Patent Description:
Legged robots, also known as robots having legs, generally include a body assembly and a leg assembly. The leg assembly includes a thigh pivotably coupled to the body assembly and a shank pivotably coupled to the thigh. In the related art, a joint of the leg assembly of legged robots has narrow movement range and low degree of freedom, resulting in that the legged robot cannot complete more complex actions. Therefore, the legged robots cannot meet use needs of users and have poor adaptability.

<CIT> discloses a three-degree-of-freedom robot leg structure which includes a first joint assembly, a second joint assembly and a third joint motor module, the first joint assembly structurally includes a first joint motor support, a first joint motor module is fixed to the outer portion of the first joint motor support, and a crank is installed at the output end of the first j oint motor module; an output rod is hinged to the head of the crank, a shank is hinged to the head of the output rod, and a foot end assembly is installed at the bottom of the shank; the second joint assembly structurally includes a second joint motor support, a second joint motor module is mounted in the second joint motor support, a second joint mounting disc is mounted at the output end of the second joint motor module, and the second joint mounting disc is fixed to the first joint motor support through a fastener; a thigh is further installed at one end of the first joint motor support and hinged to the shank. An output end of the third joint motor module is connected with the second joint motor support, and the work is reliable.

The present invention aims to solve at least one of the technical problems in the related art to a certain extent.

To this end, embodiments of the present invention provide a leg assembly for a legged robot with a wide movement range and good adaptability.

The embodiments of the present invention further provide a legged robot having the leg assembly of the above embodiments.

The leg assembly for the legged robot according to the embodiments of the present invention includes: a first motor, a second motor and a third motor, the first motor being coupled to the second motor to drive the second motor to rotate relative to the first motor, a rotation axis of the first motor being substantially orthogonal to a rotation axis of the second motor, the second motor being coupled to the third motor to drive the third motor to rotate relative to the second motor, a rotation axis of the third motor substantially coinciding with the rotation axis of the second motor; and a first leg part, a second leg part and a transmission component, the third motor being arranged at a first end of the first leg part, the second leg part is pivotably coupled to a second end of the first leg part, the transmission component being coupled to an output shaft of the third motor and the second leg part to drive the second leg part to rotate relative to the first leg part.

The leg assembly for the legged robot according to the embodiments of the present invention can allow the first leg part and the second leg part to move in a large range in the three-dimensional space through relative rotations between the first motor, the second motor and the third motor, so that the legged robot can complete more complex actions, and then improve the applicability of the leg assembly of the legged robot.

In some embodiments, the leg assembly further includes a first flange coupled to the second motor and located between the first motor and the second motor, the first flange is provided with a first limit portion, the first motor is provided with a first stop portion and a second stop portion, the first stop portion and the second stop portion are spaced apart to limit a rotation angle of the second motor by stopping the first limit portion.

In some embodiments, an angle α between a first coupling line of the first stop portion and a rotation center of the first motor and a second coupling line of the second stop portion and the rotation center of the first motor satisfies: <NUM> degrees ≤α≤ <NUM> degrees.

In some embodiments, the first flange is provided with a second limit portion, the leg assembly further includes a second flange coupled to the third motor and located between the second motor and the third motor, the second flange is provided with a third stop portion and a fourth stop portion, and the third stop portion and the fourth stop portion are spaced apart to limit a rotation angle of the third motor by stopping the second limit portion.

In some embodiments, an angle β between a third coupling line of the third stop portion and a rotation center of the second motor and a fourth coupling line of the fourth stop portion and the rotation center of the second motor satisfies: <NUM> degrees ≤β≤ <NUM> degrees.

In some embodiments, the second limit portion is substantially located on a coupling line between the first limit portion and the rotation center of the first flange.

In some embodiments, the first flange includes a first coupling portion and a second coupling portion, the first coupling portion is coupled to an output shaft of the first motor and the second coupling portion, the second coupling portion is coupled to the casing of the second motor, the first limit portion is located on the first coupling portion, and the second limit portion is located on the second coupling portion.

In some embodiments, the first coupling portion is a disc-shaped member, the first coupling portion is coupled to an end of the output shaft of the first motor, the second coupling portion is a ring-shaped member, and the second coupling portion surrounds the casing of the second motor.

In some embodiments, the leg assembly further includes a third flange, the third flange is coupled to an output shaft of the third motor to drive the third flange to rotate, the third flange is provided with a third limit portion, the first leg part is provided with a fifth stop portion and a sixth stop portion, and the fifth stop portion and the sixth stop portion are spaced apart to limit a rotation angle of the third motor by stopping the third limit portion.

In some embodiments, an angle γ between a fifth coupling line of the fifth stop portion and a rotation center of the third motor and a sixth coupling line of the sixth stop portion and the rotation center of the third motor satisfies: <NUM> degrees ≤γ≤ <NUM> degrees.

In some embodiments, the transmission component includes a coupling rod having a first end pivotably coupled to the third flange through a first pivot shaft and a second end pivotably coupled to a first end of the second leg part through a second pivot shaft, and the second end of the first leg part is pivotably coupled to the first end of the second leg part through a third pivot shaft.

In some embodiments, the third flange is provided with a recessed portion, an end of the recessed portion is provided with a U-shaped fitting groove, the first end of the coupling rod is pivotably fitted in the U-shaped fitting groove, and a surface of the recessed portion can stop the coupling rod to limit rotation of the second leg part.

In some embodiments, the first leg part includes an inner housing and an outer housing, the third motor is coupled to the inner housing, the inner housing and the outer housing are coupled with each other and define a receiving cavity, and the transmission component is arranged inside the receiving cavity.

In some embodiments, the inner housing and the outer housing are detachably coupled through a threaded member, a circumferential wall of the receiving cavity is provided with crossed reinforcing ribs, and the threaded member is located at a junction of the reinforcing ribs.

In some embodiments, an outer circumferential wall of the outer housing is coated with a buffer layer.

The legged robot according to the embodiments of the present invention includes a body assembly and a plurality of leg assemblies according to any one of the above embodiments, and the first motor of the leg assembly is coupled to the body assembly.

The legged robot according to the embodiments of the present disclosure has a wide movement range and good applicability.

Embodiments of the present invention are described in detail below, and examples of the embodiments are illustrated in accompanying drawings. The following embodiments described with reference to the accompanying drawings are exemplary and are intended to explain the present invention rather than limit the present invention.

A leg assembly for a legged robot and a legged robot having the leg assembly according to an embodiment of the present invention are described below with reference to the accompanying drawings.

First, the legged robot according to the embodiments of the present invention is briefly described. As illustrated in <FIG>, the legged robot according to the embodiments of the present invention includes a body assembly <NUM> and a plurality of leg assemblies <NUM>. In the embodiment illustrated in <FIG>, four leg assemblies <NUM> 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 invention is not limited to this. For example, the legged robot can also include two leg assemblies <NUM>, and accordingly, the robot can be called as a biped robot or a two-legged robot. In the embodiment illustrated in <FIG>, the four leg assemblies <NUM> are coupled to the body assembly <NUM> to support the body assembly <NUM>. Actions such as walking of the robot can be realized when the leg assemblies <NUM> operate.

The leg assembly for the legged robot according to the embodiments of the present invention is described in detail below with reference to <FIG>.

As illustrated in <FIG>, <FIG> and <FIG>, the leg assembly <NUM> for the legged robot according to the embodiments of the present invention includes: a first motor <NUM>, a second motor <NUM>, a third motor <NUM>, a first leg part <NUM>, a second leg part <NUM> and a transmission component <NUM>.

The first motor <NUM> is mounted on the body assembly <NUM> of the legged robot. The first motor <NUM> is coupled to the second motor <NUM> to drive the second motor <NUM> to rotate relative to the first motor <NUM>, and a rotation axis of the first motor <NUM> is substantially orthogonal to a rotation axis of the second motor <NUM>. The second motor <NUM> is coupled to the third motor <NUM> to drive the third motor <NUM> to rotate relative to the second motor <NUM>, and a rotation axis of the third motor <NUM> substantially coincides with a rotation axis of the second motor <NUM>. The third motor <NUM> is arranged at a first end of the first leg part <NUM> (an upper end of the first leg part <NUM> as illustrated in <FIG>), the second leg part <NUM> is pivotably coupled to a second end of the first leg part <NUM> (a lower end of the first leg part <NUM> as illustrated in <FIG>), and the transmission component <NUM> is coupled to an output shaft <NUM> of the third motor and the second leg part <NUM>, to drive the second leg part <NUM> to rotate relative to the first leg part <NUM>.

It can be understood that, as illustrated in <FIG>, the rotation axis of the first motor <NUM> is parallel to a front-rear direction of the body assembly <NUM>, and the rotation axis of the second motor <NUM> is parallel to a left-right direction of the body assembly <NUM>, so that the first motor <NUM> can drive the second motor <NUM> and associated first leg part <NUM> and second leg part <NUM> to swing circumferentially around the front-rear direction of the body assembly <NUM>. Furthermore, the leg assembly <NUM> according to the embodiments of the present invention can complete actions of a "extension" and a "retraction", to increase the movement range of the first leg part <NUM> and the second leg part <NUM> within a space, improve the flexibility of the legged robot during motion, enable the legged robot to complete more complex actions, and improve the applicability of the legged robot.

As illustrated in <FIG>, the second motor <NUM> can drive the first leg part <NUM> to rotate relative to the body assembly <NUM>, and the third motor <NUM> can drive the second leg part <NUM> to rotate around the second end of the first leg part <NUM> through the transmission component <NUM>. Therefore, the leg assembly <NUM> according to the embodiments of the present invention can realize a walking action of the first leg part <NUM> and the second leg part <NUM> through the rotation of the first motor <NUM> and the second motor <NUM>.

In an embodiment, as illustrated in <FIG>, the leg assembly <NUM> further includes a first flange <NUM>, and the first flange <NUM> is coupled to the second motor <NUM> and located between the first motor <NUM> and the second motor <NUM>. The first flange <NUM> is provided with a first limit portion <NUM>, the first motor <NUM> is provided with a first stop portion <NUM> and a second stop portion <NUM>, and the first stop portion <NUM> and the second stop portion <NUM> are spaced apart, to limit a rotation angle of the second motor <NUM> by stopping the first limit portion <NUM>. In other words, the first stop portion <NUM> and the second stop portion <NUM> respectively define rotation limit positions of the first limit portion <NUM>. When the first limit portion <NUM> is stopped by the first stop portion <NUM> or the second stop portion <NUM>, a further rotation of the first flange <NUM>, i.e., a further rotation of the first motor <NUM> is prevented.

In the leg assembly <NUM> for the legged robot according to the embodiments of the present invention, since the first motor <NUM> is provided with the first stop portion <NUM> and the second stop portion <NUM>, a range of the rotation angle of the first flange <NUM> can be conveniently limited, to conveniently control a rotation amplitude of an "extension" action and a "retraction" action of the first leg part <NUM> and the second leg part <NUM>. Furthermore, it is more conducive to the accurate control of the leg assembly <NUM>, and the limit reliability of the leg assembly <NUM> during motion is improved.

In some embodiments, as illustrated in <FIG>, an angle α between a first coupling line L1 of the first stop portion <NUM> and a rotation center of the first motor <NUM> and a second coupling line L2 of the second stop <NUM> and the rotation center of the first motor <NUM> satisfies: <NUM> degrees ≤α≤ <NUM> degrees. It is found through experiments that a force and an impact applied to the leg assembly <NUM> are small, and the legged robot is relatively stable when walking, when the angle α between the first coupling line L1 and the second coupling line L2 is <NUM> degrees or <NUM> degrees.

In at least one embodiment, it is found through experiments that the force and impact applied to the leg assembly <NUM> are less, and the legged robot is more stable when walking, when the angle α between the first coupling line L1 and the second coupling line L2 is <NUM> degrees. Moreover, the angle set as above can make full use of their degrees of freedom, avoid interference, widen the movement range of the leg assembly <NUM>, and improve the motion stability of the legged robot.

Further, as illustrated in <FIG>, the first flange <NUM> is provided with a second limit portion <NUM>, and the leg assembly <NUM> further includes a second flange <NUM>. The second flange <NUM> is coupled to the third motor and is pivotable relative to an output shaft <NUM> of the second motor, and the second flange <NUM> is located between the second motor <NUM> and the third motor <NUM>. The second flange <NUM> is provided with a third stop portion <NUM> and a fourth stop portion <NUM>, and the third stop portion <NUM> and the fourth stop portion <NUM> are spaced apart, to limit a rotation angle of the third motor <NUM> by stopping the second limit portion <NUM>.

It can be understood that, as illustrated in <FIG>, <FIG>, the third stop portion <NUM> and the fourth stop portion <NUM> respectively define rotation limit positions of the second limit portion <NUM>. When the second limit portion <NUM> is stopped by the third stop portion <NUM> or the fourth stop portion <NUM>, a further rotation of the second flange <NUM> can be prevented. Therefore, in the leg assembly <NUM> for a legged robot according to the embodiments of the present invention, since the second flange <NUM> is provided with the third stop portion <NUM> and the fourth stop portion <NUM>, a range of a rotation angle of the second flange <NUM> can be conveniently limited, to conveniently control a swing amplitude of the first leg part <NUM>. Furthermore it is more conducive to the accurate control of the leg assembly <NUM> and the limit reliability of the leg assembly <NUM> during motion is improved.

In some embodiments, as illustrated in <FIG>, an angle β between a third coupling line L3 of the third stop portion <NUM> and a rotation center of the second motor <NUM>, and a fourth coupling line L4 of the fourth stop portion <NUM> and the rotation center of the second motor <NUM>, satisfies: satisfies: <NUM> degrees ≤ β ≤ <NUM> degrees. The inventors of the present invention found through experiments that the force and impact applied to the leg assembly <NUM> are small, and the legged robot is relatively stable when walking, when the angle β between the third coupling line L3 and the fourth coupling line L4 is <NUM> degrees or <NUM> degrees.

In at least one embodiment, it is found through experiments that the force and impact applied to the leg assembly <NUM> are less, and the legged robot is more stable when walking, when the angle β between the third coupling line L3 and the fourth coupling line L4 is <NUM> degrees. Moreover, the angle β set as above can make full use of their degrees of freedom, avoid the interference, widen the movement range of the leg assembly <NUM>, and improve the motion stability of the legged robot.

Further, as illustrated in <FIG>, the second limit portion <NUM> is substantially located on a coupling line between the first limit portion <NUM> and the rotation center of the first flange <NUM>. In other words, a coupling line between the second limit portion <NUM> and the center of the first flange <NUM> coincides with a coupling line between the first limit portion <NUM> and the center of the first flange <NUM>. Therefore, when machining the first flange <NUM>, the first limit portion <NUM> and the second limit portion <NUM> can be processed and formed more conveniently, thereby shortening the processing and manufacturing time of the first flange <NUM>. In addition, since the first limit portion <NUM> and the second limit portion <NUM> are substantially located at the same position, it is convenient for an operator to design and plan a motion trajectory when the leg assembly <NUM> rotates, to improve the controllability of the leg assembly <NUM> during motion.

In an embodiment, as illustrated in <FIG>, the first flange <NUM> includes a first coupling portion <NUM> and a second coupling portion <NUM>. The first coupling portion <NUM> is detachably coupled to the output shaft <NUM> of the first motor through a threaded member. The first coupling portion <NUM> is integrally formed with the second coupling portion <NUM>. The second coupling portion <NUM> is detachably coupled to a casing of the second motor <NUM> through the threaded member. The first limit portion <NUM> is located on the first coupling portion <NUM>, and the second limit portion <NUM> is located on the second coupling portion <NUM>. For example, the first coupling portion <NUM> is a disc-shaped member, and is detachably coupled to an end of the output shaft <NUM> of the first motor through the threaded member; the second coupling portion <NUM> is a ring-shaped member, and surrounds the casing of the second motor <NUM>; so that the coupling strength of the first flange <NUM> with the first motor <NUM> and the second motor <NUM> can be improved, and it is convenient for the assembly and the disassembly by the operator.

In some embodiments, as illustrated in <FIG>, the leg assembly <NUM> further includes a third flange <NUM>, and an output shaft <NUM> of the third motor is coupled to the third flange <NUM>, to drive the third flange <NUM> to rotate. The third flange <NUM> is provided with a third limit portion <NUM>, the first leg part <NUM> is provided with a fifth stop portion <NUM> and a sixth stop portion <NUM>, and the fifth stop portion <NUM> and the sixth stop portion <NUM> are spaced apart, to limit a rotation angle of the third motor <NUM> by stopping the third limit portion <NUM>. In other words, the fifth stop portion <NUM> and the sixth stop portion <NUM> respectively define rotation limit positions of the third limit portion <NUM>. When the third limit portion <NUM> is stopped by the fifth stop portion <NUM> or the sixth stop portion <NUM>, a further rotation of the third flange <NUM>, i.e., a further rotation of the third motor <NUM>, can be prevented.

In the leg assembly <NUM> for the legged robot according to the embodiments of the present invention, since the first leg part <NUM> is provided with the fifth stop portion <NUM> and the sixth stop portion <NUM>, a range of a rotation angle of the third flange <NUM> can be conveniently limited, to conveniently control a swing amplitude of the second leg part <NUM>. Furthermore, it is more conducive to the accurate control of the leg assembly <NUM> and the limit reliability of the leg assembly <NUM> during motion is improved.

As illustrated in <FIG>, an angle γ between a fifth coupling line L5 of the fifth stop portion <NUM> and a rotation center of the third motor <NUM> and a sixth coupling line L6 of the sixth stop portion <NUM> and the rotation center of the third motor <NUM> satisfies: <NUM> degrees ≤ γ ≤ <NUM> degrees. It is found through experiments that, the force and impact applied to the leg assembly <NUM> are small, and the legged robot is relatively stable when walking, when the angle γ between the fifth coupling line L5 and the sixth coupling line L6 is <NUM> degrees or <NUM> degrees.

In at least one embodiment, it is found through experiments that the force and impact applied to the leg assembly <NUM> are less, and the legged robot is more stable when walking, when the angle γ between the fifth coupling line L5 and the sixth coupling line L6 is <NUM> degrees. Moreover, the angle γ set as above can make full use of their degrees of freedom, avoid the interference, widen the movement range of the leg assembly <NUM>, and improve the motion stability of the legged robot.

In some embodiments, as illustrated in <FIG> and <FIG>, the transmission component <NUM> includes a coupling rod <NUM>, a first end (an upper end of the coupling rod <NUM> as illustrated in <FIG>) of the coupling rod <NUM> is pivotably coupled to the third flange <NUM> through a first pivot shaft <NUM>, and a second end of the coupling rod <NUM> is pivotably coupled to a first end (an upper end of the second leg part <NUM> as illustrated in <FIG>) of the second leg part <NUM> through a second pivot shaft <NUM>. The second end (the lower end of the first leg part <NUM> illustrated in <FIG>) of the first leg part <NUM> is pivotably coupled to the first end of the second leg part <NUM> through a third pivot shaft <NUM>.

In an embodiment, in <FIG> and <FIG>, the third pivot shaft <NUM> is located between the second pivot shaft <NUM> and a second end of the first leg part <NUM>, that is, the third pivot shaft <NUM> is closer to the second end (a lower end illustrated in <FIG>) of the first leg part <NUM> than the second pivot shaft <NUM>. When the third flange <NUM> rotates clockwise, the coupling rod <NUM> moves downward and drives the second pivot shaft <NUM> to move downward, to drive the second leg part <NUM> to swing clockwise around the third pivot shaft <NUM>, that is, the second leg part <NUM> is retracted relative to the first leg part <NUM>. On the contrary, when the third flange <NUM> rotates counterclockwise, the coupling rod <NUM> moves upward and drives the second pivot shaft <NUM> to move upward, to drive the second leg part <NUM> to swing counterclockwise around the third pivot shaft <NUM>, that is, the second leg part <NUM> is extended relative to the first leg part <NUM>.

In some embodiments, as illustrated in <FIG> and <FIG>, the third flange <NUM> is provided with a recessed portion <NUM>, an end of the recessed portion <NUM> is provided with a U-shaped fitting groove <NUM>, the first end (the upper end of the coupling rod <NUM> illustrated in <FIG>) of the coupling rod <NUM> is pivotably fitted in the U-shaped fitting groove <NUM>, and a surface of the recessed portion <NUM> can stop the coupling rod <NUM> to limit rotation of the second leg part <NUM>. It can be understood that, as illustrated in <FIG>, when the coupling rod <NUM> rotates, a side wall of the coupling rod <NUM> can abut against the surface of the recessed portion <NUM> to limit rotation of the coupling rod <NUM>, and then limit the rotation of the third flange <NUM> and the second leg part <NUM>, so that the reliability of the limit is further improved, the force and impact applied to respective members are reduced, and then the movement of the second leg part <NUM> can be controlled more accurately.

In some embodiments, as illustrated in <FIG>, the first leg part <NUM> includes an inner housing <NUM> and an outer housing <NUM>, and the third motor <NUM> is coupled to the inner housing <NUM>. The inner housing <NUM> and the outer housing <NUM> are coupled with each other and define a receiving cavity, and the transmission component <NUM> is arranged inside the receiving cavity, so that the transmission component <NUM> can be prevented from being exposed to the outside for a long time, and then the transmission stability of the leg assembly <NUM> is improved.

In an embodiment, as illustrated in <FIG>, the inner housing <NUM> and the outer housing <NUM> are detachably coupled through the threaded member, a circumferential wall of the receiving cavity is provided with crossed reinforcing ribs <NUM>, and the threaded member is located at a junction of the reinforcing ribs <NUM>, to further improve the coupling strength between the inner housing <NUM> and the outer housing <NUM> and then further improve the service life of the leg assembly <NUM> for a legged robot according to the embodiments of the present invention.

In some embodiments, an outer circumferential wall of the outer housing <NUM> is coated with a buffer layer (not illustrated), for example, the buffer layer can be covered on an upper end of the outer housing <NUM>, wherein the buffer layer can be a foam buffer layer or a rubber buffer layer, so that the legged robot can be buffered through the buffer layer when placed on the side or fallen down, thereby reducing the probability of the wear and the collision of the legged robot.

As illustrated in <FIG>, the legged robot <NUM> according to the embodiments of the present invention has four leg assemblies <NUM>, and the first motors <NUM> of the four leg assemblies <NUM> are all coupled to the body assembly <NUM>. It can be understood that, in the leg assembly <NUM>, the swing amplitude of the extension and the retraction of the first leg part <NUM> and the second leg part <NUM> can be adjusted by the first motor <NUM>, the second motor <NUM> controls the first leg part <NUM> to rotate relative to the body assembly <NUM>, and the third motor <NUM> drives the second leg part <NUM> to rotate relative to the first leg part <NUM>, to realize actions such as the walking of the robot. The legged robot <NUM> according to the embodiments of the present invention has a wide movement range, good practicability, a reliable limit, the force and impact applied to various components are small, the operation is stable and the control precision is high.

In the description of the present invention, 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 illustrated 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 invention.

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 invention, unless otherwise specifically defined, "a plurality of" means at least two, such as two, three, etc..

In the present invention, unless otherwise explicitly specified and defined, the terms "mounted," "coupled," "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 invention, 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 invention, 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 invention. 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 invention. 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.

Claim 1:
A leg assembly (<NUM>) for a legged robot (<NUM>), comprising:
a first motor (<NUM>), a second motor (<NUM>) and a third motor (<NUM>), the first motor (<NUM>) being coupled to the second motor (<NUM>) to drive the second motor (<NUM>) to rotate relative to the first motor (<NUM>), a rotation axis of the first motor (<NUM>) being substantially orthogonal to a rotation axis of the second motor (<NUM>), the second motor (<NUM>) being coupled to the third motor (<NUM>) to drive the third motor (<NUM>) to rotate relative to the second motor (<NUM>), a rotation axis of the third motor (<NUM>) substantially coinciding with the rotation axis of the second motor (<NUM>); and
a first leg part (<NUM>), a second leg part (<NUM>) and a transmission component (<NUM>), the third motor (<NUM>) being arranged at a first end of the first leg part (<NUM>), the second leg part (<NUM>) is pivotably coupled to a second end of the first leg part (<NUM>), the transmission component (<NUM>) being coupled to an output shaft (<NUM>) of the third motor (<NUM>) and the second leg part (<NUM>) to drive the second leg part (<NUM>) to rotate relative to the first leg part (<NUM>),
characterized in that the leg assembly (<NUM>) further comprises a first flange (<NUM>) coupled to the second motor (<NUM>) and located between the first motor (<NUM>) and the second motor (<NUM>), the first flange (<NUM>) is provided with a first limit portion (<NUM>), the first motor (<NUM>) is provided with a first stop portion (<NUM>) and a second stop portion (<NUM>), the first stop portion (<NUM>) and the second stop portion (<NUM>) are spaced apart to limit a rotation angle of the second motor (<NUM>) by stopping the first limit portion (<NUM>),
wherein the first flange (<NUM>) is provided with a second limit portion (<NUM>), the leg assembly (<NUM>) further comprises a second flange (<NUM>) coupled to the third motor (<NUM>) and located between the second motor (<NUM>) and the third motor (<NUM>), the second flange (<NUM>) is provided with a third stop portion (<NUM>) and a fourth stop portion (<NUM>), and the third stop portion (<NUM>) and the fourth stop portion (<NUM>) are spaced apart to limit a rotation angle of the third motor (<NUM>) by stopping the second limit portion (<NUM>), and
wherein the second limit portion (<NUM>) is substantially located on a coupling line between the first limit portion (<NUM>) and a rotation center of the first flange (<NUM>).