Control method for unmanned aerial vehicles

Abstract

To provide a method for controlling an unmanned aerial vehicle capable of quickly raising a body carrying a heavy load and performing stable attitude control. [Solution] The control method for an unmanned aerial vehicle of the present invention is a control method for a vertical takeoff and landing type unmanned aerial vehicle equipped with multiple propellers driven by an engine, the pitch angle (θ) of each propeller being individually settable, and when controlling the throttle of the vehicle, the opening of the throttle valve of the engine is increased or decreased, thereby increasing or decreasing the engine rotation speed, thereby increasing or decreasing the rotation speed of each propeller, and when controlling the attitude of the vehicle, the pitch angle (θ) of each propeller to obtain lift is set larger if the engine rotation speed is low, and smaller if the engine rotation speed is high.

Description

[Technical Field]

[0001] The present invention relates to a control method for an unmanned aerial vehicle and an unmanned aerial vehicle, and more specifically to a control method for an unmanned aerial vehicle equipped with an engine, which allows the ascent of the unmanned aerial vehicle to be achieved by controlling the engine's throttle valve, thereby obtaining greater thrust than control that maintains the engine speed constant and adjusts the propeller pitch angle to achieve ascent, and an unmanned aerial vehicle. [Background technology]

[0002] To lift a rotorcraft carrying a load, it is necessary to increase the thrust compared to when it is hovering without a load. In conventional controllable-pitch electric quadcopters and unmanned helicopters, the engine speed is kept constant, so to increase thrust, it is common to increase the pitch angle of the propellers.

[0003] Increasing the propeller pitch angle increases drag, so in the case of an electric motor, the current must be increased, and in the case of an engine, the throttle valve opening must be increased to increase horsepower. In the case of an engine, two systems must be operated: propeller pitch angle control and engine throttle valve opening control. Because this operation is cumbersome, the engine speed is kept constant and flight control is performed only by controlling the propeller pitch angle (angle of elevation). This makes it easier to control the aircraft's attitude. Note that the engine speed is, for example, around 5000 rpm, but the propeller speed is reduced by a gear to around 1250 rpm.

[0004] For example, suppose you want to return a tilted aircraft to a horizontal position by adjusting the propeller pitch angle by 1° at a low speed, increasing lift and leveling the aircraft. In the same way, if you adjust the propeller pitch angle by 1° at a high speed, the lift will be greater than at a low speed, so you will not be able to level the aircraft. To avoid this difficulty in control, conventional aircraft keep the engine speed constant. In other words, the propeller speed is kept constant.

[0005] Conventional control methods that maintain a constant propeller rotation speed can only operate within a certain horsepower range, even when the load increases due to ascent or loading of cargo. As shown in Figure 8, electric motors, which rotate at low speeds and have high output, are suitable for this type of use. However, if a high-speed, high-output engine is used for the propeller drive unit and a control method that maintains a constant engine rotation speed is adopted, the following problems arise.

[0006] When operating at low speeds and low loads with emphasis on no load or good fuel economy, if the set speed is set low, the engine output is small at low speeds, as shown in Figure 9, so even if the throttle valve is opened, a large output cannot be obtained and a heavy load cannot be lifted. Conversely, if the set speed is set high, as shown in Figure 8, a large output can be obtained and a machine carrying a heavy load can be lifted, but when the load is light or in the low load range where there is no load, the engine speed will be unnecessarily high, which can result in poor fuel economy and increased noise.

[0007] Patent Document 1 discloses a quadcopter in which propellers are driven by a two-stroke, single-cylinder engine. Each propeller consists of two blades, and the pitch angle of the blades can be changed by a pitch angle change mechanism. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-100387 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for controlling an unmanned aerial vehicle that can quickly raise a body carrying a heavy load and can perform stable attitude control. [Means for solving the problem]

[0010] The control method for an unmanned aerial vehicle according to the present invention is a control method for a vertical takeoff and landing type unmanned aerial vehicle equipped with multiple propellers driven by an engine, the pitch angle of each propeller being able to be set individually, and is characterized in that, when controlling the throttle of the aircraft, the opening of the throttle valve of the engine is increased or decreased, and the engine rotation speed is increased or decreased, thereby increasing or decreasing the rotation speed of each propeller, and when controlling the attitude of the aircraft, the pitch angle of each propeller to generate lift is set larger if the engine rotation speed is low, and smaller if the engine rotation speed is high.

[0011] When a heavy load is loaded, the opening of the throttle valve is increased and the engine is operated at high speed, and when a light load is loaded, the opening of the throttle valve is decreased and the engine is operated at low speed. [Effects of the Invention]

[0012] According to the unmanned aerial vehicle control method and unmanned aerial vehicle of the present invention, (1) Throttle control of the aircraft: When descending, the engine throttle valve opening is increased or decreased to increase or decrease the engine speed rather than increasing the propeller pitch angle, thereby providing greater or less thrust. This allows the aircraft to ascend when carrying heavy loads. It also enables emergency ascent to avoid obstacles. Furthermore, the propeller pitch angle is set small when the engine is rotating at high speed, and larger when the engine is rotating at low speed, allowing for stable control of the aircraft. (2) The aircraft receives lift from the propeller. Here, lift is proportional to the wind speed the propeller receives, so when the engine is rotating at high speed, the lift is large and when it is rotating at low speed, the lift is small. On the other hand, lift is proportional to the pitch angle, so when the pitch angle is small, the lift is small and when the pitch angle is large, the lift is large. By increasing the pitch angle at low speed and decreasing the pitch angle at high speed, it is possible to achieve approximately the same lift. Therefore, in controlling the aircraft's attitude, the inclination of the aircraft when operating at high speed and moving forward can be made approximately the same as the inclination when operating at low speed and moving forward. When correcting the aircraft's attitude, it can be done in the same way in either operation.

[0013] When a light load is loaded, the engine operates at a low speed, which saves energy. When a heavy load is loaded, the engine operates at a high speed, which allows for quick ascent even with a heavy aircraft, and allows the engine performance to be fully utilized. This is not limited to such operation, and high speed rotation may also be used for emergency ascent or descent to avoid obstacles. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart of a method for controlling an unmanned aerial vehicle according to the present invention, showing a flowchart of throttle control of the airframe. [Figure 2] 1 is a flowchart of a control method for an unmanned aerial vehicle according to the present invention, showing a flowchart for controlling the attitude of the aircraft. [Figure 3] FIG. 1 is an explanatory diagram of the body and propeller of an unmanned aerial vehicle. [Figure 4] FIG. 2 is a diagram showing the pitch angle of each propeller when the aircraft is moving forward. [Figure 5] FIG. 5 is a left side view of the machine body of FIG. 4 when it is moving forward. [Figure 6] FIG. 4 is an explanatory diagram of a pitch angle. [Figure 7] 4 is a graph showing the relationship between the throttle opening and pitch angle of the valve according to the present invention. [Figure 8] 4 is a graph showing the relationship between the engine rotation speed and pitch angle during attitude control according to the present invention. [Figure 9] 1 is a graph showing the relationship between rotation speed and torque of a general engine. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a control method for an unmanned aerial vehicle and an unmanned aerial vehicle according to the present invention will be described in detail with reference to the drawings.

[0016] Figure 1 is a flowchart of a method for controlling an unmanned aerial vehicle according to the present invention, showing a flowchart for controlling the throttle of the vehicle. The unmanned aerial vehicle 100 of this embodiment is a quadcopter, and the vehicle 1 is equipped with four propellers 5, which are driven by an engine 4 (see Figure 3). The vehicle 1 also contains a program that receives commands from the ground via wireless communication and controls each component.

[0017] As shown in Figure 1, S1 determines whether or not the aircraft's throttle control is being performed. If S1 is YES, it is throttle control, so S10 determines whether or not the throttle is being operated to raise the aircraft. Examples of this operation include tilting the handle forward to raise the aircraft, or tilting the handle backward to lower the aircraft. If S10 is YES, it is control to increase the throttle valve, so S11 and S12 are processed. S11 issues a command to increase the engine throttle valve opening. S12 operates the engine according to the throttle valve opening. As the throttle valve opens, the engine rotates at a higher speed. When the engine rotates at a higher speed, the propeller also rotates at a higher speed, allowing the aircraft to ascend. When a heavy load is loaded on the aircraft, the engine torque allows the aircraft to ascend more powerfully than with conventional control that keeps the engine speed constant and increases the propeller pitch angle.

[0018] If S10 is NO, control is performed in S13 and S14. S13 issues a command to reduce the opening of the engine's throttle valve. S14 operates the engine according to the opening of the throttle valve. Since the throttle valve is closed, the engine rotates at a slower speed. When the engine rotates at a slower speed, the propeller also rotates at a slower speed, allowing the aircraft to descend. Note that when light loads are loaded on the aircraft, operation at a slower speed can be applied. In this case, energy-saving operation is possible compared to conventional control where the engine speed is kept constant at a medium speed.

[0019] Figure 2 is a flowchart of a control method for an unmanned aerial vehicle, showing the flowchart for aircraft attitude control. S2 is a determination of whether or not the aircraft is being controlled for attitude. If the answer is YES in S2, it is attitude control, so the determinations and processing of S21 to S26 are carried out. There are three types of attitude control: rudder, aileron, and elevator. For attitude control, S20 is the first step in processing. The current engine speed is determined, and a specific value α is found as the pitch angle θ (see Figure 6, explanation of pitch angle provided) corresponding to the engine speed. The pitch angle α is applied to propellers that increase lift. A pitch angle β smaller than the pitch angle α is calculated and applied to propellers that do not increase lift. β is set to the value obtained by subtracting a predetermined value from α.

[0020] As shown in Figure 2, if the command is for the rudder (YES in S21), the process branches to S24 and the aircraft is turned. There are two types of turns: right and left. For a right turn, if the propellers are designated P1 to P4 in a plan view (see Figure 3), the pitch angle θ of P1 and P3 is set large, and the pitch angle θ of P2 and P4 is set small. This increases the lift of P1 and P3 in the clockwise direction, causing the aircraft to turn right. For a left turn, the pitch angle θ of P2 and P4 is set large, and the pitch angle θ of P1 and P3 is set small. This increases the lift of P2 and P4 in the counterclockwise direction, causing the aircraft to turn left.

[0021] If the pitch angles P1 to P4 are all set to the same value, the aircraft will not turn right or left. Depending on the engine speed at the time, if the propeller lift is greater than the load, the aircraft will rise. If the propeller lift is balanced with the load, the aircraft will hover. If the propeller lift is less than the load, the aircraft will descend.

[0022] If it is an aileron command (YES in S22), the process branches to S25 and performs a slide of the aircraft. To slide the aircraft to the left, the pitch angles of P1 and P2 are set large and the pitch angles of P3 and P4 are set small. This increases the lift of P1 and P2, causing the left side of the aircraft to descend and the aircraft to slide to the left. To slide the aircraft to the right, the pitch angles of P1 and P2 are set small and the pitch angles of P3 and P4 are set large. This increases the lift on the left side of the aircraft, causing it to ascend, the right side of the aircraft to descend and the aircraft to slide to the right.

[0023] If the command is for the elevator (YES in S23), the process branches to S26, where the aircraft is moved in the fore-aft direction. To move the aircraft forward, the pitch angles of P2 and P3 are set large, and the pitch angles of P1 and P4 are set small. This increases the lift on the rear side of the aircraft, causing it to rise, the front side of the aircraft to lower, and the aircraft to move forward. To move the aircraft backward, the pitch angles of P2 and P3 are set small, and the pitch angles of P1 and P4 are set large. This increases the lift on the front side of the aircraft, causing it to rise, the rear side of the aircraft to lower, and the aircraft to move backward. The processing of S24, S25, and S26 continues.

[0024] FIG. 3 is an explanatory diagram of the airframe 1 and propeller 5 of the unmanned aerial vehicle 100. The unmanned aerial vehicle 100 of this embodiment is a vertical take-off and landing quadcopter equipped with propellers P1 (clockwise), P2 (counterclockwise), P3 (clockwise), and P4 (counterclockwise). The propeller 5 has two blades. The engine 4 is an in-line four-cylinder reciprocating engine, with each cylinder equipped with a throttle valve 2. The propellers 5 have link mechanisms (not shown) driven by servo motors (not shown) provided on the airframe, allowing the pitch angle to be set individually.

[0025] Figure 4 shows the pitch angle of each propeller when the aircraft 1 is moved forward using elevator attitude control. To move the aircraft forward, the pitch angles of P2 and P3 are set large, and the pitch angles of P1 and P4 are set small. This increases the lift on the rear side of the aircraft, causing it to rise, and the front side of the aircraft to drop, causing the aircraft to move forward. Because the propeller 5 is in an inclined position, thrust is generated for forward movement. Specifically, the pitch angle θ is set so that P1 and P4 are set to θ = β, and P2 and P3 are set to θ = α, with α > β.

[0026] Figure 5 is a left side view of the aircraft 1 when it is moving forward in Figure 4. The front side of the aircraft 1 drops because of the small lift, and the rear side of the aircraft 1 rises because of the large lift, causing the entire aircraft 1 to tilt forward and downward.

[0027] Figure 6 is an explanatory diagram of the pitch angle. As shown in the circle on the right, the pitch angle 3 is the angle indicated by θ. When the pitch angle 3 is large, the lift also increases. When the pitch angle 3 is small, the lift also decreases. In other words, the lift is proportional to the pitch angle. Here, since the lift is also proportional to the wind speed, the lift increases when the propeller rotates at high speed and decreases when the propeller rotates at low speed. As shown in the circle on the left, the pitch angle 3 can be set individually for the propeller 5. The pitch angle 3 of the propeller 5 blades is set by a servo motor and link mechanism installed on the aircraft 1.

[0028] FIG. 7 is a graph showing the relationship between the throttle opening and pitch angle of the valve according to the present invention. The throttle valve opening (circled A) is controlled so that it slopes upward relative to the load. When a heavy load is carried, the throttle valve opening is increased, and when a light load is carried, the throttle valve opening is decreased. When the aircraft is ascending or descending, if the pitch angles (circled B) of the propellers P1 to P4 are all the same and fixed, increasing the engine speed increases the propeller speed, causing the aircraft to ascend quickly vertically. Decreasing the engine speed decreases the propeller speed, causing the aircraft to descend vertically. When the aircraft is moving forward, the propeller pitch angles P1 and P4 at the front of the aircraft and P2 and P3 at the rear of the aircraft are set differently, so if the engine speed is increased, for example, the aircraft will ascend diagonally upward from the horizontal. In this case, forward attitude control continues, so the pitch angle is adjusted in a timely manner to match the engine speed shown in S20.

[0029] Figure 8 is a graph showing the relationship between engine speed and pitch angle during attitude control according to the present invention. When the engine speed is high and the aircraft is operating at high speed, the pitch angle is set smaller than when the aircraft is operating at low speed. Specifically, the pitch angle θ is set to α for propellers that increase lift, and β for propellers that decrease lift. When the engine speed is low and the aircraft is operating at low speed, the pitch angle is set larger than when the aircraft is operating at high speed. The pitch angle θ is set to α' for propellers that increase lift, and β' for propellers that decrease lift. [Industrial Applicability]

[0030] The present invention is suitable as a control method for an unmanned aircraft, which can increase engine speed to enable rapid ascent of the aircraft when heavy loads are loaded, and can reduce engine speed to enable energy-saving operation when light loads are loaded. [Explanation of symbols]

[0031] 1 aircraft 2 throttle valve 3 Pitch angle 4 Engine 5 propellers 100 Unmanned Aircraft

Claims

1. A control method for a vertical takeoff and landing unmanned aerial vehicle (UAV) equipped with multiple propellers driven by a reciprocating engine with multiple cylinders, the pitch angle of each propeller being individually adjustable, comprising: a throttle control for increasing or decreasing the opening of the throttle valve of the reciprocating engine to increase or decrease the rotational speed of the reciprocating engine, thereby increasing or decreasing the rotational speed of each propeller, thereby ascending or descending the aircraft; and attitude control, which controls the pitch angle of each propeller to perform the following operations: rudder for turning the aircraft, ailerons for sliding the aircraft left and right, and elevators for moving the aircraft forward and backward; A control method for an unmanned aircraft, characterized in that during attitude control, if the engine speed is low, the propeller pitch angle (α') that produces high lift is set larger than the propeller pitch angle (β') that produces low lift, and if the engine speed is high, the propeller pitch angle (α) that produces high lift is set larger than the propeller pitch angle (β) that produces low lift, and both the pitch angle (α) and the pitch angle (β) are set smaller than the pitch angle (α') and the pitch angle (β').

2. 2. The control method for an unmanned aerial vehicle according to claim 1, wherein the engine is operated at a high speed when a heavy load is loaded, and the engine is operated at a low speed when a light load is loaded.

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