CN109407688B - Centroid motion decoupling method for vertical take-off and landing rocket online trajectory planning - Google Patents
Centroid motion decoupling method for vertical take-off and landing rocket online trajectory planning Download PDFInfo
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Abstract
The invention relates to a centroid motion decoupling method for vertical take-off and landing rocket online track planning, which reuses a rocket online trackThe decoupling description of the centroid motion of the trajectory planning avoids generating the shape T in the process of constructing the kinetic equationx 2+Ty 2+Tz 2＝T2The non-linear equation of (1) can also distinguish the vertical Y direction, the horizontal X direction and the Z direction of the vertical take-off and landing repeatedly-used rocket, and can also distinguish the acceleration a in the X, Y and Z directionsx,ay,azThe associated equality is described separately from the inequality constraint, and by the acceleration ax,ay,azThe generated equality and inequality constraint of the variable are separately described, cone constraint in online trajectory planning is avoided, and calculation efficiency is improved, so that the rationality of guidance and attitude control instructions in an online trajectory planning algorithm is ensured, and the trajectory planning of the rocket in the flight process is ensured not to exceed the capability range of the rocket.
Description
Technical Field
The invention relates to a centroid motion decoupling method for vertical take-off and landing rocket online trajectory planning, belonging to the technical field of vehicle trajectory online planning.
Background
The on-line trajectory planning technology is a technology for planning a motion trajectory of a carrier in real time in the flight process of the carrier to meet various equality and inequality constraint conditions. In flight control in the vertical take-off and landing repeated use carrier falling section, the introduction of the online trajectory planning technology can solve the problem of uncertainty of the initial falling position of the carrier. In the conventional track planning problem description, the dynamic equation constraint is generally only to select a thrust vector T as a state quantity in the establishing process, and then a component force vector T of the vector in the x, y and z directions under a coordinate systemx,Ty,TzDifferential equations are respectively constructed as the state quantities. However, this construction will result in a shape like Tx 2+Ty 2+Tz 2＝T2The non-linear equation of the method makes the calculation more complex, and the construction mode is not beneficial to the description of the differential equation of the acceleration of the subchannel in the X, Y and Z directions, and is also not beneficial to the description of the related equation and inequality constraint of the acceleration of the subchannel in the X, Y and Z directions.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a centroid motion decoupling method for online trajectory planning of a vertical take-off and landing rocket, which is used for decoupling the centroid motion of the vertical take-off and landing rocket online trajectory planning repeatedly and directly decoupling the accelerations a in the X, Y and Z directionsx,ay,azAs a state quantity, avoiding the generation of a shape such as T during the construction processx 2+Ty 2+Tz 2＝T2The non-linear equation of (1) can also distinguish the vertical Y direction, the horizontal X direction and the Z direction of the vertical take-off and landing repeatedly-used rocket, and can also distinguish the acceleration a in the X, Y and Z directionsx,ay,azThe associated equality is described separately from the inequality constraint, and by the acceleration ax,ay,azThe resulting equality of the variable is described separately from the inequality constraint.
The purpose of the invention is realized by the following technical scheme:
the method for decoupling the centroid motion of the online trajectory planning of the vertical take-off and landing rocket comprises the following steps:
(1) constructing a rocket X-direction online trajectory planning dynamics differential equation;
(2) constructing a rocket Y-direction online trajectory planning dynamics differential equation;
(3) constructing a rocket Z-direction online trajectory planning dynamics differential equation;
(4) constructing a relation between a control instruction and rocket acceleration;
(5) constructing an online trajectory planning dynamics equality constraint equation containing engine characteristics;
(6) acquiring a state quantity phi in real time, and solving a control quantity in real time through an on-line trajectory planning dynamics equality constraint equation;
(7) and calculating an engine thrust command and a program angle command in real time according to the solved control quantity.
Preferably, the differential equation of the online trajectory planning dynamics in the X direction is as follows:
wherein x is the lateral displacement in the rocket horizontal plane, vxFor transversely generated speeds in the horizontal plane, axIs the lateral acceleration in the horizontal plane.
Preferably, the rocket Y-direction online trajectory planning dynamics differential equation is as follows:
wherein y isIs the displacement of the rocket in the vertical direction, vyIs the velocity generated in the vertical direction, ayThe acceleration generated in the vertical direction.
Preferably, the rocket Z-direction online trajectory planning dynamics differential equation is as follows:
wherein the longitudinal displacement in the horizontal plane of the rocket is z, and the velocity v generated longitudinally in the horizontal planezThe acceleration generated longitudinally in the horizontal plane is az。
Preferably, the relationship between the control command and the rocket acceleration is as follows:
ux＝ax
uy＝ay
uz＝az
wherein u isxFor transverse control commands in the rocket's horizontal plane, uyFor rocket vertical direction control commands, uzIs a longitudinal control instruction in the horizontal plane of the rocket.
Preferably, the constraint equation of the online trajectory planning dynamics including the engine characteristics is as follows:
wherein the state quantity phi is [ x y z v ═x vy vz]', control quantity U ═ Ux uy uz]', a and B are coefficients before the state quantity and the controlled quantity, respectively.
Preferably, wherein
Preferably, the formula for calculating the engine thrust command in real time is as follows:
wherein M is rocket mass and g is gravitational acceleration.
Preferably, the formula for calculating the program angle command in real time is as follows:
γcx＝0
wherein
ψcx、γcxThe program angle commands of pitching, yawing and rolling directions are respectively, and g is the gravity acceleration.
Preferably, the step (5) further includes setting constraints for each of the state quantities and the control quantities.
Compared with the prior art, the invention has the following advantages:
(1) the invention avoids the generation of T-shaped motion in the process of constructing a kinetic equation by using the decoupling description of the centroid motion in the online trajectory planning of the rocket for vertical take-off and landing repeatedlyx 2+Ty 2+Tz 2＝T2The non-linear equation of (1) can also distinguish the vertical Y direction, the horizontal X direction and the Z direction of the vertical take-off and landing repeatedly-used rocket, and can also distinguish the acceleration a in the X, Y and Z directionsx,ay,azThe associated equality is described separately from the inequality constraint, and by the acceleration ax,ay,azSeparate description of the equality and inequality constraints of the variables produced, avoidingCone constraint in online trajectory planning is avoided, and calculation efficiency is improved.
(2) According to the invention, the engine thrust instructions generated after decoupling in the X, Y and Z directions can respectively describe the engine characteristics Y and the equivalent attitude control loop characteristics X, Z, and are respectively constrained, so that the guidance and attitude control precision in an online trajectory planning algorithm is ensured.
(3) According to the invention, the state variables after decoupling in the X, Y and Z directions respectively restrict the amplitude and the change rate of the control quantity in the X, Y and Z directions, and the position and the speed in the X, Y and Z directions, so that the trajectory planning of the rocket in the flying process can not exceed the capability range of the rocket.
Drawings
FIG. 1 is a schematic diagram of a mass center motion decoupling method for vertical take-off and landing rocket online trajectory planning.
Detailed Description
The technical scheme of the invention is that in the existing drop and reuse rocket trajectory planning problem description, a thrust vector T and a thrust vector T are constrained in the establishing process by a dynamics equationx,Ty,TzThree components as state quantity are changed into acceleration a in X, Y and Z directionsx,ay,azAs a state quantity, the vertical take-off and landing repeatedly uses the decoupling of the mass center motion of rocket online trajectory planning, and the technical scheme is shown in figure 1.
The method comprises the following concrete steps:
1) building rocket X-direction online trajectory planning dynamics differential equation
Pointing to a launching aiming direction according to the fact that an origin of a launching inertial coordinate system is at a launching point o and an ox axis is in a horizontal plane of the launching point; the oy axis is vertical to the horizontal plane of the emission point and points upwards, and the oz axis is vertical to the xoy plane, so that a right-hand coordinate system is formed.
Let x be the transverse displacement in the horizontal plane of the rocket, and the transversely generated velocity v in the horizontal planexIn the horizontal plane, the lateral acceleration is ax. Then the kinetic equation can be constructed as follows:
2) building rocket Y-direction online trajectory planning dynamics differential equation
Let the vertical displacement of the rocket be y and the vertical velocity vyAcceleration generated in the vertical direction is ay. Then the kinetic equation can be constructed as follows:
3) building rocket Z-direction online trajectory planning dynamics differential equation
Let the longitudinal displacement in the horizontal plane of the rocket be z, and the velocity v generated longitudinally in the horizontal planezThe acceleration generated longitudinally in the horizontal plane is az. Then the kinetic equation can be constructed as follows:
4) and constructing a relation between the control command and the acceleration, wherein the control command is an acceleration control command.
ux＝ax
uy＝ay
uz＝az
Wherein u isxFor transverse control commands in the rocket's horizontal plane, uyIs a fireArrow vertical direction control command, uzIs a longitudinal control instruction in the horizontal plane of the rocket.
5) Constructing an online trajectory planning dynamics equation constraint equation containing engine characteristics:
let the state quantity phi and the control quantity U be respectively
φ＝[x y z vx vy vz]′U＝[ux uy uz]′
An online trajectory planning dynamics differential equation including engine characteristics can be obtained as follows, where a and B are coefficients before the state quantity and the control quantity, respectively.
Constraints of each state quantity and each control quantity can be set, and therefore it is guaranteed that the trajectory planning of the rocket does not exceed the capability range of the rocket in the flying process.
6) Obtaining a state quantity phi in real time, and solving a control quantity U-U in real time through an online trajectory planning dynamics equality constraint equationx uy uz]′。
7) Program angle commands for calculating engine thrust command T and pitch, yaw, and roll directions
ψcx、γcx
γcx＝0
M is rocket mass, and g is gravity acceleration.
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
Claims (3)
1. A centroid motion decoupling method for vertical take-off and landing rocket online trajectory planning is characterized by comprising the following steps:
(1) constructing a rocket X-direction online trajectory planning dynamics differential equation;
(2) constructing a rocket Y-direction online trajectory planning dynamics differential equation;
(3) constructing a rocket Z-direction online trajectory planning dynamics differential equation;
(4) constructing a relation between a control instruction and rocket acceleration;
(5) constructing an online trajectory planning dynamics equality constraint equation containing engine characteristics;
(6) acquiring a state quantity phi in real time, and solving a control quantity in real time through an on-line trajectory planning dynamics equality constraint equation;
(7) calculating an engine thrust instruction and a program angle instruction in real time according to the solved control quantity;
the X-direction online trajectory planning dynamics differential equation is as follows:
wherein x is the lateral displacement in the rocket horizontal plane, vxFor transversely generated speeds in the horizontal plane, axIs the lateral acceleration in the horizontal plane.
The rocket Y-direction online trajectory planning dynamics differential equation is as follows:
wherein y is the displacement of the rocket in the vertical direction, vyIs the velocity generated in the vertical direction, ayAcceleration generated for the vertical direction;
the rocket Z-direction online trajectory planning dynamics differential equation is as follows:
wherein the longitudinal displacement in the horizontal plane of the rocket is z, and the velocity v generated longitudinally in the horizontal planezThe acceleration generated longitudinally in the horizontal plane is az；
The relationship between the control command and the rocket acceleration is as follows:
ux＝ax
uy＝ay
uz＝az
wherein u isxFor transverse control commands in the rocket's horizontal plane, uyFor rocket vertical direction control commands, uzIs a longitudinal control instruction in a rocket horizontal plane;
the on-line trajectory planning dynamics equation constraint equation containing the engine characteristics is as follows:
wherein the state quantity phi is [ x y z v ═x vy vz]', control quantity U ═ Ux uy uz]', A and B are coefficients before the state quantity and the control quantity, respectively;
the formula for calculating the thrust instruction of the engine in real time is as follows:
wherein M is rocket mass, and g is gravity acceleration;
the formula for calculating the program angle command in real time is as follows:
γcx＝0
wherein
ψcx、γcxThe program angle commands of pitching, yawing and rolling directions are respectively, and g is the gravity acceleration.
2. The method of decoupling centroid motion for online trajectory planning of a VTOL rocket of claim 1, wherein
3. The method for decoupling the centroid motion of the online trajectory planning of the vertical take-off and landing rocket according to claim 2, wherein the step (5) further comprises setting constraints of each state quantity and each control quantity.
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