Patent Publication Number: US-2022226984-A1

Title: Legged robot and leg assembly thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority to the Chinese Patent Application No. 202120117250.9 filed on Jan. 15, 2021, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a field of legged robots, and more particularly, to a leg assembly for a legged robot and a legged robot having the same. 
     BACKGROUND 
     A legged robot, also known as a robot having legs, generally includes a body assembly and a leg assembly. The leg assembly includes a thigh pivotably connected to the body assembly and a shank pivotably connected to the thigh. In the related art, due to a large rotational inertia of the shank relative to the thigh, each member of the leg assembly is subjected to a large force and a large impact. Moreover, the leg assembly is noisy, the reliability of the shank is low, and the accurate control of the leg assembly is difficult. 
     SUMMARY 
     Embodiments of the present disclosure provide a leg assembly for a legged robot. 
     Embodiments of the present disclosure further provide a legged robot. 
     The leg assembly for the legged robot according to the embodiments of the present disclosure includes a first leg, a second leg, a motor, an output flange and a transmission component, the motor is arranged at a first end of the first leg, an output shaft of the motor is connected to the output flange to drive the output flange to rotate, the first leg is pivotably connected to the second leg, the transmission component is connected to the output flange and the second leg and configured to drive the second leg to rotate relative to the first leg, the output flange is provided with a first limiting portion, the first leg is provided with a first stop portion and a second stop portion, the first stop portion and the second stop portion are spaced apart and configured to stop the first limiting portion to limit a rotation angle of the output flange, and the first leg is provided with a second limiting portion configured to stop the second leg to limit rotation of the second leg. 
     The legged robot according to the embodiments of the present disclosure includes a body assembly and a plurality of leg assemblies. Each leg assembly includes a first leg, a second leg, a motor, an output flange and a transmission component, the motor is arranged at a first end of the first leg, an output shaft of the motor is connected to the output flange to drive the output flange to rotate, the first leg is pivotably connected to the second leg, the transmission component is connected to the output flange and the second leg and configured to drive the second leg to rotate relative to the first leg, the output flange is provided with a first limiting portion, the first leg is provided with a first stop portion and a second stop portion, the first stop portion and the second stop portion are spaced apart and configured to stop the first limiting portion to limit a rotation angle of the output flange, and the first leg is provided with a second limiting portion configured to stop the second leg to limit rotation of the second leg. The first leg of the leg assembly is pivotably connected to the body assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a legged robot according to an embodiment of the present disclosure. 
         FIG. 2  is a schematic view of a leg assembly for a legged robot according to an embodiment of the present disclosure. 
         FIG. 3  is a schematic view of a leg assembly for a legged robot according to an embodiment of the present disclosure, in which a second leg is in a retraction limit position. 
         FIG. 4  is a schematic view of a leg assembly for a legged robot according to an embodiment of the present disclosure, in which a second leg is in an extension limit position. 
         FIG. 5  is a schematic view of a first leg and an output flange of a leg assembly for a legged robot according to an embodiment of the present disclosure. 
         FIG. 6  is a schematic view of a second leg of a leg assembly for a legged robot according to an embodiment of the present disclosure. 
         FIG. 7  is a schematic view of an output flange and a connecting rod connected with each other of a leg assembly for a legged robot according to another embodiment of the present disclosure. 
         FIG. 8  is a schematic view of a leg assembly for a legged robot according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in accompanying drawings. The following embodiments described with reference to the accompanying drawings are exemplary and are intended to explain the present disclosure rather than limit the present disclosure. 
     A leg assembly for a legged robot and a legged robot having the leg assembly according to embodiments of the present disclosure are described below with reference to the accompanying drawings. 
     First, the legged robot according to the embodiments of the present disclosure is briefly described. As shown in  FIG. 1 , the legged robot according to the embodiments of the present disclosure includes a body assembly  200  and a plurality of leg assemblies  100 . In the embodiment shown in  FIG. 1 , four leg assemblies  100  are provided, and thus the robot can be called as a quadruped robot or a four-legged robot. It can be understood that the present disclosure is not limited to this. For example, the legged robot can also include two leg assemblies  100 . Accordingly, the robot can be called as a biped robot or a two-legged robot. In the embodiment shown in  FIG. 1 , the four leg assemblies  100  are connected to the body assembly  200  to support the body assembly  200 . Actions such as walking of the robot can be realized when the leg assembly  100  operates. 
     The leg assembly  100  of the legged robot according to the embodiments of the present disclosure is described in detail below. 
     As shown in  FIGS. 1 to 8 , the leg assembly for the legged robot according to the embodiments of the present disclosure includes a first leg  1 , a second leg  2 , a motor  5 , an output flange  4  and a transmission component  3 . It can be understood that the first leg  1  can also be called as a thigh and the second leg  2  can also be called as a shank. The first leg  1  can be pivotably connected to the body assembly  200  of the robot. 
     As shown in  FIGS. 2 to 4 , the motor  5  is arranged at a first end of the first leg  1  (an upper end of the first leg  1  as shown in  FIG. 2 ), an output shaft  51  of the motor  5  is connected to the output flange  4  to drive the output flange  4  to rotate, and the first leg  1  is pivotably connected to the second leg  2 . The transmission component  3  is connected to the output flange  4  and the second leg  2  to drive the second leg  2  to rotate relative to the first leg  1 . 
     As shown in  FIGS. 2 to 4 , the output flange  4  is provided with a first limiting portion  41 . The first leg  1  is provided with a first stop portion  11  and a second stop portion  12 . The first stop portion  11  and the second stop portion  12  are spaced apart along a circumferential direction of the output flange  4 . The first stop portion  11  and the second stop portion  12  can limit a rotation angle of the output flange  4  by stopping the first limiting portion  41 , thus limiting a rotation amplitude of the second leg  2  relative to the first leg  1  as well as an extension limit position and a retraction limit position of the second leg  2 . 
     In other words, the first stop portion  11  and the second stop portion  12  define rotation limit positions of the first limiting portion  41  respectively. When the first limiting portion  41  is stopped by the first stop portion  11  or the second stop portion  12 , further rotation of the output flange  4  is prevented, that is, further rotation of the motor  5  is prevented. 
     For example, as shown in  FIGS. 2 to 4 , when the output flange  4  rotates clockwise from a position shown in  FIG. 2 , after the first limiting portion  41  contacts the second stop portion  12  on the first leg  1 , as shown in  FIG. 4 , the second stop portion  12  prevents the output flange  4  from further rotating clockwise, that is, the output flange  4  reaches a clockwise rotation limit position, so that the second leg  2  rotates to the extension limit position. Conversely, when the output flange  4  rotates counterclockwise from the position shown in  FIG. 2 , after the first limiting portion  41  contacts the first stop portion  11  on the first leg  1 , as shown in  FIG. 3 , the first stop portion  11  prevents the output flange  4  from further rotating counterclockwise, that is, the output flange  4  reaches a counterclockwise rotation limit position, so that the second leg  2  rotates to the retraction limit position. 
     The first leg  1  is provided with a second limiting portion  13 , and the second limiting portion  13  is configured to stop the second leg  2  so as to limit rotation of the second leg  2 . As shown in  FIG. 3 , when the second leg  2  moves to the retraction limit position, the second limiting portion  13  stops the second leg  2 , and at the same time, the first stop portion  11  stops the first limiting portion  41 . 
     In the leg assembly for the legged robot according to the embodiments of the present disclosure, since the first stop portion  11  and the second stop portion  12  are arranged on the first leg  1 , a range of a rotation angle of the output flange  4  can be conveniently limited, so as to facilitate the control of a rotation range of the second leg  2 , i.e., the extension limit position and the retraction limit position, thus accurately controlling the operation of the second leg  2 . Moreover, since the second limiting portion  13  is arranged on the first leg  1 , the second leg moving to the retraction limit position is stopped by the second limiting portion  13  when the first limiting portion  41  is stopped by the first stop portion  11 , thus preventing the second leg  2  from hitting the first leg  1 . Therefore, the rotation of the output flange can be conveniently limited within a predetermined angle range. Moreover, since the second limiting portion limits the second leg moving to the retracted limit position, the limiting reliability of the leg assembly can be improved, the forces and impacts applied to various members of the leg assembly can be reduced, the noise is decreased, and the accurate control of the leg assembly is facilitated. 
     As shown in  FIGS. 2 to 4 , the output flange  4  is a disc and is coaxially connected to the output shaft  51  of the motor  5 . The first limiting portion  41  is arranged on an outer circumferential wall of the output flange  4 , and the first stop portion  11  and the second stop portion  12  are arranged on the upper end of the first leg  1  along the circumferential direction of the output flange  4 . 
     In the embodiment shown in  FIGS. 2 to 4 , the first limiting portion  41 , the first stop portion  11  and the second stop portion  12  are rectangular blocks, so that the first limiting portion  41  can be in surface contact with the first stop portion  11  and the second stop portion  12 . Thus, the force is more uniform and the impact is less. In some embodiments of the present disclosure, surfaces of the first stop portion  11  and the second stop portion  12  and/or the first limiting portion  41  may be coated with buffer layers, such as an elastic rubber layer, thereby further reducing impact forces when the first limiting portion  41  contacts the first stop portion  11  and the second stop portion  12 . In some embodiments of the present disclosure, a conical groove can be formed in the surfaces of the first stop portion  11  and the second stop portion  12  in contact with the first limiting portion  41 , and a conical protrusion can be arranged on the first limiting portion  41 , so that the conical protrusion gradually enters the conical groove when the first limiting portion  41  contacts the first stop portion  11  or the second stop portion  12 , so as to further increase the gentleness of the contact and reduce the impact. In some embodiments of the present disclosure, a surface of the conical groove and/or a surface of the conical protrusion can be coated with an elastic material layer, so as to further reduce the impact. 
     In some embodiments, as shown in  FIGS. 2 to 5 , the second limiting portion  13  is a limit block suitable to be in surface contact with the second leg  2 . In some other embodiments, the second limiting portion  13  may also be a limit column suitable to be in line contact with the second leg  2 , as shown in  FIG. 8 . 
     In the embodiments of the present disclosure, the second limiting portion  13  is the limit block suitable to be in surface contact with the second leg  2 , so as to further reduce the force and impact applied to the leg assembly  100  and improve the service life of the leg assembly  100 . 
     Specifically, as shown in  FIG. 3 , the second limiting portion  13  can limit counterclockwise rotation of the second leg  2 , and then limit a height of the leg assembly  100  when the legged robot is upright. Thus, the applicability of the leg assembly  100  is improved and the design of the robot is facilitated. 
     In some embodiments, as shown in  FIGS. 2 to 5 , the output flange  4  is provided with a third limiting portion  42 , and the third limiting portion  42  is configured to stop the transmission component  3  to limit the rotation of the second leg  2 . In other words, as shown in  FIG. 4 , when the second leg  2  moves to the extension limit position, the first limiting portion  41  contacts the first stop portion  11  and the third limiting portion  42  contacts the transmission component  3 , so as to have a dual limit on the second leg  2  moving to the extension limit position, thus improving the limiting reliability. 
     In some embodiments of the present disclosure, as shown in  FIG. 3  and  FIG. 4 , the third limiting portion  42  is a bump  421  arranged on a surface of the output flange  4 . As shown in  FIG. 4 , when the output flange  4  rotates clockwise and when the second leg  2  rotates clockwise to the extension limit position, the transmission component  3  contacts the third limiting portion  42  to stop the movement of the transmission component  3 , so as to limit the rotation of the output flange  4 , the motor  5  and the second leg  2 . The bump  421  rotates clockwise along with the output flange  4  and stops the transmission component  3 , so as to further limit the movement of the second leg  2 , thus further improving the limiting reliability of the leg assembly  100 . 
     In some embodiments, the transmission component  3  includes a connecting rod  31 . A first end of the connecting rod  31  (an upper end of the connecting rod  31  as shown in  FIG. 4 ) is pivotably connected to the output flange  4  through a first pivot shaft  311 , a second end of the connecting rod  31  (a lower end of the connecting rod  31  as shown in  FIG. 4 ) is pivotably connected to a first end of the second leg  2  (an upper end of the second leg  2  as shown in  FIG. 4 ) through a second pivot shaft  312 , and a second end of the first leg  1  (a lower end of the first leg  1  as shown in  FIG. 4 ) is pivotably connected to the first end of the second leg  2  (the upper end of the second leg  2  as shown in  FIG. 4 ) through a third pivot shaft  22 . 
     After the motor  5  is started, the motor  5  drives the output flange  4  to rotate for (example, to swing) around a central axis of the output shaft  51  through the output shaft  51 . Since the first pivot shaft  311  is eccentrically arranged relative to the central axis of the output shaft  51 , the first pivot shaft  311  revolves around the central axis of the output shaft  51 , and then drives the first end of the connecting rod  31  to revolve around the central axis of the output shaft, thus driving the connecting rod  31  to move. Since the second end of the connecting rod  31  is pivotably connected to the first end of the second leg  2  through the second pivot shaft  312 , and also the first end of the second leg  2  is pivotably connected to the second end of the first leg  1  through the third pivot shaft  22 , the connecting rod  31  drives the second leg  2  to rotate around the third pivot shaft  22  relative to the first leg  1 . 
     More specifically, in  FIG. 2 , the second pivot shaft  312  is located between the third pivot shaft  22  and an end face of the first end (a left end in  FIG. 2 ) of the second leg  2 , that is, the second pivot shaft  312  is closer to the end face of the first end of the second leg  2  than the third pivot shaft  22 . When the output flange  4  rotates clockwise, the connecting rod  31  moves upward and drives the second pivot shaft  312  to move upward, so as to drive the second leg  2  to swing clockwise around the third pivot shaft  22 , that is, the second leg  2  extends relative to the first leg  1 . On the contrary, when the output flange  4  rotates counterclockwise, the connecting rod  31  moves downward and drives the second pivot shaft  312  to move downward, so as to drive the second leg  2  to swing counterclockwise around the third pivot shaft  22 , that is, the second leg  2  retracts relative to the first leg  1 . 
     In some other embodiments of the present disclosure, the third pivot shaft  22  may also be located between the second pivot shaft  312  and the end face of the first end of the second leg  2 , that is, the third pivot shaft  22  is closer to the end face of the first end of the second leg  2  than the second pivot shaft  312 . Thus, when the output flange  4  rotates clockwise, the second leg  2  is driven to retract relative to the first leg  1 , and when the output flange  4  rotates counterclockwise, the second leg  2  is driven to extend relative to the first leg  1 . 
     In some embodiments, as shown in  FIG. 7 , the output flange  4  has a recessed portion  422 , an end of the recessed portion  422  is provided with a U-shaped fitting groove  43 , the first end of the connecting rod  31  is pivotably fitted in the U-shaped fitting groove  43 , and a bottom surface of the recessed portion  422  is configured as the third limiting portion  42 . It can be understood that, as shown in  FIG. 7 , when the connecting rod  31  rotates, a side wall of the connecting rod  31  can abut against the bottom surface of the recessed portion  422 , to limit the rotation of the connecting rod  31 , and then to limit the rotation of the output flange  4 , the motor  5  and the second leg  2 , Thus, the limiting reliability is further improved, the forces and impacts applied to various members are reduced, and the movement of the second leg  2  can be accurately controlled. 
     Further, as shown in  FIG. 2 ,  FIG. 5  and  FIG. 6 , a first connecting line between the first stop portion  11  and a center of the output shaft  51  is L 1 , a second connecting line between the second stop portion  12  and the center of the output shaft  51  is L 2 , and an included angle between the first connecting line L 1  and the second connecting line L 2  is 0, in which 110 degrees≤θ≤160 degrees. In other words, the first connecting line L 1  is a connecting line between a center of the output flange  4  and a contact surface of the first stop portion  11  configured to be in contact with the first limiting portion  41 , and the second connecting line L 2  is a connecting line between the center of the output flange  4  and a contact surface of the second stop portion  12  configured to be in contact with the first limiting portion  41 . Through research, the inventor of the present disclosure found that since a swing angle of the first limiting portion  41  is set between 110 degrees and 160 degrees, the force and impact applied to the leg assembly can be further reduced, and the rotation of the second leg  2  is more stable. 
     Specifically, as shown in  FIG. 2 ,  FIG. 5  and  FIG. 6 , and more specifically, as shown in  FIG. 3  and  FIG. 4 , an included angle a between the first connecting line L 1  and a third connecting line L 3  between a center of the third pivot shaft  22  and the center of the output shaft  51  satisfies a relation: 0≤α≤40 degrees. An included angle b between the second connecting line L 2  and a direction perpendicular to the third connecting line L 3  satisfies a relation: 10 degrees≤b≤50 degrees. 
     As shown in  FIG. 3  and  FIG. 4 , a sum of the included angle a between the first connecting line L 1  and the third connecting line L 3  between the center of the third pivot shaft  22  and the center of the output shaft  51  and the included angle b between the second connecting line L 2  and the direction perpendicular to the third connecting line L 3  plus 90 degrees is the included angle θ between the first connecting line L 1  and the second connecting line L 2 . Through research, the inventor of the present disclosure has found that since the included angle a and the included angle b are limited within the above ranges, the forces and impacts applied to various members can be further reduced, the operation is more stable, and the control of the operation of the second leg  2  can be more accurate. 
     In some embodiments, as shown in  FIG. 2 ,  FIG. 5  and  FIG. 6 , an included angle c between a length direction of the second end of the first leg  1  and the third connecting line L 3  satisfies a relation: 130 degrees≤c≤170 degrees. Further, an included angle d between a fourth connecting line L 4  between a center of the second pivot shaft  312  and the center of the third pivot shaft  22  and a fifth connecting line L 5  between the center of the third pivot shaft  22  and a center of the second end (a lower end of the second leg  2  as shown in  FIG. 6 ) of the second leg  2  satisfies a relation: 140 degrees≤d≤180 degrees. 
     Through research, the inventor of the present disclosure found that, since the included angle c of the first leg  1  and/or the included angle d of the second leg  2  are set as described above, the first leg and the second leg have a wide movement range, thus allowing the full use of their degrees of freedom and avoiding interference. Therefore, the movement stability of the first leg  1 , the second leg  2  and the connecting rod  31  is good. 
     Further, as shown in  FIGS. 2-4 , a distance between a center of the first pivot shaft  311  and the center of the output shaft  51  is less than a distance between the center of the second pivot shaft  312  and the center of the third pivot shaft  22 . Through this design, a swing track of the second leg  2  can be controlled more conveniently, the motion performance of the second leg can be improved, and the motion characteristics of the leg assembly and the robot can be controlled more accurately. 
     In some embodiments, as shown in  FIG. 3  and  FIG. 6 , a distance S 1  between the center of the output shaft  51  and the center of the third pivot shaft  22  is 0.6 to 1 times a distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2 . 
     For example, the distance S 1  between the center of the output shaft  51  and the center of the third pivot shaft  22  is 0.6 times the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2 . Or, the distance S 1  between the center of the output shaft  51  and the center of the third pivot shaft  22  is 1 time the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2 . Through simulations, the inventor of the present disclosure found that when a ratio between the second leg  2  and the first leg  1  is 0.6 or 1, the leg assembly  100  can move more smoothly and stably, and consume less energy. 
     In some embodiments of the present disclosure, the distance S 1  between the center of the output shaft  51  and the center of the third pivot shaft  22  is 0.84 times the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2 . Through simulations, the inventor of the present disclosure found that when the ratio between the second leg  2  and the first leg  1  is 0.84, the leg assembly  100  can move even more smoothly and stably, and the energy consumed by the leg assembly  100  is further reduced. 
     In some embodiments, as shown in  FIG. 3  and  FIG. 6 , the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 6 to 10 times a distance S 3  between the center of the second pivot shaft  312  and the center of the third pivot shaft  22 . 
     For example, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 6 times the distance S 3  between the center of the second pivot shaft  312  and the center of the third pivot shaft  22 . Or, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 10 times the distance S 3  between the center of the second pivot shaft  312  and the center of the third pivot shaft  22 . Through experiments, the inventor of the present disclosure found that when a ratio of S 2  to S 3  is 6 or 10, the force and impact applied to the leg assembly  100  can be further reduced, and the rotation of the second leg  2  is more stable. 
     In some embodiments of the present disclosure, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 8.3 times the distance S 3  between the center of the second pivot shaft  312  and the center of the third pivot shaft  22 . Through experiments, the inventor of the present disclosure found that when the ratio of S 2  to S 3  is 8.3, the force and impact applied to the leg assembly  100  are the smallest, and the rotation of the second leg  2  is even more stable. 
     In some embodiments, as shown in  FIG. 3  and  FIG. 6 , the second end of the second leg  2  has a ground contact portion  23 , and an outer circumferential surface of the ground contact portion  23  is a hemispherical surface. The distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 7 to 11 times a radius R 1  of the outer circumferential surface of the ground contact portion  23 . 
     For example, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 7 times the radius R 1  of the outer circumferential surface of the ground contact portion  23 . Or, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 11 times the radius R 1  of the outer circumferential surface of the ground contact portion  23 . Through experiments, the inventor of the present disclosure found that when a ratio of S 2  to R 1  is 7 or 11, the strength of the second leg  2  is good, and the uniformity of the force applied to the second leg  2  can be improved. 
     In some embodiments of the present disclosure, the distance S 2  between the center of the third pivot shaft  22  and the center of the second end of the second leg  2  is 9 times the radius R 1  of the outer circumferential surface of the ground contact portion  23 . Through experiments, the inventor of the present disclosure found that when the ratio of S 2  to R 1  is 9, the strength of the second leg  2  is better, and the uniformity of the force applied to the second leg  2  can be further improved. 
     In some embodiments, as shown in  FIG. 8 , the transmission component  3  includes a first wheel  32 , a second wheel  33  and a flexible transmission member  34  wound around the first wheel  32  and the second wheel  33 . The first wheel  32  is mounted on the output flange  4 , the second wheel  33  is rotatably mounted on the second end of the first leg  1 , and the first end of the second leg  2  is connected to the second wheel  33 . 
     In some embodiments of the present disclosure, as shown in  FIG. 8 , the first wheel  32  and the second wheel  33  are pulleys and the flexible transmission member  34  is a conveyor belt, or the first wheel  32  and the second wheel  33  are sprockets and the flexible transmission member  34  is a chain. It can be understood that the motor  5  can drive the first wheel  32  to rotate, the first wheel  32  drives the second wheel  33  to rotate through the flexible transmission member  34 , and the second wheel  33  can drive the second leg  2  to rotate. 
     Further, as shown in  FIG. 8 , the second limiting portion  13  includes a second left limiting portion  132  and a second right limiting portion  133  spaced apart along a width direction of the first leg  1  (such as a left-right direction of the first leg  1  in  FIG. 8 ), and the second left limiting portion  132  and the second right limiting portion  133  are configured to limit a rotation angle of the second leg  2 . Specifically, the flexible transmission member  34  is located between the second left limiting portion  132  and the second right limiting portion  133 , and the second left limiting portion  132  and the second right limiting portion  133  are symmetrically arranged along a direction perpendicular (i.e. the left-right direction of the first leg  1 ) to a length direction of the first leg  1 . 
     Specifically, as shown in  FIG. 8 , the first end of the second leg  2  is provided with a U-shaped groove  21 , and a part of the second wheel  33  is located in the U-shaped groove  21 . It can be understood that the second wheel  33  is erected on the upper end of the second leg  2 , and the upper end of the second leg  2  is connected to the second wheel  33  through a bolt or a rivet, so that the second wheel  33  can drive the second leg  2  to rotate. 
     As shown in  FIGS. 2 to 4  and  FIG. 8 , the output flange  4  is connected to the output shaft  51  through a plurality of pin shafts  44 . For example, three pin shafts  44  are provided, and the output flange  4  is fixed with the output shaft  51  through the three pin shafts  44 , thus improving the connection strength between the output flange  4  and the output shaft  51 . 
     As shown in  FIG. 1 , the legged robot according to the embodiments of the present disclosure has four leg assemblies  100 , and the four leg assemblies  100  are connected to the body assembly  200 . It can be understood that the first leg  1  of the leg assembly  100  can be driven by an additional motor to rotate relative to the body assembly  200 , and the motor  5  drives the second leg  2  to rotate relative to the first leg  1 , so as to realize actions such as walking of the robot. In the legged robot according to the embodiments of the present disclosure, the limiting of the leg assembly is reliable, the forces and impacts applied to various members are small, the noise is small, the operation is stable, and the control precision is high. 
     In the description of the present disclosure, it shall be understood that terms such as “central,” “longitudinal,” “transverse,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial” and “circumferential” should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not indicate or imply that the device or element referred to must have a particular orientation, or be constructed and operated in a particular orientation. Thus, these terms shall not be construed as limitation on the present disclosure. 
     In addition, terms such as “first” and “second” are merely used for descriptive purposes and cannot be understood as indicating or implying relative importance or the number of technical features indicated. Thus, the features defined with “first” and “second” may explicitly or implicitly include at least one of the features. In the description of the present disclosure, unless otherwise specifically defined, “a plurality of” means at least two, such as two, three, etc. 
     In the present disclosure, unless otherwise explicitly specified and defined, the terms “mounted,” “interconnected,” “connected,” “fixed” and the like are used broadly, and may be, for example, fixed connections, detachable connections, or integral connections; may also be mechanical or electrical connections or intercommunication; may also be direct connections or indirect connections via intervening structures; may also be inner communications or interactions of two elements, which can be understood by those skilled in the art according to specific situations. 
     In the present disclosure, unless otherwise explicitly specified and defined, a structure in which a first feature is “on” or “below” a second feature may include an embodiment in which the first feature is in direct contact with the second feature, and may also include an embodiment in which the first feature and the second feature are not in direct contact with each other, but are contacted via an additional feature formed therebetween. Furthermore, a first feature “on,” “above,” or “on top of” a second feature may include an embodiment in which the first feature is right or obliquely “on,” “above,” or “on top of” the second feature, or just means that the first feature is at a height higher than that of the second feature; while a first feature “below,” “under,” or “on bottom of” a second feature may include an embodiment in which the first feature is right or obliquely “below,” “under,” or “on bottom of” the second feature, or just means that the first feature is at a height lower than that of the second feature. 
     In the present disclosure, terms such as “an embodiment,” “some embodiments,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of these terms in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. In addition, without contradiction, those skilled in the art may combine and unite different embodiments or examples or features of the different embodiments or examples described in this specification. 
     Although the embodiments of the present disclosure have been shown and described above, it can be understood that the above embodiments are exemplary and shall not be understood as limitation on the present disclosure, and changes, modifications, alternatives and variations can be made in the above embodiments by those skilled in the art within the scope of the present disclosure.