Thrust producing device

Abstract

A thrust generating device is provided. A controller (14) of the thrust generating device (10) executes one of a first control and a second control, wherein in the first control, a thrust is controlled by varying a pitch angle of each blade (28) while maintaining a rotational speed of a propeller (26) at a reference value, and in the second control, a thrust greater than that generated in the first control can be generated by making the rotational speed of the propeller (26) greater than the reference value. Accordingly, the opportunity of generating noise can be reduced and a required thrust can be obtained.

Description

Technical Field

[0001] The present invention relates to a thrust generating device for generating vertical thrust. Background Technology

[0002] U.S. Patent No. 10,336,436 discloses a rotorcraft. In this rotorcraft, a controller (processor) generates the desired thrust by maintaining the rotational speed of the propeller at a constant speed while controlling the pitch angle of each blade of the propeller. Summary of the Invention

[0003] According to the specification of U.S. Patent No. 10,336,436, noise can be reduced by maintaining the propeller's rotational speed at a low speed. However, when the propeller is maintained at a low speed, the upper limit of thrust decreases, sometimes failing to meet thrust requirements. Increasing the propeller size increases the upper limit of thrust. However, a larger propeller results in a heavier fuselage.

[0004] The purpose of this invention is to solve the above-mentioned technical problems.

[0005] The present invention provides a thrust generating device comprising a propeller, a motor, an actuator, and a controller. The propeller has one or more blades for generating vertical thrust on the fuselage. The motor rotates the propeller. The actuator changes the pitch angle of each blade. The controller controls the propeller's rotational speed by controlling the motor and controls the pitch angle of each blade by controlling the actuator. The controller performs one of a first control and a second control. In the first control, thrust is controlled by changing the pitch angle of each blade while maintaining the propeller's rotational speed at a reference value. In the second control, a greater thrust than that generated in the first control can be generated by making the propeller's rotational speed greater than the reference value.

[0006] According to the present invention, the chance of noise generation can be reduced, and the required thrust can be obtained.

[0007] The above-described objectives, features, and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a structural diagram of the thrust generating device.

[0009] Figure 2This is a functional block diagram of the control unit in the first embodiment.

[0010] Figure 3 It is a graph showing the relationship between the propeller speed and the thrust of the VTOL rotor at each pitch angle.

[0011] Figure 4 It is a graph that shows the relationship between propeller speed and torque at each pitch angle, and also shows the rated torque of the motor.

[0012] Figure 5 This is a diagram used to illustrate the method for calculating pitch angle.

[0013] Figure 6 This is a diagram used to illustrate the calculation methods for pitch angle and rotational speed.

[0014] Figure 7 This is a functional block diagram of the control unit in the second embodiment. Detailed Implementation

[0015] [Structure of thrust generating device 10] Figure 1 This is a structural diagram of the thrust generating device 10. The thrust generating device 10 is installed in a VTOL aircraft. The VTOL aircraft has multiple VTOL rotors 18 and multiple cruise rotors. Each VTOL rotor 18 generates thrust in the vertical direction. Each cruise rotor generates thrust in the horizontal direction. The thrust generating device 10 controls the thrust of the VTOL rotors 18. In this embodiment, the thrust generating device 10 is installed in an electric vertical takeoff and landing aircraft, also known as an eVTOL aircraft. However, the thrust generating device 10 can also be installed in a VTOL aircraft other than an electric one. Additionally, the thrust generating device 10 can also be installed in a VTOL aircraft that has a tilting rotor instead of the VTOL rotors 18 (and cruise rotors).

[0016] 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 pitch control mechanism 24, and a propeller 26. The propeller 26 has one or more blades 28.

[0017] Sensor group 12 includes multiple sensors for detecting the movements of the eVTOL aircraft. For example, sensor group 12 includes multiple angular velocity sensors, multiple acceleration sensors, and velocity sensors. A portion of the angular velocity and acceleration sensors detect the angular velocity and angular acceleration of the eVTOL aircraft about its yaw axis. A portion of the angular velocity and acceleration sensors detect the angular velocity and angular acceleration of the eVTOL aircraft about its roll axis. A portion of the angular velocity and acceleration sensors detect the angular velocity and angular acceleration of the eVTOL aircraft about its pitch axis. The velocity sensor detects airspeed.

[0018] Controller 14 controls motor 20 and actuator 22. Controller 14 can be the flight controller of an eVTOL aircraft. Alternatively, controller 14 can be a slave controller managed by the flight controller. Alternatively, controller 14 can include both the flight controller and the slave controller. Controller 14 has a control unit 30, a storage unit 32, a motor driver 34, and an actuator driver 36.

[0019] The control unit 30 has processing circuitry. This processing circuitry can be a processor such as a CPU or GPU. It can also be an integrated circuit such as an ASIC or FPGA. The processor can perform various processes by executing programs stored in the storage unit 32. At least some of these processes can be executed by electronic circuitry including discrete devices.

[0020] Storage unit 32 includes volatile memory and non-volatile memory. Examples of volatile memory include RAM (Random Access Memory). The volatile memory is used as the processor's working memory. The volatile memory temporarily stores data required for processing or computation. Examples of non-volatile memory include ROM (Read Only Memory) and flash memory. The non-volatile memory is used for storage. The non-volatile memory stores programs, diagrams, and maps. At least a portion of storage unit 32 can be provided in a processor, integrated circuit, or the like described above.

[0021] The non-volatile memory stores reference values ​​for the rotational speeds of each propeller 26. These reference values ​​refer to the rotational speeds of the propeller 26 maintained during the first control described later. The reference values ​​are set based on the viewpoints of reducing noise generated by the rotation of the propeller 26 and generating the required thrust. Additionally, the non-volatile memory stores a pitch angle calculation mapping 38. The pitch angle calculation mapping 38 will be explained in [2-2] below.

[0022] The motor driver 34, in response to the motor control signal output from the control unit 30, outputs on / off signals to each switching element of the inverter 16. The actuator driver 36, in response to the actuator control signal output from the control unit 30, supplies electrical power to the actuator 22.

[0023] Inverter 16 has an inverter circuit. The inverter circuit has multiple switching elements. The primary terminal of the inverter circuit is connected to a power source (not shown). The secondary terminal of the inverter circuit is connected to the motor 20. The inverter circuit can convert the DC power output from the power source into AC power and output it to the motor 20.

[0024] Motor 20 is, for example, a three-phase motor. The rotating shaft of motor 20 is connected to the hub of propeller 26. Motor 20 causes propeller 26 to rotate. Actuator 22 changes the pitch angle of each blade 28 by actuating pitch change mechanism 24.

[0025] [2. First Embodiment] [2-1 Function of Control Unit 30] Figure 2 This is a functional block diagram of the control unit 30 in the first embodiment. The control unit 30 can perform either the first control or the second control as thrust control. Furthermore, the control unit 30 can appropriately perform switching from the first control to the second control, and switching from the second control to the first control. In the first control, the control unit 30 controls thrust by maintaining the rotational speed of the propeller 26 at a reference value while changing the pitch angle of each blade 28. In the second control, the control unit 30 generates a greater thrust than that generated in the first control by making the rotational speed of the propeller 26 greater than the reference value. The control unit 30 performs the first control as much as possible, switching from the first control to the second control only when the required thrust cannot be obtained in the first control. Furthermore, unless otherwise specified, "thrust" as used in this specification refers to thrust in the vertical direction.

[0026] The control unit 30 performs thrust control by executing the first control and the second control. As an example, the control unit 30 functions as the thrust calculation unit 40, the pitch angle calculation unit 42, the pitch angle control unit 44, the speed determination unit 46, and the speed control unit 48 by executing the programs stored in the storage unit 32.

[0027] The thrust calculation unit 40 calculates the required thrust in response to the action command. This thrust value is called the thrust requirement value. The action command is output, for example, based on the operation of a joystick. Alternatively, the action command is output by an automatic control system, etc. The formula or mapping used to calculate the thrust is stored in the storage unit 32.

[0028] The pitch angle calculation unit 42 obtains the thrust requirement value from the thrust calculation unit 40 and the reference value of the propeller 26 rotational speed from the storage unit 32. The pitch angle calculation unit 42 calculates the pitch angle of the blade 28 and the rotational speed of the propeller 26 for obtaining the thrust requirement value. For example, the pitch angle calculation unit 42 uses the pitch angle calculation mapping 38 stored in the storage unit 32. The calculation of pitch angle and rotational speed will be explained in [2-2] below.

[0029] The pitch angle control unit 44 obtains the calculated pitch angle value from the pitch angle calculation unit 42. To make the pitch angle of the propeller blade 28 close to the calculated value of the pitch angle calculation unit 42, the pitch angle control unit 44 outputs an actuator control signal to the actuator driver 36. For example, the pitch angle control unit 44 may also use the calculated value of the pitch angle calculation unit 42 as a target value for feedback control.

[0030] The rotational speed determination unit 46 obtains the calculated rotational speed value from the pitch angle calculation unit 42 and obtains the reference value of the rotational speed of the propeller 26 from the storage unit 32. The rotational speed determination unit 46 determines the rotational speed of the propeller 26 based on the calculation result of the pitch angle calculation unit 42. If the pitch angle calculation unit 42 does not calculate a rotational speed exceeding the reference value, the rotational speed determination unit 46 uses the rotational speed of the propeller 26 as the reference value. Accordingly, first control is executed. On the other hand, if the pitch angle calculation unit 42 calculates a rotational speed exceeding the reference value, the rotational speed determination unit 46 uses the rotational speed of the propeller 26 as the calculated value of the pitch angle calculation unit 42. Accordingly, second control is executed.

[0031] The speed control unit 48 obtains a determined value of the rotational speed from the speed determination unit 46. To bring the rotational speed of the propeller 26 close to the determined value of the speed determination unit 46, the speed control unit 48 outputs a motor control signal to the motor driver 34. Alternatively, the speed control unit 48 may use the determined value of the speed determination unit 46 as a target value for feedback control.

[0032] [2-2 Calculation of pitch angle and rotational speed using pitch angle calculation] Figure 3 This is a graph showing the relationship between the rotational speed of propeller 26 and the thrust of VTOL rotor 18 at each pitch angle. Figure 3 In the diagram, multiple solid lines represent the relationship between rotational speed and thrust at different pitch angles. Figure 4This is a graph showing the relationship between the rotational speed and torque of the propeller 26 at each pitch angle, and also showing the rated torque of the motor 20. Figure 4 In the diagram, multiple solid lines represent the relationship between rotational speed and torque at different pitch angles. Additionally, in... Figure 4 In the diagram, multiple dashed lines represent the relationship between rotational speed and torque under different thrust levels. For example... Figure 3 and Figure 4 As shown, the thrust is positively correlated with the pitch angle of the blade 28 and the rotational speed of the propeller 26. The pitch angle calculation mapping 38 establishes a correspondence between the thrust of the VTOL rotor 18, the pitch angle of the blade 28, and the rotational speed of the propeller 26 based on this positive correlation.

[0033] Furthermore, in the pitch angle calculation mapping 38, an upper limit value (UL) for the pitch angle is set for each rotational speed. Figure 3 and Figure 4 In the diagram, the dashed line represents the upper limit (UL) of the pitch angle at each rotational speed. For example, as shown... Figure 4 As shown, the pitch angle at which the torque of motor 20 is less than the rated value (RA) is set as the upper limit value (UL). That is, a predetermined torque difference is set between the torque of 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). Furthermore, in Figure 4 In this context, the upper limit value (UL) is a fixed value. Alternatively, the upper limit value (UL) can be a variable value that varies according to changes in rotational speed. For example, in... Figure 4 In this embodiment, the upper limit value (UL) can be a variable value that increases with increasing rotational speed. The spare torque (T) is set for the following reasons: To increase the rotational speed of the propeller 26, a torque is needed to overcome inertia. If the propeller 26 rotates with a pitch angle exceeding the upper limit value (UL), the torque required to increase the rotational speed of the propeller 26 is insufficient. Therefore, the responsiveness of the propeller 26 deteriorates. In the first embodiment, when it is necessary to increase the rotational speed of the propeller 26, a spare torque (T) is set to prevent a deterioration in the responsiveness of the propeller 26.

[0034] As described above, in the first embodiment, a reference value is set as the rotational speed of the propeller 26. Furthermore, the thrust calculation unit 40 calculates the required thrust value. The pitch angle calculation unit 42 calculates the pitch angle corresponding to the required thrust value and the reference value using the pitch angle calculation mapping 38.

[0035] Figure 5 This is a diagram used to illustrate the method for calculating pitch angle. Figure 5This is a diagram used to illustrate the first control. For example, suppose the pitch angle calculation unit 42 obtains a thrust requirement value (Tr1) and a reference value (Rr). The pitch angle (Pa1) corresponds to the thrust requirement value (Tr1) and the reference value (Rr). The pitch angle (Pa1) is less 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 requirement value (Tr1) and the reference value (Rr) by using the pitch angle calculation mapping 38.

[0036] Figure 6 This is a diagram used to illustrate the calculation methods for pitch angle and rotational speed. Figure 6 This is a diagram used to illustrate the second control. For example, suppose the pitch angle calculation unit 42 obtains a thrust requirement value (Tr2) and a reference value (Rr). The pitch angle (Pa2) corresponds to the thrust requirement value (Tr2) and the reference value (Rr). The pitch angle (Pa2) is greater than the upper limit value (UL1) corresponding to the reference value (Rr). In this case, the pitch angle calculation unit 42 selects the combination with the smallest rotational speed from the combinations of rotational speed and pitch angle where the torque is below a specified value (in this embodiment, the torque is below the torque corresponding to the upper limit value (UL)) and the thrust is the thrust requirement value (Tr2) by using the pitch angle calculation mapping 38. Figure 6 As shown, the pitch angle calculation unit 42 calculates the pitch angle (Pa3) and rotational speed (R3).

[0037] From Figure 5 The state shown (first control execution state) becomes Figure 6 In the state shown (second control start state), the control unit 30 switches thrust control from the first control to the second control. In the example above, when the thrust requirement value changes from (Tr1) to (Tr2), the control unit 30 switches thrust control from the first control to the second control. Thus, during the execution of the first control, if 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, the control unit 30 switches thrust control from the first control to the second control.

[0038] In addition, from Figure 6 The state shown (second control execution state) becomes Figure 5In the state shown (first control start state), the control unit 30 switches thrust control from second control to first control. That is, when the thrust requirement value changes from (Tr2) to (Tr1), the control unit 30 switches thrust control from second control to first control. Thus, during the execution of second control, if the pitch angle corresponding to both the thrust requirement value and the reference value becomes below the upper limit value (UL) corresponding to the reference value, the control unit 30 switches thrust control from second control to first control. Furthermore, the switching condition from second control to first control can also be other conditions.

[0039] According to the first embodiment, noise can be suppressed by executing the first control. Furthermore, according to the first embodiment, a larger thrust can be obtained by executing the second control in response to a larger thrust requirement value. Therefore, according to the first embodiment, the chance of noise generation can be reduced, and the required thrust can be obtained.

[0040] Furthermore, according to the first embodiment, since an upper limit (UL) is set for the pitch angle, the torque of the motor 20 always has a margin of safety. Therefore, according to the first embodiment, the rotational speed of the propeller 26 can be rapidly increased.

[0041] [3 Second Implementation] Figure 7 This 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, in addition to having the functions of the first embodiment, the control unit 30 also has the function of pre-increasing the rotational speed of the propeller 26 regardless of the thrust requirement value. In the second embodiment, the same reference numerals are used for structures identical to those in the first embodiment, and their descriptions are omitted.

[0042] The control unit 30 functions as a thrust calculation unit 40, a pitch angle calculation unit 42, a pitch angle control unit 44, a speed determination unit 46, and a speed control unit 48. Furthermore, the control unit 30 functions as a status determination unit 50 and a speed selection unit 52.

[0043] The state determination unit 50 determines whether a state requiring greater thrust has occurred. If a greater thrust requirement is predicted, it is preferable to increase the rotational speed of the propeller 26 beforehand. The state determination unit 50 sets a value greater than a reference value when a greater thrust requirement is needed. This value is called a correction reference value. The correction reference value can be a fixed value or a variable value. The variable value can also be set according to the following conditions for each situation requiring greater thrust.

[0044] For example, when there are significant changes in the fuselage attitude (yaw, roll, pitch), a larger thrust is predicted to be needed. The state determination unit 50 monitors the fuselage attitude based on the detection values ​​of the sensor group 12. In response to the yaw change per unit time exceeding a predetermined threshold (change threshold), the state determination unit 50 temporarily sets a correction reference value to replace the reference value. The state determination unit 50 performs the same processing on roll and pitch as on yaw. Accordingly, the required thrust can be obtained quickly.

[0045] For example, when the airspeed of the fuselage decreases significantly, a larger thrust is predicted to be needed. The status determination unit 50 monitors the airspeed based on the detection values ​​of the sensor group 12. In response to the deceleration per unit time exceeding a predetermined threshold (change threshold), the status determination unit 50 temporarily sets a correction reference value to replace the reference value. Accordingly, the required thrust can be obtained quickly.

[0046] For example, if the number of times switching from the first control to the second control reaches a threshold, it is predicted that a larger thrust is required. In response to the threshold being reached within a specified time, the status determination unit 50 temporarily sets a correction reference value instead of the baseline value. This prevents frequent switching between the first and second control within a short period.

[0047] For example, sometimes pilots require greater thrust. In such cases, a pilot-operable switch can be installed in the cockpit. The status determination unit 50 temporarily sets a correction reference value instead of the reference value in response to the switch operation.

[0048] The speed selection unit 52 obtains a reference value for the rotational speed of the propeller 26 from the storage unit 32 and a correction reference value from the state determination unit 50. The speed selection unit 52 sets the larger of the reference value and the correction reference value as the selection value. For example, in a state where greater thrust is not required, the state determination unit 50 does not set the correction reference value. In this case, the speed selection unit 52 sets the reference value as the selection value. On the other hand, in a state where greater thrust is required, the state determination unit 50 sets the correction reference value. In this case, the speed selection unit 52 sets the correction reference value as the selection value.

[0049] In the first embodiment, the pitch angle calculation unit 42 and the rotational speed determination unit 46 obtain reference values ​​from the storage unit 32. In contrast, in the second embodiment, the pitch angle calculation unit 42 and the rotational speed determination unit 46 obtain selection values ​​from the rotational speed selection unit 52. Apart from this, the subsequent processing in the second embodiment is the same as that in the first embodiment.

[0050] In the second embodiment, when a state requiring greater thrust occurs, the state determination unit 50 sets a correction reference value greater than the reference value. As a result, the rotational speed of the propeller 26 increases. That is, in the second embodiment, when a state requiring greater thrust occurs, the control unit 30 switches the thrust control from the first control to the second control.

[0051] According to the second embodiment, the same effect as the first embodiment can be obtained.

[0052] [4. Inventions obtainable according to the embodiments] The invention described below is an invention that can be mastered based on the above embodiments.

[0053] The technical solution of the present invention is a thrust generating device (10), which has a propeller (26), a motor (20), an actuator (22), and a controller (14), wherein the propeller has one or more blades (28) for generating vertical thrust on the fuselage; the motor rotates the propeller; the actuator changes the pitch angle of each blade; the controller controls the rotational speed of the propeller by controlling the motor, and controls the pitch angle of each blade by controlling the actuator; the controller performs one of a first control and a second control, wherein, in the first control, thrust is controlled by changing the pitch angle of each blade while maintaining the rotational speed of the propeller at a reference value; in the second control, a greater thrust than that generated in the first control can be generated by making the rotational speed of the propeller greater than the reference value.

[0054] Based on the above structure, the chance of noise generation can be reduced, and the required thrust can be obtained.

[0055] In the above technical solution, the controller may switch from the first control to the second control in response to the fulfillment of a specified condition during the execution of the first control, in order to execute the second control.

[0056] In the above technical solution, the controller can switch from the first control to the second control in response to the pitch angle exceeding the specified upper limit (UL) to execute the second control.

[0057] Based on the above structure, the chance of noise generation can be further reduced.

[0058] In the above technical solution, the upper limit value can be set as the pitch angle at which the torque of the motor is less than the rated value (RA).

[0059] The above structure can prevent the propeller's responsiveness from deteriorating.

[0060] In the above technical solution, after switching from the first control to the second control, the controller switches from the second control to the first control in response to the thrust requirement value being lower than the requirement threshold, in order to execute the first control.

[0061] In the above technical solution, the controller may maintain the second control in a manner independent of the thrust requirement value in response to the number of switching from the first control to the second control reaching a predetermined threshold.

[0062] Based on the above structure, it is possible to prevent frequent switching between the first control and the second control within a short period of time.

[0063] In the above technical solution, the controller can monitor the attitude change or speed change of the fuselage, and switch from the first control to the second control in response to the attitude change or speed change exceeding the change threshold, so as to execute the second control.

[0064] Based on the above structure, the required thrust can be obtained quickly.

[0065] Furthermore, the present invention is not limited to the content disclosed above, and various structures can be adopted without departing from the spirit of the present invention.

Claims

1. A thrust generating device comprising a propeller, a motor, an actuator, and a controller, wherein, The propeller has one or more blades for generating vertical thrust on the fuselage. The motor causes the propeller to rotate; The actuator causes the pitch angle of each of the blades to change; The controller controls the propeller's rotational speed by controlling the motor, and controls the pitch angle of each blade by controlling the actuator. Its features are, The controller executes one of a first control and a second control, wherein, in the first control, thrust is controlled by varying the pitch angle of each blade while maintaining the propeller speed at a reference value; and in the second control, thrust is generated by increasing the propeller speed above the reference value to produce a greater thrust than that generated in the first control. The controller switches from the first control to the second control in response to the pitch angle exceeding a predetermined upper limit value. The upper limit value is set as the pitch angle that makes the torque of the motor less than the rated value.

2. The thrust generating device according to claim 1, characterized in that, After switching from the first control to the second control, the controller switches back to the first control in response to the thrust requirement value being lower than a predetermined requirement threshold, in order to execute the first control.

3. The thrust generating device according to claim 2, characterized in that, The controller maintains the second control in a manner independent of the thrust requirement value in response to the number of switching from the first control to the second control reaching a predetermined threshold.

4. The thrust generating device according to claim 1, characterized in that, The controller monitors the attitude change or speed change of the fuselage, and switches from the first control to the second control in response to the attitude change or speed change exceeding a threshold, thereby executing the second control.

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