A design method for the alignment process of inertial navigation products

Abstract

The present invention relates to the technical field of aviation airborne inertial navigation products, specifically a design method for an inertial navigation product alignment process, comprising the following steps: step (1) system startup stage; step (2) platform rapid zero return stage; step (3) horizontal open circuit coarse alignment, coarse estimation of wandering angle stage; step (4) platform horizontal zero return stage; step (5) horizontal open circuit coarse alignment, coarse estimation of wandering angle and dimension detection stage; step (6) platform horizontal precise zero return stage; step (7) azimuth alignment stage. The present invention clarifies the different tasks, processing methods and technical indicators of each stage by setting different alignment stages, as well as the processing method after the indicators do not meet the conditions, so as to modularize the alignment process. At the same time, by providing a platform-type navigation product alignment process with a status code, the completion status of the product in the alignment process is judged, which effectively improves the design efficiency of the product alignment process and the recognition of the product alignment status.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation airborne inertial navigation products, in particular to a design method for an alignment process of an inertial navigation product. Background Art

[0002] Platform-based inertial navigation products require alignment before entering navigation mode. This provides a measurement reference for the accelerometers, aligning the inertial navigation platform with the ideal platform coordinate system, and thus providing the necessary initial conditions for navigation calculations. The quality of alignment is directly related to the accuracy of the inertial navigation system.

[0003] Initial alignment of an inertial navigation system typically involves both horizontal and azimuth alignment. Horizontal alignment is typically based on the gravity vector. A horizontal accelerometer senses the component of gravity acceleration along the platform plane, generating a torque signal to control the platform and return it to the local horizontal plane. Azimuth alignment, performed on top of horizontal alignment, aims to determine the platform's azimuth and heading. Compass alignment is typically employed (i.e., using a gyroscope to sense the Earth's rotational angular velocity for azimuth alignment).

[0004] Chinese patent CN103134521A (published on June 5, 2013) discloses a method for rapid alignment of a platform's inertial navigation system under arbitrary azimuth misalignment. This invention only discloses a method for achieving rapid initial alignment of the platform's inertial navigation system under arbitrary azimuth misalignment by leveraging the platform's inertial navigation gyroscope's ability to achieve torque locking through platform rotation and traditional horizontal alignment. A drawback of this patent is that it only discloses an alignment method, without specifying the alignment process, indicators for each stage, or processing methods.

[0005] Chinese patent CN105203129A (published on December 30, 2015) discloses a method for initial alignment of an inertial navigation system. This invention, however, is applicable to MEMS sensors, a type of strapdown inertial navigation product. The alignment method utilizes a Kalman filter based on the mounting angle. However, this invention has several drawbacks: 1. It targets MEMS sensors, which has a narrow scope. 2. It relies on calculations based on the mounting angle, resulting in low alignment accuracy. 3. It lacks a design for the alignment process, relying solely on a calculation method. Summary of the Invention

[0006] In response to the above technical problems, the present invention proposes a design method for the alignment process of an inertial navigation product.

[0007] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0008] A design method for an inertial navigation product alignment process includes the following steps:

[0009] Step (1) System startup phase (status code "90");

[0010] Step (2) Platform rapid return to zero stage (status code "80");

[0011] Step (3) Horizontal open circuit coarse alignment and coarse estimation of wander angle (status code "70");

[0012] Step (4) Platform level return to zero stage (status code "60");

[0013] Step (5) Horizontal open circuit coarse alignment, coarse estimation of wander angle and dimension detection stage (status code "50");

[0014] Step (six) Platform level precision zero return stage (status code "40");

[0015] Step (seven) Azimuth alignment phase (status code "30→01").

[0016] Preferably, step (1) includes setting the start-up conditions, performing the start-up process, and initializing the parameters, wherein the start-up conditions are: a) the gyroscope temperature is less than 70°; b) the simulation switch quantity is invalid; when condition a is not met, the system waits, and when it is met, executes the remaining operations in sequence; when condition b is not met, executes the "simulation" process.

[0017] Preferably, the startup process includes the following steps:

[0018] Step (1) seal the azimuth ring and the inner ring, and heat the system;

[0019] Step (2) straightening the inner ring and the outer rolling ring;

[0020] Step (3) straightening the azimuth ring and the pitch ring;

[0021] Step (4) starting the upper gyroscope;

[0022] Step (5) gyro start validity detection;

[0023] Step (6) starting the lower gyroscope;

[0024] Step (7) gyro validity test;

[0025] Step (8) straightening the azimuth ring, inner roll ring, pitch ring, and outer ring;

[0026] Step (9) The platform is ready.

[0027] Preferably, step (2) includes: a large current return to zero process and a small current return to zero process; wherein the large current return to zero process is specifically as follows:

[0028] Step (S1) Calculation of large current return to zero angle:

[0029]

[0030]

[0031] F x =[K ya *(Ny'-N y0 *T 回 )] / T 回 ;

[0032] F y =[-K xa *(Nx'-N x0 *T 回 )] / T 回 ;

[0033] Where:

[0034] T return: Calculate the platform deflection time when returning to zero;

[0035] Ts: sampling time interval;

[0036] N Xi 、N Yi : The number of accelerometer pulses sampled in each sampling period;

[0037] F x 、F y : The average deflection angle of the platform X and Y axes in 1s;

[0038] K xa , K ya : Scale factor when aligning the X and Y axis accelerometers;

[0039] N x0 、N y0 : X, Y axis accelerometer zero position.

[0040] Step (S2) Calculation of the angular rate of large current returning to zero:

[0041] ω x '=ω y '=-I 大 *K g ;

[0042] Here the return-to-zero angular rate limit is: ω x '=ω y '=-3000.

[0043] Where:

[0044] ω x '、ω y ': angular rate of return to zero during inertial navigation alignment;

[0045] I 大 : Inertial large current return to zero current, fixed value, set to 60mA;

[0046] K g : The precession coefficient of the gyroscope is 60" / mA / s.

[0047] Step (S3) Calculation of large current return to zero time:

[0048] t x =F x / ω x ';

[0049] t Y =F Y / ω Y ';

[0050] Where: t x , t Y : Large current return to zero time.

[0051] Step (S4) High current return to zero condition:

[0052] F x ≥300",F y ≥300" (X and Y axes are judged separately). When the large current return to zero condition is met, the large current return to zero is started. Otherwise, the small current return to zero is performed. The large current return to zero condition is judged once at the end of the second second of the status code "80".

[0053] Preferably, the specific process of the small current return to zero process is as follows:

[0054] Step (s1) Small current return to zero condition:

[0055] When the platform deflection angle does not meet the conditions for the large current zero return process, the small current zero return process begins;

[0056] Step (s2) Calculation of the small current return to zero deflection angle:

[0057] It is determined by the bias angle 1s before this return-to-zero sub-process, and is calculated in the same way as the large current return-to-zero bias angle, where T return = 1s.

[0058] Step (s3) Calculation of small current return to zero time:

[0059]

[0060]

[0061] Step (s4) Calculation of the angular rate of small current return to zero:

[0062]

[0063]

[0064] Step (s5) small current return to zero process:

[0065] First, calculate the return to zero angle, then calculate the return to zero time, calculate the return to zero rate, and use the actuator to return to zero. It is judged whether the return to zero rate is 0. If it is not 0, continue the return to zero operation.

[0066] Preferably, the specific process of step (3) of horizontal open circuit coarse alignment and coarse estimation of wander angle is as follows:

[0067] The number of accelerometer output pulses is sampled once every 25ms;

[0068] The platform heading angle and attitude angle are sampled every 2.5ms;

[0069] Coarse alignment uses a pure open-loop method. Acceleration is calculated using the platform's input, and azimuth is calculated using the platform's heading. The platform's angular rate is calculated from the change in deflection, used to estimate the wander angle and gyro drift, and to apply a moment. The platform is brought back and forth to the local horizontal plane. During this phase, the local longitude and latitude are input and checked.

[0070] Preferably, the specific process of step (4) platform level return to zero stage is:

[0071] When the status code is "60", the "heading valid" switch value is set;

[0072] After the wander angle is roughly estimated, the platform returns to zero with a small current. The return time is at least 10 seconds. When the return angle rate is not less than 100" / s, the return time is automatically extended by 5 seconds.

[0073] Coarse alignment uses a pure open-loop method. Acceleration is calculated using the platform's input, and azimuth is calculated using the platform's heading. The platform's angular rate is calculated from the change in deflection, used to estimate the wander angle and gyro drift, and to apply a moment. The platform is brought back and forth to the local horizontal plane. During this phase, the local longitude and latitude are input and checked.

[0074] Preferably, the specific process of step (5) horizontal open-circuit coarse alignment, coarse estimation of wander angle and dimension detection is as follows:

[0075] The calculation process of horizontal deflection angle, heading angle and drift estimation is the same as that of status code "70";

[0076] Wander angle estimation and correction, when status code "50" ends, the wander angle is estimated and corrected as in status code "70", without performing validity check.

[0077] Preferably, the termination conditions of the horizontal open-circuit coarse alignment, coarse estimation of wander angle and dimension detection phase in step (5) are:

[0078] When the total power-on time T>t, t is determined as follows:

[0079] t = 250 - K2 × (T40 - 20);

[0080] Where: t=490-6×(T40+10); T40<-10; T40 is the initial temperature of the gyroscope.

[0081] Preferably, the specific process of step (seven) azimuth alignment stage is:

[0082] With both azimuth and horizontal open circuits, under normal compass alignment conditions, alignment time 210s, and status code from "30" to "01", the horizontal and azimuth drifts were estimated using the recursive least squares method;

[0083] After the initial performance test after 90 seconds, the normal compass alignment is completed and the status code changes to "25". If the test fails, the status code "30" will be extended to open circuit alignment. During this process, the initial test is continuously performed. If it passes, the pass button will be pressed to process it. The alignment time can be extended for up to 90 seconds. If it fails, the system will exit and report a fault.

[0084] Initial test conditions: bx≤1.0, by≤1.0;

[0085] The initial test conditions are met at the same time and the test passes;

[0086] Performance test conditions for alignment after 90s:

[0087] Perform drift test stability check after 90 seconds:

[0088] △W=|WW′|; W′=0; W′ is the estimated value of gyro drift in the previous 1 second;

[0089] Set the P value to 0.02, 0.015, 0.01, 0.005, 0.002. When △W<P, the test passes, otherwise it fails. The alignment time can be extended by up to 90s in the original state. If it fails, a fault is reported.

[0090] Status code processing method:

[0091] When P = 0.02, the status code changes from "25" to "20";

[0092] When P = 0.015, the status code changes from "20" to "15";

[0093] When P = 0.01, the status code changes from "15" to "10";

[0094] When P = 0.005, the status code changes from "10" to "05";

[0095] When P = 0.002, the status code changes from "05" to "01";

[0096] The condition for status code "05" to change to "01" is that in addition to the P value meeting the conditions, the alignment time must be greater than 8 minutes. Otherwise, the system will wait in status code "05" until the alignment time requirement is met. When the status code is "01", the gyrocompass alignment is completed and the system enters the working state.

[0097] The beneficial effects of the present invention are:

[0098] Compared with the existing technology, the present invention sets different alignment stages, clarifies the different tasks, processing methods and technical indicators of each stage, as well as the processing methods when the indicators do not meet the conditions, so as to modularize the alignment process. At the same time, by providing a platform-based navigation product alignment process with a status code, the completion status of the product in the alignment process is judged, which effectively improves the design efficiency of the product alignment process and the recognition of the product alignment status. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0100] Figure 1 is a flow chart of the present invention;

[0101] Figure 2 This is a flow chart of the system startup phase in the present invention;

[0102] Figure 3 Schematic diagram of the large current zero return process in the present invention;

[0103] Figure 4 This is a schematic diagram of the small current zero return process in the present invention;

[0104] Figure 5 This is a flow chart of horizontal open circuit coarse alignment in the present invention. DETAILED DESCRIPTION

[0105] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0106] like Figure 1 As shown, a design method for an inertial navigation product alignment process includes the following steps:

[0107] Step (1) System startup phase (status code "90").

[0108] Specifically, it includes setting startup conditions, performing startup procedures, and initializing parameters.

[0109] The starting conditions are:

[0110] a) The gyroscope temperature is less than 70°;

[0111] b) The simulated switch value is invalid;

[0112] When condition a is not met, the system waits, and executes the remaining operations in sequence after it is met; when condition b is not met, the "simulation" process is executed.

[0113] The startup process is divided into nine stages;

[0114] The startup process changes according to time and temperature. Different switch values ​​can be set to complete the system startup process. See the time axis. Figure 2 shown.

[0115] The specific startup process is as follows:

[0116] Step (1) Seal the azimuth ring and the inner ring and heat the system.

[0117] When the starting conditions are met, the system outputs the "sealing and straightening" switch value and starts the temperature control process at the same time.

[0118] Step (2) straightens the inner ring and the outer rolling ring.

[0119] 2 seconds after startup, when the gyroscope temperature is greater than 0°C, the computer outputs the "righting the inner and outer roll rings" switch value to control the platform's inner and outer roll rings to right themselves, otherwise it will wait in the original state.

[0120] Step (3) straighten the azimuth ring and the pitch ring.

[0121] 2 seconds after the inner and outer roll rings are straightened, the computer outputs the switch values ​​of "0° straightening" and "azimuth and pitch straightening" to control the straightening of the platform's azimuth and pitch rings.

[0122] Step (4) starts the upper gyro.

[0123] 2 seconds after the azimuth ring is straightened, when the gyro temperature is greater than 20℃ and the time is greater than or equal to 6 seconds, the computer outputs the "start upper gyro" switch value to start the upper gyro, otherwise it waits in the original state.

[0124] Step (5) The gyro starts the validity test.

[0125] 4 seconds after the gyro is started, the startup validity is tested. Check the A / D converter input voltage AD1; after 5 seconds, check the input voltage AD2; after 6 seconds, check the input voltage AD3. Check the voltage increase rate S1 = AD2-AD1, S2 = AD3-AD2. If AD3 > 3.5V or 0.2 < S2 < 0.7, the gyro startup is considered successful. Otherwise, the startup is stopped and restarted after a delay of 1 second. If it does not reach the specified value within 30 seconds from the first time, the "upper gyro motor power supply" fault is set and the process exits.

[0126] Step (6) starts the lower gyroscope.

[0127] 6 seconds after the upper gyro starts and passes the validity test, the computer outputs the "start lower gyro" switch value. When the upper gyro is started for 10 seconds, that is, the gyroscope temperature is greater than 20℃, 16 seconds later, the lower gyroscope is started and the timing is started at the same time.

[0128] Step (7) is to check the effectiveness of the gyroscope.

[0129] 4 seconds after the lower gyro is started, the startup validity is tested and the A / D conversion input voltage AD4 is checked; in the 5th second, AD5 is checked; in the 6th second, AD6 is checked, S3=AD5-AD4; S4=AD6-AD5, and AD6>3.5V or 0.2V<S3<0.7V and 0.2V<S4<0.7V are judged to be successful. Otherwise, the startup is judged to be successful after a delay of 1s. From the first time to 30s, if the specified value is not reached, the process is exited.

[0130] Step (8) Straightening of the azimuth ring, inner roll ring, pitch ring and outer ring.

[0131] Eight seconds after the lower gyro's startup validity test passes, the computer outputs "Stable Horizontal" and "Stable Azimuth Locked" switches, and the system transitions from the righting state to the stable state. If these tests pass, the upper gyro motor is >3.5V and the power-on time is within 28 seconds, the azimuth, inner roll, pitch, and outer rings are righted.

[0132] Step (9) The platform is ready.

[0133] 12 seconds after the stabilization conversion, the system startup process is completed, that is, the 90 state is completed and it can be transferred to the 80 state. At room temperature, the time from system startup to platform readiness is set to 40 seconds. As the starting temperature drops and the gyro starts to start, the startup time will automatically increase accordingly.

[0134] Parameter initialization specifically includes position initialization and wander angle initialization; among which, position initialization includes inputting the latitude and longitude information of the location;

[0135] The initialization of the wander angle includes the calculation of the wander angle according to the following formula: α=ψ p -ψ T ;

[0136] Where: T Input the effective true heading to the system; ψ P System platform heading.

[0137] That is, when there is a true heading input, the wander angle is calculated based on the true heading. This calculation process is continuous during the entire status code "90" and "80" status process. When the status code "70" is valid and the "ready" command is valid, the calculation process continues and is calculated before the true heading.

[0138] Step (2) Platform rapid return to zero phase (status code "80").

[0139] This stage includes the large current return to zero process and the small current return to zero process; the large current first and then the small current, the large current return to zero process is controlled according to time, and the small current has a cycle of every 5 seconds.

[0140] The total return to zero time for large and small currents is 30s, and the Z axis does not return to zero.

[0141] The specific process of large current zero return is as follows:

[0142] Step (S1) Calculation of large current return to zero angle:

[0143] At the beginning, it is determined based on the average value of the first 2 seconds:

[0144]

[0145]

[0146] F x =[K ya *(Ny'-N y0 *T 回 )] / T 回 ;

[0147] F y =[-K xa *(Nx'-N x0 *T 回 )] / T 回 ;

[0148] Where:

[0149] T return: Calculate the platform deflection time when returning to zero, here it is 2s;

[0150] Ts: sampling time interval;

[0151] N Xi 、N Yi : The number of accelerometer pulses sampled in each sampling period;

[0152] F x 、F y : The average deflection angle of the platform X and Y axes in 1s;

[0153] K xa , K ya : Scale factor when aligning the X and Y axis accelerometers;

[0154] N x0 、N y0 : X, Y axis accelerometer zero position.

[0155] Step (S2) Calculation of the angular rate of large current returning to zero:

[0156] ω x '=ω y '=-I 大 *K g ;

[0157] Here the return-to-zero angular rate limit is: ω x '=ω y '=-3000.

[0158] Where:

[0159] ω x '、ω y ': angular rate of return to zero during inertial navigation alignment;

[0160] I 大 : Inertial large current return to zero current, fixed value, set to 60mA;

[0161] K g : The precession coefficient of the gyroscope is 60" / mA / s.

[0162] Step (S3) Calculation of large current return to zero time:

[0163] t x =F x / ω x ';

[0164] t Y =F Y / ω Y ';

[0165] Where: t x , t Y : Large current return to zero time.

[0166] Step (S4) High current return to zero condition:

[0167] F x ≥300",F y ≥300" (X and Y axes are judged separately). When the large current return to zero condition is met, the large current return to zero is started. Otherwise, the small current return to zero is performed. The large current return to zero condition is judged once at the end of the second second of the status code "80".

[0168] Small current zero return process:

[0169] Generally, every 5 seconds for a small current return to zero is a return to zero sub-process. When a return to zero sub-process is less than 5 seconds, the return to zero sub-process is merged into the previous return to zero sub-process. That is, the last small current return to zero sub-process time is between 5 and 10 seconds. Figure 3 shown.

[0170] Step (s1) Small current return to zero condition:

[0171] When the platform deflection angle does not meet the conditions for the large current zero return process, the small current zero return process begins;

[0172] Step (s2) Calculation of the small current return to zero deflection angle:

[0173] It is determined by the bias angle 1s before this return-to-zero sub-process, and is calculated in the same way as the large current return-to-zero bias angle, where T return = 1s.

[0174] Step (s3) Calculation of small current return to zero time:

[0175]

[0176]

[0177] Step (s4) Calculation of the angular rate of small current return to zero:

[0178]

[0179]

[0180] Step (s5) small current return to zero process:

[0181] First calculate the zero return angle, then calculate the zero return time, calculate the zero return rate, and perform zero return by the actuator to determine whether the zero return rate is 0. If it is not 0, continue the zero return operation. Figure 4 shown.

[0182] Step (3) Horizontal open-circuit coarse alignment and coarse estimation of wander angle stage (status code "70").

[0183] This stage mainly completes the system's horizontal rough alignment and wander angle estimation. The platform's horizontal deflection angle is converted based on the acceleration measured by the accelerometer. Then, the horizontal axis wander is fitted by the first-order minimum recursive formula. Finally, the wander angle is calculated based on the drift. Figure 5 shown.

[0184] The control process is as follows: the number of pulses output by the accelerometer is sampled once every 25ms;

[0185] The platform heading angle and attitude angle are sampled every 2.5ms;

[0186] Coarse alignment uses a pure open-loop method. Acceleration is calculated using the platform's input, and azimuth is calculated using the platform's heading. The platform's angular rate is calculated from the change in deflection, used to estimate the wander angle and gyro drift, and to apply a moment. The platform is brought back and forth to the local horizontal plane. During this phase, the local longitude and latitude are input and checked.

[0187] Step (4) Platform level return to zero stage (status code "60").

[0188] The specific process is as follows: When status code "60" is reached, the "Heading Valid" switch is set. After the wander angle is roughly estimated, the platform is returned to zero with a small current. The return time is at least 10 seconds. If the return rate is no less than 100" / s, the return time is automatically extended by 5 seconds. Coarse alignment uses a pure open-circuit alignment method, calculating the platform deflection using the added input, the azimuth deflection using the platform heading, and the angular rate calculated from the change in the platform deflection. This is used to estimate the wander angle and gyro drift and apply the torque. The platform is then brought back and forth to the local horizontal plane. During this stage, the local longitude and latitude are input and the latitude is checked.

[0189] Step (5) Horizontal open circuit coarse alignment, coarse estimation of wander angle and dimension detection phase (status code "50"). Figure 5 shown.

[0190] The specific process is as follows: the calculation of horizontal deflection angle, heading angle and drift estimation process are the same as the status code "70";

[0191] Wander angle estimation and correction, when status code "50" ends, the wander angle is estimated and corrected as in status code "70", without performing validity check.

[0192] The end conditions are:

[0193] When the total power-on time T>t, t is determined as follows:

[0194] t = 250 - K2 × (T40 - 20);

[0195] Where: t=490-6×(T40+10); T40<-10; T40 is the initial temperature of the gyroscope.

[0196] Step (six) Platform level precision zero return stage (status code "40").

[0197] Specifically: return to zero time 10s, requirements are the same as step (4).

[0198] Step (seven) Azimuth alignment phase (status code "30→01").

[0199] The specific process is:

[0200] With both azimuth and horizontal open circuits, under normal compass alignment conditions, alignment time 210s, and status code changes from "30" to "01", the horizontal and azimuth drifts were estimated using the recursive least squares method;

[0201] After the initial performance test after 90 seconds, the normal compass alignment is completed and the status code changes to "25". If the test fails, the status code "30" will be extended to open circuit alignment. During this process, the initial test is continuously performed. If it passes, the pass button will be pressed to process it. The alignment time can be extended for up to 90 seconds. If it fails, the system will exit and report a fault.

[0202] Initial test conditions: bx≤1.0, by≤1.0;

[0203] The initial test conditions are met at the same time and the test passes;

[0204] Performance test conditions for alignment after 90s:

[0205] Perform drift test stability check after 90 seconds:

[0206] △W=|WW′|; W′=0; W′ is the estimated value of gyro drift in the previous 1 second;

[0207] Set the P value to 0.02, 0.015, 0.01, 0.005, 0.002. When △W<P, the test passes, otherwise it fails. The alignment time can be extended by up to 90s in the original state. If it fails, a fault is reported.

[0208] Status code processing method:

[0209] When P = 0.02, the status code changes from "25" to "20";

[0210] When P = 0.015, the status code changes from "20" to "15";

[0211] When P = 0.01, the status code changes from "15" to "10";

[0212] When P = 0.005, the status code changes from "10" to "05";

[0213] When P = 0.002, the status code changes from "05" to "01";

[0214] The condition for status code "05" to change to "01" is that in addition to the P value meeting the conditions, the alignment time must be greater than 8 minutes. Otherwise, the system will wait in status code "05" until the alignment time requirement is met. When the status code is "01", the gyrocompass alignment is completed and the system enters the working state.

[0215] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and description merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A design method for an inertial navigation product alignment process, characterized by: The steps are as follows: Step 1: System startup phase, at this time the status code is "90"; Step 2: The platform quickly returns to zero. The status code is "80": Step 2 includes: a large current return to zero process and a small current return to zero process; wherein, the specific process of the large current return to zero process is as follows: Step S1: Calculation of the angle of large current returning to zero: ; Where: T return: Calculate the platform deflection time when returning to zero; Ts: sampling time interval; N Xi 、N Yi : The number of accelerometer pulses sampled in each sampling period; F x 、F y : The average deflection angle of the platform X and Y axes in 1s; K xa , K ya : Scale factor when aligning the X and Y axis accelerometers; N x0 、N y0 : X, Y axis accelerometer zero position; Step S2: Calculation of the angular rate of large current returning to zero: ; Here the return-to-zero angular rate limit is: ; Where: ω x '、ω y ': angular rate of return to zero during inertial navigation alignment; I 大 : Inertial large current return to zero current, fixed value, set to 60mA; K g : The precession coefficient of the gyroscope is 60" / mA / s; Step S3: Calculation of high current return to zero time: t x =F x / ω x '; t Y =F Y / ω Y '; Where: t x , t Y : High current return to zero time; Step S4: High current return to zero condition: F x ≥300",F y ≥300", when the high current return to zero condition is met, the high current return to zero is started, otherwise, the low current return to zero is performed. The high current return to zero condition is judged once at the end of the second second of the status code "80"; The specific process of small current zero return is as follows: Step s1: Small current return to zero condition: When the platform deflection angle does not meet the conditions for the large current zero return process, the small current zero return process begins; Step s2: Calculation of the small current return to zero angle: It is determined by the current deflection angle 1s before this return-to-zero sub-process, and is calculated in the same way as the large current return-to-zero deflection angle, where T return = 1s; Step s3: Calculation of small current return to zero time: ； Step s4: Calculation of the angular rate of return to zero of small current: ； Step s5: Small current return to zero process: First, calculate the zero return angle, then calculate the zero return time, calculate the zero return rate, and then use the actuator to return to zero. It is judged whether the zero return rate is 0. If it is not 0, continue the zero return operation. Step 3: Horizontal open circuit coarse alignment and coarse estimation of wander angle. The status code is "70" at this time. Step 4: The platform returns to zero level. The status code is "60" at this time. Step 5: Horizontal open circuit coarse alignment, rough estimation of wander angle and dimension detection phase. The status code is "50" at this time: The completion conditions for the horizontal open-circuit coarse alignment, coarse estimation of wander angle, and dimension detection phase in step 5 are: When the total power-on time T>t, t is determined as follows: t=250-K2×(T40-20); Where: ; t = 490 - 6 × (T40 + 10); T40 < -10; T40 is the initial temperature of the gyroscope; Step 6: The platform returns to zero precisely. The status code is "40" at this time. Step 7: Azimuth alignment phase. The status code is "30→01": The specific process of step seven azimuth alignment stage is as follows: With both azimuth and horizontal open circuits, under normal compass alignment conditions, an alignment time of 210 seconds, and status codes from "30" to "01", the horizontal and azimuth drifts were estimated using the recursive least squares method. After the initial performance test after 90 seconds, normal compass alignment is completed and the status code changes to "25". If the test fails, the status code "30" will be extended to open circuit alignment. During this process, the initial test is repeated. If it passes, the alignment time can be extended by up to 90 seconds. If it fails, the system will exit and report a fault. Initial test conditions: bx≤1.0, by≤1.0; The initial test conditions are met at the same time and the test passes; Performance test conditions for alignment after 90s: Perform drift test stability check after 90 seconds: △W=|WW′|; W′=0; W′ is the estimated value of gyro drift in the previous 1 second; Set the P value to 0.02, 0.015, 0.01, 0.005, 0.

002. When △W<P, the test passes, otherwise it fails. The alignment time can be extended by up to 90s in the original state. If it fails, a fault is reported. Status code processing method: When P = 0.02, the status code changes from "25" to "20"; When P = 0.015, the status code changes from "20" to "15"; When P = 0.01, the status code changes from "15" to "10"; When P = 0.005, the status code changes from "10" to "05"; When P = 0.002, the status code changes from "05" to "01"; The condition for status code "05" to change to "01" is that in addition to the P value meeting the conditions, the alignment time must be greater than 8 minutes. Otherwise, the system will wait in status code "05" until the alignment time requirement is met. When the status code is "01", the gyrocompass alignment is completed and the system enters the working state.

2. The method for designing an alignment process for an inertial navigation product according to claim 1, characterized in that: Step 1 includes setting the startup conditions, performing the startup process, and initializing parameters. The startup conditions are: a. The gyroscope temperature is less than 70°C; b. The simulated switch value is invalid; when condition a is not met, the system waits, and when it is met, executes the remaining operations in sequence; when condition b is not met, the "simulation" process is executed.

3. The method for designing an alignment process for an inertial navigation product according to claim 2, characterized in that: The startup process includes the following steps: Step 1: Seal the azimuth ring and the inner ring, and heat the system; Step 2: Straighten the inner ring and outer roll ring; Step 3: Straighten the azimuth and elevation rings; Step 4: Start the gyro; Step 5: Start the gyro validity test; Step 6: Start the gyro; Step 7: Gyro validity test; Step 8: Straighten the azimuth ring, inner roll ring, pitch ring, and outer ring; Step 9: The platform is ready.

4. The method for designing an alignment process for an inertial navigation product according to claim 1, characterized in that: The specific process of step 3, horizontal open circuit coarse alignment and coarse estimation of wander angle, is as follows: The number of accelerometer output pulses is sampled once every 25ms; The platform heading angle and attitude angle are sampled every 2.5ms; Coarse alignment uses a pure open-loop alignment method. The platform deflection is calculated using the added input, and the azimuth deflection is calculated using the platform heading. The platform angular rate is calculated from the change in the platform deflection angle, which is used to estimate the wander angle and gyro drift and apply a moment to move the platform back and forth to the local horizontal plane. At this stage, the local longitude and latitude are input and the latitude is checked.

5. The method for designing an alignment process of an inertial navigation product according to claim 1, characterized in that: Step 4: The specific process of the platform returning to zero level is as follows: When the status code is "60", the "heading valid" switch value is set; After the wander angle is roughly estimated, the platform returns to zero with a small current. The return time is at least 10 seconds. When the return angle rate is not less than 100" / s, the return time is automatically extended by 5 seconds. Coarse alignment uses a pure open-loop alignment method. The platform deflection is calculated using the added input, and the azimuth deflection is calculated using the platform heading. The platform angular rate is calculated from the change in the platform deflection angle, which is used to estimate the wander angle and gyro drift and apply a moment to move the platform back and forth to the local horizontal plane. At this stage, the local longitude and latitude are input and the latitude is checked.

6. The method for designing an alignment process for an inertial navigation product according to claim 1, characterized in that: Step 5: Horizontal open circuit coarse alignment, rough estimation of wander angle and dimension detection. The specific process is as follows: The calculation process of horizontal deflection angle, heading angle and drift estimation is the same as that of status code "70"; Wander angle estimation and correction: When status code "50" ends, the wander angle is estimated and corrected as in status code "70" without performing validity check.

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