Method for controlling a propulsion system of an extruded rocket engine

Abstract

The application discloses a control method of a propelling system of an extrusion rocket engine, which comprises steps S1-S8. The application pre-plans nitrogen pressurization timing, simultaneously returns combustion chamber temperature, storage tank pressure, nitrogen cylinder pressure and thrust multidimensional data to a nitrogen pressurization timing control module, dynamically updates a next period pre-pressurization starting moment, forms a whole-process millisecond-level closed-loop iterative control, solves the problems of large starting pressurization impact and thrust peak overshoot of a traditional fixed timing, and adapts to multiple nonlinear disturbances such as nitrogen pressure attenuation and pipeline pressure drop changes. The system does not need an accurate system mathematical model, has low parameter debugging workload, and is suitable for multiple types of extrusion propelling systems. The application adopts a barycenter method to output continuous high-precision regulating quantity, simultaneously uniformly limits the output regulating quantity, eliminates extreme working conditions of valve full opening and full closing, reduces thrust regulating overshoot, and greatly reduces pipeline instantaneous flow impact.

Description

Technical Field

[0001] This invention relates to propulsion control technology for liquid extrusion rocket engines, and is particularly applicable to closed-loop control of extrusion-type, nitrogen-pressurized variable thrust rocket engines, belonging to the field of aerospace propulsion automatic control technology. Background Technology

[0002] Squeeze-type liquid rocket engines rely on high-pressure nitrogen gas to squeeze the propellant tank, delivering fuel and liquid oxygen to the combustion chamber for combustion. They offer advantages such as simple structure, high reliability, and multiple restart capabilities, and are widely used in sounding rockets, small launch vehicles, and landing descent stage engines. However, existing squeeze-type propulsion system control schemes have several inherent drawbacks: 1. Existing technology does not take into account the pressure decay caused by continuous venting of high-pressure nitrogen cylinders and the pressure fluctuation of the storage tank. The propellant flow rate has a non-linear relationship with the cylinder and tank pressures, and the controller cannot identify and compensate for nitrogen pressure changes in advance. The thrust fluctuation is large throughout the process, the mixture ratio deviates from the design value continuously, and problems such as fuel-rich carbon buildup, delayed oscillation, and oxygen-enriched injector ablation are very likely to occur. 2. Existing fuzzy control quantization mostly adopts segmented fixed threshold segmented mapping. The mapping rules for different working condition variables such as thrust deviation and pressure deviation are not uniform, the interval division is rigid, and there are abrupt breaks in the conversion of the original measured working condition values ​​to fuzzy discrete gears, which leads to distortion of the input data of the fuzzy controller and directly reduces the thrust adjustment accuracy. 3. Sudden changes in the output of the existing controller drive the fuel, liquid oxygen metering valve, and nitrogen booster valve to reciprocate at high frequency with small amplitude movements, resulting in pipeline flow oscillations, inducing low-frequency combustion instability in the combustion chamber, and shortening the service life of valves and injectors. 4. Existing solutions mostly use simple defuzzification algorithms, resulting in discrete output adjustment quantities and low accuracy. During the adjustment process, valves are prone to extreme conditions of being fully open or fully closed, resulting in large overshoot of thrust adjustment and large instantaneous flow impact in pipelines, which disrupts the stability of the supply system. 5. Most existing control strategies independently control the opening of the fuel electromagnetic metering valve and the liquid oxygen electromagnetic metering valve. During the thrust increase and decrease, the liquid oxygen to fuel flow ratio deviates from the rated design ratio in real time, the staged combustion condition in the combustion chamber continues to deteriorate, and the combustion efficiency decreases. 6. Traditional control methods have a fixed nitrogen pre-pressurization start-up sequence, which cannot be dynamically adjusted according to real-time operating conditions. Furthermore, they only collect single-point thrust data for simple feedback, and key parameters such as combustion chamber temperature, tank pressure, and nitrogen cylinder pressure are not fed back to the timing control link. This results in a large boost pressure surge and significant thrust peak overshoot during engine start-up, and the system has weak adaptive adjustment capability when faced with nitrogen decay and changes in pipeline pressure drop.

[0003] In summary, existing control methods for squeeze-type rocket propulsion systems suffer from multiple defects, including large thrust drift, quantization mapping distortion, boundary adjustment jitter, fuel-oxygen ratio imbalance, low defuzzification accuracy, and lack of adaptive timing correction. These shortcomings make it difficult to meet the requirements of high-precision, long-term stable variable thrust aerospace propulsion systems. Summary of the Invention

[0004] To overcome the shortcomings mentioned above, the present invention aims to provide a technical solution that can solve the above problems.

[0005] A control method for a propulsion system of a squeeze-type rocket engine includes the following steps.

[0006] S1. Nitrogen timing pre-control: retrieves multi-dimensional sensor data of nitrogen cylinder pressure, fuel tank pressure, and liquid oxygen tank pressure from the previous cycle, and dynamically corrects the nitrogen pre-pressurization delay and conduction time for the current cycle; it iterates operating parameters such as thrust and combustion chamber temperature to the timing module in a closed loop, buffering sudden pressure changes in advance, significantly reducing the pressure shock and thrust peak at engine start-up, and improving the system's adaptability to slow nitrogen depressurization and pipeline pressure drop disturbances; S2. Real-time acquisition of multiple parameters, calculation of three sets of fuzzy input variables, and addition of nitrogen pressure coupling deviation as the third independent input, directly converting nitrogen cylinder attenuation and tank pressure fluctuation into controller input signals, synchronously acquiring real-time thrust deviation and deviation change trend, and capturing steady-state offset and dynamic change trend, providing complete original disturbance data for three-dimensional coupled fuzzy inference, and identifying nitrogen pressure disturbance in advance from the input level; S3. The linear mapping formula is used to complete the normalized discrete mapping of input and output variables, unify the linear continuous mapping rules, and achieve seamless smooth quantization of physical quantities with different dimensions and different domains, such as thrust and pressure. The numerical jump distortion caused by segmented thresholds is eliminated, ensuring the continuous and stable fuzzy input signal and improving the accuracy of subsequent fuzzy inference calculation and the precision of thrust steady-state control. S4. Using a smooth Gaussian function as the main membership function and a bell-shaped membership function for the boundary, a membership mapping is established for deviation, deviation change rate, and adjustment amount. In the steady-state intermediate range, a Gaussian function is used to ensure smooth adjustment without jitter. At the limit boundary of the operating condition, the bell-shaped function is switched to smoothly transition the output, suppressing sudden changes in output. The three inputs are independently parameterized and do not interfere with each other, completely eliminating the small-amplitude high-frequency reciprocating action of the metering valve and nitrogen booster valve, reducing pipeline flow pulsation, suppressing low-frequency unstable combustion in the combustion chamber, and extending the service life of injection and valves. S5. Based on the 7×7 basic thrust fuzzy rule library and the nitrogen pressure compensation logic, three-dimensional fuzzy reasoning is completed. On the basis of the two-dimensional thrust rules, the three-dimensional nitrogen pressure compensation logic is introduced to simultaneously offset the flow deviation caused by the continuous depressurization of the nitrogen cylinder. The output is dynamically corrected and adjusted according to the nitrogen pressure deviation, thereby stabilizing the combustion chamber oxygen-fuel mixture ratio and avoiding carbon buildup and injection erosion failures. S6. The centroid method is used to solve the fuzzy calculation formula to calculate the adjustment amount u with nitrogen compensation. The centroid method outputs a continuous high-precision simulated adjustment amount. Combined with the output limiting constraint, it eliminates the extreme fully open / fully closed conditions of valves. The thrust step adjustment overshoot is greatly reduced, the instantaneous flow impact in the pipeline is weakened, and the long-term stability of the propulsion supply system is maintained. It solves the problems of easy full opening and closing of valves, large thrust overshoot, and severe instantaneous flow impact in the pipeline. S7. Synchronously adjust the opening of the fuel and liquid oxygen electromagnetic metering valves, and synchronously adjust the nitrogen booster valves of the fuel tank and liquid oxygen tank to compensate for the pressure drop of the high-pressure nitrogen cylinder. The fuel and liquid oxygen metering valves are linked synchronously in proportion to eliminate valve response time difference. The rated chemical ratio is maintained throughout the thrust rise and fall process. The two nitrogen booster valves are linked synchronously to compensate for cylinder pressure drop in real time. The mixture ratio is stabilized from two layers: propellant supply and tank extrusion pressure, which improves the staged combustion efficiency of the combustion chamber. S8: The propellant enters the combustion chamber and undergoes staged combustion. Sensors continuously collect data and return it to S1 to form a closed-loop control. After combustion, the thrust, tank pressure, cylinder pressure, and combustion chamber temperature are all transmitted back to the nitrogen timing pre-control module in S1 in real time, forming a millisecond-level full closed-loop iteration. The pre-pressurization timing is dynamically updated for the next cycle each cycle, continuously reducing the start-up impact and enhancing the system's adaptive capability to nonlinear disturbances such as nitrogen decay and pipeline pressure drop. No precise mathematical model is required, and the engineering debugging workload is low. Preferably, the nitrogen timing pre-control includes: The remaining pressure of the high-pressure nitrogen cylinder, the real-time pressure of the fuel tank, and the real-time pressure of the liquid oxygen tank are retrieved from the sensor feedback of the previous closed-loop cycle. The nitrogen pre-pressurization start-up delay and continuous conduction duration of the current control cycle are planned in advance, and the timing parameters are pre-stored for back-end closed-loop iterative correction to reduce the boost shock and thrust peak overshoot during the engine start-up phase. Preferably, the calculation of the three sets of fuzzy input variables is as follows: Thrust deviation S(c), thrust deviation change rate Se(i) = S(c) - S(c-1), nitrogen pressure coupling deviation N(p); Where -50≤S(c)≤50, -25≤Se(i)≤25, -20≤N(p)≤20; Preferably, in S2, the formula for the linear mapping is:

[0007] Where n is a discrete hierarchical variable, and the set of values ​​for the discrete hierarchical variable is n∈{-3,-2,-1,0,1,2,3}; where X represents the original measured working condition variable, a is the lower limit of the domain of the corresponding variable, and b is the upper limit of the domain of the corresponding variable. Preferably, the smooth Gaussian function is expressed as follows:

[0008] in, σ is the membership function center value, and σ is the Gaussian function width coefficient; The bell-shaped membership function is:

[0009] Where c is the half-width parameter and b is the curvature adjustment coefficient; Preferably, the 7×7 basic thrust fuzzy rule includes: The seven-level fuzzy linguistic variables NB, NM, NS, ZO, PS, PM, and PB are used to represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively. When the thrust deviation and the thrust deviation change rate reach their extreme values ​​in the same direction, the output is the maximum reverse adjustment amount; when they reach their extreme values ​​in opposite directions, the output is the maximum positive adjustment amount. The smaller the deviation and the smoother the change, the closer the output adjustment amount is to zero. Preferably, the nitrogen pressure compensation logic is as follows: If the nitrogen pressure coupling deviation N(p) is NB, the nitrogen boost compensation is positively superimposed under the same thrust deviation, and the nitrogen boost valves of the fuel tank and liquid oxygen tank are opened simultaneously; if the nitrogen pressure coupling deviation N(p) is PB, the nitrogen boost output is reduced in the opposite direction, and the two nitrogen boost valves are closed simultaneously; when N(p) is ZO, no compensation is superimposed, and only the basic thrust adjustment output is executed. Preferably, the specific process of the three-dimensional fuzzy inference is as follows: The first step is to substitute the thrust deviation S(c) and the thrust deviation change rate Se(i) into the 7×7 basic thrust rule base to calculate the basic adjustment fuzzy subset; The second step is to introduce a nitrogen pressure coupling deviation N(p), and the nitrogen pressure compensation logic performs amplitude correction on the basic adjustment fuzzy subset. The third step is to take the union of the corrected multi-channel fuzzy subsets to obtain the final integrated output fuzzy set; Preferably, the centroid method for fuzzy resolution is calculated as follows:

[0010] Wherein, μN(x) is the composite membership function of the output adjustment after nitrogen pressure compensation; Preferably, the method for adjusting the opening of the fuel and liquid oxygen electromagnetic metering valve is as follows: The adjustment amount u synchronously and proportionally adjusts the flow opening of the fuel electromagnetic metering valve and the liquid oxygen electromagnetic metering valve, keeping the adjustment amplitudes of the two valves matched to maintain the real-time oxygen-fuel ratio of fuel and liquid oxygen within the preset allowable range. When the adjustment amount u is positive, the two valves are opened synchronously to increase the propellant flow rate, and when the adjustment amount u is negative, the two valves are closed synchronously to reduce the propellant flow rate. The synchronous action throughout the process eliminates the ratio imbalance caused by the response time difference of the two valves.

[0011] Compared with the prior art, the advantages of the present invention are: This invention introduces nitrogen pressure coupling deviation as a third input, and superimposes nitrogen pressure compensation logic on the basis of two-dimensional thrust rule base to realize three-dimensional coupled fuzzy reasoning. At the same time, it synchronously adjusts the nitrogen pressurization valve of the storage tank to actively compensate for the continuous pressure relief of the nitrogen cylinder. The dual mechanism offsets the thrust offset caused by nitrogen decay, so that the propellant mixing ratio is stably maintained near the design value, avoiding fuel-rich and oxygen-rich combustion failures.

[0012] This invention employs a standardized linear mapping formula to continuously map measured physical quantities such as thrust and pressure from different domains to seven unified discrete intervals. The mapping process is seamless, solving the input distortion problem inherent in traditional segmented threshold quantization, improving the consistency of fuzzy inference input data, and significantly enhancing thrust adjustment accuracy.

[0013] This invention employs a smooth Gaussian membership function in the middle interval of the domain to ensure smooth steady-state regulation, and a bell-shaped membership function for switching at the limit boundary to smoothly transition the output, avoiding sudden changes in the controller output under boundary conditions. This effectively eliminates high-frequency reciprocating jitter of metering valves and booster valves, suppresses pipeline flow oscillations and low-frequency combustion instability in the combustion chamber, and extends the service life of valves and injectors.

[0014] This invention uses the center of gravity method to output continuous high-precision adjustment, which is different from the traditional simple defuzzification of taking the larger / smaller value; at the same time, it uniformly limits the output adjustment value, eliminates extreme working conditions of valves being fully open or fully closed, reduces the overshoot of thrust adjustment, and significantly reduces the instantaneous flow impact in the pipeline.

[0015] This invention synchronously and proportionally adjusts the opening of the electromagnetic metering valves for fuel and liquid oxygen, maintaining the rated oxygen-fuel ratio throughout the thrust increase and decrease process, solving the problem of ratio imbalance caused by traditional independent adjustment, and optimizing the staged combustion efficiency of the combustion chamber.

[0016] This invention pre-plans the nitrogen pressurization sequence and simultaneously feeds back multi-dimensional data such as combustion chamber temperature, tank pressure, nitrogen cylinder pressure, and thrust to the nitrogen pressurization sequence control module, dynamically updating the pre-pressurization start time for the next cycle. This forms a millisecond-level closed-loop iterative control throughout the entire process, solving the problems of large start-up pressurization impact and thrust peak overshoot in traditional fixed-sequence pressurization systems. The system can adapt to multiple nonlinear disturbances such as nitrogen pressure decay and pipeline pressure drop changes, without requiring a precise system mathematical model, resulting in low parameter debugging workload and compatibility with various types of extrusion propulsion systems.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram illustrating the working principle of the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Please see Figure 1 In this embodiment of the invention, a control method for a propulsion system of a squeeze-type rocket engine includes the following steps.

[0025] S1, Nitrogen timing pre-control, plans the nitrogen pressurization timing in advance, providing a basis for back-end closed-loop correction, and achieves dynamic timing adjustment in conjunction with S8 feedback; this step retrieves the high-pressure nitrogen cylinder pressure, fuel tank pressure, and liquid oxygen tank pressure of the previous closed-loop cycle, dynamically calculates the nitrogen pre-pressurization delay and conduction duration of the current cycle, and iterates back parameters such as thrust and combustion chamber temperature to buffer the pressurization impact in advance, solving the problems of thrust spikes and large pressurization impacts in traditional fixed-timing start-up, and improving the system's resistance to nitrogen decay disturbances.

[0026] S2. Real-time acquisition of multiple parameters, calculation of three sets of fuzzy input variables; the calculation of the three sets of fuzzy input variables is as follows: Thrust deviation S(c), thrust deviation change rate Se(i) = S(c) - S(c-1), nitrogen pressure coupling deviation N(p); Where -50≤S(c)≤50, -25≤Se(i)≤25, -20≤N(p)≤20.

[0027] This step adds an independent input for nitrogen pressure coupling deviation, which simultaneously captures the thrust steady-state deviation, dynamic change trend and nitrogen pressure decay disturbance, solving the shortcomings of traditional single-loop thrust control that cannot identify nitrogen pressure relief disturbance, and providing complete input data for three-dimensional fuzzy compensation inference.

[0028] S3. The input and output variables are normalized and discretely mapped using a linear mapping formula; the formula for the linear mapping is: ; Where n is a discrete hierarchical variable, and the set of values ​​for the discrete hierarchical variable is n∈{-3,-2,-1,0,1,2,3}; where X represents the original measured working condition variable, and a and b are the lower and upper bounds of the basic value domain of the corresponding variable.

[0029] This step abandons the traditional segmented threshold quantization and adopts a breakpoint-free linear transformation to unify the mapping rules for different pressure and thrust dimension variables, eliminate input distortion caused by numerical jumps, and improve the accuracy of fuzzy inference and thrust control.

[0030] S4. The intermediate interval uses a smooth Gaussian function as the main membership function to ensure smooth steady-state regulation; the boundary uses a bell-shaped membership function to smoothly transition the output, avoid sudden changes in boundary conditions, suppress valve mechanical vibration and low-frequency combustion oscillation, and establish a membership mapping of deviation, deviation change rate, and regulation amount; in addition, deviation, deviation change rate, and nitrogen pressure coupling deviation are all configured with independent parameter groups and are not shared with each other.

[0031] This step addresses the issue of abrupt output changes at the boundary of a single membership function, eliminating the shortcomings of traditional controllers, such as excessively rapid decay of membership degrees at the boundary of the domain and abrupt output changes. It also suppresses high-frequency reciprocating vibrations of metering valves and nitrogen booster valves, reduces pipeline flow pulsation, eliminates low-frequency combustion instability in the combustion chamber, and extends the service life of valves and injectors.

[0032] S5. Three-dimensional fuzzy inference is completed by superimposing nitrogen pressure compensation logic on the 7×7 basic thrust fuzzy rule base; a 7×7 two-dimensional basic thrust rule is constructed with thrust deviation and thrust deviation change rate, and three-dimensional coupled inference is realized by superimposing nitrogen pressure coupling deviation compensation logic to offset the thrust offset caused by nitrogen pressure decay in real time; this step introduces nitrogen pressure deviation into the inference process, and adjusts the output synchronously according to the nitrogen pressure level, actively compensates for the propellant flow offset caused by continuous cylinder depressurization, stabilizes the oxygen-fuel mixture ratio, and avoids faults such as fuel-rich carbon buildup and oxygen-rich ablation.

[0033] S6. The centroid method is used to solve the fuzzy calculation formula to calculate the adjustment amount u with nitrogen compensation, so as to avoid the actuator from over-range operation and reduce the thrust adjustment overshoot and pipeline instantaneous flow impact. After the adjustment amount u is calculated, it is limited to the discrete range of [-3,3] and then output to the valve actuator. This step outputs a high-precision continuous adjustment signal to prevent the extreme working conditions of the valve being fully open or fully closed, reduce the thrust adjustment overshoot and pipeline instantaneous flow impact, and ensure the stability of the propulsion supply system.

[0034] S7. On the one hand, the opening of the electromagnetic metering valves for fuel and liquid oxygen is adjusted synchronously to maintain the rated oxygen-fuel ratio throughout the process. On the other hand, the nitrogen booster valves for the fuel tank and liquid oxygen tank are adjusted synchronously to compensate for the pressure drop of the high-pressure nitrogen cylinder and prevent the combustion efficiency from decreasing. In this step, the two metering valves operate synchronously to eliminate the response time difference, maintain the rated oxygen-fuel ratio throughout the thrust range, and improve the combustion efficiency of the combustion chamber. The nitrogen booster valve is adjusted synchronously to offset the cylinder depressurization in real time, thus doubly stabilizing the propellant supply pressure difference.

[0035] S8. The propellant enters the combustion chamber for staged combustion, and sensors continuously collect data, which is then fed back to S1 to form a closed-loop control. This step collects multi-dimensional combustion, pressure, and thrust data and feeds it back to the nitrogen timing pre-control module in S1 to dynamically update the pressurization timing for the next cycle, forming a millisecond-level full-process closed-loop iterative control. This further reduces start-up shock and improves the system's adaptability to nonlinear disturbances such as nitrogen decay and pipeline pressure drop.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A control method for a propulsion system of a squeeze-type rocket engine, characterized in that, include: S1, Nitrogen gas timing pre-control; S2. Real-time acquisition of multiple parameters, calculation of three sets of fuzzy input variables; S3. Use the linear mapping formula to complete the normalized discrete mapping of input and output variables; S4. Using a smooth Gaussian function as the main membership function and a bell-shaped membership function for the boundary, establish a membership mapping for deviation, deviation rate of change, and adjustment amount. S5. Three-dimensional fuzzy reasoning is completed by superimposing nitrogen pressure compensation logic on a 7×7 basic thrust fuzzy rule base. S6. The adjustment amount u containing nitrogen compensation is calculated using the centroid method to solve the fuzzy calculation formula; S7. Synchronously adjust the opening of the fuel and liquid oxygen electromagnetic metering valves, and synchronously adjust the nitrogen booster valves of the fuel tank and liquid oxygen tank to compensate for the pressure drop of the high-pressure nitrogen cylinder. S8. The propellant enters the combustion chamber and undergoes staged combustion. The sensor continuously collects data and returns it to S1 to form a closed-loop control.

2. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that, The nitrogen timing pre-control includes: The system retrieves the remaining pressure of the high-pressure nitrogen cylinder, the real-time pressure of the fuel tank, and the real-time pressure of the liquid oxygen tank from the sensors of the previous closed-loop cycle. It then plans in advance the nitrogen pre-pressurization start-up delay and continuous conduction duration for the current control cycle, and stores the timing parameters for back-end closed-loop iterative correction, thereby reducing the boost shock and thrust peak overshoot during the engine start-up phase.

3. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that: The three sets of fuzzy input variables are calculated as follows: Thrust deviation S(c), thrust deviation change rate Se(i) = S(c) - S(c-1), nitrogen pressure coupling deviation N(p); Where -50≤S(c)≤50, -25≤Se(i)≤25, -20≤N(p)≤20.

4. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that: In S2, the formula for the linear mapping is: ； Where n is a discrete hierarchical variable, and the set of values ​​for the discrete hierarchical variable is n∈{-3,-2,-1,0,1,2,3}; where x represents the original measured working condition variable, a is the lower limit of the domain of the corresponding variable, and b is the upper limit of the domain of the corresponding variable.

5. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that, The smooth Gaussian function is expressed as follows: ; in, σ is the membership function center value, and σ is the Gaussian function width coefficient; The bell-shaped membership function is: Where c is the half-width parameter and b is the curvature adjustment coefficient.

6. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that, The 7×7 basic thrust fuzzy rule includes: The seven-level fuzzy linguistic variables NB, NM, NS, ZO, PS, PM, and PB are used to represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large, respectively. When the thrust deviation and the rate of change of thrust deviation are in the same direction and reach their extreme values, the output is the maximum reverse adjustment amount. When they are in opposite directions and reach their extreme values, the output is the maximum positive adjustment amount. The smaller the deviation and the smoother the change, the closer the output adjustment amount is to zero.

7. The control method for the propulsion system of the squeeze-type rocket engine according to claim 6, characterized in that, The nitrogen pressure compensation logic is as follows: If the nitrogen pressure coupling deviation N(p) is NB, the nitrogen boost compensation is positively superimposed under the same thrust deviation, and the nitrogen boost valves of the fuel tank and liquid oxygen tank are opened simultaneously; if the nitrogen pressure coupling deviation N(p) is PB, the nitrogen boost output is reduced in the reverse direction, and the two nitrogen boost valves are closed simultaneously; when N(p) is ZO, no compensation is superimposed, and only the basic thrust adjustment output is executed.

8. The control method for the propulsion system of the squeeze rocket engine according to claim 7, characterized in that, The specific process of the three-dimensional fuzzy reasoning is as follows: The first step is to substitute the thrust deviation S(c) and the thrust deviation change rate Se(i) into the 7×7 basic thrust rule base to calculate the basic adjustment fuzzy subset; The second step is to introduce a nitrogen pressure coupling deviation N(p), and the nitrogen pressure compensation logic performs amplitude correction on the basic adjustment fuzzy subset. The third step is to take the union of the corrected multi-channel fuzzy subsets to obtain the final comprehensive output fuzzy set.

9. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that, The centroid method for fuzzy resolution calculation formula is as follows: ;in, The composite membership function is the output adjustment amount after nitrogen pressure compensation.

10. The control method for the propulsion system of the squeeze rocket engine according to claim 1, characterized in that, The method for adjusting the opening of the fuel and liquid oxygen electromagnetic metering valves is as follows: The adjustment amount u synchronously and proportionally adjusts the flow opening of the fuel electromagnetic metering valve and the liquid oxygen electromagnetic metering valve, keeping the adjustment amplitudes of the two valves matched to maintain the real-time oxygen-fuel ratio of fuel and liquid oxygen within the preset allowable range. When the adjustment amount u is positive, the two valves are opened synchronously to increase the propellant flow rate, and when the adjustment amount u is negative, the two valves are closed synchronously to reduce the propellant flow rate. The synchronous action throughout the process eliminates the ratio imbalance caused by the response time difference of the two valves.

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