JP4679527B2 - Biped robot - Google Patents

Description

  The present invention relates to a biped robot that can float, and more particularly, to a biped robot that achieves weight reduction and simplified structure.

  The technology related to biped robots is advancing rapidly, and various industries are exploring the possibility of applying them to various needs. Such biped robots are sometimes called humanoid robots, and by improving their walking performance and realizing joint movements that are closer to humans, they reduce intimidation and sophisticate their work content, and broaden their work range. It has come to be. In Japan, where we are facing an aging society, application to nursing care for the elderly and the disabled is being considered, and facility guidance is provided at expos and amusement facilities, and production lines that manufacture automobiles, home appliances, etc. Plays its role as an assembly robot.

  Looking at the construction industry, the application of biped robots is desired for disaster recovery activities and disaster recovery surveys in the event of frequent earthquakes and typhoons. Also, in high-risk tasks such as construction of various public facilities and office buildings, and demolition / removal work, if a biped robot can work on behalf of humans, it will lead to a reduction in accidents and disasters. The social credibility of Furthermore, considering the decrease in the labor force population, expectations for biped robots, especially in the construction industry, are even higher.

  Regarding the development of biped walking robots, as described in Patent Documents 1 to 4, the leg performance, that is, not only walking, but also energizing the realization of running and jumping, surfaced No development has been made on floating or biped robots. However, by developing a biped robot that has not only running performance but also levitation performance, it is possible to move the biped robot in a short time to a working place at a high place or a deep position in an excavation mine. Can eliminate the need for permanent installation of lifting equipment.

  Therefore, the present inventors have come up with the idea of a biped robot that can float freely, and the technique is disclosed in Patent Document 5. In principle, this biped robot uses three ducted fans and adjusts the center of gravity of the robot and the resultant force center of the thrust of the ducted fan to realize a stable floating motion.

JP 2005-64837 A JP 2004-299035 A JP 2003-266337 A JP 2003-231081 A JP 2006-297554 A

  According to the biped walking robot disclosed in Patent Document 5, stable floating of the robot can be realized. On the other hand, since a plurality of ducted fans are mounted, the weight of the entire robot increases, and the ducted fan drive is performed. Therefore, it is necessary to apply a relatively large-scale motor and internal combustion engine with high output. In this biped robot, although load reducing means is provided at the knee joint, ankle joint, etc. in order to solve the problem of chain weight increase, it is desired to develop a biped robot that is lighter and can float. By the way. The biped walking robot of the present invention has been made in view of such a problem, and an object thereof is to provide a biped walking robot that can be levitated and can realize further weight reduction and structure simplification. It is said.

  In order to achieve the above object, the biped robot according to the present invention is a biped robot in which left and right legs are attached to each of two hip joints, and the hip joint is connected to a connecting member. A first drive device is provided for rotating the left and right leg portions in the front-rear direction to move the robot forward and backward, and both the left and right leg portions have a substantially flat louver extending in the longitudinal direction of the leg portion. Is mounted on the side of the one leg that faces the other leg, and the fan moves its rotation shaft from one leg to the other via the second drive device. Mounted at a connecting member position that is rotatable to the leg side and blows out from the fan directly onto the louver, and at least the levitation direction is adjusted by the inclination of the louver according to the operation of the hip joint The And it is characterized in Rukoto.

  The connecting member forms the body of the robot for connecting the left and right legs indirectly and integrally, and its shape is not particularly limited, but from the viewpoint of weight reduction and rigidity (strength), For example, box-shaped or gate-shaped members made of steel members can be selected.

  Left and right hip joints equipped with actuators such as motors are attached to the connecting member, and legs are attached to the actuators of both hip joints. The left and right leg portions are rotated in the front-rear direction so as to advance or retract the robot at least, and an actuator for that purpose only needs to be attached to the hip joint.

  The leg part has a thigh member and a lower leg member connected via a knee joint, and the lower leg member and a foot member are connected via an ankle joint. Here, the knee joint and the ankle joint may be provided with actuators for joint driving, and when the driving at each joint is not required, the joint may be fixed in a fixed posture. . Therefore, when it is not necessary to drive the knee joint and the ankle joint, the left and right legs are only rotated in the front-rear direction by the pair of left and right actuators at the hip joint. For example, when the knee joint and the ankle joint are not provided with joint actuators, the movement control is executed by the direction control based on the thrust of the fan and the inclination of the louver, which will be described later, even during slight back-and-forth movement and lateral movement. .

  Further, the left and right leg portions, for example, the thigh members thereof, have a substantially flat louver in a posture in which the longitudinal direction is directed to the longitudinal direction of the leg portion, and the side surface of the one leg portion that faces the other leg portion. It is attached to. Here, the term “substantially flat” means that the cross section is a flat shape, a flat elliptical shape, the end of the flat elliptical shape is not a curved shape, an acute shape, a streamline shape, etc. It is meant to encompass general shapes that can perform direction control functions.

  In addition, a fan that is rotated by various motors, an internal combustion engine, or the like is mounted at a position directly above the left and right leg portions of the connecting member, and the airflow generated by the fan (the wake from the fan) is directed downward. By blowing out (blowout flow), the reaction force acts on the fan to lift the robot. In addition, this blowing flow is directly applied to the left and right leg louvers, and by appropriately adjusting the inclination angle of the louvers, the propulsion force is generated forward and backward to fly the robot forward and backward. In other words, it is possible to fly left and right laterally by generating right and left lateral propulsive force, and to rotate and fly by generating a turning couple around the center of gravity of the robot. The aerial stop operation (hovering) in the floating state is performed by adjusting the balance between the overall weight of the robot and the fan reaction force.

  Here, the connection form between the connecting member and the fan is such that one end of the link mechanism or one end of the rack and pinion mechanism is attached to a place where the rotation of the rotating blades of the fan is not hindered, and these mechanisms are connected by an actuator such as a motor. By operating the fan, the fan is connected in such a manner that its rotating shaft rotates from one leg side to the other leg side.

  By rotating the left and right leg portions in the front-rear direction by a predetermined angle via the hip joint, the inclination angle of the louver is adjusted, and the flight control in the front-rear direction of the robot can be executed by the thrust of the fan. . Further, the flight control in the left-right direction of the robot can be executed by rotating the fan by a predetermined angle. Furthermore, the robot can be rotated in a floating posture by the rotation of the fan and the back and forth movement of the two hip joints (movement in which the inclination angles of the two louvers change each other).

  According to the above biped robot according to the present invention, only one fan that generates thrust is mounted, and the left and right legs are rotated to control the direction of the blowout flow from the fans with the louvers attached to them. With such an extremely simple configuration, the floating control of the robot and the flight control in an appropriate direction can be realized. Furthermore, because of this structure, the robot itself can be reduced in weight and size, and its manufacturing cost can be reduced.

  The connecting member is equipped with a GPS (Global Positioning System) such as a car navigation system, a gyro sensor and an actuator rotation control mechanism based on real-time sensing, a CCD camera, etc. It is possible to identify the position, ensure levitation stability, and take pictures in the high places, deep places, and dangerous areas (photographs such as the state of damage, the state of underground mine walls, and the state of cracks in the upper walls of high-rise buildings).

  As another embodiment of the biped robot according to the present invention, the fan rotates in a direction orthogonal to the rotation direction and also in the forward / backward direction of the robot via a third driving device. It may be movable.

  By setting the rotation direction of the fan to the two orthogonal directions, it is possible to realize the direction control at the time of floating the robot with higher accuracy.

  In another embodiment of the biped robot according to the present invention, a biped robot in which left and right legs are attached to two hip joints, respectively, the hip joint has left and right legs to advance and retract the robot. A first drive device that rotates the leg portion in the front-rear direction; and a second drive device that rotates the left and right leg portions in the left-right direction. A substantially flat first louver is mounted on a side of one leg that faces the other leg in a posture in which the longitudinal direction thereof is directed to the longitudinal direction of the leg. Among them, a substantially flat second louver extending in a direction orthogonal to the first louver is attached to the end facing the other leg, and the two hip joints are fixed to the fan, The fan is directly above the left and right legs, Is disposed at a position where the blowout flow can be directly applied to the louver, and the first and second louvers are inclined and the levitation direction is adjusted according to the operation of the hip joint. .

  In the embodiment of the present invention, the louver extending in two orthogonal directions is attached to the left and right legs, so that the rotation of the fan is unnecessary (the fan is fixed to the hip joint) and the direction control during the robot floating is realized. To do. In this embodiment, the box-shaped and gate-shaped connecting members described above are not applied, and the left and right hip joints are fixed at locations where there is no hindrance to the rotation of the fan.

  By appropriately controlling the rotation of the left and right leg portions, it becomes possible to change the levitation direction by directing the wake from the fan directly onto the louvers spreading in two directions.

  According to this embodiment, since an actuator for driving a fan can be dispensed with, the robot can be further reduced in weight, the structure can be further simplified, and the manufacturing cost can be reduced.

  Further, by using a ducted fan in which a fan is installed in the duct as the above-mentioned fan, there is a possibility that the fan and the connecting member interfere when the fan is inclined, or an airborne obstacle collides with the fan when the robot is lifted. The danger can be avoided and the levitation safety of the robot can be improved.

  As can be understood from the above description, according to the biped walking robot of the present invention, it becomes possible to appropriately control the floating direction of the robot with an extremely simple structure in which appropriate louvers are attached to the left and right legs, The weight reduction, size reduction, and cost reduction can be realized.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an embodiment of a biped robot according to the present invention, and FIG. 2 is a view taken in the direction of arrows II-II in FIG. FIG. 3 is a diagram showing a state of levitation movement in the left-right direction of the biped walking robot of FIG. 1, and FIG. 4 is a diagram showing a situation of levitation movement in the front-rear direction of the biped walking robot of FIG. FIG. 5 is a diagram illustrating thrust deflection by the louver, and FIG. 6 is a diagram illustrating a floating rotation state of the biped robot of FIG. FIG. 7 is a front view of another embodiment of the biped robot of the present invention, and FIG. 8 is a view taken in the direction of arrows VIII-VIII in FIG. FIG. 9 is a diagram showing the levitation movement situation in the left-right direction of the biped walking robot of FIG. 7, and FIG. 10 is a diagram showing the levitation movement situation of the biped walking robot in FIG. FIG. 11 is a diagram showing a floating rotation state of the biped robot of FIG. FIG. 12 is a front view of still another embodiment of the biped robot of the present invention, and FIG. 13 is a view taken in the direction of arrows XIII-XIII in FIG. FIG. 14 is a perspective view of another embodiment of the louver. FIG. 15 is a diagram showing the levitation movement situation of the biped walking robot of FIG. 12 in the left-right direction, and FIG. 16 is a diagram showing the levitation movement situation of the biped walking robot of FIG. FIG. 17 is a diagram showing a floating rotation state of the biped robot of FIG. Unless otherwise specified, each member constituting the biped walking robot is formed from a steel material, an aluminum alloy, FRP, etc., and the plate members are welded, bonded or bolted to an appropriate shape, It is formed by using a mold steel material.

  1 and 2 are a front view and a side view (arrow view) of an embodiment of a biped robot according to the present invention. This biped walking robot 10 is made of steel and has a gate shape in a front view, and includes both a connecting member 1 composed of left and right vertical members 11 and 12 and a horizontal member 13 connecting them, and the vertical members 11 and 12. Leg portions (from above, thigh members 3a and 3b, knee joints 6a1 and 6b1, lower leg members 4a and 4b, ankle joints 6a2 and 6b2, and foot members) 5a, 5b) and a ducted fan 7 that is pivotably suspended below the horizontal member 13 of the connecting member 1.

  The ducted fan 7 includes a plurality of fans 71 rotating around the rotation shaft 73 and a duct 72 that accommodates the fans 71... The duct 72 and the lower surface of the horizontal member 13 of the connecting member 1 connect the ball joint 95. Connected through. Two servomotors 91 and 92 are mounted on the horizontal member 13 in a posture in which the rotation shaft faces the right leg portion (left leg portion in FIG. 1) and the front side. The right side surface (left side surface in FIG. 1) and the servo motor 92 are connected to the front surface of the duct 72 via cam link mechanisms 94 and 93, respectively.

  The leg part will be described by taking the right leg part (the left leg part in FIG. 1). The hip joint 2a includes a servo motor 2a1 that rotates the thigh member 3a to the foot member 5a in the front-rear direction. On the inner side, that is, on the side surface facing the thigh member 3b, a substantially flat louver 8 having a vertically long rectangle and a streamline shape as shown in FIG. FIG. 2 shows the louver 8 on the left leg side.

  In the illustrated embodiment, the knee joint 6a1 is provided with the joint servomotor 6a11, and the ankle joint is provided with the joint servomotor 6a21. However, the joint servomotor may not be provided. In addition to the servo motor 2a1, a separate servo motor that rotates the leg portion to the left and right may be disposed at the hip joint 2a.

  When the robot 10 is walking, it goes without saying that the rotation control of the servo motors 2a1, 2b1, 6a11, 6b11, 6a21, 6b21 is executed by a known control mechanism (not shown). Further, although illustration of the rotational power means of the fans 71,... Is omitted, an appropriate power means such as a servo motor, a hydraulic motor, or an internal combustion engine can be selected. Of course, in the case of applying any power means, it is of course necessary to have at least an output capable of levitating a biped walking robot equipped with the power means by thrust generated by the rotation of the fan.

  As shown in the figure, the ducted fan 7 suspended from the horizontal member 13 via the ball joint 95 is disposed immediately above the left and right leg portions, more specifically, directly above the left and right louvers 8, 8. 7 is configured such that the blowout flow from 7 is directly applied to the louvers 8 and 8.

A floating movement mode of the biped robot 10 will be described with reference to FIGS.
FIG. 3 shows a situation where the biped walking robot 10 is levitating and moving in the left-right direction. This movement is performed while sensing the moving direction and the stability of the robot at any time by a gyro sensor (not shown). By rotating the servo motor 91 by a predetermined rotation angle, the ducted fan 7 is moved in the X1 direction shown in the figure. By rotating a predetermined angle and directing the blowout flow Y1 from the ducted fan 7 onto either the left or right thigh member side surface and the louver 8, it is possible to generate left and right lateral propulsive force and to perform left and right lateral flight (for example, Z1 direction in FIG. 3).

  On the other hand, FIG. 4 shows a situation where the biped robot 10 is levitating and moving in the front-rear direction. This levitation movement causes the ducted fan 7 to rotate by a predetermined angle in the X2 direction shown in the figure by rotating the servo motor 92 by a predetermined rotation angle, and the blowing flow Y2 from the ducted fan 7 is applied to one side of the left and right louvers 8,8. It is executed by direct exposure.

Here, the thrust deflection by the louver in this levitation movement mode will be described with reference to FIG.
When the louver 8 is rotated by a predetermined rotation angle θ with respect to the rotation shaft 73 of the fan according to the rotation of the left and right legs, a levitation thrust force Fv acts on the fan as a reaction of the blowout flow Y2 from the fan. Further, a lateral thrust Fh is generated. Here, as the rotation angle θ increases, the force to push the louver 8 downward by the blowing flow Y2 also increases, and the descent and rise of the robot 10 is controlled by the balance between this and the thrust Fv and the weight of the robot 10. The Further, the magnitude of the lateral thrust Fh also changes with the fluctuation of the rotation angle θ, leading to a change in the moving speed in the lateral direction. Note that the relationship between Fv, Fh, and robot weight changes not only the elevation of the robot but also the movement in the diagonally up and down direction and the movement speed thereof.

  Therefore, the GPS device (not shown) mounted on the biped walking robot 10 specifies the position in a remote management wing at any time, and senses the moving direction and the posture stability in real time by the gyro sensor and The thrust (Fv, Fh) is adjusted and controlled to move in the direction.

  FIG. 6 illustrates a situation where, for example, the biped robot 10 is rotated in a posture where the robot 10 is suspended. This rotation is achieved by rotating the louvers 8 and 8 in the front-rear direction (W1 direction shown in the figure) by synchronously rotating the servo motors 2a1 and 2b1 at the left and right hip joints in the reverse direction, thereby causing the robot to move by the blowout flow Y3 from the fan. This can be realized by generating a turning couple with the center of gravity as the rotation axis.

  7 and 8 show a front view and a side view (arrow view) of another embodiment of the biped robot, and the levitation movement modes of left-right movement, front-back movement, and rotation are shown in FIGS. 11. In the present embodiment, the ducted fan 7 does not need to be rotated in two directions, so that the duct 72 and the horizontal member 13 of the connecting member 1 are connected via a single rotating shaft member 96. Well, there is no need for a ball joint connection.

  This biped robot 10 </ b> A is an embodiment in which only one servomotor 91 is provided as a servomotor mounted on the connection member 1.

  In the present embodiment, only one servo motor is provided, so that the ducted fan 7 is rotated only in one direction, but even in that case, the levitating movement in the left-right direction shown in FIG. 9 and the rotation shown in FIG. The movement similar to that of the biped robot 10 can be realized without any trouble in movement.

  On the other hand, when the biped walking robot 10A is lifted and moved in the front-rear direction, the ducted fan 7 does not rotate as shown in FIG. By controlling the rotation at the rotation angle (W2 direction), the lateral thrust by the blowout flow Y2 ′ from the fan works, and in the illustrated rotation mode, the robot 10A is levitated and moved forward (Z2 ′ direction). Can do.

  12 and 13 are a front view and a side view (arrow view) of still another embodiment of the biped robot.

  In this biped robot 10B, the left and right hip joints 2a 'and 2b' are fixed to the side surface of the duct 72 of the ducted fan 7, and two servo motors 2a1 and 2b2 (2b1 and 2b2) are respectively provided to the hip joints 2a 'and 2b'. Specifically, servo motors 2a1 and 2b1 for rotating the left and right leg portions in the front-rear direction and servo motors 2a2 and 2b2 for rotating the left and right leg portions in the left-right direction are provided above the servo motors 2a1 and 2b1.

  Further, as shown in FIG. 14, the left and right thigh members 3a and 3b include a flat member 81 (first louver) in the vertical direction corresponding to the louver 8 similar to the biped walking robot 10 and 10A and the end side thereof. A louver 8A configured by a flat member 82 (second louver) that is fixed to the flat member 81 and orthogonal to the flat member 81 is mounted. The left and right louvers 8A, 8A are arranged at intervals that do not interfere with the movement of the center of gravity during walking of the robot. A louver 8A composed of orthogonal flat member 81 and flat member 82 is attached to the leg portion, and the left and right leg portions are rotated in the front-rear direction and the left-right direction, whereby thrust deflection in two orthogonal directions (one-direction thrust deflection) Is described in FIG. 5, and the levitation is substantially the same as adjusting the levitation direction by generating a thrust deflection in one direction in the louver 8 by rotating the ducted fan in two orthogonal directions. Direction adjustment is possible.

  In the present embodiment, instead of making the ducted fan 7 unrotatable, the left and right leg portions can be pivoted back and forth, and left and right, and a louver extending in two orthogonal directions is attached to the leg portions. It implement | achieves each levitating movement of the left-right direction as shown in -17, the front-back direction, and rotation. Here, since the flat members 81 and 82 constituting the louver 8A are arranged at equal distances from the ducted fan 7, the lateral thrust generated by both flat members 81 and 82 can be adjusted to the same extent. it can.

  Specifically, in FIG. 15, the left and right legs are rotated in the left-right direction (W3 direction) to cause a lateral thrust by the blow-off flow Y1 ′ from the fan. In the illustrated rotation mode, the robot 10B is moved to the left. It can be levitated in the direction (Z1 direction in the right direction in the figure). Further, in FIG. 16, similarly to FIG. 10, the robot 10 </ b> B can be levitated and moved in the forward direction (Z2 ′ direction). Further, in FIG. 17, the left and right leg portions are alternately rotated in the front-rear direction (W1 direction), thereby enabling rotation in the floating state.

The inventors have verified whether or not the small biped walking robot described below can be levitated.
The prototype biped robot uses a commercially available ducted fan capable of exerting a thrust of 20N with an input of about φ100mm, weight of 1N and 1000W, can input 1000W, has a weight of about 2N, and has a weight of 2.5N. A battery made of lithium polymer is used as a fan power means. Servo motors for rotating various joints and servo motors for rotating ducted fans. About 10 servo motors with a weight of 0.2N / 1 are used. A controller (proportional) for proportional control with a weight of 0.3 N, a controller with a weight of 0.3 N and a lithium polymer battery for a servo motor, a control microcomputer with a weight of 1 N, and various actuator connecting members with a total weight of 5 N A biped walking robot with a total weight of 14N and a total height of several tens of centimeters Tsu is a door.

  The ratio of the thrust of the biped robot to the total weight is 1.42, which satisfies the ratio 1.3 required for levitation.

  As a result of movement control of the biped robot, for example, the movement and rotation shown in FIGS. 3, 4, and 6 can be reliably executed in the floating posture.

  By mounting a CCD camera on the above-mentioned small biped robot, for example, it is possible to take pictures of the earthquake-stricken area, the state of the pit wall deep in the underground mine wall, the crack state of the upper wall of a high-rise building, etc. for a short time. It becomes possible to shoot with. In addition, it is possible to perform various types of work at high places by attaching a shoulder joint and an arm joint to the connection member and increasing the thrust.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

It is a front view of one embodiment of a biped walking robot of the present invention. It is an II-II arrow line view of FIG. It is the figure which showed the levitation movement situation to the left-right direction of the biped walking robot of FIG. It is the figure which showed the levitation movement situation to the front-back direction of the biped walking robot of FIG. It is a figure explaining thrust deflection by a louver. It is the figure which showed the floating rotation state of the biped walking robot of FIG. It is a front view of other embodiment of the biped walking robot of this invention. It is a VIII-VIII arrow line view of FIG. It is the figure which showed the levitation movement situation to the left-right direction of the biped walking robot of FIG. It is the figure which showed the levitation movement situation to the front-back direction of the biped walking robot of FIG. It is the figure which showed the levitation rotation situation of the biped walking robot of FIG. It is a front view of further another embodiment of the biped walking robot of the present invention. It is a XIII-XIII arrow line view of FIG. It is a perspective view of other embodiment of a louver. It is the figure which showed the levitation movement situation to the left-right direction of the biped walking robot of FIG. It is the figure which showed the levitation movement situation to the front-back direction of the biped walking robot of FIG. It is the figure which showed the floating rotation situation of the biped walking robot of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Connection member 11,12 ... Vertical member, 13 ... Horizontal member, 2a, 2a ', 2b, 2b' ... Hip joint, 2a1, 2b1 ... Servo motor (drive device), 3a, 3b ... Thigh member, 4a, 4b ... lower leg member, 5a, 5b ... foot member, 7 ... ducted fan, 71 ... fan, 72 ... duct, 8, 8A ... louver, 81 ... flat material (first louver), 82 ... flat material (second louver) 91, 92 ... Servo motor (drive device), 93, 94 ... Cam link mechanism, 95 ... Ball joint

Claims (4)

In a biped walking robot in which left and right legs are attached to each of two hip joints, and the hip joints are connected to a connecting member,
The hip joint includes a first drive device that rotates left and right legs in the front-rear direction to advance and retract the robot.
Both of the left and right leg portions are mounted with a substantially flat louver in a posture in which the longitudinal direction thereof is directed to the longitudinal direction of the leg portion, and on the side surface of the one leg portion facing the other leg portion. ,
At the connecting member position where the fan is rotatable about the rotation shaft from one leg side to the other leg side via the second driving device, and the blowout flow from the fan is directly radiated to the louver. Is installed,
A biped walking robot characterized in that a levitation direction is adjusted by an inclination of the louver according to at least the movement of the hip joint.   2. The two feet according to claim 1, wherein the fan is rotatable in a direction perpendicular to the rotation direction and in a forward / backward direction of the robot via a third driving device. Walking robot. In a biped robot in which left and right legs are attached to each of two hip joints,
The hip joint includes a first driving device that rotates left and right legs in the front-rear direction to move the robot forward and backward, and a second driving device that rotates the left and right legs in the left-right direction. And
On both the left and right legs, a substantially flat first louver is mounted on the side of one leg that faces the other leg in a posture with its longitudinal direction oriented in the longitudinal direction of the leg. Has been
A substantially flat second louver that extends in a direction orthogonal to the first louver is attached to the end of the first louver facing the other leg,
The two hip joints are fixed to the fan, and the fan is disposed directly above the left and right legs so that the blowing flow can be directly applied to the louver.
The biped walking robot characterized in that the first and second louvers are tilted and the levitation direction is adjusted according to the movement of the hip joint.   The biped robot according to claim 1, wherein the fan is a ducted fan.

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