Three-degree-of-freedom complete machine wind tunnel test device for multi-rotor aircraft

Abstract

The invention provides a three-degree-of-freedom complete machine wind tunnel test device for a multi-rotor aircraft, which comprises a wind tunnel test support rack, a windshield fairing, a stand column, a six-component force measuring balance and a three-degree-of-freedom test device, and is characterized in that the wind tunnel test support rack is mounted at the center of a wind tunnel flow field, and the stand column is mounted right above the wind tunnel test support rack; a wind shield fairing is further installed over the wind tunnel test supporting rack, a six-component force measuring balance is installed above the stand column, a three-degree-of-freedom test device is installed above the six-component force measuring balance, and a multi-rotor aircraft is installed above the three-degree-of-freedom test device. The three-degree-of-freedom test device realizes three-degree-of-freedom motion of pitching, yawing and rolling of the multi-rotor aircraft. The device does not interfere with one another in three degrees of freedom of pitching, yawing and rolling, the movement axes of the device can intersect at one point, the point can coincide with the mass center of the aircraft, and the free flight test of the aircraft in a wind tunnel can be well simulated.

Description

Technical Field

[0001] This invention belongs to the field of wind tunnel free-flight testing technology for multi-rotor aircraft, and particularly relates to a wind tunnel testing device for a three-degree-of-freedom multi-rotor aircraft. Background Technology

[0002] Currently, common three-degree-of-freedom (DOF) wind tunnel testing setups include ball joint type, rope-connected parallel support mechanism, and multi-DOF combination type. The ball joint type couples pitch, yaw, and roll onto a single ball joint, but its structure is too simple to restrict single- or double-DOF motion. Furthermore, its motion often combines several degrees of freedom simultaneously, making it difficult for test operators to clearly discern the trajectory. The rope-connected parallel support mechanism uses rope traction to connect the three degrees of freedom in parallel, but the rope stiffness is low, making it susceptible to deformation under wind conditions in the wind tunnel, and the rope strength is also low. This leads to a low safety factor and increased test risks. In addition, the rope needs to be straightened by the weight of the test piece, and the installation method requires the test piece to be below the rope. When the lift generated by the test piece is greater than its own weight, the rope is in a slack state, making it impossible to effectively conduct three-degree-of-freedom tests. The multi-degree-of-freedom combined structure has a more complex connection, and its large size affects the wind tunnel process. The large weight results in greater inertia, affecting the test piece's free flight test in the wind tunnel. Moreover, it is sometimes impossible to ensure that the center lines of pitch, yaw and roll intersect at a single point, which is far from the center of gravity of the test piece. This makes it impossible to better simulate the test piece's three-degree-of-freedom virtual flight test in the wind tunnel, affecting the accuracy of the test. Summary of the Invention

[0003] This invention provides a wind tunnel testing device for a three-degree-of-freedom multi-rotor aircraft. The technical solution is as follows: In a first aspect, a three-degree-of-freedom wind tunnel testing device for a multi-rotor aircraft is provided, characterized in that it comprises: a wind tunnel test support frame 2, a windshield fairing 3, a column 4, a six-component force balance 5, and a three-degree-of-freedom testing device 6. The wind tunnel test support frame 2 is installed at the center of the wind tunnel flow field. The column 4 is installed directly above the wind tunnel test support frame 2. The windshield fairing 3 is also installed directly above the wind tunnel test support frame 2. The six-component force balance 5 is installed above the column 4. The three-degree-of-freedom testing device 6 is installed above the six-component force balance 5. The multi-rotor aircraft 7 is installed above the three-degree-of-freedom testing device 6. The three-degree-of-freedom testing device 6 realizes the pitch, yaw, and roll motions of the multi-rotor aircraft 7.

[0004] Optionally, the three-degree-of-freedom wind tunnel test device 6 includes: a roll mechanism 8, a pitch mechanism 9, a yaw mechanism 10, and a fixed base 11. The fixed base 11 is fixedly connected to the upper plate of the six-component force balance 5, and the upper mounting plate of the roll mechanism device 8 is fixedly connected to the multi-rotor aircraft 7. The yaw mechanism 10, the pitch mechanism 9, and the roll mechanism device 8 are located on the fixed base 11 from top to bottom.

[0005] Optionally, the rolling mechanism 8 includes: a rotatable component rolling support 13, a rolling connecting shaft 14, an angular contact ball bearing 15, a bearing cover 17, an encoder fixing bracket 19, and a rolling encoder 18. The rolling support 13 and the rolling connecting shaft 14 are fixedly connected. The rolling connecting shaft 14 passes through the rolling support 13 and the angular contact ball bearing 15 respectively, and is then tightened by the threaded connection of the locking round nut 16. Finally, the bearing outer ring is pressed by the bearing cover 17, and finally fixed by the countersunk screw. The outer ring of the angular contact ball bearing 15 is fixedly fitted to the pitch support 22 yaw center hole of the pitch mechanism 9, and the inner ring is tightly fitted to the roll connecting shaft 14. All the above connecting parts are coaxially connected and symmetrically installed in front of and behind the roll mechanism device 8. The roll connecting shaft 14 at the rear of the roll mechanism device 8 is also connected to an encoder fixing bracket 19 and a roll encoder 18. The roll encoder 18 measures and records the change in the roll angle of the roll support 13 in real time. When the roll support 13 rolls, it will drive the roll connecting shaft 14 to move. The roll connecting shaft 14 will drive the connecting pin of the roll encoder 18 to move, so that the roll encoder 18 can collect and record the roll angle value. The limit movement angle of the roll support 13 is 45° to the left and right.

[0006] Furthermore, four rolling buffer pads 20 are symmetrically arranged at the lower part of the rolling support 13. The rolling buffer pads 20 have a central hole, and the rolling buffer pads 20 are fixed to the rolling support 13 with embedded screws in the hole. The rolling buffer pads 20 are used to reduce the inertial impact caused by the rolling support rolling to the limit position. The roll support 13 and the pitch support 22 of the pitch mechanism 9 are fixedly connected by horizontal fixed connecting screws 21. One horizontal fixed connecting screw 21 is arranged in front and behind the yaw. When the horizontal fixed connecting screw 21 is fixedly connected to the roll support 13, the roll support 13 cannot rotate and always remains in a horizontal state. The outer end of the rolling connecting shaft 14 is tightly fitted to the inner ring of the angular contact ball bearing 15. The middle part of the rolling connecting shaft 14 is tightly fitted to the lower center opening of the rolling support 13. The inner end of the rolling connecting shaft 14 is semi-circularly pressed and fitted to the rolling support 13 by countersunk screws. The angular contact ball bearing 15, the rolling connecting shaft 14, and the lower center opening of the rolling support 13 are coaxially mounted. One rolling connecting shaft 14 is installed in each of the forward and backward directions.

[0007] Optionally, the pitch mechanism 9 includes: an encoder mounting bracket 19, a pitch support 22, an angular contact ball bearing 23, a pitch connecting shaft 24, a pitch bearing cover plate 25, a pitch encoder connecting bracket 26, and a pitch encoder 27. The left and right sides of the pitch support 22 are tightly connected to two pitch connecting shafts 24 respectively. The pitch connecting shafts 24 pass through the center holes on the left and right sides of the pitch support 22, the center hole at the upper end of the yaw support 32, and the angular contact ball bearing 23 respectively. The pitch bearing cover plate 25 is fixed to the pitch connecting shaft 24, the pitch support 22, the yaw support 32, and the angular contact ball bearing 23 by screws. The pitch support 22, the lateral center hole, the angular contact ball bearing 23, the roll connecting shaft 24, and the upper center hole of the yaw support 32 are coaxially connected. The pitch connecting shaft 24 is symmetrically installed on both sides of the pitch support 22 along the heading direction. The pitch connecting shaft 24 on the left side is also connected to the pitch encoder connecting bracket 26, the encoder fixing bracket 19, and the pitch encoder 27. When the pitch support 22 pitches along the roll axis, the encoder fixing bracket 19 will pitch together. The encoder fixing bracket 19 drives the encoder connecting bracket 26 to pitch, thereby driving the pitch encoder 27 to rotate, so that the pitch encoder 27 can collect and record the pitch angle value. Furthermore, two 15-degree pitch limiting blocks 28 are symmetrically arranged in front and behind the pitch mechanism 9. The 15-degree limiting blocks 28 are fixedly installed in the pitch support 22 cavity in front and behind the pitch. When the pitch support 22 moves to its limit, because the 15-degree pitch limiting blocks 28 are low, they will first touch the pitch support 22, which will prevent its stroke from expanding and limit its pitch stroke.

[0008] Furthermore, the pitch support 22 is provided with arc-shaped grooves on its left and right sides, which can artificially restrict the pitch movement of the pitch support 22. The pitch support 22 and the yaw support 32 are adjusted and tightened or loosened by the pitch locking plate 29 and the locking nut 30 at the arc-shaped grooves, so as to achieve the desired fixed pitch angle. When the locking plate 29 and the locking nut 30 are removed, the pitch mechanism 9 can pitch freely. Four roll limit blocks 31 are symmetrically arranged in the front, back, left and right of the pitch support 22. When the roll support 13 moves to the limit, the roll buffer pad 20 will first touch the roll limit block 31, so that its stroke cannot be expanded, thus playing a limiting and protective role.

[0009] Optionally, the yaw mechanism 10 includes: a yaw support 32, a yaw encoder mounting bracket 33, a yaw encoder connecting shaft 34, a screw 37, a yaw angle encoder 38, an angular contact ball bearing 39, and a yaw connecting cover plate 40. The yaw support 32, yaw encoder mounting bracket 33, and yaw encoder connecting shaft 34 are rotatable components. The inner cavity of the yaw support 32 is tightly fitted with the outer rings of four vertically arranged angular contact ball bearings 39. The inner rings of the angular contact ball bearings 39 are tightly fitted with the fixed base 11. A yaw connecting cover plate 40 is installed at the uppermost end of the fixed base 11, and the yaw angle encoder 38 is fixed to the yaw connecting cover plate 40 by ring screws. The bottom end of the yaw encoder connecting shaft 34 is connected to the yaw angle encoder 38, and the top end is connected to the yaw encoder. Mounting bracket 33; fixed base 11, angular contact ball bearing 39, yaw support 32, yaw angle encoder 38, yaw encoder connecting shaft 34 and yaw connecting cover plate 40 are connected and installed with the same vertical rotation axis; when the yaw support 32 yaws along the axis, the yaw encoder mounting bracket 33 will also yaw. The yaw encoder mounting bracket 33 drives the yaw encoder connecting shaft 34 to yaw, thereby driving the yaw angle encoder 38 to yaw rotate, so that the yaw angle encoder 38 can collect and record the yaw angle value.

[0010] Furthermore, a yaw angle limiting block 35 and a limiting locking pad 36 are provided in the middle area between the yaw support 32 and the fixed base 11. The yaw angle limiting block 35 is set at the ±15° position with two blocks and at the 90° position with one block, so that the yaw limit can be moved within the set ±90° or ±15° range at the beginning of the test. Furthermore, the bottom circumference of the yaw support 32 is provided with several arc-shaped grooves. The yaw support 32, the limiting locking pad 36 and the fixed base 11 are fixedly connected along the arc-shaped grooves by screws 37 in an adjustable position, so as to play the role of locking the yaw angle.

[0011] The beneficial effects of this invention are at least as follows: 1. The device of the present invention does not interfere with each other in the three degrees of freedom of pitch, yaw and roll, and their axes of motion can intersect at a point that can coincide with the center of mass of the aircraft, which can better simulate the free flight test of the aircraft in the wind tunnel. 2. This invention can lock 0, 1, 2 or 3 of the 3 degrees of freedom, thereby enabling the aircraft to be tested in 3-degree-of-freedom, 2-degree-of-freedom, single-degree-of-freedom or locked states. Furthermore, the pitch, yaw and roll limit motion angles of this invention can be changed by manually replacing different components. 3. The device of the present invention is equipped with an independent six-component force balance and a three-degree-of-freedom angle encoder, which can record and store in real time the aerodynamic force and attitude angle correspondence and change law of the aircraft during the wind tunnel free flight test; 4. The device of the present invention has a simple, flexible and compact structure. Its dimensions are 185*121*175mm (length*width*height) and its weight is less than 10kg, which is much smaller than the size limit and inertia requirement of the aircraft itself. Therefore, it has little impact on the wind tunnel free flight test of the aircraft. Attached Figure Description

[0012] Figure 1 This is a wind tunnel test diagram of the three-degree-of-freedom multi-rotor aircraft of the present invention; Figure 2 This is a front view of the three-degree-of-freedom wind tunnel testing device of the present invention; Figure 3 This is an axial view of the three-degree-of-freedom wind tunnel testing device of the present invention; Figure 4 This is an axial view of the rolling mechanism of the present invention; Figure 5 This is an exploded view of the rolling mechanism of the present invention; Figure 6 This is a diagram showing the 45° limit position of the rolling mechanism of the present invention (symmetrical left and right). Figure 7 A view showing the installation of the horizontal limiting screw on the rolling mechanism of the present invention; Figure 8 This is an axial view of the pitch mechanism of the present invention; Figure 9 This is an exploded view of the pitching mechanism of the present invention; Figure 10 This is a 15° limiting diagram of the pitch mechanism of the present invention (symmetrical left and right); Figure 11 This is a diagram showing the 45° limit position of the pitch mechanism of the present invention (symmetrical left and right). Figure 12 This is a diagram showing the pitch fixed angle limiting setting of the present invention; Figure 13 This is an axis view of the yaw mechanism of the present invention; Figure 14 This is a front view of the yaw mechanism of the present invention; Figure 15 This is an exploded view of the yaw mechanism of the present invention; Figure 16 Axial view of the fixed base of the present invention Figure 17 This is an axial view of the yaw support of the present invention; Figure 18 This is a diagram showing the limiting motion of the yaw mechanism of the present invention. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0015] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] This invention designs an experimental setup that allows a model aircraft to freely pitch, yaw, and roll, and to test and record its motion attitude and aerodynamic load data in real time under various attitudes. This data is then fed back to the model's control system outside the wind tunnel, which in turn sends corrective control commands to the model's control surfaces. By continuously repeating this cycle, the model achieves free flight and control within the wind tunnel, thereby verifying and evaluating the performance of the aircraft and its control system.

[0018] This invention relates to a three-degree-of-freedom wind tunnel testing device for multi-rotor aircraft, mainly composed of a support structure, a rotation mechanism, and a force measurement system. The support structure, made of high-strength alloy structural steel and optimized in design, possesses excellent stability and rigidity, capable of withstanding various loads during testing. Its unique frame structure not only ensures the overall strength of the device but also facilitates the installation of components and reduces wind resistance. The rotation mechanism includes motion components in the yaw, lateral, and vertical directions, respectively enabling precise movement of the test model in the roll, pitch, and yaw directions. It can rotate independently or couple movements in multiple directions. Each motion component uses high-precision bearings to ensure smooth and accurate movement. The design of the rotation mechanism fully considers the installation and adjustment requirements of the model, facilitating the fixing of models of different sizes and shapes, as well as their fixed positioning and infinitely variable positioning at different angles. The pitch motion allows for stepless positioning within a range of ±45° and ±15°; the roll motion allows for movement within a range of ±45° and ±15°, with a 0° fixed-angle lock; and the yaw motion allows for movement within a range of ±90° and ±15°. The force measurement system employs a six-component rod-type strain gauge structure, which includes symmetrically distributed rectangular cross-section beams, X-element support force gauges, hooks, and front and rear connecting flanges, along with wiring holes for the balance and angle measurement encoder. The fixed end of the balance has threaded holes at the bottom for screw connection to the support column, while the floating end has flanges at the top for screw fixation to the base of the rotating mechanism. This system can be used to measure aerodynamic changes generated by the aircraft's actions.

[0019] See Figure 1 A three-degree-of-freedom wind tunnel testing device for a multi-rotor aircraft includes: a wind tunnel test support frame 2, a windshield fairing 3, a column 4, a six-component force balance 5, and a three-degree-of-freedom testing device 6. The wind tunnel test support frame 2 is installed at the center of the wind tunnel flow field. The column 4 is installed directly above the wind tunnel test support frame 2. The windshield fairing 3 is also installed directly above the wind tunnel test support frame 2. The six-component force balance 5 is installed above the column 4. The three-degree-of-freedom testing device 6 is installed above the six-component force balance 5. The multi-rotor aircraft 7 is installed above the three-degree-of-freedom testing device 6.

[0020] Multi-rotor aircraft undergoes overall testing and installation in a wind tunnel. Figure 1As shown, 1 is the wind tunnel inlet, and 2 is the wind tunnel test support platform, which is installed at the center of the wind tunnel flow field. The overall height of the wind tunnel test support platform 2 is 8 meters. A fixed column 4 with a height of 2 meters is installed directly above the wind tunnel test support platform 2. A windshield fairing 3 is also installed directly above the platform 2 to reduce the wind resistance of the column. A six-component force balance 5 is installed above the column 4 to measure the aerodynamic load generated by the model. A three-degree-of-freedom test device 6 is installed above the column 4. The three-degree-of-freedom test device can realize the pitch, yaw and roll motion of the multi-rotor aircraft 7. The overall installation height of the multi-rotor aircraft is 10 meters above the ground and is located at the center of the wind tunnel flow field.

[0021] The three-degree-of-freedom wind tunnel test device 6 includes a roll mechanism 8, a pitch mechanism 9, a yaw mechanism 10, and a fixed base 11. The fixed base 11 is fixedly connected to the upper plate of the six-component force balance 5 by six evenly distributed bolts 12. The upper mounting plate of the roll mechanism device 8 is fixedly connected to the multi-rotor aircraft 7. The yaw mechanism 10, the pitch mechanism 9, and the roll mechanism device 8 are located on the fixed base 11 from top to bottom.

[0022] The front view and axial view of the overall structure of the three-degree-of-freedom wind tunnel testing device 6 are shown below. Figure 2 and Figure 3 Its dimensions are 185*121*175mm (length*width*height), and it weighs less than 10kg. The overall size is exquisite and compact. It can realize the individual rotation of the three axes of roll, pitch and yaw, as well as multi-directional motion coupling. It is composed of a roll mechanism 8, a pitch mechanism 9, a yaw mechanism 10 and a fixed base 11. The fixed base 11 is fixedly connected to the upper plate of the six-component force balance 5 by six evenly distributed bolts 12. The upper mounting plate of the roll mechanism device 8 is fixedly connected to the multi-rotor aircraft 7.

[0023] The rolling mechanism 8 includes: a rotatable component rolling support 13, a rolling connecting shaft 14, an angular contact ball bearing 15, a bearing cover 17, an encoder mounting bracket 19, a rolling encoder 18, and a rolling buffer pad 20. The axial view and exploded view of the rolling mechanism are shown below. Figure 4 and Figure 5As shown, it mainly consists of a rotatable component, a rolling support 13, a rolling connecting shaft 14, and its fixing components. The rolling support 13 and the rolling connecting shaft 14 are fixedly connected by a connecting bolt. The rolling connecting shaft 14 passes through the rolling support 13 and the angular contact ball bearing 15, and is then tightened by a locking nut 16. Finally, the bearing cap 17 presses the outer ring of the bearing, and the connection is finally fixed by six countersunk screws. The outer ring of the angular contact ball bearing 15 is fixedly fitted with the yaw center hole of the pitch support 22 of the pitch mechanism 9, and the inner ring is tightly fitted with the rolling connecting shaft 14. All the above connecting components are coaxially connected and symmetrically installed at the front and rear of the rolling mechanism device 8. At the rear of the rolling mechanism device 8, the rolling connecting shaft 14 is also connected to an encoder fixing bracket 19 and a rolling encoder 18. The rolling encoder 18 can measure and record the rolling angle change of the rolling support 13 in real time. Its motion logic is that when the rolling support 13 rolls, it drives the rolling connecting shaft 14 to move, and the rolling connecting shaft 14 drives the connecting pin of the rolling encoder 18 to move, thus allowing the rolling encoder 18 to collect and record the rolling angle value. Four rolling buffer pads 20 are symmetrically arranged diagonally below the rolling support 13. Each rolling buffer pad 20 has a central hole, and embedded screws are used to fix the rolling buffer pad 20 to the rolling support 13. The rolling buffer pads 20 are used to mitigate the inertial impact caused by the rolling support rolling to its limit position. In this invention, the limit movement angle of the rolling support 13 is 45° to the left and right, and the corresponding limit positions are as follows: Figure 6 As shown, alternatively, the roll support 13 and the pitch support 22 of the pitch mechanism 9 can be fixedly connected by horizontal fixing screws 21, as detailed in the attached diagram. Figure 7 As shown, one horizontal fixing screw 21 is arranged in the forward and backward directions. When the horizontal fixing screw 21 is fixedly connected to the rolling support 13, the rolling support 13 cannot rotate and always remains horizontal. The outer end of the rolling connecting shaft 14 is tightly fitted to the inner ring of the angular contact ball bearing 15. The middle part of the rolling connecting shaft 14 is tightly fitted to the lower center opening of the rolling support 13. The inner end of the rolling connecting shaft 14 is connected to the rolling support 13 in a semi-circular pressing fit by a countersunk screw. The angular contact ball bearing 15, the rolling connecting shaft 14, and the lower center opening of the rolling support 13 are coaxially installed. One rolling connecting shaft 14 is installed in each of the forward and backward directions.

[0024] The pitch mechanism 9 includes: encoder mounting bracket 19, pitch support 22, angular contact ball bearing 23, pitch connecting shaft 24, pitch bearing cover plate 25, pitch encoder connecting bracket 26, pitch encoder 27, and 15-degree limit block 28.

[0025] The axial view and exploded view of the rolling mechanism are as follows: Figure 8 and Figure 9As shown, the pitch mechanism mainly consists of a rotatable pitch support 22, a fixed bracket 19, and other fixed components. The left and right sides of the pitch support 22 are respectively tightly connected to two pitch connecting shafts 24. The pitch connecting shafts 24 pass through the left and right center holes of the pitch support 22, the upper center hole of the yaw support 32, and the angular contact ball bearing 23. The pitch bearing cover plate 25 is fixed to the pitch connecting shafts 24, the pitch support 22, the yaw support 32, and the angular contact ball bearing 23 by two screws. The pitch support 22 has a lateral center hole, the angular contact ball bearing 23, and the rolling connection... Shaft 24 and the center hole at the upper end of yaw support 32 are coaxially connected. Pitch connecting shaft 24 is symmetrically installed on both sides of pitch support 22 along the heading direction. Pitch connecting shaft 24 on the left side is also connected to pitch encoder connecting bracket 26, encoder fixing bracket 19 and pitch encoder 27. When pitch support 22 pitches along the roll axis, encoder fixing bracket 19 will pitch together. Encoder fixing bracket 19 drives encoder connecting bracket 26 to pitch, thereby driving pitch encoder 27 to rotate. Thus, pitch encoder 27 can collect and record pitch angle values. Two 15-degree pitch limiting blocks 28 are symmetrically arranged behind and behind the yaw direction of the pitch mechanism 9. These 15-degree limiting blocks 28 are fixedly installed in the yaw direction within the pitch support 22 by screws. When the pitch support 22 reaches its limit, the 15-degree pitch limiting blocks 28, due to their low position, will preferentially contact the pitch support 22, preventing further travel and thus limiting the pitch travel. Their 15-degree pitch limiting movement is as follows: Figure 10 As shown, if the 15-degree limit block 28 is removed, the 45-degree limit of the pitch mechanism 9 will be as follows: Figure 11 As shown.

[0026] Furthermore, arc-shaped grooves are provided on the left and right sides of the pitch support 22 to artificially restrict the pitch movement of the pitch support 22. Pitch locking plates 29 and three locking nuts 30 are used at the arc-shaped grooves to adjustably fasten or loosen the pitch support 22 and yaw support 32, thereby achieving the desired fixed pitch angle. When the locking plates 29 and locking nuts 30 are removed, the pitch mechanism 9 can move freely in pitch. Additionally, four roll limit blocks 31 are symmetrically arranged on the front, back, left, and right sides of the pitch support 22. When the roll support 13 reaches its limit, the roll buffer pad 20 preferentially contacts the roll limit block 31, preventing its stroke from expanding, thus achieving a limiting and protective function. Furthermore, the roll limit angle of the roll support 13 can be limited by changing the height of the roll limit block 31. See [link to relevant documentation]. Figure 12 .

[0027] The yaw mechanism 10 includes: a yaw support 32, a yaw encoder mounting bracket 33, a yaw encoder connecting shaft 34, a yaw angle limiting block 35, a limiting locking pad 36, a screw 37, a yaw angle encoder 38, an angular contact ball bearing 39, and a yaw connecting cover plate 40.

[0028] The axial view, front view, and exploded view of the yaw mechanism are as follows: Figure 13 , Figure 14 and Figure 15 As shown, the rotatable component is the yaw support 32 (e.g. Figure 17 (As shown), yaw encoder mounting bracket 33, yaw encoder connecting shaft 34, and other components are fixed parts. The inner cavity of the yaw support 32 is tightly fitted with the outer rings of four vertically arranged angular contact ball bearings 39. The inner rings of the angular contact ball bearings 39 are tightly fitted with the fixed base 11. A yaw connecting cover plate 40 is installed at the top of the fixed base 11. The yaw angle encoder 38 is fixed to the yaw connecting cover plate 40 by six ring screws. The bottom end of the yaw encoder connecting shaft 34 is connected to the yaw angle encoder 38, and the top end is connected to the yaw encoder mounting bracket 33. The fixed base 11 (as shown) Figure 16 As shown), the angular contact ball bearing 39, yaw support 32, and yaw angle encoder 38 are connected and installed with the yaw encoder connecting shaft 34 and yaw connecting cover plate 40 in the same vertical rotation axis. When the yaw support 32 yaws along the axis, the yaw encoder mounting bracket 33 will also yaw. The yaw encoder mounting bracket 33 drives the yaw encoder connecting shaft 34 to yaw, thereby driving the yaw angle encoder 38 to yaw and rotate, so that the yaw angle encoder 38 can collect and record the yaw angle value. A yaw angle limiting block 35 and a limiting locking pad 36 are provided in the middle area between the yaw support 32 and the fixed base 11. The yaw angle limiting blocks 35 are set at ±15° position (2 blocks) and 90° position (1 block), so that the yaw limit can be selected to move within the set range of ±90° or ±15° at the beginning of the test. Furthermore, the bottom circumference of the yaw support 32 is provided with several arc-shaped grooves. The yaw support 32, the limiting locking pad 36, and the fixed base 11 are fixedly connected along the arc-shaped grooves by screws 37 in an adjustable position, thereby achieving the function of locking the yaw at a fixed angle. The yaw mechanism's limiting movement is as follows: Figure 18 As shown.

[0029] In summary, the three-degree-of-freedom wind tunnel test device 6 achieves limited movement and 0° fixed-angle locking within ±45° and ±15° ranges in roll motion; stepless positioning and limited movement within ±45° and ±15° ranges in pitch motion; and limited movement and stepless positioning within ±90° and ±15° ranges in yaw motion. The motion axes in the three directions converge at a single point, realizing individual motion of the three degrees of freedom and multi-directional motion coupling.

[0030] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A wind tunnel testing device for a three-degree-of-freedom multi-rotor aircraft, characterized in that, include: The wind tunnel test support platform (2), windshield fairing (3), column (4), six-component force balance (5), and three-degree-of-freedom test device (6) are installed. The wind tunnel test support platform (2) is installed at the center of the wind tunnel flow field. The column (4) is installed directly above the wind tunnel test support platform (2). The windshield fairing (3) is also installed directly above the wind tunnel test support platform (2). The six-component force balance (5) is installed above the column (4). The three-degree-of-freedom test device (6) is installed above the six-component force balance (5). The multi-rotor aircraft (7) is installed above the three-degree-of-freedom test device (6). The three-degree-of-freedom test device (6) realizes the pitch, yaw and roll motion of the multi-rotor aircraft (7).

2. The apparatus according to claim 1, characterized in that, The three-degree-of-freedom wind tunnel test device (6) includes: a roll mechanism (8), a pitch mechanism (9), a yaw mechanism (10) and a fixed base (11). The fixed base (11) is fixedly connected to the upper plate of the six-component force balance (5). The upper mounting plate of the roll mechanism device (8) is fixedly connected to the multi-rotor aircraft (7). The yaw mechanism (10), pitch mechanism (9) and roll mechanism device (8) are located on the fixed base (11) from top to bottom.

3. The apparatus according to claim 2, characterized in that, The rolling mechanism (8) includes: a rotatable component rolling support (13), a rolling connecting shaft (14), an angular contact ball bearing (15), a bearing cover (17), an encoder fixing bracket (19), and a rolling encoder (18). The rolling support (13) and the rolling connecting shaft (14) are fixedly connected. The rolling connecting shaft (14) passes through the rolling support (13) and the angular contact ball bearing (15) respectively. Then, the locking round nut (16) is threaded to tighten it. Finally, the bearing cover (17) is used to press the outer ring of the bearing and finally the connection is fixed by countersunk screws. The outer ring of the angular contact ball bearing (15) is fixedly fitted to the pitch support (22) of the pitch mechanism (9) and the yaw center hole. The inner ring is tightly fitted to the roll connecting shaft (14). All the above connecting parts are coaxially connected and symmetrically installed in front of and behind the yaw of the roll mechanism device (8). The roll connecting shaft (14) behind the roll mechanism device (8) is also connected to the encoder fixing bracket (19) and the roll encoder (18). The roll encoder (18) measures and records the roll angle change of the roll support (13) in real time. When the roll support (13) rolls, it will drive the roll connecting shaft (14) to move. The roll connecting shaft (14) will drive the connecting pin of the roll encoder (18) to move, so that the roll encoder (18) can collect and record the roll angle value. The limit movement angle of the roll support (13) is 45° to the left and right.

4. The apparatus according to claim 3, characterized in that, Four rolling buffer pads (20) are symmetrically arranged at the lower side of the rolling support (13). The rolling buffer pads (20) have a central hole, and the rolling buffer pads (20) are fixed to the rolling support (13) by embedded screws in the hole. The roll support (13) and the pitch support (22) of the pitch mechanism (9) are fixedly connected by horizontal fixed connecting screws (21). One horizontal fixed connecting screw (21) is arranged in front and behind the navigator. When the horizontal fixed connecting screw (21) is fixedly connected to the roll support (13), the roll support (13) cannot rotate and always remains in a horizontal state. The outer end of the rolling connecting shaft (14) is tightly fitted to the inner ring of the angular contact ball bearing (15). The middle part of the rolling connecting shaft (14) is tightly fitted to the lower center opening of the rolling support (13). The inner end of the rolling connecting shaft (14) is connected to the rolling support (13) in a semi-circular press-fit connection by countersunk screws. The angular contact ball bearing (15), the rolling connecting shaft (14) and the lower center opening of the rolling support (13) are coaxially installed. One rolling connecting shaft (14) is installed in each direction along the forward and backward direction.

5. The apparatus according to claim 2, characterized in that, The pitch mechanism (9) includes: an encoder mounting bracket (19), a pitch support (22), an angular contact ball bearing (23), a pitch connecting shaft (24), a pitch bearing cover (25), a pitch encoder connecting bracket (26), and a pitch encoder (27). The left and right sides of the pitch support (22) are tightly connected to two pitch connecting shafts (24). The pitch connecting shafts (24) pass through the left and right center holes of the pitch support (22), the upper center hole of the yaw support (32), and the angular contact ball bearing (23). The pitch bearing cover plate (25) is fixed to the pitch connecting shaft (24), the pitch support (22), the yaw support (32), and the angular contact ball bearing (23) by screws. The pitch support (22) is coaxially connected to the lateral center hole, the angular contact ball bearing (23), the roll connecting shaft (24), and the upper center hole of the yaw support (32). The pitch connecting shaft (24) is symmetrically installed on both sides of the pitch support (22) along the heading direction. The pitch connecting shaft (24) on the left side is also connected to the pitch encoder connecting bracket (26), the encoder fixing bracket (19), and the pitch encoder (27). When the pitch support (22) pitches along the roll axis, the encoder fixing bracket (19) will pitch together. The encoder fixing bracket (19) drives the encoder connecting bracket (26) to pitch, thereby driving the pitch encoder (27) to rotate, so that the pitch encoder (27) can collect and record the pitch angle value.

6. The apparatus according to claim 5, characterized in that, Two 15-degree pitch limit blocks (28) are symmetrically arranged in front and behind the pitch mechanism (9). The 15-degree limit blocks (28) are fixedly installed in the inner cavity of the pitch support (22) in front and behind the pitch. When the pitch support (22) moves to the limit, the 15-degree pitch limit blocks (28) will touch the pitch support (22) first because the position of the 15-degree pitch limit blocks (28) is low, which will prevent the range of motion from expanding and limit the pitch range.

7. The apparatus according to claim 6, characterized in that, The pitch support (22) has arc-shaped grooves on its left and right sides respectively. The pitch support (22) and the yaw support (32) are adjusted and tightened or loosened by the pitch locking plate (29) and the locking nut (30) at the arc-shaped grooves. When the locking plate (29) and the locking nut (30) are removed, the pitch mechanism (9) can move freely in pitch. The pitch support (22) has four roll limit blocks (31) arranged symmetrically in front, behind and to the left and right. When the roll support (13) moves to the limit, the roll buffer pad (20) will first touch the roll limit block (31), so that its stroke cannot be expanded, thereby playing a limiting and protective role.

8. The apparatus according to claim 2, characterized in that, The yaw mechanism (10) includes: a yaw support (32), a yaw encoder mounting bracket (33), a yaw encoder connecting shaft (34), a screw (37), a yaw angle encoder (38), an angular contact ball bearing (39), and a yaw connecting cover plate (40). The yaw support (32), yaw encoder mounting bracket (33), and yaw encoder connecting shaft (34) are rotatable components. The inner cavity of the yaw support (32) is tightly fitted with the outer rings of four vertically arranged angular contact ball bearings (39). The inner rings of the angular contact ball bearings (39) are tightly fitted with the fixed base (11). The uppermost end of the fixed base (11) is equipped with a yaw connecting cover plate (40). The yaw angle encoder (38) is fixed to the yaw connecting cover plate (40) by ring screws. The bottom end of the yaw encoder connecting shaft (34) is connected to the yaw angle encoder (38), and the top end is connected to the yaw encoder. Mounting bracket (33); fixed base (11), angular contact ball bearing (39), yaw support (32), yaw angle encoder (38), yaw encoder connecting shaft (34) and yaw connecting cover plate (40) are connected and installed with the same vertical rotation axis; when the yaw support (32) yaws along the axis, the yaw encoder mounting bracket (33) will yaw together. The yaw encoder mounting bracket (33) drives the yaw encoder connecting shaft (34) to yaw, thereby driving the yaw angle encoder (38) to yaw and rotate, so that the yaw angle encoder (38) collects and records the yaw angle value.

9. The apparatus according to claim 8, characterized in that, The yaw support (32) and the fixed base (11) are provided with a yaw angle limiting block (35) and a limiting locking pad (36). The yaw angle limiting block (35) is set at ±15° position with 2 blocks and at 90° position with 1 block.

10. The apparatus according to claim 9, characterized in that, The bottom circumference of the yaw support (32) is provided with several arc-shaped grooves. The yaw support (32), the limit locking pad (36) and the fixed base (11) are fixedly connected along the arc-shaped grooves by screws (37) in an adjustable position, so as to lock the yaw angle.

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