A power system for increasing the endurance of a drone

Abstract

The application relates to a power system for increasing the flight time of a drone, which comprises the following steps: S1, determining the total maximum pulling force of all rotors according to the take-off weight of an electric multi-rotor drone; S2, determining the maximum pulling force of each rotor according to the total maximum pulling force of all rotors and the total number of rotors; S3, determining the motor type and initially determining the rotor size according to the maximum pulling force of each rotor; S4, increasing the rotor size on the basis of the initially determined rotor size, and then obtaining a rotor size amplification coefficient; S5, determining a reduction ratio according to the rotor size amplification coefficient; S6, designing a speed reducer according to the determined reduction ratio; and S7, installing the speed reducer between each motor and each rotor. The application improves the economy of the drone.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft technology, in particular to a power system for increasing the flight time of a UAV, and a UAV using the power system. BACKGROUND

[0002] A UAV is a general term for unmanned aerial vehicles, which are equipped with automatic pilots, program control devices and other equipment, and can be operated and controlled by ground station terminals or remote controls. Compared with manned aircraft, it has the advantages of small size, low cost and easy use. It can take off vertically, can be automatically launched and landed, and can be repeatedly used, and has been widely used in various industries.

[0003] At present, for electric multi-rotor UAVs mainly used for spraying operations, in order to increase the load capacity and flight time, larger size rotors are needed to provide greater lift. However, the current design method is to connect the rotor and the motor directly, so that larger size rotors require larger power, larger torque and larger lift motors. As a result, with the increase of rotor size, the motor power increases exponentially, and accordingly, larger capacity and heavier batteries are needed, resulting in a synchronous increase in the weight of the UAV itself. The disadvantage of this power system is that the ultimate increase in load capacity or flight time is not proportional to the total cost, that is, as the power increases, it becomes less and less economical, and the cost performance becomes worse and worse.

[0004] For other applications of UAVs, such as reconnaissance UAVs, camera UAVs, etc., the above problems exist, and the economic performance of the UAV has become a bottleneck restricting the development of the industry. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the above-mentioned prior art, and to provide a power system for increasing the flight time of a UAV, in particular a power system for increasing the flight time of an electric multi-rotor UAV.

[0006] The technical solution adopted by the present application is to increase a speed reducer on the basis of the direct connection of the motor and the rotor of the existing electric multi-rotor UAV, so that the motor and the rotor are no longer directly connected, but each motor and each rotor are connected through a speed reducer, which comprises:

[0007] S1: determining the total maximum pull of all rotors according to the takeoff weight of the UAV;

[0008] The total maximum pull of all rotors is generally about twice the takeoff weight.

[0009] S2: determining the maximum pull of each rotor according to the total maximum pull of all rotors and the total number of rotors;

[0010] The maximum pull of each rotor is the total maximum pull of all rotors divided by the total number of rotors.

[0011] S3: Determine the motor model according to the maximum pull of each rotor and preliminarily determine the rotor size for the first time;

[0012] The determination of the motor model according to the maximum pull of each rotor and the preliminary determination of the rotor size for the first time is the selection of the motor and the rotor size recommended by the manufacturer.

[0013] S4: Increase the rotor size on the basis of the preliminarily determined rotor size for the first time, and then obtain a rotor size amplification factor;

[0014] The increase of the rotor size refers to the selection of a rotor larger than the preliminarily determined rotor size for the first time within the size range allowed by the entire unmanned aerial vehicle system, that is, the second-determined rotor size. Assuming that the rotor size amplification factor of the second-determined rotor size after the increase of the size divided by the preliminarily determined rotor size for the first time is K1, then K1>1.

[0015] S5: Determine a reduction ratio according to the rotor size amplification factor;

[0016] According to the rotor size amplification factor K1, a reduction ratio K2 is determined.

[0017] S6: Design a reduction ratio according to the determined reduction ratio;

[0018] According to the determined reduction ratio K2, a reduction ratio is designed. Preferably, a synchronous gear and a synchronous belt reduction ratio are used; the reduction ratio can also be a gear transmission reduction ratio or a belt transmission reduction ratio.

[0019] S7: Install the reduction ratio between each motor and each rotor, and each motor drives the corresponding rotor to provide lift through the reduction ratio.

[0020] The reduction ratio K2 is installed between each motor and each rotor, that is, the rotation speed of each rotor and the corresponding motor is determined by the reduction factor K2, the rotation speed of the motor is high, and the rotation speed of the corresponding rotor is low. The rotation speed of the motor divided by the rotation speed of the corresponding rotor is equal to the reduction ratio K2.

[0021] Step S7 specifically includes:

[0022] T1, if it is required to keep the pull unchanged and the power to decrease in the case that all rotors are changed to the large-size rotors with the rotor size amplification factor K1, the reduction ratio of the reduction ratio is That is, K2 is equal to the square of K1.

[0023] T2, if the power needs to be kept unchanged and the pull force increased when all the rotors are changed to the large-size rotors with the rotor size amplification coefficient K1, the reduction ratio of the reduction gear is i.e. K2 is equal to the 5th power of K1 and then the 3rd root.

[0024] T3, if the power needs to be reduced and the pull force increased when all the rotors are changed to the large-size rotors with the rotor size amplification coefficient K1, the reduction ratio of the reduction gear is i.e. K2 is between and .

[0025] Step S7 specifically further comprises:

[0026] T4, a reduction gear with the reduction ratio K2 is installed between each motor and each rotor;

[0027] T5, each motor is directly connected with the input shaft of each reduction gear with the reduction ratio K2, and each rotor is directly connected with the output shaft of each reduction gear with the reduction ratio K2.

[0028] T6, it is determined whether the rotation direction of each motor needs to be changed so that the rotation direction of each rotor remains unchanged compared with the rotation direction of the rotor before the reduction gear is used. Since the reduction gear is used, the rotation direction of each rotor is the same as the rotation direction of the output shaft of the reduction gear, but can be opposite to the rotation direction of the input shaft of the reduction gear, i.e. can be opposite to the rotation direction of each motor. The rotation direction of each motor is changed as needed, so that the rotation direction of each rotor after the reduction gear is used remains unchanged.

[0029] The single-rotor pull force and torque formula of the application is:

[0030]

[0031] wherein: C T , K T is the pull force coefficient, p is the air density, N is the motor speed per minute, D is the rotor diameter, C M , K M is the torque coefficient.

[0032] When the rotor diameter is D1 and the maximum pull force output is generated, the corresponding speed (N1) is as follows according to the moment and torque model formula:

[0033] T max = K T N1 2 D1 4 (3)

[0034] M max = K M N1 2 D1 5 (4)

[0035] P max = M max 2πN1 (5)

[0036] The rotor size amplification coefficient is K1 after replacing the rotor, and the large-size rotor diameter is D2=K1D1.

[0037] A reducer with a reduction ratio of K2 is determined, so that the rotor end speed is:

[0038]

[0039] The actual pull and torque of the rotor end are

[0040]

[0041] The torque converted to the motor end is:

[0042]

[0043] The motor end power is:

[0044]

[0045] The beneficial effects of the present application are:

[0046] First, the power of the motor is reduced under the condition that the output pull is unchanged, thereby increasing the flight time.

[0047] Formula (7) shows that under the condition that the maximum pull is unchanged,

[0048] The actual motor end power is

[0049]

[0050] P r_new is less than the original maximum power P max , so the flight time can be increased under the condition that the system energy capacity is unchanged.

[0051] Second, the pull is increased under the condition that the motor output power is unchanged.

[0052] Formula (10) shows that under the condition that the actual motor end power is unchanged,

[0053] Formula (7) shows that

[0054]

[0055] Third, both can increase the tension, while reducing power.

[0056] When selecting ,

[0057]

[0058] The existing power system is directly connected between each motor and each rotor, that is, the rotation speed of each rotor and the corresponding motor is strictly equal, the flight time is increased by increasing the battery capacity, and the increase of the battery capacity will also increase the weight of the unmanned aerial vehicle, so that the unmanned aerial vehicle with increased flight time cannot be designed ideally. The power system applied to the unmanned aerial vehicle of the application can effectively increase the flight time of the unmanned aerial vehicle and improve the economy of the unmanned aerial vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 It is a six-axis heterogeneous multi-rotor unmanned aerial vehicle;

[0060] Figure 2 It is a structure diagram of the prior art unmanned aerial vehicle without a speed reducer connected between the motor and the rotor;

[0061] Figure 3 It is a structure diagram of the motor and the rotor provided by the embodiment of the application, which is connected by a speed reducer;

[0062] In the drawings, the components represented by each reference numeral are listed as follows:

[0063] 1-body, 2-landing gear, 3-long arm, 4-short arm, 5-motor, 6-rotor, 7-spraying device. 11-arm, 12-motor, 13-rotor. 21-arm, 22-motor, 23-1 small gear number synchronous pulley of the speed reducer, 23-2 synchronous belt of the speed reducer, 23-3 large gear number synchronous pulley of the speed reducer, 24-rotor. DETAILED DESCRIPTION

[0064] The principle and characteristics of the application will be described below with reference to a six-axis heterogeneous multi-rotor unmanned aerial vehicle as an example, and the examples are only used to explain the application and not to limit the scope of the application. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0065] As Figure 1As shown, the embodiment is based on a six-axis heterogeneous multi-rotor plant protection unmanned aerial vehicle, which comprises a body 1, a landing gear 2, two long arms 3, two short arms 4, six motors 5 and six rotors 6. The two short arms 4 are arranged in line on the front and rear sides of the body, with one end fixed to the body and the other end provided with a motor and a rotor assembly. The bottom of the rotor assembly is provided with a spraying device. The two long arms 3 are arranged in line on the left and right sides of the body, comprising an inner section connected to the body and an outer section away from the body. The inner section and the outer section are each provided with a motor and a rotor assembly. The bottom of the rotor assembly on the two long arms 3 is provided with a spraying device.

[0066] S1: Determine the total maximum pull of all rotors according to the take-off weight of the electric multi-rotor unmanned aerial vehicle.

[0067] The total maximum pull of all rotors is generally about twice the take-off weight. The take-off weight of this heterogeneous multi-rotor unmanned aerial vehicle is 28 kg self-weight plus 16 kg load, a total of 44 kg. The maximum pull of all rotors is designed to be twice the weight of 44 kg: 88 kg.

[0068] S2: Determine the maximum pull of each rotor according to the total maximum pull of all rotors and the total number of rotors;

[0069] The maximum pull of each rotor is the total maximum pull of all rotors divided by the total number of rotors.

[0070] The maximum pull of all rotors is designed to be 88 kg, and the maximum pull of each rotor of the 6 rotors is 88÷6=14.7 kg.

[0071] S3: Determine the motor model and initially determine the rotor size according to the maximum pull of each rotor;

[0072] The determination of the motor model and the initial determination of the rotor size according to the maximum pull of each rotor is according to the classic method, i.e. the motor and rotor size recommended by the manufacturer.

[0073] The motor selected is a commercially available model, each motor is equipped with a rotor with a diameter of 30 inches, which can generate a maximum pull of T max =11 kg. Thus, the total maximum pull of the 6 rotors is 66 kg, which is less than the design requirement of 88 kg.

[0074] S4: appropriately increase the rotor size based on the initially determined rotor size, and then obtain a rotor size amplification factor;

[0075] The second determined rotor size after increasing the size is 47 inches, and the rotor size amplification factor is

[0076] S5: According to the rotor size amplification factor, determine a deceleration ratio factor;

[0077] According to the rotor size amplification factor K1, determine a decelerator with a deceleration ratio K2.

[0078]

[0079] The larger K2 is, the closer it is to The more power is saved; the smaller K2 is, the closer it is to The greater the lifting force is. K2 = 2.2, i.e. a decelerator with a ratio of 2.2:1.

[0080] S6: Design a decelerator according to the determined deceleration ratio;

[0081] Design a decelerator according to the determined deceleration ratio K2. Use a synchronous gear and a synchronous belt decelerator. Use one-stage deceleration, which requires two synchronous gears with 10 teeth and 22 teeth, respectively.

[0082] S7: Install the decelerator between each motor and each rotor, and each motor drives the respective rotor to provide lift through the decelerator.

[0083] Install a decelerator with a deceleration ratio K2 = 2.2 between each motor and the respective rotor;

[0084] Each motor is directly connected to the input shaft (10-tooth gear) of the respective decelerator with a deceleration ratio K2, and each rotor is directly connected to the output shaft (22-tooth gear) of the respective decelerator with a deceleration ratio K2. Due to the synchronous gear deceleration method, the rotation direction of each rotor remains unchanged after the decelerator is used without the need to change the rotation direction of each motor.

[0085] The actual lifting force at the rotor end of a single rotor is

[0086]

[0087] The torque of a single rotor converted to the motor end is:

[0088]

[0089] The motor end power of a single rotor is:

[0090]

[0091] Formula (11) shows that when the maximum tension increases to about twice (14.7 kg), formula (13) shows that the actual power at the motor end decreases to about 0.887 times, and under the condition that the system energy capacity is unchanged, the flight time can be increased.

[0092] The present application effectively solves the problem that the increased load capacity or flight time is not proportional to the total cost in the prior art. The present application can increase the flight time on the basis of keeping the tension unchanged, or can increase the lift under the condition of keeping the power unchanged, or can increase the flight time on the basis of reducing the power while increasing the lift, thereby greatly increasing the flight time of the unmanned aerial vehicle under the condition that the system energy (battery capacity) is unchanged, and improving the economy of the existing unmanned aerial vehicle.

Claims

1. A power system to increase the endurance of a drone, characterized in that, The method comprises: S1: determining the total maximum pulling force of all rotors (6, 13, 24) according to the take-off weight of the unmanned aerial vehicle; S2: determining the maximum pulling force of each rotor (6, 13, 24) according to the total maximum pulling force of all rotors (6, 13, 24) and the total number of rotors (6, 13, 24); The maximum pulling force of each rotor (6, 13, 24) is the total maximum pulling force of all rotors (6, 13, 24) divided by the total number of rotors (6, 13, 24); S3: determining the motor (5) model and the first primary rotor (6, 13, 24) size according to the maximum pulling force of each rotor (6, 13, 24); S4: increasing the rotor (6, 13, 24) size based on the first primary rotor (6, 13, 24) size, i.e. determining the second rotor (6, 13, 24) size, and then obtaining a rotor (6, 13, 24) size amplification factor, the rotor size amplification factor of the second rotor (6, 13, 24) size divided by the first primary rotor (6, 13, 24) size is K1, K1>1; S5: determining a reduction ratio according to the rotor (6, 13, 24) size amplification factor; determining a reducer with a reduction ratio of K2 according to the rotor size amplification factor K1; If it is desired to maintain the pull force constant and the power to decrease in the case where all the rotors are changed to large-size rotors with a rotor size amplification factor K1, the reduction ratio of the reduction gear is i.e. K2 is equal to the square of K1; If it is desired to maintain the power unchanged and the pull force increased in the case where all the rotors are changed to large-size rotors with a rotor size amplification factor K1, the reduction ratio of the reduction gear is i.e. K2 is equal to the 5th power of K1 raised to the 3rd root; If it is desired to maintain the power reduction and the increase in the pull force in the case where all the rotors are changed to large-size rotors having a rotor size amplification factor of K1, the reduction ratio of the speed reducer is i.e. K2 is between and ​ S6: designing the reducer according to the determined reduction ratio; S7: installing the reducer between the motor (22) of the unmanned aerial vehicle and the rotor (6, 13, 24), the motor (22) drives the respective rotor (6, 13, 24) to provide lift through the reducer (23-1, 23-2, 23-3).

2. The power system of claim 1, wherein, The step S3 specifically comprises: The determination of the motor (5) model and the first primary rotor (6, 13, 24) size according to the maximum pulling force of each rotor (6, 13, 24) is performed according to the recommended motor (5) and rotor (6, 13, 24) size of the manufacturer.

3. The power system of claim 2, wherein, The step S4 specifically comprises: The increase of the rotor (6, 13, 24) size is limited within the size range allowed by the entire unmanned aerial vehicle system.

4. The power system of claim 3, wherein, The step S6 specifically comprises: The reducer adopts a gear transmission reducer or a belt transmission reducer.

5. The power system of claim 4, wherein, The reducer comprises a small-tooth synchronous pulley (23-1), a synchronous belt (23-2), and a large-tooth synchronous pulley (23-3).

6. A power system for increasing the endurance of a UAV according to any one of claims 4-5, wherein, The step S7 specifically comprises: Each motor is installed with a reducer with a reduction ratio of K2 between the motor and the rotor; Each motor is directly connected to the input shaft of the reducer with a reduction ratio of K2, and each rotor is directly connected to the output shaft of the reducer with a reduction ratio of K2.

7. The power system of claim 6, wherein the fuel cell is a hydrogen fuel cell. It is determined whether the rotation direction of each motor (22) needs to be changed, so that the rotation direction of each rotor (6, 13, 24) remains unchanged compared with the rotation direction of the rotor (6, 13, 24) before the reducer (23-1, 23-2, 23-3) is not used.

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