RU171506U1 - UNMANNED AERIAL VEHICLE - Google Patents

Abstract

The utility model relates to ultra-small unmanned aerial vehicles (hereinafter UAVs) in the form of a ball with a four-channel control system and a propeller-type propulsion system. The technical result is to increase the reliability of the UAV. UAV contains: UAV casing, made in the form of a ball, reinforced with stiffeners; a power frame, which is a thin-walled tube, inside which air flow laminators are installed, and the power frame is fixed inside the casing, forming a usable volume between the outer wall of the power frame and the casing; an impeller type power unit attached to the power frame and creating an air flow passing through the power frame, the casing having corresponding openings providing air to the impeller type power unit and outputting it outward through the power frame; UAV control elements, consisting of four servo drives fixed inside the power frame and four aerodynamic surfaces - rudders rigidly fixed to the shaft of the corresponding servo drive, the deviation of which leads to a change in the UAV's position and orientation in space; UAV control system for controlling the impeller type power plant and UAV control elements, mounted on the outside of the side wall of the power frame.

Description

The field of technology.

The utility model relates to ultra-small unmanned aerial vehicles (hereinafter UAVs) in the form of a ball with a four-channel control system and a propeller-type propulsion system.

The level of technology.

In the current state of the art, UAVs are used to perform many different tasks, including for surveillance, reconnaissance, target acquisition, target designation, data collection, data transmission in communication systems, as false targets, for jamming, etc.

For example, the known radio-controlled LA Space Ball company Kyosho (http://www.gizmag.com/kyosho-space-ball/24711/). This UAV, made in the shape of a ball, uses a power plant (hereinafter referred to as SU) with coaxial bearing, two-bladed propellers located one after another and rotating in different directions without a swashplate, but with a blade pitch balancing system. The screws are driven by two independent commutator motors through a reduction gear. This scheme provides only 2 degrees of freedom. The first is an up / down flight by changing the total propeller thrust, which depends on the angular speed of the electric motor. The second is the direction of flight (yaw), provided by the difference in angular velocities of the rotors. For flight in a given direction, an auxiliary control system is used in the form of a pulling or pushing propeller. It is located above the main rotors and serves to create relative to the center of mass of the UAV a moment that tilts (rotates) the UAV in the horizontal plane. Structurally, this UAV is made of shockproof, hard plastics like ABS or PLA using the technological method - injection molding. However, this device has several disadvantages, namely: open rotors that increase the likelihood of damage, which leads to loss of controllability of the entire UAV and reduces overall safety when interacting with a person; due to the use of the coaxial scheme, relatively large dimensions; less maneuverable and manageable due to the three-channel control system.

The essence of the utility model.

The objective of the claimed technical solution is the creation of a UAV in the form of a ball with the smallest possible dimensions of a glider / structure in the class of ultra-small UAVs weighing up to 0.5 kg, with a four-channel control system and an impeller-type power plant.

The technical result is to increase the reliability of the UAV.

The specified technical result is achieved by using a special structural layout of the entire UAV. In particular, the claimed UAV contains: a UAV casing made in the shape of a ball, reinforced with stiffeners; a power frame, which is a thin-walled tube, inside which air flow laminators are installed, and the power frame is fixed inside the casing, forming a usable volume between the outer wall of the power frame and the casing;

an impeller type power unit attached to the power frame and creating an air flow passing through the power frame, the casing having corresponding openings providing air to the impeller type power unit and outputting it outward through the power frame;

UAV control elements, consisting of four servo drives fixed inside the power frame and four aerodynamic surfaces - rudders rigidly fixed to the shaft of the corresponding servo drive, the deviation of which leads to a change in the UAV's position and orientation in space;

UAV control system for controlling the impeller type power plant and UAV control elements, mounted on the outside of the side wall of the power frame.

The impeller type power plant used has the smallest layout volume in comparison with a single-screw or coaxial power plant, as a result of which the working air channel also occupies a smaller volume relative to the entire UAV body volume. The increased net volume formed between the power frame on which the UAV control system is fixed and the casing in case of collisions or a hard landing of the UAV gives space for elastic deformation of the casing, which prevents damage to the UAV control system. Also, the casing prevents the ingress of foreign objects that could damage the UAV control system, and the stiffeners and the power cage increase the strength of the casing and additionally protect the UAV controls installed inside the power cage against damage.

For a better understanding of the essence of the utility model, and to more clearly show how it can be implemented, then reference will be made to the accompanying drawings, on which:

FIG. 1 - general view of the UAV;

FIG. 2 - a general view of a UAV without a casing;

FIG. 3 - the first stage of disassembling the product into components, assemblies and systems;

FIG. 4 - the second stage of disassembling the product into components, assemblies and systems;

FIG. 5 - the third stage of disassembling the product into components, assemblies and systems;

FIG. 6 - power frame with asymmetric flow laminators.

Implementation of a utility model.

In FIG. 1 and FIG. 2 shows a general view of a UAV in the form of a ball in a casing and without a casing, respectively, from different angles.

Next, with reference to FIG. 3-5 shows the detailed design of the UAV.

In FIG. 3 shows the first stage of disassembling the product into components, assemblies and systems. The casing, made in the shape of a ball, consists of two thin-walled hemispheres - the upper casing 1 and the lower casing 3, and is reinforced with stiffeners with the necessary holes and hatches for the convenience of assembly and adjustment of the UAV. A hole in the upper casing allows air to enter the impeller type 6 power plant attached to the power cage, and air is discharged through the power cage 5 and the hole in the lower casing. Also in FIG. 3 shows the power supply system, which is a left 2 and right 4 batteries placed inside the housing on the power frame 5.

The propulsion system of impeller type 6 (hereinafter referred to as impeller SU) contains an impeller — a blade air machine (impeller), enclosed in a ring (stator), driven by an electric motor. This unit is a purchased product (actively used in aircraft modeling) and for the correct choice must have the following parameters:

- diameter of the inlet 50-64 mm;

- impeller with 5 or 6 blades;

- electric motor - brushless with a shaft speed of 3500KV-4500KV;

- the weight of the entire SU is not more than 80 grams;

- energy efficiency = (Max. Thrust) / (Cons. electric power.) = 2.1-2.4 g / W.

The power supply system consists of two Li-Po batteries 2 and 4 connected in parallel. They are a purchased product and for the correct choice they must have the following parameters:

- capacity: 800-1200 mAh;

- voltage: 11.1-14.8 V;

- number of cans: 3S-4S;

- maximum discharge current: 20-30 C

- the weight of two batteries is not more than 160 g.

The power frame 5 is, conventionally, a thin-walled pipe, inside of which four asymmetric laminators of air flow are installed. They provide 80% of the compensation of the reactive moment from the SU impeller in all flight modes, i.e. stabilize yaw UAVs. Laminators have a cross-sectional shape of the aerodynamic profile, determined from aerodynamic calculations and confirmed by bench tests. The second main task of the power frame 5 is the supporting function, i.e. all other systems and units are installed and attached to it. The strength characteristic of the entire UAV as a whole depends on its strength and rigidity.

In FIG. 4 and 5 depict the second and third stages of disassembling the product into components, assemblies and systems. One of the disadvantages of impeller SU 6 is the presence during operation of vibrations of a certain frequency caused by inaccuracy in the manufacture of components and parts of this SU. These vibrations introduce noise and errors into the operation of the inertial measuring system 10. To partially eliminate this phenomenon, the SU 7 vibration isolation system was developed. It consists in using elastic rubber elements in the attachment points of the inertial SU 6 to the UAV power frame 5. The UAV control system consists of software and hardware that provide stabilization and controlled UAV flight. The software part consists of a program written in C ++ that describes the methods and algorithms for controlling the hardware. The hardware consists of: the main control controller 13, control controller 8 of the SU brushless motor, four servos 12 and a transceiver 9. All elements of the hardware are purchased products, for the correct selection of which they must have the following parameters:

- the main controller 13 must filter the data from the inertial measuring system based on the AHRS algorithm of Sebastian Majwick, monitor the state and manage the rest of the hardware in accordance with the laid down algorithms, and must have the necessary and sufficient computing power: ARM architecture, 32 bits, frequency from 100 MGz, memory from 512 kb;

- the control controller 8 of the brushless motor must meet the requirement to withstand long-term loads of current, which consumes the SU electric motor;

- servo drive characteristics 12: operating speed - 0.10 sec / 60 ° in the absence of load, blocking moment - 0.8 kg * cm, weight - 4.5 g;

- transceiver device 9 is necessary to receive external control commands and send telemetry data of the UAV, which can be implemented using wireless interfaces Bluetooth, WiFi, etc.

The inertial measuring system 10 determines the position and orientation of the UAV in space, it includes a set of three axial sensors - an accelerometer / gyroscope / magnetometer and barometer, with an integrated low-level filter. The specified system is a purchased product based on MEMS technology, for the correct choice should have the following parameters:

- working range of the gyroscope: ± 250 ° / s;

- gyro sensitivity: 16.4 LSB / ° / s;

- operating ranges of the accelerometer: ± 4, ± 8g;

- working range of the magnetometer: ± 4800 μT;

The UAV control bodies 11 consist of four independent identical aerodynamic surfaces - rudders, the deviation of which leads to a change in the position and orientation of the UAV in space. The rudders are located in one plane, in a circle with a step of 90 degrees, at an equal distance from the center of mass. Each steering wheel is rigidly fixed to the shaft of the corresponding servo drive 12, and each servo drive is installed in a special structural groove of the power frame 5 and is fixed with two self-tapping screws.

The steering wheels are deviated by controlling the position of the corresponding servo in the range of -20 ° ... + 20 °. Structurally, the steering wheel is a thin-walled lattice structure with a complex shape in cross section. The shape and size of the cross section are determined from aerodynamic calculations and are confirmed by bench tests.

The center of mass of the entire UAV is located on the vertical axis at the level of the geometric center of the impeller. With allowable simplifications, the geometric center of the impeller will conditionally coincide with the center of application of the total resultant aerodynamic force, i.e. the scheme of this UAV is statically neutral, which increases the maneuverability and controllability of the aircraft, but in turn complicates the control system.

The main material used for the production of the power frame 5, the casing and the aerodynamic rudders is ABS plastic in the form of a rod with a diameter of 1.75 mm, used for 3D printing. This plastic has the necessary strength and stiffness with a relatively low specific gravity, is easily amenable to machining and post-processing.

The technology for the production of parts - extrusion layer-by-layer 3D printing, providing satisfactory accuracy, minimum printing cost of 1 cubic meter. see maximum speed. 3D printing also allows you to get a complex shape, part geometry, which cannot (or expensive) be obtained by other manufacturing technologies. This advantage of 3D printing reduces the total number of parts, fasteners, which in turn reduces the overall weight of the structure.

In FIG. 6 shows a power frame with asymmetric laminators of air flow from various angles, as well as in various sections.

Next, the principle of operation of the claimed UAV will be described.

Impeller SU 6 was chosen because with the minimum required energy efficiency of 2.1-2.4 g / W, it has the smallest dimensions of the working fluid — the impellers (64 mm) —in diameter, relative to the coaxial two screw or single screw SU. Traction control is regulated by the motor revolutions through the control controller of the brushless motor 8, which receives control signals from the main control controller 13. The impeller, creating a lifting force, also creates a reactive moment equal in magnitude and oppositely directed to the moment on the motor shaft. This moment relative to the vertical axis creates an angular velocity that rotates the housing in the opposite direction of rotation of the impeller. To compensate for the reactive moment, four air flow laminators with an asymmetric profile in cross section are installed in the power frame 5. Under the influence of the air flow created by the impeller, an aerodynamic force of a certain size and direction appears on the surface of the laminator. The projection of this force on the horizontal axis relative to the vertical axis creates a moment opposite to the reactive moment. The sum of the moments from all 4 laminators compensates for 80-90% of the reactive moment, the rest of it is compensated by 4 aerodynamic rudders by simultaneous deviation in one direction by the same angle. The control along the yaw channel is also carried out by the simultaneous deviation of all 4 rudders, decreasing or increasing the compensating moment of the laminators. The shape of the profile, the dimensions in cross section and the surface area of the laminator are determined from the condition of the required aerodynamic force of the laminator. The aerodynamic force of the laminator is defined as 1/4 M _REAK , M _REAK = M _{VAL DV.} , and M _{VAL DV.} = Ρ _MEX / Ω _NAG , where M _REAK is the reactive moment, M _{VAL DV.} is the moment on the motor shaft, P _FUR is mechanical power, Ω _NAG is the angular velocity with a load on the motor shaft.

The angular speed of the engine with the load on the shaft is measured at the bench by the angular velocity sensor. Mechanical power P _MECH = P _ELEK × engine efficiency. Knowing the required value of the strength of the laminator according to aerodynamic manuals, a profile with the best quality is selected in a given range of air flow velocities. In any of the available CAD systems, a 3D model of the geometry of laminators, a power frame, and an impeller model are built. Then, in a specialized program for aerohydromodeling (for example, Flow Simulation), a series of verification calculations (at least 10 purges) is carried out, the data obtained are analyzed, if necessary, changes are made to the geometry of the laminators and the process is repeated again.

Under the influence of the air flow created by the impeller, the aerodynamic force of a certain size and direction, which creates a moment relative to the center of mass of the UAV, arises on the surfaces of the aerodynamic rudders when they are deflected. This moment changes orientation, rotates the UAV relative to the longitudinal or transverse axis, along pitch or roll. By means of the first pair of rudders located diagonally, the pitch is adjusted, and by means of another pair of rudders, the pitch is adjusted. The shape, size in section and the surface area of the rudders are determined from the conditions of the necessary and sufficient value created by the aerodynamic force at the maximum deflection angle. The magnitude of the required force is determined from the requirements for the speed of the control system.

The inertial measuring system 10 sends the accelerometer / gyroscope / magnetometer data measured in three axes to the main controller, then the data is filtered by Sebastian Majvik's AHRS algorithm, and the current UAV position angles (pitch, roll and yaw angle) are determined at the filter output. This data - angles are updated at a frequency of 200 Hz. Further, the angles are subtracted from the current values of the control system (in the hang mode, roll and pitch = 0), if there is a mismatch (not 0), the value of this mismatch is sent to the PID controller, the PID controller, based on the mismatch value, generates a control signal to the servos, the servos reject the rudders, the steering wheels create control forces, the forces turn the UAV in the right direction to eliminate the mismatch. Those. The UAV control system is closed with negative position feedback.

For flight in a given direction, the controller through the transceiver 9 receives the signal from the UAV operator (or the signal from a higher-level control system, autopilot, AI). This signal contains the new current values of the roll or pitch angles, and the PID controller will eliminate the position error not with respect to 0, but with respect to the new value. Also, the vertical axis of the UAV will deviate, which will lead to the appearance of a projection of the thrust on the horizontal axis, i.e. a horizontal force will appear, which will create a linear movement of the UAV. However, the projection of thrust on the vertical axis will be less than the original thrust, as a result of which the UAV will begin to decline. To eliminate the reduction, the UAV control system at the moment of deviation from the vertical should increase thrust by a factor proportional to the deviation angle.

To determine all the coefficients of the PID controllers in each control channel, a 3D assembly model of the entire UAV with all the nodes and systems with the required relative position is created. For each node, part and system, the maximum allowable weight is determined. Further, this assembly is converted into a special Mathlab Simulink format, where all mechanical relationships and dependencies are preliminarily described. Mathematical modeling of mechanics and control systems is launched. Based on the results of mathematical modeling, the necessary parameters of the control system are edited.

The presented UAV design allows providing a high level of protection for UAV control elements and control system, reducing UAV weight and increasing the share of payload in comparison with the known UAVs made with single-rotor or coaxial power plant.

Claims (9)

1. Unmanned aerial vehicle (UAV), containing: UAV casing, made in the form of a ball, reinforced with stiffeners; a power frame, which is a thin-walled tube, inside which air flow laminators are installed, and the power frame is fixed inside the casing, forming a usable volume between the outer wall of the power frame and the casing; an impeller type power unit attached to the power frame and creating an air flow passing through the power frame, the casing having corresponding openings providing air to the impeller type power unit and outputting it outward through the power frame; UAV control elements, consisting of four servo drives fixed inside the power frame and four aerodynamic surfaces - rudders rigidly fixed to the shaft of the corresponding servo drive, the deviation of which leads to a change in the UAV's position and orientation in space; UAV control system for controlling the impeller type power plant and UAV control elements, mounted on the outside of the side wall of the power frame. 2. UAV according to claim 1, characterized in that the said rudders are located in one plane, in a circle with a step of 90 degrees, at an equal distance from the center of mass located on the vertical axis at the level of the geometric center of the impeller. 3. UAV according to claim 1, characterized in that the UAV control system is closed with negative position feedback. 4. UAV according to claim 1, characterized in that the fastenings of the power plant to the power frame are equipped with a vibration isolation system.

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