WO2016111317A1 - 軌道制御装置および衛星 - Google Patents
軌道制御装置および衛星 Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/242—Orbits and trajectories
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/244—Spacecraft control systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/26—Guiding or controlling apparatus, e.g. for attitude control using jets
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
- G05D1/08—Control of attitude, i.e. control of roll, pitch, or yaw
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
- B64G1/00—Cosmonautic vehicles
- B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
- B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
- B64G1/244—Spacecraft control systems
- B64G1/245—Attitude control algorithms for spacecraft attitude control
Definitions
- the present invention relates to an orbit control device for maintaining the orbit of a satellite and a satellite equipped with the orbit control device.
- a satellite or spacecraft flying in a circular orbit over an altitude of about 36000km above the equator appears to be roughly stationary when viewed from the ground observers because the period of orbital motion and the rotation period of the Earth are almost the same. .
- Such satellites are called geostationary satellites.
- geostationary satellites are subject to various perturbations such as the tidal force of the earth and the sun, the perturbation due to the non-uniformity of the earth's gravitational potential, and the solar radiation pressure. Go. For this reason, it is necessary for the satellite to perform thruster injection for correcting variations in latitude and longitude.
- Thruster injection that corrects longitude fluctuations is generally called east-west control, and control that corrects latitude fluctuations is generally called north-south control.
- east-west control and north-south control to keep the satellite latitude and longitude within a desired range is generally called orbit maintenance.
- Non-patent document 1 is an example of a technique for realizing orbit maintenance of a geostationary satellite.
- orbit maintenance control is performed using a nonlinear optimal control method for a geostationary satellite in which electric propulsion devices are arranged in a petal shape.
- four thrusters are jetted simultaneously, and the trajectory holding accuracy is about 0.005 °.
- Non-Patent Document 1 the injection amount of the electric propulsion device is calculated by a non-linear programming method in order to realize highly accurate track maintenance with low propellant consumption. Therefore, it requires a large calculation cost and is not suitable for calculating the injection law.
- An object of the present invention is to calculate a thruster injection law for performing highly accurate orbit maintenance while suppressing propellant consumption at a low calculation cost.
- An orbit control device is a satellite orbit control device including four thrusters arranged on a satellite in directions different from each other in directions away from the center of mass of the satellite. From the orbit determination unit that determines the average orbital element and the time change rate of the average orbital element, the target value setting unit that sets the target value of the average orbital element, the average orbital element, the time change rate and the target value of the average orbital element, The control amount calculation unit that calculates the control amount of the average orbital element and the movement of the satellite are expressed by the orbital element, taking into account the combination of the thruster placement angle and the out-of-orbital motion and in-orbital motion due to multiple thruster injection amounts.
- Control amount calculation unit by combining the thruster injection that mainly controls the out-of-track surface direction and the thruster injection that mainly controls the in-plane direction.
- a distribution unit that calculates the injection timing and injection amount of the thruster for realizing the calculated control amount of the average orbital element, and a thruster control unit that controls the thruster according to the injection timing and injection amount calculated by the distribution unit; Prepare.
- FIG. 1 It is a block diagram which shows the structure of the orbit control apparatus of the satellite which concerns on Embodiment 1 of this invention. It is a figure which shows arrangement
- 3 is a flowchart showing an operation of a control amount calculation unit according to the first embodiment.
- 3 is a flowchart showing an operation of a distribution unit according to the first embodiment.
- 10 is a flowchart illustrating an operation of a distribution unit according to the second embodiment.
- 10 is a flowchart illustrating an operation of a distribution unit according to the third embodiment. It is a figure which shows the example of the hardware constitutions of this invention. It is a figure which shows the example of the hardware constitutions of this invention.
- the injection amount of the electric propulsion device is determined by nonlinear optimization calculation in order to realize highly accurate orbit maintenance, which requires a large calculation cost, and the injection amount is calculated by a satellite-borne computer. Not suitable.
- the present invention provides an orbit control device and a satellite that suppress power consumption or the amount of propellant and that maintain the orbit of the satellite with high accuracy.
- FIG. 1 is a block diagram showing the configuration of a satellite orbit control apparatus according to Embodiment 1 of the present invention.
- the orbit control device 9 is mounted on the satellite 7.
- a geostationary satellite is assumed as the satellite 7.
- the satellite 7 includes four thrusters 91, 92, 93, and 94 and an orbit control device 9 that controls the thrusters.
- the trajectory control device 9 includes a target value setting unit 1, a control amount calculation unit 2, a distribution unit 5, a trajectory determination unit 8, and a thruster control unit 6.
- the control amount calculation unit 2 includes a feedforward control amount calculation unit 3 and a feedback control amount calculation unit 4.
- the orbit control device 9 determines the injection timing and injection amount of each of the thrusters 91, 92, 93, 94 in order to maintain the orbit of the satellite 7, and the thrusters 91, 92, 93, 94 with the determined injection timing and injection amount. Control to spray.
- the orbit determination unit 8 includes, for example, GPS information, satellite range and range rate information with respect to the ground station, satellite azimuth / elevation angle information obtained by observation with a ground optical camera, and the like.
- the average orbital element of the satellite 7 and the time change rate of the average orbital element are determined.
- the average orbit element is an average orbit element obtained by removing a periodically varying component from the orbit element of the satellite.
- the target value setting unit 1 sets a target value of an average orbit element suitable for realizing the orbit maintenance of the satellite 7.
- the target value of the average orbital element is a target value of the average longitude longitude, average eccentricity vector, average inclination angle vector, or the like.
- the control amount calculation unit 2 calculates the average eccentricity of the satellite 7 based on the average orbit element calculated by the orbit determination unit 8, the time change rate of the average orbit element, and the target value of the average orbit element set by the target value setting unit 1.
- the feedforward control amount and the feedback control amount of the rate vector and the average inclination angle vector are calculated.
- the distribution unit 5 includes the control amount of the average inclination angle vector calculated by the control amount calculation unit 2, the target value of the average direct point longitude set by the target value setting unit 1, the average trajectory element calculated by the trajectory determination unit 8, and The time change rate of the average orbital element is received, and the control amount of the average eccentricity vector and the average inclination angle vector and the control amount of the average direct point longitude for maintaining the average direct point longitude in the vicinity of the target value are calculated. Then, the injection timing and the injection amount of the thruster for realizing the calculated control amount are calculated.
- the thruster control unit 6 causes the thrusters 91, 92, 93, and 94 to perform injection according to the injection timing and injection amount of the thruster calculated by the distribution unit 5.
- thrusters 91, 92, 93, 94 are arranged in a petal shape on the anti-earth surface of the satellite 7.
- the thrusters 91, 92, 93, 94 are ejected in different directions on a straight line passing through the center of mass of the satellite 7 in a direction away from the central celestial body (Earth) as seen from the center of mass of the satellite 7.
- FIG. 2 shows the arrangement of the thrusters.
- M.M. Center of Mass
- central celestial typically a satellite center of mass C. from the center of the earth M.M.
- the Z B axis coincides with the velocity direction of the satellite, and the Y B axis forms a right-handed coordinate system with respect to the X B axis and the Z B axis.
- the thrusters 91, 92, 93, and 94 are directed in the northwest direction, the northeast direction, the southwest direction, and the southeast direction, respectively.
- the thrusters 91, 92, 93, and 94 are also referred to as NW thrusters, NE thrusters, SW thrusters, and SE thrusters, respectively.
- the angle ⁇ 2 is an angle thrusters 91, 92, 93 and 94 makes with the Y B axis.
- the angle phi the line obtained by projecting the line connecting the center of mass of the thruster and satellite 7 thrusters 91, 92, 93 and 94 in the X B Z B plane, an angle formed between the X B axis.
- FIG. 7 is a diagram illustrating an example of a hardware configuration.
- the satellite 7 includes a receiving unit 111 that receives a GPS signal, a range and a range rate signal, a trajectory control device 9 that receives a signal from the receiving unit 111 and determines a trajectory to control a thruster, and a control target. Thrusters 91, 92, 93 and 94 are provided.
- the trajectory control device 9 controls the thruster based on the calculation result of the distribution circuit 5 and the processing circuit 101 that realizes the functions of the target value setting unit 1, the control amount calculation unit 2, the distribution unit 5, and the trajectory determination unit 8.
- a thruster control unit 6 is provided. Even if the processing circuit is dedicated hardware, a CPU that executes a program stored in a memory (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP) It may be.
- a memory Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, micro
- FIG. 8 is a diagram illustrating another example of the hardware configuration of the present embodiment.
- the satellite 7 includes a receiving unit 111 that receives a GPS signal, a range and a range rate signal, a trajectory control device 9 that receives a signal from the receiving unit 111 and determines a trajectory to control a thruster, and a control target.
- the thrusters 91, 92, 93, and 94 may be provided.
- the processing circuit 101 in FIG. 7 corresponds to a processor (CPU) 102 and a memory 103.
- the processing circuit 101 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these. To do.
- the functions of the target value setting unit 1, the control amount calculation unit 2, the distribution unit 5, and the trajectory determination unit 8 may be realized by a processing circuit, or the functions of the units may be realized by a processing circuit. .
- the processing circuit is the processor (CPU) 102
- the functions of the target value setting unit 1, the control amount calculation unit 2, the distribution unit 5, and the trajectory determination unit 8 are realized by software, firmware, or a combination of software and firmware.
- Software and firmware are described as programs and stored in a memory.
- the processing circuit reads out and executes the program stored in the memory, thereby realizing the function of each unit.
- the trajectory control device 9 includes a memory for storing a program that, when executed by the processing circuit 101, results in the target setting step, the control amount calculation step, and the distribution step being executed as a result. These programs can be said to cause the computer to execute the procedures and methods of the target value setting unit 1, the control amount calculation unit 2, the distribution unit 5, and the trajectory determination unit 8.
- the memory corresponds to, for example, a nonvolatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. To do.
- a nonvolatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like.
- the memory includes an average orbital element determined by the orbit determination unit 8, a time change rate of the average orbital element, a target value of the average orbital element set by the target value setting unit 1, and a control amount calculation unit 2
- the feedforward control amount and the feedback control amount of the average trajectory element calculated in step (1), the injection amount and injection timing of each thruster calculated by the distribution unit 5 are stored.
- the information stored in the above-mentioned memory is appropriately read out, used for processing, and corrected.
- a part is implement
- a part is implement
- the function of the trajectory determination unit 8 is realized by a processing circuit as dedicated hardware
- the function of the bag distribution unit 5 is realized by the processing circuit reading and executing a program stored in the memory. Is possible.
- the processing circuit 101 corresponds to the processor 102 in FIG. 8
- the memory corresponds to the memory 103 in FIG.
- the processing circuit can realize the above functions by hardware, software, firmware, or a combination thereof.
- the operation of each part of the trajectory control device 9 will be described.
- the target value setting unit 1 sets a target value for the average orbital element of the satellite 7.
- the average average point longitude ⁇ M defined by ⁇ g is a time average of the average point longitude ⁇ M.
- the average trajectory element may be used as the average trajectory element.
- eccentricity vector draws a circular trajectory of radius e n in one year due to the influence of solar radiation pressure.
- the size of the radius e n is the mass of the satellite 7, determined by the optical constants of the effective area, and a satellite surface.
- the control amount of the average eccentricity vector in the control amount calculation unit 2 can be suppressed.
- the control amount calculation unit 2 calculates the control amount of the average orbital element from the average orbital element, the time change rate of the average orbital element, and the target value.
- the control amount calculation unit 2 includes a feedforward control amount calculation unit 3 and a feedback control amount calculation unit 4.
- the feedforward control amount calculation unit 3 calculates the feedforward control amount of the average eccentricity vector and the average inclination angle vector of the satellite 7 based on the time change rate of the average orbit element calculated by the orbit determination unit 8.
- the average eccentricity vector and average inclination angle vector of the satellite 7 are calculated based on the average orbit element calculated by the orbit determination unit 8 and the target value of the average orbit element set by the target value setting unit 1. Calculate the feedback control amount.
- operations of the feedforward control amount calculation unit 3 and the feedback control amount calculation unit 4 will be described.
- the feedforward control amount calculation unit 3 calculates the feedforward control amount of the average eccentricity vector and the average inclination angle vector of the satellite 7 based on the time change rate of the average orbit element calculated by the orbit determination unit 8.
- the time rate of change at time t 0 of the average eccentricity vector e as the 'x0, e' y0 define the time rate of change at time t 0 of the average inclination angle vector i and 'x0, i' y0.
- changes ⁇ e and ⁇ i per cycle of the average eccentricity vector and average inclination angle vector are expressed by the following equations (1) and (2).
- the subscript “ T ” on the right shoulder represents transposition.
- the period T of the orbital movement of the satellite 7 is equal to the rotation period of the earth.
- a constant multiple of ⁇ e and ⁇ i is used as the feedforward control amount of the average eccentricity vector and the average inclination angle vector.
- ⁇ e FF ⁇ (3/4) ⁇ e (3)
- ⁇ i FF ⁇ (3/4) ⁇ i (4)
- the average eccentricity vector and average inclination angle vector of the satellite 7 are calculated based on the average orbit element calculated by the orbit determination unit 8 and the target value of the average orbit element set by the target value setting unit 1. Calculate the feedback control amount.
- De e 0 -e ref
- Di i 0 -i ref.
- PID control PID control as in the following formulas (5) and (6).
- k ep , k ed, and k ed are a proportional gain, a differential gain, and an integral gain, respectively, for calculating the feedback control amount of the average eccentricity vector.
- k ip , k id, and k ii are respectively a proportional gain, a differential gain, and an integral gain for calculating the feedback control amount of the average inclination angle vector.
- the control amount output by the control amount calculation unit 2 is the sum of the feedforward control amount calculated by the feedforward control amount calculation unit 3 and the feedback control amount calculated by the feedback control amount calculation unit 4. If the control amounts of the average eccentricity vector and the average inclination angle vector output by the control amount calculation unit 2 are defined as ⁇ e and ⁇ i, respectively, ⁇ e and ⁇ i are expressed as the following equations (7) and (8).
- Control of the average eccentricity vector is control in the in-orbit plane direction of the satellite 7, and control of the average inclination angle vector is control in the out-of-orbit plane direction of the satellite 7.
- the control amount calculation unit 2 calculates the control amounts of the average eccentricity vector and the average inclination angle vector according to the calculations of the equations (1) to (8).
- the control amount calculation unit 2 realizes highly accurate trajectory control by the feedforward control amount, and enhances the stability and robustness of the control system by feedback control. The operation of the control amount calculation unit 2 has been described above, but will be described below with reference to a flowchart.
- FIG. 3 is a flowchart showing the operation of the control amount calculation unit 2 according to the first embodiment.
- the control amount calculation unit 2 includes a feedforward control amount calculation unit 3 and a feedback control amount calculation unit 4. This will be described below with reference to a flowchart.
- the feedforward control amount calculation unit 3 receives the time change rate of the average trajectory element from the trajectory determination unit 8 (step S250).
- step S251 calculates the amount of change ⁇ e, ⁇ i per orbit of the average eccentricity vector and average inclination angle vector (Sstep 251).
- step S252 values obtained by multiplying ⁇ e and ⁇ i by a constant are set as feedforward control amounts ⁇ eFF and ⁇ iFF (step S252).
- the feedforward control amount calculation unit 3 executes the above steps S250 to S252.
- the feedforward control amount calculation unit 3 may be processed by the processing circuit 101 or the processor 102 or may be realized by an independent processing circuit. Further, the feedforward control amount calculation unit 3 reads the time change rate of the average orbital element from the memory, and stores the calculated changes ⁇ e and ⁇ i and the feedforward control amounts ⁇ eFF and ⁇ iFF in the memory.
- step S253 the feedback control amount calculation unit 4 receives the average trajectory element from the trajectory determination unit 8, and receives the target value of the average trajectory element from the target value setting unit 1 (step S253).
- step S254 calculates differences De and Di between the trajectory determination value of the average trajectory element and the target value (step S254).
- step S255 feedback control amounts ⁇ eFB and ⁇ iFB for the average eccentricity vector and the average inclination angle vector are calculated (step S255).
- the feedback control amount calculation unit 4 executes the above steps S253 to S255.
- the feedback control amount calculation unit 4 may be processed by the processing circuit 101 or the processor 102, or may be realized by an independent processing circuit. Further, the feedback control amount calculation unit 4 reads out the average trajectory element, the target value of the average trajectory element, and the like from the memory, and stores the calculated differences De and Di and the feedback control amounts ⁇ eFB and ⁇ iFB in the memory.
- step S256 the feedforward control amount and the feedback control amount are finally added to calculate the control amount of the average eccentricity vector and the average inclination angle vector (step S256). Further, in step S257, the calculated control amount of the average trajectory element is transferred to the distribution unit 5 (step S257).
- the above-described steps S256 and S257 are executed by the control amount calculation unit 2.
- the control amount calculation unit 2 stores the control amounts of the average eccentricity vector and the average inclination angle vector in the memory.
- the control amount of the average eccentricity vector and the average inclination angle vector calculated by the control amount calculation unit 2 the target value of the average direct point longitude set by the target value setting unit 1, and the trajectory determination
- the average trajectory element calculated by the unit 8 and the time change rate of the average trajectory element are received.
- the thruster injection timing and the injection amount for realizing the control amount are calculated.
- of the control amount ⁇ i of the average inclination angle vector at the time t 0 calculated by the control amount calculation unit 2 and the deflection angle ⁇ . That is, ⁇ i is expressed as the following formula (9). ⁇ i [ ⁇ i cos ⁇ ⁇ i sin ⁇ ] T (9) However, ⁇ i > 0 is satisfied.
- the distribution unit 5 determines the timing of the first north-south control (out-orbit control).
- control for correcting fluctuations in longitude is generally called east-west control
- control for correcting fluctuations in latitude is generally called north-south control.
- An equation related to the tilt angle vector indicates that the optimum timing for the north-south control is when the average longitude of the satellite 7 coincides with ⁇ or ⁇ + ⁇ .
- ⁇ is the circumference ratio. Therefore, when the average longitude lambda 0 of the satellite 7 at time t 0 coincides with beta or beta + [pi, performs first north-south control at time t 0.
- mean longitude lambda mean longitude lambda 0 and if 0 matches the beta is divided into two types in the case of matching the beta + [pi, the operation of the distributor 5.
- the distribution unit 5 calculates the timing and the injection amount of the first and second north-south control.
- ⁇ 1 ⁇ (10)
- ⁇ 2 ⁇ + ⁇ (11)
- SW thrusters and SE thrusters are used in the first north-south control
- NW thrusters and NE thrusters are used in the second north-south control.
- the total injection amount of SW thrusters and SE thrusters and f S during the first north-south control, the total injection amount of NW thrusters and NE thruster in the second north-south control is defined as f N.
- F S and f N are as follows: It is determined as follows.
- A na ⁇ i ( ⁇ e x cos ⁇ + ⁇ e y sin ⁇ ) / (sin ⁇ cos ⁇ ) (12)
- B na ⁇ i / cos ⁇ (13)
- the angle ⁇ is the angle of thruster 91, 92, 93 and 94 makes with the Y B axis, the angle phi, the line segment connecting the center of mass of the thruster and satellite 7 thrusters 91, 92, 93 and 94 line projected onto the X B Z B plane, an angle formed between the X B axis ( Figure 2).
- the variables A and B have a speed dimension.
- variable B is obtained by substituting the component of impulse in the Y B axis direction generated by the SW thruster and SE thruster injection into the Gaussian planetary equation relating to the tilt angle vector.
- variable A is obtained by substituting the components of X B-axis direction impulse caused by the injection of SW thrusters and SE thrusters Gaussian planet equations for eccentricity vector.
- the distribution unit 5 gives f S and f N according to the following expression (14) according to the sizes of A and B.
- the distribution unit 5 calculates a control amount for controlling the average eccentricity vector (in-plane control).
- the average eccentricity vector is controlled by applying a force in the orbital radial direction to the satellite 7 by injecting the NW thruster and the SE thruster equally, or by injecting the NE thruster and the SW thruster equally. Achieve.
- Average longitude when controlling the mean eccentricity vector and lambda r defines a control amount of the track radially applied to the satellite at the time and f r.
- ⁇ r is given by the following equation (15).
- the distribution unit 5 restricts the distribution rate ⁇ S of the SW thruster and the SE thruster in the first north-south control and the distribution rate ⁇ N of the NW thruster and the NE thruster in the second north-south control.
- the evaluation function J in the optimization problem can be set as the following expression (17), for example.
- the constraint condition can be set as in the following formula (18), for example.
- Expression (18) is a constraint condition for controlling the average directly below longitude to the target value ⁇ Mref .
- .DELTA..LAMBDA Mtotal an average mean directly below the satellite 7 caused by the mean eccentricity vector control mean longitude lambda 1 during the first north-south control and the average longitude lambda 2 2 nd north-south control in the in the average longitude lambda r This is the sum of the changes in point longitude, and can be expressed as the following equation (19).
- Equation (19) is obtained by adding the first north-south control at the average longitude ⁇ 1, the second north-south control at the average longitude ⁇ 2 , and the average eccentricity vector control at the average longitude ⁇ r to the Gaussian planetary equation for the average nadir point longitude. obtained by substituting X B-axis direction impulse occurring.
- ⁇ Mref is a target holding value of the longitude point directly below the satellite 7 and is set by the target value setting unit 1.
- Equation (18) ⁇ MT is the average average point longitude of satellite 7 one cycle after the first north-south control, and can be expressed as Equation (20) below.
- ⁇ MT ⁇ M0 + ⁇ ' M0 T + (1/2) ⁇ " M0 T 2 + ⁇ Mtotal -(3 / a) sin ⁇ sin ⁇ [(2 ⁇ S -1) f S + (1/2) (2 ⁇ N -1) f N ] T (20)
- the first three terms are obtained by time-integrating the angular velocity and angular acceleration of the average average direct point longitude immediately before executing the first north-south control.
- ⁇ ′ M0 , ⁇ ′ M0 , and ⁇ ′′ M0 are the average average nadir longitude, the angular velocity of the average average nadir longitude, and the angular acceleration of the average average nadir longitude of the satellite 7 at time t 0 .
- the distribution unit 5 is given by the equation (17) while satisfying the constraint condition for controlling the average direct point longitude given by the equation (18) to the target value ⁇ Mref.
- the distribution ratios ⁇ S and ⁇ N are determined so that the evaluation function J is minimized.
- the distribution unit 5 determines the injection amounts of the first and second north-south control from the calculated distribution rates ⁇ S and ⁇ N as shown in the following equations (21) and (22).
- the subscripts NW, NE, SW, and SE of the injection amount f represent an NW thruster, an NE thruster, an SW thruster, and an SE thruster, respectively.
- the subscript 1 indicates the first time, and the subscript 2 indicates the second time.
- Formula (21) shows the injection amount of each thruster in the first north-south control.
- Formula (22) shows the injection amount of each thruster in the second north-south control.
- f NW2 ⁇ N f N
- f NE2 (1 ⁇ N ) f N
- the distribution unit 5 passes the calculated injection timing and injection amount of the north-south control and the average eccentricity vector control to the thruster control unit 6.
- the thruster control unit 6 controls the thrusters 91, 92, 93, and 94 according to the injection timing and the injection amount calculated by the distribution unit 5.
- the distribution unit 5 calculates the timing of the first and second north-south control and the injection amount.
- lambda 1 Average longitude when performing the second north-south control, when referred to as lambda 2 is the following formula (23) given by (24).
- ⁇ 1 ⁇ + ⁇ (23)
- ⁇ 2 ⁇ + 2 ⁇ (24)
- NW thrusters and NE thrusters are used, and in the second north-south control, SW thrusters and SE thrusters are used.
- the total injection amount of NW thrusters and NE thruster during the first north-south control and f N, a total injection quantity of SW thrusters and SE thrusters in the second north-south control is defined as f S.
- f S a total injection quantity of SW thrusters and SE thrusters in the second north-south control
- the orbital length radius and the average orbital angular velocity of the satellite 7 are represented as a and n, respectively.
- variables A and B depending on ⁇ e and ⁇ i are defined as in the following equations (25) and (26).
- A na ⁇ i ( ⁇ e x cos ⁇ + ⁇ e y sin ⁇ ) / (sin ⁇ cos ⁇ ) (25)
- B na ⁇ i / cos ⁇ (26)
- Angle ⁇ is the angle of thruster 91, 92, 93 and 94 makes with the Y B axis, the angle ⁇ for the line segment connecting the center of mass of the thruster and satellite 7 thrusters 91, 92, 93 and 94 X B Z line segment projected on B plane, an angle formed between the X B axis ( Figure 2).
- the distribution unit 5 gives f S and f N according to the following expression (27) according to the sizes of A and B.
- the distribution unit 5 calculates a control amount for controlling the average eccentricity vector.
- the average eccentricity vector is controlled by applying a force in the orbital radial direction to the satellite 7 by injecting the NW star and SE thrusters equally, or by injecting the NE thruster and SW thrusters equally. Achieve.
- Average longitude when controlling the mean eccentricity vector and lambda r defines a control amount of the track radially applied to the satellite at the time and f r.
- ⁇ e average eccentricity vector and the unit vector [rho beta provides a mean longitude lambda r when controlling the mean eccentricity vector by the following equation (28).
- the distribution unit 5 constrains the distribution rate ⁇ N of the NW thruster and the NE thruster in the first north-south control and the distribution rate ⁇ S of the SW thruster and the SE thruster in the second north-south control.
- the evaluation function J in the optimization problem can be set as the following expression (30), for example.
- the constraint condition can be set as in the following equation (31), for example.
- ⁇ MT ⁇ Mref ⁇ (1/2) ⁇ Mtotal (31)
- .DELTA..LAMBDA Mtotal is first north-south control in the average longitude lambda 1, 2 nd north-south control in mean longitude lambda 2, and the average mean of satellite 7 caused by the mean eccentricity vector control in the average longitude lambda r This is the sum of the change amount of the direct point longitude and can be expressed as the following equation (32).
- ⁇ Mtotal 2 tan ⁇ cos ⁇ i +2
- ⁇ Mref is a target holding value of the longitude directly below the satellite 7 and is set by the target value setting unit 1.
- ⁇ MT is the average average point longitude of satellite 7 after one orbit cycle has elapsed since the first north-south control, and can be expressed as Equation (33) below.
- ⁇ MT ⁇ M0 + ⁇ ' M0 T + (1/2) ⁇ " M0 T 2 + ⁇ Mtotal -(3 / a) sin ⁇ sin ⁇ [(2 ⁇ N -1) f N + (1/2) (2 ⁇ S -1) f S ] T (33)
- ⁇ M0 , ⁇ ′ M0 and ⁇ ′′ M0 are the average average nadir longitude, the average average nadir velocity, and the average average nadir acceleration of the satellite 7 at time t 0, respectively.
- the distribution unit 5 satisfies the constraint condition given by the equation (31), and the distribution rate ⁇ S so that the evaluation function J given by the equation (30) is minimized.
- ⁇ N is determined.
- the distribution unit 5 determines the first and second north-south injection amounts from the calculated distribution rates ⁇ S and ⁇ N as in the following equations (34) and (35).
- the subscript of the injection amount f is the same as in the equations (21) and (22).
- Formula (34) shows the injection amount of each thruster in the first north-south control.
- Formula (35) shows the injection amount of each thruster in the second north-south control.
- Equations (12) to (14), (16) and (18) to (20) are equations that take into account the coupling of the out-of-orbital motion and the in-orbital motion.
- the distribution unit 5 solves an equation that takes into account the coupling of out-of-plane motion and in-plane motion by a plurality of thruster injection amounts, and performs thruster injection that mainly controls the out-of-plane direction and thruster injection that mainly controls the in-plane direction.
- the injection timing and the injection amount of the thruster for realizing the control amount of the average trajectory element calculated by the control amount calculation unit 2 are calculated.
- the distribution unit 5 passes to the thruster control unit 6 the injection timing and the injection amount of each thruster of the north-south control and the average eccentricity vector control calculated above.
- the thruster control unit 6 controls the thrusters 91, 92, 93, and 94 according to the injection timing and the injection amount calculated by the distribution unit 5.
- FIG. 4 is a flowchart showing the operation of the distribution unit 5 according to the first embodiment.
- the distribution unit 5 first calculates the magnitude and declination of the control amount of the average inclination angle vector represented by the equation (9) (step S01). And the timing of north-south control is determined (step S02).
- the injection timings ⁇ 1 and ⁇ 2 of the north-south control are calculated by the equations (10) and (11), and the total injections of each.
- the quantities f S and f N are calculated from the equations (12) to (14) (step S03).
- the distribution unit 5 stores in the memory the magnitude and declination of the control amount of the average inclination angle vector, the north and south control injection timings ⁇ 1 and ⁇ 2 , and the total injection amounts f S and f N.
- the injection timing lambda r of the mean eccentricity vector control of injection quantity f r is calculated by equation (15) and (16) (step S04). Then, the distribution ratios ⁇ S and ⁇ N that minimize the evaluation function J of Expression (17) are determined under the constraint condition of Expression (18) (Step S05).
- the distribution unit 5 calculates the injection amount of each thruster for the first time and the second time by the equations (21) and (22) from the distribution rates ⁇ S and ⁇ N (step S06). Then, the calculated injection timing and injection amount are sent to the thruster controller 6 (step S07).
- the distribution unit 5 stores the injection timing ⁇ r and the injection amount fr of the average eccentricity vector control , the distribution rates ⁇ S and ⁇ N , and the injection timing and the injection amount in a memory.
- the distribution unit 5 uses the equations (23) and (24). ), The injection timings ⁇ 1 and ⁇ 2 of the north-south control are calculated, and the respective total injection amounts f S and f N are calculated from the equations (25) to (27) (step S09). The distribution unit 5 stores the north-south control injection timings ⁇ 1 and ⁇ 2 and the total injection amounts f S and f N in a memory.
- Distributor 5 is then injection timing lambda r and the injection quantity f r of the mean eccentricity vector control, is calculated by equation (28) and (29) (step S10). Then, the distribution ratios ⁇ S and ⁇ N that minimize the evaluation function J of Equation (30) are determined under the constraint condition of Equation (31) (Step S11). The distribution unit 5 calculates the injection amount of each thruster for the first time and the second time by the equations (34) and (35) from the distribution rates ⁇ S and ⁇ N (step S12). Then, the calculated injection timing and injection amount are sent to the thruster controller 6 (step S07). The distribution unit 5 stores in memory the injection timing ⁇ r and injection amount f r of the average eccentricity vector control, the distribution rates ⁇ S and ⁇ N, and the injection amounts of the first and second thrusters.
- step S02 and step S08 when the average longitude ⁇ 0 does not coincide with the declination ⁇ or ⁇ + ⁇ (step S02; N, step S08; N), neither injection amount calculation nor injection is performed (step S13). End the process.
- the distribution unit 5 analytically analyzes the Gaussian planetary equation including the coupling between the in-orbit surface and the out-of-orbit surface depending on the thruster arrangement angle and multiple thruster injections. By solving, it is possible to calculate the thruster injection law that suppresses the consumption propellant at a low calculation cost.
- the satellite can be highly accurately controlled while suppressing power consumption. Can keep track.
- the optimum north-south control injection timing can be calculated based on the control amount of the average inclination angle vector, and high-precision north-south control can be realized. Further, it becomes possible to simultaneously control the average average direct point longitude, the average inclination angle vector, and the average eccentricity vector in the north-south control.
- the average eccentricity vector is controlled once per orbit, so that the average eccentricity vector can be held near the target value. It becomes possible to maintain longitude in the vicinity of the target value with high accuracy.
- the interval between the north-south control and the average eccentricity vector control can be set at a quarter of the orbit, and it is possible to avoid the timing of thruster injection of the north-south control and the average eccentricity vector control from overlapping.
- Embodiment 2 the timing at which thruster injection is possible in one round of the orbit is fixed in advance. Then, the injection amount of the thruster 2 to 4 times and the propriety of the injection are determined according to the control amount of the average eccentricity vector and the average inclination angle vector calculated by the control amount calculation unit for each timing.
- the configuration of the second embodiment is the same as that of the first embodiment, only the operation of the distribution unit 5 in the trajectory control device 9 is different.
- Other target value setting unit 1, control amount calculation unit 2, thruster control unit 6 and trajectory determination unit 8 are the same as those in the first embodiment.
- the distribution unit 5 controls the average eccentricity vector and the average inclination angle vector control amount calculated by the control amount calculation unit 2, the target value of the average direct point longitude set by the target value setting unit 1,
- the average trajectory element calculated by the trajectory determination unit 8 and the time change rate of the average trajectory element are received.
- the injection timing and the injection amount of the thruster for realizing the control amount of the average direct point longitude for maintaining the control amount of the average eccentricity vector and the average inclination angle vector and the average direct point longitude in the vicinity of the target value are calculated.
- the thruster injection timing is set to a maximum of four times in one cycle.
- Each timing is expressed as ⁇ 1 , ⁇ 2 , ⁇ 3 , ⁇ 4 using the average longitude ⁇ , and is given by the following equations (48) to (51).
- ⁇ 1 ⁇ C (48)
- ⁇ 2 ⁇ 1 + ⁇ / 2 (49)
- ⁇ 3 ⁇ 1 + ⁇ (50)
- ⁇ 4 ⁇ 1 + 3 ⁇ / 2 (51)
- ⁇ C is the first thruster injection timing given in advance.
- thruster injection is performed with the phase being separated by ⁇ / 2 at equal intervals from the first thruster injection.
- ⁇ C, ⁇ 1 , ⁇ 2 , ⁇ 3 , and ⁇ 4 can be selected from values other than the above-described method.
- the number of thruster injections is four here, the number of thruster injections may be suppressed to two from the actually calculated control amount. The following describes the control force required to maintain the trajectory and how to calculate the thruster injection amount.
- .delta.e i determines the f hi by case analysis on the magnitude relationship .delta.i i. In this case, priority is given to realizing the control amount of the average eccentricity vector. If f hi is determined from the arrangement of the thrusters, f ri is automatically determined. When the case became .delta.e i> .delta.i i would fit the control amount of the average tilt angle vector, the control amount of the average eccentricity vector becomes insufficient. Therefore, in such a case, f hi is determined based on the control amount of the average eccentricity vector.
- a is an orbital radius
- n is an average orbital angular velocity
- ⁇ and ⁇ are angles given in FIG.
- the thruster injection for giving this f ⁇ i is the distribution of the injection quantity to the SW thruster and SE thruster or the NW thruster and NE thruster when giving the out-of-plane control force f hi (in the case of electric propulsion, the injection) This is achieved by allocating time).
- This distribution amount can be uniquely determined based on the thruster arrangement angle when f hi and f ⁇ i are given.
- f hi varies for each control cycle, and in some cases, a sufficient total f ⁇ i cannot be obtained by four times of control. In such a case, the injection of two or one thruster is performed in the first thruster injection, and the necessary f ⁇ is additionally given.
- the distribution unit 5 passes the above calculation result to the thruster control unit 6.
- the basic operation in the second embodiment is as described above. However, when aiming at further saving of the propellant, the following control is performed when calculating the out-of-plane control amount f hi .
- the average inclination angle vector error ⁇ is a sufficiently small value, for example,
- the number of thruster injections is reduced to three or less by adjusting the control amount only to the control amount necessary for controlling the average eccentricity vector.
- FIG. 5 is a flowchart showing the operation of the distribution unit 5 according to the second embodiment.
- Distributor unit 5 controls the amount of average eccentricity vector and the average tilt angle vector, and stores the target value and .delta.e i of the average mean nadir longitude, reads .delta.i i from the memory, the out-of-plane control amount f hi the memory.
- the distribution unit 5 determines the distribution of the injection amount of each thruster at each thruster injection timing (step S26), and determines the fixed injection timing and the injection amount of each thruster as a thruster control unit. 6 (step S27).
- the distribution unit 5 stores the distribution of the injection amount of each thruster at each thruster injection timing in the memory.
- the control amount of the average eccentricity vector and the average inclination angle vector and the control amount of the average direct point longitude for maintaining the average direct point longitude in the vicinity of the target value are realized in the second embodiment.
- the injection timing and injection amount of the thruster to be calculated are calculated.
- the injection interval between the thruster injections can be fixed, and the orbit maintenance error in the longitude direction caused by the fluctuation of the control time interval can be reduced.
- Embodiment 3 In the third embodiment, two out of four thrusters are combined to perform north-south control once per orbit, and two east thrusters are controlled twice per orbit.
- the configuration of the third embodiment is the same as that of the first embodiment, only the operation of the distribution unit 5 in the trajectory control device 9 is different.
- Other target value setting unit 1, control amount calculation unit 2, thruster control unit 6, satellite 7 and orbit determination unit 8 are the same as those in the first embodiment. Since only the distribution unit 5 is different from the first embodiment, the distribution unit 5 will be described.
- the injection amounts of the thrusters 91 (NW thruster), thruster 92 (NE thruster), thruster 93 (SW thruster), and thruster 94 (SE thruster) shown in FIG. 2 are respectively expressed as f NW , f NE , f SW , and f SE. .
- the north direction injection amount f N f NW + f NE
- f S f SW + f SE
- f E f NE + f SE
- f W f NW + f SW
- control amount of the distribution unit 5 controls the control amount of the average inclination angle by north injection quantity f N or south direction injection quantity f S. Since the east direction injection amount f E and west direction injection amount f W does not affect the average angle of inclination, is to define the north direction injection amount f N or south direction injection amount f S from only control the amount of the average inclination angle it can.
- the injection timing can be determined from the deviation angle ⁇ of the control amount ⁇ i of the average inclination angle vector.
- This north injection quantity f N or south direction injection quantity f S is able to control the average inclination angle be used either, in the case of both calculate the total value of the final injection amount is reduced Adopt one.
- the average eccentricity and mean average nadir longitude by north injection quantity f N or south direction injection quantity f S is affected by adding a correction amount of that amount, a new average eccentricity vector
- This correction amount is calculated by substituting the X B axis and Z B axis direction components of the north direction injection amount f N or the south direction injection amount f S into the eccentricity vector and the Gaussian planetary equation for the mean nadir longitude. Can do.
- eastward injection amount f E and west directions injection quantity f W is a total of two minutes is required. That is, given the eastward injection quantity f E or west injection quantity f W In certain longitude, obtaining a solution which gives an east injection quantity f E or west injection quantity f W at different longitudes.
- partitioned section 5 determines whether to adopt either north injection quantity f N or south direction injection amount f S as follows.
- Distributor 5 compares the total value of the East-West injection amount combined injection quantity when using the f N, a sum of the east and west injection amount combined injection quantity when using the f S, the sum The smaller value is adopted as the final injection.
- the lesser of the way the injection amount in one injection and two injections of east-west south of f N or f S, since longitude will be away when their implementation, these The effect that the timing of injection does not overlap is also obtained.
- the average tilt angle, the average eccentricity, and the average average directly below longitude in the series of control operations with one north-south and two east-west thrusters. can be controlled to a desired value.
- the average inclination angle can be affected.
- the average tilt angle is affected by the east and west thruster injections, it is not possible to easily determine the north and south thruster injection amounts.
- both or one of the two east-west thruster injections can be planned with only one thruster. If planned in this way, a part of the average inclination angle is controlled by the thruster injection in the east-west direction, so that there is an effect of keeping the total value of the injection amount low.
- FIG. 6 is a flowchart showing the operation of the distribution unit 5 according to the third embodiment.
- the distribution unit 5 first receives the control amount of the average eccentricity vector and the average inclination angle vector, the target value of the average average direct point longitude, and the like (step S31). Then, the north direction injection amount f N or the south direction injection amount f S (the north-south injection amount f N or f S ) is determined from the control amount of the average inclination angle vector (step S32).
- the distribution unit 5 reads out the control amount of the average eccentricity vector and the average inclination angle vector, the target value of the average average direct point longitude, and the like from the memory, and reads the north direction injection amount f N or the south direction injection amount f S (the north-south injection amount f N or f S ) is stored in memory.
- step S33 the control amount of the determined north-south injection quantity f N or new average eccentricity than f S and corrects the target value of the average mean nadir longitude. Then, determined from the target value of the average mean nadir longitude control of new average eccentricity, eastward injection amount f E and west directions injection quantity f W (east-west injection quantity f E, f W) (steps S34) .
- Distributor 5 reads the south injection quantity f N or f S from the memory, the control amount of the new average eccentricity, a target value of the average mean nadir longitude east injection amount f E and west directions injection quantity f W ( storing east-west injection quantity f E, the f W) in the memory.
- Distributor 5 in north-south injection quantity f N or f S, employing a lesser of the total injection quantity obtained by adding the east-west injection amount (step S35). Furthermore, based on the calculation of the thruster injection amount, in the two thruster injections in the east and west, instead of the simultaneous injection of two thrusters that exerts force in the east and west directions, some or all Is recalculated so as to be replaced by the injection of only one thruster (step S36). The calculated thruster injection amount is sent to the thruster controller 6 (step S37). The distribution unit 5 stores the calculated thruster injection amount in a memory.
- the average inclination angle is obtained by one injection in the north-south direction and two injections in the east-west direction by simple calculation on the premise of the injection combining the two thrusters. It is possible to control the average eccentricity and the average average direct point longitude to desirable values. Further, according to the configuration of the third embodiment, at least one of the two east and west thruster injections is made to be an injection of only one thruster based on a solution based on an injection that combines two thrusters. By obtaining a numerical search solution, it is possible to obtain an effect of controlling the average inclination angle, the average eccentricity, and the average average direct point longitude to desirable values and keeping the total value of the injection amount low.
- the orbit control device 9 of the embodiment can be applied not only to geostationary satellites.
- the orbit control device 9 can be applied to, for example, a quasi-zenith satellite.
- the quasi-zenith satellite looks like an eight-shaped orbit long from north to south when observed from one point on the ground, but the period and altitude are the same as those of geostationary satellites, and the orbital plane is tilted with respect to the equator plane. Therefore, if the above equation is appropriately coordinate-transformed, it can be applied as it is.
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Abstract
Description
図1はこの発明の実施の形態1に係る衛星の軌道制御装置の構成を示すブロック図である。軌道制御装置9は衛星7に搭載される。実施の形態では、衛星7として静止衛星を想定する。衛星7は、4つのスラスタ91、92、93、94とそれを制御する軌道制御装置9を備える。軌道制御装置9は、目標値設定部1、制御量計算部2、分配部5、軌道決定部8、およびスラスタ制御部6から構成される。制御量計算部2は、フィードフォワード制御量計算部3とフィードバック制御量計算部4を含む。軌道制御装置9は、衛星7の軌道を保持するためにスラスタ91、92、93、94それぞれの噴射タイミングと噴射量を決定し、決定した噴射タイミングと噴射量でスラスタ91、92、93、94に噴射させるよう制御する。
また、平均平均直下点経度の目標値ΛMrefの設定方法は、例えば衛星7を日本の上空に保持する場合にはΛMref=140degと設定することが挙げられる。
Δe=[e'x0T e'y0T]T (1)
Δi=[i'x0T i'y0T]T (2)
ここで、静止衛星の場合、衛星7の軌道運動の周期Tは、地球の自転周期に等しい。平均離心率ベクトルと平均傾斜角ベクトルが軌道1周期あたりにΔe、Δiだけ変化することを見越して、Δe、Δiを定数倍したものを平均離心率ベクトルと平均傾斜角ベクトルのフィードフォワード制御量に設定する。平均離心率ベクトルと平均傾斜角ベクトルそれぞれのフィードフォワード制御量δeFF、δiFFを、例えば以下の式(3)、(4)のように設定することができる。
δeFF=-(3/4)Δe (3)
δiFF=-(3/4)Δi (4)
以上が、フィードフォワード制御量計算部3の動作の説明である。続いて、フィードバック制御量計算部4の動作について説明する。
制御量計算部2が出力する平均離心率ベクトルと平均傾斜角ベクトルの制御量をそれぞれδe、δiと定義すると、δeとδiは以下の式(7)、(8)のように表される。
δe=δeFF+δeFB (7)
δi=δiFF+δiFB (8)
平均離心率ベクトルの制御は、衛星7の軌道面内方向の制御であり、平均傾斜角ベクトルの制御は、衛星7の軌道面外方向の制御である。
δi=[δicosβ δisinβ]T (9)
ただしδi>0を満たす。
λ1=β (10)
λ2=β+π (11)
A=naδi(-δexcosβ+δeysinβ)/(sinθcosφ) (12)
B=naδi/cosθ (13)
ここで、角度θはスラスタ91、92、93および94がYB軸と成す角度であり、角度φは、スラスタ91、92、93および94の各スラスタと衛星7の質量中心を結ぶ線分をXBZB平面に投影した線分が、XB軸と成す角度である(図2)。
ここで、上記変数AとBとは、速度の次元を有する。変数Bは、傾斜角ベクトルに関するガウス惑星方程式にSWスラスタとSEスラスタの噴射で生じるYB軸方向の力積の成分を代入することで得られる。また、上記変数Aは、離心率ベクトルに関するガウス惑星方程式にSWスラスタとSEスラスタの噴射で生じるXB軸方向の力積の成分を代入することで得られる。
分配部5は、AとBの大きさに応じて、fSとfNを以下の式(14)のように与える。
J=|(2αS-1)fS-(2αN-1)fN| (17)
式(17)で表される評価関数は、1回目の南北制御で発生するZB軸方向の力積と,2回目の南北制御で発生するZB軸方向の力積の差が小さくなることを要請している。
また、拘束条件を例えば以下の式(18)のように設定できる。
ΛMT=ΛMref-(1/2)ΔΛMtotal (18)
式(18)は、平均直下点経度を目標値ΛMrefに制御するための拘束条件である。式(18)において、ΔΛMtotalは、平均経度λ1における1回目の南北制御と平均経度λ2における2回目の南北制御と平均経度λrにおける平均離心率ベクトル制御によって生じる衛星7の平均平均直下点経度の変化量の総和であり、以下の式(19)のように表せる。
ΔΛMtotal=2tanθcosφδi+2|δe・ρβ| (19)
式(19)は、平均直下点経度に関するガウス惑星方程式に、平均経度λ1における1回目の南北制御、平均経度λ2における2回目の南北制御、および平均経度λrにおける平均離心率ベクトル制御によって生じるXB軸方向の力積を代入することで得られる。式(18)において、ΛMrefは衛星7の直下点経度の目標保持値であり、目標値設定部1にて設定される。また、式(18)において、ΛMTは1回目の南北制御を行ってから軌道1周期後の衛星7の平均平均直下点経度であり、以下の式(20)のように表せる。
ΛMT=ΛM0+Λ'M0T+(1/2)Λ"M0T2+ΔΛMtotal
-(3/a)sinθsinφ[(2αS-1)fS+(1/2)(2αN-1)fN]T
(20)
式(20)において、最初の3項は,1回目の南北制御を実行する直前の平均平均直下点経度の角速度と角加速度を時間積分することで得られる。また、最後の項は、1回目と2回目の南北制御で生じる平均平均直下点経度の角速度を時間積分することで得られる。ここで、Λ'M0、Λ'M0、Λ"M0はそれぞれ時刻t0における衛星7の平均平均直下点経度、平均平均直下点経度の角速度、および平均平均直下点経度の角加速度である。これらは軌道決定部8にて計算される。分配部5は、式(18)で与えられる平均直下点経度を目標値ΛMrefに制御するための拘束条件を満たしつつ、式(17)で与えられる評価関数Jが最小となるように、配分率αSとαNを決定する。
fNW1=0、fNE1=0、fSW1=αSfS、fSE1=(1-αS)fS (21)
fNW2=αNfN、fNE2=(1-αN)fN、fSW2=0、fSE2=0 (22)
λ1=β+π (23)
λ2=β+2π (24)
A=naδi(-δexcosβ+δeysinβ)/(sinθcosφ) (25)
B=naδi/cosθ (26)
角度θはスラスタ91、92、93および94がYB軸と成す角度であり、角度φはスラスタ91、92、93および94の各スラスタと衛星7の質量中心を結ぶ線分を向けXBZB平面に投影した線分が、XB軸と成す角度である(図2)。
分配部5は、AとBの大きさに応じて、fSとfNを以下の式(27)のように与える。
J=|(2αS-1)fS-(2αN-1)fN| (30)
また、拘束条件を例えば以下の式(31)のように設定できる。
ΛMT=ΛMref-(1/2)ΔΛMtotal (31)
ΔΛMtotal=2tanθcosφδi+2|δe・ρβ| (32)
ΛMT=ΛM0+Λ'M0T+(1/2)Λ"M0T2+ΔΛMtotal
-(3/a)sinθsinφ[(2αN-1)fN+(1/2)(2αS-1)fS]T
(33)
ここで、ΛM0、Λ'M0およびΛ"M0はそれぞれ時刻t0における衛星7の平均平均直下点経度、平均平均直下点経度の角速度、および平均平均直下点経度の角加速度であり、これらは軌道計算部8にて計算される。分配部5は、式(31)で与えられる拘束条件を満たしつつ、式(30)で与えられる評価関数Jが最小となるように、配分率αSとαNを決定する。
fNW1=αNfN、fNE1=(1-αN)fN、fSW1=0、fSE1=0 (34)
fNW2=0、fNE2=0、fSW2=αSfS、fSE2=(1-αS)fS (35)
実施の形態2では、軌道一周回においてスラスタ噴射が可能なタイミングを予め固定しておく。そして、その各タイミングについて制御量計算部で計算された平均離心率ベクトルおよび平均傾斜角ベクトルの制御量に応じて2回~4回のスラスタの噴射量および噴射の可否を決定する。実施の形態2の構成は実施の形態1と同様であるが、軌道制御装置9における分配部5の動作のみが異なる。その他の、目標値設定部1、制御量計算部2、スラスタ制御部6および軌道決定部8は実施の形態1と共通である。
λ1=λC (48)
λ2=λ1+π/2 (49)
λ3=λ1+π (50)
λ4=λ1+3π/2 (51)
λCは予め与える1回目のスラスタ噴射タイミングである。実施の形態2においてはこのλCを昇交点Ω付近の適当な値に固定する。例えばλC=80[deg]と設定する。そして1回目のスラスタ噴射から等間隔に位相をπ/2ずつ離してスラスタ噴射を行う。但しこのλCおよびλ1、λ2、λ3、λ4は上記の与え方以外の値を選ぶことも可能である。ここではスラスタの噴射回数を4回としているが実際に計算された制御量から、スラスタ噴射の回数が2回に抑えられる場合もありうる。以下に 軌道の保持に必要な制御力とスラスタの噴射量の計算方法について説明する。
|fhi|-|fh(i+2)|=anδe・ρei/(tanθcosφ) (52)
fhi-fh(i+2)=anδi・ρei (53)
θおよびφは、図2で与えられる角度である。
(1a) δei<0 のとき
fhi=sign(δii)|δei|、fh(i+2)=0 (54)
(1b) δei>0のとき
fhi=0、fh(i+2)=-sign(δii)|δei| (55)
(2) |δei|<|δii|のとき
(2a) δei+δii>0かつδei-δii<0 のとき
fhi=(1/2)(δei+δii)、fh(i+2)=(1/2)(δei-δii)
(56)
(2b) δei+δii<0かつδei-δii>0のとき
fhi=-(1/2)(δei+δii)、fh(i+2)=-(1/2)(δei-δii)
(57)
実施の形態3では、4本のスラスタのうち2本のスラスタを組み合わせて軌道1周回あたり1回南北制御を行い、2本のスラスタを組み合わせて軌道1周回あたり2回東西制御を行う。実施の形態3の構成は実施の形態1と同様であるが、軌道制御装置9における分配部5の動作のみが異なる。その他の、目標値設定部1、制御量計算部2、スラスタ制御部6、衛星7および軌道決定部8は実施の形態1と共通である。実施の形態1と異なる部分は分配部5のみであるので、分配部5について述べる。
fN=fNW+fNE、fS=fSW+fSE、
fE=fNE+fSE、fW=fNW+fSW
Claims (9)
- それぞれが衛星の質量中心から遠ざかる向きに互いに異なる方向に噴射方向を向けて前記衛星に配置された4本のスラスタを備える衛星の軌道制御装置であって、
前記衛星の平均軌道要素および平均軌道要素の時間変化率を決定する軌道決定部と、
前記平均軌道要素の目標値を設定する目標値設定部と、
前記平均軌道要素、前記平均軌道要素の時間変化率および前記目標値から、前記平均軌道要素の制御量を計算する制御量計算部と、
前記衛星の運動を軌道要素で表現し、スラスタ配置角度と複数回のスラスタ噴射量による軌道面外運動および軌道面内運動の連成を考慮した方程式を解き、主として軌道面外方向を制御するスラスタ噴射および主として軌道面内方向を制御するスラスタ噴射を複数回組み合わせることによって、前記制御量計算部で計算した前記平均軌道要素の制御量を実現させるための前記スラスタの噴射タイミングおよび噴射量を計算する分配部と、
前記分配部で計算された前記噴射タイミングおよび前記噴射量に従って、前記スラスタを制御するスラスタ制御部と、
を備える軌道制御装置。 - 前記制御量計算部は、
前記軌道決定部にて計算された前記平均軌道要素および前記目標値設定部にて設定された前記平均軌道要素の目標値をもとに、前記平均軌道要素のフィードバック制御量を計算するフィードバック制御量計算部と、
前記平均軌道要素の時間変化率をもとに、前記平均軌道要素のフィードフォワード制御量を計算するフィードフォワード制御量計算部と、
を含む請求項1に記載の軌道制御装置。 - 前記分配部は、同時に使用するスラスタ本数が2本以下になるように前記スラスタの前記噴射タイミングおよび前記噴射量を計算する請求項1に記載の軌道制御装置。
- 前記制御量計算部は、平均傾斜角ベクトルの制御量を計算し、
前記分配部は、前記平均傾斜角ベクトルの制御量の偏角を計算し、前記平均傾斜角ベクトルの制御量の偏角から南北制御の噴射タイミングを決定し、1回目の前記南北制御の噴射タイミングから軌道1/2周期後に2回目の南北制御を実施し、前記1回目の前記南北制御の噴射タイミングから軌道1/4周期後もしくは3/4周期後に平均離心率ベクトルの制御を行うように前記スラスタの前記噴射タイミングおよび前記噴射量を計算する、請求項1に記載の軌道制御装置。 - 前記分配部は、4本のうち2本の前記スラスタを組み合わせて軌道1周回あたり1回南北制御を行い、2本の前記スラスタを組み合わせて軌道1周回あたり2回東西制御を行うように前記スラスタの前記噴射タイミングおよび前記噴射量を計算する、請求項1に記載の軌道制御装置。
- 前記分配部は、前記分配部で計算した前記スラスタの前記噴射タイミングと前記噴射量を初期解として数値探索を実行し、2回の前記東西制御のスラスタ噴射のうち、少なくとも1回は前記スラスタを1本使用しないような前記スラスタの前記噴射タイミングおよび前記噴射量を計算する、請求項5に記載の軌道制御装置。
- 前記制御量計算部は、平均離心率ベクトルおよび平均傾斜角ベクトルの制御量を計算し、
前記分配部においては、軌道一周回においてスラスタ噴射が可能なタイミングを予め固定し、その各タイミングについて前記制御量計算部で計算された前記平均離心率ベクトルおよび前記平均傾斜角ベクトルの制御量に応じて、2回から4回の前記スラスタの前記噴射量および噴射の可否を決定する、請求項1に記載の軌道制御装置。 - それぞれが衛星の質量中心から遠ざかる向きに互いに異なる方向に噴射方向を向けて前記衛星に配置された4本のスラスタと、
請求項1から7のいずれか1項に記載の軌道制御装置と、
を備える衛星。 - それぞれが衛星の質量中心から遠ざかる向きに互いに異なる方向に噴射方向を向けて前記衛星に配置された4本のスラスタを備える衛星の軌道制御方法であって、
前記衛星の平均軌道要素および平均軌道要素の時間変化率を決定する軌道決定ステップと、
前記平均軌道要素の目標値を設定する目標値設定ステップと、
前記平均軌道要素、前記平均軌道要素の時間変化率および前記目標値から、前記平均軌道要素の制御量を計算する制御量計算ステップと、
前記衛星の運動を軌道要素で表現し、スラスタ配置角度と複数回のスラスタ噴射量による軌道面外運動および軌道面内運動の連成を考慮した方程式を解き、主として軌道面外方向を制御するスラスタ噴射および主として軌道面内方向を制御するスラスタ噴射を複数回組み合わせることによって、前記制御量計算ステップで計算した前記平均軌道要素の制御量を実現させるための前記スラスタの噴射タイミングおよび噴射量を計算する分配ステップと、
前記分配ステップで計算された前記噴射タイミングおよび前記噴射量に従って、前記スラスタを制御するスラスタ制御ステップと、
を備える軌道制御方法。
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