CN114476056B - Control framework for autonomous splicing of distributed amphibious spherical unmanned system - Google Patents
Control framework for autonomous splicing of distributed amphibious spherical unmanned system Download PDFInfo
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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, a gesture control mode and a sphere rolling mode are realized at different stages of splicing; the control architecture comprises a position controller based on nonlinear increment dynamic inversion, a posture 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 gesture controller is used for controlling the gesture of the unmanned aerial vehicle to reach 90 degrees, and the unmanned aerial vehicle is overturned into a hemisphere by a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispherical body to roll towards the direction of unfinished splicing, so that the whole spherical body can be spliced. The control architecture simplifies the connection mechanism of each subsystem unmanned aerial vehicle, and simultaneously realizes the autonomous splicing control of multiple unmanned aerial vehicles.
Description
Technical Field
The invention relates to the technical field of control of rotary-wing unmanned aerial vehicles and spherical robots, in particular to a multi-machine cooperative control and large-angle attitude control frame of an unmanned aerial vehicle. And more particularly to coordinated control of multiple machines in multiple modes.
Background
The distributed amphibious 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 sub-system unmanned aerial vehicles, wherein each unmanned aerial vehicle is in a four-rotor wing configuration and has the capability of independently executing tasks in the air; at the same time, they are mutually equipped with electromagnetic adsorption devices, and can be mutually connected into a sphere, so that the system can represent the movement characteristics of the sphere on the ground. The distributed combined structure has extremely wide application prospect in military and civilian life. In recent years, a large number of amphibious unmanned innovative mobile platforms are researched all over the world, and some platforms adopt fixed wing structures, but aircraft adopting the fixed wing structures can take off only by long running; although some amphibious mobile platforms flying by using the rotorcraft principle have the advantages of vertical take-off and landing, the bare propellers can form a great threat to surrounding objects, and the platforms have the problems of single configuration, isolated work and great functional limitation in safety or working space; on the one hand, the research on the spherical robot rarely considers expanding the amphibious property of the spherical robot, and on the other hand, a gravity moment driving scheme is adopted, and the scheme couples three degrees of freedom of the sphere together, so that the problems of single configuration and large functional limitation are also caused.
For the distributed multi-dwelling spherical unmanned aerial vehicle system, the process of splicing and converting the multi-shelf system unmanned aerial vehicle from a flight mode to a ground sphere mode is complex, and the design of a connecting mechanism between the subsystem unmanned aerial vehicles, the design of a splicing process and the design of a specific control law in the splicing process are involved. The subsystem unmanned aerial vehicle adopts a four-rotor configuration, and the basic controller design method is mature. However, the four-rotor unmanned aerial vehicle control method based on the traditional theory still has the defects for the distributed multi-dwelling spherical unmanned aerial vehicle system, and mainly comprises the following aspects: (1) When the flight control system is designed based on a traditional control strategy, the Euler angle is generally adopted to represent the gesture of the rotor unmanned aerial vehicle, and the phenomenon of universal joint locking exists under the condition of a large gesture angle, for example, when the pitch angle is 90 degrees, the gesture of the unmanned aerial vehicle can be represented by a plurality of Euler angle combinations, so that the feedback value of the controller is deviated. (2) In traditional multi-machine cooperation and unmanned aerial vehicle formation control, each unmanned aerial vehicle is not physically connected, but collision is prevented, so that the requirement on the precision of the position is low. The spherical mode corresponding to the control method is formed by splicing and combining a plurality of rotor subsystems, and has higher requirements on the position control of the subsystems.
Disclosure of Invention
In order to solve the problem of high functional limitation of the amphibious unmanned system, the invention adopts the concept of modular assembly, and provides a distributed amphibious spherical unmanned system. The device can have a better configuration in different ground and air environments, and consists of a plurality of independent rotor wing driving flight unit modules, wherein each module has the capability of independently executing tasks in the air; at the same time, they are mutually equipped with electromagnetic adsorption devices, and can be mutually connected into a sphere, so that the system can represent the movement characteristics of the sphere on the ground. The reference data shows that the research on the amphibious spherical system at home and abroad is very little at present, and the process of combining unmanned aerial vehicles of a multi-frame system into spheres is critical for the combined spherical unmanned aerial vehicle system. In view of the above, the invention provides a splicing control architecture for a modal conversion process of a distributed multi-dwelling spherical unmanned system, which comprises the following specific technical scheme:
the control framework for autonomous splicing of the distributed multi-dwelling spherical unmanned aerial vehicle system comprises a plurality of unmanned aerial vehicles, wherein the unmanned aerial vehicles are spliced to form the spherical unmanned aerial vehicle system, and a flight mode, a gesture control mode and a sphere rolling mode are realized at different stages of splicing; the control architecture comprises a position controller based on nonlinear increment dynamic inversion, a posture 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 gesture controller is used for controlling the gesture of the unmanned aerial vehicle to reach 90 degrees, and the unmanned aerial vehicle is overturned into a hemisphere by a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispherical body to roll towards the direction of unfinished splicing, so that the whole spherical body can be spliced.
In particular, the flight mode realizes multi-level formation flight and air docking of the unmanned aerial vehicle; the attitude control mode realizes that the unmanned aerial vehicle is spliced into a hemisphere; the rolling mode realizes the rolling control of the ground sphere mode and the assembly of the hemispheres into a complete sphere.
In particular, the unmanned aerial vehicle is spliced through an electromagnetic connecting mechanism, the electromagnetic connecting mechanism is positioned at the middle point of four sides of the unmanned aerial vehicle, an electromagnet is arranged on the electromagnetic connecting mechanism, and the attraction and separation of the electromagnet are realized by controlling the 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; the coil spring is arranged at the rotating shaft, so that the electromagnetic connecting mechanism is in an ejecting state under the condition of no external force, and the suction surface of the electromagnet is parallel to the plumb surface when the electromagnetic connecting mechanism ejects.
In particular, the electromagnet is cuboid, and limiting in the rolling direction of the unmanned aerial vehicle is achieved.
Particularly, the 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, the electromagnetic connection mechanisms in the pop-up state are mutually attracted to realize the butt joint when the distance is relatively close, and at the moment, the six unmanned aerial vehicles are positioned in the same plane, and cooperatively control to keep the gesture and realize the landing; six unmanned aerial vehicles are connected in a cross shape, the upper parts of the four transverse unmanned aerial vehicles are sequentially numbered 6, 5, 1, 3 and 1 from left to right, the upper parts of the unmanned aerial vehicles are connected with the No. 2 unmanned aerial vehicle, and the lower parts of the unmanned aerial vehicles are connected with the No. 4 unmanned aerial vehicle; 2. the unmanned aerial vehicles No. 3 and No. 4 enter a gesture control mode, an electromagnetic connecting mechanism is used as a support, 90-degree overturning is realized through a gesture controller, the unmanned aerial vehicles No. 1, 2, 3 and No. 4 are combined into a hemisphere, and a rolling control mode is entered; 1. the unmanned aerial vehicle No. 2 provides pitching moment to enable the hemispheroids to roll towards the unmanned aerial vehicles No. 5 and No. 6, and the unmanned aerial vehicles No. 3 and No. 4 cooperatively provide pulling force to keep the balance of the hemispheroids in the rolling direction; in the rolling process of the hemispheroids, electromagnetic connecting mechanisms at two sides of the No. 5 unmanned aerial vehicle and the No. 6 unmanned aerial vehicle are connected with electromagnets of the No. 2 unmanned aerial vehicle, the No. 3 unmanned aerial vehicle and the No. 4 unmanned aerial vehicle, so that the split of the hemispheroids is realized.
In particular, the nonlinear increment dynamic inversion-based position controller specifically comprises:
the translational motion equation and the kinetic equation of the unmanned plane are as follows:
wherein x is the position coordinate of the unmanned aerial vehicle; v is the unmanned vehicle speed vector; m is the unmanned aerial vehicle mass; e, e 3 Is a unit vector, e 3 ＝[0,0,1]The method comprises the steps of carrying out a first treatment on the surface of the g is the gravitational acceleration; r= [ b ] x b y b z ]E, SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; τ is the ratio of the tension of the unmanned rotor to the mass; f (f) ext Representing external interference suffered by the unmanned aerial vehicle, including additional aerodynamic force generated by incoming flow and unmodeled dynamic characteristics of the executing mechanism; the position controller based on nonlinear incremental dynamic inversion comprises a position speed ring and a linear acceleration ring, wherein the linear acceleration ring adopts an INDI controller based on a dynamic equation, estimates external interference in real time through a sensor, and compensates in the controller; the disturbance term is presented to equation (2) and the acceleration and tension terms are represented by the sensor measurements:
f ext ＝m(a f -τ f b z -ge 3 ) (3)
wherein a is f Is an acceleration measurement obtained by a sensor; b z Is the unit projection vector of the z axis of the body system of the unmanned aerial vehicle under the ground system, namely R= [ b ] x ,b y ,b z ]Is a third column of (2); τ f The ratio of the pulling force of the unmanned aerial vehicle rotor wing to the mass obtained by the sensor is substituted in the formula (3) to eliminate the influence caused by disturbance, so that the expression of the unmanned aerial vehicle acceleration a without external force disturbance term is obtained:
the linear acceleration loop is input as the expected acceleration a cmd Output is attitude angle instruction R cmd And a combined pulling force F cmd An instruction; and (3) inverting the attitude angle and the tension command in the formula (4) to obtain the control law of the linear acceleration ring:
τ cmd R cmd e 3 ＝a cmd -a f +τ f b z (5)
wherein τ cmd Is a scalar, R cmd e 3 Is a vector; obtaining a combined tension instruction by modeling the left side of the equation, and obtaining a third column of the expected rotation matrix by unitizing the combined tension instruction; and then, obtaining a complete rotation matrix instruction by vector cross multiplication through a yaw angle instruction:
F cmd ＝-m||τ cmd R cmd e 3 || 2 (6)
according to b zcmd And the yaw angle psi of the unmanned aerial vehicle to determine b xcmd And b ycmd Further, the instruction value R of the rotation matrix is determined cmd ：
R cmd ＝[b xcmd b ycmd b zcmd ] (10)
The position and speed loop does not relate to an external force disturbance term in a kinematic equation, and a PD controller is adopted, so that the control law is as follows:
wherein K is x ,K v ∈R 3×3 Gain matrix for position and velocity loop; the output of the position and speed loop is a linear acceleration command.
In particular, the attitude controller based on the nonlinear geometric control theory specifically comprises:
the rotational motion equation and the kinetic equation of the unmanned aerial vehicle are as follows:
wherein, the definition of the lambda is defined by x, y epsilon R 3 ,
Obtaining; omega is the angular velocity of the unmanned aerial vehicle, J is the rotational inertia of the body; m is the sum torque experienced by the unmanned aerial vehicle; the input of the gesture controller is R cmd Obtained by a position controller; the error of the inner ring is expressed as:
wherein e R Is the error of the rotation matrix; e, e Ω Is the error of angular velocity; omega shape cmd Is an angular velocity command; the V-shaped is inverse transformation of V; according to a rotary motion equation (13), designing a control law of the inner ring as follows:
wherein K is R ,K Ω ∈R 3×3 Gain matrix for angle and angular velocity loops; in the process of executing 90-degree overturning splicing in the attitude control mode, the unmanned aerial vehicle uses the electromagnetic connecting mechanism as a hinge to realize overturning, so gravity can generate a resisting moment, and a formula for controlling distribution is as follows:
wherein phi is the angle of rotation about the hinge connection; f (F) 1 Pulling force generated by two rotors close to the connecting mechanism; f (F) 2 Pulling force for two rotors remote from the coupling mechanismThe method comprises the steps of carrying out a first treatment on the surface of the a is F 1 The horizontal distance of the two rotors to the connection mechanism; b is F 2 The horizontal distance of the two rotors to the connection mechanism.
In particular, the hemispherical unmanned system rolling controller specifically comprises:
1. 2, 3 and 4 unmanned aerial vehicles are combined into a hemisphere, and the hemisphere rolls and advances in the directions of the 5 and 6 unmanned aerial vehicles; the unmanned aerial vehicle 5 and the unmanned aerial vehicle 6 adopt gesture controllers when the splicing is not completed, and gesture angle instructions are all 0 degrees, so that the unmanned aerial vehicle is kept horizontal in the splicing process; 2. the unmanned aerial vehicle No. 4 adopts a gesture controller, uses a rotation matrix to represent gesture, controls the direction of a Z axis of a machine body to be parallel to the ground, and prevents the hemispherical body from tilting to the side surface in 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 hemisphere to roll forward so as to realize splicing; 2. and after the 4 # unmanned aerial vehicle finishes splicing, switching to an angular speed controller to jointly provide the moment of ball rolling.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a flow scheme of a sphere combined unmanned system formed by splicing a plurality of sub-system unmanned aerial vehicles, and adopts an electromagnetic hinge connecting mechanism, so that each sub-unmanned aerial vehicle does not need to be spliced in place in one step to form a sphere, but is firstly in a plane to realize butt joint, and then is spliced into a sphere in a three-dimensional way. The difficulty in control is simplified by designing the connecting mechanism, and engineering realization is easy.
2. Compared with the traditional Euler angle representation gesture controller, the gesture controller has no singular problem, so that the aircraft can achieve a large gesture. Meanwhile, simulation results show that tracking accuracy is superior to that of a PID controller when the gesture instruction with a large angle is tracked.
Drawings
FIG. 1 is a schematic view of a hinge connection;
wherein 1 is a subsystem unmanned aerial vehicle housing; 2 is an electromagnet arranged on the base of the electromagnetic connecting mechanism; 3 is a rotatable electromagnetic connection mechanism; (a) is a schematic view of the state of the electromagnetic connection mechanism when ejected; (b) is a schematic view of the state of the electromagnetic connection mechanism when the electromagnetic connection mechanism is retracted;
FIG. 2 is a schematic illustration of a two-rack system unmanned aerial vehicle docking;
FIG. 3 is a schematic view of a spherical combining robot splice;
FIG. 4 is a flow chart of a spherical combined robot modality conversion;
FIG. 5 is a graph of 90 response tracking in attitude control mode;
fig. 6 is a schematic diagram of the drone dimension parameters and the drone motor tension.
Detailed Description
The invention will be described in further detail with reference to the drawings and examples.
The invention provides a control framework for autonomous splicing of a distributed amphibious spherical unmanned system, and the control framework can be divided into a flight mode, a gesture control mode and a sphere rolling mode according to different stages of splicing. The flight mode is mainly responsible for the operation of multi-level formation flight and aerial docking of the subsystem unmanned aerial vehicle; the attitude control mode is mainly used for splicing into a hemisphere; the rolling mode is mainly used for rolling control of the ground sphere mode and the stage of combining the hemispheres into a complete sphere; the specific design steps are as follows:
first, electromagnetic connection mechanisms among unmanned aerial vehicles of all rotor subsystems and design of splicing processes. The single rotor subsystem unmanned aerial vehicle adopts the configuration of four rotors, and because of the platform characteristic of four rotors, the aerodynamic force that the rotor produced always is parallel with the z-axis of organism. In the ground spherical mode, the z axis of six subsystems combined into a sphere points to the outer surface of the sphere from the center of the sphere, if the subsystems are required to be directly spliced into the sphere in air flight, only the unmanned aerial vehicle positioned at the bottom of the sphere is in a smaller posture, and five unmanned aerial vehicles around the sphere and at the top of the sphere are required to be close to and connected with each other in a very large posture angle, so that the control is difficult. The invention designs a movable electromagnetic connecting mechanism, the rotor subsystem is not required to be directly spliced into a sphere in flight, but is firstly connected in sequence in a horizontal plane to form a cube which is unfolded into a planar layout, and then the cube falls to the ground. On the ground, the splicing of the spheres is realized through the rotatable connecting mechanism and the attitude control of the subsystem. The geometric topology structure of the six-frame system unmanned aerial vehicle when docking in a plane is not limited to the structure of the upper left corner in fig. 3, and various plane patterns which are developed into planes in an orthocube can be used as the topology structure of the aerial 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 receiving external force. The electromagnet adopted by the electromagnetic connecting mechanism is not limited to a cylindrical shape, and can also be a cuboid shape. Compare in columniform electro-magnet, cuboid shape electro-magnet can be spacing on unmanned aerial vehicle's the direction of rolling, unmanned aerial vehicle can not surpass the side and empty at the in-process that carries out 90 upset, but general electro-magnet that accords with the size is cylindric, 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 nonlinear increment dynamic inverse. Because the proposed splicing method requires six rotor subsystem unmanned aerial vehicles to dock in the air, the invention designs a precise position controller based on nonlinear incremental dynamic inversion (INDI). Under the environment of external visual positioning, millimeter-level control precision can be realized, and accurate butt joint of the splicing mechanism is ensured.
Thirdly, designing a posture controller based on a nonlinear geometric control theory. The method for representing the gesture by the Euler angle is widely adopted in the traditional unmanned aerial vehicle gesture control, and can decouple three channels for representing the gesture, and controllers are respectively designed, so that the method has the advantages of intuitiveness and easiness in understanding. But at large angles a singular problem arises. According to the invention, the rotation matrix is used for representing the gesture of the unmanned aerial vehicle, so that the gesture of the unmanned aerial vehicle can be controlled to reach 90 degrees, and the control of turning the plane into a hemisphere is realized.
And fourthly, designing a rolling controller of the hemispherical unmanned system. The part spliced into the hemispheroids adopts a sphere rolling controller to roll towards the direction of unfinished splicing, so that the whole sphere is spliced.
The first step, the electromagnetic connection mechanism between each rotor subsystem unmanned aerial vehicle is in the specific form:
the electromagnetic connecting mechanism is connected with the unmanned aerial vehicle shell by adopting a movable hinge mechanism, wherein the electromagnetic connecting mechanism is arranged at the midpoint of four sides of the subsystem unmanned aerial vehicle. The electromagnetic connecting mechanism is provided with an electromagnet, and the attraction and separation operation 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 ejecting and retracting. The rotor subsystem is horizontally placed as a reference, and when the electromagnetic connecting mechanism pops up, the suction surface of the electromagnet is parallel to the plumb surface. The rotating shaft of the hinge mechanism is provided with a coil spring, so that the electromagnetic connecting mechanism is in an ejecting state under the condition of no external force.
The specific form of the splicing process is as follows: six unmanned aerial vehicles in formation flight hover and form a specific topological structure, at the moment, the unmanned aerial vehicles in a hovering state are controlled by a position controller and slowly gather towards the center, and when the distance is relatively close, electromagnetic connection mechanisms in a popup state can attract each other and realize butt joint. At this time, all the unmanned aerial vehicles are located in the same plane, and cooperatively control and maintain the posture and realize landing. The subsystem unmanned aerial vehicle automatically allocates numbers according to the position of the unmanned aerial vehicle in formation after aerial docking, as shown in fig. 2. After the butt joint is finished, unmanned aerial vehicles with the numbers of 2, 3 and 4 enter a gesture control mode, an electromagnetic connecting mechanism is used as a support, and 90-degree overturning is realized through a gesture controller. At this time, 1, 2, 3, 4 are combined into a hemisphere, and the scroll control mode is entered. 1. 2 the unmanned aerial vehicle of serial number provides pitching moment and makes the hemisphere roll towards 5, 6 unmanned aerial vehicle. 3. Unmanned aerial vehicle No. 4 cooperatively provides a pulling force to maintain the equilibrium of the hemisphere in the roll direction. In the rolling process of the hemispheres, electromagnetic connecting mechanisms at two sides of the No. 5 and No. 6 unmanned aerial vehicle are connected with electromagnetic connecting mechanisms at No. 2, no. 3 and No. 4, so that the assembly of the hemispheres is realized.
The second step, the specific method for designing the position controller based on nonlinear increment dynamic inversion is as follows:
the translational motion equation and the kinetic equation of the subsystem unmanned aerial vehicle are as follows:
wherein x is the position coordinate of the unmanned aerial vehicle; v is the unmanned vehicle speed vector; m is the unmanned aerial vehicle mass; e, e 3 Is a unit vector, e 3 ＝[0,0,1]The method comprises the steps of carrying out a first treatment on the surface of the g is the gravitational acceleration; r= [ b ] x b y b z ]E, SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; τ is the ratio of the tension of the unmanned rotor to the mass; f (f) ext Representing the external disturbances experienced by the drone, including additional aerodynamic forces due to the incoming flow and the unmodeled dynamic characteristics of the actuator itself. The position controller based on nonlinear incremental dynamic inversion mainly comprises a position speed ring and a linear acceleration ring, wherein the linear acceleration ring is based on a dynamic equation, and in order to reduce the influence caused by external interference, the 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 to equation (2) and the acceleration and tension terms are represented by the sensor measurements:
f ext ＝m(a f -τ f b z -ge 3 ) (3)
wherein a is f Is an acceleration measurement obtained by a sensor; b z Is the unit projection vector of the z axis of the body system of the unmanned aerial vehicle under the ground system, namely R= [ b ] x ,b y ,b z ]Is a third column of (2); τ f Is the ratio of the pulling force of the unmanned aerial vehicle rotor wing to the mass obtained by the sensor. The estimated disturbance is substituted into the formula (2) to eliminate the influence caused by the disturbance, so that an expression of the unmanned plane acceleration a without an external disturbance term is obtained:
the linear acceleration loop is input as the expected acceleration a cmd Output is attitude angle instruction R cmd And a combined pulling force F cmd An instruction. The control law of the linear acceleration ring can be obtained by inverting the attitude angle and the tension command:
τ cmd R cmd e 3 ＝a cmd -a f +τ f b z (5)
wherein τ cmd Is a scalar, R cmd e 3 Is a vector. The resultant tension command can be obtained by modulo the left side of the equation, and the third column b of the desired rotation matrix can be obtained by unitizing the resultant tension command zcmd . And then according to the yaw angle instruction, vector cross multiplication is carried out to obtain a complete rotation matrix instruction.
F cmd ＝-m||τ cmd R cmd e 3 || 2 (6)
According to b zcmd And the yaw angle psi of the unmanned aerial vehicle can be uniquely determined b xcmd And b ycmd And further determining the instruction value of the rotation matrix. The specific process is as follows: first a vector b is defined in terms of yaw angle m ＝[cosψ sinψ 0] T The rotation matrix is constructed using this vector as an intermediate vector. Then pass through vector b zcmd Cross-multiplying to obtain b of the system ycmd ：
Finally, b is obtained ycmd And b zcmd Cross multiplying to obtain b of the machine system xcmd Thereby obtaining a complete rotation matrix instruction.
R cmd ＝[b xcmd b ycmd b zcmd ] (10)
The position and speed loop does not relate to an external force disturbance term in a kinematic equation, so that a traditional PD controller can be adopted, and the control law is as follows:
wherein K is x ,K v ∈R 3×3 Is a gain matrix of the position velocity loop. The output of the position and speed loop is a linear acceleration command.
Thirdly, designing a specific method for the attitude controller based on the nonlinear geometric control theory, wherein the specific method comprises the following steps:
the rotational motion equation and the kinetic equation of the subsystem unmanned aerial vehicle are as follows:
wherein, the definition of a can be defined by x, y E R 3 ,
Obtained. Omega is the angular velocity of the unmanned aerial vehicle, and J is the rotational inertia of the body. M is the sum torque experienced by the drone. The input of the gesture controller is R cmd Obtained by a position controller. The error of the inner loop can be expressed as:
wherein e R Is the error of the rotation matrix; e, e Ω Is the error of angular velocity; the V-shaped is inverse transformation of V; omega shape cmd Is an angular velocity command. According to a rotational motion equation of the subsystem unmanned aerial vehicle, designing a control law of the inner ring as follows:
wherein K is R ,K Ω ∈R 3×3 A gain matrix for 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 subsystem unmanned aerial vehicle is different from that of the flight mode. In the flight mode, the gravity of the unmanned aerial vehicle does not generate moment, while in the attitude control mode, as the unmanned aerial vehicle needs to overturn by taking the connecting mechanism as a hinge, the gravity generates resistance moment, and the formula for controlling distribution is as follows:
wherein a and b are unmanned aerial vehicle size parameters; is the angle of rotation about the hinge connection; f (F) 1 ，F 2 Is the tension of the unmanned aerial vehicle motor. F as shown in FIG. 6 1 For the tension produced by two rotors situated close to the connecting mechanism, F 2 Tension (in attitude mode) is created for the two rotors that are far from the connection. a is F 1 The horizontal distance of the two rotors to the connection mechanism; b is F 2 The horizontal distance of the two rotors to the connection mechanism.
The third step, the specific method for designing the hemispherical unmanned system rolling controller is as follows:
the subsystem unmanned aerial vehicle with the numbers of 1, 2, 3 and 4 is combined into a hemisphere, and needs to roll and advance towards the directions of the unmanned aerial vehicles with the numbers of 5 and 6. The unmanned aerial vehicle No. 5 and No. 6 adopt gesture controllers when the splicing is not completed, and gesture angle instructions are all 0 degrees, so that the plane is kept horizontal in the splicing process. 2. The unmanned aerial vehicle No. 4 also adopts the gesture controller, uses rotatory matrix representation gesture, and the direction of control organism Z axle is parallel with ground, prevents hemisphere body part and leans over to the side in the roll forward. 1. No. 3 unmanned aerial vehicle adopts angular velocity controller, and is the same with four rotor flight mode's controller is general, and two unmanned aerial vehicles provide the pitching moment that advances jointly, drives whole hemisphere forward roll and realizes the concatenation. 2. The No. 4 unmanned aerial vehicle is also switched to the angular velocity controller once the splicing is completed, and the moment of ball rolling is provided together.
The above embodiments are merely for illustrating the design concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, the scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications according to the principles and design ideas of the present invention are within the scope of the present invention.
Claims (6)
1. The control framework for autonomous splicing of the distributed multi-dwelling spherical unmanned aerial vehicle system is characterized by comprising six unmanned aerial vehicles, wherein the six unmanned aerial vehicles are spliced to form the spherical unmanned aerial vehicle system, and a flight mode, a gesture control mode and a sphere rolling mode are realized at different stages of splicing; the control architecture comprises a position controller based on nonlinear increment dynamic inversion, a posture 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 gesture controller is used for controlling the gesture of the unmanned aerial vehicle to reach 90 degrees, and the unmanned aerial vehicle is overturned into a hemisphere by a plane; the hemispherical unmanned system rolling controller is used for controlling the hemispherical body to roll towards the direction of unfinished splicing, so that the whole spherical body is spliced;
the unmanned aerial vehicle is spliced through an electromagnetic connecting mechanism, the electromagnetic connecting mechanism is positioned at the middle points of four sides of the unmanned aerial vehicle, an electromagnet is arranged on the electromagnetic connecting mechanism, and the attraction and separation of the electromagnet are realized by controlling the 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; the rotating shaft is provided with a coil spring, so that the electromagnetic connecting mechanism is in an ejecting state under the condition of no external force, and when the electromagnetic connecting mechanism ejects, the suction surface of the electromagnet is parallel to the plumb surface;
the 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, the electromagnetic connection mechanisms in the pop-up state are mutually attracted to realize the butt joint when the distance is relatively close, and at the moment, the six unmanned aerial vehicles are positioned in the same plane, and cooperatively control to keep the gesture and realize the landing; six unmanned aerial vehicles are connected in a cross shape, the upper parts of the four transverse unmanned aerial vehicles are sequentially numbered 6, 5, 1, 3 and 1 from left to right, the upper parts of the unmanned aerial vehicles are connected with the No. 2 unmanned aerial vehicle, and the lower parts of the unmanned aerial vehicles are connected with the No. 4 unmanned aerial vehicle; 2. the unmanned aerial vehicles No. 3 and No. 4 enter a gesture control mode, an electromagnetic connecting mechanism is used as a support, 90-degree overturning is realized through a gesture controller, the unmanned aerial vehicles No. 1, 2, 3 and No. 4 are combined into a hemisphere, and a rolling control mode is entered; 1. the unmanned aerial vehicle No. 2 provides pitching moment to enable the hemispheroids to roll towards the unmanned aerial vehicles No. 5 and No. 6, and the unmanned aerial vehicles No. 3 and No. 4 cooperatively provide pulling force to keep the balance of the hemispheroids in the rolling direction; in the rolling process of the hemispheroids, electromagnetic connecting mechanisms at two sides of the No. 5 unmanned aerial vehicle and the No. 6 unmanned aerial vehicle are connected with electromagnets of the No. 2 unmanned aerial vehicle, the No. 3 unmanned aerial vehicle and the No. 4 unmanned aerial vehicle, so that the split of the hemispheroids is realized.
2. The control architecture for autonomous splice of a distributed multi-dwelling spherical unmanned system according to claim 1, wherein the flight mode enables multi-level formation flight and air docking of the unmanned aerial vehicle; the attitude control mode realizes that the unmanned aerial vehicle is spliced into a hemisphere; the rolling mode realizes the rolling control of the ground sphere mode and the assembly of the hemispheres into a complete sphere.
3. The control architecture for autonomous splicing of a distributed multi-dwelling spherical unmanned aerial vehicle system according to claim 1, wherein the electromagnet is a cuboid, and limiting in the rolling direction of the unmanned aerial vehicle is achieved.
4. A control architecture for autonomous splice of a distributed multi-dwelling spherical unmanned system according to any of claims 1-3, wherein the nonlinear incremental dynamic inverse-based position controller is specifically:
the translational motion equation and the kinetic equation of the unmanned plane are as follows:
wherein x is the position coordinate of the unmanned aerial vehicle; v is the unmanned vehicle speed vector; m is the unmanned aerial vehicle mass; e, e 3 Is a unit vector, e 3 ＝[0,0,1]The method comprises the steps of carrying out a first treatment on the surface of the g is the gravitational acceleration; r= [ b ] x b y b z ]E, SO (3) is a rotation matrix of the current state of the unmanned aerial vehicle; τ is the ratio of the tension of the unmanned rotor to the mass; f (f) ext Representing external interference suffered by the unmanned aerial vehicle, including additional aerodynamic force generated by incoming flow and unmodeled dynamic characteristics of the executing mechanism; the position controller based on nonlinear incremental dynamic inversion comprises a position speed ring and a linear acceleration ring, wherein the linear acceleration ring adopts an INDI controller based on a dynamic equation, estimates external interference in real time through a sensor, and compensates in the controller; the disturbance term is presented to equation (2) and the acceleration and tension terms are represented by the sensor measurements:
f ext ＝m(a f -τ f b z -ge 3 ) (3)
wherein a is f Is an acceleration measurement obtained by a sensor; b z Is the unit projection vector of the z axis of the body system of the unmanned aerial vehicle under the ground system, namely R= [ b ] x ,b y ,b z ]Is a third column of (2); τ f The ratio of the pulling force of the unmanned aerial vehicle rotor wing to the mass is obtained by a sensor; substituting the formula (3) into the formula (2) can eliminate the influence caused by disturbance, and obtain an expression of the unmanned plane acceleration a without an external force disturbance term:
the linear acceleration loop is input as the expected acceleration a cmd Output is attitude angle instruction R cmd And a combined pulling force F cmd An instruction; will beThe equation (4) inverts the attitude angle and the tension command to obtain the control law of the linear acceleration ring:
τ cmd R cmd e 3 ＝a cmd -a f +τ f b z (5)
wherein τ cmd Is a scalar, R cmd e 3 Is a vector; obtaining a combined tension instruction by modeling the left side of the equation, and obtaining a third column of the expected rotation matrix by unitizing the combined tension instruction; and then, obtaining a complete rotation matrix instruction by vector cross multiplication through a yaw angle instruction:
F cmd ＝-m||τ cmd R cmd e 3 || 2 (6)
according to b zcmd And the yaw angle psi of the unmanned aerial vehicle to determine b xcmd And b ycmd Further, the instruction value R of the rotation matrix is determined cmd ：
R cmd ＝[b xcmd b ycmd b zcmd ] (10)
The position and speed loop does not relate to an external force disturbance term in a kinematic equation, and a PD controller is adopted, so that the control law is as follows:
wherein K is x ,K v ∈R 3×3 Gain moment for position velocity loopAn array; the output of the position and speed loop is a linear acceleration command.
5. The control architecture for autonomous splice of a distributed multi-dwelling spherical unmanned system according to claim 4, 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:
wherein, the definition of the lambda is defined by x, y epsilon R 3 ,
Obtaining; omega is the angular velocity of the unmanned aerial vehicle, J is the rotational inertia of the body; m is the sum torque experienced by the unmanned aerial vehicle; the input of the gesture controller is R cmd Obtained by a position controller; the error of the inner ring is expressed as:
wherein e R Is the error of the rotation matrix; e, e Ω Is the error of angular velocity; omega shape cmd Is an angular velocity command; the V-shaped is inverse transformation of V; according to a rotary motion equation (13), designing a control law of the inner ring as follows:
wherein K is R ,K Ω ∈R 3×3 Gain matrix for angle and angular velocity loops; in the attitude controlIn the process of executing 90-degree overturning splicing in the control mode, the unmanned aerial vehicle uses the electromagnetic connecting mechanism as a hinge to realize overturning, so gravity can generate a resistance moment, and a formula for controlling distribution is as follows:
wherein phi is the angle of rotation about the hinge connection; f (F) 1 Pulling force generated by two rotors close to the connecting mechanism; f (F) 2 Pulling force generated for two rotors far from the connecting mechanism; a is F 1 The horizontal distance of the two rotors to the connection mechanism; b is F 2 The horizontal distance of the two rotors to the connection mechanism.
6. The control architecture for autonomous splice of a distributed multi-dwelling spherical unmanned system according to claim 1, wherein the hemispherical unmanned system roll controller is specifically:
1. 2, 3 and 4 unmanned aerial vehicles are combined into a hemisphere, and the hemisphere rolls and advances in the directions of the 5 and 6 unmanned aerial vehicles; the unmanned aerial vehicle 5 and the unmanned aerial vehicle 6 adopt gesture controllers when the splicing is not completed, and gesture angle instructions are all 0 degrees, so that the unmanned aerial vehicle is kept horizontal in the splicing process; 2. the unmanned aerial vehicle No. 4 adopts a gesture controller, uses a rotation matrix to represent gesture, controls the direction of a Z axis of a machine body to be parallel to the ground, and prevents the hemispherical body from tilting to the side surface in 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 hemisphere to roll forward so as to realize splicing; 2. and after the 4 # unmanned aerial vehicle finishes splicing, switching to an angular speed controller to jointly provide the moment of ball rolling.
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