A method for controlling the inflation and time-sharing deflation of a spacecraft's airbag.

Abstract

This invention discloses a method for controlling the inflation and time-sharing deflation of spacecraft airbags, comprising: setting a waiting synchronization signal time parameter; when the spacecraft airbags reach the airbag inflation determination altitude, sending an airbag inflation command according to the waiting synchronization signal time parameter; when overload information reaches a preset threshold, determining the landing of the return capsule; determining the attitude of the return capsule, if it is in quadrant III facing forward, entering quadrant III facing forward deflation mode; if it is in quadrant I facing forward, entering quadrant I facing forward deflation mode; if the attitude is not determined after a predetermined time, controlling all airbags to deflate simultaneously, and the deflation ends. This invention can solve the problem of asynchronous airbag inflation commands caused by inter-board differences in redundant control systems.

Description

Technical Field

[0001] This invention relates to a method for controlling the inflation and time-sharing deflation of a spacecraft's cushioning airbag, belonging to the field of landing cushioning technology for recoverable spacecraft. Background Technology

[0002] The landing cushioning process is one of the most crucial stages in the execution of a recoverable spacecraft mission. Common methods and techniques for addressing spacecraft landing cushioning include mechanical cushioning, horizontal runway landing, active thrust reverse cushioning, and airbag cushioning. Airbag cushioning landing methods offer advantages such as small device mass, simple structure, small installation envelope, and low cost, and are therefore widely used in spacecraft design.

[0003] Traditional vented airbag cushioning designs release airbags during spacecraft descent, filling them with air. Upon landing, the airbags are compressed, and the compressed air is passively expelled through vents or valves, absorbing the impact energy and achieving cushioning. However, this approach results in a triangular overload curve, leading to high peak overload values ​​and increased susceptibility to environmental influences, potentially causing the spacecraft to tip over during landing. Using pressure- or mechanically controlled vent areas can effectively reduce peak overload values, but this design suffers from drawbacks such as complex drive structures, high assembly precision requirements, and low timing control accuracy.

[0004] FPGA Design of Landing Buffer Control System Based on Active Exhaust Airbags, Sun Xiyun et al., Space Return and Remote Sensing, Vol. 40, No. 8. This paper presents a simplified engineering approach for exhaust control, focusing on the active exhaust control method for airbags. However, the control system cannot independently control each airbag, and differentiated control needs improvement. The paper concludes by suggesting further research on how landing exhaust control strategies can adapt to different ground environments at landing sites, exploring methods to achieve optimal control under high reliability.

[0005] The patent "A Combined Buffer Active Exhaust Control System" by Li Bo et al., application number: CN202211528401.5, describes a method of differentially exhausting airbags by comparing the landing wind speed with a preset wind speed and then controlling the airbags according to a preset control strategy. In engineering implementation, the landing wind speed of the spacecraft cannot be written into the return control program in advance.

[0006] The patent "An Active Exhaust Control System and Method for Landing Buffer Airbags of Return Capsule" by Sun Xiyun et al., application number: 202018016796.6, describes real-time monitoring of the overload sensor data of the return capsule. This data is used as an excitation to perform a weighted evaluation of the force conditions at each airbag control point through the transfer function of the airbag landing control model. Based on the evaluation results, an exhaust control command sequence for the airbag is formed to exhaust the airbag and ensure that the overload value meets the requirements. The control method does not incorporate the motion characteristics of the parachute system. Summary of the Invention

[0007] The technical problem solved by the present invention is to overcome the shortcomings of the prior art and provide a method for controlling the inflation and time-sharing deflation of spacecraft buffer airbags, which can solve the problem of asynchronous airbag inflation commands caused by differences between boards in redundant control systems.

[0008] The technical solution of this invention is:

[0009] This invention discloses a method for controlling the inflation and time-sharing deflation of a spacecraft's cushioning airbag, comprising:

[0010] Set the waiting time parameter for the synchronization signal;

[0011] When the spacecraft's airbag reaches the airbag inflation detection altitude, an airbag inflation command is sent according to the waiting synchronization signal time parameter;

[0012] When the overload information reaches a preset threshold, the return capsule is determined to land;

[0013] The attitude of the return capsule is determined. If it is facing forward in quadrant III, the capsule enters the quadrant III forward venting mode; if it is facing forward in quadrant I, the capsule enters the quadrant I forward venting mode; if the attitude is not determined within the predetermined time, all airbags are controlled to vent simultaneously, and the venting ends.

[0014] Furthermore, in the above method, the waiting time parameter for the synchronization signal is specifically:

[0015] T_wait = ΔRef / M

[0016] ΔRef=Max{|Ref1-Ref2|, |Ref1-Ref3|, |Ref2-Ref3|}

[0017] M = V2 - V1

[0018] Among them, T_wait is the longest waiting time for inter-board synchronization; ΔRef is the maximum value of the voltage difference between boards; M is the change rate of the voltage at the synchronization control point height; Ref1, Ref2, and Ref3 are the reference voltages of the AD chips of the three boards respectively; V2 is the voltage value corresponding to the atmospheric pressure at the height 0.5 s after the control point, and V1 is the voltage value corresponding to the atmospheric pressure at the height 0.5 s before the control point.

[0019] Further, in the above method, the method for judging the attitude of the return capsule is as follows:

[0020] When AD1_G_FIT_X < YZ and AD2_G_FIT_X < YZ and AD3_G_FIT_Y > YZ, it is judged that the third quadrant is facing forward;

[0021] When AD1_G_FIT_X > YZ and AD2_G_FIT_X > YZ and AD3_G_FIT_Y < YZ, it is judged that the first quadrant is facing forward;

[0022] Among them, AD1_G_FIT_X is the value after AD sampling and filtering of the X-direction overload at the position of the overload sensor a; AD2_G_FIT_X is the value after AD sampling and filtering of the X-direction overload at the position of the overload sensor b; AD3_G_FIT_Y is the value after AD sampling and filtering of the Y-direction overload at the position of the overload sensor c; YZ is the minimum overload threshold for judging the movement direction.

[0023] Further, in the above method, the exhaust mode with the third quadrant facing forward is specifically as follows:

[0024] If min(PP1, PP2) > max(PP4, PP5), perform the control mode of facing forward in the third quadrant and raising the head;

[0025] If min(PP4, PP5) > max(PP1, PP2), perform the control mode of facing forward in the third quadrant and lowering the head;

[0026] If the attitude cannot be judged after exceeding the predetermined time, perform time-sharing exhaust, specifically: exhaust the airbags P1, P2, P3, and P6 first, and then exhaust the airbags P4 and P5 after a delay of 30 - 40 ms.

[0027] Further, in the above method, the control mode of facing forward in the third quadrant and raising the head is specifically as follows:

[0028] Sort the pressure values of the airbags P1, P2, P3, and P6, and select the airbag corresponding to the maximum value to exhaust first;

[0029] Delay for 10 - 15 ms, refresh the pressure values of the airbags P1, P2, P3, and P6 after sampling and filtering, assign the pressure value corresponding to the exhausted airbag to 0X 0, and then sort them;

[0030] When the same pressure value is obtained, the airbags are sorted in order of priority from largest to smallest according to the order of P1, P2, P3, P6, and the airbag with the highest priority is depressurized first.

[0031] When all values ​​are 0, the airbags are sorted in order of priority from largest to smallest according to the order of P1, P2, P3, P6, and the airbags with the highest priority are deflated first.

[0032] Continue in this manner at 10-15ms intervals until all airbags (P1, P2, P3, and P6) have finished deflating.

[0033] After a delay of 10-15ms, deflate the remaining P4 and P5 airbags.

[0034] Furthermore, in the above method, the forward-facing and head-down control mode in quadrant III is specifically as follows:

[0035] Sort the pressure values ​​of P1, P2, P3, and P6, and select the airbag corresponding to the minimum value to deflate first;

[0036] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P1, P2, P3, and P6, assign 0xFFF to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0037] When the same pressure value is obtained, the airbags P1, P2, P3, and P6 are sorted from highest to lowest priority, and the air is deflated according to the minimum priority value.

[0038] When all values ​​are 0xFFF, the airbags are sorted in order of priority from largest to smallest according to P1, P2, P3, P6, and the airbags with the highest priority that have not been deflated are deflated first.

[0039] Continue in this manner at 10ms intervals until all four airbags (P1, P2, P3, and P6) have finished deflating.

[0040] After a 10ms delay, deflate the remaining P4 and P5 airbags.

[0041] Furthermore, in the above method, the quadrant-I forward exhaust mode specifically refers to:

[0042] If min(PP1,PP2)>max(PP4,PP5), then proceed to the forward and head-down control mode in quadrant I;

[0043] If min(PP4,PP5)>max(PP1,PP2), then proceed with the forward-facing and head-up control mode in quadrant I;

[0044] If the attitude is not determined within the predetermined time, timed exhaust will be performed. Specifically, airbags P3, P4, P5, and P6 will be exhausted first, and airbags P1 and P2 will be exhausted after a delay of 30-40ms.

[0045] Furthermore, in the above method, the forward-facing and head-down control mode in quadrant I specifically refers to:

[0046] Sort the pressure values ​​of P4, P5, P6, and P3, and select the airbag corresponding to the minimum value to deflate first;

[0047] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P4, P5, P6, and P3, assign 0xFFF to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0048] When the same pressure value is obtained, the airbags are sorted from highest to lowest priority according to P4, P5, P6, and P3, and the air is depressurized according to the lowest priority value.

[0049] When all values ​​are 0xFFF, the airbags are sorted in order of priority from largest to smallest according to P4, P5, P6, P3, and the airbags with the highest priority that have not been deflated are deflated first.

[0050] Continue in this manner at 10ms intervals until all airbags (P4, P5, P6, and P3) have finished deflating.

[0051] After a 10ms delay, deflate the remaining airbags P1 and P2.

[0052] Furthermore, in the above method, the forward-facing and head-up control mode in quadrant I specifically refers to:

[0053] Sort the pressure values ​​of P4, P5, P6, and P3, and select the airbag corresponding to the maximum value to deflate first;

[0054] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P4, P5, P6, and P3, assign 0X0 to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0055] When the same pressure value is obtained, the airbags are sorted from highest to lowest priority according to P4, P5, P6, and P3, and the airbag with the highest priority is used for deflating.

[0056] When all values ​​are in the 0X0 extreme state, the airbags are sorted in descending order of priority according to P4, P5, P6, P3, and the airbags with higher priority are deflated first.

[0057] Continue in this manner at 10ms intervals until all airbags (P4, P5, P6, and P3) have finished deflating.

[0058] After a 10ms delay, deflate the remaining airbags P1 and P2.

[0059] The advantages of this invention over the prior art are as follows:

[0060] (1) This invention provides a three-plate synchronization method by calculating the difference in AD reference voltage between plates and the rate of change of static pressure height, which can solve the problem of asynchronous airbag inflation commands caused by differences between plates in redundant control systems. It can also be extended to redundant control systems that use static pressure for height parachute opening control.

[0061] (2) The exhaust strategy adopted in this invention takes the forward direction and pitch angle of the return capsule as the main determining factors. It uses the sampling data of the overload X and overload Y directions at the moment of landing to determine the direction of the return capsule at the moment of landing, and uses the sampling values ​​of the airbag pressure in different directions at the moment of landing to determine the pitch attitude of the return capsule.

[0062] (3) The present invention formulates different exhaust strategies according to different modes such as Quadrant III facing forward and tilting up, Quadrant III facing forward and tilting down, Quadrant I facing forward and tilting down, and Quadrant I facing forward and tilting up to accurately control the timing and sequence of exhaust of different airbags, improve the stability and anti-rollover capability of the return capsule landing, and avoid structural damage caused by the return capsule tilting when the horizontal speed is large, the swing angle of the return capsule is too large, or the ground slope is large, thereby ensuring the reusability of the return capsule.

[0063] (4) This invention adds monitoring and interpretation of airbag pressure changes. While ensuring the safety of astronauts by controlling the peak impact overload of the return capsule during the landing buffer process, the exhaust strategy is based on the motion characteristics of the capsule parachute system. The exhaust strategy takes the forward direction and pitch angle of the return capsule as the main determining factors. By judging the combination of overload and pressure, the timing and sequence of exhaust of different airbags are precisely controlled, which improves the stability and anti-rollover ability of the return capsule landing. It avoids structural damage caused by the return capsule tipping over when the horizontal speed is large, the swing angle of the return capsule is too large, or the ground slope is large, thereby ensuring the reusability of the return capsule.

[0064] (5) The airbag of the present invention uses the altitude signal to control inflation at a preset altitude point in the air. In order to achieve high reliability control, the general control system adopts redundant hot backup. The altitude signal is generally the analog signal of the static pressure altitude sensor after AD conversion. Due to the difference of AD reference voltage between multiple control boards, the inflation control command is not synchronized. The present invention provides a three-board synchronization method by calculating the difference of AD reference voltage between boards and the static pressure altitude change rate, which can solve the problem of airbag inflation command not synchronized due to the difference between boards in the redundant control system. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the slowest board synchronization at the detected height point in this invention;

[0066] Figure 2 This is a schematic diagram of the fastest board synchronization for detecting height points according to the present invention;

[0067] Figure 3 This is a schematic diagram of the synchronization signal output in the abnormal state where no synchronization signal is detected according to the present invention;

[0068] Figure 4 This is a schematic diagram of the control system connection of the present invention;

[0069] Figure 5 This is a schematic diagram showing the quadrant definition of the return capsule and the positions of various sensors and airbags in this invention;

[0070] Figure 6 Here is a flowchart of the airbag degassing control process of the present invention; (a) is the main flowchart; (b) is the flowchart of sub-process 1; and (c) is the flowchart of sub-process 2.

[0071] Figure 7 This is a schematic diagram of the synchronization signal and airbag inflation command signal of the present invention. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0073] This invention discloses a method for controlling the inflation and time-sharing deflation of a spacecraft's cushioning airbag, comprising:

[0074] Set the waiting time parameter for the synchronization signal;

[0075] When the spacecraft's airbag reaches the airbag inflation detection altitude, an airbag inflation command is sent according to the waiting synchronization signal time parameter;

[0076] When the overload information reaches a preset threshold, the return capsule is determined to land;

[0077] The attitude of the return capsule is determined. If it is facing forward in quadrant III, the system enters the quadrant III forward-facing exhaust mode; if it is facing forward in quadrant I, the system enters the quadrant I forward-facing exhaust mode. If the attitude is not determined within a predetermined time, all airbags are simultaneously deflated, and the exhaust process ends. Figure 5 As shown.

[0078] The method for determining whether the airbag inflation detection height has been reached is as follows: The height information of static pressure height sensors a to c is sampled and filtered in real time by AD modules 1 to 3, compared with the digital threshold of the control point height, and the result is determined by taking two out of three values ​​and waiting for a certain period of time.

[0079] Based on the valid timing of the waiting synchronization signal, an airbag inflation command is sent, specifically:

[0080] After a single control board determines the airbag inflation height H (m), it sends the "BOARD_SYNC_OUT signal for inter-board synchronization". The synchronization output signals of the three FPGAs are processed by a hardware two-out-of-three logic externally to form the "BOARD_SYNC_IN signal for inter-board synchronization" and input into each FPGA. After a single FPGA reads the two-out-of-three return signal for inter-board synchronization, it is considered that at least two control boards have reached the airbag inflation determination height. At this time, an airbag inflation instruction is sent. The instruction width T_comd is determined according to the ignition performance index of the pyrotechnic device. At the same time, the synchronization signal time parameter T_sync is continuously sent so that the slow board can read the synchronization signal.

[0081] Preferably, the time parameter for waiting for the synchronization signal is specifically:

[0082] T_wait = ΔRef / M

[0083] ΔRef = Max{|Ref1 - Ref2|, |Ref1 - Ref3|, |Ref2 - Ref3|}

[0084] M = V2 - V1

[0085] Among them, T_wait is the longest waiting time for inter-board synchronization; ΔRef is the maximum value of the voltage difference between boards; M is the rate of change of the voltage at the synchronization control point height, which is M; Ref1, Ref2, and Ref3 are the reference voltages of the AD chips of the three boards respectively; V2 is the voltage value corresponding to the atmospheric pressure at a height 0.5 s backward from the control point, and V1 is the voltage value corresponding to the atmospheric pressure at a height 0.5 s forward from the control point.

[0086] Preferably, the method for judging the attitude of the return capsule is specifically:

[0087] When AD1_G_FIT_X < YZ and AD2_G_FIT_X < YZ and AD3_G_FIT_Y > YZ, it is judged that the third quadrant is facing forward;

[0088] When AD1_G_FIT_X > YZ and AD2_G_FIT_X > YZ and AD3_G_FIT_Y < YZ, it is judged that the first quadrant is facing forward;

[0089] Among them, AD1_G_FIT_X is the value after AD sampling and filtering of the X-direction overload at the position of the overload sensor a; AD2_G_FIT_X is the value after AD sampling and filtering of the X-direction overload at the position of the overload sensor b; AD3_G_FIT_Y is the value after AD sampling and filtering of the Y-direction overload at the position of the overload sensor c; YZ is the minimum overload threshold for judging the movement direction.

[0090] Preferably, the exhaust mode with the third quadrant facing forward is specifically:

[0091] If min(PP1,PP2)>max(PP4,PP5), then proceed with the forward-facing and head-up control mode in quadrant III.

[0092] If min(PP4,PP5)>max(PP1,PP2), then proceed to the forward and head-down control mode in quadrant III;

[0093] If the attitude is not determined within the predetermined time, timed exhaust will be performed. Specifically, airbags P1, P2, P3, and P6 will be vented first, and airbags P4 and P5 will be vented after a delay of 30-40ms.

[0094] Preferably, the III quadrant facing forward and head-up control mode is as follows:

[0095] Sort the pressure values ​​of airbags P1, P2, P3, and P6, and select the airbag with the highest value to deflate first;

[0096] After a delay of 10-15ms, refresh the pressure values ​​of airbags P1, P2, P3, and P6 after sampling and filtering. Then, assign 0X 0 to the pressure values ​​of the airbags that have already been deflated and sort them.

[0097] When the same pressure value is obtained, the airbags are sorted in order of priority from largest to smallest according to the order of P1, P2, P3, P6, and the airbag with the highest priority is depressurized first.

[0098] When all values ​​are 0, the airbags are sorted in order of priority from largest to smallest according to the order of P1, P2, P3, P6, and the airbags with the highest priority are deflated first.

[0099] Continue in this manner at 10-15ms intervals until all airbags (P1, P2, P3, and P6) have finished deflating.

[0100] After a delay of 10-15ms, deflate the remaining P4 and P5 airbags.

[0101] Preferably, the III quadrant is facing forward and the head-down control mode is as follows:

[0102] Sort the pressure values ​​of P1, P2, P3, and P6, and select the airbag corresponding to the minimum value to deflate first;

[0103] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P1, P2, P3, and P6, assign 0xFFF to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0104] When the same pressure value is obtained, the airbags P1, P2, P3, and P6 are sorted from highest to lowest priority, and the air is deflated according to the minimum priority value.

[0105] When all values ​​are 0xFFF, the airbags are sorted in order of priority from largest to smallest according to P1, P2, P3, P6, and the airbags with the highest priority that have not been deflated are deflated first.

[0106] Continue in this manner at 10ms intervals until all four airbags (P1, P2, P3, and P6) have finished deflating.

[0107] After a 10ms delay, deflate the remaining P4 and P5 airbags.

[0108] Preferably, the quadrant I front-facing exhaust mode is as follows:

[0109] If min(PP1,PP2)>max(PP4,PP5), then proceed to the forward and head-down control mode in quadrant I;

[0110] If min(PP4,PP5)>max(PP1,PP2), then proceed with the forward-facing and head-up control mode in quadrant I;

[0111] If the attitude is not determined within the predetermined time, timed exhaust will be performed. Specifically, airbags P3, P4, P5, and P6 will be exhausted first, and airbags P1 and P2 will be exhausted after a delay of 30-40ms.

[0112] Preferably, the forward-facing and head-down control mode in quadrant I is as follows:

[0113] Sort the pressure values ​​of P4, P5, P6, and P3, and select the airbag corresponding to the minimum value to deflate first;

[0114] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P4, P5, P6, and P3, assign 0xFFF to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0115] When the same pressure value is obtained, the airbags are sorted from highest to lowest priority according to P4, P5, P6, and P3, and the air is depressurized according to the lowest priority value.

[0116] When all values ​​are 0xFFF, the airbags are sorted in order of priority from largest to smallest according to P4, P5, P6, P3, and the airbags with the highest priority that have not been deflated are deflated first.

[0117] Continue in this manner at 10ms intervals until all airbags (P4, P5, P6, and P3) have finished deflating.

[0118] After a 10ms delay, deflate the remaining airbags P1 and P2.

[0119] Preferably, the quadrant I facing forward and head-up control mode is as follows:

[0120] Sort the pressure values ​​of P4, P5, P6, and P3, and select the airbag corresponding to the maximum value to deflate first;

[0121] After a 10ms delay, refresh the sampled and filtered pressure values ​​of P4, P5, P6, and P3, assign 0X0 to the pressure values ​​of the airbags that have already been deflated, and then sort them.

[0122] When the same pressure value is obtained, the airbags are sorted from highest to lowest priority according to P4, P5, P6, and P3, and the airbag with the highest priority is used for deflating.

[0123] When all values ​​are in the 0X0 extreme state, the airbags are sorted in descending order of priority according to P4, P5, P6, P3, and the airbags with higher priority are deflated first.

[0124] Continue in this manner at 10ms intervals until all airbags (P4, P5, P6, and P3) have finished deflating.

[0125] After a 10ms delay, deflate the remaining airbags P1 and P2.

[0126] Example

[0127] Based on the natural environmental conditions of the landing area and the motion characteristics of the parachute system, the exhaust sequence selection strategy is mainly determined by the forward direction and pitch angle of the reentry capsule. The direction of the reentry capsule is determined by the sampling data of the overload in the X and Y directions at the moment of landing, and the pitch attitude of the reentry capsule is determined by the sampling values ​​of the airbag pressure in different azimuths at the moment of landing. According to different exhaust strategies, the timing and sequence of exhaust of different airbags are precisely controlled to improve the stability and anti-rollover capability of the reentry capsule during landing. This avoids structural damage caused by the reentry capsule tipping over when the horizontal speed is large, the swing angle of the reentry capsule is too large, or the ground slope is large, thereby ensuring the reusability of the reentry capsule.

[0128] like Figure 4 As shown, the control system includes: static pressure altitude sensors a-c, overload sensors a-c, pressure sensors a-f, AD modules 1-9, FPGA chips 1-3, and two sets of 3-out-of-2 circuit modules (used for altitude synchronization and command synchronization respectively). The FPGA internally includes the following software modules: AD sampling, filtering, and detection modules 1-3, a synchronization module, an airbag inflation control module, and an airbag deflation control module. The three overload sensors are mounted on the bottom of the return capsule, with their X, Y, and Z axes parallel to the X, Y, and Z axes of the return capsule, respectively. The positive X-axis of overload sensor a points towards quadrant III of the return capsule, the positive X-axis of overload sensor b points towards quadrant III of the return capsule, and the positive Y-axis of overload sensor c points towards quadrant I of the return capsule.

[0129] The specific connection relationship is as follows: the height simulation signal of static pressure height sensor a, the overload simulation signals of overload sensor a in the X, Y, and Z directions, and the pressure simulation signals of pressure sensors a and b are output to FPGA1 through AD1 chip, to FPGA2 through AD4 chip, and to FPGA3 through AD7 chip.

[0130] The static pressure height sensor b's height analog signal, the overload sensor b's overload analog signals in the X, Y, and Z directions, and the pressure analog signals of pressure sensors c and d are output to FPGA1 through the AD2 chip, to FPGA2 through the AD5 chip, and to FPGA3 through the AD8 chip.

[0131] The static pressure height sensor c's height analog signal, the overload sensor c's overload analog signals in the X, Y, and Z directions, and the pressure analog signals from pressure sensors e and f are output to FPGA1 via the AD3 chip, to FPGA2 via the AD6 chip, and to FPGA3 via the AD9 chip.

[0132] The AD sampling and filtering detection modules 1-3 of FPGA1-3 drive the AD conversion chip and output the information after sampling and filtering the digital signal to the airbag inflation control module. After the airbag inflation control module detects the inflation height point, it enables the synchronization module to output the synchronization signal to the synchronization three-out-of-two circuit. Based on the signal after synchronization return, it outputs the airbag inflation command to the command three-out-of-two circuit.

[0133] The AD sampling, filtering and detection modules 1-3 of FPGA1-3 drive the AD conversion chip and output the information after sampling and filtering the digital signal to the airbag exhaust control module. The airbag exhaust control module outputs the airbag exhaust command to the instruction three-out-of-two circuit according to the exhaust strategy.

[0134] like Figure 6 As shown, this embodiment provides a method for controlling the inflation and time-sharing deflation of a spacecraft's airbag, comprising the following steps:

[0135] Step 1: During the return capsule's descent, the three FPGAs drive their corresponding AD chips in real time to read three channels of hydrostatic altitude information. Due to the redundant power supply structure of the control system, the reference voltages of the AD modules corresponding to the three FPGAs are different. The airbag inflation altitude control point is H(m). The theoretical voltage at altitude point H(m) is calculated according to the AD reference voltage. By inputting the theoretical voltage, the AD voltage output values ​​corresponding to the three FPGAs are tested: AD1~AD3 voltage is Ref1, AD4~AD6 voltage is Ref2, and AD7~AD9 voltage is Ref3. The maximum voltage difference is ΔRef={|Ref1-Ref2|、|Ref1-Ref3|、|Ref2-Ref3|}. At control point H(m), the velocity of the return capsule is V(m / s). Based on the theoretical reference voltage, the voltage change rate at this point is M(V / s). This can be calculated using the standard atmospheric calculation formula or by referring to the table in the National Military Standard "Altitude and Pressure Conversion Table GJB365.2-87". Calculate the atmospheric pressure P1 at HV / 2 and the atmospheric pressure P2 at H+V / 2. Based on the voltage and pressure relationship formula of the static pressure altitude sensor, calculate V1 corresponding to P1 and V2 corresponding to P2. M = V2 - V1. The timing difference of the altitude points sampled by the three FPGAs is ΔRef / M. Design a synchronization mechanism to ensure that the effective width of the airbag inflation command output by the FPGA, after taking two out of three, can meet the ignition requirements. In the program parameter list, the waiting time parameter T_wait = ΔRef / M for the synchronization signal is set, and the continuous sending time parameter T_sync = ΔRef / M for the synchronization signal is set. When the program samples and filters the three analog height signals and reaches the discrimination point H, it sends the "inter-board synchronization output signal BOARD_SYNC_OUT". The synchronization output signals of the three FPGAs are processed externally using a hardware 3-out-of-2 logic to form the "inter-board synchronization return signal BOARD_SYNC_IN", which is then input to each FPGA. When a single FPGA reads the inter-board synchronization 3-out-of-2 return signal, it considers that at least two control boards have reached the airbag inflation discrimination height. At this time, it sends an airbag inflation command. The command width T_comd is determined according to the ignition performance index of the pyrotechnics. At the same time, the synchronization signal time parameter T_sync is continuously sent so that the slower board can read the synchronization signal. Figures 1-3 As shown.

[0136] The following are two scenarios: normal and abnormal.

[0137] (a) Within a time period less than or equal to T_wait, if BOARD_SYNC_IN is read low three times consecutively at 1ms intervals, it is considered that the height signal boards have achieved synchronization. At the same time, the timing T_sync continuously sets the BOARD_SYNC_OUT signal to "1". See the timing diagram. Figure 1 and Figure 2 ;

[0138] (b) Conversely, if the time exceeds T_wait and BOARD_SYNC_IN cannot be read low three times consecutively, the program also considers the altitude signal boards to be synchronized, and the timer T_sync continuously sets the BOARD_SYNC_OUT signal to "1". This indicates that the asynchronous time between this control board and the other two control boards exceeds T_wait, or that the synchronization signal line is faulty. Based on the ballistic altitude change rate, the former scenario is extremely unlikely. If it does occur, this control board may be the fastest or slowest control board. See the timing diagram below. Figure 3 Even in the event of this malfunction, the other two FPGAs can still issue airbag inflation commands normally.

[0139] Step Two: After sending the airbag inflation command, the program uses overload information to determine whether to land.

[0140] The use of overload information to determine "landing" has been discussed in the patent applicant's paper "FPGA Design of Landing Buffer Control System Based on Active Exhaust Airbag" and is not within the scope of the claims of this patent. Here, it is only briefly described. The overload information in the XYZ directions is used to determine the landing according to a pre-set threshold. Once the threshold is reached, the return capsule is considered to have landed, and the process proceeds to step three.

[0141] Step 3: Using the X-axis overload filter value AD1_G_FIT_X from sensor a, the X-axis overload filter value AD2_G_FIT_X from sensor b, and the Y-axis overload filter value AD3_G_FIT_Y from sensor c, determine whether the reentry capsule is facing forward in quadrant III or quadrant I. This determination process is protected by time Tp (30ms from the start of the venting module activation after landing determination). Within time Tp, the overload filter value is refreshed every 600µs for continuous determination.

[0142] a) When two of the three conditions are met, the X-direction overload filter value AD1_G_FIT_X < 1g, the X-direction overload filter value AD2_G_FIT_X < 1g, and the Y-direction overload filter value AD3_G_FIT_Y > 1g, it is determined that the III quadrant is facing forward, and then proceed to step four.

[0143] b) When two of the three conditions are met, the X-direction overload filter value AD1_G_FIT_X of sensor a > 1g, the X-direction overload filter value AD2_G_FIT_X of sensor b > 1g, and the Y-direction overload filter value AD3_G_FIT_Y of sensor c < 1g, it is determined that quadrant I is facing forward and backward, and proceed to step five.

[0144] c) If the timeout fails to determine whether quadrant III or quadrant I is facing forward, all six airbags will deflate simultaneously, the airbag deflation command will be output to the command 3-out-of-2 circuit, and the deflation process will end.

[0145] Step Four:

[0146] In the forward-facing mode of Quadrant III, the relative pressure values ​​of the P4 airbag (AD2_P_FIT_B) and P5 airbag (AD3_P_FIT_A) in Quadrant III, and the P1 airbag (AD1_P_FIT_A) and P2 airbag (AD1_P_FIT_B) in Quadrant I, are used to determine whether the reentry capsule is in a pitched-up or pitched-down state. This determination is protected by a 10ms timeout (starting from the activation of the exhaust module after landing is determined). During this protection time, the overload filter value is refreshed every 600µs for continuous assessment.

[0147] a) When the filtered airbag pressure values ​​P1 and P2 are greater than P4 and P5, it is determined to be the III quadrant facing forward and head-up mode, and proceed to step six.

[0148] b) When the filtered airbag pressure values ​​P4 and P5 are greater than P1 and P2, it is determined to be the III quadrant facing forward and head-down mode, and proceed to step seven.

[0149] c) If the attitude is not determined after the timeout, the timed exhaust will be performed directly: exhaust airbags P1, P2, P3 and P6 first, and after a delay of 30ms, exhaust airbags P4 and P5. The airbag exhaust command is output to the command three-out-of-two circuit, and the exhaust program ends.

[0150] Step 5:

[0151] In the forward-facing mode of Quadrant I, the relative pressure values ​​of the P4 airbag (AD2_P_FIT_B) and P5 airbag (AD3_P_FIT_A) in Quadrant III, and the pressure values ​​of the P1 airbag (AD1_P_FIT_A) and P2 airbag (AD1_P_FIT_B) in Quadrant I, are used to determine whether the reentry capsule is in a pitched-up or pitched-down state. This determination is protected by a 10ms timeout (starting from the activation of the exhaust module after landing is determined). During this protection time, the overload filter value is refreshed every 600µs for continuous assessment.

[0152] a) When the filtered airbag pressure values ​​P1 and P2 are greater than P4 and P5, it is determined to be in quadrant I facing forward and head-down mode, and proceed to step eight.

[0153] b) When the filtered airbag pressure values ​​P4 and P5 are greater than P1 and P2, it is determined to be the forward-facing and head-up mode in quadrant I, and proceed to step nine.

[0154] c) If the attitude is not determined after the timeout, the timed exhaust will be performed directly: exhaust airbags P3, P4, P5 and P6 first, and after a 30ms delay, exhaust airbags P1 and P2. The airbag exhaust command is output to the command three-out-of-two circuit, and the exhaust program ends.

[0155] Step Six:

[0156] The system determines the forward-facing and head-up mode in quadrant III. It sorts the pressure values ​​of airbags P1, P2, P3, and P6, selecting the airbag with the highest pressure value to deflate first. After a 10ms delay, it refreshes the sampled and filtered pressure values ​​of P1, P2, P3, and P6. The pressure values ​​of the deflated airbags are assigned 0x0 and then sorted. When identical pressure values ​​appear, the larger value is selected based on priority: P1>P2>P3>P6. When all values ​​are at the 0x0 limit (a fault), the airbags that haven't been deflated are deflated according to priority: P1>P2>P3>P6. This process is repeated every 10ms until all four airbags have been deflated. Finally, after a 10ms interval, the remaining airbags (numbers 4 and 5) are deflated. The airbag deflation command is output to the 3-out-of-2 instruction circuit, and the deflation process ends.

[0157] Step Seven:

[0158] The system determines that the airbags in quadrant III are facing forward and in a tilted-down mode. It sorts the pressure values ​​of P1, P2, P3, and P6, selecting the airbag with the lowest pressure value to deflate first. After a 10ms delay, it refreshes the sampled and filtered pressure values ​​of P1, P2, P3, and P6. The pressure values ​​of the deflated airbags are assigned 0xFFF and then sorted. When identical pressure values ​​appear, the smallest value is selected based on priority: P1>P2>P3>P6. When all values ​​reach the 0xFFF limit (a fault), the airbags that have not yet been deflated are deflated according to priority: P1>P2>P3>P6. This process is repeated every 10ms until all four airbags have been deflated. Finally, after a 10ms interval, the remaining airbags (numbers 4 and 5) are deflated. The airbag deflation command is output to the three-out-of-two command circuit, and the deflation procedure ends.

[0159] Step 8:

[0160] The system determines that the airbags in quadrant I are facing forward and in a tilted-down mode. It sorts the pressure values ​​of P4, P5, P6, and P3, selecting the airbag with the lowest pressure value to deflate first. After a 10ms delay, it refreshes the sampled and filtered pressure values ​​of P4, P5, P6, and P3. The pressure values ​​of the deflated airbags are assigned 0xFFF and then sorted. When identical pressure values ​​appear, the smallest value is selected based on priority: P4 > P5 > P6 > P3. When all values ​​reach the 0xFFF limit (a fault), the airbags that have not yet been deflated are deflated based on priority: P4 > P5 > P6 > P3. This process is repeated every 10ms until all four airbags have been deflated. Finally, after a 10ms interval, the remaining airbags (numbers 1 and 2) are deflated. The airbag deflation command is output to the instruction 3-out-of-2 circuit, and the deflation procedure ends.

[0161] Step Nine:

[0162] The system determines the quadrant I is facing forward and in a head-up mode. It sorts the pressure values ​​of P4, P5, P6, and P3, selecting the airbag with the highest value to deflate first. After a 10ms delay, it refreshes the sampled and filtered pressure values ​​of P4, P5, P6, and P3. The pressure values ​​of the deflated airbags are assigned 0x0 and then sorted. When identical pressure values ​​appear, the larger value is selected based on priority: P4 > P5 > P6 > P3. When all values ​​are at the 0x0 limit (fault), the airbags that haven't been deflated are deflated based on priority: P4 > P5 > P6 > P3. This process is repeated every 10ms until all four airbags have been deflated. Finally, after a 10ms interval, the remaining airbags (numbers 1 and 2) are deflated. The airbag deflation command is output to the instruction 3-out-of-2 circuit, and the deflation process ends.

[0163] Specific implementation method of airbag inflation control: The AD chip used is B128S102RH, with a reference voltage of 5V and a digital length of 12 bits. It reads three channels of static pressure height information. The correspondence between the voltage of the selected static pressure height sensor and the static pressure is based on the following formula:

[0164]

[0165] The airbag inflation altitude control point is H = 2800m. Referring to the "Altitude Pressure Conversion Table GJB365.2-87", the corresponding pressure is 71.91 kPa, and the theoretical voltage is 2.996 V. The maximum voltage difference between the AD circuits corresponding to the three FPGAs at altitude H (m) is 0.007 V. The return capsule speed at control point H (m) is 10 (m / s). Centered on 2800m, referring to the table, the pressure change from 2795m to 2805m is 0.1 kPa, corresponding to a voltage change of M (V / s) = 0.004 V / s. In the program parameter list, T_wait = 1.75s, T_sync = 1.75s. When the sampling and filtering of the three analog height signals reaches the discrimination point H, the program sends the "inter-board synchronization output signal BOARD_SYNC_OUT" in the T_comd=0.8s timer. The synchronization output signals of the three FPGAs are processed externally by hardware three-out-of-two logic to form the "inter-board synchronization return signal BOARD_SYNC_IN" which is input to each FPGA. After a single FPGA reads the inter-board synchronization three-out-of-two return signal, it considers that at least two control boards have reached the airbag inflation discrimination height, sends the airbag inflation command, and continuously sends a synchronization signal with a width of T_sync to ensure that the width of the airbag inflation command in the external three-out-of-two command meets the requirements. Figure 7 A schematic diagram is given for the synchronization signal where the reference voltage of plate C > the reference voltage of plate A > the reference voltage of plate B, and the airbag inflation command signal, as shown below. Figure 7 As shown.

[0166] Provide an implementation case study of Quadrant III advanced and head-down mode:

[0167] X-axis overload of overload sensor a: 12'd2063;

[0168] Y-axis overload of overload sensor a: 12'd1646;

[0169] Z-axis overload of overload sensor a: 12'd2711;

[0170] X-axis overload of overload sensor b: 12'd2449

[0171] Y-axis overload of overload sensor b: 12'd1646

[0172] Z-axis overload of overload sensor b: 12'd2711

[0173] X-axis overload of overload sensor c: 12'd2449

[0174] Y-axis overload of overload sensor c: 12'd1646

[0175] Z-axis overload of overload sensor c: 12'd2711

[0176] Pressure sensor a: 12'd1234

[0177] Pressure sensor b: 12'd1235

[0178] Pressure sensor c: 12'd1236

[0179] Pressure sensor d: 12'd1237

[0180] Pressure sensor e: 12'd1238

[0181] Pressure sensor f: 12'd1239

[0182] Results of airbag deflation sequence:

[0183] P1

[0184] 10ms delay P2

[0185] 10ms delay P3

[0186] 10ms delay P6

[0187] 10ms delay for P4 and P5

[0188] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0189] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for controlling the inflation and time-delayed venting of a spacecraft cushion airbag, comprising: It comprises the following steps: Setting a waiting synchronization signal time parameter; When the spacecraft buffer air bag reaches the air bag inflation judgment height, sending the air bag inflation instruction according to the waiting synchronization signal time parameter; When the overload information reaches the pre-set threshold, judging the return capsule landing; Judging the attitude of the return capsule, if it is in the III quadrant and faces forward, entering the III quadrant and facing forward exhaust mode; If it is in the I quadrant and faces forward, entering the I quadrant and facing forward exhaust mode; if the attitude is not judged out within a predetermined time, controlling all air bags to exhaust at the same time, and ending the exhaust; The waiting synchronization signal time parameter is specifically: T_wait = ΔRef / M ΔRef = Max{|Ref1-Ref2|, |Ref1-Ref3|, |Ref2-Ref3|} M = V2-V1 Wherein, T_wait is the longest waiting time between boards for synchronization; ΔRef is the maximum value of the voltage difference between boards; M is the rate of change of voltage at the synchronization control point height; Ref1, Ref2, Ref3 are the reference voltages of the three board AD chips respectively; V2 is the voltage value corresponding to the atmospheric pressure at the height of 0.5s backward from the control point, and V1 is the voltage value corresponding to the atmospheric pressure at the height of 0.5s forward from the control point; The specific method for judging the attitude of the return capsule is: When AD1_G_FIT_X<YZ and AD2_G_FIT_X<YZ and AD3_G_FIT_Y>YZ, it is judged to be in the III quadrant and faces forward; When AD1_G_FIT_X>YZ and AD2_G_FIT_X>YZ and AD3_G_FIT_Y<YZ, it is judged to be in the I quadrant and faces forward; Wherein, AD1_G_FIT_X is the AD sampling and filtering value of the overload sensor a position X to the overload; AD2_G_FIT_X is the AD sampling and filtering value of the overload sensor b position X to the overload; AD3_G_FIT_Y is the AD sampling and filtering value of the overload sensor c position Y to the overload; YZ is the minimum overload threshold value that can judge the direction of movement; The III quadrant and facing forward exhaust mode is specifically: If min(PP1, PP2)>max(PP4, PP5), the III quadrant and facing forward and head-up control mode is performed; If min(PP4, PP5)>max(PP1, PP2), the III quadrant and facing forward and head-down control mode is performed; If the attitude is not judged out within a predetermined time, time-sharing exhaust is performed, specifically: air bags P1, P2, P3 and P6 are exhausted first, and air bags P4 and P5 are exhausted after a delay of 30-40ms; The I quadrant and facing forward exhaust mode is specifically: If min(PP1, PP2)>max(PP4, PP5), the I quadrant and facing forward and head-down control mode is performed; If min(PP4, PP5)>max(PP1, PP2), the I quadrant and facing forward and head-up control mode is performed; If the attitude is not judged out within a predetermined time, time-sharing exhaust is performed, specifically: air bags P3, P4, P5 and P6 are exhausted first, and air bags P1 and P2 are exhausted after a delay of 30-40ms.

2. The method of claim 1, wherein: The III quadrant and facing forward and head-up control mode is specifically: The air bags P1, P2, P3, P6 pressure value ordering, select the maximum value corresponding to the air bag first exhaust; Delay 10~15ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0X0 and then sorted; When the same pressure value appears, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with high priority is exhausted first; When all values are 0 limit state, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with high priority is exhausted first; According to the interval of 10~15ms, the P1, P2, P3, P6 air bags are exhausted in turn until all the air bags are exhausted. Delay 10~15ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0X0 and then sorted; 3. The spacecraft cushion airbag inflation and time-divided venting control method according to claim 2, wherein: The Ⅰ quadrant forward and low head control mode, specifically: The P1, P2, P3, P6 pressure value ordering, select the minimum value corresponding to the air bag first exhaust; Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0XFFF and then sorted; When the same pressure value appears, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with minimum priority is exhausted first; When all values are 0XFFF limit state, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with high priority is exhausted first. According to the interval of 10ms, the P1, P2, P3, P6 air bags are exhausted in turn until all the air bags are exhausted. Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0X0 and then sorted; 4. The spacecraft cushion airbag inflation and time-divided venting control method according to claim 3, wherein: The Ⅰ quadrant forward and low head control mode, specifically: The P1, P2, P3, P6 pressure value ordering, select the minimum value corresponding to the air bag first exhaust; Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0XFFF and then sorted; When the same pressure value appears, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with minimum priority is exhausted first; When all values are 0XFFF limit state, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with high priority is exhausted first. According to the interval of 10ms, the P1, P2, P3, P6 air bags are exhausted in turn until all the air bags are exhausted. Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0X0 and then sorted; 5. The method of claim 4, wherein: The Ⅰ quadrant forward and low head control mode, specifically: The P1, P2, P3, P6 pressure value ordering, select the minimum value corresponding to the air bag first exhaust; Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0XFFF and then sorted; When the same pressure value appears, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with minimum priority is exhausted first; When all values are 0XFFF limit state, the priority of the air bag P1, P2, P3, P6 is sorted from large to small, and the air bag with high priority is exhausted first. According to the interval of 10ms, the P1, P2, P3, P6 air bags are exhausted in turn until all the air bags are exhausted. Delay 10ms, refresh sampling filter after P1, P2, P3, P6 pressure value, the corresponding pressure value of the air bag which has been exhausted is assigned 0X0 and then sorted; When the limit state of all values being 0X0 occurs, the priority is sorted from large to small in the order of airbag P4, P5, P6, P3, and the un-vented airbag with large priority is preferentially vented; In the same way, the interval is 10 ms, until the airbags P4, P5, P6, P3 are all vented; Delay 10 ms, and vent the remaining airbags P1 and P2.

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