Liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method

Abstract

A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method comprises two parts, one part is fault code design, the other part is fault code application control, a 32-bit variable fault code is designed, a high byte is designed as alarm sign information, and the alarm sign information comprises a total alarm sign and a historical alarm sign. The historical alarm sign records nearly six alarm conditions, and whether the total alarm sign is effective or not is judged according to different iteration judgment modes; the second high byte is alarm category information, the alarm category information comprises fault large class information and fault small class information, the fault large class indicates that a certain fault has different progressive branches, and the fault small class indicates that a certain judgment branch has different progressive judgment branches; the two lower bytes are specific fault information which indicates the specific condition judgment condition in a certain judgment node.

Description

Technical Field

[0001] The invention relates to a liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method, belonging to the field of aerospace engine fault diagnosis. Background Art

[0002] Liquid hydrogen and liquid oxygen engines use liquid hydrogen and liquid oxygen as propellants and have the functions of engine status monitoring and fault diagnosis. The engine status monitoring and fault diagnosis system uses sensors to obtain engine operating status data and uses some specific fault diagnosis methods to determine whether the engine itself and its accessories have faults.

[0003] Liquid hydrogen and liquid oxygen engines have multiple operating processes and complex operating mechanisms. The design of fault diagnosis methods needs to consider the following aspects:

[0004] 1. Different operation stages: The judgment basis and judgment method vary at different engine operation stages;

[0005] 2. Reliability of acquisition equipment: If a certain acquisition equipment fails and the parameters are missing, it is necessary to consider using the remaining valid parameters for judgment;

[0006] 3. Progressive failure mode: For a specific operation stage, when the result of a certain progressive judgment branch is not abnormal, other failure modes need to be considered, and subsequent progressive judgment branches still need to be judged;

[0007] 4. Fault diagnosis false alarm rate: In fault judgment during a certain operation phase, certain reliability measures need to be taken to reduce the fault diagnosis false alarm rate.

[0008] The design of the fault diagnosis process of liquid hydrogen and liquid oxygen engines is complex, including both progressive branches and progressive judgment branches, and the specific judgment conditions under each progressive judgment branch are different. For conventional design methods, each judgment condition corresponds to a variable and executes different judgment logics. In this way, a large number of variables and logical judgment branches will be generated. In order to reduce the false alarm rate, it is often necessary to record historical judgment results and take reliability measures. Designing a historical result array for each variable will cause risks such as complicated program design, low code coupling, and excessive memory usage. At the same time, the real-time requirements of engine communication are high, and bandwidth resources are very precious. It is not allowed to design too much data in the protocol frame. Therefore, conventional design methods are difficult to apply to increasingly complex fault diagnosis systems. Summary of the invention

[0009] The technical problem solved by the present invention is: in view of the problem that the conventional design methods existing in the current prior art are difficult to apply to increasingly complex fault diagnosis information, a liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method is proposed.

[0010] The present invention solves the above technical problems by the following technical solutions:

[0011] A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method, comprising:

[0012] Design fault codes, including alarm sign information, alarm category information and alarm condition information;

[0013] Perform fault code initialization processing according to fault code design requirements;

[0014] Use the initialization processed fault code to diagnose the fault condition of the current control cycle;

[0015] Assigning a fault condition result to the fault code after initialization processing according to the fault condition diagnosis result;

[0016] According to the fault condition diagnosis result, the fault code after the fault condition result is assigned a value is updated with a general alarm flag;

[0017] The fault code updated by the general alarm flag is used as the fault detection result of the current control cycle.

[0018] The alarm mark information includes a total alarm mark and a historical alarm mark, and the design method is as follows:

[0019] The 31st to 30th bits of the preset fault code represent the general alarm flag, which is represented by a 2-bit code, with 00b indicating no fault, 11b indicating a fault, and 01b and 10b indicating invalid data;

[0020] The 29th to 24th bits of the preset fault code represent the historical alarm flag, which is represented by a 6-bit code and is used to record the fault code alarm conditions of 6 cycles. The 24th bit represents the alarm condition of this cycle. 0b indicates no fault, and 1b indicates a fault.

[0021] The alarm category information includes major fault category information and minor fault category information, and the design method is as follows:

[0022] The 23~x bits of the preset fault code represent the major fault category information, which is used to select n fault diagnosis branch processes according to the alarm condition information;

[0023] The (x-1) to 16 bits of the preset fault code represent fault sub-category information, which is used to characterize the progressive branch process under the fault diagnosis branch process according to the entered fault diagnosis branch process;

[0024] 23>x>16.

[0025] During the control cycle of each fault code, the alarm category information only enters one fault diagnosis branch process;

[0026] Under any fault diagnosis branch process, there are m progressive branch processes. When the previous progressive branch process does not meet the fault code design requirements, the next progressive branch process is entered.

[0027] The alarm condition information is that under any progressive branch process, there are k (k<16) fault conditions, and each fault condition corresponds to one of the fault codes 15 to 0.

[0028] The fault code initialization process is to set the fault code 23~0 to 0b.

[0029] The method of assigning the fault condition result is:

[0030] The fault condition diagnosis results under each progressive branch process are assigned to the corresponding position of the fault code, with 0b indicating no fault and 1b indicating a fault; if any fault conditions exist under any progressive branch process in the current control cycle, the fault code position corresponding to each fault condition position is set to 1b.

[0031] The fault code design requirements include iteration rules, iteration times, fault diagnosis branch process information, progressive branch process information, and historical alarm flags. The method for updating the fault code after the fault condition result is assigned is:

[0032] First, update the fault diagnosis branch process information and the progressive branch process information;

[0033] If the alarm condition information of the current fault code does not meet the fault code design requirements and there is a next progressive branch process, then exit the current update process; if the fault condition diagnosis result does not meet the fault condition diagnosis result requirements and there is no next progressive branch process, then update the historical alarm information;

[0034] If the alarm condition information of the current fault code meets the fault code design requirements, determine whether to update the general alarm flag according to the iteration rules and the number of iterations;

[0035] After updating the general alarm flag, the fault code of the current control cycle is updated.

[0036] The method for updating the historical alarm information is: shifting the historical alarm information of the fault code of the current control cycle to the left, and setting the position of the fault code 24 to 0b.

[0037] The iteration rule is: use the historical alarm information within 6 adjacent control cycles to make a judgment. If the historical alarm information of consecutive iteration number cycles is 1b, the total alarm flag is updated to 11b; if in consecutive iteration number cycles, the historical alarm information of a total of iteration number cycles is 1b, the total alarm flag is updated to 11b; wherein the number of iterations is ≤6 times.

[0038] The advantages of the present invention compared with the prior art are:

[0039] (1) The present invention provides a liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method, which can effectively improve the application effect of complex fault diagnosis system methods, more effectively ensure the safety of engines and test facilities, effectively improve existing methods, reduce the number of diagnostic variables and the complexity of diagnostic logic design, and simplify the fault diagnosis system design;

[0040] (2) The present invention achieves diagnostic result reliability at the lowest cost by representing diagnostic information at the maximum density, and transmits as many diagnostic results as possible without sacrificing bandwidth, which is helpful for real-time feedback of engine test results and post-test analysis process;

[0041] (3) The present invention adopts the component-based concept in the design process, and considers the universality of fault diagnosis fault code design and application as much as possible, which can be extended to the design and application of fault diagnosis systems for multiple types of engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A brief flow chart of fault judgment of a liquid hydrogen and liquid oxygen engine provided by the present invention;

[0043] Figure 2 This is a structural diagram of the fault diagnosis fault code provided by the present invention. DETAILED DESCRIPTION

[0044] A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method includes two parts, one part is fault code design, the other part is fault code application control, a 32-bit variable fault code is designed, the high byte is designed as alarm mark information, the alarm mark information includes a total alarm mark and a historical alarm mark, the historical alarm mark records the alarm conditions of the past 6 times, and judges whether the total alarm mark is valid according to different iterative judgment methods; the second highest byte is alarm category information, the alarm category information includes fault major category information and fault minor category information, the fault major category indicates that a certain fault has different progressive branches, and the fault minor category indicates that a certain judgment branch has different progressive judgment branches; the lower two bytes are specific fault information, indicating the specific condition judgment situation in a certain judgment node.

[0045] The design of the fault diagnosis process of liquid hydrogen and liquid oxygen engines is complex, including both progressive branches and progressive judgment branches, and the specific judgment conditions under each progressive judgment branch are different. Therefore, it is necessary to explore a fault code design method that can accommodate as much diagnostic information as possible and occupy as little bandwidth resources as possible, which is an important supplement to the current field of engine fault diagnosis.

[0046] like Figure 1 As shown, the design and application method of fault diagnosis fault code for liquid hydrogen and liquid oxygen engine includes the following steps:

[0047] Design fault codes, including alarm sign information, alarm category information and alarm condition information;

[0048] Perform fault code initialization processing according to fault code design requirements;

[0049] Use the initialization processed fault code to diagnose the fault condition of the current control cycle;

[0050] Assigning a fault condition result to the fault code after initialization processing according to the fault condition diagnosis result;

[0051] According to the fault condition diagnosis result, the fault code after the fault condition result is assigned a value is updated with a general alarm flag;

[0052] The fault code updated by the general alarm flag is used as the fault detection result of the current control cycle.

[0053] The alarm mark information includes the total alarm mark and the historical alarm mark. The design method is:

[0054] The 31st to 30th bits of the preset fault code represent the general alarm flag, which is represented by a 2-bit code, with 00b indicating no fault, 11b indicating a fault, and 01b and 10b indicating invalid data;

[0055] The 29th to 24th bits of the preset fault code represent the historical alarm flag, which is represented by a 6-bit code and is used to record the fault code alarm conditions of 6 cycles. The 24th bit represents the alarm condition of this cycle. 0b indicates no fault, and 1b indicates a fault.

[0056] The alarm category information includes major fault category information and minor fault category information. The design method is as follows:

[0057] The 23~x bits of the preset fault code represent the major fault category information, which is used to select n fault diagnosis branch processes according to the alarm condition information;

[0058] The (x-1) to 16 bits of the preset fault code represent fault sub-category information, which is used to characterize the progressive branch process under the fault diagnosis branch process according to the entered fault diagnosis branch process;

[0059] 23>x>16.

[0060] During the control cycle of each fault code, the alarm category information only enters one fault diagnosis branch process;

[0061] Under any fault diagnosis branch process, there are m progressive branch processes. When the previous progressive branch process does not meet the fault code design requirements, the next progressive branch process is entered.

[0062] The alarm condition information is that under any progressive branch process, there are k (k<16) fault conditions, and each fault condition corresponds to one of the fault codes 15 to 0.

[0063] The fault code initialization process is to set the fault code 23~0 to 0b.

[0064] The method of assigning the fault condition result is:

[0065] The fault condition diagnosis results under each progressive branch process are assigned to the corresponding position of the fault code, with 0b indicating no fault and 1b indicating a fault; if any fault conditions exist under any progressive branch process in the current control cycle, the fault code position corresponding to each fault condition position is set to 1b.

[0066] The fault code design requirements include iteration rules, iteration times, fault diagnosis branch process information, progressive branch process information, and historical alarm flags. The method for updating the fault code after the fault condition result is assigned is:

[0067] First, update the fault diagnosis branch process information and the progressive branch process information;

[0068] If the alarm condition information of the current fault code does not meet the fault code design requirements and there is a next progressive branch process, then exit the current update process; if the fault condition diagnosis result does not meet the fault condition diagnosis result requirements and there is no next progressive branch process, then update the historical alarm information;

[0069] If the alarm condition information of the current fault code meets the fault code design requirements, determine whether to update the general alarm flag according to the iteration rules and the number of iterations;

[0070] After updating the general alarm flag, the fault code of the current control cycle is updated.

[0071] The method for updating the historical alarm information is: shift the historical alarm information of the fault code of the current control cycle to the left, and set the fault code 24 position to 0b.

[0072] The iteration rule is: use the historical alarm information within 6 adjacent control cycles for judgment. If the historical alarm information of consecutive iteration number cycles is 1b, the total alarm flag is updated to 11b; if in consecutive iteration number cycles, the historical alarm information of a total of iteration number cycles is 1b, the total alarm flag is updated to 11b; among which, the number of iterations is ≤6 times.

[0073] The following is further described in conjunction with the accompanying drawings and preferred embodiments of the specification:

[0074] In the current embodiment, according to the specific requirements of the engine system for the fault diagnosis system, a liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method is proposed. The engine operation status data is obtained by using sensors, and the fault diagnosis system determines whether the engine itself and its accessories are faulty, and feeds back the fault diagnosis results.

[0075] 1. Fault code structure

[0076] like Figure 2 As shown, the fault code is a 32-bit variable. On 32-bit devices represented by ARM A9, it is generally declared as unsigned int (in the code, it is represented as Uint32 through macro definition). Other devices are set according to the address bus width and compiler type. The high byte of the fault code represents the alarm flag information, the second high byte represents the alarm category information, and the low two bytes represent the alarm condition information. They are introduced as follows:

[0077] (1) Alarm sign information

[0078] In the alarm flag information, bits 31-30 represent the total alarm flag, and bits 29-24 represent the historical alarm flag. Figure 1 In the process, updating the alarm flag means updating the general alarm flag and the historical alarm flag. The historical alarm flag has 6 bits in total, which record the alarm conditions of 6 cycles respectively. 24 bits represent the alarm conditions of this cycle. 0b means no fault, and 1b means a fault. According to the historical alarm flag, it is determined whether the general alarm flag is updated in this cycle. If the general alarm flag is valid, it indicates that a diagnostic system alarm (hereinafter referred to as the system alarm) is generated in this cycle, and the engine control system needs to take certain measures to avoid greater losses. The historical alarm flag is designed to improve the reliability of fault diagnosis. It can be used as a basis for judging whether to update the general alarm flag through methods such as "alarm for 3 consecutive cycles" or "alarm for 3 cycles in the next 6 cycles". In general, the importance level of the general alarm flag is higher, and the code distance needs to be increased. This implementation scheme uses 2 bits to represent it. 00b means no fault, 11b means fault, and 01b and 10b mean that the data is invalid.

[0079] (2) Alarm category information

[0080] like Figure 1As shown in the figure, during a certain period of time during the engine ignition process, the fault diagnosis enters the corresponding process. First, it is necessary to determine whether a certain progressive branch is satisfied, and select the branch number as the major fault category information. Under this progressive branch, there are also certain progressive branches. The progressive branches contain specific diagnostic conditions, and the progressive branch numbers are the minor fault category information. These two types of information are necessary for real-time or post-test analysis of the engine hot test. If the diagnostic result of a certain progressive branch meets the fault requirements, the fault flag information is updated. If it does not meet the requirements, enter the next progressive branch. 23 to x bits represent the major fault category information, and (x-1) to 16 bits represent the minor fault category information. In actual application, the number of occupied bits can be flexibly adjusted according to the number of major and minor fault categories. In most cases, x can be set to 20.

[0081] (3) Specific fault condition information

[0082] In the description of the previous section, the diagnosis result of the specific diagnosis condition in the progressive branch is called the specific fault condition information, which is represented by bits 15 to 0. Each bit can represent a fault condition, and a total of 16 fault condition judgment results can be recorded.

[0083] 2. Application steps

[0084] The application of this fault code is mainly divided into three steps: fault code initialization, fault condition result assignment, and fault code update. They are introduced as follows:

[0085] Assume that there are 2 progressive branches when selecting branch 2. Progressive branch 1 contains 8 fault conditions, and at least 3 conditions meet the fault requirements, then progressive branch 1 determines the fault, and the fault code determines the fault in this cycle and enters the next cycle. If no more than 3 conditions, it enters progressive branch 2. Progressive branch 2 has 4 fault conditions, and at least 2 conditions meet the fault requirements, then progressive branch 2 determines the fault, and the fault code determines the fault in this cycle and enters the next cycle. If no more than 2 conditions, the fault code does not determine the fault in this cycle.

[0086] (1) Fault code initialization

[0087] At the beginning of this cycle diagnosis, the fault code needs to be initialized in order to clear the diagnosis results of the previous cycle, including fault category information and fault condition information, to prevent affecting the judgment results of this cycle. The clearing method is to set the fault code 23~0 to 0b. This implementation plan provides a specific code implementation:

[0088] FLAG&=~(1U<<24)–1U;

[0089] (2) Fault condition result assignment

[0090] The fault condition diagnosis result under the progressive branch needs to be assigned to the corresponding position of the fault code, 0b means no fault, 1b means fault. Assuming that the third condition of the progressive branch 3 of the selection branch 2 is judged to meet the fault requirement in this cycle, the third position of the fault code should be set to 1b at this time. This implementation plan provides a specific code implementation:

[0091] FLAG|=1U<<3;

[0092] (3) Update fault code

[0093] When all fault conditions of a progressive branch are diagnosed, the fault code needs to be updated based on the fault condition diagnosis results, iteration rules, iteration times, fault major category information, fault minor category information, historical alarm flags, etc. The following will explain in detail with specific examples:

[0094] (3-1) If the progressive branch 1 alarms in this cycle and the system alarms: Assume that the progressive branch 1 judgment of branch 2 is completed in this cycle, and the result is (1,0,1,0,1,0,0,1), and the judgment results of the previous 6 cycles are (1,0,1,0,1,1), then the fault code should be updated to 0xD70210095, and the corresponding binary is:

[0095] 11 010111 0010 0001 0000000010010101b

[0096] (3-2) If the progressive branch 2 alarms in this cycle, but the system does not alarm: Assume that the progressive branch 1 judgment of branch 2 is completed in this cycle, and the result is (1,0,0,0,0,0,0,1), then the progressive branch 2 judgment is completed, and the result is (0,1,1,0), and the judgment results of the first 6 cycles are (1,0,1,0,0,1), then the fault code should be updated to 0x13220006, and the corresponding binary is:

[0097] 00 010011 0002 0002 0000000000000110b

[0098] To update the alarm code, follow these steps:

[0099] 1) Supplement the information of major and minor fault categories;

[0100] 2) If the alarm condition information does not meet the fault requirements and there is a next progressive branch, then exit the update;

[0101] 2) If the alarm condition information does not meet the fault requirements and there is no next progressive branch, the historical alarm information is updated (the historical alarm information is shifted left, the fault code 24 is at position 0b), and the total alarm information is cleared;

[0102] 3) If the alarm condition information meets the fault requirements, the historical alarm information is updated (the historical alarm information is shifted left, and the fault code 24 is at position 1b), and whether to update the general alarm flag is determined based on the iteration rules and the number of iterations.

[0103] The iteration rule refers to the mode of using the historical alarm information of the adjacent 6 cycles to determine whether to update the general alarm flag. This implementation scheme implements two rules at the same time:

[0104] 1) If the historical alarm information for consecutive “iteration times” cycles is 1b, the total alarm flag is updated to 11b;

[0105] 2) In 6 cycles, if the historical alarm information of "iteration times" cycles is 1b, the total alarm flag is updated to 11b;

[0106] This implementation provides a specific code implementation for updating the alarm flag:

[0107] Uint32 FlagRefresh(Uint32 Flag,char thisCount,cahr bigClass,charsmallClass=0,BOOL isEnd=TRUE,char iterCount=3,char iterType=01b){

[0108] Flag=(Flag&0xFF00FFFF)|((bigClass<<20)&0x00F00000)|

[0109] ((smallClass<<16)&0x000F0000);

[0110] if(SumOfBit(Flag,0,15) <thisCount)

[0111] {

[0112] if(isEnd == TRUE)

[0113] {

[0114] Flag=(Flag&0x00FFFFFF)|((Flag<<1)&0x3E000000);

[0115] }

[0116] }

[0117] else

[0118] {

[0119] Flag=(Flag|0x01000000)|((Flag<<1)&0x3E000000);

[0120] if((iterType==01b)&&(SumOfBit(Flag,24,(23+iterCount))>=

[0121] iterCount))

[0122] {

[0123] Flag |= 0xC0000000;

[0124] }

[0125] else if((iterType==10b)&&(SumOfBit(Flag,24,29)>=iterCount))

[0126] {

[0127] Flag |= 0xC0000000;

[0128] }

[0129] }

[0130] return Flag;

[0131] }

[0132] Some specific parameters in this embodiment are related to the design indexes of the liquid hydrogen and liquid oxygen engine fault diagnosis system, and are described using variables in the invention. When the fault diagnosis system of other types of engines is applied, the method can be introduced for calculation according to the actual situation, which has certain scalability.

[0133] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0134] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method, characterized in that include: Design fault codes, including alarm sign information, alarm category information and alarm condition information; Perform fault code initialization processing according to fault code design requirements; Use the initialization processed fault code to diagnose the fault condition of the current control cycle; Assigning a fault condition result to the fault code after initialization processing according to the fault condition diagnosis result; According to the fault condition diagnosis result, the fault code after the fault condition result is assigned a value is updated with a general alarm flag; The fault code updated by the general alarm flag is used as the fault detection result of the current control cycle.

2. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 1, characterized in that: The alarm mark information includes a total alarm mark and a historical alarm mark, and the design method is as follows: The 31st to 30th bits of the preset fault code represent the general alarm flag, which is represented by a 2-bit code, with 00b indicating no fault, 11b indicating a fault, and 01b and 10b indicating invalid data; The 29th to 24th bits of the preset fault code represent the historical alarm flag, which is represented by a 6-bit code and is used to record the fault code alarm conditions of 6 cycles. The 24th bit represents the alarm condition of this cycle. 0b indicates no fault, and 1b indicates a fault.

3. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 1, characterized in that: The alarm category information includes major fault category information and minor fault category information, and the design method is as follows: The 23~x bits of the preset fault code represent the major fault category information, which is used to select n fault diagnosis branch processes according to the alarm condition information; The (x-1) to 16 bits of the preset fault code represent fault sub-category information, which is used to characterize the progressive branch process under the fault diagnosis branch process according to the entered fault diagnosis branch process; 23>x>16。 4. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 3, characterized in that: During the control cycle of each fault code, the alarm category information only enters one fault diagnosis branch process; Under any fault diagnosis branch process, there are m progressive branch processes. When the previous progressive branch process does not meet the fault code design requirements, the next progressive branch process is entered.

5. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 4, characterized in that: The alarm condition information is that under any progressive branch process, there are k (k<16) fault conditions, and each fault condition corresponds to one of the fault codes 15 to 0.

6. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 4, characterized in that: The fault code initialization process is to set the fault code 23~0 to 0b.

7. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 4, characterized in that: The method of assigning the fault condition result is: The fault condition diagnosis results under each progressive branch process are assigned to the corresponding position of the fault code, with 0b indicating no fault and 1b indicating a fault; if any fault conditions exist under any progressive branch process in the current control cycle, the fault code position corresponding to each fault condition position is set to 1b.

8. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 4, characterized in that: The fault code design requirements include iteration rules, iteration times, fault diagnosis branch process information, progressive branch process information, and historical alarm flags. The method for updating the fault code after the fault condition result is assigned is: First, update the fault diagnosis branch process information and the progressive branch process information; If the alarm condition information of the current fault code does not meet the fault code design requirements and there is a next progressive branch process, then exit the current update process; if the fault condition diagnosis result does not meet the fault condition diagnosis result requirements and there is no next progressive branch process, then update the historical alarm information; If the alarm condition information of the current fault code meets the fault code design requirements, determine whether to update the general alarm flag according to the iteration rules and the number of iterations; After updating the general alarm flag, the fault code of the current control cycle is updated.

9. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 8, characterized in that: The method for updating the historical alarm information is: shifting the historical alarm information of the fault code of the current control cycle to the left, and setting the position of the fault code 24 to 0b.

10. A liquid hydrogen and liquid oxygen engine fault diagnosis fault code design and application method according to claim 9, characterized in that: The iteration rule is: use the historical alarm information within 6 adjacent control cycles to make a judgment. If the historical alarm information of consecutive iteration number cycles is 1b, the total alarm flag is updated to 11b; if in consecutive iteration number cycles, the historical alarm information of a total of iteration number cycles is 1b, the total alarm flag is updated to 11b; wherein the number of iterations is ≤6 times.

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