A method for handling faults in a vacuum booster system

Abstract

The present invention discloses a method for handling faults in a vacuum assist system, which specifically includes the following steps: Step S1, according to the division of functional modules, three types of fault monitoring are also set up, namely, fault monitoring of the braking intention detection and perception module, fault monitoring of the environment and actuator perception module, and fault monitoring of the vacuum degree control module. When any fault occurs, corresponding countermeasures can be taken. The present invention sets corresponding faults for problems that can be sensed and judged, and performs a certain filtering algorithm processing on the credibility of each fault to prevent misjudgment of faults caused by accidental factors. After the filtering algorithm processing, if the fault is still in a confirmed state, it is considered that the fault actually exists, and the fault is reported, thereby activating the corresponding fault handling mechanism, fully ensuring braking safety after the fault occurs, avoiding affecting the safety of the driver and passengers when a fault occurs in the braking assist system, and effectively improving the safety of the braking function.

Description

Technical Field

[0001] The present invention relates to the field of new energy vehicles. Specifically, the present invention relates to a method for handling faults in a vacuum booster system. Background Art

[0002] At present, almost all vehicles are equipped with a brake booster system. In particular, the use of a vacuum brake booster system is very popular. Its principle is to utilize the pressure difference between the vacuum generated during engine operation and the atmospheric pressure to force the rubber diaphragm in the brake vacuum booster to move, pushing the piston of the master cylinder, thereby reducing the force required to step on the brake pedal.

[0003] As a common brake configuration for new energy commercial vehicles, the vacuum booster brake system is widely used in different types of new energy commercial vehicle products. Compared with other types of brake systems, the vacuum booster system has advantages such as low cost and good braking linearity. Its system mainly consists of a vacuum pump, a pressure detection sensor, etc. If related components fail, it will have a greater impact on braking safety and threaten the lives and property safety of the driver and passengers. Therefore, meticulous fault diagnosis should be carried out for all detectable faults, and at the same time, the fault handling after the occurrence of a fault should be reasonable and have a certain redundancy to maximize the guarantee of braking safety after the occurrence of a fault. Summary of the Invention

[0004] The present invention provides a method for handling faults in a vacuum booster system, which fully guarantees braking safety after the occurrence of a fault, avoids affecting the safety of the driver and passengers when the brake booster system fails, and effectively improves the safety of the braking function.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for handling faults in a vacuum booster system, specifically including the following steps:

[0006] Step S1, according to the division of functional modules, three types of fault monitoring are also set, namely, fault monitoring of the braking intention detection and perception module, fault monitoring of the environment and execution unit perception module, and fault monitoring of the vacuum degree control module. When any fault occurs, targeted response and handling can be carried out;

[0007] Step S2, for the fault of the braking intention detection and perception module, which directly affects the perception and decision-making of braking energy recovery control, targeted handling needs to be carried out according to the severity of each fault after its occurrence;

[0008] Step S3, for the fault of the environment and execution unit perception module, which directly affects the judgment of the vacuum pressure of the vacuum pump and thus affects the enabling control of the vacuum pump;

[0009] Step S4. For the vacuum degree fault, which directly affects the vacuum assist performance. Insufficient vacuum degree will lead to insufficient braking assist, affecting the force assist intensity when the driver steps on the brake pedal during braking, possibly resulting in insufficient depression of the brake pedal and further affecting the braking force, leading to braking safety risks.

[0010] Step S5. For the enabling control of the vacuum pump, when a fault occurs in the environment and actuator perception module or a vacuum degree fault occurs, to ensure the braking performance to the greatest extent, when the driver has no intention of stepping on the brake, the vacuum pump works intermittently, and when the driver has a braking intention, the vacuum pump works continuously.

[0011] Step S6. When the vacuum degree fault in Step S4 occurs and the vacuum assist system has clearly failed to provide normal vacuum assist, the processing method in Step S5 can ensure that the vacuum pump works at its maximum capacity. However, uncertain factors such as the state of mechanical components like pipelines may still cause the system to be unable to provide normal and sufficient vacuum assist. In this case, by identifying the difference err between the vacuum pressure and the normal set threshold, the braking intensity r of the electric brake is dynamically adjusted. At the same time, combined with the opening t obtained by the brake angle sensor, the deficiency of the mechanical braking force is dynamically compensated from the perspective of the electric brake. A braking force compensation table is set up, and the electric brake intensity correction coefficient r is output by looking up the table through the difference err and the vehicle speed v. The overall change trend of the electric brake intensity correction coefficient r is that when the difference err is larger and the vehicle speed v is larger, the electric brake intensity correction coefficient r is larger. At the same time, considering that after the electric brake increases, the rear wheels may skid due to uneven distribution of the front and rear wheel braking forces. Therefore, the vehicle controller VCU needs to monitor the slip ratio between the front and rear wheels in real time at this time. When the slip ratio is large, the electric brake needs to be controlled to withdraw, and when the slip ratio drops to the normal range, the electric brake intervenes again. The electric brake torque size in the fault state is calculated based on the basic energy recovery map, the electric brake intensity correction coefficient r, and the opening t of the brake angle sensor.

[0012] Preferably, the specific processing method in Step S2 is as follows:

[0013] Step S2.1. If a short - circuit to power or short - circuit to ground fault occurs in the brake pedal angle sensor, after the fault is reported through debounce, when one path fails, the other path is trusted, giving full play to the advantage of the dual - path redundancy design to ensure the normal operation of the brake opening detection function.

[0014] Step S2.2: If a rationality fault occurs in the brake pedal switch signal, that is, when the brake opening degrees of both channels are greater than the threshold value while the brake switch state is not depressed, or when the brake opening degrees of both channels are less than the threshold value while the brake switch state is depressed, it is considered that a rationality fault has occurred in the brake pedal switch signal. Cancel the judgment of the brake switch and adjust to solely use the brake angle sensor to judge the driver's braking operation to control driving and braking energy recovery;

[0015] Step S2.3: If a rationality fault occurs in the brake pedal angle sensor, that is, when twice the signal voltage of the first channel minus the signal voltage of the second channel is greater than the threshold value, it is considered that a rationality fault has occurred in the brake pedal angle sensor. Take the smaller value of the two-channel brake signals to prevent excessive superposition of the braking energy recovery intensity and cause danger;

[0016] Step S2.4: If a rationality fault occurs in brake pedal angle sensor 1 or brake pedal angle sensor 2, that is, when the brake switch and the change trend of the other channel of the brake signal are the same while the signal of this channel is in the opposite state, take the signal of the other channel for use, giving full play to the advantage of the dual-channel redundant design to ensure the normal operation of the brake opening detection function.

[0017] Preferably, when two or more faults are reported in steps 2.1 to 2.4, zero-power processing is performed because the braking intention cannot be detected.

[0018] Preferably, the specific processing method in step S3 is as follows:

[0019] Step S3.1: If a signal voltage abnormality fault occurs in the ambient pressure sensor, the vehicle control unit (VCU) controls the vehicle to perform speed limit processing to prevent inaccurate judgment of the vacuum pressure threshold due to abnormal ambient pressure detection, which may affect the vacuum assist and further affect the braking function. The enabling prerequisite for this fault diagnosis is that there is no abnormality fault in the 5V power supply and the vehicle low-voltage power supply is normal;

[0020] Step S3.2: If a signal voltage abnormality occurs in the vacuum pump pressure sensor, the vehicle control unit (VCU) controls the vehicle to perform speed limit processing to prevent abnormal vacuum pump pressure detection from directly affecting the enabling and closing threshold judgments of the vacuum pump. The prerequisite for this fault diagnosis is that there is no abnormality fault in the 5V power supply of the brake vacuum pressure sensor and the vehicle low-voltage power supply is normal;

[0021] Step S3.3: For the short power supply (control), short circuit to ground, or open circuit fault of the vacuum pump enabling signal, since the vacuum pump enabling control is a low-effective output, for the short power supply fault, it will cause the vacuum pump not to suck in, that is, the vacuum pump cannot work. In addition, since the short circuit to ground and open circuit faults cannot be detected separately, in order to avoid misjudgment, they are uniformly processed as the vacuum pump not working. After the fault is reported, limp-home processing is required for all;

[0022] Step S3.4: If a 5V power supply anomaly fault occurs in the vacuum pressure sensor, this fault will affect the monitoring of the vacuum pressure. The vehicle control unit (VCU) will send a braking system fault to the instrument through the bus. After receiving it, the instrument will light up the braking system fault light to prompt the driver to pay attention to the maintenance.

[0023] Preferably, when two or more faults are reported simultaneously in steps S3.1 to S3.4, a limp-home process is executed.

[0024] Preferably, the specific processing method in step S4 is as follows:

[0025] Step S4.1: For the rapid leakage fault of the vacuum pump, this fault is reported when the brake switch is not closed, the vacuum pump is not enabled to output, and the vacuum degree reduction rate is greater than 3 kPa / s. At this time, the vacuum assist performance has been greatly affected. The vehicle control unit (VCU) controls the vehicle to perform speed limit processing. The enabling prerequisite for this fault diagnosis is that there is no anomaly fault in the signal voltage of the vacuum pump pressure sensor.

[0026] Step S4.2: For the working overtime fault of the vacuum pump, when the brake switch is not closed and the vacuum pump continuously enables output for more than 30 s, since the vacuum degree itself meets the braking performance at this time, the vehicle control unit (VCU) controls the vehicle to perform slight speed limit processing. The enabling prerequisite for this fault diagnosis is that there is no anomaly fault in the signal voltage of the vacuum pump pressure sensor and there is no short power supply (relay control) fault in the vacuum pump enabling signal.

[0027] Step S4.3: For the low vacuum fault of the vacuum pump, when the vacuum pump continuously enables output for more than 5 s but the vacuum degree is higher than -25 kPa, at this time, the vacuum assist performance has been greatly affected. The vehicle control unit (VCU) controls the vehicle to perform speed limit processing. The enabling prerequisite for this fault diagnosis is that there is no anomaly fault in the signal voltage of the vacuum pump pressure sensor.

[0028] The beneficial effects of adopting the above technical solutions are:

[0029] 1. The vacuum booster system of the present invention is divided into three modules according to functions, namely: a braking intention detection and perception module, an environment and execution unit perception module failure, and a vacuum degree control module. The braking intention detection and perception module includes a brake switch and a brake angle sensor. The environment and execution unit perception module includes an atmospheric pressure sensor and a vacuum pressure sensor. The vacuum degree control module includes a decision-making unit as the vehicle controller and an execution module as the vacuum pump. A failure in any of the above three modules will affect the braking function or performance. Therefore, corresponding faults are set for the problems that can be perceived and judged, and a certain filtering algorithm is processed for the credibility of each fault to prevent misjudgment of faults caused by accidental factors. After being processed by the filtering algorithm, if the fault is still in a confirmed state, it is considered that the fault actually exists, and the fault is reported, thereby activating the corresponding fault handling mechanism, fully ensuring the braking safety after the fault occurs, avoiding affecting the safety of the driver and passengers when the braking booster system fails, and effectively improving the safety of the braking function. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the diagnostic architecture diagram of the present invention;

[0031] Figure 2 is the fault monitoring and control flow chart of the braking intention detection and perception module of the present invention;

[0032] Figure 3 is the fault monitoring and control flow chart of the environment and execution unit perception module of the present invention;

[0033] Figure 4 is the fault monitoring and control flow chart of the vacuum degree control module of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0034] The following is a more detailed description of the specific implementation of the present invention by referring to the accompanying drawings and describing the embodiments, aiming to help those skilled in the art have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitate its implementation.

[0035] As Figures 1 to 4 shown, the present invention is a method for handling faults in a vacuum booster system, which fully ensures the braking safety after the fault occurs, avoids affecting the safety of the driver and passengers when the braking booster system fails, and effectively improves the safety of the braking function.

[0036] Specifically, as Figures 1 to 4 shown, it specifically includes the following steps:

[0037] Step S1, according to the functional module classification, fault monitoring is also set into three categories, namely, fault monitoring of the braking intention detection perception module, fault monitoring of the environment and execution unit perception module, and fault monitoring of the vacuum control module, so that when any fault occurs, a targeted response can be carried out;

[0038] Step S2: For the failure of the braking intention detection sensing module, which directly affects the perception and decision-making of the braking energy recovery control, targeted processing is required according to the severity of each failure after it occurs;

[0039] Step S3, for the environment and execution unit sensing module failure, which directly affects the determination of the vacuum pressure of the vacuum pump, and further affects the enabling control of the vacuum pump;

[0040] Step S4, for vacuum failure, which directly affects the vacuum boost performance, insufficient vacuum will lead to insufficient brake boost, affecting the force of the driver's brake pedal during braking, which may cause insufficient depression of the brake pedal and thus affect the braking force, resulting in a braking safety risk;

[0041] Step S5, for enabling control of the vacuum pump, when the environment and the execution unit sensing module fails or a vacuum failure occurs, in order to ensure the braking performance to the greatest extent, the vacuum pump works intermittently when the driver has no intention to brake, and keeps working continuously when the driver has the intention to brake;

[0042] Step S6, when the vacuum failure in step S4 occurs, the vacuum boost system has clearly failed to provide vacuum boost normally. The processing method in step S5 can ensure that the vacuum pump can work at its maximum capacity, but uncertain factors such as the state of mechanical components such as pipelines may cause the system to still be unable to provide normal and sufficient vacuum boost. In this case, the braking intensity r of the electric brake is dynamically adjusted by identifying the difference err between the vacuum pressure and the normal set threshold. At the same time, combined with the opening t obtained by the brake angle sensor, the lack of mechanical braking force is dynamically compensated from the electric braking angle, and the braking force compensation table is set. The electric brake intensity correction coefficient r is output by looking up the table through the difference err and the vehicle speed v. The overall change trend of the electric brake intensity correction coefficient r is that when the difference err is larger and the vehicle speed v is larger, the electric brake intensity correction coefficient r is larger. At the same time, considering that after the electric brake is increased, the uneven distribution of the braking force of the front and rear wheels may cause the rear wheel to drift, the vehicle controller VCU needs to monitor the slip rate between the front and rear wheels in real time. When the slip rate is large, the electric brake needs to be controlled to exit. When the slip rate drops to within the normal range, the electric brake will intervene again. The electric brake torque under the fault state is calculated based on the basic energy recovery map, the electric brake intensity correction coefficient r and the brake angle sensor opening t.

[0043] The specific processing method in step S2 is as follows:

[0044] Step S2.1, if a short circuit to power or a short circuit to ground occurs in the brake pedal angle sensor, after the fault is reported through debounce, when a fault occurs in one path, the other path is trusted, giving full play to the advantage of the dual-channel redundant design to ensure the normal operation of the brake opening detection function;

[0045] Step S2.2, if a rationality fault occurs in the brake pedal switch signal, that is, when both paths of the brake opening are greater than the threshold value while the brake switch state is not depressed, or when both paths of the brake opening are less than the threshold value while the brake switch state is depressed, it is considered that a rationality fault has occurred in the brake pedal switch signal at this time. The judgment of the brake switch is cancelled, and it is adjusted to simply use the brake angle sensor to judge the driver's braking operation to control drive and brake energy recovery;

[0046] Step S2.3, if a rationality fault occurs in the brake pedal angle sensor, that is, when twice the signal voltage of the first path minus the signal voltage of the second path is greater than the threshold value, it is considered that a rationality fault has occurred in the brake pedal angle sensor. The smaller value of the two paths of brake signals is taken to prevent the excessive superposition of the brake energy recovery intensity from causing danger;

[0047] Step S2.4, if a rationality fault occurs in brake pedal angle sensor 1 or brake pedal angle sensor 2, that is, when the brake switch and the change trend of the other path of brake signal are the same, while the signal of this path is in the opposite state, the other path is trusted for processing, giving full play to the advantage of the dual-channel redundant design to ensure the normal operation of the brake opening detection function.

[0048] When two or more faults are reported simultaneously in Steps 2.1 to 2.4, zero-power processing is performed because the braking intention cannot be detected.

[0049] The specific processing method in Step S3 is as follows:

[0050] Step S3.1, if a signal voltage abnormality fault occurs in the ambient pressure sensor, the vehicle control unit VCU controls the vehicle to perform speed limit processing to prevent the abnormal detection of the ambient pressure from causing the misjudgment of the vacuum pressure threshold, thereby affecting the vacuum assist and further affecting the braking function; the enabling prerequisite condition for this fault diagnosis is that there is no abnormal 5V power supply fault and the vehicle low-voltage power supply is normal;

[0051] Step S3.2, if a signal voltage abnormality occurs in the vacuum pump pressure sensor, the vehicle control unit VCU controls the vehicle to perform speed limit processing to prevent the abnormal detection of the vacuum pump pressure from directly affecting the enabling and closing threshold judgments of the vacuum pump. The prerequisite condition for this fault diagnosis is that there is no abnormal 5V power supply fault in the brake vacuum pressure sensor and the vehicle low-voltage power supply is normal;

[0052] Step S3.3, there is a short power supply (control), short to ground or open circuit fault in the vacuum pump enable signal. Since the vacuum pump enable control is a low-effective output, for the short power supply fault, it will cause the vacuum pump to fail to engage, that is, the vacuum pump cannot work. In addition, since the short to ground and open circuit faults cannot be detected separately, in order to avoid misjudgment, they are uniformly processed as the vacuum pump cannot work. After the fault is reported, a limp-home process needs to be performed;

[0053] Step S3.4, if there is an abnormal 5V power supply fault in the vacuum pressure sensor, this fault will affect the monitoring of the vacuum pressure. The vehicle control unit VCU will send a braking system fault to the instrument through the bus. After receiving it, the instrument will light up the braking system fault light to prompt the driver to pay attention to the repair.

[0054] For the faults in steps S3.1 to S3.4, when two or more faults are reported simultaneously, a limp-home process is performed.

[0055] The specific processing method in step S4 is as follows:

[0056] Step S4.1, for the fast leakage fault of the vacuum pump, when the brake switch is not closed, the vacuum pump does not enable output, and the vacuum degree reduction rate is greater than 3 kPa / s, this fault is reported. At this time, the vacuum assist performance has been greatly affected. The vehicle control unit VCU controls the vehicle to perform speed limit processing. The enabling prerequisite condition for this fault diagnosis is that there is no abnormal fault in the signal voltage of the vacuum pump pressure sensor;

[0057] Step S4.2, for the vacuum pump working overtime fault, when the brake switch is not closed and the vacuum pump continuously enables output for more than 30 s, since the vacuum degree itself meets the braking performance at this time, the vehicle control unit VCU controls the vehicle to perform a slight speed limit processing. The enabling prerequisite condition for this fault diagnosis is that there is no abnormal fault in the signal voltage of the vacuum pump pressure sensor and there is no short power supply (relay control) fault in the vacuum pump enable signal;

[0058] Step S4.3, for the low vacuum fault of the vacuum pump, the vacuum pump continuously enables output for more than 5 s, but the vacuum degree is higher than -25 kPa. At this time, the vacuum assist performance has been greatly affected. The vehicle control unit VCU controls the vehicle to perform speed limit processing. The enabling prerequisite condition for this fault diagnosis is that there is no abnormal fault in the signal voltage of the vacuum pump pressure sensor.

[0059] The present invention has been described exemplarily in combination with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above-mentioned manner. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention; or without improvement, the above-mentioned concept and technical solution of the present invention are directly applied to other occasions, all are within the protection scope of the present invention.

Claims

1. A method for handling a vacuum boost system fault, characterized in that: The specific steps include: Step S1, according to the functional module classification, fault monitoring is also set into three categories, namely, fault monitoring of the braking intention detection perception module, fault monitoring of the environment and execution unit perception module, and fault monitoring of the vacuum control module, so that when any fault occurs, a targeted response can be carried out; Step S2: For the failure of the braking intention detection sensing module, which directly affects the perception and decision-making of the braking energy recovery control, targeted processing is required according to the severity of each failure after it occurs; Step S3, for the environment and execution unit sensing module failure, which directly affects the determination of the vacuum pressure of the vacuum pump, and further affects the enabling control of the vacuum pump; Step S4, for vacuum failure, which directly affects the vacuum boost performance, insufficient vacuum will lead to insufficient brake boost, affecting the force of the driver's brake pedal during braking, which may cause insufficient depression of the brake pedal and thus affect the braking force, resulting in a braking safety risk; Step S5, for enabling control of the vacuum pump, when the environment and the execution unit sensing module fails or a vacuum failure occurs, in order to ensure the braking performance to the greatest extent, the vacuum pump works intermittently when the driver has no intention to brake, and keeps working continuously when the driver has the intention to brake; Step S6, when the vacuum failure in step S4 occurs, the vacuum boost system has clearly failed to provide vacuum boost normally. The processing method in step S5 can ensure that the vacuum pump can work at its maximum capacity, but uncertain factors such as the state of mechanical components such as pipelines may cause the system to still be unable to provide normal and sufficient vacuum boost. In this case, the braking intensity r of the electric brake is dynamically adjusted by identifying the difference err between the vacuum pressure and the normal set threshold. At the same time, combined with the opening t obtained by the brake angle sensor, the lack of mechanical braking force is dynamically compensated from the electric braking angle, and the braking force compensation table is set. The electric brake intensity correction coefficient r is output by looking up the table through the difference err and the vehicle speed v. The overall change trend of the electric brake intensity correction coefficient r is that when the difference err is larger and the vehicle speed v is larger, the electric brake intensity correction coefficient r is larger. At the same time, considering that after the electric brake is increased, the uneven distribution of the braking force of the front and rear wheels may cause the rear wheel to drift, the vehicle controller VCU needs to monitor the slip rate between the front and rear wheels in real time. When the slip rate is large, the electric brake needs to be controlled to exit. When the slip rate drops to within the normal range, the electric brake will intervene again. The electric brake torque under the fault state is calculated based on the basic energy recovery map, the electric brake intensity correction coefficient r and the brake angle sensor opening t.

2. A vacuum boost system fault handling method according to claim 1, characterized in that: The specific processing method in step S2 is as follows: Step S2.1, if the brake pedal angle sensor is short-circuited to the power supply or short-circuited to the ground, the fault is reported by debounce, and when one path fails, the other path is trusted, giving full play to the advantages of dual-path redundancy design to ensure the normal function of brake opening detection; Step S2.2, if a brake pedal switch signal rationality fault occurs, that is, when the brake openings are both greater than the threshold and the brake switch is not pressed, or when the brake openings are both less than the threshold and the brake switch is pressed, it is considered that a brake pedal switch signal rationality fault occurs, and the judgment of the brake switch is canceled, and the brake angle sensor is used to judge the driver's braking operation to control the drive and brake energy recovery; Step S2.3: If a reasonable fault of the brake pedal angle sensor occurs, that is, twice the signal voltage of the first channel minus the signal voltage of the second channel is greater than the threshold, it is considered that a reasonable fault of the brake pedal angle sensor has occurred, and the two brake signals are processed to be smaller to prevent the superposition of excessive braking energy recovery intensity from causing danger; Step S2.4, if a rationality failure of the brake pedal angle sensor 1 or a rationality failure of the brake pedal angle sensor 2 occurs, that is, when the brake switch and the other brake signal have the same change trend, but the signal of this channel is in the opposite state, the other channel is processed to give full play to the advantages of the dual-channel redundant design and ensure the normal function of the brake opening detection function.

3. A vacuum boost system fault handling method according to claim 2, characterized in that: When two or more faults in steps 2.1 to 2.4 are reported simultaneously, since the braking intention cannot be detected, 0 power processing is performed.

4. A vacuum boost system fault handling method according to claim 1, characterized in that: The specific processing method in step S3 is as follows: Step S3.1, if an abnormal voltage fault occurs in the ambient pressure sensor signal, the vehicle controller VCU controls the vehicle to limit the speed to prevent the abnormal ambient pressure detection from causing inaccurate judgment of the vacuum pressure threshold, thereby affecting the vacuum boost and then the braking function; the enabling prerequisite for this fault diagnosis is that there is no power supply, the 5V power supply is abnormal, and the low-voltage power supply of the vehicle is normal; Step S3.2, if the vacuum pump pressure sensor signal voltage is abnormal, the vehicle controller VCU controls the vehicle to limit the speed to prevent the vacuum pump pressure detection abnormality from directly affecting the vacuum pump enable and shutdown threshold judgment. The prerequisite for this fault diagnosis is that there is no abnormal 5V power supply failure of the brake vacuum pressure sensor and the low-voltage power supply of the vehicle is normal; Step S3.3, the vacuum pump enable signal is short-power (control) or short-ground or open-circuit fault. Since the vacuum pump enable control is a low effective output, a short-power fault will cause the vacuum pump to fail to engage, that is, the vacuum pump cannot work. In addition, since short-ground and open-circuit faults cannot be detected separately, in order to avoid misjudgment, they are uniformly treated as vacuum pump failures, and limp handling is required after the fault is reported; Step S3.4, if an abnormal 5V power failure of the vacuum pressure sensor occurs, the failure will affect the monitoring of the vacuum pressure. The vehicle controller VCU will send a brake system fault to the instrument through the bus. After receiving the signal, the brake system fault light will be turned on to remind the driver that maintenance is required.

5. A vacuum boost system fault handling method according to claim 4, characterized in that: When two or more faults are reported simultaneously in steps S3.1 to S3.4, limp home processing is performed.

6. A vacuum boost system fault handling method according to claim 1, characterized in that: The specific processing method in step S4 is: Step S4.1, vacuum pump leakage fault, when the brake switch is not closed, the vacuum pump is not enabled to output, and the vacuum degree reduction rate is greater than 3kPa / s, the fault is reported. At this time, the vacuum boost performance has been greatly affected, and the vehicle controller VCU controls the vehicle to limit the speed. The enabling prerequisite for this fault diagnosis is that there is no abnormal voltage fault of the vacuum pump pressure sensor signal; Step S4.2, vacuum pump overtime failure. When the brake switch is not closed and the vacuum pump is continuously enabled for more than 30 seconds, the vehicle controller VCU controls the vehicle to perform a slight speed limit because the vacuum degree itself meets the braking performance. The enabling prerequisite for this fault diagnosis is that there is no abnormal voltage fault of the vacuum pump pressure sensor signal and no short power (relay control) fault of the vacuum pump enable signal. Step S4.3, vacuum pump low vacuum failure, the vacuum pump is continuously enabled for more than 5s, but the vacuum degree is higher than -25kPa. At this time, the vacuum assist performance has been greatly affected, and the vehicle controller VCU controls the vehicle to limit the speed. The enabling prerequisite for this fault diagnosis is that there is no abnormal vacuum pump pressure sensor signal voltage failure.

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