Control methods for unmanned aerial vehicles
The control method for unmanned aerial vehicles adjusts engine speed and propeller pitch to manage thrust and attitude, addressing inefficiencies in conventional systems by enabling stable flight and energy-efficient operations.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ARASE AIZAWA AEROSPATIALE LLC
- Filing Date
- 2024-11-14
- Publication Date
- 2026-05-26
AI Technical Summary
Conventional unmanned aerial vehicles face challenges in efficiently managing thrust and attitude control, particularly when carrying heavy loads, leading to issues with fuel efficiency, noise, and difficulty in maintaining stable flight dynamics.
A control method for unmanned aerial vehicles that adjusts the engine speed and propeller pitch angle independently to manage thrust and attitude, allowing for rapid ascent with heavy loads and energy-efficient operation with light loads by varying the throttle valve opening and engine speed.
Enables stable attitude control and efficient operation by increasing thrust with heavy loads and reducing engine speed for light loads, facilitating rapid ascents and descents while optimizing fuel consumption.
Smart Images
Figure 2026086299000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for controlling an unmanned aircraft and an unmanned aircraft. More specifically, by controlling the throttle valve of the engine to lift an unmanned aircraft equipped with an engine, the engine speed is kept constant and the pitch angle of the propeller is adjusted for lifting, compared with a control method in which the pitch angle of the propeller is adjusted to obtain a large thrust. The present invention relates to a method for controlling an unmanned aircraft and an unmanned aircraft capable of obtaining a large thrust.
Background Art
[0002] To lift a load on a rotary-wing aircraft, it is necessary to increase the thrust compared to when hovering without load. In conventional variable pitch electric quadcopters and unmanned helicopters, since the engine speed is kept constant, it is common to increase the pitch angle of the propeller to increase the thrust.
[0003] When the pitch angle of the propeller is increased, the drag increases. Therefore, if it is an electric motor, it is necessary to increase the current, and if it is an engine, it is necessary to increase the opening of the throttle valve to increase the horsepower. In the case of an engine, two systems of control, namely, the control of the pitch angle of the propeller and the control of the opening of the throttle valve of the engine, must be operated. Since this operation is troublesome, flight control is performed only by controlling the pitch angle (elevation angle) of the propeller while keeping the engine speed constant. This makes it easier to control the attitude of the aircraft. The engine speed is, for example, about 5000 rpm, but it is decelerated by a gear so that the propeller speed is about 1250 rpm.
[0004] As an example, when returning an inclined aircraft to horizontal, assume that the pitch angle of the propeller is operated by 1° at low speed rotation and the lift is increased to level the aircraft. Similarly, even if the pitch angle of the propeller is operated by 1° at high speed rotation, there is a problem that the aircraft cannot be leveled because the lift is greater than in the case of low speed rotation. To avoid such difficulty in control, the engine speed is kept constant in conventional aircraft. That is, the propeller speed is kept constant.
[0005] Conventional control methods that maintain a constant propeller speed limit operation to a certain horsepower range, even when the load increases due to ascent or cargo loading. As shown in Figure 8, electric motors with high output at low rotational speeds are suitable for this type of use. However, if a high-speed, high-output engine is used as the propeller drive and a control method that maintains a constant engine speed is employed, the following problems arise.
[0006] When prioritizing low-speed, low-load operation, especially during no-load conditions or when fuel efficiency is a priority, setting the engine speed low results in low engine output. As shown in Figure 9, even with the throttle valve open, significant power cannot be obtained, making it impossible to lift heavy loads. Conversely, setting the engine speed high results in significant power output, as shown in Figure 8, allowing the machine to lift heavy loads. However, when the load is light or unloaded in the low-load range, the unnecessarily high engine speed leads to problems such as decreased fuel efficiency and increased noise.
[0007] Patent Document 1 discloses a quadcopter in which a propeller is 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 changing mechanism. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Publication No. 2020-100387 [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] The object of the present invention is to provide a control method for an unmanned aerial vehicle that can rapidly ascend an aircraft carrying a heavy load and maintain 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 take-off and landing type unmanned aerial vehicle equipped with a plurality of propellers driven by an engine, wherein the pitch angle of each propeller can be set individually, characterized in that when controlling the throttle of the aircraft, the rotational speed of each propeller is increased or decreased by increasing or decreasing the opening degree of the throttle valve of the engine and increasing or decreasing the rotational speed of the engine, and when controlling the attitude of the aircraft, the pitch angle of each propeller for obtaining lift is set to be large when the engine rotational speed is low and small when the engine rotational speed is high.
[0011] The system is characterized by increasing the opening of the throttle valve and operating the engine at high speed when a heavy load is loaded, and decreasing the opening of the throttle valve and operating the engine at low speed when a light load is loaded. [Effects of the Invention]
[0012] According to the unmanned aerial vehicle control method and unmanned aerial vehicle of the present invention, (1) When controlling the aircraft's throttle, instead of increasing the propeller pitch angle, the engine speed is increased or decreased by increasing or decreasing the opening of the engine's throttle valve, thereby obtaining large or small thrust. This allows the aircraft to climb even with a heavy load. It also enables emergency climbs to avoid obstacles. Furthermore, the propeller pitch angle is set to be 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, the lift is proportional to the wind speed acting on the propeller, so when the engine rotates at high speed, the lift is large, and when it rotates at low speed, the lift is small. On the other hand, the 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 rotation speed and decreasing the pitch angle at high rotation speed, it is possible to achieve almost the same lift. Therefore, in aircraft attitude control, the tilt of the aircraft when operating at high rotation speed and moving forward can be made approximately the same as the tilt when operating at low rotation speed and moving forward. When correcting the aircraft's attitude, the same can be done in either operation.
[0013] When carrying a light load, the engine operates at a low speed, saving energy. When carrying a heavy load, the engine operates at a high speed, allowing for rapid ascent even with a heavy aircraft, and maximizing engine performance. Beyond this type of operation, high-speed rotation may also be used for emergency ascents or descents to avoid obstacles. [Brief explanation of the drawing]
[0014] [Figure 1] This flowchart shows the throttle control of an unmanned aerial vehicle, according to the present invention. [Figure 2] This flowchart shows the attitude control of an unmanned aerial vehicle according to the present invention. [Figure 3] This is a diagram illustrating the airframe and propeller of an unmanned aerial vehicle. [Figure 4] This diagram shows the pitch angle of each propeller when the aircraft is moving forward. [Figure 5] Figure 4 is a left side view of the aircraft when it is moving forward. [Figure 6] This is an explanatory diagram of the pitch angle. [Figure 7] This graph shows the relationship between the throttle opening and pitch angle of the valve according to the present invention. [Figure 8] This graph shows the relationship between engine speed and pitch angle during attitude control according to the present invention. [Figure 9] It is a graph showing the relationship between the rotational speed and torque of a general engine.
Embodiment for Carrying Out the Invention
[0015] Hereinafter, referring to the drawings, the control method of the unmanned aircraft and the unmanned aircraft according to the present invention will be described in detail.
[0016] FIG. 1 is a flowchart of the control method of the unmanned aircraft according to the present invention, showing a flowchart of the throttle control of the airframe. The unmanned aircraft 100 in this embodiment is a quadcopter, and four propellers 5 are provided on the airframe 1, and the propellers 5 are driven by an engine 4 (see FIG. 3). Further, a program for receiving commands by wireless communication from the ground and controlling each part is built into the airframe 1.
[0017] As shown in FIG. 1, S1 is a determination as to whether or not it is throttle control of the airframe. If it is YES in S1, since it is throttle control, it is determined in S10 whether or not it is an operation to raise the throttle of the airframe. As an example of this operation, there is an operation of tilting the handle forward to raise the airframe and an operation of tilting the handle backward to lower the airframe. If it is YES in S10, since it is control to increase the throttle valve, the processes of S11 and S12 are performed. S11 instructs to increase the opening degree of the throttle valve of the engine. S12 operates the engine according to the opening degree of the throttle valve. Since the throttle valve opens, the engine rotates at high speed. When the engine rotates at high speed, the propellers also rotate faster than before, so the airframe can be raised. When a heavy load is loaded on the airframe, compared with the control of increasing the pitch angle of the propellers with a constant conventional engine rotational speed, the airframe can be strongly raised by the torque of the engine.
[0018] In the case of NO in S10, control of S13 and S14 is performed. S13 instructs to reduce the opening degree of the throttle valve of the engine. S14 operates the engine according to the opening degree of the throttle valve. Since the throttle valve is closed, the engine rotates at a low speed. When the engine rotates at a low speed, the propeller also rotates at a lower speed than before, so the aircraft can descend. When a light load is carried on the aircraft, operation at low speed rotation can be applied. In that case, compared with the conventional operation with the engine rotating at medium speed and constant control, energy-saving operation can be achieved.
[0019] Figure 2 is a flowchart of a control method for an unmanned aircraft, showing a flowchart of the attitude control of the aircraft. S2 is a determination as to whether it is aircraft attitude control. If YES in S2, since it is attitude control, determinations and processes of S21 to S26 are performed. There are three elements for attitude control: the rudder, the aileron, and the elevator. In attitude control, first, the process of S20 is performed. The current engine rotation speed is grasped, and a specific value α is obtained as the pitch angle θ (refer to Figure 6, there is an explanation of the pitch angle) corresponding to the engine rotation speed. The pitch angle α is applied to the propeller that increases lift. A pitch angle β smaller than the pitch angle α is calculated and applied to the propeller that does not increase lift. β is a value obtained by subtracting a predetermined value from α.
[0020] As shown in Figure 2, in the case of being a command of the rudder (YES in S21), it branches to S24 and the aircraft turns. There are right turns and left turns for turning. For a right turn, when the propellers are P1 to P4 in a plan view (refer to 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. Then, the lift of P1 and P3 in the clockwise direction increases, and it turns to the 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. Then, the lift of P2 and P4 in the counterclockwise direction increases, and it turns to the left.
[0021] If the pitch angles of P1 to P4 are all set to the same value, the aircraft will neither turn right nor left. Depending on the engine speed at that time, if the propeller lift is greater than the load, the aircraft will ascend. If the propeller lift balances the load, the aircraft will hover. If the propeller lift is less than the load, the aircraft will descend.
[0022] If the command is for the ailerons (YES in S22), the program branches to S25 and performs a slide. 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 on P1 and P2, causing the left side of the aircraft to drop 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 rise, causing the right side to drop 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 moves in the forward and backward directions. For forward movement, the pitch angles of P2 and P3 are set to be large, and the pitch angles of P1 and P4 are set to be small. This increases the lift at the rear of the aircraft, causing it to rise, while the front of the aircraft lowers, and the aircraft moves forward. For backward movement, the pitch angles of P2 and P3 are set to be small, and the pitch angles of P1 and P4 are set to be large. This increases the lift at the front of the aircraft, causing it to rise, while the rear of the aircraft lowers, and the aircraft moves backward. Processing in S24, S25, and S26 continues.
[0024] Figure 3 is an explanatory diagram of the airframe 1 and propeller 5 of the unmanned aerial vehicle 100. The unmanned aerial vehicle 100 in this embodiment is a vertical take-off and landing quadcopter equipped with propellers P1 (clockwise), P2 (counterclockwise), P3 (clockwise), and P4 (counterclockwise). Propeller 5 has two blades. Engine 4 is an in-line 4-cylinder reciprocating engine, with throttle valves 2 for each cylinder. The propeller 5's pitch angle can be individually set by driving a linkage mechanism (not shown) with a servo motor (not shown) installed on the airframe.
[0025] Figure 4 shows the pitch angles of each propeller when the aircraft 1 is moved forward by 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 at the rear of the aircraft, causing it to rise and the front of the aircraft to drop, moving the aircraft forward. Since propeller 5 is at an angle, thrust is obtained to move forward. Specifically, the pitch angles θ are set so that θ=β for P1 and P4, and θ=α for P2 and P3, such that α>β.
[0026] Figure 5 is a left side view of the aircraft shown in Figure 4 when it is moving forward. The front of the aircraft 1 sinks down due to the small amount of lift, and the rear of the aircraft 1 rises due to the large amount of lift, causing the aircraft 1 to tilt downwards overall.
[0027] Figure 6 is an explanatory diagram of the pitch angle. As shown in the right-hand lead circle, the pitch angle 3 is the angle indicated by θ. A larger pitch angle 3 results in a larger lift. A smaller pitch angle 3 results in a smaller lift. In other words, the lift is proportional to the pitch angle. Here, since the lift is also proportional to the wind speed, the lift is larger when the propeller rotates at high speed and smaller when the propeller rotates at low speed. As shown in the left-hand lead circle, the pitch angle 3 of the propeller 5 can be set individually. The pitch angle 3 of the propeller blades is set by a servo motor and linkage mechanism installed on the aircraft body 1.
[0028] Figure 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 to rise to the right with respect to the load. When a heavy load is loaded, the throttle valve opening is increased, and when a light load is loaded, the throttle valve opening is decreased. When the aircraft ascends and descends, if the pitch angles of propellers P1 to P4 (circled B) are all the same and fixed, increasing the engine speed will increase the propeller speed and the aircraft will ascend rapidly vertically. Decreasing the engine speed will decrease the propeller speed and the aircraft will descend vertically. When the aircraft is moving forward, the propeller pitch angles of P1 and P4 at the front of the aircraft and P2 and P3 at the rear of the aircraft are set differently, so for example, if the engine speed is increased, the aircraft will ascend from horizontal to diagonally upward. In that case, since forward attitude control is maintained, the pitch angle adjustment, which matches the engine speed indicated by S20, is performed as needed.
[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 engine is operating at high speed, the pitch angle is set to be smaller than when it is rotating at low speed. Specifically, for propellers that increase lift, pitch angle θ is set to α, and for propellers that decrease lift, pitch angle θ is set to β. When the engine speed is low and the engine is operating at low speed, the pitch angle is set to be larger than when it is rotating at high speed. For propellers that increase lift, pitch angle θ is set to α', and for propellers that decrease lift, pitch angle θ is set to β'. [Industrial applicability]
[0030] The present invention is suitable as a control method for unmanned aerial vehicles that allows for rapid ascent by increasing engine speed when carrying a heavy load, and for energy-efficient operation by lowering engine speed when carrying a light load. [Explanation of Symbols]
[0031] 1 unit 2 Throttle valve 3 Pitch angle 4 engines 5 propellers 100 Unmanned Aircraft
Claims
1. A control method for a vertical takeoff and landing unmanned aerial vehicle equipped with multiple propellers driven by engines, wherein the pitch angle of each propeller can be set individually, When controlling the aircraft's throttle, the opening of the throttle valve of the engine is increased or decreased, thereby increasing or decreasing the rotational speed of the engine, and thus increasing or decreasing the rotational speed of each propeller. A control method for unmanned aerial vehicles, characterized in that, during attitude control of the aircraft, the pitch angle of each propeller for obtaining lift is set to be large when the engine speed is low and small when the engine speed is high.
2. The control method for an unmanned aerial vehicle according to claim 1, characterized in that when a heavy load is loaded, the engine is operated at high speed, and when a light load is loaded, the engine is operated at low speed.