Thrust generating device
Patent Information
- Application Number
- JP2022143525
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-09-09
- Publication Date
- 2025-01-28
- Estimated Expiration
- 2042-09-09
AI Technical Summary
Existing rotary wing aircraft face challenges in generating sufficient thrust while maintaining low propeller rotation speeds to reduce noise, as large propellers increase weight and noise reduction methods limit thrust capacity.
A thrust generating device that controls propeller rotation speed and blade pitch angle to manage thrust, switching between two control modes: maintaining a reference speed for low noise and increasing speed for higher thrust when needed, with an actuator adjusting blade pitch to optimize thrust generation.
The system effectively reduces noise and achieves required thrust levels by dynamically adjusting propeller speed and pitch, ensuring efficient thrust generation without excessive weight or noise.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to a thrust generating device that generates a thrust in a vertical direction. [Background technology]
[0002] Patent Document 1 discloses a rotorcraft, in which a controller (processor) generates a desired thrust by controlling the pitch angle of each blade of the propeller while maintaining the rotation speed of the propeller constant. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] U.S. Pat. No. 10,336,436 Summary of the Invention [Problem to be solved by the invention]
[0004] According to the rotorcraft of Patent Document 1, noise can be reduced by maintaining the propeller rotation speed at a low speed. However, when the propeller is maintained at a low speed, the upper limit of thrust is small, and it may not be possible to meet the demand for thrust. By making the propeller itself larger, the upper limit of thrust is increased. However, a large propeller is heavy, and the weight of the aircraft increases.
[0005] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]
[0006] One aspect of the present invention is a thrust generating device comprising a propeller having one or more blades and generating vertical thrust on an aircraft, a motor to rotate the propeller, an actuator to change the pitch angle of each of the blades, and a controller to control the rotation speed of the propeller by controlling the motor and to control the pitch angle of each of the blades by controlling the actuator, wherein the controller executes one of a first control that controls thrust by changing the pitch angle of each of the blades while maintaining the rotation speed of the propeller at a reference value, and a second control that is capable of generating a thrust greater than that generated by the first control by increasing the rotation speed of the propeller above the reference value. Effect of the Invention
[0007] According to the present invention, it is possible to reduce the chances of noise generation and obtain the required thrust. [Brief description of the drawings]
[0008] [Figure 1] FIG. 1 is a configuration diagram of a thrust generating device. [Diagram 2] FIG. 2 is a functional block diagram of the control unit in the first embodiment. [Diagram 3] FIG. 3 is a diagram showing the relationship between the propeller rotation speed and the thrust of the VTOL rotor for each pitch angle. [Figure 4] FIG. 4 is a diagram showing the relationship between the rotation speed and torque of the propeller for each pitch angle, and also showing the rated value of the motor torque. [Diagram 5] FIG. 5 is a diagram for explaining a method of calculating the pitch angle. [Figure 6] FIG. 6 is a diagram for explaining a method for calculating the pitch angle and the rotation speed. [Figure 7] FIG. 7 is a functional block diagram of a control unit in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] [1 Configuration of thrust generating device 10] FIG. 1 is a configuration diagram of a thrust generating device 10. The thrust generating device 10 is provided in a VTOL aircraft. The VTOL aircraft has a plurality of VTOL rotors 18 and a plurality of cruise rotors. Each VTOL rotor 18 generates a vertical thrust. Each cruise rotor generates a horizontal thrust. The thrust generating device 10 controls the thrust of the VTOL rotor 18. In this embodiment, the thrust generating device 10 is provided in an electric vertical take-off and landing aircraft, a so-called eVTOL aircraft. However, the thrust generating device 10 may be provided in a VTOL aircraft other than an electric one. In addition, the thrust generating device 10 may be provided in a VTOL aircraft having a tilt rotor instead of the VTOL rotor 18 (and the cruise rotor).
[0010] The thrust generating device 10 includes a sensor group 12, a controller 14, an inverter 16, and a VTOL rotor 18. The VTOL rotor 18 includes a motor 20, an actuator 22, a variable pitch mechanism 24, and a propeller 26. The propeller 26 includes one or more blades 28.
[0011] The sensor group 12 includes a plurality of sensors that detect the behavior of the eVTOL aircraft. For example, the sensor group 12 includes a plurality of angular velocity sensors, a plurality of acceleration sensors, and a velocity sensor. Some of the angular velocity sensors and acceleration sensors detect the angular velocity and angular acceleration about the yaw axis of the eVTOL aircraft. Some of the angular velocity sensors and acceleration sensors detect the angular velocity and angular acceleration about the roll axis of the eVTOL aircraft. Some of the angular velocity sensors and acceleration sensors detect the angular velocity and angular acceleration about the pitch axis of the eVTOL aircraft. The velocity sensor detects airspeed.
[0012] The controller 14 controls the motor 20 and the actuator 22. The controller 14 may be a flight controller of the eVTOL aircraft. Alternatively, the controller 14 may be a slave controller managed by the flight controller. Alternatively, the controller 14 may include both a flight controller and a slave controller. The controller 14 has a control unit 30, a memory unit 32, a motor driver 34, and an actuator driver 36.
[0013] The control unit 30 has a processing circuit. The processing circuit may be a processor such as a CPU or a GPU. The processing circuit may be an integrated circuit such as an ASIC or an FPGA. The processor can execute various processes by executing a program stored in the storage unit 32. At least a part of the processes may be executed by an electronic circuit including a discrete device.
[0014] The storage unit 32 has a volatile memory and a non-volatile memory. Examples of the volatile memory include RAM. The volatile memory is used as a working memory of the processor. The volatile memory temporarily stores data required for processing or calculation. Examples of the non-volatile memory include ROM and flash memory. The non-volatile memory is used as a storage memory. The non-volatile memory stores programs, tables, maps, etc. At least a part of the storage unit 32 may be provided in the processor, integrated circuit, etc. as described above.
[0015] The non-volatile memory stores a reference value for the rotation speed of each propeller 26. The reference value is the rotation speed of the propeller 26 maintained in a first control described below. The reference value is set based on the viewpoints of reducing noise generated by the rotation of the propeller 26 and generating a required thrust. The non-volatile memory also stores a pitch angle calculation map 38. The pitch angle calculation map 38 will be described below in [2-2].
[0016] The motor driver 34 outputs an on / off signal to each switching element of the inverter 16 in response to a motor control signal output from the control unit 30. The actuator driver 36 supplies power to the actuator 22 in response to an actuator control signal output from the control unit 30.
[0017] The inverter 16 has an inverter circuit. The inverter circuit has a plurality of switching elements. A primary terminal of the inverter circuit is connected to a power source (not shown). A secondary terminal of the inverter circuit is connected to the motor 20. The inverter circuit can convert DC power output from the power source into AC power and output it to the motor 20.
[0018] The motor 20 is, for example, a three-phase motor. A rotating shaft of the motor 20 is connected to a hub of a propeller 26. The motor 20 rotates the propeller 26. The actuator 22 operates the variable pitch mechanism 24 to change the pitch angle of each blade 28.
[0019] [2 First embodiment] [2-1 Functions of the control unit 30] FIG. 2 is a functional block diagram of the control unit 30 in the first embodiment. The control unit 30 can execute one of the first control and the second control as the thrust control. The control unit 30 can also switch from the first control to the second control and from the second control to the first control as appropriate. In the first control, the control unit 30 controls the thrust by changing the pitch angle of each blade 28 while maintaining the rotation speed of the propeller 26 at a reference value. In the second control, the control unit 30 generates a thrust larger than the thrust generated in the first control by increasing the rotation speed of the propeller 26 above the reference value. The control unit 30 executes the first control as much as possible, and switches from the first control to the second control only when the required thrust cannot be obtained in the first control. Note that the "thrust" used in this specification means a thrust in the vertical direction unless otherwise specified.
[0020] The control unit 30 has a function of executing a first control and a second control as thrust control. As an example, the control unit 30 executes a program stored in the storage unit 32 to function as a thrust calculation unit 40, a pitch angle calculation unit 42, a pitch angle control unit 44, a rotation speed determination unit 46, and a rotation speed control unit 48.
[0021] The thrust calculation unit 40 calculates the required thrust in response to the operation command. This thrust value is called a thrust requirement value. The operation command is output based on, for example, the operation of a control stick. The operation command is also output by an autopilot system or the like. An equation or map for calculating the thrust is stored in the memory unit 32.
[0022] The pitch angle calculation unit 42 obtains the thrust requirement value from the thrust calculation unit 40, and obtains a reference value of the rotation speed of the propeller 26 from the storage unit 32. The pitch angle calculation unit 42 calculates the pitch angle of the blades 28 and the rotation speed of the propeller 26 to obtain the thrust requirement value. For example, the pitch angle calculation unit 42 uses the pitch angle calculation map 38 stored in the storage unit 32. The calculation of the pitch angle and the rotation speed will be described below in [2-2].
[0023] The pitch angle control unit 44 obtains the calculated value of the pitch angle from the pitch angle calculation unit 42. The pitch angle control unit 44 outputs an actuator control signal to the actuator driver 36 to bring the pitch angle of the blades 28 closer to the calculated value of the pitch angle calculation unit 42. The pitch angle control unit 44 may perform feedback control, for example, using the calculated value of the pitch angle calculation unit 42 as a target value.
[0024] The rotation speed determination unit 46 acquires the calculated value of the rotation speed from the pitch angle calculation unit 42, and acquires a reference value of the rotation speed of the propeller 26 from the storage unit 32. The rotation speed determination unit 46 determines the rotation speed of the propeller 26 based on the calculation result of the pitch angle calculation unit 42. When the pitch angle calculation unit 42 does not calculate a rotation speed that exceeds the reference value, the rotation speed determination unit 46 sets the rotation speed of the propeller 26 to the reference value. In this way, the first control is executed. On the other hand, when the pitch angle calculation unit 42 calculates a rotation speed that exceeds the reference value, the rotation speed determination unit 46 sets the rotation speed of the propeller 26 to the calculated value of the pitch angle calculation unit 42. In this way, the second control is executed.
[0025] The rotation speed control unit 48 obtains the determined value of the rotation speed from the rotation speed determination unit 46. The rotation speed control unit 48 outputs a motor control signal to the motor driver 34 in order to bring the rotation speed of the propeller 26 closer to the determined value of the rotation speed determination unit 46. The rotation speed control unit 48 may perform feedback control, for example, using the determined value of the rotation speed determination unit 46 as a target value.
[0026] [2-2 Calculation of pitch angle and rotation speed using pitch angle calculation map 38] FIG. 3 is a diagram showing the relationship between the rotation speed of the propeller 26 and the thrust of the VTOL rotor 18 for each pitch angle. In FIG. 3, each of the multiple solid lines shows the relationship between the rotation speed and thrust at different pitch angles. FIG. 4 is a diagram showing the relationship between the rotation speed and torque of the propeller 26 for each pitch angle and the rated value of the torque of the motor 20. In FIG. 4, each of the multiple solid lines shows the relationship between the rotation speed and torque at different pitch angles. Also, in FIG. 4, each of the multiple broken lines shows the relationship between the rotation speed and torque at different thrusts. As shown in FIG. 3 and FIG. 4, the thrust is correlated with the pitch angle of the blade 28 and the rotation speed of the propeller 26. The pitch angle calculation map 38 associates the thrust of the VTOL rotor 18, the pitch angle of the blade 28, and the rotation speed of the propeller 26 based on this correlation.
[0027] Furthermore, in the pitch angle calculation map 38, an upper limit value (UL) of the pitch angle is set for each rotation speed. In Fig. 3 and Fig. 4, the dashed line indicates the upper limit value (UL) of the pitch angle for each rotation speed. For example, as shown in Fig. 4, the upper limit value (UL) is set to a pitch angle at which the torque of the motor 20 is smaller than the rated value (RA). That is, a predetermined torque difference is set between the torque of the motor 20 corresponding to the upper limit value (UL) and the rated value (RA). This torque difference is called the margin torque (T). Any value can be set as the upper limit value (UL). Note that in Fig. 4, the upper limit value (UL) is a constant value. Alternatively, the upper limit value (UL) may be a variable value that changes according to the change in the rotation speed. For example, in Fig. 4, the upper limit value (UL) may be a variable value that increases as the rotation speed increases. The margin torque (T) is set for the following reason. In order to increase the rotation speed of the propeller 26, a torque that overcomes the inertia is required. If the propeller 26 rotates with the pitch angle exceeding the upper limit value (UL), there will be a shortage of torque required to increase the rotation speed of the propeller 26. This will result in poor responsiveness of the propeller 26. In the first embodiment, a margin torque (T) is set to prevent poor responsiveness of the propeller 26 when it is necessary to increase the rotation speed of the propeller 26.
[0028] As described above, in the first embodiment, a reference value is set as the rotation speed of the propeller 26. Furthermore, a thrust demand value is calculated by the thrust calculation unit 40. A pitch angle calculation unit 42 calculates the pitch angle corresponding to the thrust demand value and the reference value by using the pitch angle calculation map 38.
[0029] FIG. 5 is a diagram for explaining a method for calculating the pitch angle. FIG. 5 is also a diagram for explaining the first control. For example, it is assumed that the pitch angle calculation unit 42 acquires a thrust request value (Tr1) and a reference value (Rr). The thrust request value (Tr1) and the reference value (Rr) correspond to a pitch angle (Pa1). The pitch angle (Pa1) is smaller than the upper limit value (UL1) corresponding to the reference value (Rr). In this case, the pitch angle calculation unit 42 calculates the pitch angle (Pa1) corresponding to the thrust request value (Tr1) and the reference value (Rr) by using the pitch angle calculation map 38.
[0030] FIG. 6 is a diagram for explaining a method for calculating the pitch angle and the rotation speed. FIG. 6 is also a diagram for explaining the second control. For example, it is assumed that the pitch angle calculation unit 42 acquires a thrust request value (Tr2) and a reference value (Rr). The thrust request value (Tr2) and the reference value (Rr) correspond to a pitch angle (Pa2). The pitch angle (Pa2) is greater than an upper limit value (UL1) corresponding to the reference value (Rr). In this case, the pitch angle calculation unit 42 uses the pitch angle calculation map 38 to select a combination of rotation speeds and pitch angles at which the torque is equal to or less than a predetermined value (the torque is equal to or less than the upper limit value (UL) in this embodiment) and the thrust is equal to the thrust request value (Tr2), and the combination at which the rotation speed is the smallest. The pitch angle calculation unit 42 calculates a pitch angle (Pa3) and a rotation speed (R3) as shown in FIG. 6.
[0031] The control unit 30 switches the thrust control from the first control to the second control when the state shown in Fig. 5 (first control execution state) changes to the state shown in Fig. 6 (second control start state). In the above example, the control unit 30 switches the thrust control from the first control to the second control when the thrust requirement value changes from (Tr1) to (Tr2). In this way, the control unit 30 switches the thrust control from the first control to the second control when the pitch angle corresponding to both the thrust requirement value and the reference value exceeds the upper limit value (UL) corresponding to the reference value while the first control is being executed.
[0032] Furthermore, the control unit 30 switches the thrust control from the second control to the first control when the state shown in FIG. 6 (second control execution state) changes to the state shown in FIG. 5 (first control start state). That is, the control unit 30 switches the thrust control from the second control to the first control when the thrust requirement value changes from (Tr2) to (Tr1). In this way, the control unit 30 switches the thrust control from the second control to the first control when the pitch angle corresponding to both the thrust requirement value and the reference value becomes equal to or less than the upper limit value (UL) corresponding to the reference value while the second control is being executed. Note that the condition for switching from the second control to the first control may be another condition.
[0033] According to the first embodiment, the first control is executed, thereby making it possible to suppress noise. Also, according to the first embodiment, the second control is executed in response to a large thrust requirement value, thereby making it possible to obtain a large thrust. Therefore, according to the first embodiment, it is possible to reduce the chance of noise generation, and also to obtain the required thrust.
[0034] Furthermore, according to the first embodiment, since an upper limit (UL) is set for the pitch angle, there is always a torque margin in the motor 20. Therefore, according to the first embodiment, the rotation speed of the propeller 26 can be increased quickly.
[0035] [3 Second embodiment] 7 is a functional block diagram of the control unit 30 in the second embodiment. The second embodiment is an application example of the first embodiment. In the second embodiment, the control unit 30 has a function of increasing the rotation speed of the propeller 26 in advance regardless of the required thrust value, in addition to the functions of the first embodiment. In the second embodiment, the same components as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.
[0036] The control unit 30 functions as a thrust calculation unit 40, a pitch angle calculation unit 42, a pitch angle control unit 44, a rotation speed determination unit 46, and a rotation speed control unit 48. Furthermore, the control unit 30 functions as a state determination unit 50 and a rotation speed selection unit 52.
[0037] The state determination unit 50 determines whether a state in which a large thrust is required has occurred. When it is predicted that a large thrust will be required, it is preferable to increase the rotation speed of the propeller 26 in advance. When a large thrust is required, the state determination unit 50 sets a value larger than the reference value. This value is called a correction reference value. The correction reference value may be a constant value or a variable value. The variable value may be set for each of the following cases in which a large thrust is required.
[0038] For example, if the attitude (yaw, roll, pitch) of the aircraft changes significantly, it is predicted that a large thrust will be required. The state determination unit 50 monitors the attitude of the aircraft based on the detection values of the sensor group 12. The state determination unit 50 temporarily sets a correction reference value instead of the reference value in response to the amount of yaw change per unit time exceeding a predetermined threshold (change amount threshold). The state determination unit 50 also performs the same process for roll and pitch as for yaw. This makes it possible to quickly obtain the required thrust.
[0039] For example, if the speed (airspeed) of the aircraft is significantly decreased, it is predicted that a large thrust will be required. The state determination unit 50 monitors the speed of the aircraft based on the detection value of the sensor group 12. The state determination unit 50 temporarily sets a correction reference value instead of the reference value in response to the amount of deceleration per unit time exceeding a predetermined threshold (amount of change threshold). This makes it possible to quickly obtain the required thrust.
[0040] For example, when the number of times the first control is switched to the second control reaches a frequency threshold, it is predicted that a large thrust is required. The state determination unit 50 temporarily sets a correction reference value instead of the reference value in response to the number of times the first control is switched to the second control within a predetermined time reaching the frequency threshold. This makes it possible to prevent frequent mutual switching between the first control and the second control in a short period of time.
[0041] For example, there may be cases where a pilot requires a large thrust. In this case, a switch that the pilot can operate may be provided in the cockpit. The state determination unit 50 temporarily sets the correction reference value instead of the reference value in response to the switch operation.
[0042] The rotation speed selection unit 52 acquires a reference value of the rotation speed of the propeller 26 from the memory unit 32, and acquires a correction reference value from the state determination unit 50. The rotation speed selection unit 52 selects the larger of the reference value and the correction reference value as the selected value. For example, in a state where a large thrust is not required, the state determination unit 50 does not set a correction reference value. In this case, the rotation speed selection unit 52 selects the reference value as the selected value. On the other hand, in a state where a large thrust is required, the state determination unit 50 sets a correction reference value. In this case, the rotation speed selection unit 52 selects the correction reference value as the selected value.
[0043] The pitch angle calculation unit 42 and the rotation speed determination unit 46 in the first embodiment obtain a reference value from the storage unit 32. In contrast, the pitch angle calculation unit 42 and the rotation speed determination unit 46 in the second embodiment obtain a selection value from a rotation speed selection unit 52. Except for this point, the subsequent processing in the second embodiment is the same as the processing in the first embodiment.
[0044] In the second embodiment, when a state occurs in which a large thrust is required, the state determination unit 50 sets a correction reference value larger than the reference value. As a result, the rotation speed of the propeller 26 increases. That is, in the second embodiment, when a state occurs in which a large thrust is required, the control unit 30 switches the thrust control from the first control to the second control.
[0045] According to the second embodiment, the same effects as those of the first embodiment can be obtained.
[0046] [4 Inventions Obtained from the Embodiments] The invention that can be understood from the above embodiment will be described below.
[0047] An aspect of the present invention is a thrust generating device (10) comprising a propeller (26) having one or more blades (28) for generating vertical thrust on an aircraft, a motor (20) for rotating the propeller, an actuator (22) for changing the pitch angle of each of the blades, and a controller (14) for controlling the motor to control the propeller rotation speed and for controlling the actuator to control the pitch angle of each of the blades, wherein the controller executes one of a first control for controlling thrust by changing the pitch angle of each of the blades while maintaining the propeller rotation speed at a reference value, and a second control capable of generating a thrust greater than that generated by the first control by increasing the propeller rotation speed above the reference value.
[0048] According to the above configuration, it is possible to reduce the chance of noise generation and obtain the required thrust.
[0049] In the above aspect, the controller may switch from the first control to the second control in response to a predetermined condition being satisfied while the first control is being executed, and execute the second control.
[0050] In the above aspect, the controller may switch from the first control to the second control in response to the pitch angle exceeding a predetermined upper limit value (UL), and execute the second control.
[0051] According to the above configuration, the chances of noise generation can be further reduced.
[0052] In the above aspect, the upper limit may be set to a pitch angle at which the torque of the motor is smaller than a rated value (RA).
[0053] According to the above configuration, it is possible to prevent the responsiveness of the propeller from becoming poor.
[0054] In the above aspect, the controller may switch from the second control to the first control in response to a thrust requirement value falling below a requirement threshold after switching from the first control to the second control, and execute the first control.
[0055] In the above aspect, the controller may maintain the second control regardless of the required thrust value when the number of times the first control is switched to the second control reaches a predetermined number threshold.
[0056] According to the above configuration, it is possible to prevent frequent mutual switching between the first control and the second control in a short period of time.
[0057] In the above aspect, the controller may determine a predetermined change amount threshold for an attitude change amount or a speed change amount of the aircraft, and switch from the first control to the second control when the attitude change amount or the speed change amount exceeds the change amount threshold, thereby executing the second control.
[0058] According to the above configuration, the required thrust can be obtained quickly.
[0059] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]
[0060] 10...Thrust generating device 14...Controller 20...Motor 22...Actuator 26…Propeller 28…Blade
Claims
1. A propeller having one or more blades for generating vertical thrust on the aircraft; A motor that rotates the propeller; an actuator for varying the pitch angle of each of the blades; a controller that controls the motor to control the rotational speed of the propeller and the actuator to control the pitch angle of each of the blades; A thrust generating device comprising: The controller executes one of a first control that controls thrust by changing the pitch angle of each of the blades while maintaining the rotation speed of the propeller at a reference value, and a second control that can generate a thrust greater than the thrust generated by the first control by increasing the rotation speed of the propeller above the reference value.
2. 2. The thrust generating device according to claim 1, The controller switches from the first control to the second control in response to a predetermined condition being satisfied while the first control is being executed, and executes the second control.
3. 3. The thrust generating device according to claim 2, The controller switches from the first control to the second control in response to a pitch angle exceeding a predetermined upper limit value, and executes the second control.
4. 4. The thrust generating device according to claim 3, A thrust generating device, wherein the upper limit value is set to a pitch angle such that the torque of the motor is smaller than a rated value.
5. 5. The thrust generating device according to claim 3 or 4, A thrust generating device, wherein the controller switches from the second control to the first control in response to a thrust requirement value falling below a predetermined requirement threshold after switching from the first control to the second control, and executes the first control.
6. 6. The thrust generating device according to claim 5, The controller maintains the second control regardless of the thrust requirement value in response to a predetermined threshold value being reached by a number of times of switching from the first control to the second control.
7. 3. The thrust generating device according to claim 2, The controller monitors an attitude change amount or a speed change amount of the aircraft, and switches from the first control to the second control when the attitude change amount or the speed change amount exceeds a change amount threshold, thereby executing the second control.