CN108760365A - Detector stress analogy method in a kind of soft landing experiment - Google Patents

Abstract

The invention provides a method for simulating the stressed state of the detector in the soft landing test, through the thrust _Tx of the detector engine and the downward and upward simulated accelerations a' _, a ’ _, confirm that the simulation requirements of the force state of the detector are met at the same time, that is, the four inequalities of the tension of the suspension rope and the test quality of the detector, and then use the assistance of the tension of the suspension rope and rely on the engine thrust to adjust the control so that the force state of the detector is consistent with the real software. The landing process is consistent, thereby accurately simulating the soft landing process in which the size and direction of the resultant force on the probe in the vertical direction will constantly change, so that the present invention can be applied to the ground soft landing on the surface of other planets such as lunar probes and Mars probes Verification test.

Description

A method for simulating the force state of the detector in the soft landing test

technical field

The invention belongs to the field of deep space exploration, in particular to a method for simulating the stressed state of a detector in a soft landing test.

Background technique

With the expansion of the field of deep space exploration, it is an inevitable process for the development of detection technology to carry out landing detection on the surface of the moon, Mars, asteroids and other celestial bodies. Deep space probes need to have the ability of autonomous guidance, navigation and control. The core design element of the landing mission. Due to the importance of the soft landing mission, complex control, irreversible process, and high reliability requirements, ground verification tests need to be carried out during the development of the detector. The gravity and atmospheric environment under ground conditions are different from those on the surface of other celestial bodies. It is impossible to fly only relying on the thrust of the probe's own engine, and it is impossible to verify the guidance, navigation and control of the probe. The same landing state can simulate the motion parameters of the probe such as flight speed and height, so as to reproduce the soft landing process of the probe on the surface of extraterrestrial celestial bodies. The simulation of the force state is the core of the design of the ground test.

Using a sling to provide a constant pulling force for the detector, and balancing its partial gravity is a common way to realize the force simulation of the detector. However, this method is mainly used for static force simulation where the acceleration in the vertical direction is zero. In the soft landing test, in order to verify the control capability, the ignition of the detector engine is required, and the thrust needs to be adjusted in real time according to the real control law to ensure that the detector The flight parameters are consistent with the real flight status. During the process, the detector performs complex variable-acceleration motions, and the size and direction of the resultant force in the vertical direction are constantly changing; as the propellant is consumed, the gravity on the detector is also changing; in addition, the detector is also subjected to wind resistance during the movement process. , wind load, tension control deviation and other uncertain disturbances. Therefore, the conventional constant tension balance method cannot be directly applied to the soft landing verification test of the probe.

Contents of the invention

In order to solve the above problems, the present invention provides a method for simulating the force state of the detector in the soft landing test, which can accurately simulate the soft landing process in which the magnitude and direction of the resultant force on the detector in the vertical direction will constantly change.

A method for simulating the stressed state of a detector in a soft landing test, comprising the following steps:

Step 1: Use the sling to provide pulling force for the detector, and obtain the engine thrust Tx of the detector and the simulated downward acceleration _a'down and _upward simulated acceleration a'up _of the detector under different force states in the soft landing test of the detector ;

Wherein, the engine thrust Tx of the detector satisfies the following inequality when the detector _is in a force-balanced state:

T _x = mg-Ff ≥ T _min (1)

T _x = mg-Ff ≤ T _max (2)

Among them, F is the pulling force of the sling, f is the interference force received by the detector in the soft landing test, T _min is the minimum output thrust of the detector engine in the soft landing test, and T _max is the maximum output thrust of the detector engine in the soft landing test , m is the test mass of the detector, g is the earth's gravitational acceleration;

The downward simulated acceleration a' _{and the} upward simulated acceleration a' _of the detector respectively satisfy the following inequalities when the detector is in a non-force balanced state:

_a'down =(mg-FT _min -f)/ _m≥adown (3)

_a'up =(F+T _max +f-mg)/ _m≥aup (4)

Wherein, a _up and a _down are respectively the maximum upward acceleration and the downward maximum acceleration of the probe during the actual soft landing process;

Step 2: Jointly solve the inequalities (1)-(4) to obtain the corresponding relationship between the test mass m of the detector and the tension F of the suspension rope, so as to determine the test mass m of the detector satisfying the inequalities (1)-(4) and The tension F interval of the suspension rope corresponding to the test mass m of the detector is used to realize the simulation of the force state of the detector in the soft landing test.

Further, the method for obtaining the minimum output thrust _Tmin and the maximum output thrust _Tmax of the engine is specifically as follows:

The probe engine is subjected to a hot test run in the ground environment, and the minimum output thrust T _min and the maximum output thrust T _max of the probe engine in the atmospheric environment are obtained.

Further, the detector test mass m is composed of two parts _: the dry mass m of the detector and the propellant filling mass Δm, and after obtaining the corresponding relationship between the test mass m of the detector and the pulling force F of the suspension rope, the detector The corresponding relationship between the test mass m and the rope tension F is transformed into the corresponding relationship between the propellant filling mass Δm and the hanging rope tension F, and then the propellant filling mass Δm and the relationship between the propellant filling mass and The propellant filling mass Δm corresponds to the tension F interval of the sling, and then realizes the force state simulation of the detector in the soft landing test.

Beneficial effect:

The invention provides a method for simulating the stressed state of the detector in the soft landing test, through the engine thrust _Tx of the detector under different stressed states in the test and the downward and upward simulated acceleration a' _of the detector in the soft landing test. On a' _, it is determined that the simulation requirements of the force state of the detector are met at the same time, that is, the sling force of the four inequalities and the test quality of the detector, and then use the sling force to assist and rely on the engine thrust to adjust the control to make the force state of the detector consistent with the real The soft landing process is consistent, thereby accurately simulating the soft landing process in which the size and direction of the resultant force on the probe in the vertical direction will constantly change, so that the present invention can be applied to the soft landing process on the surface of other planets such as lunar probes and Mars probes. Landing verification test.

Description of drawings

Fig. 1 is a schematic diagram of force analysis of the detector provided by the present invention in a state of force balance;

Fig. 2 is a schematic diagram of the corresponding relationship between the probe propellant filling quality and the pulling force of the suspension rope provided by the present invention;

Fig. 3 is a schematic diagram of the comparison between the actual flight curve and the simulation results of the probe in the soft landing test along the height direction provided by the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

Embodiment one

In this embodiment, by analyzing parameters such as the quality of the detector, the acceleration range of the soft landing flight process, the actual thrust output range of the engine ground environment, and the interference force in the detector ground test, the requirements for the pulling force of the sling are determined, and the detector is assisted by the pulling force of the sling. The stress state is consistent with the real soft landing process, which can satisfy the motion simulation of the probe in the ground soft landing test. A method for simulating the stressed state of a detector in a soft landing test, comprising the following steps:

Step 1: Use the sling to provide pulling force for the detector, and obtain the engine thrust Tx of the detector and the simulated downward acceleration _a'down and _upward simulated acceleration a'up _of the detector under different force states in the soft landing test of the detector .

It should be noted that the different force states in the soft landing test of the probe include the force-balanced state of the probe, the non-force-balanced state with the acceleration direction downward, and the non-force-balanced state with the acceleration direction upward. Wherein, when the force is balanced, the detector maintains a state of hovering or uniform linear motion. Referring to FIG. 1 , this figure is a schematic diagram of force analysis of the detector provided in this embodiment in a state of force balance. Wherein, the thrust _Tx of the detector engine satisfies the following inequality:

T _x = mg-Ff ≥ T _min (1)

T _x = mg-Ff ≤ T _max (2)

Among them, F is the pulling force of the sling, f is the interference force received by the detector in the soft landing test, T _min is the minimum output thrust of the detector engine in the soft landing test, and T _max is the maximum output thrust of the detector engine in the soft landing test , m is the test mass of the detector, and g is the gravitational acceleration of the earth.

It should be noted that the disturbance force on the probe in the soft landing test includes the wind resistance, wind load, and tension control deviation of the probe during its movement.

It should be noted that due to the atmospheric back pressure in the ground environment, the output thrust of the probe engine will be attenuated to a certain extent, resulting in the actual output thrust range in the test being smaller than the actual flight process. That is to say, the real output thrust of the probe engine in the ground soft landing test is between T _min and T _max .

Optionally, the methods for obtaining the minimum output thrust T _min and the maximum output thrust T _max are specifically:

The probe engine is subjected to a hot test run in the ground environment, and the minimum output thrust T _min and the maximum output thrust T _max of the probe engine in the atmospheric environment are obtained.

The downward simulated acceleration a' _{and the} upward simulated acceleration a' _of the detector respectively satisfy the following inequalities when the detector is in a non-force balanced state:

_a'down =(mg-FT _min -f)/ _m≥adown (3)

_a'up =(F+T _max +f-mg)/ _m≥aup (4)

Among them, aup _and aup _are respectively the maximum upward acceleration and the maximum downward acceleration of the probe during the actual soft landing process; that is to say, in the real flight and ground soft landing test during the actual soft landing The received resultant acceleration is all within the range limited by _the two values _on a and a.

Step 2: Jointly solve the inequalities (1)-(4) to obtain the corresponding relationship between the test mass m of the detector and the tension F of the suspension rope, so as to determine the test mass m of the detector satisfying the inequalities (1)-(4) and The tension F interval of the suspension rope corresponding to the test mass m of the detector is used to realize the simulation of the force state of the detector in the soft landing test.

It should be noted that since the dry mass m ₀ of the detector has been determined in the design stage, the test mass m of the detector is mainly changed by changing the propellant filling mass Δm in the test stage. The tension of the suspension rope and the test mass of the detector required for the stress state simulation can convert the corresponding relationship between the test mass m of the detector and the tension F of the suspension rope to the corresponding relationship between the propellant filling mass Δm and the tension F of the suspension rope.

Specifically, the detector test mass m is composed of two parts: the detector dry mass m ₀ and the propellant filling mass Δm. After obtaining the corresponding relationship between the detector test mass m and the tension F of the suspension rope, the detector The corresponding relationship between the test mass m and the rope tension F is transformed into the corresponding relationship between the propellant filling mass Δm and the hanging rope tension F, and then the propellant filling mass Δm and the relationship between the propellant filling mass and The range of rope tension F corresponding to the propellant filling mass Δm, thereby realizing the simulation of the force state of the detector in the soft landing test.

Embodiment two

Based on the above embodiments, the method for simulating the force state of the detector in the soft landing test of the present invention will be introduced in detail below by taking the soft landing verification test of Chang'e-3 on the lunar surface as an example.

Based on the soft landing dynamics design on the lunar surface, the upward and downward motion accelerations of the probe during the soft landing are a _up =1.1m/s ² and a _down =0.47m/s ² respectively.

According to the thermal test of the engine in the ground environment, the thrust output range of the engine on the ground is determined to be T _min =630N, T _max =2710N.

According to the cross-sectional area of the detector and the moving speed, it is estimated that the wind resistance and other disturbances f received in the test are at most 25N, and the dry mass m ₀ of the detector is designed to be 1180kg.

Solve the inequalities (1)-(4) according to the constraint formula, and the results are shown in Figure 2. The shaded area of the oblique line in Figure 2 is the solution area that satisfies the inequalities (1)-(4) at the same time, using the propellant filling mass Δm corresponding to the solution area, and the sling tension F interval corresponding to the propellant filling mass Δm , in order to simulate the force state of the probe on the lunar surface on the ground.

Specifically, it can be seen from Figure 2 that the detector’s maximum propellant filling mass Δm is 163.5kg, and the corresponding sling tension value is 11671.3N, which can meet the test requirements, but the selection of this value does not allow control deviations in the sling tension. That is to say, the pulling force of the hanging rope must be 11671.3N in order to successfully simulate the force state of the detector on the lunar surface on the ground; however, due to various resistance factors, it is not convenient to keep the pulling force of the hanging rope at 11671.3N at all times, so it is found according to Figure 2 , when the propellant is less than the filling mass of 163.5kg, the corresponding pulling force of the sling is within a range, and a certain fluctuation in the pulling force is also allowed at this time; comprehensively considering various effects, the propellant filling mass can be determined as 100kg in the test. The tension value of the rope is taken as 11000N, and the tension control accuracy is allowed to have a fluctuation range of ±200N. Other random interference effects can be considered comprehensively, that is, even if the detector is subjected to a comprehensive interference effect of ±200N in the test, it will not affect its final response. Simulation of the force state.

Refer to FIG. 3 , which is a schematic diagram of the comparison between the actual flight curve and the simulation results of the probe in the soft landing test along the height direction provided by this embodiment. It can be seen from Fig. 3 that after adopting the propellant filling quality and rope tension range determined by the method of this embodiment, the detector in the test can overcome the system interference, and the flight curve is completely consistent with the simulation result, which serves the purpose of test verification.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can certainly make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (3)

1. detector stress analogy method in a kind of soft landing experiment, which is characterized in that include the following steps：

Step 1：It uses lifting rope to provide pulling force for detector, and obtains in detector soft landing experiment and detected under different stresses Device motor power T_xThe analog acceleration a' downward with detector_Under, upward analog acceleration a '_On；

Wherein, the detector motor power T_x, such as lower inequality is met in the case where detector is in force balance state：

T_x=mg-F-f >=T_min (1)

T_x=mg-F-f≤T_max (2)

Wherein, F is lifting rope pulling force, and f is the perturbed force that detector is subject in soft landing experiment, T_minIt is detected in being tested for soft landing The minimum thrust output of device engine, T_maxThe maximum output thrust of detector engine in being tested for soft landing, m is detector It participates in the experiment quality, g is terrestrial gravitation acceleration；

The downward analog acceleration a' of the detector_Under, upward analog acceleration a'_On, non-stress balance is in detector Meet such as lower inequality under state respectively：

a'_Under=(mg-F-T_min-f)/m≥a_Under (3)

a'_On=(F+T_max+f-mg)/m≥a_On (4)

Wherein, a_On、a_UnderRespectively detector peak acceleration upward during practical soft landing, downward maximum acceleration Degree；

Step 2：Joint solves inequality (1)~(4), obtains detector and participates in the experiment the correspondence of quality m and lifting rope pulling force F, from And it determines while meeting the detectors of inequality (1)~(4) and participate in the experiment and quality m and participate in the experiment the corresponding lifting ropes of quality m with detector The sections pulling force F, and then realize the stress simulation of detector in soft landing experiment.

2. detector stress analogy method in a kind of soft landing experiment as described in claim 1, which is characterized in that described Engine minimum thrust output T_minWith maximum output thrust T_maxAcquisition methods be specially：

The detector engine is subjected to heat run test in ground environment, obtains detector engine in atmospheric environment Minimum thrust output T_minWith maximum output thrust T_max。

3. detector stress analogy method in a kind of soft landing experiment as described in claim 1, which is characterized in that described Detector participates in the experiment quality m by detector dry mass m₀It is formed with repropellenting quality Δ m two parts, then obtains detector and participate in the experiment After the correspondence of quality m and lifting rope pulling force F, the participate in the experiment correspondence of quality m and lifting rope pulling force F of detector is converted into propulsion Agent fills the correspondence of quality Δ m and lifting rope pulling force F, then determines while meeting the repropellenting matter of inequality (1)~(4) Δ m and the sections lifting rope pulling force F corresponding with repropellenting quality Δ m are measured, and then realizes detector in soft landing experiment Stress is simulated.