S4, the VGT control method further includes step S5, determining either the VGT opening limit or the initial target opening as the final target opening. Specifically, the opening limit refers to the maximum limit of the VGT's booster opening under certain conditions; the VGT's booster opening must not exceed this limit to avoid the problem of boost pressure failing to recover. In other words, the final target opening of the VGT needs to be selected from either the VGT opening limit or the initial target opening. The final target opening of the VGT is determined by comparing the opening limit and the initial target opening.

[0070] For example, in one embodiment, the initial target opening is determined as the final target opening if the initial target opening is not greater than the opening limit. That is, if the initial target opening is less than or equal to the opening limit, control is enabled, and the initial target opening is output as the final target opening of the VGT.

[0071] For example, in one embodiment, if the initial target opening is greater than the opening limit, the opening limit is determined as the final target opening. That is, if the initial target opening is greater than the opening limit, control is disabled, and the opening limit is output as the final target opening of VGT.

[0072] In one embodiment, determining the VGT opening limit based on engine speed and engine load includes:

[0073] The third relationship table is queried, which includes at least one correspondence between the inflection point openings of the calibrated engine speed, calibrated engine load, and calibrated boost pressure. When the engine speed and calibrated engine speed and load are the same, the corresponding inflection point opening is determined as the opening limit. The engine load is the engine load measured in real time during vehicle operation.

[0074] In other words, we can use a third relation table to store the correspondence between the calibrated engine speed, the calibrated boost pressure, and the inflection point opening of the calibrated boost pressure. If the engine speed measured in real time during vehicle operation is the same as the calibrated engine speed, and the engine load measured in real time during vehicle operation is also the same as the calibrated engine load, then we can set the corresponding inflection point opening of the calibrated boost pressure as the opening limit of VGT according to the third relation table.

[0075] The methods for obtaining the third relationship table include, but are not limited to, bench calibration tests on the VGT. For example, in one embodiment, a bench calibration test is performed on the VGT, keeping the calibrated engine speed and load constant while gradually increasing the turbocharger opening to determine the inflection point opening under the calibrated engine speed and load conditions; at least one set of correspondences between the calibrated engine speed, calibrated engine load, and inflection point opening is obtained, and these correspondences are added to the third relationship table.

[0076] Specifically, the process begins with bench calibration. The VGT is installed in a laboratory or test bench and operated alongside the engine. Sensors are prepared to measure and record the calibration engine speed, calibration engine load, and calibration turbocharger opening. The bench calibration test is then conducted by starting the engine and bringing it to the predetermined calibration engine speed and load. The turbocharger opening is then gradually increased, and the inflection point opening at the maximum boost pressure is observed and recorded. This test is repeated, recording multiple inflection point openings at the maximum boost pressure under different calibration engine speeds and loads. These data can be recorded and processed by computer. Finally, the data is analyzed to determine at least one correspondence between the calibration engine speed, calibration engine load, and inflection point opening, and this correspondence is added to a third relationship table. Establishing this third relationship table facilitates subsequent retrieval of opening limits, shortens data acquisition time, and improves the control efficiency of the VGT.

[0077] In one embodiment, the VGT control method further includes step S6: adjusting the actual boost pressure according to the final target opening to achieve closed-loop control. Specifically, during vehicle operation, the input signals of the VGT control method include engine speed, target boost pressure, actual boost pressure, and engine load. The output signals of the VGT control method include the pre-control item opening, feedback control item opening, initial target opening, opening limit, and final target opening. Within one control cycle, the input signal is first acquired by sampling, and then the output signal is obtained from the input signal. In the output signal, the pre-control item opening, feedback control item opening, initial target opening, and opening limit are intermediate values, while the final target opening is the final value. By outputting the final target opening, the actual boost pressure in the input signal can be changed. Then, the actual boost pressure adjusted by the final target opening is fed back to the input of the next control cycle to determine the final target opening of the next control cycle. This process is repeated according to the above control cycle to form a control closed loop, so that the actual boost pressure continuously approaches the target boost pressure, thereby achieving PID closed-loop control.

[0078] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method of a VGT, characterized by, The control method includes: The opening degree of the pre-control term is determined based on the engine speed and the target boost pressure, and the gain factor of the PID control is determined based on the engine speed and the target boost pressure. The PID basic parameters are determined based on the engine speed, the target boost pressure, and the actual boost pressure. The opening degree of the feedback control term is determined based on the PID basic parameters and the gain factor. The initial target opening is determined based on the opening degree of the pre-control item and the opening degree of the feedback control item.

2. The control method according to claim 1, characterized by, The opening degree of the pre-control item is determined based on engine speed and target boost pressure, including: Query the first relation table, wherein the first relation table includes at least one set of correspondences between calibrated engine speed, calibrated boost pressure and calibrated booster opening; When the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, the corresponding calibrated booster opening is determined as the pre-control item opening.

3. The control method according to claim 2, characterized by, A bench calibration test is performed on the VGT to obtain at least one set of correspondences between the calibrated engine speed, the calibrated boost pressure and the calibrated booster opening, and the correspondences of the three are added to the first relationship table.

4. The control method according to claim 1, characterized by, The gain factor of the PID control is determined based on engine speed and target boost pressure, including: Query the second relation table, wherein the second relation table includes at least one set of correspondences between calibrated engine speed, calibrated boost pressure and calibrated gain factor; When the engine speed is the same as the calibrated engine speed and the target boost pressure is the same as the calibrated boost pressure, the corresponding calibration gain factor is determined as the gain factor.

5. The control method according to claim 4, characterized by A bench calibration test is performed on the VGT. The calibration gain factor is determined based on the correspondence between the change in the calibration turbocharger opening and the change in the calibration boost pressure. At least one set of correspondences between the calibration engine speed, the calibration boost pressure and the calibration gain factor is obtained, and the correspondences of the three are added to the second relationship table.

6. The control method according to claim 1, characterized by, The opening degree of the feedback control term is determined based on the PID basic parameters and the gain factor; wherein, the PID basic parameters include P term, I term and D term; the gain factor includes Kp term, Ki term and Kd term; the opening degree of the feedback control term is Kp term × P term + Ki term × I term + Kd term × D term.

7. The control method according to claim 1, characterized by, The initial target opening is determined based on the opening degree of the pre-control item and the opening degree of the feedback control item; wherein the initial target opening degree is the sum of the opening degree of the pre-control item and the opening degree of the feedback control item.

8. The control method according to claim 1, characterized by, The final target opening is determined by either the opening limit of the VGT or the initial target opening.

9. The control method according to claim 8, characterized by, The opening limit is determined based on the engine speed and engine load.

10. The control method according to claim 9, characterized by, Query the third relation table, wherein the third relation table includes at least one set of correspondences between the inflection point opening of the calibrated engine speed, calibrated engine load, and calibrated boost pressure; When the engine speed is the same as the calibrated engine speed and the engine load is the same as the calibrated engine load, the corresponding inflection point opening is determined as the opening limit value.

11. The control method according to claim 10, characterized by, A bench calibration test was performed on the VGT. The rated engine speed and the rated engine load were kept constant, and the turbocharger opening was gradually increased to determine the inflection point opening under the rated engine speed and the rated engine load conditions. Obtain at least one set of correspondences between the calibrated engine speed, the calibrated engine load, and the inflection point opening, and add the correspondences of the three to the third relationship table.

12. The control method according to claim 8, characterized by, Under the condition that the initial target opening is not greater than the opening limit, the initial target opening is determined as the final target opening.

13. The control method according to claim 8, characterized by, If the initial target opening is greater than the opening limit, the opening limit is determined to be the final target opening.

14. The control method according to claim 8, characterized by, Adjust the actual boost pressure according to the final target opening to achieve closed-loop control.

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