LQG relative orbit control method under condition that orbit control thrust deviates from mass center

Abstract

The invention discloses an LQG relative orbit control method under the condition that orbit control thrust deviates from a mass center, and the method comprises the steps: giving out the orbit control thrust pulse width amplitude limiting amount of each axis based on the relative orbit control demand under the condition that the orbit control thrust deviates from the mass center and considering the conditions of orbit control disturbance torque and attitude control torque during relative orbit control; and performing amplitude limiting on the orbit control original quantity calculated based on the relative state deviation quantity through the LQG control law, and then outputting the orbit control original quantity to each orbit control thruster for execution. The LQG relative orbit control method under the condition that the orbit control thrust deviates from the mass center is easy to implement and easy to apply in engineering.

Description

Technical Field

[0001] The present invention relates to the field of aircraft control, and in particular to an LQG relative orbit control method under the condition that the orbit control thrust deviates from the center of mass. Background Art

[0002] Existing spacecraft do not yet have the relevant technology for relative orbit control when the orbit control thrust deviates from the center of mass. The propulsion system of conventional on-orbit satellites or aircraft is basically designed as a combined state of orbit control thrusters in which the orbit control force of each axis basically passes through the center of mass of the aircraft.

[0003] Since the aircraft cannot ensure that the orbit control thrust vectors of each axis pass near the center of mass, and since the orbit control resultant force deviates greatly from the center of mass position, it will generate a non-negligible interference torque, which will interfere with the attitude control of the aircraft. Therefore, when the aircraft performs relative orbit control, it is necessary to effectively control this interference and not have a safety impact on the overall attitude and orbit control of the aircraft, so as to ensure that the interference caused by orbit control is small and the attitude and orbit control accuracy during relative orbit control is ensured. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and provide an LQG relative orbit control method when the orbit control thrust deviates from the center of mass. For the relative orbit control requirements when the orbit control thrust deviates from the center of mass, the orbit control interference torque and attitude control torque during the relative orbit control period are taken into consideration to achieve stable control of the aircraft during the relative orbit control period.

[0005] The technical solution of the present invention is: a LQG relative orbit control method under the condition that the orbit control thrust deviates from the center of mass, comprising:

[0006] Step 1: Obtain the pulse width limit of each axis orbit control according to the attitude control torque of each axis and the interference torque generated by the relative orbit control thrust of each axis;

[0007] Step 2: Calculate the relative state deviation. Based on the relative state deviation and the LQG control law matrix, calculate the original orbital acceleration of each axis to be applied in the current control cycle. Then, based on the original orbital acceleration of each axis, combined with the current spacecraft mass and the scalar force of each axis of the orbital control thrust combination, obtain the original orbital pulse width of each axis.

[0008] Step 3: Based on the orbit control pulse width limit of each axis and the inherent minimum control pulse width of the propulsion system, the original orbit control pulse width of each axis is limited to obtain the actual execution amount of the orbit control pulse width of each axis, and the execution amount is distributed to each corresponding orbit control thruster.

[0009] Furthermore, in step 1, the pulse width limit of each axis track is specifically:

[0010]

[0011] in, represents the pulse width limit of each axis orbit control, i,j∈{X,Y,Z} is the attitude and orbit control thruster combination with the same axis torque, is the attitude control torque of each axis The maximum absolute value in the vector, The interference torque generated by the relative orbit control thrust of each axis The maximum absolute value in the vector, t cyc is the control period, λ is the margin coefficient, take λ>1, To round x down, min{x,y} compares the two values ​​of x and y and takes the minimum value.

[0012] Furthermore, in step 2, the original value of the pulse width of each axis track control is specifically:

[0013]

[0014] in, is the original value of the pulse width of each axis track control, is the original value of the orbital acceleration of each axis, m is the current mass of the aircraft, f oc_i is the total force scalar of each axis of the orbit control thrust combination, t cyc is the control period, and round(·) is the rounding operation.

[0015] Furthermore, in step 3, the actual execution amount of each axis relative to the track control pulse width is specifically:

[0016]

[0017] in, is the actual execution amount of the relative track control pulse width of each axis, is the original value of the pulse width of each axis track control, The minimum control pulse width for the propulsion system is is the pulse width limit of each axis track control; sgn(x) is the sign function.

[0018] Furthermore, the attitude control torque of each axis is determined by the thrust vector of each attitude control thruster in the combination according to the combination of each axis attitude control thruster. and installation position vector The calculation is as follows:

[0019]

[0020] in, Represents the attitude control torque of each axis, i∈{X,Y,Z}, X represents the roll axis, Y represents the pitch axis, Z represents the yaw axis, n ac_i is the number of thrusters in the attitude control assembly, and × represents the vector product.

[0021] Furthermore, the interference torque generated by the relative orbit control thrust of each axis is determined by the thrust vector of each orbit control thruster in the combination according to the combination of each axis orbit control thruster. and installation position vector The calculation is as follows:

[0022]

[0023] in, It represents the interference torque generated by each axis relative to the orbit control thrust, i∈{X,Y,Z}, X represents the roll axis, Y represents the pitch axis, Z represents the yaw axis, n oc_i is the number of thrusters in the orbit control assembly, and × represents the vector product.

[0024] Furthermore, the relative state deviation is obtained by tracking the actual relative position and speed of the aircraft and the target aircraft during this control cycle. Relative position and speed to the expected The calculation is as follows:

[0025]

[0026] in, is the actual relative position vector, is the actual relative velocity vector; is the desired relative position vector, is the desired relative velocity vector.

[0027] Furthermore, the original acceleration of each axis track control is calculated as follows:

[0028]

[0029] Among them, K is the 3*6 LQG control law matrix, is the relative state deviation.

[0030] The present invention also provides an on-board computing terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method described above are implemented.

[0031] The present invention also provides a computer program product, characterized in that: when the computer program product is executed by a processor, the steps of the method described above are implemented.

[0032] The advantages of the present invention compared with the prior art are:

[0033] (1) The present invention innovatively proposes a technical solution for stabilizing the control of an aircraft when the orbit control thrust deviates from the center of mass. By considering the orbit control interference torque and attitude control torque during relative orbit control, the orbit control thrust pulse width limit of each axis is given. The orbit control original value calculated by the LQG control law based on the relative state deviation is limited and then output to each orbit control thruster for execution. This can effectively achieve stable relative orbit control when the orbit control thrust deviates from the center of mass.

[0034] (2) The present invention can achieve relative orbit control under different orbit control thrust combination modes.

[0035] (3) The relative orbit control method of the present invention is very convenient for implementation and engineering application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0037] In order to better understand the technical solution of the present invention, the specific implementation methods of the present invention are described below.

[0038] The LQG relative orbit control method proposed in this invention under the condition of orbit control thrust deviating from the center of mass can refer to the main process of Figure 1 , including the following steps:

[0039] Step 1: Obtain the pulse width limit of each axis orbit control according to the attitude control torque of each axis and the interference torque generated by the relative orbit control thrust of each axis;

[0040] Step 2: Calculate the relative state deviation. Based on the relative state deviation and the LQG control law matrix, calculate the original orbital acceleration of each axis to be applied in the current control cycle. Then, based on the original orbital acceleration of each axis, combined with the current spacecraft mass and the scalar of the combined force of each axis of the orbital control thrust, obtain the original orbital pulse width of each axis.

[0041] Step 3: Based on the orbit control pulse width limit of each axis and the inherent minimum control pulse width of the propulsion system, the original orbit control pulse width of each axis is limited to obtain the actual execution amount of the orbit control pulse width of each axis, and the execution amount is distributed to each corresponding orbit control thruster.

[0042] In one possible implementation, step 1 specifically includes the following steps:

[0043] Step 1.1, calculate the attitude control torque of each axis:

[0044] According to the selected combination of attitude control thrusters of each axis, according to the thrust vector of each attitude control thruster in the combination (unit N) and installation position vector (Unit: m) Calculate the attitude control torque vector of each axis (Unit Nm):

[0045]

[0046] Where i∈{X,Y,Z} represents the roll axis (X), pitch axis (Y) and yaw axis (Z), n cia_ is the number of thrusters in the attitude control combination, and × represents the vector product.

[0047] Step 1.2, calculate the relative orbit control torque of each axis:

[0048] According to the selected axis orbit control thruster combination, according to the thrust vector of each orbit control thruster in the combination and installation position vector Calculate the interference torque generated by each axis relative to the orbit control thrust

[0049]

[0050] Among them, n oc_i is the number of thrusters in the orbit control assembly.

[0051] Step 1.3, calculate the pulse width limit of each axis track control:

[0052] Based on the attitude control torque of each axis The interference torque generated by the relative orbit control thrust of each axis Get the track control pulse width limit (Unit: ms):

[0053]

[0054] Among them, i,j∈{X,Y,Z} is the attitude and orbit control thruster combination with the same axis torque, for The maximum absolute value in the vector, for The maximum absolute value in the vector (the two maximum absolute values ​​are in the same position in the two vectors, i.e. coaxial), t cyc is the control software operation cycle (unit: ms), λ is the margin coefficient (λ>1), To round x down, min{x,y} compares the two values ​​of x and y and takes the minimum value.

[0055] In one possible implementation, step 2 specifically includes the following steps:

[0056] Step 2.1, calculate the relative state deviation:

[0057] The actual relative position and speed of the aircraft and the target aircraft are tracked in this cycle Relative position and speed to the expected Calculate relative state deviation

[0058]

[0059] in, The actual relative position velocity vector of the tracking aircraft and the target aircraft in this cycle is: is the actual relative position vector (unit: m), is the actual relative velocity vector (unit: m / s); is the relative position velocity vector expected in this cycle, is the desired relative position vector (unit: m), is the desired relative velocity vector (unit: m / s).

[0060] Step 2.2, calculate the original value of relative orbit control pulse width:

[0061] Based on relative state deviation And LQG control law matrix K (3*6 matrix, given value), calculate the original amount of orbit control acceleration of each axis to be applied in this cycle (Unit: m / s 2 ):

[0062]

[0063] in, is the original value of the orbit control acceleration of each axis.

[0064] Based on the original acceleration of each axis orbit control The current vehicle mass m (unit: kg) and the combined force scalar f of each axis of the orbital control thrust combination oc_i (Unit: N), calculate the original value of each axis track control pulse width (Unit: ms):

[0065]

[0066] in, |·| is the modulus operation of the vector, and round(·) is the rounding operation.

[0067] In one possible implementation, step 3 specifically includes the following steps:

[0068] Step 3.1, calculate the relative orbit control pulse width execution amount:

[0069] Based on the pulse width limit of each axis track and propulsion system minimum control pulse width (Unit: ms, inherent given value of propulsion system), original value of pulse width of each axis orbit control Perform amplitude limiting to obtain the actual execution amount of each axis relative to the track control pulse width

[0070]

[0071] in, is a symbolic function.

[0072] Step 3.2, relative orbit control pulse width execution amount distribution:

[0073] Based on the actual execution amount of each axis track control pulse width The execution amount is distributed to each corresponding orbit control thruster.

[0074] A specific embodiment of the present invention is given below:

[0075] Step 1.1, calculate the attitude control torque of each axis:

[0076] Attitude control thruster combination table

[0077]

[0078] According to the selected combination of each axis attitude control thruster, according to the thrust vector of each thruster in the combination (unit N) and installation position vector (Unit: m) Calculate the attitude control torque vector of each axis (Unit Nm):

[0079]

[0080] Among them, n ac_X＝ n ac_Y =n ac_Z =2 (i.e. each axis attitude control thrust combination consists of two thrusters).

[0081] Note: The torque in the negative direction of each axis is opposite.

[0082] Step 1.2, calculate the relative orbit control torque of each axis:

[0083] Orbital control thruster combination table

[0084]

[0085]

[0086] According to the selected axis orbit control thruster combination, according to the thrust vector of each thruster in the combination and installation location Calculate the interference torque generated by each axis relative to the orbit control thrust

[0087]

[0088] Among them, n oc_X =n oc_Z =2,n oc_Y =1 (i.e. the XZ-axis orbital control thrust combination consists of two thrusters, and the Y-axis orbital control thrust is composed of one thruster).

[0089] Step 1.3, calculate the pulse width limit of each axis track control:

[0090] Based on the attitude control torque of each axis The interference torque generated by the relative orbit control thrust of each axis Compare the same axis torque to obtain the upper limit value of the track control pulse width limit

[0091]

[0092] in, and At the same position (position 2) in both vectors, and At the same position (position 3) in both vectors, t cyc The operating cycle is 250ms, and λ=2 (i.e., a double margin is reserved).

[0093] The X-axis orbit control thrust has no interference torque, so it has no amplitude limit, and the maximum pulse width is 250ms of the operating cycle; the Y-axis orbit control thrust produces a yaw axis interference torque, and the pulse width is limited to 50ms with a double margin; the Z-axis orbit control thrust produces a pitch axis interference torque, and the pulse width is limited to 60ms with a double margin.

[0094] Step 2.1, calculate the relative state deviation:

[0095] The actual relative position velocity between the tracking aircraft and the target aircraft during this period is:

[0096]

[0097] The expected relative position velocity is:

[0098]

[0099] Calculate the relative state deviation of this cycle

[0100]

[0101] Step 2.2, calculate the original value of relative orbit control pulse width:

[0102] Based on relative state deviation and LQG control law matrix K (3*6 matrix, given value),

[0103]

[0104] The original amount of three-axis orbit control acceleration to be applied during this period (Unit: m / s 2 )for:

[0105]

[0106] Based on the original acceleration of each axis The current vehicle mass m = 3000 (unit kg) and the combined force scalar f of each axis of the orbital control thrust combination oc_X =f oc_Z =20 and f oc_Y =25 (unit: N), calculate the original value of each axis track control pulse width as follows:

[0107]

[0108] Step 3.1, calculate the relative orbit control pulse width execution amount:

[0109] Based on the pulse width limit of each axis track and propulsion system minimum control pulse width (Unit: ms, inherent given value of propulsion system), original value of pulse width of each axis orbit control The actual execution amount of each axis track control pulse width is obtained by limiting the amplitude as shown below.

[0110] The absolute value of the original pulse width of the X axis is 126ms, which is within the minimum control pulse width of 20ms and the track control pulse width limit. Therefore, the actual pulse width of the X-axis is the same as the original value:

[0111]

[0112] The absolute value of the original pulse width of the Y axis is 59ms, which is greater than the track control pulse width limit. Therefore, the actual pulse width of the Y-axis needs to be limited:

[0113]

[0114] Z-axis original pulse width absolute value Less than the minimum control pulse width Therefore, the Z axis has no actual execution pulse width:

[0115]

[0116] Step 3.2, relative orbit control pulse width execution amount distribution:

[0117] Based on the actual execution amount of each axis orbit control pulse width, the execution amount is allocated to each corresponding orbit control thruster:

[0118] Track control pulse width distribution table

[0119]

[0120] It will be understood that the present invention is described by way of example, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and any embodiment that falls within the scope of the claims of this application is intended to be within the scope of protection of the present invention.

[0121] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A LQG relative orbit control method with orbit control thrust deviating from the center of mass, characterized in that: include: Step 1: Obtain the pulse width limit of each axis orbit control according to the attitude control torque of each axis and the interference torque generated by the relative orbit control thrust of each axis; Step 2: Calculate the relative state deviation. Based on the relative state deviation and the LQG control law matrix, calculate the original orbital acceleration of each axis to be applied in the current control cycle. Then, based on the original orbital acceleration of each axis, combined with the current spacecraft mass and the scalar force of each axis of the orbital control thrust combination, obtain the original orbital pulse width of each axis. Step 3: Based on the orbit control pulse width limit of each axis and the inherent minimum control pulse width of the propulsion system, the original orbit control pulse width of each axis is limited to obtain the actual execution amount of the orbit control pulse width of each axis, and the execution amount is distributed to each corresponding orbit control thruster.

2. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: In step 1, the pulse width limit of each axis track is as follows: in, represents the pulse width limit of each axis orbit control, i,j∈{X,Y,Z} is the attitude and orbit control thruster combination with the same axis torque, is the attitude control torque of each axis The maximum absolute value in the vector, The interference torque generated by the relative orbit control thrust of each axis The maximum absolute value in the vector, t cyc is the control period, λ is the margin coefficient, take λ>1, To round x down, min{x,y} compares the two values ​​of x and y and takes the minimum value.

3. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: In step 2, the original value of the pulse width of each axis track control is: in, is the original value of the pulse width of each axis track control, is the original value of the orbital acceleration of each axis, m is the current mass of the aircraft, f oc_i is the total force scalar of each axis of the orbit control thrust combination, t cyc is the control period, and round(·) is the rounding operation.

4. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: In step 3, the actual execution amount of each axis relative to the track control pulse width is as follows: in, is the actual execution amount of the relative track control pulse width of each axis, is the original value of the pulse width of each axis track control, The minimum control pulse width for the propulsion system is is the pulse width limit of each axis track control; sgn(x) is the sign function.

5. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: The attitude control torque of each axis is determined by the thrust vector of each attitude control thruster in the combination according to the combination of each axis attitude control thruster. and installation position vector The calculation is as follows: in, Represents the attitude control torque of each axis, i∈{X,Y,Z}, X represents the roll axis, Y represents the pitch axis, Z represents the yaw axis, n ac_i is the number of thrusters in the attitude control assembly, and × represents the vector product.

6. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: The interference torque generated by the relative orbit control thrust of each axis is determined by the thrust vector of each orbit control thruster in the combination according to the combination of each axis orbit control thruster. and installation position vector The calculation is as follows: in, It represents the interference torque generated by each axis relative to the orbit control thrust, i∈{X,Y,Z}, X represents the roll axis, Y represents the pitch axis, Z represents the yaw axis, n oc_i is the number of thrusters in the orbit control assembly, and × represents the vector product.

7. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: The relative state deviation is the actual relative position and speed of the aircraft and the target aircraft tracked by this control cycle. Relative position and speed to the expected The calculation is as follows: in, is the actual relative position vector, is the actual relative velocity vector; is the desired relative position vector, is the desired relative velocity vector.

8. The LQG relative orbit control method with orbit control thrust deviating from the center of mass according to claim 1, characterized in that: The original value of the track control acceleration of each axis is calculated as follows: Among them, K is the 3*6 LQG control law matrix, is the relative state deviation.

9. An onboard computing terminal, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method according to any one of claims 1 to 8 when executing the computer program.

10. A computer program product, characterized in that: When the computer program product is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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