CN114476056A - Control framework for autonomous splicing of distributed multi-dwelling spherical unmanned system - Google Patents

Control framework for autonomous splicing of distributed multi-dwelling spherical unmanned system Download PDF

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CN114476056A
CN114476056A CN202210040388.2A CN202210040388A CN114476056A CN 114476056 A CN114476056 A CN 114476056A CN 202210040388 A CN202210040388 A CN 202210040388A CN 114476056 A CN114476056 A CN 114476056A
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unmanned aerial
aerial vehicle
attitude
splicing
controller
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CN114476056B (en
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蔡志浩
杨杰松
赵江
王英勋
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Beihang University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C37/00—Convertible aircraft
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C39/00—Aircraft not otherwise provided for
    • B64C39/02—Aircraft not otherwise provided for characterised by special use
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64U—UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR
    • B64U10/00—Type of UAV
    • B64U10/10—Rotorcrafts
    • B64U10/13—Flying platforms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64U—UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR
    • B64U70/00—Launching, take-off or landing arrangements
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course or altitude of land, water, air, or space vehicles, e.g. automatic pilot
    • G05D1/08—Control of attitude, i.e. control of roll, pitch, or yaw
    • G05D1/0808—Control of attitude, i.e. control of roll, pitch, or yaw specially adapted for aircraft
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64U—UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR
    • B64U2101/00—UAVs specially adapted for particular uses or applications

Abstract

The invention discloses a control framework for autonomous splicing of a distributed multi-dwelling spherical unmanned system, which comprises a plurality of unmanned aerial vehicles, wherein the unmanned aerial vehicles are spliced to form the spherical unmanned system, and a flight mode, an attitude control mode and a sphere rolling mode are realized at different stages of splicing; the control framework comprises a position controller based on nonlinear incremental dynamic inversion, an attitude controller based on nonlinear geometric control theory and a hemispherical unmanned system rolling controller; the position controller is used for realizing accurate butt joint of the splicing mechanism of the unmanned aerial vehicle in an external visual positioning environment; the attitude controller is used for controlling the attitude of the unmanned aerial vehicle to reach 90 degrees and turning the unmanned aerial vehicle into a hemisphere from a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispheroids to roll towards the direction of incomplete splicing, so that the whole sphere is spliced. The control framework simplifies the connecting mechanism of each subsystem unmanned aerial vehicle, and meanwhile, the autonomous splicing control of multiple unmanned aerial vehicles is realized.

Description

Control framework for autonomous splicing of distributed multi-dwelling spherical unmanned system
Technical Field
The invention relates to the technical field of control over a rotor unmanned aerial vehicle and a spherical robot, in particular to a multi-machine cooperative control and large-angle attitude control framework of an unmanned aerial vehicle. And more particularly, to coordinated control of multiple machines in multiple modalities.
Background
A distributed multi-dwelling spherical unmanned system is an unmanned system with two structural modes of an air flight mode and a ground rolling mode. The unmanned aerial vehicle comprises a plurality of independent subsystem unmanned aerial vehicles, wherein each unmanned aerial vehicle is of a four-rotor configuration and has the capability of independently executing tasks in the air; meanwhile, the electromagnetic adsorption devices are arranged among each other and can be mutually connected into a spherical shape, so that the system can represent the motion characteristic of a sphere on the ground. The distributed combined structure has extremely wide application prospect in military affairs and civilian life. In recent years, a large number of multi-dwelling unmanned innovative mobile platforms are researched all over the world, and some platforms adopt a fixed wing type structure, but an aircraft adopting the fixed wing type structure can take off only by long running; some multi-purpose mobile platforms flying by using the principle of the gyroplane have the advantages of vertical take-off and landing and the like, but the exposed propellers of the multi-purpose mobile platforms can threaten surrounding objects greatly, and the platforms have the problems of single configuration, isolated work and large functional limitation in safety or working space; on one hand, research on the spherical robot rarely considers the expansion of the multi-dwelling property of the spherical robot, on the other hand, a scheme of driving by gravity moment is adopted, the scheme couples three degrees of freedom of the sphere together, and the problems of single configuration and large functional limitation exist.
For the distributed multi-dwelling spherical unmanned system, the process that the multi-subsystem unmanned aerial vehicle is converted from flight mode splicing to ground sphere mode is complex, and the design of a connecting mechanism between the subsystem unmanned aerial vehicles, the design of a splicing flow and the design of a specific control law in the splicing process are involved. The subsystem unmanned aerial vehicle adopts the configuration of four rotors, and its basic controller design method has been more mature. However, the control method of the quadrotor unmanned aerial vehicle based on the traditional theory still has the defects for the distributed multi-dwelling spherical unmanned system, which are mainly reflected in the following aspects: (1) when a flight control system is designed based on a traditional control strategy, an euler angle is usually adopted to represent the posture of a rotor unmanned aerial vehicle, and the phenomenon that a universal joint is locked exists under the condition of a large posture angle, for example, when a pitch angle is 90 degrees, the posture of the unmanned aerial vehicle can be represented by a plurality of euler angles in a combined mode, and the feedback value of a controller is caused to deviate. (2) In the traditional multi-machine cooperation and unmanned aerial vehicle formation control, all unmanned aerial vehicles are not physically connected, and collision is prevented, so that the requirement on the position precision is low. The spherical mode corresponding to the control method needs a plurality of rotor subsystems to be spliced and combined, and the requirement on position control of the subsystems is high.
Disclosure of Invention
In order to solve the problem of large functional limitation of the multi-dwelling unmanned system, the invention adopts the concept of modular assembly and provides a distributed multi-dwelling spherical unmanned system. The aircraft has a better configuration under different ground and air environments, and consists of a plurality of independent rotor wing driving flight unit modules, and each rotor wing driving flight unit module has the capability of independently executing tasks in the air; meanwhile, the electromagnetic adsorption devices are arranged among each other and can be mutually connected into a spherical shape, so that the system can represent the motion characteristic of a sphere on the ground. The research on the multi-dwelling spherical system is few at home and abroad at present, and the process of splicing the multi-subsystem unmanned aerial vehicle into a sphere is more critical for the combined spherical unmanned aerial vehicle system. In view of this, the invention provides a splicing control architecture for a distributed multi-dwelling spherical unmanned system in a modal conversion process, and the specific technical scheme is as follows:
a control framework for autonomous splicing of a distributed multi-dwelling spherical unmanned system comprises a plurality of unmanned aerial vehicles which are spliced to form the spherical unmanned system, and a flight mode, an attitude control mode and a sphere rolling mode are realized at different stages of splicing; the control framework comprises a position controller based on nonlinear incremental dynamic inversion, an attitude controller based on nonlinear geometric control theory and a hemispherical unmanned system rolling controller;
the position controller is used for realizing accurate butt joint of the splicing mechanism of the unmanned aerial vehicle in an external visual positioning environment; the attitude controller is used for controlling the attitude of the unmanned aerial vehicle to reach 90 degrees and turning the unmanned aerial vehicle into a hemisphere from a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispheroids to roll towards the direction of incomplete splicing, so that the whole sphere is spliced.
In particular, the flight mode enables multi-level formation flight and air docking of the drones; the attitude control mode realizes that the unmanned aerial vehicles are spliced into hemispheres; the rolling mode realizes rolling control of a ground sphere mode and the splicing of hemispheres into a complete sphere.
Particularly, the unmanned aerial vehicle realizes splicing through an electromagnetic connecting mechanism, the electromagnetic connecting mechanism is positioned at the middle points of four sides of the unmanned aerial vehicle, electromagnets are installed on the electromagnetic connecting mechanism, and attraction and separation of the electromagnets are realized by controlling on-off of current; the electromagnetic connecting mechanism is connected with the unmanned aerial vehicle shell through a movable hinge mechanism, the hinge mechanism comprises a rotating shaft, and the electromagnetic connecting mechanism rotates around the rotating shaft to form two states of ejection and recovery; and a coil spring is arranged at the rotating shaft, so that the electromagnetic connecting mechanism is in a popup state under the state of not receiving external force, and the suction surface of the electromagnet is parallel to the plumb bob surface when the electromagnetic connecting mechanism pops.
Particularly, the electro-magnet is the cuboid, realizes spacing on unmanned aerial vehicle's roll direction.
Particularly, six unmanned aerial vehicles are spliced, the six unmanned aerial vehicles hover to form a topological structure, the position controller controls the six unmanned aerial vehicles to gather towards the center, the electromagnetic connecting mechanisms in the popping state attract each other to realize butt joint when the distance is short, and the six unmanned aerial vehicles are located in the same plane and cooperatively control to keep the posture and realize landing; six unmanned aerial vehicles are connected in a cross manner, the four transverse unmanned aerial vehicles are numbered from left to right in sequence as 6, 5, 1 and 3, the No. 2 unmanned aerial vehicle is connected above the No. 1 unmanned aerial vehicle, and the No. 4 unmanned aerial vehicle is connected below the No. 1 unmanned aerial vehicle; 2. the No. 3 and No. 4 unmanned aerial vehicles enter an attitude control mode, an electromagnetic connecting mechanism is used as a support, 90-degree overturning is realized through an attitude controller, the No. 1, No. 2, No. 3 and No. 4 unmanned aerial vehicles are combined into a hemisphere, and the rolling control mode is entered; 1. the No. 2 unmanned aerial vehicle provides pitching moment to enable the hemispheroid to roll towards the No. 5 and No. 6 unmanned aerial vehicles, and the No. 3 and No. 4 unmanned aerial vehicles cooperatively provide tension to keep the hemispheroid balanced in the rolling direction; in the rolling process of the hemispheroid, the electromagnetic connecting mechanisms on the two sides of the No. 5 and No. 6 unmanned aerial vehicles are connected with the electromagnets of the No. 2, No. 3 and No. 4 unmanned aerial vehicles, so that the spherical combination is realized.
Specifically, the position controller based on the nonlinear incremental dynamic inverse is specifically:
the translational motion equation and the kinetic equation of the unmanned aerial vehicle are as follows:
Figure BDA0003469958960000021
Figure BDA0003469958960000022
wherein x is the drone position coordinates; v is the unmanned aerial vehicle velocity vector; m is the unmanned aerial vehicle mass; e.g. of the type3Is a unit vector, e3＝[0,0,1](ii) a g is the acceleration of gravity; r ═ bx by bz]The element SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; tau is the ratio of the tension to the mass of the rotor of the drone; f. ofextRepresenting external disturbances to the drone, including additional aerodynamic forces due to the incoming flow and unmodeled dynamic characteristics of the actuators themselves; the position controller based on the nonlinear incremental dynamic inverse comprises a position velocity ring and a linear acceleration ring, wherein the linear acceleration ring is based on a kinetic equation, an INDI controller is adopted, external interference is estimated in real time through a sensor, and compensation is carried out in the controller; the disturbance term is presented for equation (2) and the acceleration and tension terms are represented by the sensor measurements:
fext＝m(af-τfbz-ge3) (3)
wherein, afAcceleration measurements taken by the sensor; bzIs a unit projection vector of the z axis of the unmanned aerial vehicle system under the ground system, namely R ═ bx,by,bz]The third column of (c); tau isfThe influence that formula (3) is substituted into formula (2) and can be got rid of the disturbance and bring is the ratio of the pulling force of the unmanned aerial vehicle rotor that obtains by the sensor and the quality, obtains the unmanned aerial vehicle acceleration a's that does not have external force disturbance term expression:
Figure BDA0003469958960000031
the input of the linear acceleration loop is a desired acceleration acmdThe output is an attitude angle command RcmdCombined tensile force FcmdInstructions; and (5) inverting the attitude angle and the resultant tension instruction by the formula (4) to obtain a control law of the linear acceleration ring:
τcmdRcmde3＝acmd-af+τfbz (5)
wherein τ iscmdIs a scalar quantity, Rcmde3Is a vector; calculating the mode of the left side of the equation to obtain a resultant tension instruction, and unitizing the resultant tension instruction to obtain a third column of the expected rotation matrix; and then, through a yaw angle instruction, solving vector cross multiplication to obtain a complete rotation matrix instruction:
Fcmd＝-m||τcmdRcmde3||2 (6)
Figure BDA0003469958960000032
according to bzcmdAnd determination of yaw angle psi of the drone bxcmdAnd bycmdAnd further determining the command value R of the rotation matrixcmd：
Figure BDA0003469958960000033
Figure BDA0003469958960000034
Rcmd＝[bxcmd bycmd bzcmd] (10)
The position and speed ring does not relate to an external force disturbance term in a kinematic equation, a PD controller is adopted, and the control law is as follows:
Figure BDA0003469958960000035
wherein, Kx,Kv∈R3×3A gain matrix that is a position velocity loop; the output of the position velocity loop is a linear acceleration command.
Specifically, the attitude controller based on the nonlinear geometric control theory is specifically:
the rotational motion equation and the kinetic equation of the unmanned aerial vehicle are as follows:
Figure BDA0003469958960000041
Figure BDA0003469958960000042
wherein ^ is defined by x, y ∈ R3,
Figure BDA0003469958960000043
Obtaining; omega is the angular velocity of the unmanned aerial vehicle, J is the moment of inertia of the body; m is the sum moment received by the unmanned aerial vehicle; the input to the attitude controller is RcmdObtained by a position controller; the error of the inner loop is expressed as:
Figure BDA0003469958960000044
wherein e isRIs the error of the rotation matrix; e.g. of the typeΩIs the error in angular velocity; omegacmdIs an angular velocity command; v is the inverse transformation of the V; according to the rotational motion equation (13), the control law of the inner ring is designed as follows:
Figure BDA0003469958960000045
wherein, KR,KΩ∈R3×3A gain matrix that is a loop of angles and angular velocities; in the process of executing 90-degree overturning splicing in the attitude control mode, the unmanned aerial vehicle takes the electromagnetic connecting mechanism as a hingeRealize the upset, so gravity can produce the moment of resistance, the formula of control distribution is as follows:
Figure BDA0003469958960000046
wherein phi is the angle of rotation around the hinge connection mechanism; f1The tension generated by the two rotors close to the connecting mechanism; f2Tension generated for two rotors that are far from the connection mechanism; a is F1The horizontal distance of the two rotors to the connection mechanism; b is F2Horizontal distance of the two rotors to the connection mechanism.
Specifically, the hemispherical unmanned system rolling controller specifically comprises:
1. the No. 2, No. 3 and No. 4 unmanned aerial vehicles are combined into a hemisphere and roll forward in the directions of the No. 5 and No. 6 unmanned aerial vehicles; the No. 5 and No. 6 unmanned aerial vehicles adopt attitude controllers when splicing is not finished, and attitude angle instructions are all 0 degrees, so that the unmanned aerial vehicles are kept horizontal in the splicing process; 2. the No. 4 unmanned aerial vehicle adopts an attitude controller, uses a rotation matrix to represent the attitude, controls the Z-axis direction of the body to be parallel to the ground, and prevents the hemispherical body part from inclining to the side surface during rolling forward; 1. the No. 3 unmanned aerial vehicle adopts an angular velocity controller, and the two unmanned aerial vehicles jointly provide forward pitching moment to drive the whole hemispheroid to roll forward to realize splicing; 2. no. 4 unmanned aerial vehicle switches to angular velocity controller after accomplishing the concatenation, provides the rolling moment of spheroid jointly.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a flow scheme for splicing a plurality of sub-system unmanned aerial vehicles into a sphere combined unmanned aerial system, and adopts an electromagnetic hinge connecting mechanism, so that the sub-unmanned aerial vehicles do not need to be spliced in place in one step to form a sphere, but are firstly butted in a plane, and then the sphere is spliced into a sphere in a three-dimensional mode. The difficulty in control is simplified by designing a connecting mechanism, and engineering realization is easy.
2. Compared with the traditional controller for representing the attitude by the Euler angle, the attitude controller has no strange problem, so that the aircraft can reach a large attitude. Meanwhile, simulation results show that the tracking precision is superior to that of a PID controller when the large-angle attitude command is tracked.
Drawings
FIG. 1 is a schematic view of a hinged connection;
wherein 1 is the shell of the subsystem unmanned aerial vehicle; 2 is an electromagnet arranged on the base of the electromagnetic connecting mechanism; 3 is a rotatable electromagnetic coupling mechanism; (a) is a state schematic diagram when the electromagnetic connecting mechanism is popped up; (b) is a state schematic diagram when the electromagnetic connecting mechanism is retracted;
FIG. 2 is a schematic view of a two shelf system drone dock;
FIG. 3 is a schematic diagram of a spherical gang robot splice;
FIG. 4 is a flowchart of a spherical composite robot modality conversion;
FIG. 5 is a graph of a 90 response tracking in attitude control mode;
fig. 6 is a schematic of drone dimensional parameters and drone motor tension.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention provides a control framework for autonomous splicing of a distributed multi-dwelling spherical unmanned system, and a controller can be divided into a flight mode, an attitude control mode and a sphere rolling mode according to different stages of splicing. The flight mode is mainly responsible for the operations of multi-stage formation flight and air butt joint of the subsystem unmanned aerial vehicle; the attitude control mode is mainly used for splicing hemispheres; the rolling mode is mainly used for rolling control of a ground sphere mode and a stage of splicing hemispheroids into a complete sphere; the specific design steps are as follows:
the design of the electromagnetic connecting mechanism and the splicing flow between the unmanned aerial vehicles of the rotor subsystems is achieved in the first step. Single rotor subsystem unmanned aerial vehicle adopts the configuration of four rotors, because the platform characteristic of four rotors, the aerodynamic force that the rotor produced is always parallel with the z axle of organism. In the spherical mode in ground, make up into the spheroidal six sub-systems's of group z axle by the directional spheroid surface in spheroid center, if need each sub-system directly splice into the spheroid when flight in the air, then only be located the unmanned aerial vehicle of spheroid bottom for less gesture, five unmanned aerial vehicles at spheroid all around and top need be close and realize the connection with very big gesture angle, are difficult to realize in control. Therefore, the movable electromagnetic connecting mechanism is designed, the rotor subsystems are not required to be directly spliced into a sphere in flight, but are sequentially connected in a horizontal plane to form a cube which is unfolded into a planar layout and then landed on the ground. On the ground, the splicing of the spheres is realized through the attitude control of the rotatable connecting mechanism and the subsystem. The geometric topological structure of the six-shelf system unmanned aerial vehicle in the plane during docking is not limited to the structure at the upper left corner in fig. 3, and various planar graphs unfolded into the plane in a right cube can be used as the topological structure for air docking. The electromagnetic connecting mechanism is connected with the unmanned aerial vehicle shell through the hinge mechanism, a torsion spring is arranged at the rotating shaft of the hinge mechanism, and the electromagnetic connecting mechanism is in a popup state under the state of not being subjected to external force. The electromagnet adopted by the electromagnetic connecting mechanism is not limited to be cylindrical, and can also be cuboid. Compare in columniform electro-magnet, cuboid shape electro-magnet can be spacing on unmanned aerial vehicle's roll-over direction, and the in-process unmanned aerial vehicle that carries out 90 upsets can not surpass the side and empty, but the electro-magnet that general accord with the size is cylindricly, is suitable for the cuboid electro-magnet of this size hinge base and needs the customization, and the price is more expensive.
And secondly, designing a position controller based on the nonlinear incremental dynamic inverse. Because the proposed splicing method requires six rotor subsystem drones to be docked in the air, the invention designs an accurate position controller based on nonlinear incremental dynamic inversion (INDI). Under the environment of external vision positioning, millimeter-scale control precision can be realized, and accurate butt joint of the splicing mechanism is ensured.
And thirdly, designing the attitude controller based on the nonlinear geometric control theory. The method for representing the attitude by the Euler angle is generally adopted in the traditional attitude control of the unmanned aerial vehicle, the method can decouple three channels representing the attitude, and controllers are respectively designed, so that the method has the advantages of intuition and easiness in understanding. But at large angles, the problem of singularity arises. The invention uses the rotation matrix to represent the posture of the unmanned aerial vehicle, can control the posture of the unmanned aerial vehicle to reach 90 degrees, and realizes the control of turning the plane into a hemisphere.
And fourthly, designing a rolling controller of the hemispherical unmanned system. The part spliced into the hemisphere adopts a controller with a rolling sphere to roll towards the direction of incomplete splicing, so that the whole sphere is spliced.
Wherein, first step, the specific form of the electromagnetism coupling mechanism between each rotor subsystem unmanned aerial vehicle is:
adopt mobilizable the hinge mechanism to connect electromagnetic connection mechanism and unmanned aerial vehicle shell, wherein electromagnetic connection mechanism arranges in subsystem unmanned aerial vehicle's four mid points. The electromagnet is arranged on the electromagnetic connecting mechanism, and the operation of attraction and separation of the electromagnet can be realized by controlling the on-off of current. The hinge mechanism comprises a rotating shaft, and the electromagnetic connecting mechanism can rotate 45 degrees around the rotating shaft to form two states of ejection and retraction. The suction surface of the electromagnet is parallel to the plumb bob surface when the electromagnetic connecting mechanism is popped up by taking the horizontal placement of the rotor subsystem as a reference. A coil spring is arranged at the rotating shaft of the hinge mechanism, so that the electromagnetic connecting mechanism is in a popup state under the state of not being subjected to external force.
The specific form of the splicing process is as follows: six unmanned aerial vehicles in formation flight hover and form specific topological structure, and the unmanned aerial vehicle of state of hovering this moment is controlled by position controller to slowly gather to the center, and when being close apart from, the electromagnetic connection mechanism that is in the pop-up state can attract each other and realize the butt joint. All unmanned aerial vehicles are located same plane this moment, and cooperative control keeps the gesture and realizes descending. The subsystem drones automatically assign numbers according to the positions of the drones in the formation after the air docking, as shown in fig. 2. After the butt joint is completed, the unmanned aerial vehicles numbered 2, 3 and 4 enter an attitude control mode, an electromagnetic connecting mechanism is used as a support, and 90-degree overturning is realized through an attitude controller. At this time, 1, 2, 3 and 4 are combined into a hemisphere, and a rolling control mode is entered. 1. The unmanned aerial vehicle of 2 numbers provides pitching moment and makes the hemispheroid roll towards 5, 6 unmanned aerial vehicle. 3. No. 4 unmanned aerial vehicle provides the pulling force in coordination and keeps the hemisphere at the ascending equilibrium of roll direction. In the rolling process of the hemispheroid, the electromagnetic connecting mechanisms on the two sides of the No. 5 and No. 6 unmanned aerial vehicles are connected with the electromagnetic connecting mechanisms on the No. 2, No. 3 and No. 4 unmanned aerial vehicles, so that the spherical bodies are spliced.
Secondly, the specific method for designing the position controller based on the nonlinear incremental dynamic inverse comprises the following steps:
the translational motion equation and the kinetic equation of the unmanned aerial vehicle subsystem are as follows:
Figure BDA0003469958960000061
Figure BDA0003469958960000062
wherein x is the drone position coordinates; v is the unmanned aerial vehicle velocity vector; m is the unmanned aerial vehicle mass; e.g. of the type3Is a unit vector, e3＝[0,0,1](ii) a g is the acceleration of gravity; r ═ bx by bz]The element SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; tau is the ratio of the tension to the mass of the rotor of the drone; f. ofextRepresenting the external disturbances to which the drone is subjected, including the additional aerodynamic forces due to the incoming flow and the unmodeled dynamic characteristics of the actuators themselves. The position controller based on the nonlinear incremental dynamic inverse mainly comprises a position velocity ring and a linear acceleration ring, wherein the linear acceleration ring is based on a kinetic equation, and in order to reduce the influence caused by external interference, the INDI controller is adopted in the invention, the external interference is estimated in real time through a sensor, and compensation is carried out in the controller. The disturbance term is presented for equation (2) and the acceleration and tension terms are represented by the sensor measurements:
fext＝m(af-τfbz-ge3) (3)
wherein, afAcceleration measurements taken by the sensor; bzIs a unit projection vector of the z axis of the unmanned aerial vehicle system under the ground system, namely R ═ bx,by,bz]The third column of (d); tau isfIs the ratio of the pulling force and the mass of the unmanned aerial vehicle rotor obtained by the sensor. Will be provided withThe estimated disturbance is substituted into formula (2) to eliminate the influence caused by the disturbance, and an expression of the acceleration a of the unmanned aerial vehicle without an external disturbance term is obtained:
Figure BDA0003469958960000071
the input of the linear acceleration loop is a desired acceleration acmdThe output is an attitude angle command RcmdCombined tensile force FcmdAnd (5) instructions. And (3) inverting the attitude angle and the resultant tension instruction by the above formula to obtain a control law of the linear acceleration ring:
τcmdRcmde3＝acmd-af+τfbz (5)
wherein tau iscmdIs a scalar quantity, Rcmde3Is a vector. Equating the left side to obtain a resultant pull command, unitizing it to obtain the third column b of the desired rotation matrixzcmd. And then, according to the yaw angle instruction, solving vector cross multiplication to obtain a complete rotation matrix instruction.
Fcmd＝-m||τcmdRcmde3||2 (6)
Figure BDA0003469958960000072
According to bzcmdAnd the yaw angle psi of the drone can be uniquely determinedxcmdAnd bycmdAnd then determines the command value of the rotation matrix. The specific process is as follows: first, a vector b is defined according to a yaw anglem＝[cosψ sinψ 0]TThe rotation matrix is constructed using this vector as the intermediate vector. Then by the and vector bzcmdB of the machine system can be obtained by cross multiplicationycmd：
Figure BDA0003469958960000073
Finally b will be obtainedycmdAnd bzcmdB of machine system can be obtained by cross multiplicationxcmdAnd then a complete rotation matrix command is obtained.
Figure BDA0003469958960000074
Rcmd＝[bxcmd bycmd bzcmd] (10)
The position and speed ring does not relate to an external force disturbance term in a kinematic equation, so a traditional PD controller can be adopted, and the control law is as follows:
Figure BDA0003469958960000075
wherein, Kx,Kv∈R3×3Is the gain matrix of the position velocity loop. The output of the position velocity loop is a linear acceleration command.
Thirdly, the specific method for designing the attitude controller based on the nonlinear geometric control theory comprises the following steps:
the rotating motion equation and the kinetic equation of the subsystem unmanned aerial vehicle are as follows:
Figure BDA0003469958960000081
Figure BDA0003469958960000082
wherein ^ can be defined by x, y ∈ R3,
Figure BDA0003469958960000083
Thus obtaining the product. Omega is unmanned aerial vehicle's angular velocity, and J is the inertia of organism. M is the sum moment that the drone is subjected to. The input to the attitude controller is RcmdAnd is obtained by a position controller. The error of the inner loop can be expressed as:
Figure BDA0003469958960000084
wherein e isRIs the error of the rotation matrix; e.g. of the typeΩIs the error in angular velocity; v is the inverse transformation of the V; omegacmdIs an angular velocity command. According to the rotation motion equation of the unmanned aerial vehicle subsystem, the control law of an inner ring is designed as follows:
Figure BDA0003469958960000085
wherein, KR,KΩ∈R3×3Is the gain matrix of the angle and angular velocity loops. In the process of executing 90-degree overturning splicing in the attitude control mode, the control distribution of the unmanned aerial vehicle subsystem is different from that of the flight mode. In flight mode, unmanned aerial vehicle's gravity can not produce moment, and in attitude control mode, because unmanned aerial vehicle needs to regard coupling mechanism as the hinge to realize the upset, so gravity can produce the moment of resistance, and the formula of control distribution is as follows:
Figure BDA0003469958960000086
wherein a and b are unmanned aerial vehicle size parameters; is the angle of rotation around the hinge connection mechanism; f1，F2Is the tension of the motor of the unmanned aerial vehicle. As shown in FIG. 6, F1The pulling force generated by two rotors close to the coupling mechanism, F2The tension created for the two rotors that are far from the attachment mechanism (in attitude mode). a is F1The horizontal distance of the two rotors to the connection mechanism; b is F2Horizontal distance of the two rotors to the connection mechanism.
Fourthly, the specific method for designing the rolling controller of the hemispherical unmanned system comprises the following steps:
the subsystem unmanned aerial vehicles numbered 1, 2, 3 and 4 are combined into a hemisphere, and need to roll and advance towards the directions of No. 5 and No. 6 unmanned aerial vehicles. No. 5 and No. 6 unmanned aerial vehicles adopt attitude controllers when splicing is not finished, and attitude angle instructions are all 0 degrees, so that the unmanned aerial vehicles keep horizontal in the splicing process. 2. No. 4 unmanned aerial vehicle also adopts attitude controller, uses the rotation matrix to characterize the gesture, and the direction of control organism Z axle is parallel with ground, prevents that the hemispheroid part from toppling over to the side in rolling the advancing. 1. No. 3 unmanned aerial vehicle adopts the angular velocity controller, and is the same roughly with the controller of four rotor flight modes, and two unmanned aerial vehicles provide the pitching moment that advances jointly, drive whole hemispheroid and roll forward and realize the concatenation. 2. No. 4 unmanned aerial vehicle also switches to angular velocity controller in case accomplish the concatenation, provides the moment that the spheroid rolled together.
The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.

Claims (8)

1. A control framework for autonomous splicing of a distributed multi-dwelling spherical unmanned system is characterized by comprising a plurality of unmanned aerial vehicles, wherein the unmanned aerial vehicles are spliced to form the spherical unmanned system, and a flight mode, an attitude control mode and a sphere rolling mode are realized at different splicing stages; the control framework comprises a position controller based on nonlinear incremental dynamic inversion, an attitude controller based on nonlinear geometric control theory and a hemispherical unmanned system rolling controller;
the position controller is used for realizing accurate butt joint of the splicing mechanism of the unmanned aerial vehicle in an external visual positioning environment; the attitude controller is used for controlling the attitude of the unmanned aerial vehicle to reach 90 degrees and turning the unmanned aerial vehicle into a hemisphere from a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispheroids to roll towards the direction of incomplete splicing, so that the whole sphere is spliced.
2. The distributed multi-dwelling spherical unmanned system autonomous-stitching control architecture according to claim 1, wherein the flight mode enables multi-level formation flight and aerial docking of the unmanned aerial vehicles; the attitude control mode realizes that the unmanned aerial vehicles are spliced into hemispheres; the rolling mode realizes rolling control of a ground sphere mode and the splicing of hemispheres into a complete sphere.
3. The control architecture for the autonomous splicing of the distributed multi-dwelling spherical unmanned system according to claim 1, wherein the unmanned aerial vehicles are spliced through electromagnetic connection mechanisms, the electromagnetic connection mechanisms are located at the midpoints of four sides of the unmanned aerial vehicles, electromagnets are mounted on the electromagnetic connection mechanisms, and attraction and separation of the electromagnets are realized by controlling on-off of current; the electromagnetic connecting mechanism is connected with the unmanned aerial vehicle shell through a movable hinge mechanism, the hinge mechanism comprises a rotating shaft, and the electromagnetic connecting mechanism rotates around the rotating shaft to form two states of ejection and recovery; and a coil spring is arranged at the rotating shaft, so that the electromagnetic connecting mechanism is in a popup state under the state of not receiving external force, and the suction surface of the electromagnet is parallel to the plumb bob surface when the electromagnetic connecting mechanism pops.
4. The autonomous splicing control architecture of the distributed multi-dwelling spherical unmanned system according to claim 3, wherein the electromagnets are rectangular solids to achieve limiting in the rolling direction of the unmanned aerial vehicle.
5. The control architecture for the autonomous splicing of the distributed multi-dwelling spherical unmanned system according to claim 3, wherein six unmanned aerial vehicles are spliced, the six unmanned aerial vehicles hover and form a topological structure, the position controller controls the six unmanned aerial vehicles to gather towards the center, and the electromagnetic connecting mechanisms in the popup state attract each other to realize butt joint when the distance is short, and at the moment, the six unmanned aerial vehicles are located in the same plane and cooperatively control to keep postures and realize landing; six unmanned aerial vehicles are connected in a cross manner, the four transverse unmanned aerial vehicles are numbered from left to right in sequence as 6, 5, 1 and 3, the No. 2 unmanned aerial vehicle is connected above the No. 1 unmanned aerial vehicle, and the No. 4 unmanned aerial vehicle is connected below the No. 1 unmanned aerial vehicle; 2. the No. 3 and No. 4 unmanned aerial vehicles enter an attitude control mode, an electromagnetic connecting mechanism is used as a support, 90-degree overturning is realized through an attitude controller, the No. 1, No. 2, No. 3 and No. 4 unmanned aerial vehicles are combined into a hemisphere, and the rolling control mode is entered; 1. the No. 2 unmanned aerial vehicle provides pitching moment to enable the hemispheroid to roll towards the No. 5 and No. 6 unmanned aerial vehicles, and the No. 3 and No. 4 unmanned aerial vehicles cooperatively provide tension to keep the hemispheroid balanced in the rolling direction; in the rolling process of the hemispheroid, the electromagnetic connecting mechanisms on the two sides of the No. 5 and No. 6 unmanned aerial vehicles are connected with the electromagnets of the No. 2, No. 3 and No. 4 unmanned aerial vehicles, so that the spherical combination is realized.
6. The distributed multi-dwelling spherical unmanned system autonomous splicing control architecture according to any one of claims 1-5, wherein the position controller based on the nonlinear incremental dynamic inversion is specifically:
the translational motion equation and the kinetic equation of the unmanned aerial vehicle are as follows:
Figure FDA0003469958950000011
Figure FDA0003469958950000012
wherein x is the drone position coordinate; v is the unmanned aerial vehicle velocity vector; m is the unmanned aerial vehicle mass; e.g. of the type3Is a unit vector, e3＝[0,0,1](ii) a g is the acceleration of gravity; r ═ bx by bz]The element SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; tau is the ratio of the tension to the mass of the rotor of the drone; f. ofextRepresenting external disturbances to the drone, including additional aerodynamic forces due to the incoming flow and unmodeled dynamic characteristics of the actuators themselves; the position controller based on the nonlinear incremental dynamic inverse comprises a position velocity ring and a linear acceleration ring, wherein the linear acceleration ring is based on a kinetic equation, an INDI controller is adopted, external interference is estimated in real time through a sensor, and compensation is carried out in the controller; the disturbance term is presented for equation (2) and the acceleration and tension terms are represented by the sensor measurements:
fext＝m(af-τfbz-ge3) (3)
wherein, afAcceleration measurements taken by the sensor; bzIs a unit projection vector of the z axis of the unmanned aerial vehicle system under the ground system, namely R ═ bx,by,bz]The third column of (c); tau isfThe ratio of the tension to the mass of the rotor of the unmanned aerial vehicle obtained by the sensor; the influence caused by disturbance can be eliminated by substituting formula (3) for formula (2), and an expression of the acceleration a of the unmanned aerial vehicle without an external disturbance term is obtained:
Figure FDA0003469958950000021
the input of the linear acceleration loop is a desired acceleration acmdThe output is an attitude angle command RcmdCombined tensile force FcmdInstructions; and (3) inverting the attitude angle and the resultant tension instruction by the formula (4) to obtain a control law of the linear acceleration ring:
τcmdRcmde3＝acmd-af+τfbz (5)
wherein tau iscmdIs a scalar quantity, Rcmde3Is a vector; calculating the mode of the left side of the equation to obtain a resultant tension instruction, and unitizing the resultant tension instruction to obtain a third column of the expected rotation matrix; and then, through a yaw angle instruction, solving vector cross multiplication to obtain a complete rotation matrix instruction:
Fcmd＝-m||τcmdRcmde3||2 (6)
Figure FDA0003469958950000022
according to bzcmdAnd determination of yaw angle psi of the drone bxcmdAnd bycmdAnd further determining the command value R of the rotation matrixcmd：
Figure FDA0003469958950000023
Figure FDA0003469958950000024
Rcmd＝[bxcmd bycmd bzcmd] (10)
The position and speed ring does not relate to an external force disturbance term in a kinematic equation, a PD controller is adopted, and the control law is as follows:
Figure FDA0003469958950000025
wherein, Kx,Kv∈R3×3A gain matrix that is a position velocity loop; the output of the position velocity loop is a linear acceleration command.
7. The distributed multi-dwelling spherical unmanned system autonomous splicing control architecture according to claim 6, wherein the attitude controller based on the nonlinear geometric control theory is specifically:
the rotational motion equation and the kinetic equation of the unmanned aerial vehicle are as follows:
Figure FDA0003469958950000031
Figure FDA0003469958950000032
wherein ^ is defined by x, y ∈ R3,
Figure FDA0003469958950000033
Obtaining; omega is the angular velocity of the unmanned aerial vehicle, J is the moment of inertia of the body; m is the sum moment received by the unmanned aerial vehicle; the input to the attitude controller is RcmdObtained by a position controller; the error of the inner loop is expressed as:
Figure FDA0003469958950000034
wherein e isRError of the rotation matrix; e.g. of the typeΩIs the error in angular velocity; omegacmdIs an angular velocity command; v is the inverse transformation of the V; according to the rotational motion equation (13), the control law of the inner ring is designed as follows:
Figure FDA0003469958950000035
wherein, KR,KΩ∈R3×3A gain matrix that is a loop of angles and angular velocities; in the process of executing 90 upset concatenation under the attitude control mode, unmanned aerial vehicle uses electromagnetic connection mechanism as the hinge to realize the upset, so gravity can produce the moment of resistance, and the formula of control distribution is as follows:
Figure FDA0003469958950000036
wherein phi is the angle of rotation around the hinge connection mechanism; f1The tension generated by the two rotors close to the connecting mechanism; f2Tension generated for two rotors that are remote from the attachment mechanism; a is F1The horizontal distance of the two rotors to the connection mechanism; b is F2Horizontal distance of the two rotors to the connection mechanism.
8. The distributed multi-dwelling spherical unmanned system autonomous splicing control architecture according to claim 5, wherein the hemispherical unmanned system rolling controller is specifically:
1. the No. 2, No. 3 and No. 4 unmanned aerial vehicles are combined into a hemisphere and roll forward in the directions of the No. 5 and No. 6 unmanned aerial vehicles; the No. 5 and No. 6 unmanned aerial vehicles adopt attitude controllers when splicing is not finished, and attitude angle instructions are all 0 degrees, so that the unmanned aerial vehicles are kept horizontal in the splicing process; 2. the No. 4 unmanned aerial vehicle adopts an attitude controller, uses a rotation matrix to represent the attitude, controls the Z-axis direction of the body to be parallel to the ground, and prevents the hemispherical body part from inclining to the side surface during rolling forward; 1. the No. 3 unmanned aerial vehicle adopts an angular velocity controller, and the two unmanned aerial vehicles jointly provide forward pitching moment to drive the whole hemispheroid to roll forward to realize splicing; 2. no. 4 unmanned aerial vehicle switches to angular velocity controller after accomplishing the concatenation, provides the rolling moment of spheroid jointly.
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