On-orbit calibration method for thrust eccentricity of single thruster of micro-nano satellite

Abstract

The invention discloses an on-orbit calibration method for thrust eccentricity of a single thruster of a micro-nano satellite, and aims to solve the problem that the actual size and direction of thrust eccentricity cannot be obtained through existing ground calibration. The method is realized through the following steps: calculating the average thrust of a thruster by using data of an on-satellite pressure sensor and a ground fitting formula; acquiring momentum wheel rotating speed and satellite angular speed data before and after orbit control, and respectively calculating average angular accelerations in Y and Z directions; calculating a thrust eccentric torque by using an angular momentum theorem in combination with satellite rotational inertia and momentum wheel rotational inertia; and finally, the components of thrust eccentricity in the Y and Z directions of the satellite body are obtained through the ratio of the thrust to the torque. According to the method, the accurate size and direction of thrust eccentricity can be calculated in real time based on in-orbit telemetry data, orbit deviation caused by attitude disturbance torque is avoided, and the method is suitable for scenes such as micro-nano satellite formation and constellation networking and has the remarkable advantages of being low in engineering cost, easy and convenient to operate and high in adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano satellite orbit control, and in particular to an on-orbit calibration method for the thrust eccentricity of a single thruster of a micro-nano satellite. Background Art

[0002] In recent years, with the rapid development of micro- and nanosatellite formation and constellation networking technologies, the demand for micro- and nanosatellite orbit control has significantly increased. Currently, commercial micro- and nanosatellite orbit control actuators primarily utilize single-thruster chemical propulsion, driven by cost, size, power consumption, and maneuverability requirements. Single thrusters are typically installed near the satellite's center of mass. However, due to limitations in satellite center of mass measurement methods and installation errors, as well as the effect of the thrust generated by thruster ignition deviating from the thruster axis, this can cause the thrust line of action to deviate from the satellite's center of mass, resulting in thrust eccentricity.

[0003] Due to thrust eccentricity, a single satellite thruster generates additional attitude disturbance torques in roll, pitch, and yaw during operation, thereby affecting the vehicle's attitude control. If the attitude disturbance torques caused by thrust eccentricity and center of mass drift are too large and exceed the vehicle's own attitude control torque, the vehicle's attitude will become unstable. During satellite operation, regular orbit maintenance and adjustments are required to address orbital perturbations (such as atmospheric drag and uneven Earth gravity). Thrust eccentricity can increase the complexity of orbit adjustments and even cause orbit deviations beyond the allowable range. Therefore, studying thrust eccentricity can help develop more precise orbit control strategies and ensure the successful completion of satellite orbit control missions.

[0004] Currently, thrust eccentricity is primarily estimated through ground-based measurements. This involves obtaining the satellite's center of mass using a centroid measuring instrument. Installation ensures the thruster axis passes through the satellite's center of mass. Ground-based thruster test fires confirm the relationship between the thrust axis and the thruster axis, thereby controlling thrust eccentricity within a certain deviation range. However, this method cannot determine the actual magnitude and direction of thrust eccentricity, making it ineffective in guiding actual orbit control. Summary of the Invention

[0005] The present invention provides an on-orbit calibration method for the thrust eccentricity of a single thruster of a micro-nano satellite, which aims to overcome the shortcomings of the existing ground-based thrust eccentricity calibration and provide an on-orbit calibration method for obtaining the actual size and deviation direction of the thrust eccentricity.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A method for on-orbit calibration of thrust eccentricity of a single thruster of a micro-nano satellite comprises the following steps:

[0008] Step 1: Obtain the pressure value of the onboard propulsion system pressure sensor , using the ground fitting formula Calculate the average thrust of the thrusters during orbit control ,in is the fitting coefficient of the relationship between thrust and pressure;

[0009] Step 2: Obtain the satellite momentum wheel speed data at the start and end of orbit control, and calculate the momentum wheel speed on the satellite body during orbit control. 、 The average angular acceleration in the direction;

[0010] Step 3: Obtain the satellite angular velocity data at the start and end of orbit control, and calculate the satellite's angular velocity during orbit control. 、 The average angular acceleration in the direction;

[0011] Step 4: According to the satellite Rotational inertia 、 Rotational inertia , Momentum wheel moment of inertia , and the angular acceleration obtained in steps 2 and 3, use the angular momentum theorem to calculate the thruster 、 Eccentric moment in the direction 、 ;

[0012] Step 5: Thrust obtained from step 1 And the eccentric moment obtained in step 4 is used to calculate the thrust eccentricity on the satellite body. Directional component and Directional component .

[0013] Furthermore, in step 2, the momentum wheel at the start of orbit control is obtained Speed 、 Speed , the momentum wheel at the end Speed 、 Speed , orbit control time , then the momentum wheel Average angular acceleration , momentum wheel Average angular acceleration .

[0014] Furthermore, in step 3, the satellite orbit control start time is obtained. Angular velocity 、 Angular velocity , end time satellite Angular velocity 、 Angular velocity , orbit control time , then the satellite Towards the mean angular acceleration , Towards the mean angular acceleration .

[0015] Furthermore, in step 4, the eccentric torque is calculated according to the installation method of the momentum wheel:

[0016] If the momentum wheel is installed upright, then ;

[0017] If the momentum wheel is reversed, .

[0018] Furthermore, the thruster nozzle is directed toward the satellite body. Direction, thrust direction is direction.

[0019] Furthermore, the ground fitting formula in step 1 is obtained by fitting thruster ground ignition test data.

[0020] Furthermore, the value calculated in step 5 is and Used to determine the magnitude and direction of thrust eccentricity.

[0021] The beneficial effects achieved by the present invention are:

[0022] The present invention utilizes the positive and negative correlation between the change in momentum wheel speed and the change in satellite angular velocity to determine the specific deviation direction of thrust eccentricity in the body coordinate system (such as the positive direction of the Y axis or the negative direction of the Z axis), which makes up for the defect that ground estimation cannot determine the direction and improves the targetedness of the attitude control strategy.

[0023] By calibrating the actual eccentricity parameters on-orbit, the interference torque error caused by thrust eccentricity in the orbit control model can be corrected to avoid mission failure caused by attitude instability or excessive orbit deviation. It is especially suitable for scenarios with high requirements for orbit control accuracy, such as micro-nano satellite formations and constellation networking.

[0024] There is no need to rely on high-precision ground centroid measurement equipment and complex installation and calibration processes. Calibration can be completed using conventional telemetry data from the satellite during its in-orbit operation, which greatly reduces the cost and time cost of project implementation and improves the flexibility of on-orbit maintenance of micro-nano satellites.

[0025] The method is based on the data of common satellite propulsion system pressure sensors, momentum wheels and gyroscopes, does not rely on special hardware modification, and is applicable to various micro-nano satellites using single-thruster chemical propulsion. The calibration process can be automatically executed by on-board software, which has engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the coordinate system and thrust direction of the micro-nano satellite body in the present invention.

[0028] Figure 2 The present invention provides an on-orbit calibration process for the thrust eccentricity of a single thruster of a micro-nano satellite.

[0029] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] This paper proposes an on-orbit calibration method for the thrust eccentricity of a single thruster on a micro-nano satellite. This method calculates the actual thrust magnitude by calculating the orbital change during thruster ignition. The satellite's angular momentum change is calculated by acquiring information about the gyro angular velocity and flywheel speed during the ignition process. Then, using attitude dynamics, the magnitude and direction of the thrust eccentricity are calculated, combining the thrust and attitude changes. This method achieves on-orbit thrust eccentricity calibration.

[0034] Assuming that the thrust is along the X direction of the satellite body, the thrust eccentricity calculation formula in the Y and Z directions of the satellite body is as follows:

[0035] (1)

[0036] Where, and They represent the thrust eccentricity components in the Y and Z directions of the satellite body, and They represent the thrust eccentric torque components in the Y and Z directions of the satellite body, represents the thrust of the thruster, and Respectively represent the satellite's Y and Z moments of inertia, represents the satellite's moment of inertia using momentum wheels, Indicates the duration of orbit control. and They represent the satellite’s Y and Z angular velocities at the start of orbit control, and They represent the satellite’s Y and Z angular velocities at the end of orbit control, and They represent the rotation speeds of satellite momentum wheels Y and Z at the start of orbit control, and They represent the rotation speeds of the satellite momentum wheels Y and Z at the end of orbit control, Indicates the pressure value of the onboard propulsion system pressure sensor, 、 、 The fitting coefficient representing the relationship between thrust and pressure.

[0037] The specific method for on-orbit calibration of thrust eccentricity of a single thruster of a micro-nano satellite is as follows:

[0038] a) Assume that the pressure value of the onboard propulsion system pressure sensor is , using the ground fitting formula (the fitting coefficient of the relationship between thrust and pressure is 、 、 (expressed) Calculate the average thrust of the thruster during orbit control Then there is

[0039] (2)

[0040] b) Assume that the thruster nozzle is facing the -X direction of the satellite body, that is, the thrust is in the +X direction. Obtain the satellite telemetry data at the start of orbit control: the Y speed of the momentum wheel is (Speed ​​unit: rpm / s, same below), the speed of momentum wheel Z is . Get the satellite telemetry data at the end of orbit control: the Y speed of the momentum wheel is , the momentum wheel Z speed is The orbit control duration is The average angular acceleration of the momentum wheel Y during satellite orbit control is , the average angular acceleration of the momentum wheel Z is Then there is

[0041] (3)

[0042] c) Assume that the satellite obtains the satellite telemetry data at the start of orbit control: the satellite angular velocity in the Y direction is (Angular velocity unit: ° / s, the same below), the satellite's Z-axis angular velocity is . Get the satellite telemetry data at the end of orbit control: the satellite Y-axis angular velocity is , the satellite's Z-axis angular velocity is The average angular acceleration in the Y direction during satellite orbit control is , the average angular acceleration in the Z direction is Then there is

[0043] (4)

[0044] d) Assume that the satellite's Y-axis moment of inertia is , the Z-direction moment of inertia is The satellite uses momentum wheels with a rotational inertia of Due to the different installation methods of the momentum wheel (positive or negative), the acceleration direction generated by the momentum wheel absorbing the external torque will be different, so it is necessary to discuss each case separately. According to the angular momentum theorem, the eccentric torque of the thruster can be calculated and . Then we have:

[0045] (5)

[0046] e) According to thrust and thrust eccentric moment and , the thrust eccentricity component in the Y direction of the satellite body can be calculated as and the component in the Z direction is , the formula is as follows

[0047] (6)

[0048] Figure 1 The coordinate system and thrust direction of the micro-nano satellite are given. Figure 2 The on-orbit calibration process of the thrust eccentricity of a micro-nano satellite single thruster is given. The goal of the present invention is to accurately calibrate the magnitude and direction of the thrust eccentricity of a micro-nano satellite single thruster.

[0049] The specific implementation steps of the on-orbit calibration of the thrust eccentricity of a single thruster of a micro-nano satellite are as follows:

[0050] Step 1: Calculate the average thrust of the thruster according to the pressure value;

[0051] Assume that the pressure value of the onboard propulsion system pressure sensor is , using the ground fitting formula (the fitting coefficient of the relationship between thrust and pressure is 、 、 (expressed) Calculate the average thrust of the thruster during orbit control Then there is

[0052] (7)

[0053] Step 2: Calculate the change in momentum wheel speed during orbit control;

[0054] Assume that the thruster nozzle is facing the -X direction of the satellite body, that is, the thrust is in the +X direction. Obtain satellite telemetry data at the start of orbit control: the Y speed of the momentum wheel is (The unit of speed is rpm, the same below), the speed of momentum wheel Z is. Get the satellite telemetry data at the end of orbit control: the speed of momentum wheel Y is , the momentum wheel Z speed is The orbit control duration is The average angular acceleration of the momentum wheel Y during satellite orbit control is , the average angular acceleration of the momentum wheel Z is Then there is

[0055] (8)

[0056] Step 3: Calculate the change in satellite angular velocity during orbit control;

[0057] Assume that the satellite obtains the satellite telemetry data at the start of orbit control: the satellite Y-axis angular velocity is (Angular velocity unit: ° / s, the same below), the satellite's Z-axis angular velocity is . Get the satellite telemetry data at the end of orbit control: the satellite Y-axis angular velocity is , the satellite's Z-axis angular velocity is The average angular acceleration in the Y direction during satellite orbit control is , the average angular acceleration in the Z direction is Then there is

[0058] (9)

[0059] Step 4: Calculate the thrust eccentric torque by combining the satellite angular velocity change and the momentum wheel speed change

[0060] Assume that the satellite's Y-axis moment of inertia is , the Z-direction moment of inertia is The satellite uses momentum wheels with a rotational inertia of Due to the different installation methods of the momentum wheel (positive or negative), the acceleration direction generated by the momentum wheel absorbing the external torque will be different, so it is necessary to discuss each case separately. According to the angular momentum theorem, the eccentric torque of the thruster can be calculated and Then there is

[0061] (10)

[0062] Step 5: Calculate thrust eccentricity

[0063] According to thrust and thrust eccentric moment and , the thrust eccentricity component in the Y direction of the satellite body can be calculated as and the component in the Z direction is , the formula is as follows

[0064] (11)

[0065] The above method is verified by simulation as follows:

[0066] The satellite's Y-axis and Z-axis moments of inertia are set to 3.58 kg.m 2and 12.53 kg.m 2 The satellite uses three-axis orthogonal momentum wheels with a rotational inertia of 0.00047764 kg.m 2 . At the start of the satellite orbit control, the satellite angular velocities in the Y and Z directions are 0.0007° / s and -0.0001° / s respectively, and at the end of the orbit control, the satellite angular velocities in the Y and Z directions are 0.0357° / s and 0.0249° / s respectively. The satellite momentum wheel X is installed upright along the X-axis of the satellite body, and the satellite momentum wheel Z is installed in reverse along the Z-axis of the satellite body. At the start of the orbit control, the rotational speeds of the satellite momentum wheels Y and Z are 1115.25rpm and 661.75rpm respectively, and at the end of the orbit control, the rotational speeds of the satellite momentum wheels Y and Z are 1708.25rpm and 439.25rpm respectively. The orbit control duration is 30s. The tank pressure value during the satellite orbit control is 1.713MPa, and the fitting coefficients of the thrust and pressure of the satellite thrusters are , , .

[0067] According to formula (1), the thrust eccentricity in the Y direction of the satellite body is -0.8252 mm, and the thrust eccentricity in the Z direction of the satellite body is 1.6006 mm, which is basically consistent with the setting.

[0068] The above analysis shows that the proposed method can effectively calibrate the thrust eccentricity of a single thruster of a micro-nano satellite.

[0069] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present description and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for on-orbit calibration of thrust eccentricity of a single thruster of a micro-nano satellite, characterized in that: The following steps are involved: Step 1: Obtain the pressure value of the onboard propulsion system pressure sensor , using the ground fitting formula Calculate the average thrust of the thrusters during orbit control ,in is the fitting coefficient of the relationship between thrust and pressure; Step 2: Obtain the satellite momentum wheel speed data at the start and end of orbit control, and calculate the momentum wheel speed on the satellite body during orbit control. 、 The average angular acceleration in the direction; Step 3: Obtain the satellite angular velocity data at the start and end of orbit control, and calculate the satellite's angular velocity during orbit control. 、 The average angular acceleration in the direction; Step 4: Satellite Rotational inertia 、 Rotational inertia , Momentum wheel moment of inertia , and the angular acceleration obtained in steps 2 and 3, use the angular momentum theorem to calculate the thruster 、 Eccentric moment in the direction 、 ; Step 5: Calculate the thrust obtained in step 1 And the eccentric moment obtained in step 4 is used to calculate the thrust eccentricity on the satellite body. Directional component and Directional component .

2. The method according to claim 1, characterized in that In step 2, the momentum wheel at the start of orbit control is obtained. Speed 、 Speed , the momentum wheel at the end Speed 、 Speed , orbit control time , then the momentum wheel Average angular acceleration , momentum wheel Average angular acceleration .

3. The method according to claim 1, characterized in that In step 3, the satellite orbit control start time is obtained Angular velocity 、 Angular velocity , end time satellite Angular velocity 、 Angular velocity , orbit control time , then the satellite Towards the mean angular acceleration , Towards the mean angular acceleration .

4. The method according to claim 1, wherein In step 4, the eccentric torque is calculated according to the installation method of the momentum wheel: If the momentum wheel is installed upright, then ; If the momentum wheel is reversed, .

5. The method according to claim 1, wherein The thruster nozzle faces the satellite body Direction, thrust direction is direction.

6. The method according to claim 1, characterized in that The ground fitting formula in step 1 is obtained by fitting the thruster ground ignition test data.

7. The method according to any one of claims 1 to 6, characterized in that Calculated in step 5 and Used to determine the magnitude and direction of thrust eccentricity.

Images