CN112208759A - Eight-rotor aircraft with wind disturbance resistant tiltable rotor and control method - Google Patents
Eight-rotor aircraft with wind disturbance resistant tiltable rotor and control method Download PDFInfo
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- CN112208759A CN112208759A CN202011251464.1A CN202011251464A CN112208759A CN 112208759 A CN112208759 A CN 112208759A CN 202011251464 A CN202011251464 A CN 202011251464A CN 112208759 A CN112208759 A CN 112208759A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/52—Tilting of rotor bodily relative to fuselage
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/04—Helicopters
- B64C27/08—Helicopters with two or more rotors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
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Abstract
The invention provides an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor and a control method thereof, wherein the rotor of the aircraft comprises the tiltable rotor; when the aircraft works in a wind disturbance resisting working condition to optimize wind resistance performance, the plane of the rotor wing of the tiltable rotor wing forms an inclination angle relative to the horizontal plane of the aircraft body; the tiltable rotor wing is driven by a motor with multiple degrees of freedom; the multi-degree-of-freedom motor can adjust the inclination angle of the rotor so as to enable the rotor wing of the tiltable rotor wing to incline relative to the horizontal plane of the aircraft body; the aircraft is provided with an airborne wind speed detection device and a flight control module capable of controlling the inclination posture of the rotor wing; when the aircraft works in a low wind speed environment, the rotor wing driving shaft of the tiltable rotor wing is vertical to the horizontal plane of the aircraft body, so that the aircraft runs in the form and working condition of a common eight-axis rotor wing aircraft to save electric power; the invention can optimize the wind-disturbance resistance of the multi-rotor aircraft.
Description
Technical Field
The invention relates to the technical field of multi-rotor aircrafts, in particular to an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor and a control method.
Background
Multi-rotor aircrafts are widely used in various fields such as aerial photography and surveying. Just a while ago, researchers have proposed its application to spray or canopy sampling. These applications require the aircraft to be close to objects in the natural environment, which makes accurate positioning extremely important. However, aircraft operation in such environments is challenging due to the wide bandwidth and unpredictability of turbulent disturbances of wind farms. Standard multi-rotor configurations, i.e. rotors oriented along a common axis, can only maintain horizontal position through attitude changes, not perfectly suited for interference rejection scenarios. And in a complex wind field, the change of the attitude of the aircraft can cause serious consequences such as the crash of the aircraft. It is therefore desirable to design a rotorcraft that can operate in a field environment while maintaining endurance and accurate operation, and it is to this end that the present invention is directed.
Disclosure of Invention
The invention provides an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor and a control method, which can optimize the wind-disturbance resistance of a multi-rotor aircraft.
The invention adopts the following technical scheme.
An eight-rotor aircraft with a tiltable rotor that resists wind disturbance, the aircraft having a tiltable rotor in its rotor; when the aircraft works in the wind disturbance resisting working condition to optimize the wind resistance performance, the plane of the rotor of the tiltable rotor wing is inclined angle relative to the horizontal plane of the aircraft body.
The tiltable rotor wing is driven by a motor with multiple degrees of freedom; the multiple degree of freedom motor may adjust the rotor tilt angle to tilt the rotor of the tiltable rotor relative to the aircraft fuselage horizontal plane.
The aircraft is provided with an airborne wind speed detection device and a flight control module capable of controlling the inclination posture of the rotor wing; when the aircraft works in a low wind speed environment, the rotor driving shaft of the tiltable rotor is perpendicular to the horizontal plane of the aircraft body, so that the aircraft runs in the form and working condition of a common eight-axis rotor aircraft to save electric power.
The multi-degree-of-freedom motor is a three-degree-of-freedom motor with a rotor having degrees of freedom in three directions; the degrees of freedom in the three directions are that the rotor tilting motion of the X-axis and the Y-axis is carried out at a single action point to drive the rotor tilting, and the rotor rotating motion of the Z-axis is also carried out at the action point to drive the rotor rotating.
The three-degree-of-freedom motor comprises a direct-current brushless actuator for driving a rotor of the three-degree-of-freedom motor to rotate, a tiltable internal frame and an external frame fixed at a machine body;
the rotor of the three-degree-of-freedom motor is arranged at the internal frame;
the external frame is provided with a voice coil actuator and a torque actuator; and the output shafts of the voice coil actuator rotor and the torque actuator rotor are connected with the internal frame through universal joints to drive the internal frame to incline according to a required angle, so that the rotor of the three-degree-of-freedom motor is inclined to a required posture.
The torque actuator is driven by a permanent magnet motor, and the permanent magnet motor comprises a tilting actuator rotor, a tilting actuator stator and a winding coil; the winding coil at the stator of the tilt actuator may operate on single phase or dual phase electricity; when the size needs to be reduced to facilitate the inclination, the permanent magnet motor is powered by single-phase electricity;
a micro sensor capable of monitoring the inclination process of the inner frame is arranged at the inner frame; the micro-sensor comprises an inertial measurement unit, an encoder and a resolver; the maximum inclination angle of the inner frame is 45 degrees; the direct current brushless actuator drives the rotor driving shaft of the tiltable rotor by two rotor structures, and the direct current brushless actuator has a double air gap structure capable of reducing iron loss when the two rotor structures operate at synchronous speed.
The voice coil actuator comprises a permanent magnet, a voice coil actuator stator, a coil frame fixed with a coil and a rotor back yoke of a voice coil actuator rotor; the voice coil actuator determines an x axis in the direction of a north pole and a y axis in the direction of a south pole according to the magnetization direction of the permanent magnet;
the stator and the coil frame of the voice coil actuator are connected on a support plate at the bottom of the voice coil actuator to form a bottom structure, and the rotor back yoke and the permanent magnet are connected on a support at the top of the voice coil actuator to form a top structure; the top structure is connected with an internal frame of the three-degree-of-freedom motor to drive the three-degree-of-freedom motor to incline;
the top structure and the bottom structure are connected through a universal joint, and when the top structure inclines relative to the bottom structure, the direction of a magnetic field of the permanent magnet is changed; the voice coil actuator generates a torque proportional to a current of the coil at the bobbin using a magnetic field provided by the permanent magnet;
the voice coil actuator is a motor driving structure without a gear and a tooth gap; the motor driving structure can provide constant high torque which has no hysteresis loss and is easy to control, and can realize balance and accurate rotor positioning;
when the top structure is at an initial angle, if current flows through the coil, the voice coil actuator generates negative torque according to a polarization mode and gravity, and when power supply current is interrupted, the top structure returns to a low-power working condition with an angle of 0 degrees through restoring force;
when the inclination angle of the top structure is changed, the coil inductance of the voice coil actuator is changed;
the rotor back yoke is provided with an extension structure including a tilt operation range to change self-resistance with a tilt angle; a magnetic core is arranged between the north pole and the south pole of the permanent magnet so that the rotor back yoke shows minimum basic dynamic stability;
the rotor back yoke is tapered towards the end part so as to enable the opening of the rotor of the voice coil actuator with the salient pole to be maximum and the inductance to be minimum;
the magnetic flux and the magnetic resistance generated by the permanent magnet in the coil are related to the size of the inclination angle of the tiltable rotor so as to realize sensorless control of the voice coil actuator;
when the inclination angle of the tiltable rotor is 0 degrees, the length of an air gap between the rotor and the stator iron core of the voice coil actuator is minimum so as to increase the magnetic flux; when the tilt angle of the tiltable rotor is 20 °, the length between the rotor and the stator core is maximized to reduce the magnetic flux.
A control method of an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor is provided, wherein eight rotors of the aircraft are all tiltable rotors; the driving mode of the aircraft rotor comprises a conventional driving mode, an intermediate driving mode and a tilting driving mode;
when the aircraft rotor wing works in a conventional driving mode, the rotor wing driving shaft of each tiltable rotor wing is vertical to the horizontal plane of the airframe so as to provide the longest endurance time;
when the rotor wings of the aircraft work in the middle driving mode, the two pairs of tiltable rotor wings are converted into tilting postures for driving, and the rotor wing driving shafts of the other tiltable rotor wings are kept vertical to the horizontal plane of the aircraft body according to the conventional driving mode, so that the wind disturbance resistance of the aircraft is improved, and the endurance time of the aircraft is considered;
when the rotors of the aircraft work in a tilt driving mode, the rotor driving shafts of all the tiltable rotors keep the same tilt angle with the horizontal plane of the airframe to work, so that the aircraft has the best wind-disturbance resistance and space holding capacity.
The rotor of the tiltable rotor can perform uniform-speed tilt adjustment in a range of 0-31 degrees relative to the horizontal plane of the fuselage, and the tilt adjustment is completed within 5 seconds;
the flight control module of the aircraft acquires wind speed information in the environment in real time by using an airborne wind speed detection device, and automatically adjusts the driving mode of the tiltable rotor wing according to the wind speed information; when the driving mode of the tiltable rotor wing is automatically adjusted by the flight control module,
if the wind speed is 0-2.5m/s, the rotor wing of the aircraft works in a conventional driving mode;
if the wind speed is 2.5-5m/s, or the instantaneous wind speed is more than 5m/s only occasionally under the wind speed environment, the rotor wing of the aircraft works in a middle driving mode;
if the wind speed is more than 5m/s, the rotor wing of the aircraft works in a tilt driving mode.
The aircraft model of the aircraft is a two-dimensional rigid body model;
the equation of motion of the aircraft is
Wherein, T, THAnd M is the vertical thrust, horizontal thrust and resulting moment, respectively; aerodynamic forces and moments generated by multi-rotor aircraft frames
And MareoRepresents;
the forces and moments generated by the rotor of the electric machine driving the rotor are formulated as
Wherein, CTIs the rotor thrust constant, ωiIs the rotational speed of the rotor. Note that the factor 2 in equation two is used to illustrate xb-zbPlanar symmetry;
the equation of motion of the rotor is formulated as
Wherein, V0Is the nominal voltage of the motor, I0Is no-load current, R is motor resistance, KVIs the motor speed constant, cτIs the rotor aerodynamic torque constant, JrotorIs the rotor inertia. ViIs the input voltage of motor i, for the power control of the aircraft, there is the following formula:
wherein VTIs a voltage command for controlling the overall thrust, and VMGenerating a pitching moment;
for horizontal thrust control of an aircraft, the input voltage of the motor is formulated as
Wherein
Is used for generating an edge xbA voltage command for shaft thrust; v1And V4The additional term tan (22.5 deg.) contained in (A) is used for counteracting
A pitching moment generated when the voltage command generates a horizontal thrust component;
the aerodynamic force and moment model acting on the rotor craft is obtained through a wind tunnel test of a full-size quadrotor; extrapolating the sizes of the aircraft and the rotors and the number of the rotors, and calculating the aerodynamic force and the moment of the rotor aircraft; the aerodynamic forces and moments are given by:
where ρ is the density of air, ApropIs the swept-back area of the propeller, AUAVIs the effective area of the wing or wings,
is the average speed of all rotors, nrotorIs the number of rotors;
the aircraft in the model is controlled by a perfect controller, so that the apparent wind speed and the attack angle of the aircraft are not influenced by the motion of the aircraft;
the aerodynamic coefficient model of the rotorcraft is suitable for an attack angle range of-180 DEG to 180 DEG, and is obtained by fitting a Fourier series to coefficients of experimental tests by using least square optimization and is expressed by a formula;
where λ is the tip speed ratio, given by:
parameter A1And A2Given by:
for the sake of symmetry, for simulation
And
the function of (a) must be an odd function with respect to α ═ 90 °, +90 °;
when calculating
Let us assume that the rotorcraft is about xb-ybPlane symmetry, i.e. meaning
And
the function of (a) must also be about 0 °;
the above-mentioned
And
the value of (a) must be zero when α is-90 °, +90 °;
for and
relative aerodynamic coefficient, assuming rotor flightAbout yb-zbAnd xb-zbIn the case of planar symmetry, the function used to model these coefficients must be an even function with α ═ 90 °, +90 °.
The aircraft provided by the invention runs in a state of a common eight-axis rotor aircraft in low wind speed occasions such as indoors and the like, so that the energy consumption is reduced. In a turbulent wind field or when a user needs, the pairs of tiltable rotors can be automatically or manually set to the tilting state by the three-degree-of-freedom rotor motor. This makes many rotor crafts need not to change the gesture, just can produce horizontal thrust, has improved flight stability. By combining these two rotor drive methods, the rotorcraft retention in wind disturbances can be improved while reducing high frequency attitude corrections. This allows the aircraft to be operated in a field environment with improved capabilities.
The aircraft of the present invention provides a fixed tiltrotor configuration that has improved responsiveness because the aircraft does not require attitude changes to produce horizontal thrust, and simplifies conventional controller designs because a minimum of one pair of rotors are required to tilt about orthogonal axes.
At a target wind speed, the present tiltrotor provides a bandwidth that is an order of magnitude higher than that provided by conventional drive styles and does not change as the wind speed changes. The bandwidth of both driving methods can be compared to the typical turbulence spectrum expected to be encountered in operation. Tilting the rotor allows additional disturbance mitigation at higher wind speed conditions. The lower amplitude of the disturbance at higher frequencies means that the lower horizontal thrust produced by the inclined rotor drive is negligible compared to a conventional drive rotor and is effective against wind disturbances. The invention can effectively improve the space position holding performance and reduce the high-frequency attitude change by combining the conventional rotor wing and the tiltable rotor wing.
The present invention allows a user to set a default rotor drive scheme with priority over different wind speeds; that is, the user can set any one of the driving forms of the rotor in any wind speed scene (for example, the rotor is set to be a tilting driving form in the wind speed of 0-5m/s to obtain better wind disturbance resisting performance).
Compared with the prior art, the invention has the beneficial effects that: the number of the inclined rotary wings can be manually or automatically adjusted according to the wind speed so as to improve the hovering capacity and the wind disturbance resistance in the space. The other rotors operate in a conventional rotor-driven manner to reduce power consumption.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1a is a schematic top view of an aircraft according to the present invention;
FIG. 1b is a schematic forward view of the aircraft of the present invention;
FIG. 2 is a schematic view of the tilting action of a pair of tiltable rotors;
FIG. 3 is a schematic representation of a model free body of the aircraft of the present invention;
FIG. 4 is a schematic top view of the three-degree-of-freedom motor according to the present invention;
FIG. 5 is an internal schematic view of the three-degree-of-freedom motor according to the present invention;
FIG. 6 is a schematic structural diagram of a DC brushless actuator according to the present invention;
FIG. 7 is a schematic structural view of a voice coil actuator according to the present invention;
FIG. 8 is a schematic diagram of the operation of the voice coil actuator of the present invention;
FIG. 9a is a schematic view of a portion of a voice coil actuator at a high inductance tilt angle;
FIG. 9b is a partial schematic view of a voice coil actuator at a low inductance tilt angle;
FIG. 10 is a schematic diagram of a torque actuator;
in the figure: 1-tiltable rotor; 2-a fuselage; 3-an outer frame; 4-an internal frame; 5-a direct current brushless actuator; 6-double air gap structure; 7-torque actuator; 8-rotor drive shaft; 9-a voice coil actuator; 10-rotor structure of the DC brushless actuator; 11-a universal joint; 12-a microsensor; 13-a permanent magnet; 14-rotor back yoke; 15-a coil; 16-a coil holder; 17-a support plate; 18-a voice coil actuator stator; 19-tilt actuator rotor; 20-tilt actuator stator; 21-winding the coil.
Detailed Description
As shown in the figure, an eight-rotor aircraft with a tiltable rotor capable of resisting wind disturbance comprises a tiltable rotor 1 in a rotor of the aircraft; when the aircraft is operated in a wind-resistant mode to optimize wind resistance, the plane of the rotor of the tiltable rotor is inclined relative to the horizontal plane of the aircraft body 2.
The tiltable rotor wing is driven by a motor with multiple degrees of freedom; the multiple degree of freedom motor may adjust the rotor tilt angle to tilt the rotor of the tiltable rotor relative to the aircraft fuselage horizontal plane.
The aircraft is provided with an airborne wind speed detection device and a flight control module capable of controlling the inclination posture of the rotor wing; when the aircraft works in a low wind speed environment, the rotor driving shaft of the tiltable rotor is perpendicular to the horizontal plane of the aircraft body, so that the aircraft runs in the form and working condition of a common eight-axis rotor aircraft to save electric power.
The multi-degree-of-freedom motor is a three-degree-of-freedom motor with a rotor having degrees of freedom in three directions; the degrees of freedom in the three directions are that the rotor tilting motion of the X-axis and the Y-axis is carried out at a single action point to drive the rotor tilting, and the rotor rotating motion of the Z-axis is also carried out at the action point to drive the rotor rotating.
The three-degree-of-freedom motor comprises a direct current brushless actuator 5 for driving a rotor of the three-degree-of-freedom motor to rotate, a tiltable inner frame 4 and an outer frame 3 fixed at a machine body;
the rotor of the three-degree-of-freedom motor is arranged at the internal frame;
the external frame is provided with a voice coil actuator 9 and a moment actuator 7; the output shafts of the voice coil actuator rotor and the torque actuator rotor are connected with the internal frame through a universal joint 11, and the internal frame is driven to incline according to a required angle, so that the rotor of the three-degree-of-freedom motor is inclined to a required posture.
The torque actuator is driven by a permanent magnet motor comprising a tilt actuator rotor 19, a tilt actuator stator 20 and a winding coil 21; the winding coil at the stator of the tilt actuator may operate on single phase or dual phase electricity; when the size needs to be reduced to facilitate the inclination, the permanent magnet motor is powered by single-phase electricity;
a microsensor 12 capable of monitoring the inclination process of the inner frame is arranged at the inner frame; the micro-sensor comprises an inertial measurement unit, an encoder and a resolver; the maximum inclination angle of the inner frame is 45 degrees;
the brushless dc actuator drives a rotor drive shaft 8 of a tiltable rotor with two rotor structures 10, and has a dual air gap structure 6 that reduces the iron loss when the two rotor structures are operated at synchronous speed.
The voice coil actuator comprises a permanent magnet 13, a voice coil actuator stator 18, a coil frame 16 fixed with a coil 15 and a rotor back yoke 14 of a voice coil actuator rotor; the voice coil actuator determines an x axis in the direction of a north pole and a y axis in the direction of a south pole according to the magnetization direction of the permanent magnet;
the stator and coil former of the voice coil actuator are connected on the support plate 17 at the bottom of the voice coil actuator to form a bottom structure, and the rotor back yoke and permanent magnet are connected on the support at the top of the voice coil actuator to form a top structure; the top structure is connected with an internal frame of the three-degree-of-freedom motor to drive the three-degree-of-freedom motor to incline;
the top structure and the bottom structure are connected through a universal joint, and when the top structure inclines relative to the bottom structure, the direction of a magnetic field of the permanent magnet is changed; the voice coil actuator generates a torque proportional to a current of the coil at the bobbin using a magnetic field provided by the permanent magnet;
the voice coil actuator is a motor driving structure without a gear and a tooth gap; the motor driving structure can provide constant high torque which has no hysteresis loss and is easy to control, and can realize balance and accurate rotor positioning;
when the top structure is at an initial angle, if current flows through the coil, the voice coil actuator generates negative torque according to a polarization mode and gravity, and when power supply current is interrupted, the top structure returns to a low-power working condition with an angle of 0 degrees through restoring force;
when the inclination angle of the top structure is changed, the coil inductance of the voice coil actuator is changed;
the rotor back yoke is provided with an extension structure including a tilt operation range to change self-resistance with a tilt angle; a magnetic core is arranged between the north pole and the south pole of the permanent magnet so that the rotor back yoke shows minimum basic dynamic stability;
the rotor back yoke is tapered towards the end part so as to enable the opening of the rotor of the voice coil actuator with the salient pole to be maximum and the inductance to be minimum;
the magnetic flux and the magnetic resistance generated by the permanent magnet in the coil are related to the size of the inclination angle of the tiltable rotor so as to realize sensorless control of the voice coil actuator;
when the inclination angle of the tiltable rotor is 0 degrees, the length of an air gap between the rotor and the stator iron core of the voice coil actuator is minimum so as to increase the magnetic flux; when the tilt angle of the tiltable rotor is 20 °, the length between the rotor and the stator core is maximized to reduce the magnetic flux.
A control method of an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor is provided, wherein eight rotors of the aircraft are all tiltable rotors; the driving mode of the aircraft rotor comprises a conventional driving mode, an intermediate driving mode and a tilting driving mode;
when the aircraft rotor works in a conventional driving mode, the rotor driving shaft 8 of each tiltable rotor is vertical to the horizontal plane of the airframe so as to provide the longest endurance time;
when the rotor wings of the aircraft work in the middle driving mode, the two pairs of tiltable rotor wings are converted into tilting postures for driving, and the rotor wing driving shafts of the other tiltable rotor wings are kept vertical to the horizontal plane of the aircraft body according to the conventional driving mode, so that the wind disturbance resistance of the aircraft is improved, and the endurance time of the aircraft is considered;
when the rotors of the aircraft work in a tilt driving mode, the rotor driving shafts of all the tiltable rotors keep the same tilt angle with the horizontal plane of the airframe to work, so that the aircraft has the best wind-disturbance resistance and space holding capacity.
The rotor of the tiltable rotor can perform uniform-speed tilt adjustment in a range of 0-31 degrees relative to the horizontal plane of the fuselage, and the tilt adjustment is completed within 5 seconds;
the flight control module of the aircraft acquires wind speed information in the environment in real time by using an airborne wind speed detection device, and automatically adjusts the driving mode of the tiltable rotor wing according to the wind speed information; when the driving mode of the tiltable rotor wing is automatically adjusted by the flight control module,
if the wind speed is 0-2.5m/s, the rotor wing of the aircraft works in a conventional driving mode;
if the wind speed is 2.5-5m/s, or the instantaneous wind speed is more than 5m/s only occasionally under the wind speed environment, the rotor wing of the aircraft works in a middle driving mode;
if the wind speed is more than 5m/s, the rotor wing of the aircraft works in a tilt driving mode.
The aircraft model of the aircraft is a two-dimensional rigid body model;
the equation of motion of the aircraft is
Wherein, T, THAnd M is the vertical thrust, horizontal thrust and resulting moment, respectively; aerodynamic forces and moments generated by multi-rotor aircraft frames
And MareoRepresents;
the forces and moments generated by the rotor of the electric machine driving the rotor are formulated as
Wherein, CTIs the rotor thrust constant, ωiIs the rotational speed of the rotor. Note that the factor 2 in equation two is used to illustrate xb-zbPlanar symmetry;
the equation of motion of the rotor is formulated as
Wherein, V0Is the nominal voltage of the motor, I0Is no-load current, R is motor resistance, KVIs the motor speed constant, cτIs the rotor aerodynamic torque constant, JrotorIs the rotor inertia. ViIs the input voltage of motor i, for the power control of the aircraft, there is the following formula:
wherein VTIs a voltage command for controlling the overall thrust, and VMGenerating a pitching moment;
for horizontal thrust control of an aircraft, the input voltage of the motor is formulated as
Wherein
Is used for generating an edge xbA voltage command for shaft thrust; v1And V4The additional term tan (22.5 deg.) contained in (A) is used for counteracting
A pitching moment generated when the voltage command generates a horizontal thrust component;
the aerodynamic force and moment model acting on the rotor craft is obtained through a wind tunnel test of a full-size quadrotor; extrapolating the sizes of the aircraft and the rotors and the number of the rotors, and calculating the aerodynamic force and the moment of the rotor aircraft; the aerodynamic forces and moments are given by:
where ρ is the density of air, ApropIs the swept-back area of the propeller, AUAVIs the effective area of the wing or wings,
is the average speed of all rotors, nrotorIs the number of rotors;
the aircraft in the model is controlled by a perfect controller, so that the apparent wind speed and the attack angle of the aircraft are not influenced by the motion of the aircraft;
the aerodynamic coefficient model of the rotorcraft is suitable for an attack angle range of-180 DEG to 180 DEG, and is obtained by fitting a Fourier series to coefficients of experimental tests by using least square optimization and is expressed by a formula;
where λ is the tip speed ratio, given by:
parameter A1And A2Given by:
for the sake of symmetry, for simulation
And
the function of (a) must be an odd function with respect to α ═ 90 °, +90 °;
when calculating
Let us assume that the rotorcraft is about xb-ybPlane symmetry, i.e. meaning
And
the function of (a) must also be about 0 °;
the above-mentioned
And
the value of (a) must be zero when α is-90 °, +90 °;
for and
relative aerodynamic coefficient, assuming rotorcraft about yb-zbAnd xb-zbIn the case of planar symmetry, the function used to model these coefficients must be an even function with α ═ 90 °, +90 °.
Example 1:
as shown in fig. 4 and 5. The output rotor of the three-degree-of-freedom motor is positioned in the center of the structure, and the output shaft is directly connected with the rotor wing of the aircraft. The brushless direct current actuator and the torque actuator which are positioned around the output rotor and the voice coil actuator which is positioned right below the output rotor are combined to provide the tilt freedom degrees of the output shaft in the x direction and the y direction. When the three-degree-of-freedom motor is inclined, the output rotor can be inclined along with the inner frame, and the maximum inclination angle is 45 degrees. The control of the tilting process depends on built-in micro sensors (including inertial measurement units, encoders and resolvers), which makes it possible to perform a 31 ° tilt or return of the rotor within 5s, and also makes it possible to switch the rotor drive scheme for an eight-axis rotorcraft. In addition, the voice coil actuator right below the internal frame can also provide a restoring moment and a magnetic field environment for the output rotor.
Example 2:
aircraft rotors have three drive forms: the conventional drive form, i.e. eight axes of the rotor are perpendicular to the horizontal plane. This rotor drive scheme is the longest-lived but provides the most limited wind-disturbance rejection. ② an intermediate driving form. Two pairs of rotors are driven in tilt (tilt angle 31 °), the remaining two pairs of rotors are driven in a conventional manner, with rotors of different drive schemes arranged adjacent to each other. It gives consideration to endurance and wind disturbance resistance. If the user does not have additional settings for the aircraft drive profile, the user will default to operating in this manner. And thirdly, a tilt driving mode, namely four pairs of rotors work at a common tilt angle of 31 degrees. The aircraft has the strongest wind disturbance resistance and space retention capacity, and is suitable for the operation of the aircraft under the condition of a complex wind field.
According to the airborne wind speed detection device, the eight-axis rotor aircraft can acquire wind speed information in real time. Under the condition of indoor equal stable wind speed (the wind speed is about 0-2.5m/s), the eight-axis aircraft runs in a conventional driving mode by default; when the wind speed is in a low environment (the wind speed is about 2.5-5m/s, or the accidental instantaneous wind speed is more than 5m/s), the wind power generator is operated in a middle driving mode by default; when in the field where wind speeds are high (wind speeds greater than 5m/s), operating in a tilted fashion by default, it can provide an order of magnitude greater drive bandwidth than conventional drives.
In addition, the user sets a default rotor drive scheme with priority over different wind speeds. The user can set any one of the rotor driving forms under any wind speed scene (for example, the rotor is set to be a tilting driving form under the wind speed of 0-5m/s so as to obtain better wind disturbance resisting performance).
As shown in fig. 2. By means of the three-degree-of-freedom motor, each rotor wing of the eight-axis aircraft can synchronously realize the conversion from a horizontal 0-degree inclined angle position to a 31-degree inclined angle position. For stability reasons, this process will be performed at a constant speed, tilting to a horizontal position or horizontal to a tilted position being achieved within 5 s.
Example 3:
the present invention is designed to be used by a parameter scanning process to select components and design parameters for a non-tiltrotor aircraft for further analysis.
Parameters considered include the combination of motor and propeller (rotor), rotorcraft diameter DUAVBattery capacity, and the tilt angle beta of the rotor when the tilt rotor is in use. The parameter scanning process evaluates a combination of design variables with the goal of finding the most compact and responsive aircraft. A total of 306 engine/propeller combinations were evaluated, with aircraft diameters of 0.5-2.1m and rotor tilt angles of 1-89 deg. (in 2 deg. increments). For designs to be considered viable, they must meet constraints such as carrying a certain payload for a certain time, throttle setting at hover, geometric disturbance conditions, and generating sufficient thrust to mitigate expected drag fluctuations.
The parameter scan produces a series of feasible solutions from which a set of non-dominant solutions is identified using pareto's ordering. I.e. if there is no corresponding compromise in one metric, there is no possibility of any improved solution in a particular metric. After a set of non-leading solutions has been determined, it is desirable to select an appropriate design that provides an appropriate compromise between size and responsiveness.
Finally, an aircraft diameter of 0.5m is selected, the maximum effective load is 1kg, the designed battery capacity is 8500mAh, and the designed endurance time is 20 minutes.
The 31-degree inclination angle of the aircraft is selected because the vertical lift force, the horizontal thrust force, the rotor moment and the endurance time reach a higher value and a higher matching degree.
Claims (10)
1. An eight-rotor aircraft with an anti-wind-disturbance tiltable rotor, characterized in that: the rotor of the aircraft comprises a tiltable rotor; when the aircraft works in the wind disturbance resisting working condition to optimize the wind resistance performance, the plane of the rotor of the tiltable rotor wing is inclined angle relative to the horizontal plane of the aircraft body.
2. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 1, wherein: the tiltable rotor wing is driven by a motor with multiple degrees of freedom; the multiple degree of freedom motor may adjust the rotor tilt angle to tilt the rotor of the tiltable rotor relative to the aircraft fuselage horizontal plane.
3. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 2, wherein: the aircraft is provided with an airborne wind speed detection device and a flight control module capable of controlling the inclination posture of the rotor wing; when the aircraft works in a low wind speed environment, the rotor driving shaft of the tiltable rotor is perpendicular to the horizontal plane of the aircraft body, so that the aircraft runs in the form and working condition of a common eight-axis rotor aircraft to save electric power.
4. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 2, wherein: the multi-degree-of-freedom motor is a three-degree-of-freedom motor with a rotor having degrees of freedom in three directions; the degrees of freedom in the three directions are that the rotor tilting motion of the X-axis and the Y-axis is carried out at a single action point to drive the rotor tilting, and the rotor rotating motion of the Z-axis is also carried out at the action point to drive the rotor rotating.
5. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 4, wherein: the three-degree-of-freedom motor comprises a direct-current brushless actuator for driving a rotor of the three-degree-of-freedom motor to rotate, a tiltable internal frame and an external frame fixed at a machine body;
the rotor of the three-degree-of-freedom motor is arranged at the internal frame;
the external frame is provided with a voice coil actuator and a torque actuator; and the output shafts of the voice coil actuator rotor and the torque actuator rotor are connected with the internal frame through universal joints to drive the internal frame to incline according to a required angle, so that the rotor of the three-degree-of-freedom motor is inclined to a required posture.
6. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 5, wherein: the torque actuator is driven by a permanent magnet motor, and the permanent magnet motor comprises a tilting actuator rotor, a tilting actuator stator and a winding coil; the winding coil at the stator of the tilt actuator may operate on single phase or dual phase electricity; when the size needs to be reduced to facilitate the inclination, the permanent magnet motor is powered by single-phase electricity;
a micro sensor capable of monitoring the inclination process of the inner frame is arranged at the inner frame; the micro-sensor comprises an inertial measurement unit, an encoder and a resolver; the maximum inclination angle of the inner frame is 45 degrees; the direct current brushless actuator drives the rotor driving shaft of the tiltable rotor by two rotor structures, and the direct current brushless actuator has a double air gap structure capable of reducing iron loss when the two rotor structures operate at synchronous speed.
7. An eight-rotor aircraft with wind disturbance resistant tiltable rotor according to claim 6, wherein: the voice coil actuator comprises a permanent magnet, a voice coil actuator stator, a coil frame fixed with a coil and a rotor back yoke of a voice coil actuator rotor; the voice coil actuator determines an x axis in the direction of a north pole and a y axis in the direction of a south pole according to the magnetization direction of the permanent magnet;
the stator and the coil frame of the voice coil actuator are connected on a support plate at the bottom of the voice coil actuator to form a bottom structure, and the rotor back yoke and the permanent magnet are connected on a support at the top of the voice coil actuator to form a top structure; the top structure is connected with an internal frame of the three-degree-of-freedom motor to drive the three-degree-of-freedom motor to incline;
the top structure and the bottom structure are connected through a universal joint, and when the top structure inclines relative to the bottom structure, the direction of a magnetic field of the permanent magnet is changed; the voice coil actuator generates a torque proportional to a current of the coil at the bobbin using a magnetic field provided by the permanent magnet;
the voice coil actuator is a motor driving structure without a gear and a tooth gap; the motor driving structure can provide constant high torque which has no hysteresis loss and is easy to control, and can realize balance and accurate rotor positioning;
when the top structure is at an initial angle, if current flows through the coil, the voice coil actuator generates negative torque according to a polarization mode and gravity, and when power supply current is interrupted, the top structure returns to a low-power working condition with an angle of 0 degrees through restoring force;
when the inclination angle of the top structure is changed, the coil inductance of the voice coil actuator is changed;
the rotor back yoke is provided with an extension structure including a tilt operation range to change self-resistance with a tilt angle;
a magnetic core is arranged between the north pole and the south pole of the permanent magnet so that the rotor back yoke shows minimum basic dynamic stability;
the rotor back yoke is tapered towards the end part so as to enable the opening of the rotor of the voice coil actuator with the salient pole to be maximum and the inductance to be minimum;
the magnetic flux and the magnetic resistance generated by the permanent magnet in the coil are related to the size of the tilting angle of the tiltable rotor, so that sensorless control of the voice coil actuator is realized.
8. A method of controlling an eight-rotor aircraft with an anti-wind-disturbance tiltable rotor, comprising: the aircraft of claim 4 wherein each of the eight rotors is a tiltable rotor; the driving mode of the aircraft rotor comprises a conventional driving mode, an intermediate driving mode and a tilting driving mode;
when the aircraft rotor wing works in a conventional driving mode, the rotor wing driving shaft of each tiltable rotor wing is vertical to the horizontal plane of the airframe so as to provide the longest endurance time;
when the rotor wings of the aircraft work in the middle driving mode, the two pairs of tiltable rotor wings are converted into tilting postures for driving, and the rotor wing driving shafts of the other tiltable rotor wings are kept vertical to the horizontal plane of the aircraft body according to the conventional driving mode, so that the wind disturbance resistance of the aircraft is improved, and the endurance time of the aircraft is considered;
when the rotors of the aircraft work in a tilt driving mode, the rotor driving shafts of all the tiltable rotors keep the same tilt angle with the horizontal plane of the airframe to work, so that the aircraft has the best wind-disturbance resistance and space holding capacity.
9. A method of controlling an eight-rotor aircraft with a wind disturbance resistant tiltable rotor according to claim 8, wherein: the rotor of the tiltable rotor can perform uniform-speed tilt adjustment in a range of 0-31 degrees relative to the horizontal plane of the fuselage, and the tilt adjustment is completed within 5 seconds;
the flight control module of the aircraft acquires wind speed information in the environment in real time by using an airborne wind speed detection device, and automatically adjusts the driving mode of the tiltable rotor wing according to the wind speed information; when the driving mode of the tiltable rotor wing is automatically adjusted by the flight control module,
if the wind speed is 0-2.5m/s, the rotor wing of the aircraft works in a conventional driving mode;
if the wind speed is 2.5-5m/s, or the instantaneous wind speed is more than 5m/s only occasionally under the wind speed environment, the rotor wing of the aircraft works in a middle driving mode;
if the wind speed is more than 5m/s, the rotor wing of the aircraft works in a tilt driving mode.
10. A method of controlling an eight-rotor aircraft with a wind disturbance resistant tiltable rotor according to claim 8, wherein: the aircraft model of the aircraft is a two-dimensional rigid body model;
the equation of motion of the aircraft is
Wherein, T, THAnd M is the vertical thrust, horizontal thrust and resulting moment, respectively; aerodynamic forces and moments generated by multi-rotor aircraft frames
And MareoRepresents; the forces and moments generated by the rotor of the electric machine driving the rotor are formulated as
Wherein, CTIs the rotor thrust constant, ωiIs the rotational speed of the rotor. Note that the factor 2 in equation two is used to illustrate xb-zbPlanar symmetry;
the equation of motion of the rotor is formulated as
Wherein, V0Is the nominal voltage of the motor, I0Is no-load current, R is motor resistance, KVIs the motor speed constant, cτIs the rotor aerodynamic torque constant, JrotorIs the rotor inertia. ViIs the input voltage of motor i, for the power control of the aircraft, there is the following formula:
wherein VTIs a voltage command for controlling the overall thrust, and VMGenerating a pitching moment;
for horizontal thrust control of an aircraft, the input voltage of the motor is formulated as
Wherein
Is used for generating an edge xbA voltage command for shaft thrust; v1And V4The additional term tan (22.5 deg.) contained in (A) is used for counteracting
A pitching moment generated when the voltage command generates a horizontal thrust component;
the aerodynamic force and moment model acting on the rotor craft is obtained through a wind tunnel test of a full-size quadrotor; extrapolating the sizes of the aircraft and the rotors and the number of the rotors, and calculating the aerodynamic force and the moment of the rotor aircraft; the aerodynamic forces and moments are given by:
where ρ is the density of air, ApropIs the swept-back area of the propeller, AUAVIs the effective area of the wing or wings,
is the average speed of all rotors, nrotorIs the number of rotors;
the aircraft in the model is controlled by a perfect controller, so that the apparent wind speed and the attack angle of the aircraft are not influenced by the motion of the aircraft;
the aerodynamic coefficient model of the rotorcraft is suitable for an attack angle range of-180 DEG to 180 DEG, and is obtained by fitting a Fourier series to coefficients of experimental tests by using least square optimization and is expressed by a formula;
where λ is the tip speed ratio, given by:
parameter A1And A2Given by:
for the sake of symmetry, for simulation
And
the function of (a) must be an odd function with respect to α ═ 90 °, +90 °;
when calculating
Let us assume that the rotorcraft is about xb-ybPlane symmetry, i.e. meaning
And
the function of (a) must also be about 0 °;
the above-mentioned
And
the value of (a) must be zero when α is-90 °, +90 °;
for and
relative aerodynamic coefficient, assuming rotorcraft about yb-zbAnd xb-zbIn the case of planar symmetry, the function used to model these coefficients must be an even function with α ═ 90 °, +90 °.
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