Heavy robot leg mechanism with dead point self-locking and mechanical unloading characteristics

Abstract

The application discloses a heavy robot leg mechanism with a dead point self-locking and mechanical unloading characteristic, and the mechanism constructs a multi-link knee joint transmission mechanism driven by a high linear drive assembly for the operation requirements of heavy load bearing and obstacle crossing on complex terrains, and realizes mechanical unloading by using an actuating extreme stroke; when the leg is in a bearing and ground climbing phase, a push rod of the linear drive assembly is retracted inward to the minimum design stroke, the multi-link network is driven to be unfolded to the rear and is staggered and locked into a polygonal bearing truss structure, external vertical loads are borne through the dead point of the mechanism, and the problem of push rod and compression rod instability and lateral bending moment coupling is reduced; when the leg is in a suspension obstacle crossing phase, the push rod of the linear drive assembly is extended outward to make the mechanism get rid of the dead point state, the link network is driven to be folded, and is accommodated in a V-shaped inner recess chamber of the leg. Under the premise of reducing the terminal rotary inertia, the mechanism considers the support of no driving force under high load, and meets the large-angle obstacle crossing requirement of steep slope terrains.

Description

Technical Field

[0001] This invention belongs to the field of core transmission technology for robots, specifically relating to a heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics. Background Technology

[0002] With the rapid evolution of robotics technology, multi-legged robots, with their superior discrete footholds and three-dimensional environmental adaptability, have demonstrated irreplaceable value in fields such as material transport, geological exploration, and disaster relief. However, when applications expand to extreme and harsh conditions, especially when facing heavy loads and climbing unstructured steep slopes at high angles, stringent engineering challenges are posed to the load-bearing limits, power output efficiency, impact resistance, and structural compactness of the multi-legged robot's leg modules (particularly the core knee joint).

[0003] Currently, knee joint drive modules for heavy-duty multi-legged robots typically employ direct drive with rotary motors, or a simple four-bar linkage combined with linear actuators (such as hydraulic cylinders or electric actuators) straddling the thigh and lower leg. In heavy-duty climbing applications, existing joint drive solutions suffer from the following technical limitations: (1) The lack of nonlinear mechanical gain characteristics leads to excessive load on the drive components. Traditional simple four-bar or direct-drive configurations have limited range of transmission angle variation, and the thrust of the linear actuator is basically linearly related to the end output force. When the robot is in a bent-knee load-bearing or starting push-off position, in order to meet the support requirements, it is usually necessary to configure a linear actuator with large thrust and large size. This increases the overall energy consumption and heat dissipation of the system, and also increases the size of the leg module, which can easily interfere with the robot's motion space.

[0004] (2) The lack of a mechanical unloading mechanism during static support makes the core power components susceptible to damage due to bending moment. In the existing direct drive architecture, when the robot walks on unstructured terrain, the ground impact force and lateral load on the feet are usually directly transmitted and converted into radial bending moment applied to the linear actuator push rod. This stress state is the main cause of push rod bending, jamming and dynamic seal failure, which limits the reliability and service life of the robot under high-intensity operation.

[0005] (3) There is a design contradiction between the end-effector rotational inertia and the kinematic space. Existing solutions usually place the drive components at the distal end of the joint or directly connect them to the main force arm, which increases the rotational inertia of the lower leg end, reduces the dynamic response speed when climbing steep slopes, and increases the mechanical recoil force when the foot touches the ground. At the same time, the simplified linkage mechanism is difficult to balance the thrust requirements under heavy loads and the large-angle folding requirements when crossing obstacles, which can easily lead to insufficient knee flexion angle and foot interference with the slope surface.

[0006] In the field of heavy-duty multi-legged robot leg drive technology, existing technologies mainly achieve joint flexion, extension, and load-bearing targets through three paths: direct bridging drive, parallel linkage mechanisms, and distributed mounting actuation. For example, Chinese patent CN102390459B provides a quadrupedal bionic robot with a parallel leg structure featuring a knee joint, which uses a linear actuator to directly bridging the thigh and lower leg knee joints to achieve leg support and walking. Chinese patent CN114506400B develops a bionic legged robot based on a centralized drive four-degree-of-freedom leg structure, which utilizes a parallel linkage mechanism to improve system load-bearing capacity and motion accuracy. Chinese patent application CN102756766A provides a leg drive mechanism for a legged robot, which achieves joint motion output by directly configuring multiple sets of swing hydraulic cylinders on the thigh and lower leg bones. However, each of the aforementioned existing technologies has significant limitations: the direct bridging scheme lacks a nonlinear mechanical unloading mechanism, and the actuator push rod directly bears external loads and lateral bending moments when under load, which can easily lead to instability and failure of the compression rod; the parallel linkage structure has limited workspace when the knee is folded, and the moving parts are prone to protruding outwards, lacking anti-interference storage space, resulting in weak obstacle-crossing ability; the distributed mounted actuator scheme increases the unsprung mass of the leg actuator, resulting in a sharp increase in the moment of inertia and reducing the high-frequency dynamic response capability of the system. At the same time, none of the technical solutions have achieved effective coordination between dead-point self-locking mechanical unloading and large-angle obstacle-crossing space avoidance. In addition, existing heavy-duty leg joints rely on large-size, heavy-duty actuators to meet load-bearing requirements, resulting in a large overall size of the leg module, which limits the robot's mobility and passability in narrow and unstructured complex terrain.

[0007] In summary, existing simple linkage or direct-drive robot knee joint drive mechanisms are insufficient to simultaneously meet the requirements of heavy load support, resistance to lateral bending moments, and high-mobility obstacle crossing. The field needs a novel leg mechanism with a new topological configuration to solve the above-mentioned technical problems. Summary of the Invention

[0008] In view of the above, the present invention provides a heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics, which can reduce the end-effector rotational inertia, while taking into account the support without driving force under high load and the need to overcome obstacles at large angles on steep slopes.

[0009] A heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics includes a thigh base, a lower leg actuator, and a multi-link knee joint mechanism connecting the two. The multi-link knee joint mechanism includes an upper rocker arm, a front link, a lateral coupling rod, a linear drive assembly, and a main drive swing arm. The inner end of the upper rocker arm is hinged to the upper part of the thigh base, the middle section of the upper rocker arm extending outward is hinged to the top of the main drive swing arm, and the outermost end of the upper rocker arm is hinged to the top of the front link. The stationary end of the linear drive assembly is anchored to the inner middle section of the thigh base, and the moving end push rod of the linear drive assembly reciprocating motion is hinged to the middle section of the main drive swing arm and coaxially hinged to the inner end of the lateral coupling rod at the hinge point. The bottom end of the main drive swing arm is connected to the rear node of the top of the lower leg actuator, and the outer end of the lateral coupling rod and the bottom end of the front link are connected to the front node of the top of the lower leg actuator, forming a front and rear dual-point drive.

[0010] Furthermore, the thigh base constitutes the upper main support frame of the entire leg mechanism, with a pre-reserved mounting position at its top for docking with the robot's torso; the lower leg actuator serves as the lower end actuator frame, with a foot component connected to its bottom end; the multi-link knee joint mechanism is fitted between the lower rear side of the thigh base and the upper rear side of the lower leg actuator, acting as a hub connecting the two main bodies; both the thigh base and the lower leg actuator adopt an integral support frame with a self-contained protective shell, and multiple topological weight reduction holes are arrayed on the outer shell surface of both.

[0011] Furthermore, the upper rocker arm is a long strip structure, the front connecting rod is arranged perpendicular to the top of the lower leg actuator, the lateral coupling rod is a short rod, the linear drive assembly includes an electric cylinder and a telescopic push rod driven by the electric cylinder to perform linear reciprocating motion, and the main transmission swing arm is a long rod.

[0012] Furthermore, the hinge nodes of each component in the multi-link knee joint mechanism adopt a U-shaped groove or a fork-shaped nested assembly structure with double ear plates, and bearings and pins are coaxially installed inside the hinge nodes.

[0013] Furthermore, the bottom hinge of the thigh base, the top hinge of the lower leg actuator, both ends of the main drive swing arm, both ends of the front connecting rod, and both ends of the transverse coupling rod are all provided with parallel clamping double ear plates, and both ends of the upper rocker arm are provided with single ear plates; when assembling the nodes, the single ear plates are nested and inserted into the double ear plate slots of the adjacent components to form a double shear or multiple shear bearing configuration.

[0014] Furthermore, the moving end push rod pull ring of the linear drive assembly and one end single ear of the lateral coupling rod are placed together in the open double ear slot in the middle section of the main drive rocker arm, and are coaxially inserted and positioned by a common main pin. This assembly method allows the drive load from the linear drive assembly to be transmitted to the main drive rocker arm and the lateral coupling rod along a single axis without off-center load.

[0015] Furthermore, each hinge node is connected by a through cylindrical pin. At each movable connection part, rolling bearings and end face thrust bearings are arranged coaxially along the axial direction between the outer and inner ear plates of the cylindrical pin and the assembly gap of the outer ear plate, so as to limit the axial movement of each rod under pressure and reduce frictional resistance.

[0016] Furthermore, in the straight-leg load-bearing state, the push rod of the linear drive assembly retracts inward to its minimum design stroke, pulling the main drive swing arm to extend the lower leg actuator downward. In this extreme posture, the multi-link knee joint mechanism, in conjunction with the physical limit of the push rod, forms a dead-point self-locking. The vertical load on the ground is directly transmitted to the thigh base through the linkage skeleton, realizing the mechanical unloading of the linear drive assembly and avoiding the risk of bending instability caused by the push rod being compressed in the extended state. In the knee-bending obstacle-crossing state, the push rod of the linear drive assembly extends outward, the multi-link knee joint mechanism disengages from the dead-point self-locking state, and the upper rocker arm rotates upward around the thigh hinge point. Through the differential constraint of the front link and the lateral coupling rod, the linear displacement of the push rod is amplified, driving the lower leg actuator to fold backward and upward at a large angle.

[0017] Furthermore, both the thigh base and the lower leg actuator have concave clearance cavities on their opposite sides. When the linear drive assembly extends outward to put the leg mechanism in a flexed knee state, the multi-link knee joint mechanism retracts as a whole and is housed within the V-shaped angle envelope formed by the thigh base and the lower leg actuator and the concave clearance cavity. This cavity spatial layout increases the ground clearance of the leg and reduces the risk of external interference of the leg mechanism in unstructured terrain.

[0018] Based on the above technical solution, the present invention has the following beneficial technical effects: 1. Achieving Heavy-Load Support and Instability Resistance Without Driving Force Based on Inverse Kinematics and Truss Locking: This invention employs inverse kinematics logic. When the robot is subjected to heavy loads, the push rod of the linear drive component retracts inward to its minimum design stroke, and the main drive swing rod, lateral coupling rod, and front connecting rod extend backward and lock into a polygonal load-bearing truss. External vertical loads are directly transmitted to the thigh base through this truss structure. At this time, the mechanism enters a "dead-point" self-locking state, achieving pressure support without driving force and avoiding the problem of bending instability when the push rod is extended and subjected to pressure.

[0019] 2. Coaxial assembly and dual shear structure to achieve mechanical unloading of driving load: This invention constructs a power splitting network. At the power convergence node, the moving end of the linear drive component, the middle section of the main transmission swing arm, and the inner end of the transverse coupling rod are coaxially assembled through a common main pin. The connecting rod node adopts a fork-shaped nesting design with U-shaped grooves or double ear plates to form a dual shear bearing configuration. When traveling on complex terrain, the external impact force is absorbed by the connecting rod skeleton, reducing the eccentric bending moment acting on the push rod of the linear drive component, thus achieving mechanical unloading of the driving load.

[0020] 3. Spatial avoidance planning, balancing large-stroke obstacle crossing and envelope protection: This invention balances heavy-load stiffness and obstacle crossing space through geometric design. When the linear drive component extends outward and leaves the dead point, the multi-link network enters the stroke amplification range, converting the push rod displacement of the linear drive component into a folding action of the lower leg actuator backward and upward. The thigh base and the lower leg actuator have avoidance cavities inside. In the knee-bent posture, the multi-link transmission network retracts and is contained within the V-shaped angle envelope formed by the thigh base and the lower leg actuator. This design increases the robot's ground clearance and reduces the risk of external mechanical interference to the core transmission components in complex terrain.

[0021] 4. Top-mounted power and lightweight layout reduce rotational inertia to improve dynamic response: In terms of mass distribution, the present invention arranges the linear drive components and main transmission links in the area close to the thigh base. Both the thigh base and the lower leg actuators adopt a truss-type topology weight reduction section. This spatial configuration reduces the rotational inertia of the lower leg actuator. The reduced end inertia improves the response speed of the leg during climbing and suspended stepping, broadens the response bandwidth of the control algorithm, and reduces the mechanical recoil force on the fuselage system when the foot touches the ground. Attached Figure Description

[0022] Figure 1 This is an overall isometric schematic diagram of the leg mechanism of the present invention under the bearing and pushing phase.

[0023] Figure 2 This is a frontal projection view of the leg mechanism of the present invention in the bearing and pushing phase.

[0024] Figure 3 This is a side view of the leg mechanism of the present invention in the bearing and pushing phase.

[0025] Figure 4 This is a magnified isometric view of the multi-link knee joint mechanism of the present invention under load-bearing and ground-pushing phase.

[0026] Figure 5 This is a side view geometric feature diagram of the multi-link knee joint mechanism of the present invention under load and ground-stepping phase.

[0027] Figure 6This is a magnified isometric view of the multi-link knee joint mechanism of the present invention in a suspended obstacle crossing phase.

[0028] Figure 7 This is a side view of the storage envelope of the multi-link knee joint mechanism of the present invention in the context of a suspended obstacle crossing phase.

[0029] Figure 8 This is a three-dimensional cross-sectional view of the leg mechanism of the present invention along the core transmission shaft under the bearing and pushing phase.

[0030] Figure 9 This is a cross-sectional view of the internal stress section of the leg mechanism of the present invention along the side view plane under the bearing and pushing phase.

[0031] Figure 10 This is a three-dimensional cross-sectional view of the leg mechanism of the present invention during obstacle avoidance in a suspended obstacle crossing phase.

[0032] Figure 11 This is a cross-sectional view of the internal anti-interference section of the leg mechanism of the present invention along the side view plane during the suspended obstacle crossing phase.

[0033] Figure 12 This is an exploded view of the multi-link knee joint mechanism and its coaxial double shear assembly node of the present invention.

[0034] In the diagram: 100—Multi-link knee joint mechanism, 101—Upper rocker arm (the main long suspension rod at the top), 102—Front link (the rightmost vertically downward rod), 103—Lateral coupling rod (a short horizontal bar connected in the middle of the mechanism), 104—Linear drive assembly (including motor cylinder and telescopic push rod), 105—Main drive swing arm (a long rod arranged vertically in the middle), 200—Thigh base (as an absolutely fixed frame), 300—Lower leg actuator (the final output end at the bottom). Detailed Implementation

[0035] To clarify the technical solution, internal kinematic mechanism, and workflow of the leg mechanism of this invention, this embodiment will describe the operation process of the multi-link mechanism under two working conditions: "bearing and pushing off the ground" and "suspended obstacle crossing". This mechanism utilizes the nonlinear mechanical characteristics of the multi-link mechanism to balance large thrust output and large stroke displacement under the same hardware architecture.

[0036] like Figure 1 As shown, the leg mechanism of the present invention presents a three-section modular design in macroscopic appearance, mainly composed of three main units: thigh base 200, lower leg actuator 300, and multi-link knee joint mechanism 100 connecting the two and providing power conversion.

[0037] In terms of overall spatial layout and relative position, the thigh base 200 constitutes the upper main support frame of the entire leg module, with a pre-reserved mounting position at its top for docking with the robot's torso. The lower leg actuator 300 serves as the lower end actuator frame, with its bottom end connected to the foot component. The multi-link knee joint mechanism 100 is fitted between the lower rear side of the thigh base 200 and the upper rear side of the lower leg actuator 300, acting as a hub connecting the two main components. From an external perspective, both the thigh base 200 and the lower leg actuator 300 employ an integral support frame with its own protective shell. To meet the requirement of low rotational inertia, multiple topological weight reduction holes (such as triangular and polygonal cutouts) are arrayed on the outer shell surfaces of both the thigh base 200 and the lower leg actuator 300.

[0038] When the leg mechanism is in such a state Figure 1 When the "bearing and pushing phase" is shown, the longitudinal central axis of the thigh base 200 and the longitudinal central axis of the lower leg actuator 300 are nearly vertically collinear in posture. At this time, the multi-link knee joint mechanism 100 presents a support frame shape that extends outward and backward behind both. This appearance structure ensures that the upper and lower shell frames can form a mechanical bearing channel under load posture, and the outer contour of the multi-link knee joint mechanism 100 maintains a preset safe envelope distance with the outer shell edges of the thigh base 200 and the lower leg actuator 300 to avoid mechanical interference.

[0039] To illustrate the layout and outer envelope features of the leg mechanism of the present invention in lateral space, such as Figure 2 As shown, viewed from a frontal projection perspective, the thigh base 200, the multi-link knee joint mechanism 100, and the lower leg actuator 300 maintain a centrally symmetrical and collinear arrangement in the lateral direction. Specifically, this frontal view shows the space clearance structure at the top of the lower leg actuator 300, where the upper housing of the lower leg actuator 300 has a U-shaped or fork-shaped concave clearance cavity. Under load, the multi-link knee joint mechanism 100 is fitted and retracted into this concave clearance cavity and connects upwards to the bottom end of the thigh base 200.

[0040] This centrally symmetrical layout ensures a uniform distribution of lateral forces under heavy loads, reducing the generation of eccentric torque; simultaneously, it protects the multi-link knee joint mechanism 100 from solid shells on both sides. Figure 2 As can be seen, the overall assembly width of the multi-link knee joint mechanism 100 is limited within the maximum outer contour width of the thigh base 200 and the lower leg actuator 300, and does not protrude to the side. This compact feature improves the robot's lateral passability when navigating narrow passages.

[0041] To illustrate the kinematic posture and force axis of the leg mechanism in the side view plane of the present invention, as follows: Figure 3As shown in the side view projection, the load-bearing axes of the thigh base 200 and the lower leg actuator 300 are vertically collinear, with an angle between them approaching 180 degrees. This upright posture is the working form of the multi-legged robot when dealing with vertical loads (such as standing still or lifting heavy objects). Meanwhile, Figure 3 The rearward envelope feature of the multi-link knee joint mechanism 100 in this state is shown. When the leg is straight and bearing weight, the multi-link knee joint mechanism 100 extends as a whole toward the rear of the thigh base 200 and the lower leg actuator 300, spanning between the upper and lower main bodies.

[0042] The side view also reveals its housing clearance design: the multi-link knee joint mechanism 100 protrudes rearward to provide mechanical support span, and its overall constraint is located near the rearward protective housing extension line between the bottom of the thigh base 200 and the top of the lower leg actuator 300. Play-off clearances are provided between the edge contours of the components to prevent the upper and lower housings from squeezing against each other or mechanically interfering under load.

[0043] To illustrate the internal power flow and transmission principle of a multi-link knee joint mechanism, such as Figure 4 As shown in the view, the multi-link knee joint mechanism 100 includes five transmission components: an upper rocker arm 101, a front link 102, a lateral coupling rod 103, a linear drive assembly 104, and a main drive swing rod 105. In the construction of the kinematic topology network, the thigh base 200 serves as the frame reference system. To achieve mechanical unloading of the drive axis and the end effector, the specific transmission constraints of the multi-link knee joint mechanism 100 are as follows: one end of the upper rocker arm 101 is hinged to the upper part of the thigh base 200; its outwardly extending middle section is hinged to the top of the main drive swing rod 105; its outermost end is hinged to the top of the front link 102; the stationary end of the linear drive assembly 104 is anchored to the inner middle section of the thigh base 200; its reciprocating moving end push rod is hinged to the middle section of the main drive swing rod 105; and at this connection point, one end of the lateral coupling rod 103 is coaxially hinged. The bottom end of the main drive rocker arm 105 is connected to the rear node at the top of the lower leg actuator 300; the other end of the lateral coupling rod 103 and the bottom end of the front connecting rod 102 are connected together to the front node at the top of the lower leg actuator 300.

[0044] Through the multi-link transmission network composed of the aforementioned transmission components, the linear displacement of the linear drive component 104 is transformed into a nonlinear composite trajectory: In the straight leg load-bearing state, when the linear drive component 104 retracts inward to its minimum design stroke, it pulls the middle section of the main drive swing arm 105. Under this pulling force, the bottom end of the main drive swing arm 105, together with the lateral coupling rod 103 and the front connecting rod 102, causes the lower leg actuator 300 to extend downward. In this posture, the force axes of the main drive swing arm 105 and the lower leg actuator 300 are nearly collinear, and the entire network enters a kinematic "dead point" self-locking state. The vertical load from the lower leg actuator 300 is directly transmitted to the thigh base 200 by the link skeleton, achieving rigid support without driving force maintenance. When transitioning from a straight leg to a bent knee position, the linear drive assembly 104 extends outward, breaking the original collinear state of multiple rods. The mechanism enters the stroke amplification range, and the linear drive assembly 104 pushes the main drive rocker arm 105 and the lateral coupling rod 103. Due to the spatial trajectory constraints applied by the upper rocker arm 101 and the front connecting rod 102, the two drive nodes generate differential displacement, converting the linear extension stroke of the push rod into a rotation of the lower leg actuator 300 folding backward and upward around the thigh base 200.

[0045] To illustrate the mechanical axis distribution and anti-interference envelope of the aforementioned multi-link transmission network under load conditions in a side view, Figure 5 The side view projection illustrates the geometric features of this design. When the system is in a straight-leg support posture, the lower half of the main drive swing arm 105, the lateral coupling rod 103, and the front connecting rod 102 extend rearward in the side view projection, intersecting to form a polygonal load-bearing truss. This truss locking feature, combined with the retraction and limiting of the linear drive component, is the physical expression of the "dead-point self-locking" achieved by this mechanism. In this state, the vertical load borne by the foot end of the lower leg actuator 300 is transmitted along the composite connecting rod skeleton to the force fulcrum of the thigh base 200. This geometric array cuts off the recoil torque acting on the linear drive component 104, achieving mechanical unloading. Furthermore, from... Figure 5 It can be seen that the upper rocker arm 101, the main drive swing rod 105 and its lower connecting rod network form a polygonal truss on the side view projection plane.

[0046] To illustrate the spatial envelope characteristics of multi-link transmission networks when performing obstacle-crossing maneuvers, such as Figure 6 As shown, when the system is in the suspended obstacle-crossing phase, the moving end push rod of the linear drive assembly 104 extends outward to its maximum designed stroke. This linear extension action acts on the middle section of the main drive swing rod 105 and the lateral coupling rod 103, breaking the... Figure 5The multiple links are in a collinear dead-point state. Under the action of outward thrust, the upper rocker arm 101 rotates upward (outward) around its top fixed hinge point, while the main drive rocker arm 105 and the lateral coupling rod 103 are pushed away from the thigh base 200. During this pushing process, due to the coordinated displacement of the front connecting rod 102 and the lateral coupling rod 103, the front and rear drive nodes at the top of the lower leg actuator 300 are pulled backward and upward, thereby driving the lower leg actuator 300 to flex and fold around the thigh base 200.

[0047] also, Figure 6 The mechanism's spatial storage characteristics in a bent-knee state were also demonstrated. When the lower leg actuator 300 is retracted, the rearward-extending upper rocker arm 101, front link 102, lateral coupling rod 103, and main drive swing rod 105 fold inward and retract into the V-shaped angle space formed by the thigh base 200 and the lower leg actuator 300. This provides clearance for obstacle crossing while reducing the risk of mechanical interference caused by the outward protrusion of internal links in complex terrain.

[0048] To illustrate the geometric deformation and contraction profile of the system in a flexed knee position on a side view plane, Figure 7 The side view projection shows the geometric characteristics of the variable transmission ratio in this scheme, and... Figure 5 With different dead-point orientations in the common linear arrangement, when the push rod of the linear drive assembly 104 extends outward, the relative angle between the main drive rocker arm 105, the lateral coupling rod 103 and the front connecting rod 102 decreases. Figure 7 This indicates that after the collinearity is broken, the multi-link transmission network is reconstructed from the supporting skeleton into a folded polygon under the side view projection.

[0049] also, Figure 7 The physical boundaries of the mechanism during retraction are defined using a two-dimensional projection. As can be seen from the side view, in the knee-flexed state, an acute-angled V-shaped space is formed between the thigh base 200 and the lower leg actuator 300. Under the outward extension of the linear drive assembly 104, the overall side-view projection contours of the upper rocker arm 101, front connecting rod 102, lateral coupling rod 103, and main drive swing rod 105 converge within the boundary of this V-shaped angle region. This layout increases the ground clearance of the lower leg and improves the system's anti-interference capability in complex terrain.

[0050] To illustrate the topological layout and physical load-bearing capacity of this invention at the physical manufacturing level, Figure 8The internal solid skeleton and static load transfer path are shown through a cross-sectional view. As shown in the area with section lines in the figure, the thigh base 200 and the lower leg actuator 300 employ a truss-type topology weight reduction design along the main force direction. The main cross-section contains triangular and polygonal weight reduction chambers, and the retained solid parts form staggered load-bearing ribs. Combining the linkage force characteristics under load, when the main drive swing arm 105 and the lower leg actuator 300 are at the collinear dead point and bear the load, the internal force converges on the thigh base 200. The linear drive assembly 104 and its top hinge point are located outside the main load-bearing axis, and their sides are wrapped by the outer shell sidewalls of the thigh base 200 and the lower leg actuator 300. This cross-sectional structure shows the mechanical unloading characteristics of the drive force and ground impact. When the robot suffers a lateral physical impact in complex terrain, the outer solid sidewalls absorb the impact force, preventing direct compression of the internal linear drive assembly 104 cylinder and push rod.

[0051] To define the nested envelope relationship and local stress-bearing cross-sectional characteristics between the internal transmission components and the outer load-bearing shell on the side view plane, from Figure 9 In the sectional projection, it can be observed that both the lower end of the thigh base 200 and the upper end of the lower leg actuator 300 have recessed clearance cavities. The sectional view shows that the linear drive assembly 104 is embedded within the contour line of the cavity formed by the solid cross-section (section line area). The reciprocating axis of the linear push rod is protected within the projection range of the outer shell of the thigh base 200 and the lower leg actuator 300. Furthermore, Figure 9 The cross-sectional features show the stress distribution design of the mechanism under load. When the bottom end of the main drive swing rod 105, the front connecting rod 102 and the transverse coupling rod 103 are at the load dead point, they transmit push-pull shear force to the lower leg actuator 300. Figure 9 The display shows that these load-bearing hinge points are anchored inside the lower leg actuator 300 in a load-bearing base area with thickened solid walls. This deep-embedded load-bearing point and thickened base cross-section structure arrangement allows the stress under heavy loads to be absorbed by the internal base of the lower leg, reducing the risk of shell fatigue failure due to local stress concentration.

[0052] In traditional heavy-duty, long-stroke joint designs, when the push rod is extended and the mechanism is folded at a large angle, internal moving parts are prone to mechanical interference with the inner wall of the external load-bearing housing. Figure 10 The boundary of the solid cross-section with the section line can be observed that the pre-set clearance chamber inside the thigh base 200 and the lower leg actuator 300 accommodates the outwardly extending push rod and the linkage group that is displaced.

[0053] To define the envelope boundary between the internal transmission components and the outer load-bearing housing of the system in a knee-flexed posture on the side view plane, Figure 11The sectional projection shows the characteristics of the push rod extending and retracting into space. When the moving end of the linear drive assembly 104 extends outward and drives the lower leg actuator 300 to fold upward, an acute V-shaped angle is formed between the thigh base 200 and the solid skeleton of the lower leg actuator 300.

[0054] To improve the lateral torsional stiffness and stress uniformity of the system under heavy load conditions, such as Figure 12 As shown, the bottom hinge of the thigh base 200, the top hinge of the lower leg actuator 300, and all connecting ends of the multi-link transmission network adopt a double-ear plate assembly structure.

[0055] In terms of geometric features: the main drive rocker arm 105, the front connecting rod 102 and the transverse coupling rod 103 are all provided with parallel clamping double ears at both ends; the upper rocker arm 101 is provided with single ear plates at both ends; when assembling the nodes, the single ear pieces are nested and inserted into the double ear plate slots of the adjacent components to form a double shear or multiple shear bearing configuration.

[0056] Regarding the assembly details of the articulated transmission assembly: along Figure 12 In the coaxial assembly direction shown, each nested hinge node is connected by a through cylindrical pin. At each movable connection part, rolling bearings (or self-lubricating bushings) and end face thrust bearings are arranged coaxially in sequence between the assembly gaps of the outer and inner ear plates and the outer ear plate of the cylindrical pin, in order to limit the axial movement of each rod under pressure and reduce frictional resistance.

[0057] also, Figure 12 The coaxial assembly feature of the power convergence node of the multi-link knee joint mechanism is also demonstrated. At the intersection of the moving end of the linear drive assembly 104, the middle section of the main drive rocker arm 105, and one end of the lateral coupling rod 103, a three-component coaxial hinge assembly is adopted. The push rod pull ring at the moving end of the linear drive assembly 104 and the single ear at one end of the lateral coupling rod 103 are jointly placed in an open double-ear slot in the middle section of the main drive rocker arm 105, and are coaxially interlocked and positioned by a common main pin. This assembly method allows the drive load from the linear drive assembly 104 to be transmitted along a single axis without off-center loading to the main drive rocker arm 105 and the lateral coupling rod 103.

[0058] The above-described solution for the knee joint drive and steep slope climbing operation of the heavy-duty multi-legged robot is merely one application example of the present invention. The technical solutions of the present invention, particularly the dead-point self-locking and mechanical unloading design and topology layout technology involved, can also be applied to other fields, including but not limited to: industrial heavy-duty automated equipment, large-scale engineering machinery, and the design of heavy-duty deployable mechanisms in the aerospace field.

[0059] Therefore, the scope of protection of this invention should not be limited to specific application carriers (such as quadruped or hexapod robots) or specific work objects, but should cover mechanical joint modules and their transmission methods based on the kinematic configuration and nonlinear stroke conversion strategy described in this invention. Any modifications to the equivalent mechanical structure, equivalent transmission chain, or lever arm ratio made using the description and drawings of this invention, or applications in other related heavy-duty and variable transmission ratio technical fields, are included within the patent protection scope of this invention.

Claims

1. A heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics, characterized in that, The device includes a thigh base, a lower leg actuator, and a multi-link knee joint mechanism connecting the two. The multi-link knee joint mechanism includes an upper rocker arm, a front link, a lateral coupling rod, a linear drive assembly, and a main drive swing arm. The inner end of the upper rocker arm is hinged to the upper part of the thigh base, the middle section of the upper rocker arm extending outward is hinged to the top of the main drive swing arm, and the outermost end of the upper rocker arm is hinged to the top of the front link. The stationary end of the linear drive assembly is anchored to the inner middle section of the thigh base. The moving end push rod of the linear drive assembly, which reciprocates, is hinged to the middle section of the main drive swing arm and coaxially hinged to the inner end of the lateral coupling rod at the hinge point. The bottom end of the main drive swing arm is connected to the rear node at the top of the lower leg actuator, and the outer end of the lateral coupling rod and the bottom end of the front link are connected to the front node at the top of the lower leg actuator, forming a front and rear dual-point drive. In the straight-leg load-bearing state, the push rod of the linear drive assembly retracts inward to its minimum design stroke, pulling the main drive swing arm to extend the lower leg actuator downward. In the extreme posture, the multi-link knee joint mechanism, in conjunction with the physical limit of the push rod, forms a dead-point self-locking. The vertical load on the ground is directly transmitted to the thigh base through the linkage skeleton, realizing the mechanical unloading of the linear drive assembly and avoiding the risk of bending instability caused by the push rod being compressed in the extended state. In the knee-bending obstacle-crossing state, the push rod of the linear drive assembly extends outward, the multi-link knee joint mechanism disengages from the dead-point self-locking state, and the upper rocker arm rotates upward around the thigh hinge point. Through the differential constraint of the front link and the lateral coupling rod, the linear displacement of the push rod is amplified, driving the lower leg actuator to fold backward and upward at a large angle.

2. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 1, characterized in that: The thigh base forms the upper main support frame of the entire leg mechanism, with a pre-reserved mounting position at its top for docking with the robot's torso; the lower leg actuator serves as the lower end actuator frame, with a foot component connected to its bottom end; the multi-link knee joint mechanism is fitted between the lower rear side of the thigh base and the upper rear side of the lower leg actuator, acting as a hub connecting the two main bodies; both the thigh base and the lower leg actuator adopt an integral support frame with a self-contained protective shell, and multiple topological weight reduction holes are arrayed on the outer shell surface of both.

3. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 1, characterized in that: The upper rocker arm is a long strip structure, the front connecting rod is arranged perpendicular to the top of the lower leg actuator, the lateral coupling rod is a short rod, the linear drive assembly includes an electric cylinder and a telescopic push rod driven by the electric cylinder to perform linear reciprocating motion, and the main transmission swing arm is a long rod.

4. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 1, characterized in that: In the multi-link knee joint mechanism, the hinge nodes of each component adopt a U-shaped groove or double ear plate fork-shaped nested assembly structure, and bearings and pins are coaxially installed inside the hinge nodes.

5. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 4, characterized in that: Parallel clamping double ear plates are provided at the bottom hinge position of the thigh base, the top hinge position of the lower leg actuator, both ends of the main drive swing arm, both ends of the front connecting rod, and both ends of the transverse coupling rod. Single ear plates are provided at both ends of the upper rocker arm. During node assembly, the single ear plate is nested into the double ear plate slot of the adjacent component to form a double shear or multiple shear bearing configuration.

6. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 4, characterized in that: Each hinge node is connected by a through cylindrical pin. At each movable connection part, rolling bearings and end face thrust bearings are arranged coaxially along the axial direction between the outer and inner ear plates of the cylindrical pin and the assembly gap of the outer ear plate, so as to limit the axial movement of each rod under pressure and reduce frictional resistance.

7. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 1, characterized in that: The moving end push rod pull ring of the linear drive assembly and one end single ear of the lateral coupling rod are placed together in the open double ear slot in the middle section of the main drive rocker arm, and are coaxially inserted and positioned by a common main pin, so that the drive load from the linear drive assembly can be transmitted to the main drive rocker arm and the lateral coupling rod along a single axis without off-center load.

8. The heavy-duty robot leg mechanism with dead-point self-locking and mechanical unloading characteristics according to claim 1, characterized in that: Both the thigh base and the lower leg actuator have concave clearance cavities on their opposite sides. When the linear drive assembly extends outward to put the leg mechanism in a flexed knee position, the multi-link knee joint mechanism retracts as a whole and is housed within the V-shaped angle envelope formed by the thigh base and the lower leg actuator and the concave clearance cavity. This cavity spatial layout increases the ground clearance of the leg and reduces the risk of external interference of the leg mechanism in unstructured terrain.

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