CN112158329A - High-fault-tolerance deformable four-rotor aircraft and control method - Google Patents
High-fault-tolerance deformable four-rotor aircraft and control method Download PDFInfo
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Abstract
The invention provides a deformable four-rotor aircraft with high fault-tolerant rate and a control method, wherein the number of rotors of the aircraft is not less than four, and the rotors are all arranged at arms of the aircraft; the horn comprises a first joint and a second joint; the starting end of the first joint is fixed at the fuselage of the aircraft, and the first joint is connected with the starting end of the second joint through a first rotating mechanism which can horizontally rotate relative to the horizontal plane of the fuselage, so that the second joint can horizontally rotate relative to the horizontal plane of the fuselage; the second joint is connected with the rotor wing of the horn through a second rotating mechanism which can vertically rotate relative to the horizontal plane of the fuselage, so that the rotor wing can vertically rotate relative to the horizontal plane of the fuselage in the direction; the rotor wing can provide lift force to the aircraft through forward rotation or reverse rotation; the invention can solve the problem of damage to people or objects when the four-rotor aircraft fails and falls, and the problem of how to reduce the failure loss of the aircraft, and can continuously complete the flight task when a small number of rotors fail.
Description
Technical Field
The invention relates to the technical field of multi-rotor aircrafts, in particular to a deformable four-rotor aircraft with high fault tolerance and a control method.
Background
In recent years, many MAV failures of micro-drones have occurred; for example, madonna dickan pigelio Marcel Hirscher (austria world cup alpine ski racer) avoids situations of being hit by drones in the alpine torrent whirling game held in italy, and therefore these faults not only bring about the risk of damage to expensive airborne equipment and drones themselves, but also threaten the health and even life of people.
The most common multi-rotor aircraft design is the quad-rotor aircraft. If one of the engines is damaged, the aircraft will fail as a whole and fall. Currently, to address this problem, the number of multiple rotor engines is doubled or even doubled, which, while increasing flexibility and reducing flight time, significantly increases the weight and cost of the aircraft.
Disclosure of Invention
The invention provides a deformable four-rotor aircraft with high fault-tolerant rate and a control method, which can solve the problem of damage to people or objects when the four-rotor aircraft fails and falls, and the problem of how to reduce the failure loss of the aircraft, and can continuously complete the flight task when a small number of rotors fail.
The invention adopts the following technical scheme.
A deformable four-rotor aircraft with high fault tolerance rate is disclosed, wherein the number of rotors of the aircraft is not less than four, and the rotors are all arranged at the horn of the aircraft; the horn comprises a first joint and a second joint; the starting end of the first joint is fixed at the fuselage of the aircraft, and the first joint is connected with the starting end of the second joint through a first rotating mechanism which can horizontally rotate relative to the horizontal plane of the fuselage, so that the second joint can horizontally rotate relative to the horizontal plane of the fuselage; the second joint is connected with the rotor wing of the horn through a second rotating mechanism which can vertically rotate relative to the horizontal plane of the fuselage, so that the rotor wing can vertically rotate relative to the horizontal plane of the fuselage in the direction; the rotor may provide lift to the aircraft by forward or reverse rotation.
The number of the rotors of the aircraft is four; the aircraft comprises a flight control module and an attitude sensor, when the aircraft is in a flight state, if the lift failure state occurs to less than three rotors, the aircraft stops the failed rotors in the failure state, and the lift loss and the torque loss of the aircraft are compensated by adjusting the orientation, the rotating speed or the position of the working rotors still in a normal state, so that the aircraft recovers a stable flight attitude.
When the number of the rotors in the lift failure state is one, the aircraft is in the single-rotor failure state, the aircraft stops the failed rotors in the single-rotor failure state, the first joints of the two adjacent booms of the failed rotors drive the second joints to horizontally swing towards the failed rotors, the working rotors at the two booms are close to the failed rotors to compensate lift loss and torque loss of the aircraft, and the fuselage is in the horizontal state at the moment.
When the number of the rotors in the lift failure state is two, the aircraft is in a double-rotor failure state, and the aircraft stops the failed rotors in the double-rotor failure state;
when the number of the rotors in the lift failure state is three, the aircraft is in a three-rotor failure state, the aircraft stops the failed rotors in the three-rotor failure state,
when the aircraft is in a double-rotor failure state or a triple-rotor failure state, the aircraft enables the first joint and the second joint of the horn where the working rotor is located to rotate, the aircraft body is driven to swing downwards by taking the working rotor as a suspension point, and the aircraft is converted into an upright state, and when the aircraft is in the upright state, the working rotor is located at the top of the aircraft.
When the aircraft is in a vertical state and no heavy object is carried, the aircraft body of the aircraft is in a vertical state;
when the aircraft is in the vertical state and a heavy object is hung below the aircraft body, the aircraft body of the aircraft is in the inclined state, so that the mass center of the aircraft carrying the heavy object is located below the working rotor wing.
The rotor of aircraft encircles the even setting of aircraft fuselage, and the second joint vertical rotation of each horn makes each rotor be located the fuselage top, and its driven air current when flowing in order to reduce aircraft frame torrent to fuselage outside below, the aircraft is in low torrent flight state.
The rotor of aircraft encircles the aircraft fuselage and evenly sets up, and when the second joint vertical rotation of each horn made each rotor be located the fuselage below and when the antiport provided lift, the aircraft was in the mode of reversing flight.
A control method for deformable four-rotor aircraft with high fault tolerance rate is disclosed, wherein the rotors of the aircraft are driven by motors, the reason of lift failure of the rotors is motor failure, when the aircraft has rotor failure, the motor connected with the failed rotors is a failure motor, and the motor connected with the working rotors is a thrust motor, and the control method comprises the following steps,
the method A comprises the steps that under the condition that one rotor of a four-rotor aircraft fails, in order to continue to keep stable flight and recover the original flight attitude of the aircraft to stabilize the coordinate of the aircraft, the aircraft is controlled by compensating the position of a mass center, namely, a new flight mode consisting of three thrust motors is formed by moving two adjacent motors of a fault motor and enabling the two motors to be close to the fault motor; the compensation torque required by the aircraft to be stabilized is generated by the aid of the propellers of the two thrust motors in the opposite directions to the fault motor, the two thrust motor propellers control the rotation angles of the propellers through the servo motors and keep the same rotation direction, and the attitude and the position of the aircraft in three dimensions are completely controlled by the aid of the other three thrust motors;
the method B comprises the steps that under the condition that two rotors in the four-rotor aircraft fail, the positions of the four-rotor aircraft are completely controlled by longitudinally arranging the remaining two thrust motors, the flight attitude of the aircraft is changed at the same time so that the aircraft keeps stable in attitude under the current thrust working condition, and if the aircraft carries heavy objects, the mass center displacement after the flight attitude is changed is compensated by vertically rotating the remaining two thrust motors;
and C, under the condition that three rotors in the four-rotor aircraft fail, the remaining thrust motors are vertically rotated to generate torsional moment to enable the aircraft to stay in the air or slowly descend so as to determine the position of the four-rotor aircraft.
When motor faults occur in the four-rotor aircraft in the flight process, at least two PD controllers are used for compensating unbalanced moment generated by odd propellers and stabilizing the direction of the aircraft, and maintaining the flight function of the aircraft to continue the task without crashing, and the control strategy of the four-rotor aircraft has eight independent input variables, wherein the eight independent input variables comprise the rotating speed of four rotors and the inclination angle of four motors driving the rotors to rotate; failure of either rotor will cause both input variables to disengage from the control strategy; in order to compensate for moment imbalance caused by rotor failure, the speed and tilt angle of the thrust motor that is still operating needs to be controlled separately; the tilt attitude of the fuselage needs to be set at a moment that compensates for the failed rotor;
meanwhile, the aircraft is provided with an airborne measuring sensor for monitoring the flight working condition and sending fault information to the flight control module;
when four rotors of the aircraft are all working rotors, a stable dynamic model can be generated at the aircraft body due to the symmetry of the thrust and the moment of the rotors; the thrust of four rotary wings is respectively F1、F2、F3、F4The moment is M respectively1、M2、M3、M4；
Then when one of the four rotors is a failed rotor, M is enabled2＝0、F2At 0, the dynamic model of the aircraft will experience an asymmetry at the yaw axis and an asymmetry at the pitch plane, expressed as a power equation,
wherein s ψ, c ψ are denoted sin, respectivelyPsi, cos psi; s φ, c φ represent sin φ, cos φ, respectively. s theta, c theta respectively represent sin theta, cos theta; psi, theta and phi are respectively yaw, pitch and roll angles; m is the total weight of the quadrotor, g is the gravitational acceleration, x, y, z is the position of the quadrotor in the system, θi(i ═ 1,2,3,4) is the angle of inclination of the corresponding propeller, C1，C2，C3Is the coefficient of resistance, Fi(i ═ 1,2,3,4) is the force generated by the four rotors as shown in the following equation:
wherein ω isiIs the angular velocity of the ith rotor, KfIs a constant of proportionality.
Similarly, the angular acceleration is determined by the euler equation and expressed as;
wherein M'i(i ═ 1,2,3,4) is the tilt moment that the servomotor attached to the end of the arm causes the tilt angle. The number of the psi, theta,
yaw, pitch and roll angles, respectively;
from the above, the available input to stabilize and control the system described by the equation of force is the angular velocity ω of the three thrust motor working rotors1，ω3，ω4And the angle of inclination theta of all the rotors of the machinei(i ═ 1,2,3,4), where l is the center of gravity of each rotor and aircraftThe distance of (d); i isx，Iy，IzMoment of inertia in the x, y and z directions, respectively; c'1、C′2And C'3Is the coefficient of rotational resistance. Mi(i ═ i, 2,3,4) is determined by the angular velocity ω of the rotoriThe rotor torque generated, e.g.
KmIs a proportionality constant;
at this time, if the fourth rotor of the four-rotor aircraft is inclined at an angle theta4Then, then
So that the aircraft can stably fly in the yaw and pitch planes;
from the above, when one rotor of the aircraft fails, the remaining rotor propeller angular speed increases, and a certain flight altitude can also be maintained, which is expressed by the following formula;
ω′1＝ω1+ω2/3
ω3′＝ω3+ω2/3
ω4′＝ω4+ω2/3
a formula V;
ω2indicating the angular velocity of the second propeller at the moment of failure, which will result in a loss of altitude, but the angular velocities of the three remaining propellers may be increased by ω2A factor of/3 to compensate for losses. Omega'1,ω'3,ω'4New angular velocities are added to each propeller to maintain fly height after failure; furthermore, the new angular velocity must satisfy the equation
Can produce a stable configuration, is formulated as follows
When two of the four rotors are failure rotors, the inclination angle of the thrust motor connected with the working rotor is set to be
Then, beginning to compensate the unbalanced moment after the fault, firstly, returning to the hovering state is necessary, and then, obtaining the direction of the aircraft to a specific pitch or roll angle; in that
The relation between the rotating speed of the traditional four-rotor motor and the deviation of the nominal vector direction of hovering and navigation is described in detail, and is expressed by a formula;
wherein
Is the angular velocity required by the rotor of a single thrust motor. Theta4The inclination angle required to be kept when the thrust motor reaches a stable structure; controlling Δ ω using proportional-derivative lawφ，Δωθ，Δθ4，ΔωfRespectively result in an edge zBThe shaft generates rolling, pitching, yawing and net force/moment, and the calculation formula is
Δωφ＝kp，φ(φdes-φ)+kd，φ(pdes-p)
Δωθ＝kp，θ(θdes-θ)+kd，θ(qdes-q)
Δθ4＝kp，ψ(ψdes-ψ)+kd，ψ(rdes-r)
A formula of nine;
where p, q and r are the components of the angular velocity of the aircraft in the fuselage frame.
Nominal hover state of said aircraft during flight with horizontal attitude of fuselage
Corresponding to a balanced hover configuration having a reference pitch or roll angle; the pitch angle and the roll angle required by the movement of the flight process are shown as the following equations:
θdes，φdesis the pitch and roll angles required to add to the nominal hover state to move the aircraft to the desired trajectory ri，TThe acceleration is commanded and the acceleration is,
calculated by the proportional derivative controller based on the position error:
wherein r isi，ri，T(i ═ 1,2, 3) are the three-dimensional positions of the four rotors and the desired trajectory, respectively; while suspending
Compared with the prior art, the invention has the beneficial effects that:
1. the aircraft can safely fly in crowded conditions.
2. Can be operated under severe environmental conditions (such as natural disasters) threatening human life.
3. Reducing damage losses in the event of failure (e.g., damage to expensive equipment mounted on the drone).
4. If a certain rotor wing fails in the flying process, the rotor wing can deform to keep stable flying, and people or objects are prevented from being directly hit by falling due to failure.
5. The production is cheap.
The technical scheme adopted by the invention reserves the advantages that the four-rotor aircraft is easy to realize the hovering function, can move in all directions and can increase the effective load for lifting and carrying objects, and the four-rotor aircraft is improved, and the specially designed four-rotor aircraft develops a thrust engine and increases the degree of freedom (DOF) of the aircraft; the design of such a multi-rotor aircraft of the present invention allows for the use of only four propeller engine sets in the aircraft design for fault tolerance and improved operability, and such a design adds only slightly to the cost of the antenna and the weight of the aircraft.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
fig. 1 shows a schematic structural diagram of a high fault tolerance deformable quad-rotor aircraft according to the invention.
Figure 2 is a schematic view of a rotor failure mode of the morphing aircraft.
Figure 3 is a schematic diagram of two rotor failure modes of a morphing aircraft.
Figure 4 is a schematic diagram of a morphing aircraft loaded with a heavy load and two rotor failure modes.
Figure 5 is a schematic diagram of three rotor failure modes of a morphing aircraft.
FIG. 6 is a schematic view of a flight pattern with inboard pitch of the morphing aircraft motor.
FIG. 7 is a schematic view of a morphing aircraft motor inverted flight mode.
FIG. 8 is a power model of a quad-rotor aircraft with one rotor failed
In the figure: 1-a machine arm; 2-a rotor wing; 3-a first joint; 4-a second joint; 5-a fuselage; 6-a first rotation mechanism; 7-a second rotation mechanism;
21-failed rotor; 22-working rotor; 32-weight.
Detailed Description
As shown in the figure, the deformable four-rotor aircraft with high fault tolerance rate has no less than four rotors 2, and the rotors are all arranged at the horn 1 of the aircraft; the horn comprises a first joint 3 and a second joint 4; the starting end of the first joint is fixed at a fuselage 5 of the aircraft, and the first joint is connected with the starting end of the second joint through a first rotating mechanism 6 which can horizontally rotate relative to the horizontal plane of the fuselage, so that the second joint can horizontally rotate relative to the horizontal plane of the fuselage; the second joint is connected with the rotor wing of the horn by a second rotating mechanism 7 which can vertically rotate relative to the horizontal plane of the fuselage, so that the rotor wing can vertically rotate relative to the horizontal plane of the fuselage in the direction; the rotor may provide lift to the aircraft by forward or reverse rotation.
The number of the rotors of the aircraft is four; the aircraft comprises a flight control module and an attitude sensor, when the aircraft is in a flight state, if the lift failure state occurs to less than three rotors, the aircraft stops the failed rotor 21 in the failure state, and the lift loss and the torque loss of the aircraft are compensated by adjusting the orientation, the rotating speed or the position of the working rotor 22 still in a normal state, so that the aircraft recovers a stable flight attitude.
When the number of the rotors in the lift failure state is one, the aircraft is in the single-rotor failure state, the aircraft stops the failed rotors in the single-rotor failure state, the first joints of the two adjacent booms of the failed rotors drive the second joints to horizontally swing towards the failed rotors, the working rotors at the two booms are close to the failed rotors to compensate lift loss and torque loss of the aircraft, and the fuselage is in the horizontal state at the moment.
When the number of the rotors in the lift failure state is two, the aircraft is in a double-rotor failure state, and the aircraft stops the failed rotors in the double-rotor failure state;
when the number of the rotors in the lift failure state is three, the aircraft is in a three-rotor failure state, the aircraft stops the failed rotors in the three-rotor failure state,
when the aircraft is in a double-rotor failure state or a triple-rotor failure state, the aircraft enables the first joint and the second joint of the horn where the working rotor is located to rotate, the aircraft body is driven to swing downwards by taking the working rotor as a suspension point, and the aircraft is converted into an upright state, and when the aircraft is in the upright state, the working rotor is located at the top of the aircraft.
When the aircraft is in a vertical state and no heavy object is carried, the aircraft body of the aircraft is in a vertical state;
when the aircraft is in the upright position and a weight 32 is carried beneath the fuselage, the fuselage of the aircraft is tilted so that the center of mass of the aircraft carrying the weight is below the working rotor.
The rotor of aircraft encircles the even setting of aircraft fuselage, and the second joint vertical rotation of each horn makes each rotor be located the fuselage top, and its driven air current when flowing in order to reduce aircraft frame torrent to fuselage outside below, the aircraft is in low torrent flight state.
The rotor of aircraft encircles the aircraft fuselage and evenly sets up, and when the second joint vertical rotation of each horn made each rotor be located the fuselage below and when the antiport provided lift, the aircraft was in the mode of reversing flight.
A control method for deformable four-rotor aircraft with high fault tolerance rate is disclosed, wherein the rotors of the aircraft are driven by motors, the reason of lift failure of the rotors is motor failure, when the aircraft has rotor failure, the motor connected with the failed rotors is a failure motor, and the motor connected with the working rotors is a thrust motor, and the control method comprises the following steps,
the method A comprises the steps that under the condition that one rotor of a four-rotor aircraft fails, in order to continue to keep stable flight and recover the original flight attitude of the aircraft to stabilize the coordinate of the aircraft, the aircraft is controlled by compensating the position of a mass center, namely, a new flight mode consisting of three thrust motors is formed by moving two adjacent motors of a fault motor and enabling the two motors to be close to the fault motor; the compensation torque required by the aircraft to be stabilized is generated by the aid of the propellers of the two thrust motors in the opposite directions to the fault motor, the two thrust motor propellers control the rotation angles of the propellers through the servo motors and keep the same rotation direction, and the attitude and the position of the aircraft in three dimensions are completely controlled by the aid of the other three thrust motors;
the method B comprises the steps that under the condition that two rotors in the four-rotor aircraft fail, the positions of the four-rotor aircraft are completely controlled by longitudinally arranging the remaining two thrust motors, the flight attitude of the aircraft is changed at the same time so that the aircraft keeps stable in attitude under the current thrust working condition, and if the aircraft carries heavy objects, the mass center displacement after the flight attitude is changed is compensated by vertically rotating the remaining two thrust motors;
and C, under the condition that three rotors in the four-rotor aircraft fail, the remaining thrust motors are vertically rotated to generate torsional moment to enable the aircraft to stay in the air or slowly descend so as to determine the position of the four-rotor aircraft.
When motor faults occur in the four-rotor aircraft in the flight process, at least two PD controllers are used for compensating unbalanced moment generated by odd propellers and stabilizing the direction of the aircraft, and maintaining the flight function of the aircraft to continue the task without crashing, and the control strategy of the four-rotor aircraft has eight independent input variables, wherein the eight independent input variables comprise the rotating speed of four rotors and the inclination angle of four motors driving the rotors to rotate; failure of either rotor will cause both input variables to disengage from the control strategy; in order to compensate for moment imbalance caused by rotor failure, the speed and tilt angle of the thrust motor that is still operating needs to be controlled separately; the tilt attitude of the fuselage needs to be set at a moment that compensates for the failed rotor;
meanwhile, the aircraft is provided with an airborne measuring sensor for monitoring the flight working condition and sending fault information to the flight control module;
when four rotors of the aircraft are all working rotors, a stable dynamic model can be generated at the aircraft body due to the symmetry of the thrust and the moment of the rotors; the thrust of four rotary wings is respectively F1、F2、F3、F4The moment is M respectively1、M2、M3、M4；
Then when one of the four rotors is a failed rotor, M is enabled2＝0、F2At 0, the dynamic model of the aircraft will experience an asymmetry at the yaw axis and an asymmetry at the pitch plane, expressed as a power equation,
wherein s ψ, c ψ are denoted sin ψ, cos ψ, respectively; s φ, c φ represent sin φ, cos φ, respectively. s theta, c theta respectively represent sin theta, cos theta; psi, theta and phi are respectively yaw, pitch and roll angles; m is the total weight of the quadrotor, g is the gravitational acceleration, x, y, z is the position of the quadrotor in the system, θi(i ═ 1,2,3,4) is the angle of inclination of the corresponding propeller, C1，C2，C3Is the coefficient of resistance, Fi(i ═ 1,2,3,4) is the force generated by the four rotors as shown in the following equation:
wherein ω isiIs the angular velocity of the ith rotor, KfIs a constant of proportionality.
Similarly, the angular acceleration is determined by the euler equation and expressed as;
wherein M'i(i ═ 1,2,3,4) is the tilt moment that the servomotor attached to the end of the arm causes the tilt angle. The number of the psi, theta,
yaw, pitch and roll angles, respectively;
from the above, the available input to stabilize and control the system described by the equation of force is the angular velocity ω of the three thrust motor working rotors1，ω3，ω4And the angle of inclination theta of all the rotors of the machinei(i ═ 1,2,3,4), l being the distance of each rotor from the aircraft's center of gravity; i isx，Iy，IzMoment of inertia in the x, y and z directions, respectively; c'1、C′2And C'3Is the coefficient of rotational resistance. Mi(i ═ i, 2,3,4) is determined by the angular velocity ω of the rotoriThe rotor torque generated, e.g.
KmIs a proportionality constant;
at this time, if the fourth rotor of the four-rotor aircraft is inclined at an angle theta4Then, then
So that the aircraft can stably fly in the yaw and pitch planes;
from the above, when one rotor of the aircraft fails, the remaining rotor propeller angular speed increases, and a certain flight altitude can also be maintained, which is expressed by the following formula;
ω′1＝ω1+ω2/3
ω3′＝ω3+ω/3
ω4′＝ω4+ω2/3
a formula V;
ω2indicating the angular velocity of the second propeller at the moment of failure, which will result in a loss of altitude, but the angular velocities of the three remaining propellers may be increased by ω2A factor of/3 to compensate for losses. Omega'1,ω'3,ω'4New angular velocities are added to each propeller to maintain fly height after failure; furthermore, the new angular velocity must satisfy the equation
Can produce a stable configuration, is formulated as follows
When two of the four rotors are failure rotors, the inclination angle of the thrust motor connected with the working rotor is set to be
Then, beginning to compensate the unbalanced moment after the fault, firstly, returning to the hovering state is necessary, and then, obtaining the direction of the aircraft to a specific pitch or roll angle; in that
The relation between the rotating speed of the traditional four-rotor motor and the deviation of the nominal vector direction of hovering and navigation is described in detail, and is expressed by a formula;
wherein
Is the angular velocity required by the rotor of a single thrust motor. Theta4The inclination angle required to be kept when the thrust motor reaches a stable structure; controlling Δ ω using proportional-derivative lawφ，Δωθ，Δθ4，ΔωfRespectively result in an edge zBThe shaft generates rolling, pitching, yawing and net force/moment, and the calculation formula is
Δωφ＝kp，φ(φdes-φ)+kd，φ(pdes-p)
Δωθ＝kp，θ(θdes-θ)+kd，θ(qdes-q)
Δθ4＝kp，ψ(ψdes-ψ)+kd，ψ(rdes-r)
A formula of nine;
where p, q and r are the components of the angular velocity of the aircraft in the fuselage frame.
Nominal hover state of said aircraft during flight with horizontal attitude of fuselage
Corresponding to a balanced hover configuration having a reference pitch or roll angle; the pitch angle and the roll angle required by the movement of the flight process are shown as the following equations:
θdes，φdesis the pitch and roll angles required to add to the nominal hover state,to move the aircraft to a desired trajectory ri，TThe acceleration is commanded and the acceleration is,
calculated by the proportional derivative controller based on the position error:
wherein r isi，ri，T(i ═ 1,2, 3) are the three-dimensional positions of the four rotors and the desired trajectory, respectively; while suspending
Example (b):
in this example, the first rotary mechanism, the second rotary mechanism and the rotor of the horn are all driven by servo motors connected to the flight control module.
When the aircraft flies, the aircraft monitors the flying working condition by the onboard measuring sensor, and if the rotor fails, the flying control module adjusts the flying state by controlling the first rotating mechanism, the second rotating mechanism or the servo motor at the rotor.
If only one or two rotors of the aircraft fail, the aircraft can still maintain the flight and carry goods; when three rotors fail, the aircraft can not normally fly and can only maintain a hovering state or slowly land, and at the moment, the landing impact force is small or can be controlled, so that the economic loss caused by the rotor failure can be reduced.
Claims (10)
1. A high fault-tolerant deformable four-rotor aircraft which characterized in that: the number of the rotor wings of the aircraft is not less than four, and the rotor wings are all arranged at the horn of the aircraft; the horn comprises a first joint and a second joint; the starting end of the first joint is fixed at the fuselage of the aircraft, and the first joint is connected with the starting end of the second joint through a first rotating mechanism which can horizontally rotate relative to the horizontal plane of the fuselage, so that the second joint can horizontally rotate relative to the horizontal plane of the fuselage; the second joint is connected with the rotor wing of the horn through a second rotating mechanism which can vertically rotate relative to the horizontal plane of the fuselage, so that the rotor wing can vertically rotate relative to the horizontal plane of the fuselage in the direction; the rotor may provide lift to the aircraft by forward or reverse rotation.
2. A high fault tolerance deformable quad-rotor aircraft according to claim 1, wherein: the number of the rotors of the aircraft is four; the aircraft comprises a flight control module and an attitude sensor, when the aircraft is in a flight state, if the lift failure state occurs to less than three rotors, the aircraft stops the failed rotors in the failure state, and the lift loss and the torque loss of the aircraft are compensated by adjusting the orientation, the rotating speed or the position of the working rotors still in a normal state, so that the aircraft recovers a stable flight attitude.
3. A high fault tolerance deformable quad-rotor aircraft according to claim 2, wherein: when the number of the rotors in the lift failure state is one, the aircraft is in the single-rotor failure state, the aircraft stops the failed rotors in the single-rotor failure state, the first joints of the two adjacent booms of the failed rotors drive the second joints to horizontally swing towards the failed rotors, the working rotors at the two booms are close to the failed rotors to compensate lift loss and torque loss of the aircraft, and the fuselage is in the horizontal state at the moment.
4. A high fault tolerance deformable quad-rotor aircraft according to claim 2, wherein: when the number of the rotors in the lift failure state is two, the aircraft is in a double-rotor failure state, and the aircraft stops the failed rotors in the double-rotor failure state;
when the number of the rotors in the lift failure state is three, the aircraft is in a three-rotor failure state, the aircraft stops the failed rotors in the three-rotor failure state,
when the aircraft is in a double-rotor failure state or a triple-rotor failure state, the aircraft enables the first joint and the second joint of the horn where the working rotor is located to rotate, the aircraft body is driven to swing downwards by taking the working rotor as a suspension point, and the aircraft is converted into an upright state, and when the aircraft is in the upright state, the working rotor is located at the top of the aircraft.
5. A high fault tolerance deformable quad-rotor aircraft according to claim 4, wherein: when the aircraft is in a vertical state and no heavy object is carried, the aircraft body of the aircraft is in a vertical state;
when the aircraft is in the vertical state and a heavy object is hung below the aircraft body, the aircraft body of the aircraft is in the inclined state, so that the mass center of the aircraft carrying the heavy object is located below the working rotor wing.
6. A high fault tolerance deformable quad-rotor aircraft according to claim 2, wherein: the rotor of aircraft encircles the even setting of aircraft fuselage, and the second joint vertical rotation of each horn makes each rotor be located the fuselage top, and its driven air current when flowing in order to reduce aircraft frame torrent to fuselage outside below, the aircraft is in low torrent flight state.
7. A high fault tolerance deformable quad-rotor aircraft according to claim 2, wherein: the rotor of aircraft encircles the aircraft fuselage and evenly sets up, and when the second joint vertical rotation of each horn made each rotor be located the fuselage below and when the antiport provided lift, the aircraft was in the mode of reversing flight.
8. A control method of a deformable four-rotor aircraft with high fault tolerance rate is characterized by comprising the following steps: the aircraft of claim 2, wherein the rotors are driven by motors, the cause of lift failure of the rotors is motor failure, when the aircraft has rotor failure, the motor connected to the failed rotor is a failed motor, and the motor connected to the working rotor is a thrust motor, and the control method comprises the following steps,
the method A comprises the steps that under the condition that one rotor of a four-rotor aircraft fails, in order to continue to keep stable flight and recover the original flight attitude of the aircraft to stabilize the coordinate of the aircraft, the aircraft is controlled by compensating the position of a mass center, namely, a new flight mode consisting of three thrust motors is formed by moving two adjacent motors of a fault motor and enabling the two motors to be close to the fault motor; the compensation torque required by the aircraft to be stabilized is generated by the aid of the propellers of the two thrust motors in the opposite directions to the fault motor, the two thrust motor propellers control the rotation angles of the propellers through the servo motors and keep the same rotation direction, and the attitude and the position of the aircraft in three dimensions are completely controlled by the aid of the other three thrust motors;
the method B comprises the steps that under the condition that two rotors in the four-rotor aircraft fail, the positions of the four-rotor aircraft are completely controlled by longitudinally arranging the remaining two thrust motors, the flight attitude of the aircraft is changed at the same time so that the aircraft keeps stable in attitude under the current thrust working condition, and if the aircraft carries heavy objects, the mass center displacement after the flight attitude is changed is compensated by vertically rotating the remaining two thrust motors;
and C, under the condition that three rotors in the four-rotor aircraft fail, the remaining thrust motors are vertically rotated to generate torsional moment to enable the aircraft to stay in the air or slowly descend so as to determine the position of the four-rotor aircraft.
9. The method of claim 8, wherein the method further comprises: when motor faults occur in the four-rotor aircraft in the flight process, at least two PD controllers are used for compensating unbalanced moment generated by odd propellers and stabilizing the direction of the aircraft, and maintaining the flight function of the aircraft to continue the task without crashing, and the control strategy of the four-rotor aircraft has eight independent input variables, wherein the eight independent input variables comprise the rotating speed of four rotors and the inclination angle of four motors driving the rotors to rotate; failure of either rotor will cause both input variables to disengage from the control strategy; in order to compensate for moment imbalance caused by rotor failure, the speed and tilt angle of the thrust motor that is still operating needs to be controlled separately; the tilt attitude of the fuselage needs to be set at a moment that compensates for the failed rotor;
meanwhile, the aircraft is provided with an airborne measuring sensor for monitoring the flight working condition and sending fault information to the flight control module;
when four rotors of the aircraft are all working rotors, a stable dynamic model can be generated at the aircraft body due to the symmetry of the thrust and the moment of the rotors; the thrust of four rotary wings is respectively F1、F2、F3、F4The moment is M respectively1、M2、M3、M4；
Then when one of the four rotors is a failed rotor, M is enabled2＝0、F2At 0, the dynamic model of the aircraft will experience an asymmetry at the yaw axis and an asymmetry at the pitch plane, expressed as a power equation,
wherein s ψ, c ψ are denoted sin ψ, cos ψ, respectively; s φ, c φ represent sin φ, cos φ, respectively. s theta, c theta respectively represent sin theta, cos theta; psi, theta and phi are respectively yaw, pitch and roll angles; m is the total weight of the quadrotor, g is the gravitational acceleration, x, y, z is the position of the quadrotor in the system, θi(i ═ 1,2,3,4) is the angle of inclination of the corresponding propeller, C1，C2，C3Is the coefficient of resistance, Fi(i ═ 1,2,3,4) is the force generated by the four rotors as shown in the following equation:
wherein ω isiIs the angular velocity of the ith rotor, KfIs a constant of proportionality.
Similarly, the angular acceleration is determined by the euler equation and expressed as;
wherein M'i(i ═ 1,2,3,4) is the tilt moment that the servomotor attached to the end of the arm causes the tilt angle. The number of the psi, theta,
yaw, pitch and roll angles, respectively;
from the above, the available input to stabilize and control the system described by the equation of force is the angular velocity ω of the three thrust motor working rotors1，ω3，ω4And the angle of inclination theta of all the rotors of the machinei(i ═ 1,2,3,4), l being the distance of each rotor from the aircraft's center of gravity; i isx，Iy，IzMoment of inertia in the x, y and z directions, respectively; c'1、C′2And C'3Is the coefficient of rotational resistance. Mi(i ═ i, 2,3,4) is determined by the angular velocity ω of the rotoriThe rotor torque generated, e.g.
KmIs a proportionality constant;
at this time, if the fourth rotor of the four-rotor aircraft is inclined at an angle theta4Then, then
So that the aircraft can stably fly in the yaw and pitch planes;
from the above, when one rotor of the aircraft fails, the remaining rotor propeller angular speed increases, and a certain flight altitude can also be maintained, which is expressed by the following formula;
ω1′＝ω1+ω2/3
ω3′＝ω3+ω2/3
ω4′＝ω4+ω2/3
a formula V;
ω2indicating the angular velocity of the second propeller at the moment of failure, which will result in a loss of altitude, but the angular velocities of the three remaining propellers may be increased by ω2A factor of/3 to compensate for losses. Omega'1,ω′3,ω′4New angular velocities are added to each propeller to maintain fly height after failure; furthermore, the new angular velocity must satisfy the equation
Can produce a stable configuration, is formulated as follows
When two of the four rotors are failure rotors, the inclination angle of the thrust motor connected with the working rotor is set to be
Then, beginning to compensate the unbalanced moment after the fault, firstly, returning to the hovering state is necessary, and then, obtaining the direction of the aircraft to a specific pitch or roll angle; in that
The relation between the rotating speed of the traditional four-rotor motor and the deviation of the nominal vector direction of hovering and navigation is described in detail, and is expressed by a formula;
wherein
Is the angular velocity required by the rotor of a single thrust motor. Theta4The inclination angle required to be kept when the thrust motor reaches a stable structure; controlling Δ ω using proportional-derivative lawφ，Δωθ，Δθ4，ΔωfRespectively result in an edge zBThe shaft generates rolling, pitching, yawing and net force/moment, and the calculation formula is
Δωφ＝kp，φ(φdes-φ)+kd，φ(pdes-p)
Δωθ＝kp，θ(θdes-θ)+kd，θ(qdes-q)
Δθ4＝kp，ψ(ψdes-ψ)+kd，ψ(rdes-r)
A formula of nine;
where p, q and r are the components of the angular velocity of the aircraft in the fuselage frame.
10. According to claim 8The control method of the deformable four-rotor aircraft with high fault tolerance rate is characterized by comprising the following steps: the aircraft is in a nominal hover state (phi-theta-0, psi-psi) during flight in the horizontal attitude of the fuselageT，
) Corresponding to a balanced hover configuration having a reference pitch or roll angle; the pitch angle and the roll angle required by the movement of the flight process are shown as the following equations:
θdes，φdesis the pitch and roll angles required to add to the nominal hover state to move the aircraft to the desired trajectory ri，TThe acceleration is commanded and the acceleration is,
calculated by the proportional derivative controller based on the position error:
wherein r isi，ri，T(i ═ 1,2, 3) are the three-dimensional positions of the four rotors and the desired trajectory, respectively; while suspending
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