Fault simulation method for monitoring response delay of VVT system

Abstract

The invention discloses a fault simulation method for monitoring response delay of a VVT system. The method comprises the following steps: S1, enabling a fault simulation function; s2, waiting for a proper condition, and responding to diagnosis sampling entering; s3, taking the current VVT actual position as a control demand position, and keeping the current VVT actual position unchanged; s4, waiting for completion of response diagnosis sampling; s5, calculating the actual position change rate of the VVT in the sampling process; s6, comparing the actual position change rate of the VVT with the diagnosis threshold value of slow response; and S6, judging a fault result, and determining whether a fault simulation function is enabled or not through selection of a function switch according to a use requirement. The fault simulation method for monitoring the response delay of the VVT system has the advantages that VVT control in a normal scene is not affected, the function is started only when the fault needs to be simulated, and the flexibility is high.

Description

Technical Field

[0001] The invention relates to the technical field of on-board diagnosis, and in particular to a fault simulation method for monitoring slow response of a VVT system. Background Art

[0002] Continuously Variable Valve Timing (VVT) is an important component for improving the performance of gasoline engines. The system can adjust the opening and closing time of the intake valve according to changes in engine operating conditions. It is widely used in the field of gasoline engines. The OBD system needs to monitor the working status of the VVT ​​system to ensure that the system is working normally. The fault modes that the OBD system needs to monitor include target errors and slow responses.

[0003] Since the VVT ​​system is mainly composed of a phaser, a camshaft position sensor, a VVT control solenoid valve, and solenoid valve control software. The components in the system are fixedly installed inside the engine body, and the control software controls the opening of the solenoid valve, changes the direction of the internal oil circuit, and drives the relative movement in the phaser through the oil to achieve the change of the valve timing phase relationship. Therefore, it is difficult to process in hardware to simulate the VVT ​​slow response fault.

[0004] The existing VVT response delay simulation scheme generally has the following three means: 1. Slow down the actual position change of VVT by adjusting the PID parameters of VVT control; 2. Connect a resistor in series on the control solenoid valve circuit; 3. Connect an additional VVT control valve to the control harness, and the actual position is always 0. The above three fault simulation methods cannot reliably and stably achieve the demonstration of the fault. The specific problems are as follows: Scheme 1: It will affect the response rate under all working conditions. When the diagnosis is not sampled, the response of VVT will become slow, and it is difficult to enter the diagnosis (entering the response delay fault requires that the actual VVT position and the expected VVT position have a small deviation). In addition, the improper adjustment of the control parameters will lead to the early reporting of the target error fault under long-term steady-state conditions, and the demonstration will fail; Scheme 2: Similar to the results of Scheme 1, the voltage of the control VVT is divided by an external resistor, resulting in a small actual control voltage, which will slow down the rate under all working conditions and affect the entry of diagnosis. In addition, long-term position control deviation will cause premature target error fault reporting and demonstration failure. Solution 3: The actual VVT position remains unchanged, which can easily cause target error fault reporting and demonstration failure. Summary of the invention

[0005] In view of the above problems, a fault simulation method for monitoring slow response of a VVT system is provided, aiming to solve the problems existing in the prior art.

[0006] The specific technical solutions are as follows:

[0007] A fault simulation method for monitoring slow response of a VVT system comprises the following steps:

[0008] S1, fault simulation function enabled;

[0009] S2, wait for appropriate conditions and respond to diagnostic sampling entry;

[0010] S3, taking the current VVT actual position as the required control position and maintaining it unchanged;

[0011] S4, waiting for the response diagnosis sampling to be completed;

[0012] S5, calculating the actual position change rate of the VVT ​​during the sampling process;

[0013] S6, comparing the actual rate of change of the VVT ​​position with a diagnostic threshold of slow response;

[0014] S6. Determine the fault result.

[0015] The fault simulation method for monitoring slow response of the VVT ​​system has the following characteristics: the fault simulation function enabling in step S1 includes:

[0016] When you need to simulate the slow response fault of the VVT ​​system, turn on the function switch and ensure that the fault simulation function is enabled. In the current driving cycle, and after the diagnostic conditions are met, it will enter the fault simulation mode, that is, the actual position of the VVT ​​at the current moment will be used as the control target.

[0017] The fault simulation method for monitoring slow response of the VVT ​​system has the following characteristics: the suitable conditions in step S2 include the following three:

[0018] a. The deviation between the actual VVT position and the expected VVT position is small and lasts for a certain period of time;

[0019] b. Count the changes in the expected position. When the changes are greater than the limit, calculate the rate of change of the expected position during this period of time.

[0020] c. When the rate of change of the expected position is greater than the limit, the sampling of slow response diagnosis is entered.

[0021] The above-mentioned fault simulation method for monitoring slow response of the VVT ​​system also has the following characteristics: step S3 also includes: after entering the slow response diagnosis sampling, since the fault simulation function is enabled, the current actual position of the VVT ​​will be used as the required position for controlling the VVT ​​actuation, and will remain unchanged until the end of the current sampling. During this process, the position deviation of the VVT, that is, the difference between the actual position and the expected position, is 0. After PID control, it can be ensured that the actual position of the VVT ​​remains basically unchanged.

[0022] The fault simulation method for monitoring the slow response of the VVT ​​system has the following characteristics: the condition for waiting for the completion of the response diagnosis sampling in step S4 is:

[0023] a. The sampling time meets the minimum time requirement;

[0024] b. The expected VVT change rate is less than a certain limit or the expected VVT position has a small deviation from the actual VVT position;

[0025] c. During the sampling process, the change direction of VVT must remain in one direction.

[0026] The above-mentioned fault simulation method for monitoring slow response of the VVT ​​system also has the following characteristics: the calculation method in step S5 is: position change / sampling time. When the fault simulation function is enabled, after sampling starts, the actual VVT position remains unchanged, and the calculation rate is 0; when the fault simulation function is not enabled, the actual position changes according to the expected VVT, and the calculation rate is larger.

[0027] The above-mentioned fault simulation method for monitoring the slow response of the VVT ​​system also has the following characteristics: the comparison method of step S6 is to make a fault judgment. When the actual position change rate of the VVT ​​is less than the slow response diagnostic threshold, it is judged that a VVT slow response fault has occurred; when the actual position change rate of the VVT ​​is greater than the slow response diagnostic threshold, it is considered that the VVT ​​response is normal and is not in a faulty state.

[0028] In summary, the beneficial effects of this scheme are:

[0029] In the fault simulation method for monitoring the slow response of the VVT ​​system provided by the present invention, whether the fault simulation function is enabled can be determined by selecting a function switch according to the use requirements. The fault simulation method for monitoring the slow response of the VVT ​​system provided by the present invention has the effect of not affecting the VVT ​​control in normal scenarios, and only turning on the function when a fault needs to be simulated, and has a high flexibility effect.

[0030] In the fault simulation method for monitoring the slow response of the VVT ​​system provided by the present invention, the monitoring sampling time window is very short, that is, the time affecting the VVT ​​control effect is very short, and no other negative effects will be brought to the engine due to the simulated fault. The fault simulation method for monitoring the slow response of the VVT ​​system provided by the present invention has the effect of simulating faults and having little impact on engine performance.

[0031] In the fault simulation method for monitoring the slow response of the VVT ​​system provided by the invention, the fault simulation takes effect only when the diagnostic sampling occurs, and each diagnostic sampling is triggered. The fault simulation method for monitoring the slow response of the VVT ​​system provided by the invention has the effect of being able to simulate faults stably and having good simulation effect, thereby improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the fault simulation method for monitoring the slow response of the VVT ​​system of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0035] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0036] Figure 1 FIG. 1 is a flow chart of a fault simulation method for monitoring slow response of a VVT system according to the present invention, as shown in FIG. Figure 1 As shown, the fault simulation method for monitoring the slow response of the VVT ​​system provided in this embodiment includes the following steps:

[0037] S1, fault simulation function enabled;

[0038] S2, wait for appropriate conditions and respond to diagnostic sampling entry;

[0039] S3, taking the current VVT actual position as the required control position and maintaining it unchanged;

[0040] S4, waiting for the response diagnosis sampling to be completed;

[0041] S5, calculating the actual position change rate of the VVT ​​during the sampling process;

[0042] S6, comparing the actual rate of change of the VVT ​​position with a diagnostic threshold of slow response;

[0043] S6. Determine the fault result.

[0044] It should be noted that, since there is no abnormality in the VVT ​​system during daily vehicle use, the control and response of the VVT ​​can meet the normal use needs of the vehicle. When fault simulation is required, this fault simulation function is turned on. In this mode, the simulated fault function can take effect.

[0045] In the above embodiment, enabling the fault simulation function in step S1 includes:

[0046] When you need to simulate the slow response fault of the VVT ​​system, turn on the function switch and ensure that the fault simulation function is enabled. In the current driving cycle, and after the diagnostic conditions are met, it will enter the fault simulation mode, that is, the actual position of the VVT ​​at the current moment will be used as the control target.

[0047] It should be noted that a function switch is set in the software, and this function is only turned on when a slow response fault needs to be demonstrated. In normal use scenarios, not turning on this function will not affect the normal operation of the VVT ​​system.

[0048] In the above embodiment, the appropriate conditions in step S2 include the following three:

[0049] a. The deviation between the actual VVT position and the expected VVT position is small and lasts for a certain period of time;

[0050] b. Count the changes in the expected position. When the changes are greater than the limit, calculate the rate of change of the expected position during this period of time.

[0051] c. When the rate of change of the expected position is greater than the limit, the sampling of slow response diagnosis is entered.

[0052] In the above embodiment, step S3 also includes: after entering the slow response diagnosis sampling, since the fault simulation function is enabled, the current VVT actual position will be used as the required position for controlling the VVT ​​actuation, and will remain unchanged until the end of the current sampling. During this process, the position deviation of the VVT, that is, the difference between the actual position and the expected position is 0. After PID control, it can be ensured that the actual position of the VVT ​​remains basically unchanged.

[0053] In the above embodiment, the condition for waiting for the completion of the response diagnosis sampling in step S4 is:

[0054] a. The sampling time meets the minimum time requirement;

[0055] b. The expected VVT change rate is less than a certain limit or the expected VVT position has a small deviation from the actual VVT position;

[0056] c. During the sampling process, the change direction of VVT must remain in one direction.

[0057] It should be noted that after entering the diagnosis, according to the operating conditions of the engine, the required VVT position will change further, and the expected position rate after a certain position change will be calculated. When the rate of change of the required position is large enough, the slow response diagnosis can be further performed in this case. When the required rate decreases or the actual position deviates from the required position by a small amount, and the minimum sampling time condition for the diagnosis is met, the current sampling is terminated. At this time, the expected position will be switched to a table lookup based on the operating conditions, and the actual VVT position will be released and no longer locked.

[0058] In the above embodiment, the calculation method in step S5 is: position change / sampling time. When the fault simulation function is enabled, after sampling starts, the actual VVT position remains unchanged and the calculation rate is 0; when the fault simulation function is not enabled, the actual position changes according to the expected VVT, and the calculation rate is larger.

[0059] In the above embodiment, the comparison method of step S6 is to perform a fault judgment. When the actual position change rate of the VVT ​​is less than the slow response diagnostic threshold, it is judged that a VVT slow response fault has occurred; when the actual position change rate of the VVT ​​is greater than the slow response diagnostic threshold, it is considered that the VVT ​​response is normal and is not in a faulty state.

[0060] It should be noted that the diagnostic threshold is the fault judgment standard for slow response, which is set according to the actual response rate of the VVT ​​system in normal state and the actual response rate of the VVT ​​in fault state. The diagnostic limit is generally around 2° / s, while the response rate of a normal VVT system is generally above 10° / s.

[0061] Working principle: set a function switch and turn it on only when it is necessary to demonstrate a slow response fault. Under normal usage scenarios, if this function is not turned on, it will not affect the normal operation of the VVT ​​system. After turning on this function, you need to wait for the conditions for slow response monitoring to be met. When the monitoring conditions are not met, it will not interfere with the normal control of the VVT, so that it is easier to enter the diagnostic state. When the conditions for slow response monitoring are met, the actual position of the VVT ​​at this time is assigned to the target position of the VVT ​​control and maintained unchanged in the diagnostic sampling window. After entering the diagnostic sampling window, the actual position of the VVT ​​no longer changes. After other diagnostic sampling completion conditions are met (minimum sampling time, expected position change rate, deviation between the actual position and the expected position, etc.), the change rate of the actual position can be calculated. The change rate of the actual position is compared with the preset slow response diagnostic threshold to determine the fault, that is, the slow fault simulation is completed.

[0062] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A fault simulation method for monitoring slow response of a VVT system, characterized in that: The following steps are involved: S1, fault simulation function enabled; S2, wait for appropriate conditions and respond to diagnostic sampling entry; S3, taking the current VVT actual position as the required control position and maintaining it unchanged; S4, waiting for the response diagnosis sampling to be completed; S5, calculating the actual position change rate of the VVT ​​during the sampling process; S6, comparing the actual rate of change of the VVT ​​position with a diagnostic threshold of slow response; S6. Determine the fault result.

2. A fault simulation method for monitoring slow response of a VVT system according to claim 1, characterized in that: The fault simulation function enabling in step S1 includes: When you need to simulate the slow response fault of the VVT ​​system, turn on the function switch and ensure that the fault simulation function is enabled. In the current driving cycle, and after the diagnostic conditions are met, it will enter the fault simulation mode, that is, the actual position of the VVT ​​at the current moment will be used as the control target.

3. A fault simulation method for monitoring slow response of a VVT system according to claim 2, characterized in that: Suitable conditions in step S2 include the following three: a. The deviation between the actual VVT position and the expected VVT position is small and lasts for a certain period of time; b. Count the changes in the expected position. When the changes are greater than the limit, calculate the rate of change of the expected position during this period of time. c. When the rate of change of the expected position is greater than the limit, the sampling of slow response diagnosis is entered.

4. A fault simulation method for monitoring slow response of a VVT system according to claim 3, characterized in that: The step S3 also includes: after entering the slow response diagnosis sampling, since the fault simulation function is enabled, the current VVT actual position will be used as the required position for controlling the VVT ​​actuation, and will remain unchanged until the end of the current sampling. During this process, the position deviation of the VVT, that is, the difference between the actual position and the expected position is 0. After PID control, it can be ensured that the actual position of the VVT ​​remains basically unchanged.

5. A fault simulation method for monitoring slow response of a VVT system according to claim 4, characterized in that: The condition for waiting for the response diagnostic sampling to be completed in step S4 is: a. The sampling time meets the minimum time requirement; b. The expected VVT change rate is less than a certain limit or the expected VVT position has a small deviation from the actual VVT position; c. During the sampling process, the change direction of VVT must remain in one direction.

6. A fault simulation method for monitoring slow response of a VVT system according to claim 5, characterized in that: The calculation method in step S5 is: position change / sampling time. When the fault simulation function is enabled, after sampling starts, the actual VVT position remains unchanged and the calculation rate is 0; when the fault simulation function is not enabled, the actual position changes according to the expected VVT, and the calculation rate is larger.

7. A fault simulation method for monitoring slow response of a VVT system according to claim 6, characterized in that: The comparison method of step S6 is to perform fault judgment. When the actual position change rate of the VVT ​​is less than the slow response diagnostic threshold, it is judged that a VVT slow response fault has occurred; when the actual position change rate of the VVT ​​is greater than the slow response diagnostic threshold, it is considered that the VVT ​​response is normal and is not in a faulty state.

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