Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a low-orbit optical remote sensing satellite multipoint imaging rapid maneuvering control method, which realizes that the satellite attitude is controlled to a desired value in the shortest time under the condition that the satellite reaction flywheel moment and the angular momentum thereof are limited, so that the optical load has the target of an imaging state.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a low-orbit optical remote sensing satellite multi-point imaging rapid maneuvering control method comprises the following steps:
the method comprises the following steps: performing kinematic dynamics modeling on the low-orbit optical remote sensing satellite: definition F
IRepresenting an inertial coordinate system, F
BRepresenting a satellite body coordinate system; satellite body coordinate system F
BRelative to an inertial frame F
IIs expressed as
Body coordinate system F
BRelative inertial frame F
IIs expressed as a unit quaternion
And satisfy the constraint condition
Wherein q is
0Is the scalar part of a quaternion Q, Q ═ Q
1,q
2,q
3) Is the vector portion of the quaternion Q,
representing an n-dimensional real vector space, the kinematic and kinetic equations of the satellite are:
in the formula:
the moment of inertia of the satellite is represented by a positive definite matrix; i is
3Is a 3 × 3 identity matrix; u is the control moment of the reaction flywheel;
is the total angular momentum of the reaction flywheel;
as an antisymmetric matrix, for arbitrary vectors
Satisfy s (x) y ═ x × y, where x represents a vector cross product;
the expected attitude of the satellite is defined as the attitude direction of the coordinate system of the satellite body relative to the inertial coordinate system, and quaternion is carried out through the expected attitude
Represents; q. q.s
d0Quaternion Q for the desired attitude
dScalar part of q
dQuaternion Q for the desired attitude
dThe vector portion of (1); the attitude tracking error is defined as the error quaternion:
in the formula:
representing quaternion multiplication, q
e0Is an error quaternion Q
eScalar part of q
eIs an error quaternion Q
eThe vector portion of (1); the angular velocity tracking error is:
ωe=ω-R(Qe)ωd
in the formula: omegadIs the desired angular velocity of the satellite; rotation matrix R (Q)e) The following relationships exist:
and satisfies the constraint condition | | | R (Q)e)||=1;
Step two: the satellite attitude planning method comprises the following steps: definition F
oShowing a trackCoordinate system, satellite body coordinate system F
BRelative to the orbital coordinate system F
oIs expressed as
Body coordinate system F
BRelative orbit coordinate system F
oUsing unit quaternion
Expressing and satisfying quaternion constraint conditions; the attitude of the satellite multi-point imaging task is that the satellite continuously performs side-sway maneuver; obtaining a satellite body coordinate system F through attitude planning
BRelative orbit coordinate system F
oDesired attitude quaternion
Desired angular velocity
And expected angular acceleration
The attitude planning is realized by an improved differentiator, and the specific form is as follows:
in the formula:
to the planned desired yaw angle;
to the planned desired yaw angular velocity; t is the controller step length;
for a planned desired yaw angular acceleration;
the calculation formula is as follows:
in the formula: r is the maximum maneuvering angular acceleration of the satellite side swing shaft;
is a prescribed maximum maneuvering angular velocity; h is a smoothing factor; a is an intermediate calculation variable, and the specific form is as follows:
in the formula: thetavFor the final desired roll angle,
obtaining the expected yaw angle according to the plan
Desired angular velocity
And desired angular acceleration
Calculating the quaternion of expected attitude of the satellite body coordinate system relative to the orbit coordinate system
Desired angular velocity
And expected angular acceleration
Comprises the following steps:
step three: transforming the attitude planning result from the orbital coordinate system to an inertial coordinate system:
calculating according to the second step to obtain the quaternion of the expected attitude of the satellite body coordinate system relative to the orbit coordinate system
Desired angular velocity
And expected angular acceleration
Quaternion Q of expected attitude of satellite body coordinate system relative to inertial coordinate system
dDesired angular velocity ω
dAnd desired angular acceleration a
dComprises the following steps:
in the formula: qoIIs the attitude quaternion of the orbit coordinate system relative to the inertia coordinate system;
step four: and establishing a satellite error kinematic kinetic equation by combining the attitude planning information:
according to the satellite attitude kinematics and the kinetic equation in the step one and by combining the attitude planning results in the step two and the step three, the error kinematics and the kinetic model of the satellite can be obtained as follows:
step five: the attitude control of the satellite is divided into an angle loop and an angular velocity loop, and control law design is carried out, wherein a controller of the satellite angle loop is as follows:
definition of
The controller of the satellite angular velocity loop is then:
the invention has the beneficial effects that: the quick maneuvering control method for the low-orbit optical remote sensing satellite multi-point imaging can realize quick and high-precision maneuvering control, greatly reduce maneuvering time of the satellite during orbit imaging, and improve the utilization rate of the optical remote sensing satellite. Compared with a classical control method, the method has the advantages that the method has the rapidity and the high-precision attitude stability of attitude maneuver, the satellite attitude can be converged to the planned attitude stably in the attitude maneuver process, and the control method is simple in structure, easy to implement and capable of being applied to engineering practice.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
A low-orbit optical remote sensing satellite multi-point imaging rapid maneuvering control method comprises the following steps:
the method comprises the following steps: performing kinematic dynamics modeling on the low-orbit optical remote sensing satellite: definition F
IRepresenting an inertial coordinate system, F
BRepresenting a satellite body coordinate system; satellite body coordinate system F
BRelative to an inertial frame F
IIs expressed as
Body coordinate system F
BRelative inertial frame F
IIs expressed as a unit quaternion
And satisfy the constraint condition
Wherein q is
0Is the scalar part of a quaternion Q, Q ═ Q
1,q
2,q
3) Is the vector portion of the quaternion Q,
representing an n-dimensional real vector space, the kinematic and kinetic equations of the satellite are:
in the formula:
the moment of inertia of the satellite is represented by a positive definite matrix; i is
3Is a 3 × 3 identity matrix; u is the control moment of the reaction flywheel;
is the total angular momentum of the reaction flywheel;
as an antisymmetric matrix, for arbitrary vectors
Satisfy s (x) y ═ x × y, where x represents a vector cross product;
the expected attitude of the satellite is defined as the attitude direction of the coordinate system of the satellite body relative to the inertial coordinate system, and quaternion is carried out through the expected attitude
Represents; q. q.s
d0Quaternion Q for the desired attitude
dScalar part of q
dQuaternion Q for the desired attitude
dThe vector portion of (1); attitude tracking error determinationMeaning as error quaternion:
in the formula:
representing quaternion multiplication, q
e0Is an error quaternion Q
eScalar part of q
eIs an error quaternion Q
eThe vector portion of (1); the angular velocity tracking error is:
ωe=ω-R(Qe)ωd
in the formula: omegadIs the desired angular velocity of the satellite; rotation matrix R (Q)e) The following relationships exist:
and satisfies the constraint condition | | | R (Q)e)||=1;
Step two: the satellite attitude planning method comprises the following steps:
the multi-point imaging task of the low-orbit optical remote sensing satellite requires the attitude to simultaneously meet the requirements of rapidity and high precision of a stable section in the maneuvering process. Compared with step control input, after the attitude planning is added, the maneuvering process can be controlled according to the maximum torque to ensure rapidity, and after maneuvering is finished, the attitude planning can enable the satellite attitude to be converged to a stable state quickly and stably.
Definition F
oRepresenting an orbital coordinate system, a satellite body coordinate system F
BRelative to the orbital coordinate system F
oIs expressed as
Body coordinate system F
BRelative orbit coordinate system F
oUsing unit quaternion
Expressing and satisfying quaternion constraint conditions; the attitude of the satellite multi-point imaging task is that the satellite continuously performs side-sway maneuver; the attitude planning is to obtain a satellite body coordinate system F through a corresponding planning algorithm
BRelative orbit coordinate system F
oDesired attitude quaternion
Desired angular velocity
And expected angular acceleration
The attitude planning is realized by an improved differentiator, and the specific form is as follows:
in the formula:
to the planned desired yaw angle;
to the planned desired yaw angular velocity; t is the controller step length;
for a planned desired yaw angular acceleration;
the calculation formula is as followsShown in the figure:
in the formula: r is the maximum maneuvering angular acceleration of the satellite side swing shaft;
is a prescribed maximum maneuvering angular velocity; h is a smoothing factor; a is an intermediate calculation variable, and the specific form is as follows:
in the formula: thetavFor the final desired roll angle,
obtaining the expected yaw angle according to the plan
Desired angular velocity
And desired angular acceleration
Calculating the quaternion of expected attitude of the satellite body coordinate system relative to the orbit coordinate system
Desired angular velocity
And expected angular acceleration
Comprises the following steps:
step three: transforming the attitude planning result from the orbital coordinate system to an inertial coordinate system:
calculating according to the second step to obtain the quaternion of the expected attitude of the satellite body coordinate system relative to the orbit coordinate system
Desired angular velocity
And expected angular acceleration
Quaternion Q of expected attitude of satellite body coordinate system relative to inertial coordinate system
dDesired angular velocity ω
dAnd desired angular acceleration a
dComprises the following steps:
in the formula: qoIIs the attitude quaternion of the orbit coordinate system relative to the inertia coordinate system;
step four: and establishing a satellite error kinematic kinetic equation by combining the attitude planning information:
according to the satellite attitude kinematics and the kinetic equation in the step one and by combining the attitude planning results in the step two and the step three, the error kinematics and the kinetic model of the satellite can be obtained as follows:
step five: the attitude of the satellite is divided into an inner loop and an outer loop, a controller is established, and the multi-point imaging rapid maneuvering control of the low-orbit optical remote sensing satellite is realized:
the controller is designed based on the idea of nonlinear feedback and model reference control. According to the satellite error kinematics and the kinetic equation, the kinematics equation and the kinetic equation have different time scales, so that the attitude control of the satellite is divided into an angle loop and an angular velocity loop to carry out controller design, the block diagram of the control system is shown in figure 1, the sign in the figure represents the sign polarity of a signal,
representing a signal summer. In the figure, a controller structure combining inner and outer loop control and nonlinear feedback control in the patent is described in a structural block diagram form, and the specific flow is as follows: after the expected attitude is subjected to attitude planning and coordinate system transformation, the generated expected attitude quaternion is used for an angle loop controller, and the expected angular velocity and the expected angular acceleration are used for a nonlinear feedback controller. The output of the angular loop controller is the virtual expected angular velocity of the angular velocity loop
The sum of the control quantities of the final angular velocity loop controller and the nonlinear feedback controller u is inputThe control moment is generated by the flywheel to act on the satellite, and the attitude dynamics and the attitude kinematics in the graph respectively feed back the real-time angular velocity and the attitude quaternion of the satellite.
The controller of the satellite angle loop is as follows:
definition of
The control quantity generated by the satellite angular velocity loop controller in combination with the nonlinear feedback controller is:
and when the satellite multi-point imaging task mode is adopted, different imaging points correspond to different side swing angles. The present embodiment performs attitude planning by respectively swinging to 15 °, -10 °, and 0 °, and ensures that each imaging task has an imaging time greater than 15 s. Table 1 shows the parameters relevant to the examples.
TABLE 1
The attitude planning curves of the yaw angle, the yaw angular velocity and the yaw angular acceleration are shown in fig. 2, and the information of the yaw angle, the yaw angular velocity and the yaw angular acceleration planned for realizing the multipoint imaging fast maneuver control is given in the diagram. The corresponding maneuvering and imaging effects of the satellite are schematically shown in fig. 3, which shows a trajectory diagram of an optical axis of an optical remote sensing satellite camera using rapid maneuvering control for three different shooting points by the satellite.
The attitude controller of the patent can guarantee stable and accurate attitude tracking control according to the attitude planning result of multi-point imaging. The attitude control tracking convergence trajectory chart is shown in fig. 4, and is a satellite yaw angle tracking convergence trajectory chart and a satellite yaw angular velocity tracking convergence trajectory chart, respectively. It can be observed from the figure that the actual roll angle curve and the actual angular velocity curve are basically completely overlapped with the planned roll angle and the planned angular velocity curve, thereby further demonstrating that the controller designed by the patent realizes good dynamic tracking on the planned roll angle and the planned roll angular velocity. The attitude control error convergence trajectory graph is shown in fig. 5, which is a satellite yaw angle error convergence trajectory graph and a satellite yaw angular velocity error convergence trajectory graph, and shows that the overall control error is small and the convergence rate is high in the maneuvering process of the satellite in multipoint imaging.