Double-joint knee-foot type passive walking robot and knee joint locking and unlocking method

Abstract

The invention relates to a double-joint knee-foot type passive walking robot and a knee joint locking and unlocking method. The robot comprises an outer leg connecting frame and walking legs. The walking legs comprise outer legs and inner legs, and the two outer legs are connected with the two ends of the outer leg connecting frame respectively; a hip joint shaft is rotationally connected between the two outer legs, and the inner legs are fixedly connected with the hip joint shaft; the walking legs comprise thighs, shanks and feet, and the thighs and the shanks are rotationally connected through knee joints; the shank is fixedly connected with the foot. The robot can simulate the natural walking process of human beings in the passive walking process, the knee joints of the robot can rapidly achieve the locking and unlocking functions, and the foot type passive walking robot with the knee joints can present a human-like natural gait.

Description

Technical Field

[0001] The present invention belongs to the technical field of walking robots, and in particular relates to a double-jointed knee-foot passive walking robot and a knee joint locking and unlocking method. Background Art

[0002] Most existing bipedal robots achieve walking motion through pre-planned movements based on certain balance principles. While capable of performing many complex humanoid movements, their movements are relatively stiff and energy efficiency is low. Addressing the low energy efficiency and unnatural movements of traditional fully automatic control robots has become a key research topic in bipedal robotics. In 1990, McGeer developed an unpowered walker called a straight-legged bipedal passive walking robot and first proposed the concept of passive walking. Passive walking involves the robot continuously walking along a slope at a certain angle, starting from a suitable initial state, without active drive or control. During this process, the robot relies solely on gravity and inertia to compensate for energy lost through friction and collisions, without the need for active control or external energy input. Passive walking also offers significant advantages, such as a natural gait and high energy efficiency.

[0003] Early models of straight-legged bipedal passive walking robots were very simple, consisting of two identical straight legs connected at the hip joint via a smooth hinge. The legs lacked knee joints. Simulation experiments have shown that these robots "scrub the ground" during walking. This is because the straight legs cannot extend or retract, preventing the sole of the swinging leg from crossing the ground during its swing, resulting in contact with the ground and preventing it from continuing to swing forward.

[0004] Therefore, a bipedal passive walking robot with knees is designed, which is closer to the leg structure of humans. During periodic walking, its gait is more natural and stable, close to the human gait, which is of great significance to the research of walking robots. Summary of the Invention

[0005] In response to at least one of the problems in the above-mentioned prior art, the purpose of the present invention is to provide a dual-joint knee-foot passive walking robot and a knee joint locking and unlocking method, which can simulate the natural walking process of humans during passive walking, and its knee joints can quickly realize the locking and unlocking functions, so that the foot-type passive walking robot with knee joints can present a human-like natural gait.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A double-jointed knee-foot passive walking robot, characterized by comprising:

[0008] Outer leg connecting frame;

[0009] The walking legs are provided with an outer leg and an inner leg, the two outer legs are respectively connected to the two ends of the outer leg connecting frame; a hip joint axis is rotatably connected between the two outer legs, and the inner leg is fixedly connected to the hip joint axis;

[0010] The walking leg comprises a thigh, a calf and a foot, wherein the thigh and the calf are rotatably connected via a knee joint; and the calf is fixedly connected to the foot.

[0011] Preferably, a hip joint bearing is provided between the hip joint axis and the outer leg.

[0012] Preferably, the knee joint includes a knee joint shaft and a knee joint bearing, the knee joint shaft is arranged at the bottom end of the thigh, the knee joint bearing is arranged at the top end of the calf, and the knee joint shaft is rotatably connected to the knee joint bearing.

[0013] Preferably, a calf knee pressure plate is provided on the upper part of the calf, the top of the calf knee pressure plate is higher than the knee joint, and the calf knee pressure plate is used to limit the thigh.

[0014] Preferably, it also includes a control module arranged on the outer leg connecting frame, and a thigh knee electromagnet is provided at the lower part of the thigh for attracting and releasing the calf knee pressure plate; the thigh knee electromagnet is connected to the control module.

[0015] Preferably, a proximity switch is provided in the thigh knee electromagnet, and the proximity switch is connected to the control module. The proximity switch is used to determine whether the calf knee pressure plate is close to the thigh knee electromagnet.

[0016] Preferably, the foot is an offset arc foot, the bottom of which is an arc-shaped foot protruding downward, and a sensor capable of sensing its contact with the ground is provided on the foot, and the sensor is connected to the control module.

[0017] Preferably, the sensor is a piezoresistive pressure sensor, which is arranged at the bottom of the foot, and the piezoresistive pressure sensor is connected to the control module; or, the sensor is a barometric pressure sensor, a cavity is provided inside the foot, the sole of the foot can be deformed when under pressure, and the bottom of the foot is covered with a layer of rubber sheet; the barometric pressure sensor and the inflation port for detecting the air pressure in the cavity are arranged at the top of the foot, and the interior of the cavity can be pre-inflated through the inflation port so that there is a set air pressure inside to increase the sensitivity of the foot touching the ground, and the barometric pressure sensor is connected to the control module.

[0018] Preferably, the number of the inner legs is two, and the thighs of the two inner legs and the calves of the two inner legs are connected by a connecting rod.

[0019] A method for locking and unlocking the knee joints of a double-jointed knee-foot passive walking robot is provided based on the above-mentioned double-jointed knee-foot passive walking robot.

[0020] The steps for locking the knee are as follows:

[0021] When the robot walks down the slope, the swinging walking leg is the swinging leg, and the walking leg in contact with the ground is the supporting leg; during the swinging process of the swinging leg, its thigh and calf rotate around the hip joint axis and the knee joint axis respectively at the same time; the calf drives the calf knee pressure plate to rotate around the knee joint axis until the thigh and the calf are in the same straight line, the calf knee pressure plate contacts the thigh knee electromagnet, and triggers the proximity switch in the thigh knee electromagnet, the proximity switch sends a signal to the control module, which is processed by the control module and sends a power-on signal to the thigh knee electromagnet, which is energized to enable the calf knee pressure plate, and the calf knee pressure plate is sucked onto the thigh knee electromagnet to complete the locking of the knee joint of the swinging leg;

[0022] The steps to unlock the knee joint are as follows:

[0023] After the knee joint of the swinging leg is locked, the thigh and calf of the swinging leg are locked together and rotate together around the hip joint axis. When the foot of the swinging leg contacts the ground and generates an impact, the sole of the foot is deformed, thereby changing the air pressure in the cavity inside the foot and triggering the air pressure sensor at the top to send a signal to the control module. After the signal is processed by the control module, the control module sends a power-off signal to the thigh knee electromagnet of the supporting leg and shields the proximity switch of the thigh knee electromagnet of the supporting leg, so that the thigh knee electromagnet of the supporting leg is powered off and loses its magnetism, completing the unlocking of the knee joint of the supporting leg.

[0024] Or: after the knee joint of the swinging leg is locked, the thigh and calf of the swinging leg are locked together and rotate together around the hip joint axis. When the foot of the swinging leg contacts the ground and produces an impact, the piezoresistive pressure sensor on the sole of the foot is triggered, and a signal is sent to the control module. The signal is processed by the control module, and the control module sends a power-off signal to the thigh knee electromagnet of the supporting leg and shields the proximity switch of the thigh knee electromagnet of the supporting leg, so that the thigh knee electromagnet of the supporting leg is powered off and loses its magnetism, thereby completing the unlocking of the knee joint of the supporting leg.

[0025] The present invention has the following advantages due to the adoption of the above technical solution:

[0026] 1. The dual-joint knee-foot passive walking robot and the knee joint locking and unlocking method provided by the present invention can simulate the natural walking process of humans during passive walking. Its knee joint can quickly realize the locking and unlocking functions, so that the foot-type passive walking robot with knee joints can present a human-like natural gait.

[0027] 2. The dual-joint knee-foot passive walking robot and the knee joint locking and unlocking method provided by the present invention, when the robot walks down a slope, the knee joints of the swing leg and the supporting leg are locked and unlocked by controlling the attraction and release of the thigh knee electromagnet and the calf knee pressure plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is an isometric view of the dual-joint knee-foot passive walking robot provided in the first embodiment of the present invention.

[0029] Figure 2 This is a front view of the double-jointed knee-foot passive walking robot provided by this embodiment of the present invention.

[0030] Figure 3 This is the main view A-direction view of the double-jointed knee-foot passive walking robot provided by this embodiment of the present invention.

[0031] Figure 4 This is a front view of a foot of a double-jointed knee-foot passive walking robot provided by this embodiment of the present invention.

[0032] Figure 5 This is a top view of the dual-joint knee-foot passive walking robot provided by this embodiment of the present invention, with the rubber sheet removed.

[0033] Figure 6 This is a front view of another foot of the double-jointed knee-foot passive walking robot provided in this embodiment of the present invention.

[0034] Figure 7 It is a partial cross-sectional view of the knee joint of the double-jointed knee-foot passive walking robot provided by this embodiment of the present invention.

[0035] Figure 8 This is a schematic diagram of the sagittal plane walking process of the dual-joint knee-foot passive walking robot provided by this embodiment of the present invention.

[0036] Markings in the accompanying drawings:

[0037] 100 is the outer leg, 200 is the inner leg, 1 is the control module, 2 is the outer leg connecting frame, 3 is the thigh, 4 is the thigh knee electromagnet, 5 is the calf knee pressure plate, 6 is the calf, 7 is the foot, 8 is the hip joint axis, 9 is the hip joint bearing, 10 is the knee joint axis, 11 is the knee joint bearing, 12 is the air pressure sensor, 13 is the proximity switch, 14 is the connecting rod, 15 is the inflation port, 16 is the rubber sheet, and 17 is the piezoresistive pressure sensor. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "back", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "assembly," "disposition," and "connection" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0041] The present invention provides a dual-joint knee-foot passive walking robot and a knee joint locking and unlocking method, which can simulate the natural walking process of humans during passive walking. The knee joint can quickly realize the locking and unlocking functions, so that the foot-type passive walking robot with knee joints can present a human-like natural gait.

[0042] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0043] Example 1

[0044] Please refer to Figures 1 to 5The present embodiment provides a dual-joint knee-foot passive walking robot, comprising an outer leg connecting frame 2 and walking legs; the walking legs are provided as an outer leg 100 and an inner leg 200, the two outer legs 100 are respectively connected to the two ends of the outer leg connecting frame 2; a hip joint axis 8 is rotatably connected between the two outer legs 100, and the inner leg 200 is fixedly connected to the hip joint axis 8;

[0045] The walking leg includes a thigh 3, a calf 6 and a foot 7. The thigh 3 and the calf 6 are rotatably connected via a knee joint; the calf 6 is fixedly connected to the foot.

[0046] In specific applications, the outer leg 100 and the inner leg 200 of the walking leg have the same structure. The main body of the outer leg connecting frame 2 is a crossbeam with both ends bent downward. The two ends of the outer leg connecting frame 2 are fixedly connected to the two thighs 3 of the outer leg 100 through four bolts respectively. The two thighs 3 of the outer leg 100 are parallel to each other to ensure that the two outer legs 100 move synchronously.

[0047] In this embodiment, a hip joint bearing 9 is provided between the hip joint axis 8 and the outer leg 100 .

[0048] Specifically, the tops of the thighs 3 of the two outer legs 100 are provided with bearing mounting holes, into which the hip joint bearings 9 are mounted. The hip joint bearings 9 can be ball bearings. The ends of the hip joint axis 8 are inserted into the center holes of the hip joint bearings 9, rotatably connected to the hip joint bearings 9. The thighs 3 of the two outer legs 100, the hip joint axis 8, and the hip joint bearings 9 together form a hip joint that can rotate about the hip joint axis 8. The inner leg 200 is positioned midway between the two outer legs 100.

[0049] In this embodiment, the knee joint includes a knee joint shaft 10 and a knee joint bearing 11. The knee joint shaft 10 is arranged at the bottom end of the thigh 3, and the knee joint bearing 11 is arranged at the top end of the calf 6. The knee joint shaft 10 is rotatably connected to the knee joint bearing 11.

[0050] Specifically, a bearing mounting hole is opened at the top of the calf 6, the knee joint bearing 11 is installed in the bearing mounting hole, and one side of the knee joint axis 10 is inserted into the center hole of the knee joint bearing 11, so that the thigh 3 and the calf 6 can rotate around the knee joint axis 10.

[0051] In this embodiment, the robot also includes a control module 1, which is fixedly mounted on the crossbeam of the outer leg connecting frame 2. The control module 1 includes a main control module (model: STM32F103C8T6, which performs logic control and PWM generation); a power supply module (model: LM2596 DC-DC step-down module, which provides a stable voltage for the electromagnet and controller); a drive module (model: HLS8L-DC5V relay module, which controls the on and off of the electromagnet and supports high current); and a protection module (model: freewheeling diode 1N5822, which prevents damage to the circuit due to back electromotive force, overcurrent, and short circuit. Each module in the control module 1 is a prior art product. The controller is connected to the electromagnet 4, the receiving proximity switch 13, and the pneumatic strain gauge 12 or piezoresistive pressure sensor 17. The controller can control the operating state of the thigh knee electromagnet 4 and receive signals transmitted by the proximity switch 13 and the pneumatic strain gauge 12 or piezoresistive pressure sensor 17.

[0052] In this embodiment, a calf knee pressure plate 5 is provided on the upper portion of the calf 6 of each walking leg. The top of the calf knee pressure plate 5 is higher than the knee joint and is used to limit the position of the thigh 3. A thigh knee electromagnet 4 is provided on the lower portion of the thigh 3 to attract and release the calf knee pressure plate 5; the thigh knee electromagnet 4 is connected to the control module 1.

[0053] In specific applications, the thigh knee electromagnet 4 is installed at the lower position of the thigh 3 above the knee joint by four bolts; the calf knee pressure plate 5 is fixed to the upper position of the calf 6 below the knee joint by six bolts. The calf knee pressure plate 5 is made of steel or iron, which can meet the magnetic adsorption of the thigh knee electromagnet 4. The calf knee pressure plate 5 is a rectangular plate with its top higher than the knee joint, simulating the human knee joint, and can limit the thigh 3 to prevent its knee joint from flexing backward.

[0054] In this embodiment, a proximity switch 13 is provided in the thigh knee electromagnet 4 , and the proximity switch 13 is connected to the control module 1 . The proximity switch 13 is used to determine whether the calf knee pressure plate 5 is close to the thigh knee electromagnet 4 .

[0055] Specifically, a threaded hole is opened on the thigh knee electromagnet 4, and the proximity switch 13 is installed and fixed in the threaded hole of the thigh knee electromagnet 4 of the robot through its own threaded structure. When the calf knee pressure plate 5 approaches the thigh knee electromagnet 4, it will send a signal to the control module 1. The proximity switch 13 can adopt existing technology products.

[0056] In this embodiment, the foot 7 is an offset arc foot, and its bottom is a downwardly convex arc shape. A sensor capable of sensing its contact with the ground is provided on the foot 7, and the sensor is connected to the control module 1.

[0057] Specifically, the sensor is a piezoresistive pressure sensor 17, located at the bottom of the foot 7 and connected to the control module 1. Alternatively, the sensor is a pneumatic pressure sensor 12, which has a cavity inside the foot 7. When the foot 7 contacts the ground, the sole of the foot is subjected to pressure and deforms. The bottom of the foot is covered with a wear-resistant and deformable rubber sheet 16. The pneumatic pressure sensor 12, used to detect the air pressure within the cavity, and an inflation port 15 are located at the top of the foot 7. Air can be pre-inflated into the cavity through the inflation port. After inflation, the inflation port 15 is sealed to prevent the air in the cavity from escaping. After inflation, the cavity is filled with air to a certain level of pressure, which increases the sensitivity of the foot 7 to the ground. The pneumatic pressure sensor 12 is connected to the control module 1. The pneumatic pressure sensor 12 is installed on the upper part of the robot's offset arc foot, ensuring that when the foot 7 contacts the ground, the internal air pressure changes, triggering the pneumatic pressure sensor 12 and promptly transmitting a signal to the control module 1.

[0058] In this embodiment, the shank 6 and the offset arc foot 7 are fixed together by bolts. The offset arc foot can improve the robot's terrain adaptability, energy efficiency and movement stability, and is particularly suitable for legged robots that require dynamic movement or operate in complex environments.

[0059] In this embodiment, two inner legs 200 are provided, and the thighs 3 of the two inner legs 200 and the calves 6 of the two inner legs 200 are connected by a connecting rod 14.

[0060] Specifically, the two inner legs 200 can further ensure the stability of the robot when walking, and the synchronization of the two legs when walking can be ensured through the connecting rod 14; similarly, the robot is provided with two outer legs 100 to ensure the stability of the robot when walking.

[0061] Example 2

[0062] Please refer to Figure 6 This embodiment provides a method for locking and unlocking the knee joints of a dual-joint knee-foot passive walking robot, which is based on the dual-joint knee-foot passive walking robot in Example 1.

[0063] The steps for locking the knee are as follows:

[0064] When the robot walks down a slope, for example, the slope has an inclination of 5°, the swinging walking leg is the swinging leg, and the walking leg in contact with the ground is the supporting leg; during the swinging of the swinging leg, its thigh 3 and calf 6 rotate around the hip joint axis 8 and the knee joint axis 10 respectively at the same time; the calf 6 drives the calf knee pressure plate 5 to rotate around the knee joint axis 10 until the thigh 3 and the calf 6 are in the same straight line, the calf knee pressure plate 5 contacts the thigh knee electromagnet 4, and triggers the proximity switch 13 in the thigh knee electromagnet 4, the proximity switch 13 sends a signal to the control module 1, which is processed by the control module 1 and sends a power-on signal to the thigh knee electromagnet 4, the thigh knee electromagnet 4 is energized and enabled, and the calf knee pressure plate 5 is sucked onto the thigh knee electromagnet 4, completing the locking of the knee joint of the swinging leg.

[0065] The steps to unlock the knee joint are as follows:

[0066] After the knee joint of the swinging leg is locked, the thigh 3 and calf 6 of the swinging leg are locked together and rotate together around the hip joint axis 8. When the foot 7 of the swinging leg contacts the ground and produces an impact, the wear-resistant and deformable rubber sheet 16 on the sole of the foot is triggered, causing the sole of the foot to deform, and the gas pressure in the inner cavity of the foot 7 to increase, triggering the air pressure sensor 12. The air pressure sensor 12 sends a signal to the control module 1. The signal is processed by the control module 1, and the control module 1 sends a power-off signal to the thigh knee electromagnet 4 of the supporting leg and shields the proximity switch of the thigh knee electromagnet 4 of the supporting leg, so that the thigh knee electromagnet 4 of the supporting leg is powered off and loses its magnetism, and the calf knee pressure plate 5 is separated from the adsorption of the thigh knee electromagnet 4, completing the unlocking of the knee joint of the supporting leg.

[0067] Or: after the knee joint of the swinging leg is locked, the thigh 3 and calf 6 of the swinging leg are locked together and rotate together around the hip joint axis 8. When the foot 7 of the swinging leg contacts the ground and produces an impact, the piezoresistive pressure sensor 17 on the sole of the foot is triggered. The piezoresistive pressure sensor 17 sends a signal to the control module 1. The signal is processed by the control module 1. The control module 1 sends a power-off signal to the thigh knee electromagnet 4 of the supporting leg and shields the proximity switch of the thigh knee electromagnet 4 of the supporting leg, so that the thigh knee electromagnet 4 of the supporting leg is powered off and loses its magnetism, and the calf knee pressure plate 5 is separated from the adsorption of the thigh knee electromagnet 4, completing the unlocking of the knee joint of the supporting leg.

[0068] Specifically, in the dual-joint knee-foot passive walking robot of this embodiment, when walking down a slope, the locking phase of the knee joint occurs during the swinging of the swinging leg, such as Figure 6(b to d). The thigh 3 and shank 6 of the robot's leg swing rotate around the hip joint and knee joint respectively at the same time. The shank 6 of the swinging leg drives the shank knee pressure plate 5 to rotate around the knee joint until the thigh 3 of the robot's swinging leg and the shank 6 of the robot's swinging leg are in the same straight line. At this time, the shank knee pressure plate 5 of the robot's swinging leg contacts the thigh knee electromagnet 4, triggering the proximity switch 13 in the thigh knee electromagnet 4. The proximity switch 13 sends a signal to the control module 1. After processing by the control module 1, it sends a power-on signal to the thigh knee electromagnet 4 of the swinging leg, so that the thigh knee electromagnet 4 of the swinging leg is energized and enabled, tightly sucking the shank knee pressure plate 5 onto the thigh knee electromagnet 4, so that the knee of the swinging leg of the foot-type passive walking robot is locked. The unlocking stage of the knee of the foot-type passive walking robot occurs at the moment the swinging leg touches the ground, and at this time the knee joint of the supporting leg can be instantly unlocked, such as Figure 6 (d, e, a, b) in the figure. After the robot's swing leg is locked at the knee joint, the thigh 3 and calf 6 of the swing leg are tightly locked together and rotate together around the hip joint. When the foot 7 of the swing leg contacts the ground and generates an impact, the rubber sheet 16 and the sole of the foot are deformed, causing the air pressure inside the foot 7 to change, triggering the air pressure sensor 12 on the top of the foot, and the air pressure sensor 12 sends a signal to the control module 1; or, when the foot 7 of the swing leg contacts the ground and generates an impact, it triggers the piezoresistive pressure sensor 17 on the sole of the foot, and the piezoresistive pressure sensor 17 sends a signal to the control module 1; the signal is processed by the control module 1, and the control module 1 sends a power-off signal to the thigh knee electromagnet 4 of the supporting leg and shields the proximity switch 13 in the thigh knee electromagnet 4 of the supporting leg, so that the thigh knee electromagnet 4 of the supporting leg is powered off and loses its magnetism, and the calf knee pressure plate 5 of the supporting leg is separated from the adsorption of the thigh knee electromagnet 4. At this time, the knee of the supporting leg of the foot-type passive walking robot is unlocked. Driven by gravity and inertia, the dual-jointed knee-leg passive walking robot can simulate the natural walking process of humans while passively walking along a slope. Its knee joints can be locked and unlocked quickly, allowing the knee-jointed foot-leg passive walking robot to present a human-like natural gait.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A double-jointed knee-foot passive walking robot, characterized in that: include: Outer leg connecting frame; The walking legs are provided with an outer leg and an inner leg, the two outer legs are respectively connected to the two ends of the outer leg connecting frame; a hip joint axis is rotatably connected between the two outer legs, and the inner leg is fixedly connected to the hip joint axis; The walking leg comprises a thigh, a calf and a foot, wherein the thigh and the calf are rotatably connected via a knee joint; and the calf is fixedly connected to the foot.

2. The double-jointed knee-foot passive walking robot according to claim 1, characterized in that: A hip joint bearing is provided between the hip joint shaft and the outer leg.

3. The double-jointed knee-foot passive walking robot according to claim 1, characterized in that: The knee joint includes a knee joint shaft and a knee joint bearing. The knee joint shaft is arranged at the bottom end of the thigh, and the knee joint bearing is arranged at the top end of the calf. The knee joint shaft is rotatably connected to the knee joint bearing.

4. The double-jointed knee-foot passive walking robot according to claim 3, characterized in that: A calf knee pressure plate is provided on the upper part of the calf, the top of the calf knee pressure plate is higher than the knee joint, and the calf knee pressure plate is used to limit the thigh.

5. The double-jointed knee-foot passive walking robot according to claim 4, characterized in that: It also includes a control module arranged on the outer leg connecting frame. A thigh knee electromagnet is arranged at the lower part of the thigh for attracting and releasing the calf knee pressure plate; the thigh knee electromagnet is connected to the control module.

6. The double-jointed knee-foot passive walking robot according to claim 5, characterized in that: A proximity switch is provided in the thigh knee electromagnet, and the proximity switch is connected to the control module. The proximity switch is used to determine whether the calf knee pressure plate is close to the thigh knee electromagnet.

7. The double-jointed knee-foot passive walking robot according to claim 6, characterized in that: The foot is an offset arc foot, the bottom of which is an arc-shaped foot that protrudes downwards. A sensor capable of sensing contact with the ground is provided on the foot, and the sensor is connected to the control module.

8. The double-jointed knee-foot passive walking robot according to claim 6, characterized in that: The sensor is a piezoresistive pressure sensor, which is arranged at the bottom of the foot and is connected to the control module; alternatively, the sensor is an air pressure sensor, a cavity is provided inside the foot, the sole of the foot can be deformed when under pressure, and the bottom of the foot is covered with a layer of rubber sheet; the air pressure sensor and the inflation port for detecting the air pressure in the cavity are arranged at the top of the foot, and the interior of the cavity can be pre-inflated through the inflation port so that there is a set air pressure inside to increase the sensitivity of the foot touching the ground, and the air pressure sensor is connected to the control module.

9. The double-jointed knee-foot passive walking robot according to claim 1, characterized in that: The inner legs are provided in two pieces, and the thighs of the two inner legs and the calves of the two inner legs are connected by a connecting rod.

10. A method for locking and unlocking the knee joints of a dual-jointed knee-foot passive walking robot, characterized in that: The double-jointed knee-foot passive walking machine according to claim 8 is completed; The steps for locking the knee are as follows: When the robot walks down the slope, the swinging walking leg is the swinging leg, and the walking leg in contact with the ground is the supporting leg; during the swinging process of the swinging leg, its thigh and calf rotate around the hip joint axis and the knee joint axis respectively at the same time; the calf drives the calf knee pressure plate to rotate around the knee joint axis until the thigh and the calf are in the same straight line, the calf knee pressure plate contacts the thigh knee electromagnet, and triggers the proximity switch in the thigh knee electromagnet, the proximity switch sends a signal to the control module, which is processed by the control module and sends a power-on signal to the thigh knee electromagnet, which is energized to enable the calf knee pressure plate, and the calf knee pressure plate is sucked onto the thigh knee electromagnet to complete the locking of the knee joint of the swinging leg; The steps to unlock the knee joint are as follows: After the knee joint of the swinging leg is locked, the thigh and calf of the swinging leg are locked together and rotate together around the hip joint axis. When the foot of the swinging leg contacts the ground and generates an impact, the sole of the foot is deformed, thereby changing the air pressure in the cavity inside the foot and triggering the air pressure sensor at the top to send a signal to the control module. After the signal is processed by the control module, the control module sends a power-off signal to the thigh knee electromagnet of the supporting leg and shields the proximity switch of the thigh knee electromagnet of the supporting leg, so that the thigh knee electromagnet of the supporting leg is powered off and loses its magnetism, completing the unlocking of the knee joint of the supporting leg. Or: after the knee joint of the swinging leg is locked, the thigh and calf of the swinging leg are locked together and rotate together around the hip joint axis. When the foot of the swinging leg contacts the ground and produces an impact, the piezoresistive pressure sensor on the sole of the foot is triggered, and a signal is sent to the control module. The signal is processed by the control module, and the control module sends a power-off signal to the thigh knee electromagnet of the supporting leg and shields the proximity switch of the thigh knee electromagnet of the supporting leg, so that the thigh knee electromagnet of the supporting leg is powered off and loses its magnetism, thereby completing the unlocking of the knee joint of the supporting leg.

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