A method and device for diagnosing faults of pressure sensors in hydraulic systems

Abstract

The present invention relates to a method and device for diagnosing a fault of a pressure sensor in a hydraulic system. The method comprises: determining whether the hydraulic system has been depressurized based on the oil temperature and depressurization time of the hydraulic system; when the hydraulic system has been depressurized, obtaining the real-time pressure value of the pressure sensor, judging whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold, and reporting the fault of the pressure sensor based on the judgment result. Compared with the prior art, the present invention has the advantages of high robustness and high diagnostic coverage.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic system diagnosis, and in particular to a method and device for diagnosing faults of a hydraulic system pressure sensor. Background Art

[0002] Sensor diagnosis generally includes value out-of-range diagnosis and rationality diagnosis. For systems where the actuator is hydraulically controlled, due to cost constraints, only one pressure sensor is installed in the main oil circuit to meet the needs of the system control function. This places high demands on the rationality diagnosis strategy design of pressure sensors. Due to hardware limitations, the diagnostic coverage of pressure sensors is not high, which is specifically reflected in:

[0003] 1) The hydraulic system itself is relatively complex, with many oil circuit branches. The leakage of various valve bodies varies in different states. At the same time, the oil temperature and oil pressure will also affect the leakage of the hydraulic system. In addition, the consistency and aging wear of the system need to be taken into account. Therefore, it is very difficult to calculate the main oil circuit pressure through a mathematical model, and the diagnostic robustness cannot be guaranteed;

[0004] 2) Performing reasonable diagnosis of pressure sensors under special working conditions, such as verifying whether the pressure is at the preset value when the hydraulic system reaches dynamic balance. This solution also needs to consider the above factors, and the diagnostic robustness is difficult to guarantee;

[0005] 3) Based on the above situation, rationality diagnosis is usually designed to monitor the physical characteristics of the pressure signal. For example, if the pressure change rate exceeds expectations, this strategy cannot diagnose whether the pressure value is accurate, and the diagnostic coverage is low. Summary of the invention

[0006] The purpose of the present invention is to provide a method and device for diagnosing hydraulic system pressure sensor faults in order to overcome the defects of the prior art.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for diagnosing a fault of a pressure sensor in a hydraulic system, the method comprising:

[0009] Determine whether the hydraulic system has been depressurized based on the hydraulic system oil temperature and depressurization time;

[0010] When the hydraulic system is depressurized, the real-time pressure value of the pressure sensor is obtained, and it is determined whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold, and the fault condition of the pressure sensor is reported based on the determination result.

[0011] Preferably, the specific method of determining whether the hydraulic system has been depressurized includes:

[0012] Get the vehicle shutdown time;

[0013] Estimate the hydraulic system oil temperature and determine the estimated oil temperature value;

[0014] The vehicle shutdown time is used as the pressure relief time, and based on the oil temperature-pressure relief time curve, it is determined whether the pressure relief is completed under the current oil temperature estimate and pressure relief time.

[0015] Preferably, the whole vehicle shutdown time is obtained through the shutdown time flag of the engine control module. When the shutdown time is in the flag position, the whole vehicle shutdown time reaches the set shutdown time.

[0016] Preferably, the method for estimating the oil temperature of the hydraulic system includes: obtaining the oil temperature T of the hydraulic system when it was last powered on before the vehicle was turned off s And the oil temperature T when the power was last turned off x , take T s 、T x The smaller value T min As an estimate of the oil temperature.

[0017] Preferably, the method of determining whether the pressure relief is completed under the current oil temperature estimate and pressure relief time based on the oil temperature-pressure relief time curve includes: taking the vehicle shutdown time as the pressure relief time, and determining the minimum oil temperature for completing the pressure relief under the pressure relief time based on the oil temperature-pressure relief time curve; if the current oil temperature estimate is greater than the minimum oil temperature for pressure relief, the pressure relief is completed.

[0018] Preferably, if the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds a pressure difference threshold and lasts for a set period of time, a pressure sensor failure is reported.

[0019] Preferably, the pressure difference threshold is 5 bar.

[0020] Preferably, the set duration is 1 second.

[0021] Preferably, the oil temperature-pressure relief time curve is obtained by testing in a low-temperature chamber, a pressure relief test is performed on the hydraulic system in the low-temperature chamber, discrete points of pressure relief time at different temperatures are obtained, and the oil temperature-pressure relief time curve is fitted based on the discrete points.

[0022] A hydraulic system pressure sensor diagnostic device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to implement the hydraulic system pressure sensor fault diagnostic method when executing the computer program.

[0023] The present invention has the following advantages:

[0024] (1) The pressure sensor diagnosis scheme of the present invention avoids the construction of a complex hydraulic system model and selects the special working condition after the hydraulic system is depressurized for diagnosis, which simplifies the complexity and ensures the robustness of the diagnosis;

[0025] (2) The present invention realizes the diagnosis of the rationality of the pressure value of the hydraulic system, has high diagnostic coverage, and improves the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the connection of the hydraulic system;

[0027] Figure 2 It is a general flow chart of the hydraulic system pressure sensor diagnosis method in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the oil temperature-pressure relief time curve in an embodiment of the present invention.

[0029] Figure 4 The present invention is a specific flowchart of a method for diagnosing a pressure sensor in a hydraulic system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Note that the following embodiments are merely illustrative in nature, and the present invention is not intended to limit its applicable objects or uses, and the present invention is not limited to the following embodiments.

[0031] like Figure 1 As shown, a schematic block diagram of a connection of the hydraulic system of this embodiment, the hydraulic system includes an oil pump, a safety relief valve (SRV, Safety Relief Valve), an accumulator, a solenoid valve (PPV), and an actuator. The oil pump is used to fill the high-pressure side with oil, the safety relief valve is pressurized by the accumulator, and the controller provides the actuator with corresponding pressure by controlling the solenoid valve. In this embodiment, the hydraulic system has three branch oil circuits, and the three branch oil circuits are located after the main oil circuit. There are three solenoid valves (PPV) and three actuators, and each branch oil circuit has a set of solenoid valves and actuators, which are defined as the first solenoid valve 1 and the first actuator 1, the second solenoid valve 2 and the second actuator 2, and the third solenoid valve 3 and the third actuator 3. The pressure sensor is installed in the main oil circuit for high-pressure side oil filling and pressure maintenance control and main oil circuit pressure monitoring to meet the actuator working pressure of each branch oil circuit and protect the hydraulic system at the same time.

[0032] Based on regulatory requirements and FMEA, the fault diagnosis of pressure sensors plays a key role in the oil pressure control and protection of the entire hydraulic system. The present invention mainly relates to a pressure sensor fault diagnosis method involved in the pressure necessity and rationality diagnosis.

[0033] like Figure 2 As shown, the present invention provides a method for diagnosing a pressure sensor in a hydraulic system, the method comprising:

[0034] Determine whether the hydraulic system has been depressurized based on the hydraulic system oil temperature and depressurization time;

[0035] When the hydraulic system is depressurized, the real-time pressure value of the pressure sensor is obtained, and the pressure sensor fault is reported by judging whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold. The pressure difference threshold can be set to 5 bar according to the sensitivity requirements of the hydraulic system for the pressure sensor.

[0036] After the hydraulic system is depressurized, the pressure sensor fault is judged, which reduces the leakage of each branch oil circuit due to different valve bodies in different states. At the same time, factors such as oil temperature and oil pressure affect the leakage of the hydraulic system, and the influence of aging and wear on the pressure sensor diagnosis scheme, avoiding the model construction of complex hydraulic systems. The diagnosis is performed under this special working condition after the hydraulic system is depressurized, which simplifies the complexity and ensures the robustness of the diagnosis. By judging whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold, the hydraulic system pressure value is diagnosed in a more reasonable manner, with high diagnostic coverage and improved system safety.

[0037] In a preferred embodiment of the present invention, the specific method of determining whether the hydraulic system is hydraulically completed includes:

[0038] Get the vehicle shutdown time;

[0039] Estimate the hydraulic system oil temperature and determine the estimated oil temperature value;

[0040] The vehicle shutdown time is used as the pressure relief time, and based on the oil temperature-pressure relief time curve, it is determined whether the pressure relief is completed under the current oil temperature estimate and pressure relief time.

[0041] The vehicle shutdown time is obtained through the shutdown time flag of the engine control module. When the shutdown time flag is set, the vehicle shutdown time reaches the set shutdown time. The method of estimating the hydraulic system oil temperature includes: obtaining the oil temperature T of the hydraulic system when it was last powered on before the vehicle was shut down s And the oil temperature T when the power was last turned off x , take T s 、T x The smaller value T minAs the oil temperature estimation value. On the basis of the above, the method of determining whether the pressure relief is completed under the current oil temperature estimation value and pressure relief time based on the oil temperature-pressure relief time curve includes: setting the flameout time as the pressure relief time, determining the minimum pressure relief oil temperature for completing the pressure relief under the pressure relief time based on the oil temperature-pressure relief time curve; if the current oil temperature estimation value is greater than the minimum pressure relief oil temperature, the pressure relief is completed.

[0042] The oil temperature-pressure relief time curve is obtained by testing in a low-temperature chamber. The hydraulic system is tested for pressure relief in a low-temperature chamber to obtain discrete points of pressure relief time at different temperatures. The oil temperature-pressure relief time curve is fitted based on the discrete points. Through testing in a low-temperature chamber, the time it takes for the hydraulic system to release pressure from 55 bar to atmospheric pressure at different temperatures is as follows: Figure 3 As shown, it can be seen that the pressure relief can only be completed when the specified time is reached at a certain temperature.

[0043] In the above preferred embodiment, the flameout time flag of the engine control module is fully utilized to obtain the flameout time of the whole vehicle, so as to serve as the basis for judging whether the pressure relief is completed. There is no need to add an additional timing system to monitor the pressure relief time. The diagnosis of the present invention can be realized by making simple improvements on the existing vehicle system, which has low investment cost and is easy to implement. In addition, the oil temperature is estimated by taking the minimum value of the oil temperature when the hydraulic system was last powered on and last powered off before the whole vehicle was turned off, so as to ensure the accuracy of the pressure relief judgment and improve the effectiveness of the fault diagnosis.

[0044] In another preferred embodiment of the present invention, if the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold and lasts for a set time, a pressure sensor failure is reported. In this embodiment, the set time is 1 second and the pressure difference threshold is 5 bar.

[0045] In this preferred real-time mode, a fault report is performed after the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold and lasts for a set period of time, thereby avoiding misjudgment of faults and ensuring the reliability of the fault diagnosis method.

[0046] In summary, the following is a most preferred embodiment to specifically describe the design concept of a hydraulic system pressure sensor diagnosis method of the present invention:

[0047] 1) Enabling conditions for pressure sensor fault diagnosis

[0048] For rationality diagnosis, it is necessary to define working conditions suitable for diagnostic operation to meet robustness requirements. Fault detection logic can only be run after the enabling conditions are met.

[0049] Usually, diagnostic monitoring enabling conditions include three categories:

[0050] FID (Function identifier), used for root faults to suppress the reporting of secondary faults;

[0051] General window conditions, generally vehicle mode, KL30 voltage and other general conditions;

[0052] Special window conditions, the enabling condition for the hydraulic system pressure sensor diagnosis of the present invention is selected as the specific working condition that the hydraulic system has completed pressure relief.

[0053] The present invention selects the whole vehicle to be powered off, and the diagnosis is performed after the hydraulic system is depressurized. It is not necessary to consider the influence of the oil pump speed and the actuator action on the hydraulic system pressure, and only the two variables of pressure and oil temperature need to be considered.

[0054] In this embodiment, since the hydraulic system itself does not have the function of power-off timing, it is necessary to use the soak time signal (ignition off time flag signal) issued by the ECM (Engine Control Modular). In this embodiment, it is set that when the vehicle is turned off for more than 6 hours, the signal will be set, so it is necessary to ensure that the pressure relief is completed within 6 hours. Figure 3 , the corresponding temperature is -15℃; in addition, the ambient temperature when the PCM is powered off needs to be saved in NVRAM and compared with the ambient temperature when the PCM is powered on, and the smaller one is selected. min For reference.

[0055] Therefore, the hydraulic system pressure relief is judged as follows: when the soak time is in the set position, T min Greater than -15℃.

[0056] 2) Fault Detection Strategy

[0057] When the real-time pressure value of the pressure sensor deviates from the atmospheric pressure value by more than 5 bar and lasts for 1 second, a fault is reported.

[0058] 3) Specific process of fault diagnosis

[0059] like Figure 4 As shown:

[0060] Start pressure sensor fault diagnosis;

[0061] Determine that soak time is in the set position (soak time = 1) and T min Greater than -15°C, if so, obtain the real-time pressure value of the pressure sensor;

[0062] Determine whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold. The pressure difference threshold is set to 5 bar. If so, monitor the pressure difference timing;

[0063] If the duration reaches the set time (set to 1 second in this embodiment), a pressure sensor failure is reported, otherwise the test passes.

[0064] Based on the above-mentioned hydraulic system pressure sensor diagnostic method, the present invention also provides a hydraulic system pressure sensor diagnostic device, including a memory and a processor, the memory is used to store a computer program, and the processor is used to implement the above-mentioned hydraulic system pressure sensor diagnostic method when executing the computer program.

[0065] The above embodiments are merely examples and do not limit the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical concept of the present invention.

Claims

1. A method for diagnosing a fault of a pressure sensor in a hydraulic system, characterized in that: The method includes: Determine whether the hydraulic system has been depressurized based on the hydraulic system oil temperature and depressurization time; When the hydraulic system is depressurized, the real-time pressure value of the pressure sensor is obtained, and it is determined whether the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold, and the fault condition of the pressure sensor is reported based on the determination result; The specific method of determining whether the hydraulic system has been depressurized includes: Get the vehicle shutdown time; Estimate the hydraulic system oil temperature and determine the estimated oil temperature value; The vehicle shutdown time is used as the pressure relief time, and whether the pressure relief is completed under the current oil temperature estimate and the pressure relief time is determined based on the oil temperature-pressure relief time curve; The method of determining whether pressure relief is completed under the current oil temperature estimate and pressure relief time based on the oil temperature-pressure relief time curve includes: taking the vehicle shutdown time as the pressure relief time, and determining the minimum oil temperature for pressure relief under the pressure relief time based on the oil temperature-pressure relief time curve; if the current oil temperature estimate is greater than the minimum oil temperature for pressure relief, the pressure relief is completed.

2. A method for diagnosing a hydraulic system pressure sensor fault according to claim 1, characterized in that: The whole vehicle shutdown duration is obtained through the shutdown time flag of the engine control module. When the shutdown time is in the flag position, the whole vehicle shutdown duration reaches the set shutdown duration.

3. A hydraulic system pressure sensor fault diagnosis method according to claim 1, characterized in that: The method for estimating the hydraulic system oil temperature includes: obtaining the oil temperature T of the hydraulic system when it was last powered on before the vehicle was turned off s And the oil temperature T when the power was last turned off x , take T s 、T x The smaller value T min As an estimate of the oil temperature.

4. A method for diagnosing a hydraulic system pressure sensor fault according to claim 1, characterized in that: If the difference between the real-time pressure value of the pressure sensor and the atmospheric pressure value exceeds the pressure difference threshold and lasts for a set period of time, a pressure sensor failure is reported.

5. A method for diagnosing a hydraulic system pressure sensor fault according to claim 1 or 4, characterized in that: The pressure difference threshold is 5 bar.

6. A method for diagnosing a hydraulic system pressure sensor fault according to claim 4, characterized in that: The set duration is 1 second.

7. A method for diagnosing a hydraulic system pressure sensor fault according to claim 1, characterized in that: The oil temperature-pressure relief time curve is obtained by testing in a low-temperature chamber. A pressure relief test is performed on the hydraulic system in the low-temperature chamber to obtain discrete points of pressure relief time at different temperatures, and the oil temperature-pressure relief time curve is fitted based on the discrete points.

8. A hydraulic system pressure sensor fault diagnosis device, characterized in that: The method comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to implement the hydraulic system pressure sensor fault diagnosis method according to any one of claims 1 to 7 when executing the computer program.

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