A quadruped passive walking robot

Abstract

The application relates to a quadruped passive walking robot, which comprises a square trunk and left front legs, right front legs, left rear legs and right rear legs rotatably connected at four corners of the trunk, wherein the left front legs, the right front legs, the left rear legs and the right rear legs are of the same structure and each comprises a leg unit and a foot unit; the leg unit is rotatably connected with the trunk to form a hip joint, the foot unit is fixedly connected with the leg unit, the bottom surface of the foot unit is a stepped arc surface composed of an inner arc surface and an outer arc surface, and the inner arc surface is lower than the outer arc surface. According to the above technical scheme, the walking robot has good continuity, periodicity and gait stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of walking robots, in particular to a four-legged passive walking robot. BACKGROUND

[0002] Passive walking robots are simple mechanical devices composed of solid links connected by joints, which can achieve stable walking on a downward inclined plane only by relying on gravity. They have no motors and controllers, and only rely on gravitational potential energy to compensate for energy loss caused by collisions and friction during walking, and achieve periodic walking by their own mechanical structure and mass distribution. The energy consumed by the unit weight to move a unit distance is comparable to that of human walking, which makes their walking efficiency exceed that of any previous walking machine.

[0003] Pure passive walking robots refer to a method of using complete passive dynamics, in which all joints of the robot do not need to be driven, and only rely on the dynamic characteristics between the robot and the environment to achieve self-walking. Since there is no energy input, in order to overcome friction and energy loss when the foot touches the ground, self-walking can only be achieved when going up and down the slope, at which time the gravitational potential energy compensates for the energy loss.

[0004] The existing pure passive robots are mainly two-legged "ladder" structures. This structure requires a high slope, and in order to switch between the supporting leg and the swinging leg, it can only meet the theoretical walking conditions on a slope with alternating high and low arrangements, and the two-legged stability is extremely poor, which cannot achieve continuous walking. Chinese patent CN118419171A discloses a passive walking device on an inclined plane. This device uses a transverse circular surface as the foot, and has obvious defects. First, it can only walk four or five steps on the slope, which is extremely unstable and cannot continue walking. The reason is that the longitudinal "pendulum" swing and the transverse "tumbler" swing cannot be effectively combined, and the gravitational potential energy cannot provide energy for the transverse swing. The essential reason lies in the design defect of the transverse circular foot. This design will inevitably stop the transverse swing due to friction and collision loss. Second, the mass distribution of the device is unreasonable, which leads to instability during walking. The asymmetric gait during walking will quickly cause the device to fall. Third, the friction of the foot is insufficient, and there is sliding between the foot of the device and the slope during walking. When the supporting leg and the swinging leg are switched, the supporting leg is still in motion of sliding and rolling, which causes the device to lose balance during gait switching. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned drawbacks and provide a four-legged passive walking robot. The robot does not need to be driven, and only relies on its own gravity and structural design to achieve stable and periodic continuous walking on a slope, and can self-adjust the initial state.

[0006] To achieve the above object, the present application adopts the following technical scheme: including a square trunk and left front leg, right front leg, left rear leg and right rear leg rotatably connected at four corners of the trunk, the left front leg and the right front leg, the left rear leg and the right rear leg are symmetrically arranged along the vertical midline of the trunk respectively, the left front leg and the left rear leg, the right front leg and the right rear leg are symmetrically arranged along the horizontal midline of the trunk respectively, the left front leg, the right front leg, the left rear leg and the right rear leg are the same structure, and each includes a leg unit and a foot unit;

[0007] The leg unit and the trunk are rotatably connected to form a hip joint, and a left restraint rod is arranged between the leg units of the left front leg and the left rear leg and rotatably connected with both, and a right restraint rod is arranged between the leg units of the right front leg and the right rear leg and rotatably connected with both.

[0008] The foot unit is fixedly connected with the leg unit, the bottom surface of the foot unit is a stepped arc surface composed of an inner arc surface and an outer arc surface, the inner arc surface is lower than the outer arc surface, the center of the inner arc surface and the center of the outer arc surface are located on the central axis of the leg unit, and the curvature radius of the inner arc surface and the outer arc surface is equal, which should be greater than the distance from the lowest point of the inner arc surface to the hip joint.

[0009] The left front leg and the right front leg are connected by a first joint shaft, the left rear leg and the right rear leg are connected by a second joint shaft, the first joint shaft and the second joint shaft are parallel to the horizontal midline of the trunk, and the first joint shaft and the second joint shaft pass through the trunk.

[0010] The left front leg and the right front leg are connected with the first joint shaft through a left connecting assembly and a right connecting assembly respectively, the left connecting assembly and the right connecting assembly are symmetrically arranged and each includes a first anti-slip sleeve, a first bearing and a second anti-slip sleeve arranged on the first joint shaft in sequence, the first anti-slip sleeve and the second anti-slip sleeve are tightly fitted with the first joint shaft, the first anti-slip sleeve in the left connecting assembly and the right connecting assembly cooperates to limit the axial movement of the first joint shaft, and the second anti-slip sleeve cooperates with the first anti-slip sleeve to limit the axial movement of the first bearing.

[0011] The first bearing is provided in two groups, and the two groups of first bearings are positioned by a third anti-slip sleeve, and the third anti-slip sleeve is tightly fitted with the first joint shaft.

[0012] The trunk is provided with right-angle notches at four corners to connect the leg units and limit the forward and backward swing angles of the leg units, and the maximum swing angles of the leg units moving forward and backward are the same, which are 15°-35°.

[0013] A through hole is arranged at the center position of the trunk, and the center of mass of the trunk coincides with the center of the trunk.

[0014] The left and right constraint rods are respectively provided with connecting rods connected with the leg units, and the connecting rods are connected with the leg units through fixing caps.

[0015] The leg unit comprises a first rod body with a square cross section and a second rod body with a circular cross section, the first rod body is provided with a first connecting hole and a second connecting hole from top to bottom, wherein the first connecting hole is connected with the corresponding left or right constraint rod, the second connecting hole is connected with the corresponding first or second joint shaft, and the second connecting holes are equidistantly arranged in multiple groups.

[0016] The bottom surface of the foot unit is attached with a silica gel film.

[0017] The first, second and third anti-skid sleeves are all made of soft plastic, and the outer diameters of the first, second and third anti-skid sleeves are all smaller than the outer diameter of the first bearing.

[0018] The beneficial effects of the present application are:

[0019] 1. The foot unit of the present application adopts the design of double-layer circular arc feet, and the design that the inner side of the foot bottom is higher than the outer side of the foot bottom increases the collision buffering time and improves the stability of the robot walking, and at the same time, the energy loss caused by sliding friction is avoided, so that the gravitational potential energy is efficiently converted into kinetic energy.

[0020] 2. The design of the hip joint bearing assembly in the present application reduces friction and energy consumption, realizes the maximum utilization of gravitational potential energy in the process of robot walking, and further improves the operation efficiency of the device.

[0021] 3. The optimal curvature design of the double-layer circular arc feet in the present application can effectively raise the center of mass when the feet roll, and increase the kinetic balance of walking.

[0022] 4. The bottom of the foot unit of the present application is attached with a silica gel film, which can increase the friction force of the contact surface and avoid unstable gait conversion caused by sliding of the supporting legs.

[0023] 5. The symmetrical design of each leg and the torso in the present application makes the center of mass of the torso accurately located at the center, and the flexibility of the center of mass adjustment further optimizes the gait stability.

[0024] 6. The height of the hip joint in the present application is adjustable, so that the robot can adapt to different slope conditions. The user can also study the influence of different heights on gait by adjusting the position of the hip joint, which provides experimental basis for further optimization design.

[0025] 7. Regardless of the initial release state (such as posture, orientation, etc.), the robot can adjust its gait within several cycles to eventually reach a stable motion state. The stride length, cycle, and average speed tend to be consistent in the stable motion state, demonstrating the adaptability of the design.

[0026] 8. The anti-slip sleeve and bearing combination design at the hip joint of this invention facilitates disassembly and assembly, simplifies the maintenance process, and reduces the cost of use and maintenance.

[0027] 9. This invention adopts a simple mechanical structure, without motors and controllers, which makes the structure simple, the manufacturing cost low, reduces the complexity of the equipment, and is suitable for large-scale promotion.

[0028] 10. The innovative design of the double-layered arc foot of this invention solves the problem that traditional passive walking devices cannot walk continuously, and realizes stable and long-term periodic walking.

[0029] 11. The connection structure between each leg and the torso in this invention ensures that the maximum swing angle of each leg remains consistent, resulting in a more regular gait and further improving the continuity and aesthetics of walking.

[0030] 12. This invention is driven entirely by gravitational potential energy, avoiding the resource waste and pollution caused by traditional robots relying on electricity or fuel.

[0031] 13. The passive walking method of this invention achieves ultra-high energy efficiency, comparable to the energy consumption of human walking, and is a deep biomimetic application of natural dynamics. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention. Figure One .

[0033] Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention. Figure Two .

[0034] Figure 3 This is a schematic diagram of the structure of the torso of the present invention.

[0035] Figure 4 This is a schematic diagram of the structure of the left foreleg of the present invention.

[0036] Figure 5 This is a schematic diagram of the center of the inner and outer arc surfaces of the foot unit of the present invention.

[0037] Figure 6 This is a schematic diagram of the structure of the left connecting component on the first joint axis of the present invention.

[0038] Figure 7 yes Figure 6 Enlarged view of part A.

[0039] Figure 8 This is a schematic diagram of the maximum swing angle of the present invention.

[0040] Figure 9 This is an exploded view of the left constraint rod connection of the present invention.

[0041] Figure 10 This is a schematic diagram of the walking process of the present invention. Figure One .

[0042] Figure 11 This is a schematic diagram of the walking process of the present invention. Figure Two .

[0043] The labels in the above figures are as follows: torso 1, through hole 11, left foreleg 2, leg unit 21, first rod 211, second rod 212, first connecting hole 213, second connecting hole 214, foot unit 22, inner arc surface 221, outer arc surface 222, right foreleg 3, left hind leg 4, right hind leg 5, left constraint rod 6, connecting rod 61, fixing cap 62, right constraint rod 7, first joint axis 8, first anti-slip sleeve 81, first bearing 82, second anti-slip sleeve 83, third anti-slip sleeve 84, second joint axis 9. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings:

[0045] like Figure 1 , Figure 2 The illustrated quadrupedal passive walking robot includes a square torso 1 and a left front leg 2, a right front leg 3, a left hind leg 4, and a right hind leg 5 rotatably connected to the four corners of the torso 1. The left front leg 2 and right front leg 3, and the left hind leg 4 and right hind leg 5 are symmetrically arranged along the vertical midline of the torso 1, and the left front leg 2 and left hind leg 4, and the right front leg 3 and right hind leg 5 are symmetrically arranged along the horizontal midline of the torso 1.

[0046] The left foreleg 2, right foreleg 3, left hind leg 4, and right hind leg 5 have the same structure, each including a leg unit 21 and a foot unit 22. The leg unit 21 is rotatably connected to the torso 1 to form a hip joint, and the foot unit 22 is fixedly connected to the leg unit 21.

[0047] Furthermore, such as Figure 3 As shown, the center of mass of the torso 1 coincides with the center of the torso 1. In this embodiment, the symmetrical arrangement of the left foreleg 2, right foreleg 3, left hind leg 4, and right hind leg 5 on the torso 1 ensures that the center of mass of the torso is precisely located in the center. Simultaneously, in this embodiment, a through hole 11 is provided at the center of the torso 1. Changing the size of the through hole 11 can change the mass of the torso 1, thereby changing the height of the center of mass and thus affecting the gait. In other words, the center of mass can be flexibly adjusted by changing the size of the through hole 11, further optimizing gait stability.

[0048] Further, the trunk 1 is provided with right-angled notches at four corners for connecting the leg units 21 and limiting the forward and backward swing angles of the leg units 21. Specifically, the leg units 21 in the left front leg 2, the right front leg 3, the left rear leg 4 and the right rear leg 5 are symmetrically connected to the four right-angled notches at the four corners of the trunk 1, and the swing positions of the leg units 21 are limited by the right-angled notches. As shown in Figure 8 the figure, when the leg units 21 swing forward or backward to the positions of collision with the trunk 1, the included angle θ between the axis of the leg units 21 and the collision surface of the trunk 1 is the maximum swing angle. The symmetric design in the embodiment makes the maximum swing angles θ of the leg units 21 in forward and backward movements the same, both being 15°-35°, and makes the walking periodic.

[0049] Further, as shown in Figure 4 the figure, the bottom surface of the foot unit 22 is a stepped arc surface composed of the inner arc surface 221 and the outer arc surface 222, and the inner arc surface 221 is lower than the outer arc surface 222. As shown in Figure 5 the figure, the center M of the inner arc surface 221 and the center N of the outer arc surface 222 are located on the central axis of the leg unit 21, and the curvatures of the inner arc surface 221 and the outer arc surface 222 are equal, which should be greater than the distance from the lowest point of the inner arc surface 221 to the hip joint. The equal curvatures can ensure the smooth switching of the contact points when the inner and outer feet roll, and the rolling of the feet along the slope is synchronous when the inner and outer feet contact the slope at the same time, thereby ensuring the walking balance of the robot. In the embodiment, the high-low arc design of the bottom of the foot unit 22 can make the inner arc surface 221 collide with the slope earlier than the outer arc surface 222, and the time difference of the collision is the buffer time, which can ensure the complete swing of each leg and improve the stability of walking, and avoid the energy loss caused by sliding friction, so that the gravitational potential energy is efficiently converted into kinetic energy. Meanwhile, the curvature in the embodiment is obtained by theoretical calculation, and only when the curvature is greater than the distance from the lowest point of the inner arc surface 221 to the hip joint, the robot can realize passive walking. The optimal curvature can effectively raise the center of mass when the foot unit 22 rolls, convert the gravitational potential energy into kinetic energy of lateral sway, and thereby realize sustained walking.

[0050] More preferably, a silica gel film is pasted on the bottom surface of the foot unit 22, which can increase the friction and make the foot unit 22 roll without relative sliding when contacting the slope. The advantages are: first, the energy loss caused by sliding friction is avoided, the gravitational potential energy is more effectively utilized, and thereby high-efficiency and sustained walking is realized. Second, the situation that the foot unit 22 slides and rolls at the same time during gait conversion is avoided, and the stability of walking is improved.

[0051] Further, the left constraint rod 6 is arranged between the leg unit 21 of the left front leg 2 and the left rear leg 4 and is rotationally connected with the two, and the right constraint rod 7 is arranged between the leg unit 21 of the right front leg 3 and the right rear leg 5 and is rotationally connected with the two. The left constraint rod 6 and the right constraint rod 7 are used to synchronize the movement of the front leg and the rear leg, increase the stability of walking, and make the periodicity of the gait more obvious. Taking the left constraint rod 6 as an example, if the left constraint rod 6 is not arranged, the slight difference in the slope will cause the movement of the left front leg and the left rear leg to be not synchronized, and the time of contacting the slope and the swing in the air will be different, resulting in the difference in the swing angle. This difference will continue to enlarge with the increase of the walking period, and finally the robot will be "stuck" on the slope and cannot walk, that is, the sustainable walking cannot be realized.

[0052] Further, the leg unit 21 includes a first rod body 211 with a square cross section and a second rod body 212 with a circular cross section, and the first rod body 211 is provided with a first connecting hole 213 and a second connecting hole 214 from top to bottom. The first connecting hole 213 is connected with the corresponding left constraint rod 6 or right constraint rod 7. As shown in the figure, specifically, the left constraint rod 6 and the right constraint rod 7 are respectively provided with a connecting rod 61 connected with the leg unit 21, and the connecting rod 61 is connected with the leg unit 21 through a fixing cap 62, that is, the connecting rod 61 penetrates into the first connecting hole 213 and is fixed through the fixing cap 62. Figure 9

[0053] Further, the left front leg 2 and the right front leg 3 are connected through a first joint shaft 8, and the left rear leg 4 and the right rear leg 5 are connected through a second joint shaft 9. The first joint shaft 8 and the second joint shaft 9 are both parallel to the horizontal center line of the torso 1, and both penetrate through the torso 1, that is, the second connecting hole 214 on the leg unit 21 is connected with the corresponding first joint shaft 8 or second joint shaft 9 to form a hip joint.

[0054] Next, the connection mode of the left front leg 2, the right front leg 3 and the first joint shaft 8 will be described, and the connection mode of the left rear leg 4, the right rear leg 5 and the second joint shaft 9 is the same, which will not be described here.

[0055] As shown in the figure, the first joint shaft 8 is provided with a first joint hole 81, and the second joint shaft 9 is provided with a second joint hole 91. The first joint hole 81 and the second joint hole 91 are arranged on the same horizontal line, and the first joint hole 81 and the second joint hole 91 are arranged on the same vertical line. Figure 6 , Figure 7 ​As shown, specifically, the left front leg 2 and the right front leg 3 are connected with the first joint shaft 8 through a left connecting assembly and a right connecting assembly respectively, the left connecting assembly and the right connecting assembly are symmetrically arranged and each includes a first anti-skid sleeve 81, a first bearing 82 and a second anti-skid sleeve 83 arranged on the first joint shaft 8 in sequence, and the first anti-skid sleeve 81 and the second anti-skid sleeve 83 are in close fit with the first joint shaft 8. Preferably, two groups of the first bearing 82 are arranged in the embodiment, and the two groups of the first bearing 82 are positioned through a third anti-skid sleeve 84, and the third anti-skid sleeve 84 is in close fit with the first joint shaft 8. That is, the left connecting assembly and the right connecting assembly each include the first anti-skid sleeve 81, the first bearing 82, the third anti-skid sleeve 84, the first bearing 82 and the second anti-skid sleeve 83 which are sequentially sleeved on the first joint shaft 8. This structure is convenient for disassembly and assembly, and reduces the energy loss caused by friction at the joint, so that the gravitational potential energy can be more effectively utilized.

[0056] The first anti-skid sleeve 81 in the left connecting assembly and the right connecting assembly cooperates to limit the axial movement of the first joint shaft 8, that is, the first anti-skid sleeve 81 in the left connecting assembly and the right connecting assembly is tightly attached to the end surface of the torso 1 when installed, so as to limit the axial displacement of the first joint shaft 8. The second anti-skid sleeve 83 cooperates with the first anti-skid sleeve 81 to limit the axial movement of the first bearing 82, that is, two groups of the first bearing 82 are arranged between the second anti-skid sleeve 83 and the first anti-skid sleeve 81, and the two groups of the first bearing 82 are further separated by the third anti-skid sleeve 84. When assembled, the first joint shaft 8 is first inserted through the through hole arranged on the torso 1, and then the left connecting assembly and the right connecting assembly are sequentially inserted onto the first joint shaft 8, the two first anti-skid sleeves 81 limit the axial displacement of the first joint shaft 8, the third anti-skid sleeve 84 separates the two groups of the first bearing 82, and the two second anti-skid sleeves 83 limit the axial displacement of the first bearing 82. Then the leg unit 21 in the left front leg 2 and the right front leg 3 is assembled to the first bearing 82, that is, the second connecting hole 222 on the leg unit 21 is connected with the first joint shaft 8 through the two groups of the first bearing 82. The outer diameters of the first anti-skid sleeve 81, the second anti-skid sleeve 83 and the third anti-skid sleeve 84 in the embodiment are all smaller than the outer diameter of the first bearing 82, so the anti-skid sleeves will not contact the leg unit 21, reducing friction. Preferably, multiple groups of the second connecting hole 214 are equidistantly arranged in the embodiment, so that the height of the hip joint can be adjusted, facilitating the user to study and observe the influence of different hip joint heights on the final walking gait.

[0057] Further, in the embodiment, the first anti-skid sleeve 81, the second anti-skid sleeve 83 and the third anti-skid sleeve 84 are all made of soft plastic, and all the other components are 3D printed except the anti-skid sleeves and the bearings.

[0058] The walking process of the present application will be described in detail in combination with the present embodiment. For the convenience of description, the inner side arc surface 221 and the outer side arc surface 222 of the bottom of the foot unit 22 are defined as the inner side foot and the outer side foot, respectively.

[0059] One complete walking movement cycle of the robot can be divided into three movement stages, i.e., lateral tilting, forward swinging and lateral returning. The lateral tilting stage is the movement stage in which the inner side foot of the supporting leg contacts the ground and tilts laterally until the outer side foot of the supporting leg contacts the ground. The forward swinging stage is the movement stage in which the swing leg on the opposite side swings forward around the hip joint to the maximum swing angle. The lateral returning is the movement stage in which the outer side foot of the supporting leg leaves the slope and the torso returns to the parallel slope. The three movement stages are continuously performed to realize the periodic walking of the robot on the slope.

[0060] 1. Lateral tilting stage.

[0061] Specifically, in the initial state, the inner side feet of the left front leg and the left rear leg of the robot are in a stable contact with the ground, and the right front leg and the right rear leg on the other side are in a suspended state. At this time, the left front leg and the left rear leg are the supporting legs, and the right front leg and the right rear leg are the swing legs. Under the driving of the potential energy, the robot tilts laterally around the contact point of the inner side foot of the supporting leg, and gradually forms lateral rotation and forward pure rolling. As shown in FIG. 2, the lateral rotation process is as follows: starting when the inner side feet of the left front leg and the left rear leg contact the slope, tilting to the left until the outer side feet of the left front leg and the left rear leg contact the slope, the speed is reduced to zero, under the action of the gravity moment, tilting to the right, and returning to the state that both feet contact the slope, and then under the action of the inertia moment, continuing to tilt to the right, the left front leg and the left rear leg are separated from the slope, and tilting to the right until the outer side feet of the right front leg and the right rear leg contact the slope, the speed is reduced to zero, under the action of the gravity moment, tilting to the left, and first returning to the state that both feet contact the slope, and then under the action of the inertia moment, continuing to tilt to the left until the inner side feet of the front leg and the left rear leg contact the slope, and then reciprocating periodically. As shown in FIG. 3, the process of pure rolling is as follows: the robot moves from state (1) to state (3), and the contact points of the left front leg and the left rear leg with the slope change from the rear side of the foot to the front side of the foot in sequence. Due to the great friction, the contact points do not slide relative to the slope, and the speed of the contact points is zero. The left front leg and the left rear leg of the robot perform pure rolling. At the end of the lateral tilting process, the outer side foot of the supporting leg contacts the ground, and the horizontal transfer of the center of gravity is completed. Figure 10 Figure 11 2. Forward swinging stage.

[0062] 2. Forward swinging stage.

[0063] ​After the lateral tilting ends, the swing leg (i.e. the right front leg and the right rear leg) swings forward around the hip joint under the action of inertia and gravity, and the swing angle of the swing leg gradually increases until it reaches the maximum swing angle. During this process, the swing leg is constrained by the straight-angle gap of the torso, so that the motion trajectory is consistent and regular, and the motion of the swing leg is free swinging without external intervention.

[0064] 3. Lateral swing-back stage.

[0065] When the swing leg reaches the maximum swing angle, the lateral foot of the support leg gradually loses the supporting point effect and leaves the ground. Under the action of gravity, the overall center of gravity of the robot moves back to the normal state, and gradually recovers to the state where the torso is parallel to the slope. After the torso is balanced, the medial foot of the swing leg begins to contact the ground to form the support leg of the next cycle.

[0066] The above three stages are repeated to form the periodic walking motion of the robot on the slope. Figure 10 、 Figure 11 The walking motion of the robot in one complete cycle is schematically shown from different perspectives.

[0067] The robot also has the feature of gait self-adjustment: no matter what the release method is, the robot will automatically adjust the gait to the stable motion stage within a few steps, that is, the step length, cycle and average speed of the stable motion state under different release methods are the same. The specific analysis is as follows: In the embodiment, the left and right constraint rods make the left front leg and the left rear leg, and the right front leg and the right rear leg move synchronously. Secondly, the connection between the constraint rod and the corresponding leg, and the connection between the joint shaft and the torso are not tightly fitted, and there is a redundant space for movement, and the difference in movement of the two places will not increase with the increase of the movement distance. Therefore, through the above structure, the robot in the embodiment can achieve the purpose of sustainable walking, and the walking gait has the feature of self-adjustment. Different release methods will cause large differences in initial motion parameters, but as the walking distance increases, the robot will reach a stable walking state, and the motion parameters will converge to a set of stable values. The initial conditions of the robot motion are different, that is, the robot is released in different ways, and the step length, cycle and swing time in the final stable walking stage are the same.

[0068] The above-described embodiments are merely preferred embodiments of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope of the claims of the present application.

Claims

1. A quadrupedal passive walking robot, characterized in that: It includes a square torso (1) and a left foreleg (2), a right foreleg (3), a left hind leg (4) and a right hind leg (5) rotatably connected at the four corners of the torso (1). The left foreleg (2) and the right foreleg (3), the left hind leg (4) and the right hind leg (5) are symmetrically arranged along the vertical midline of the torso (1). The left foreleg (2) and the left hind leg (4), the right foreleg (3) and the right hind leg (5) are symmetrically arranged along the horizontal midline of the torso (1). The left foreleg (2), the right foreleg (3), the left hind leg (4) and the right hind leg (5) have the same structure, each including a leg unit (21) and a foot unit (22). The leg unit (21) is rotatably connected to the torso (1) to form a hip joint, and a left constraint rod (6) is provided between the leg units (21) of the left front leg (2) and the left rear leg (4) and is rotatably connected to both of them, and a right constraint rod (7) is provided between the leg units (21) of the right front leg (3) and the right rear leg (5) and is rotatably connected to both of them. The foot unit (22) is fixedly connected to the leg unit (21). The bottom surface of the foot unit (22) is a stepped arc surface composed of an inner arc surface (221) and an outer arc surface (222). The inner arc surface (221) is lower than the outer arc surface (222). The center of the inner arc surface (221) and the center of the outer arc surface (222) are both located on the central axis of the leg unit (21). The radius of curvature of the inner arc surface (221) and the outer arc surface (222) are equal. The radius of curvature is greater than the distance from the lowest point of the inner arc surface (221) to the hip joint.

2. The quadrupedal passive walking robot according to claim 1, characterized in that: The left foreleg (2) and the right foreleg (3) are connected by a first joint axis (8), and the left hind leg (4) and the right hind leg (5) are connected by a second joint axis (9). The first joint axis (8) and the second joint axis (9) are both parallel to the horizontal midline of the torso (1), and both the first joint axis (8) and the second joint axis (9) are set through the torso (1).

3. The quadrupedal passive walking robot according to claim 1, characterized in that: The left front leg (2) and the right front leg (3) are connected to the first joint shaft (8) through the left connecting component and the right connecting component, respectively. The left connecting component and the right connecting component are symmetrically arranged and each includes a first anti-slip sleeve (81), a first bearing (82) and a second anti-slip sleeve (83) arranged sequentially on the first joint shaft (8). The first anti-slip sleeve (81) and the second anti-slip sleeve (83) are tightly fitted with the first joint shaft (8). The first anti-slip sleeve (81) in the left connecting component and the right connecting component cooperate to limit the axial movement of the first joint shaft (8). The second anti-slip sleeve (83) cooperates with the first anti-slip sleeve (81) to limit the axial movement of the first bearing (82).

4. The quadrupedal passive walking robot according to claim 3, characterized in that: The first bearing (82) is provided in two sets, and the two sets of first bearings (82) are positioned by a third anti-slip sleeve (84), and the third anti-slip sleeve (84) is tightly fitted with the first joint shaft (8).

5. The quadrupedal passive walking robot according to claim 1, characterized in that: The torso (1) has right-angle notches at the four corners to connect the leg units (21) and limit the front and rear swing angles of the leg units (21). The maximum swing angles of the leg units (21) moving forward and backward are the same, both being 15° to 35°.

6. The quadrupedal passive walking robot according to claim 1, characterized in that: The torso (1) has a through hole (11) at its center, and the center of mass of the torso (1) coincides with the center of the torso (1).

7. The quadrupedal passive walking robot according to claim 1, characterized in that: The left constraint rod (6) and the right constraint rod (7) are respectively provided with connecting rods (61) that are connected to the leg unit (21). The connecting rods (61) are connected to the leg unit (21) through fixing caps (62).

8. The quadrupedal passive walking robot according to claim 2, characterized in that: The leg unit (21) includes a first rod (211) with a square cross-section and a second rod (212) with a circular cross-section. The first rod (211) is provided with a first connecting hole (213) and a second connecting hole (214) from top to bottom. The first connecting hole (213) is connected to the corresponding left constraint rod (6) or right constraint rod (7), and the second connecting hole (214) is connected to the corresponding first joint axis (8) or second joint axis (9). Multiple sets of second connecting holes (214) are arranged at equal intervals.

9. The quadrupedal passive walking robot according to claim 1, characterized in that: The bottom surface of the foot unit (22) is covered with a silicone film.

10. The quadrupedal passive walking robot according to claim 4, characterized in that: The first anti-slip sleeve (81), the second anti-slip sleeve (83) and the third anti-slip sleeve (84) are all made of soft plastic, and the outer diameters of the first anti-slip sleeve (81), the second anti-slip sleeve (83) and the third anti-slip sleeve (84) are all smaller than the outer diameter of the first bearing (82).

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