Fault diagnosis and control method for vacuum boosting system of new energy automobile

Abstract

The invention discloses a fault diagnosis and control method for a vacuum boosting system of a new energy automobile, and belongs to the field of new energy automobiles. The method comprises the following steps: acquiring the vacuum degree of a current vacuum tank through a vacuum tank pressure sensor; the current external environment atmospheric pressure is obtained through an external atmospheric pressure sensor, and opening and closing threshold values of the vacuum pump under the two conditions of the plain and the plateau are formulated according to the current external environment atmospheric pressure; starting fault diagnosis of the vacuum boosting system; and controlling the vacuum pump to enter a corresponding working mode according to a fault diagnosis result. The fault diagnosis of the vacuum boosting system is realized, the regional influence is overcome, the control of the vacuum pump is realized, and the driving feeling and the driving safety are improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy vehicles, and in particular, relates to a fault diagnosis and control method for a vacuum booster system of a new energy vehicle. Background Art

[0002] With the advancement of technological change, new energy vehicles have developed rapidly in recent years, and traditional fuel vehicles have been gradually replaced by new energy vehicles. The brake assist of traditional fuel vehicles is achieved by providing negative pressure to a chamber of the vacuum booster through the work of the engine. However, new energy vehicles (pure electric vehicles, hybrid vehicles); pure electric vehicles do not have engines, and hybrid vehicles do not start the engine in pure electric mode, so the vacuum boost brake system of traditional vehicles cannot be directly applied to new energy vehicles. To achieve brake assist, it is necessary to add a vacuum pump to replace the engine to provide negative pressure for a chamber of the vacuum booster.

[0003] At present, the control of the vacuum pump is simply to control the start and stop of the vacuum pump according to the pressure value of the vacuum booster. Controlling the working state of the vacuum pump by a single pressure threshold cannot meet the braking needs under different atmospheric pressure conditions in plains and plateaus, affecting the driving comfort of the driver and posing potential braking safety hazards. At the same time, the lack of diagnosis of the vacuum boost system often causes the electronic vacuum pump to be started frequently and kept in working state for a long time, affecting the service life of the electronic vacuum pump and the safety of the vehicle. In view of this situation, the present application proposes a fault diagnosis and control method for the vacuum boost system of new energy vehicles. Summary of the invention

[0004] The present invention aims to overcome the deficiencies of the prior art and proposes a fault diagnosis and control method for a vacuum power-assisting system of a new energy vehicle to achieve the following objectives: to realize the fault diagnosis of the vacuum power-assisting system and to overcome the influence of geographical conditions to realize the control of the vacuum pump, thereby improving the driving experience and driving safety.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a fault diagnosis and control method of a vacuum booster system of a new energy vehicle, the method comprising:

[0006] Step S1, obtaining the current vacuum degree of the vacuum tank through the vacuum tank pressure sensor;

[0007] Step S2, obtaining the current external atmospheric pressure through an external atmospheric pressure sensor, and using this to formulate the opening and closing thresholds of the vacuum pump in both plain and plateau conditions;

[0008] Step S3, vacuum boost system start fault diagnosis;

[0009] Step S4: According to the fault diagnosis result of step S3, the control of the vacuum pump enters a corresponding working mode, including a sensor fault working mode, a minor fault working mode, a major fault working mode, and a normal working mode.

[0010] Preferably, in step S2, according to the current external environment atmospheric pressure P 外界 Determine whether the current area is a plain or a plateau. 外界 When the atmospheric pressure is less than the first threshold, the current area is determined to be a plateau; when P 外界 When it is greater than or equal to the first atmospheric pressure threshold, it is determined that the current area is a plain.

[0011] Preferably, the vacuum pump on and off thresholds in a plain environment are as follows:

[0012] When the current vehicle speed is less than the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.45*P 外界 , the vacuum pump shut-off threshold is P Vam _OFF=0.24*P 外界 ;

[0013] When the current vehicle speed is greater than or equal to the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.3*P 外界 , the vacuum pump shut-off threshold is P Vam _OFF=0.24*P 外界 .

[0014] Preferably, in a plateau environment, when P 外界 When it is greater than or equal to the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=26KPa, vacuum pump shut-off threshold is P Vam _OFF=22KPa; when P 外界 When the pressure is less than the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=24KPa, vacuum pump shut-off threshold is P Vam _OFF=15KPa, wherein the second atmospheric pressure threshold is less than the first atmospheric pressure threshold.

[0015] Preferably, in step S3, the fault diagnosis includes fault diagnosis of a vacuum tank pressure sensor and an external atmospheric pressure sensor, wherein whether the sensor is faulty is determined by detecting the sensor voltage;

[0016] Specifically, during the sensor fault diagnosis, if the sensor voltage exceeds the operating voltage range and this situation lasts for a preset number of detection cycles, the sensor fault is determined and a sensor fault signal is generated, wherein a counting mechanism is enabled, that is, the value of the counter increases according to a first preset value in each detection cycle; after the sensor fault signal is generated, if the sensor voltage recovers to the operating voltage range during the sensor fault diagnosis and lasts for multiple detection cycles, then in each detection cycle, the value of the counter decreases according to a second preset value until the value of the counter is cleared, and the sensor fault signal is eliminated.

[0017] Preferably, the fault diagnosis includes air extraction fault diagnosis, wherein: when the vacuum pump is enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P1 is latched after a first preset time, and then after a second preset time, the current vacuum tank vacuum degree P2 is latched, if the difference between P2-P1 is greater than the first air extraction fault threshold and less than the second air extraction fault threshold, it indicates a minor fault; if the difference between P2-P1 is less than the second inflation fault threshold, it indicates a serious fault; wherein, the first inflation fault threshold is less than the second inflation fault threshold.

[0018] Preferably, the fault diagnosis includes air leakage fault diagnosis, wherein: when the vacuum pump is not enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P3 is latched after a third preset time, and then after a fourth preset time, the current vacuum tank vacuum degree P4 is latched, if the difference between P3-P4 is greater than the first air leakage fault threshold, it indicates a serious fault; if the difference between P3-P4 is less than the first air leakage fault threshold and greater than the second air leakage fault threshold, it indicates a minor fault; wherein, the first air leakage fault threshold is greater than the second air leakage fault threshold.

[0019] Preferably, in step S4, when the vacuum boost system has no faults, the vacuum pump enters a normal working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start-up threshold, the vacuum pump is turned on; if the vacuum degree VACb of the current vacuum tank is less than the current vacuum pump shut-down threshold, the vacuum pump is turned off;

[0020] When a sensor failure occurs in the vacuum booster system, the vacuum pump enters the sensor failure working mode. At this time, the rising edge of the brake pedal signal is taken as the trigger signal, that is, when the brake pedal is stepped on, the vacuum pump stops after working for the first duration; after stopping, the vacuum pump does not respond to the received trigger signal within the preset protection time;

[0021] When a minor fault occurs in the vacuum boost system, the vacuum pump enters a minor fault working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start-up threshold, the vacuum pump is turned on, and the vacuum pump is turned off after working for the second duration;

[0022] When a serious fault occurs in the vacuum boosting system, the vacuum pump enters a serious fault working mode. At this time, the vacuum pump starts to work in a cycle, that is, the vacuum pump is turned on and works for a third duration, then stops working, stops for a fourth duration, and then turns on the vacuum pump again, and repeats this cycle.

[0023] Preferably, the vacuum assist system is provided with a forced protection mechanism, namely: the maximum working time of the vacuum pump is set to the fifth duration, after which the vacuum pump stops working immediately and returns to the state before stopping after the sixth duration.

[0024] Preferably, in step S3, the vacuum boost system synchronously sends the result of the fault diagnosis to the vehicle instrument to remind the user.

[0025] The technical effect of the present invention is as follows: the present invention formulates a control strategy suitable for plains and plateaus according to the atmospheric pressure value, the vacuum degree of the vacuum tank and the working characteristics of the vacuum pump, and the present invention has a complete fault diagnosis system. When there is a fault in the vacuum boost system, the vacuum pump enters the corresponding fault working mode to meet the driver's braking needs to the greatest extent. At the same time, it protects the vacuum pump from failure caused by frequent starting, long-term operation and other working conditions to a great extent, greatly improving braking safety and driving comfort for the driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A structural diagram of a vacuum booster system according to an embodiment of the present invention;

[0027] Figure 2 A vacuum pump control flow chart of an embodiment of the present invention;

[0028] Figure 3 This is a flow chart of the vacuum pump forced protection mechanism method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following is a further detailed description of the specific implementation of the present invention through the description of the embodiments with reference to the accompanying drawings, with the purpose of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation. It should be noted that the words "first", "second" and the like described in this application are only for the convenience of describing the technical solution to distinguish different components, modules, etc., and are not used to limit this application. In order to make the technical solution of the present invention clearer, the present invention is explained through the following embodiments.

[0030] The structure of a vacuum booster system of this embodiment is as follows Figure 1 As shown, the vacuum boost system includes a vacuum tank, a vacuum tank pressure sensor, a vacuum pump, a vacuum booster, a brake pedal, a vehicle controller VCU, and an external atmospheric pressure sensor, wherein the vacuum tank pressure sensor, vacuum pump, brake pedal, and external atmospheric pressure sensor are electrically connected to the vehicle controller VCU respectively; the vacuum booster converts the vacuum pressure into thrust to assist the brake pedal in braking; the vacuum tank is connected to the vacuum tank pressure sensor, vacuum pump, and vacuum booster respectively by air pipes. The vehicle controller VCU is used for the collection and analysis of sensor data, and the fault diagnosis and control of the vacuum boost system.

[0031] Based on the above vacuum boost system, this embodiment proposes a fault diagnosis and control method for the vacuum boost system of a new energy vehicle, the method comprising:

[0032] Step S1, obtaining the current vacuum degree of the vacuum tank through the vacuum tank pressure sensor;

[0033] Step S2, obtaining the current external atmospheric pressure through an external atmospheric pressure sensor, and using this to formulate the opening and closing thresholds of the vacuum pump in both plain and plateau conditions;

[0034] Step S3, vacuum boost system start fault diagnosis;

[0035] Step S4: According to the fault diagnosis result of step S3, the control of the vacuum pump enters a corresponding working mode, including a sensor fault working mode, a minor fault working mode, a major fault working mode, and a normal working mode.

[0036] Specifically, in step S1, the vehicle controller VCU converts the internal air pressure of the vacuum tank into a voltage signal for collection through the vacuum tank pressure sensor. At the same time, in order to reduce signal noise, the voltage signal can be filtered by a first-order low-pass filter; according to the voltage signal, the vacuum degree of the vacuum tank can be calculated by referring to the pressure signal characteristic curve of the pressure sensor under different working voltages. Taking the pressure signal characteristic curve of the pressure sensor under a working voltage of 5V as an example, the calculation formula of the vacuum degree is expressed as:

[0037]

[0038] Wherein, Vout represents the voltage signal output by the pressure sensor; VACb represents the vacuum degree.

[0039] In step S2, the vehicle controller converts the external atmospheric pressure into a voltage signal through the external atmospheric pressure sensor for collection, and calculates the external atmospheric pressure P 外界Considering that different regions have different atmospheric pressures, the corresponding braking requirements are also different, especially in plateaus and plains, so it is necessary to formulate control strategies for plateaus and plains respectively. First, according to the current external atmospheric pressure P 外界 Determine whether the current vehicle location is a plain or a plateau. 外界 When the atmospheric pressure is less than the first threshold, the current area is determined to be a plateau; when P 外界 When the atmospheric pressure is greater than or equal to the first atmospheric pressure threshold, it is determined that the current area is a plain. The first atmospheric pressure threshold of this embodiment is 84Kpa, which can be adjusted according to actual conditions during implementation.

[0040] In a plain environment, the higher the speed, the higher the braking requirement. Considering the safety braking factor, different vacuum pump on / off thresholds are adopted for different vehicle speeds. The vacuum pump on / off thresholds in a plain environment are as follows:

[0041] When the current vehicle speed is less than the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.45*P 外界 , the vacuum pump shut-off threshold is P Vam _OFF=0.24*P 外界 ; When the current vehicle speed is greater than or equal to the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.3*P 外界 , vacuum pump off

[0042] The closing threshold is P Vam _OFF=0.24*P 外界 The first vehicle speed threshold of this embodiment is 30 km / h.

[0043] In plateau environments, when P 外界 When it is greater than or equal to the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=26KPa, vacuum pump shut-off threshold is P Vam _OFF=22KPa; when P 外界 When the pressure is less than the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=24KPa, vacuum pump shut-off threshold is P Vam _OFF=15KPa, wherein the second atmospheric pressure threshold is less than the first atmospheric pressure threshold. The second atmospheric pressure threshold of this embodiment is 62KPa.

[0044] In step S3, the fault diagnosis of this embodiment includes fault diagnosis of the vacuum tank pressure sensor and the external atmospheric pressure sensor, wherein the vehicle controller determines whether the sensor is faulty by detecting the sensor voltage.

[0045] Specifically, during the sensor fault diagnosis, if the sensor voltage exceeds the working voltage range and the situation lasts for a preset number of detection cycles (150 detection cycles in this embodiment), the sensor fault is determined and a sensor fault signal is generated, wherein the counting mechanism is enabled, that is, the value of the counter increases according to the first preset value (2 in this embodiment) in each detection cycle; after the sensor fault signal is generated, if the sensor voltage returns to the working voltage range during the sensor fault diagnosis and lasts for multiple detection cycles, then in each detection cycle, the value of the counter decreases according to the second preset value (1 in this embodiment) until the value of the counter is cleared, and the sensor fault signal is eliminated. The use of the counting mechanism can effectively avoid false fault reports.

[0046] The fault diagnosis of this embodiment also includes air extraction fault diagnosis and air leakage fault diagnosis, wherein:

[0047] Exhaust fault diagnosis: When the vacuum pump is enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P1 is latched after a first preset time (1s in this embodiment), and then after a second preset time (3s in this embodiment), the current vacuum tank vacuum degree P2 is latched. If the difference between P2-P1 is greater than the first exhaust fault threshold and less than the second exhaust fault threshold, it indicates a minor fault; if the difference between P2-P1 is less than the second inflation fault threshold, it indicates a serious fault; wherein, the first inflation fault threshold is less than the second inflation fault threshold, and the first inflation fault threshold and the second inflation fault threshold can be obtained in advance by looking up the table based on the exhaust characteristic table of the vacuum pump.

[0048] Air leakage fault diagnosis: When the vacuum pump is not enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P3 is latched after the third preset time (5s in this embodiment), and then after the fourth preset time (3s in this embodiment), the current vacuum tank vacuum degree P4 is latched. If the difference between P3-P4 is greater than the first air leakage fault threshold (5KPa in this embodiment), it indicates a serious fault; if the difference between P3-P4 is less than the first air leakage fault threshold and greater than the second air leakage fault threshold (2KPa in this embodiment), it indicates a minor fault; wherein, the first air leakage fault threshold is greater than the second air leakage fault threshold.

[0049] After the vehicle controller VCU diagnoses the result, it is sent to the instrument through CAN communication. The instrument displays the fault icon on the interface and can also issue a warning sound according to the fault level (minor, serious, sensor failure), so as to remind the driver in time and make the correct treatment to reduce the occurrence of accidents.

[0050] In step S4 of this embodiment, the control of the vacuum pump is divided into a normal working mode, a minor fault working mode, a serious fault working mode, and a sensor fault working mode. Figure 2 As shown, the vehicle controller will enter the corresponding working mode according to the failure result of the vacuum booster system.

[0051] Specifically, first determine whether the sensor of the vacuum boost system is faulty. When a sensor fault occurs in the vacuum boost system, the vacuum pump enters the sensor fault working mode. At this time, the rising edge of the brake pedal signal is taken as the trigger signal, that is, when the brake pedal is stepped on, the vacuum pump stops after working for a first duration (10s in this embodiment); after stopping, the vacuum pump does not respond to the received trigger signal within a preset protection time (3s in this embodiment), thereby protecting the vacuum pump and preventing faults caused by frequent startup of the vacuum pump.

[0052] Then, determine whether the vacuum boost system has other faults besides the sensor, such as air extraction fault and air leakage fault. When the vacuum boost system has no faults, the vacuum pump enters the normal working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start threshold, the vacuum pump is turned on; if the vacuum degree VACb of the current vacuum tank is less than the current vacuum pump shutdown threshold, the vacuum pump is turned off.

[0053] Secondly, if there are other faults in the vacuum boost system except for the sensor, it is determined whether the fault is a minor fault. When a minor fault occurs in the vacuum boost system, the vacuum pump enters a minor fault working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start-up threshold, the vacuum pump is turned on and turned off after the second working duration (20s in this embodiment);

[0054] Finally, it is determined whether the fault is a serious fault. When a serious fault occurs in the vacuum boost system, the vacuum pump enters a serious fault working mode, at which time the vacuum pump starts to work in a cycle, that is, the vacuum pump is turned on and works for a third duration (10 seconds in this embodiment) and then stops working, stops for a fourth duration (5 seconds in this embodiment) and then restarts the vacuum pump, and the cycle repeats.

[0055] This embodiment also provides mandatory protection for the vacuum pump based on the working characteristics and design features of the vacuum pump to prevent the vacuum pump from working continuously due to a malfunction of the vacuum booster system or a pipeline problem. Figure 3 As shown, the vacuum assist system is provided with a forced protection mechanism, namely: after the vacuum pump is enabled, the maximum working time of the vacuum pump is set to the fifth duration (20s in this embodiment), and the timer T1 is used for timing. After the time is up, the vacuum pump stops working immediately and returns to the state of the vacuum pump before stopping after the sixth duration (5s in this embodiment). The stop interval time is counted by the timer T2.

[0056] The present invention has formulated a control strategy suitable for plains and plateaus based on the atmospheric pressure value, the vacuum degree of the vacuum tank and the working characteristics of the vacuum pump. At the same time, the present invention has a complete fault diagnosis system. When there is a fault in the vacuum boost system, the vacuum pump enters the corresponding fault working mode to meet the driver's braking needs to the greatest extent. At the same time, it protects the vacuum pump from failure caused by frequent starting, long-term operation and other working conditions to a great extent, greatly improving braking safety and driving comfort for the driver.

[0057] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A fault diagnosis and control method for a vacuum booster system of a new energy vehicle, characterized in that: The method comprises: Step S1, obtaining the vacuum degree of the current vacuum tank through the vacuum tank pressure sensor; Step S2, obtaining the current external atmospheric pressure through an external atmospheric pressure sensor, and using this to formulate the opening and closing thresholds of the vacuum pump in both plain and plateau conditions; Step S3, vacuum boost system start fault diagnosis; Step S4: According to the fault diagnosis result of step S3, the control of the vacuum pump enters a corresponding working mode, including a sensor fault working mode, a minor fault working mode, a major fault working mode, and a normal working mode.

2. A fault diagnosis and control method for a vacuum booster system of a new energy vehicle according to claim 1, characterized in that: In step S2, according to the current external ambient atmospheric pressure P 外界 Determine whether the current area is a plain or a plateau. 外界 When the atmospheric pressure is less than the first threshold, the current area is determined to be a plateau; when P 外界 When it is greater than or equal to the first atmospheric pressure threshold, it is determined that the current area is a plain.

3. A fault diagnosis and control method for a vacuum booster system of a new energy vehicle according to claim 2, characterized in that: The vacuum pump on and off thresholds in plain environment are as follows: When the current vehicle speed is less than the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.45*P 外界 , the vacuum pump shut-off threshold is P Vam _OFF=0.24*P 外界 ; When the current vehicle speed is greater than or equal to the first vehicle speed threshold, the vacuum pump opening threshold is P Vam _ON=0.3*P 外界 , the vacuum pump shut-off threshold is P Vam _OFF=0.24*P 外界 .

4. A fault diagnosis and control method for a vacuum booster system of a new energy vehicle according to claim 2 or 3, characterized in that: In plateau environments, when P 外界 When it is greater than or equal to the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=26KPa, vacuum pump shut-off threshold is P Vam _OFF=22KPa; when P 外界 When the pressure is less than the second atmospheric pressure threshold, the vacuum pump opening threshold is P Vam _ON=24KPa, vacuum pump shut-off threshold is P Vam _OFF=15KPa, wherein the second atmospheric pressure threshold is less than the first atmospheric pressure threshold.

5. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: In step S3, the fault diagnosis includes fault diagnosis of the vacuum tank pressure sensor and the external atmospheric pressure sensor, wherein whether the sensor is faulty is determined by detecting the sensor voltage; Specifically, during the sensor fault diagnosis, if the sensor voltage exceeds the operating voltage range and this situation lasts for a preset number of detection cycles, the sensor fault is determined and a sensor fault signal is generated, wherein a counting mechanism is enabled, that is, the value of the counter increases according to a first preset value in each detection cycle; after the sensor fault signal is generated, if the sensor voltage recovers to the operating voltage range during the sensor fault diagnosis and lasts for multiple detection cycles, then in each detection cycle, the value of the counter decreases according to a second preset value until the value of the counter is cleared, and the sensor fault signal is eliminated.

6. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: The fault diagnosis includes air extraction fault diagnosis, in which: when the vacuum pump is enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P1 is latched after a first preset time, and then after a second preset time, the current vacuum tank vacuum degree P2 is latched, if the difference between P2-P1 is greater than the first air extraction fault threshold and less than the second air extraction fault threshold, it indicates a minor fault; if the difference between P2-P1 is less than the second inflation fault threshold, it indicates a serious fault; wherein, the first inflation fault threshold is less than the second inflation fault threshold.

7. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: The fault diagnosis includes air leakage fault diagnosis, in which: when the vacuum pump is not enabled and the brake pedal is not pressed, both conditions are met at the same time, the current vacuum tank vacuum degree P3 is latched after a third preset time, and then after a fourth preset time, the current vacuum tank vacuum degree P4 is latched. If the difference between P3-P4 is greater than the first air leakage fault threshold, it indicates a serious fault; if the difference between P3-P4 is less than the first air leakage fault threshold and greater than the second air leakage fault threshold, it indicates a minor fault; wherein, the first air leakage fault threshold is greater than the second air leakage fault threshold.

8. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: In step S4, when the vacuum boost system has no faults, the vacuum pump enters a normal working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start threshold, the vacuum pump is turned on; if the vacuum degree VACb of the current vacuum tank is less than the current vacuum pump shut-off threshold, the vacuum pump is turned off; When a sensor failure occurs in the vacuum booster system, the vacuum pump enters the sensor failure working mode. At this time, the rising edge of the brake pedal signal is taken as the trigger signal, that is, when the brake pedal is stepped on, the vacuum pump stops after working for the first duration; after stopping, the vacuum pump does not respond to the received trigger signal within the preset protection time; When a minor fault occurs in the vacuum boost system, the vacuum pump enters a minor fault working mode. At this time, if the vacuum degree VACb of the current vacuum tank is greater than the current vacuum pump start-up threshold, the vacuum pump is turned on, and the vacuum pump is turned off after working for the second duration; When a serious fault occurs in the vacuum boosting system, the vacuum pump enters a serious fault working mode. At this time, the vacuum pump starts to work in a cycle, that is, the vacuum pump is turned on and works for a third duration, then stops working, stops for a fourth duration, and then turns on the vacuum pump again, and repeats this cycle.

9. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: The vacuum assist system is provided with a mandatory protection mechanism, namely: the maximum working time of the vacuum pump is set to the fifth duration, after which the vacuum pump stops working immediately and returns to the state before the vacuum pump stops after the sixth duration.

10. The fault diagnosis and control method of the vacuum booster system of a new energy vehicle according to claim 1, characterized in that: In step S3, the vacuum boost system synchronously sends the result of the fault diagnosis to the vehicle instrument to remind the user.

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