阅读说明：本技术 一种四足机器人可控多点接触地面的腿部结构及控制方法 (Leg structure of controllable multi-point contact ground of quadruped robot and control method ) 是由 李延博 于 2021-09-16 设计创作，主要内容包括：本公开的实施例,提供一种四足机器人可控多点接触地面的腿部结构及控制方法,小臂包括两个或两个以上彼此分离的地面接触点；多个地面接触点可独立驱动；本公开具有结构简单,可靠性高,并具备低成本大规模制造的可能性；本公开兼容传统四足机器人的高通过性,传统控制可直接移植到本公开应用上；除此之外,传统四足机器人属于欠驱动系统,上身有6个自由度,但却只能提供5个独立控制。而本公开可以令四足机器人具备全时且持续的上身全部6自由度的6个独立控制。本公开使得四足机器人以简单的整体布局实现全驱动系统,在不影响传统四足机器人高通过性,高适应性的同时,极大的提高了四足机器人的稳定性。(The embodiment of the disclosure provides a leg structure of a quadruped robot with controllable multi-point contact with the ground and a control method thereof, wherein a small arm comprises two or more ground contact points separated from each other; the plurality of ground contact points can be driven independently; the present disclosure has the advantages of simple structure, high reliability, and low cost and large scale manufacturing possibility; the method is compatible with the high trafficability of the traditional quadruped robot, and the traditional control can be directly transplanted to the application of the method; in addition, the traditional quadruped robot belongs to an under-actuated system, and the upper body has 6 degrees of freedom but can only provide 5 independent controls. The present disclosure allows the four-legged robot to have 6 independent controls of 6 degrees of freedom for all the upper body, which are continuous and all the time. This disclosure makes the four-footed robot realize full actuating system with simple overall arrangement, when not influencing the high trafficability characteristic of traditional four-footed robot, high adaptability, very big improvement four-footed robot's stability.)

1. A controllable multi-point contact ground leg structure of a quadruped robot is characterized in that each single leg comprises an upper arm and at least two lower arms hinged to the upper arm;

the upper arm has a yaw and pitch drive unit;

each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

2. A controllable multi-point contact ground leg structure of a quadruped robot is characterized by comprising an upper arm, a middle arm and at least two lower arms hinged to the middle arm;

the upper arm has a yaw and pitch drive unit;

the middle arm is hinged to the upper arm;

each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

3. The controllable multi-point contact leg structure of the quadruped robot as claimed in claim 1 or 2, wherein the number of the lower arms is two, the two lower arms are independently driven, and the inclination angles of the two lower arms are independently controlled and can be changed to be equal or unequal.

4. A controllable multi-point contact leg structure of a quadruped robot as claimed in claim 1 or 2, wherein the number of the lower arms is 3, 3 of the lower arms are independently driven or only the two lower arms on the outer side are independently driven;

or the lower arms are 4, and the 4 lower arms are independently driven or only the two lower arms at the outer side are independently driven.

5. The controllable multi-point ground contact leg structure of a quadruped robot as claimed in claim 1 or 2, wherein each of the lower arms is a symmetrical structure or an asymmetrical structure; further, the respective lower arms may be identical or different in structure; further, the lower arms are the same or different in length and height.

6. The controllable multi-point contact ground leg structure of a quadruped robot as claimed in claim 1, wherein the driving unit of the lower arm is mounted on the upper arm and transmits power mechanically. Furthermore, the mechanical mode is the direct drive of a connecting rod transmission, a chain transmission, a synchronous belt transmission, a ball screw slide block connecting rod transmission and a transmission mechanism-free actuator.

7. The controllable multi-point ground contact leg structure of a quadruped robot as claimed in claim 1, wherein the upper arm comprises a first arm lever, a second arm lever, a first drive unit, a second drive unit, a first transmission member and a second transmission member;

a first transmission part and a second transmission part are arranged in a space between the first arm lever and the second arm lever; the first driving unit drives the first lower arm through the first transmission part, and the second driving unit drives the second lower arm through the second transmission part;

the first lower arm and the second lower arm are two lower arms outside the lower arm.

8. The controllable multi-point contact leg structure of the quadruped robot as claimed in claim 2, wherein the driving unit of the lower arm is mounted on any part of the upper arm or the middle arm, and transmits power mechanically. Furthermore, the mechanical mode is link transmission, chain transmission, synchronous belt transmission, ball screw slider link transmission, and actuator direct drive without transmission mechanism.

9. A quadruped robot characterized in that at least one leg adopts a leg structure of the quadruped robot controllable multi-point contact ground as claimed in one of claims 1 to 8.

10. The quadruped robot of claim 9 wherein the leg structure knee is free to flex. Further, the knee is partially flexed anteriorly, partially flexed posteriorly or fully flexed posteriorly, or fully flexed anteriorly.

11. A method of controlling the quadruped robot according to claim 9 or 10, comprising: each forearm in a single leg structure is simultaneously grounded to form an equivalent virtual landing point;

the two lower arms on the outer side of each leg structure are respectively a first lower arm and a second lower arm which are driven independently, and a first driving moment and a second driving moment are applied to the first lower arm and the second lower arm respectively; and adjusting the difference value of the first driving moment and the second driving moment so as to adjust the position of the virtual landing point.

12. A quadruped robot control method according to claim 10, wherein when the leg structure is swung in the air away from the ground, the first lower arm and the second lower arm move synchronously at substantially the same angle to the upper arm, which is equivalent to the same lower arm.

Technical Field

The embodiment of the disclosure relates to the technical field of robots, in particular to a leg structure of a quadruped robot in controllable multi-point contact with the ground and a control method.

Background

At present, the contact mode of each leg of the existing high-performance quadruped robot with the ground is mostly single-point (or single-area) contact. Quadruped robots, in which a single leg is in contact with the ground at a plurality of independently controllable separation points (or separation areas), are rare because the mechanical structure of such legs is complicated and difficult to drive. It is difficult to meet high performance sports requirements.

The prior art has the following defects:

(1) the sole single contact of traditional four-footed robot easily appears sliding, seriously influences the stability of robot.

(2) Traditional single contact point quadruped robots, such as the boston power Spot, or MIT mini-Cheetah, are under-actuated robotic systems. Although the traditional four-foot robot system has 12 or more than 12 actuating actuators, the traditional structure enables the robot to have only 5 independent control functions when the robot stands on two feet and lifts the legs. And the upper body of the robot has 6 independent degrees of freedom in space. That is, the conventional quadruped robot is not fully controllable at any moment when walking in a diagonal gait or a unilateral gait. Under-actuation is the root cause of the problems of influencing the walking stability, the trafficability characteristic and the control robustness of the traditional four-footed robot.

(3) Some existing single-leg single-contact-surface quadruped robots such as CN108001560A have 6 fully controllable degrees of freedom, but the structural composition is too complex. The weight of itself increases significantly. The mass distribution of the single leg is limited by the mechanical structure of the scheme, the gravity center of the single leg has to be far away from the body, and the requirement of high-performance dynamics is difficult to meet.

Some existing single-leg multi-point contact surface quadruped robots, such as CN113129729A, cannot achieve 6 independent degrees of freedom which can be controlled completely. The first finger and the second finger of one leg of the hand-operated electric tool are meshed through a gear. One driving unit drives two fingers, and thus the two fingers are not independently driven.

Disclosure of Invention

To solve the problems in the prior art, the embodiment of the present disclosure provides a leg structure and a control method for a quadruped robot with controllable multiple points in contact with the ground, so as to realize single-leg multiple point contact with the ground, and enable the quadruped robot to have a completely controllable driving capability with 6 degrees of freedom.

To achieve the above objects, the present disclosure provides in one aspect a leg structure of a quadruped robot for controllable multi-point contact with the ground, each single leg including an upper arm and at least two lower arms hinged to the upper arm;

the upper arm has a yaw and pitch drive unit;

each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

The leg structure of the controllable multi-point contact ground of the quadruped robot is characterized by comprising an upper arm, a middle arm and at least two lower arms hinged to the middle arm;

the upper arm has a yaw and pitch drive unit;

the middle arm is hinged to the upper arm;

each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

A fourth aspect of the present disclosure provides a quadruped robot, wherein at least one leg is a controllable multi-point contact leg structure of the quadruped robot.

A fourth aspect of the present disclosure provides a method for controlling the quadruped robot, including: each forearm in a single leg structure is simultaneously grounded to form an equivalent virtual landing point;

the two lower arms on the outer side of each leg structure are respectively a first lower arm and a second lower arm which are driven independently, and a first driving moment and a second driving moment are applied to the first lower arm and the second lower arm respectively; and adjusting the difference value of the first driving moment and the second driving moment so as to adjust the position of the virtual landing point.

The technical scheme of the disclosure has the following beneficial technical effects:

(1) the leg structure of the robot disclosed by the invention is in multipoint contact with the ground, so that the robot has better ground grabbing force on a complex and changeable road surface, and the foot bottom is not easy to slide.

(2) Compared with the traditional single-leg single-point contact, the single-leg multi-point contact can provide more road information for the robot, and can obviously improve the accuracy of the position and posture estimation of the robot. .

(3) The mass distribution of the robot legs is mainly concentrated on the connecting parts of the legs and the body structure, so that the moment of inertia of the legs during swinging can be obviously reduced, and the robot can run and jump at high speed.

(4) The robot adopting the leg structure can decouple the roll angle control (roll control) of the upper body of the robot and the lateral horizontal control (horizontal control in the z direction) of the upper body of the robot. The control mode of the quadruped robot is greatly simplified, and the complete decoupling control effect which cannot be achieved by the traditional quadruped robot is obtained.

(5) The traditional four-foot robot belongs to an under-actuated system, and the upper body has 6 degrees of freedom but can only provide 5 independent controls. The present disclosure allows the four-legged robot to have 6 independent controls of 6 degrees of freedom for all the upper body, which are continuous and all the time. This disclosure makes the four-footed robot realize full actuating system with simple overall arrangement, when not influencing the high trafficability characteristic of traditional four-footed robot, high adaptability, very big improvement four-footed robot's stability.

Drawings

FIG. 1 is a side view of a one-leg multi-contact quadruped robot in one embodiment;

FIG. 2 is a front schematic view of the single-leg multi-contact quadruped robot of FIG. 1;

FIG. 3 is a schematic diagram of the mechanical mechanism of the quadruped robot in one embodiment;

FIG. 4 is a schematic view of a chain drive;

fig. 5(a) is a schematic diagram illustrating a leg force principle of a conventional single contact point, and fig. 5(b) is a schematic diagram illustrating a leg force principle of a multi-contact point;

FIG. 6(a) shows the torques T and F of the conventional quadruped robot_zA relationship diagram; FIG. 6(b) is a diagram illustrating quadruped robot torques T and F when forces are generated to push the robot body laterally in the disclosed embodiment_zA relationship diagram;

FIG. 6(c) is a graph of quadruped robot torques T and F for generating a robot roll torque without requiring a traverse in an embodiment of the disclosure_zA relationship diagram;

FIG. 7 is an exploded view of a leg structure of an embodiment of the chain drive;

FIG. 8 is a schematic view of a leg structure of an embodiment of a linkage;

FIG. 9(a) is a conventional spider-like quadruped robot; fig. 9(b) is a spider-like quadruped robot employing the leg structure of the present disclosure.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, the present disclosure will be described in further detail below with reference to the accompanying drawings in conjunction with the detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

In describing embodiments of the present disclosure, the terms "include" and its derivatives should be interpreted as being inclusive, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like may refer to different or the same object. Other explicit and implicit definitions are also possible below.

The present disclosure provides a controllable multi-point contact ground leg structure of a quadruped robot, comprising an upper arm and at least two lower arms hinged to the upper arm; the upper arm has a yaw and pitch drive unit; each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

The present disclosure provides yet another controllable multi-point ground contact leg structure of a quadruped robot, which includes an upper arm, a middle arm, and at least two lower arms hinged to the middle arm. The upper arm has a yaw and pitch drive unit; the middle arm is hinged to the upper arm; each lower arm has a foot end, and at least two lower arms can independently drive the front and back swinging.

Further, for a leg structure comprising 2 independent lower arm sections. The 2 lower arms are respectively provided with independent driving units. The two lower arms have independently controllable degrees of freedom relative to the upper or middle arm to which they are hinged. In other words, the included angle 1 between the first lower arm and the upper arm (or the middle arm) and the included angle 2 between the second lower arm and the upper arm (or the middle arm) can be equal or unequal by controlling the driving unit.

Further, for a vehicle comprising more than 2 (3, 4 …) independent lower arms. Of these 2 lower arms, an independent drive unit must be installed, and the remaining lower arms may or may not be installed with drive units. Preferably, at least the outer two lower arms have a drive unit.

Further, the structural body of the single small arm can adopt a symmetrical structure, such as MIT Cheetah-3, and also can adopt an asymmetrical structure, such as Boston dynamic Spot.

Further, the outer shapes of the small arms may be similar or dissimilar. Even the length of the small arms may or may not be the same.

Further, the drive unit for the lower arm is usually mounted on the upper arm, close to the upper body, and transmits power by some mechanical means to reduce the moment of inertia of the entire leg structure. The transmission form of the lower arm drive unit includes, but is not limited to: a link drive, such as the drive form of MIT Cheetah-2; chain drives, such as the drive form MIT Cheetah-3; synchronous belt drives, such as the MITmini-Cheetah drive format; ball screw slider link drives, such as the form of the Boston power Spot drive; the gearless actuator drives directly, for example in the form of an ANYbotics ANYmal, and the drive unit is mounted directly at the hinge of the lower arm and the upper arm. Further, the drive unit of the lower arm may be mounted on any part of the upper or middle arm, transmitting power mechanically.

The single leg of the quadruped robot is in controllable multipoint contact with the ground contact area. The virtual contact surface is formed by the multipoint contact of the front leg and the rear leg when two feet stand, so that the four-footed robot can have independent 6 complete controllable degrees of freedom at any time and any place. The four-foot robot is changed from a traditional underactuated system into a full-time fully controllable system.

One or more groups of small arm structures are additionally arranged on the leg structure of the traditional quadruped robot. So that the increase of the mass of the single leg is very limited. More importantly, all the driving units can be arranged at the root of the combination of the leg structure and the body, so that the moment of inertia of the whole leg can be reduced, and the dynamic requirement of the high-performance quadruped robot can be met.

Further, at least one leg of the four legs of the quadruped robot adopts a controllable multipoint contact leg structure of the quadruped robot. The knee bending direction of the quadruped robot is arbitrary, and the knee bending part is bent forwards, and is partially bent backwards or is completely bent backwards, or is completely bent forwards.

In one embodiment, the overall freedom degree distribution structure of the single-leg multi-contact-point quadruped robot is shown in fig. 3. The quadruped robot has 4 degrees of freedom and 4 actuating units for each leg structure. The robot has 16 degrees of freedom and 16 actuating units. With 2 coaxial rotational degrees of freedom for each leg structure knee portion.

Taking one of the legs as an example, the 4 degrees of freedom are (r) degrees of freedom for swinging the leg left and right. The freedom of the leg to swing back and forth is two. The degree of freedom (c) and the degree of freedom (d) are coaxial and are degrees of freedom for independent swinging of the two small arms and the large arm respectively.

A single leg structure is illustrated in fig. 4. The structural body 1-1 of the big arm is connected with 2 independent small arms 2-1 and 3-1 at the knee part. The small arm 2-1 is driven by an actuating unit 2-3 via a chain. The small arm 3-1 is driven by the actuator unit 3-3 through a chain. Two actuating units 1-2 and 1-3 of the large arm are controlled, the actuating unit 1-2 is responsible for the front-back swing of the whole leg, corresponding to the degree of freedom II in the figure 3, and the actuating unit 1-3 is responsible for the left-right swing of the whole leg, corresponding to the degree of freedom I in the figure 3.

During robot walking, the multiple lower arms in each single leg of the disclosed leg structure land almost always simultaneously when the robot leg supports the body. The small arms which land on the ground simultaneously provide supporting force, and an equivalent virtual landing point is formed together. When the leg is lifted and swung, the small arms are also lifted almost simultaneously.

Fig. 5 shows the difference of the leg structure force principle of the disclosed robot compared to the leg structure force principle of the conventional quadruped robot. The traditional four-footed robot leg structure is in single point O contact with the ground. The leg structure can adjust the moment T generated by three degrees of freedom₁,T₂,T₃Can be produced at the terminal OGenerating a force F acting on the ground_leg. The direction of the force is from T₁,T₂,T₃May be in any direction. But the force F_legThe O point must be passed.

The leg structure in this disclosure is in contact with the ground at multiple points, as shown in fig. 5b as O₁And O₂. The leg structure in this disclosure generates a force F on the ground_leg. Due to T₃And T₄Is coaxial, then T₃+T₄Resultant torque T₃₄T equivalent to conventional leg₃. Thus F_legThe direction of action of (c) is also arbitrary. From the force analysis, the equivalent action point O of the leg structure in the present disclosure_vMust be at the actual action point O₁And O₂The line segments are two end points. O is_vBy simple analysis, the specific location of (A) is known as T₃And T₄Linear combination control of (2). For example if T₃＝0，T₄Not equal to 0, then O_vAt O₂At least one of (1) and (b); if T₃≠0，T₄When the value is 0, then O_vAt O₁At least one of (1) and (b); if T₃＝T₄Then O is_vAt O₁And O₂At the midpoint of (a).

It can be seen that the leg structure in the present disclosure relaxes the constraints on the point of application of the force relative to a conventional single point contact leg. The constraint that the previous acting force must pass through the O point is changed into the constraint that the acting force only passes through the O₁,O₂Any point in between. The new function of the present disclosure added to a four-legged robot to be able to arbitrarily select the force application point without moving the actual foot landing point provides the robot with the previously missing control capabilities.

Fig. 6 illustrates the difference between a conventional four-footed robot leg and the leg control model of the four-footed robot of the present disclosure. The legs of the robot need to generate force F for supporting the body when standing_lThe force needs to always pass through the contact point O and be directed towards the robot center of gravity. For a conventional quadruped robot, as shown in fig. 6a, when the robot needs to generate a horizontal control force F_zWhen the robot leg generates F_lAnd F_zTwo forces, the resultant of which is shown in fig. 6 a. Obviously, the resultant force cannot pass through the center of gravity of the robot because the force must pass through the limit of the point O, and therefore, a torque is generated to rotate the robot counterclockwise. This torque will force the robot body to roll undesirably. This torque is a torque that disturbs stabilization. On the other hand, when the robot body needs to roll, the legs must generate a torque about the center of gravity M. Due to the limitation that the force must pass the O-point, the leg can only generate a force that passes the O-point and is offset from the center of gravity, as is still shown in fig. 6 a. However, the negative effect is that the roll-generating force generated by the conventional leg also has a component F in the horizontal direction_z. It will inevitably push the centre of gravity sideways to the right.

That is, when it is desired to push the robot sideways, the leg may produce an undesirable roll torque. When only a roll is desired, the legs have to produce a detrimental lateral pushing horizontal force. The two effects can only occur simultaneously, which is a structural defect that the traditional four-foot robot cannot overcome.

On the other hand, the present disclosure proposes a controllable multi-point contact ground leg structure as shown in fig. 6b and 6 c. When it is desired to generate only a force pushing the robot body sideways (see fig. 6b), the leg structure may be generated through the virtual contact point O_vAnd through the force of the center of gravity M. As long as T is reasonably distributed by calculation₃,T₄The value of (a), i.e. the equivalent contact point O of the leg structure_vTo O₁Close. The horizontal component of this force may cause the effect of horizontal lateral pushing. And because of the over center of gravity, the force does not produce a rolling effect. Similarly, when only the torque for rolling the robot needs to be generated but the transverse pushing is not needed (as shown in FIG. 6c), only the T is reasonably distributed through calculation₃,T₄Of such that the equivalent contact point O is_vTo O₂Approach and maintain the direction of force and F_lParallel. In this way, the force generated by the legs only generates a rolling torque and not a lateral thrust.

In other words, when the multi-point contact four-footed robot of the present disclosure stands on the ground, the present disclosure enables virtual contact of the leg structure with the ground without moving the actual position of the feetContact O_v(the point of action of the equivalent force) to the desired position. Moving O_vThe lateral push and roll coupling limits may be disengaged. Both no longer have to occur simultaneously.

Estimate with typical machine parameters: for example, a quadruped robot with a height of 0.4 m and a self-weight of 30kg when walking can have a lateral boosting acceleration of + -0.1 g at any time and will not cause negative roll disturbance if the distance between the two contact points of one leg is 8 cm, as shown in fig. 6 b. Likewise, the robot may also be provided with roll correction torque of about ± 12 nm without creating negative disturbances of side-to-side thrust, as shown in fig. 6 c. Thereby greatly improving the stability of the quadruped robot at any moment.

In the embodiment shown in fig. 7, a chain drive scheme is employed. The large arm structural body 1-1 is connected to two independent small arms 2-1 and 3-1. A knee main shaft 1-4 penetrating the knee is arranged, and the large arm and the two small arms are hinged on the knee shaft through a plurality of bearings. The rotational degrees of freedom of the two small arms relative to the large arm are coaxial and collinear with the principal axes 1-4 of the knee.

The stator part of the actuator 2-3 is mounted on the large arm 1-1, and its rotor is rigidly mounted on the 2-4 sprocket. The two chain wheels 2-4 and 2-5 are respectively meshed with the chain 2-2 to form a transmission mechanism. The lower chain wheel 2-5 is rigidly connected with the small arm 2-1. The actuator 2-3 drives the small arm 2-1 to swing back and forth.

Similarly, the stator part of the actuator 3-3 is mounted on the large arm 1-1, and its rotor is rigidly mounted on the 3-4 sprocket. The two chain wheels 3-4 and 3-5 are respectively meshed with the chain 3-2 to form a transmission mechanism. The lower chain wheel 3-5 is rigidly connected with the small arm 3-1. The actuator 3-3 drives the small arm 3-1 to swing back and forth.

In the embodiment shown in fig. 8, a link drive is used. Similar to fig. 7, the link 2-6 in fig. 8 replaces the chain 2-2 in fig. 7 to complete the transmission of the actuator 2-3 and the small arm 2-1.

The link 3-6 in fig. 8 replaces the chain 3-2 in fig. 7 to complete the transmission of the actuator 3-3 and the small arm 3-1.

Another aspect provides a quadruped robot driving control method, including: each forearm of each leg structure is simultaneously grounded to form an equivalent virtual landing point; the two lower arms on the outer side of each leg structure are respectively a first lower arm and a second lower arm which are driven independently, and a first driving torque and a second driving torque are coaxially applied to the first lower arm and the second lower arm respectively; and adjusting the difference value of the first driving moment and the second driving moment so as to adjust the position of the virtual landing point. Further, when the difference between the first driving force and the second driving force is 0, the equivalent virtual landing point is located at the midpoint of the connecting line of the foot end of the first lower arm and the foot end of the second lower arm.

When the robot leg structure is swung in the air off the ground, the forearm 1 and the forearm 2 are considered as a virtual forearm. At this time, the included angles between the two small arms and the upper arm are always equal. At this time, the leg of the present disclosure is equivalent to a leg of a conventional four-legged robot, and the swing leg planning algorithm and control strategy of the conventional four-legged robot are applied with the middle point of the foot ends of the two lower arms as the foot drop point to be planned.

Force control is applied to both legs grounded when the robot leg structure contacts the ground. At the moment, 6 control targets of the mass center are obtained through the upper body algorithm of the quadruped robot: 1 vertical supporting force, 2 horizontal thrusts and 3 torques required by 3 direction angle control. The 6 target forces/moments are calculated by robot inverse dynamics (or by using various popular algorithms such as WBC, WBIC and the like), so that target torques of 16 degrees of freedom in total can be obtained for each joint of the two landing support legs and the two swinging legs respectively. The actuator is commanded to execute the command to complete the control.

This step of calculation is relatively unsatisfactory for a conventional quadruped robot. For a traditional quadruped robot, any algorithm can only meet 5 or 4 of the 6 control targets of the upper body, and 1 or 2 targets need to be abandoned. And then the actuating unit executes the target torque which is calculated by the inverse dynamics and corresponds to the degree of freedom.

From another perspective, for landing the leg-leg structure of the quadruped robot to which the present disclosure is applied, direct moment control (or pseudo moment control) is employed for four degrees of freedom of a single leg. At the moment, the included angle 1 between the small arm 1 and the large arm and the included angle 2 between the small arm 2 and the large arm can be changed spontaneously along with the dynamic constraint of each part of the robot body. In this case, the angle of the two angles, or their angular velocities, does not require active intervention. The included angles 1 and 2 are changed at any time, and may be equal or unequal.

Only when the four-legged robot of the present disclosure is applied to leg-lifting swing, position and speed control need be employed for four degrees of freedom of a single leg. At this time, the included angle 1 and the included angle 2 may be always equal.

Fig. 9b shows another possible overall solution for composing a quadruped robot using the legs of the present disclosure. Spider-like robots are also the more popular four-legged robot solution. Compared with a robot of a mechanical dog type, the spider type robot is characterized in that the working space of the legs is larger, and the theoretical trafficability characteristic is higher. But the hardware requirements for each joint and structure are more demanding. Such robots may also employ the multi-contact point scheme described in this disclosure. Similar to the robotic dog solution, such robots differ only in the relative lengths of the large and small arms. The control strategies are similar, and the behavior and the effect are also similar.

In short, the small arms of each leg in this configuration are also grounded at approximately the same time, while being lifted off the ground. The multiple small arms in the single leg provide supporting force simultaneously, and together form an equivalent virtual landing point.

In summary, the present disclosure relates to a leg structure of a four-legged robot with controllable multi-point contact with the ground and a control method thereof, wherein the small arm comprises two or more ground contact points; the plurality of ground contact points can be driven independently; the present disclosure has the advantages of simple structure, high reliability, and low cost and large scale manufacturing possibility; the method is compatible with the high trafficability of the traditional quadruped robot, and the traditional control can be directly transplanted to the application of the method; in addition, the traditional quadruped robot belongs to an under-actuated system, and the upper body has 6 degrees of freedom but can only provide 5 independent controls. The present disclosure allows the four-legged robot to have 6 independent controls of all 6 degrees of freedom in all time and continuously. This disclosure makes the four-footed robot realize full actuating system with simple overall arrangement, when not influencing the high trafficability characteristic of traditional four-footed robot, high adaptability, very big improvement four-footed robot's stability.

It is noted that the present disclosure is directed to the design of a controllable multi-point contact quadruped robot structure. The control strategy provided above is but one of many possible control strategies that may be used with the present disclosure. Its purpose is to present some of the unique designs of the disclosure and its role, not to limit the disclosure.

It is to be understood that the above-described specific embodiments of the present disclosure are merely illustrative of or illustrative of the principles of the present disclosure and are not to be construed as limiting the present disclosure. Accordingly, any modification, equivalent replacement, improvement or the like made without departing from the spirit and scope of the present disclosure should be included in the protection scope of the present disclosure. Further, it is intended that the following claims cover all such variations and modifications that fall within the scope and bounds of the appended claims, or equivalents of such scope and bounds.