A plantar exoskeleton that changes the trajectory of walking center of gravity

Abstract

A plantar exoskeleton for changing the trajectory of the center of gravity during walking belongs to the field of robotics. It includes a base plate, a drive mechanism, a vertical elastic guide mechanism, and a plantar contact plate. The plantar contact plate is arranged above the base plate. Along the length of the foot, two sets of drive mechanisms are arranged at the front and rear parts of the base plate, respectively. The four drive mechanisms are arranged in an array. The left and right parts of the base plate are respectively provided with a set of vertical elastic guide mechanisms. The two sets of vertical elastic guide mechanisms are connected by a rotating shaft. The rotating shaft is rotatably arranged on the surface of the plantar contact plate. The four drive mechanisms work synchronously to realize the rotation of the plantar contact plate relative to the rotating shaft and the vertical movement relative to the base plate. This application can reduce the up and down fluctuation amplitude of the center of gravity of the human body during walking, making the power-assisting position equivalent to the center of gravity, thereby reducing the energy metabolism consumption of the whole body and improving walking efficiency.

Description

Technical Field

[0001] The present invention relates to a foot wearable device, in particular to a plantar exoskeleton for changing the trajectory of the center of gravity during walking, and belongs to the technical field of wearable robots. Background Art

[0002] As people's demands for greater comfort and convenience continue to rise, exoskeletons for assisting walking have garnered widespread attention. Exoskeleton technology research encompasses multiple aspects, with the study of assistive positioning being a key focus. Maintaining a balanced and stable center of gravity during walking is paramount. During a steady gait cycle, the center of gravity fluctuates within the sagittal plane by approximately 5-8 cm. During this period, a significant portion of energy is consumed to balance these fluctuations, with the work required to overcome gravity representing approximately 65% of the total energy consumed.

[0003] Traditional walking-assistance exoskeletons usually assist at the hip, knee, and ankle joints, but few designs consider assisting at the person's overall center of gravity. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and propose a plantar exoskeleton that changes the trajectory of the center of gravity during walking. The plantar exoskeleton can reduce the up and down fluctuation amplitude of the center of gravity during human walking, so that the power assistance position is equivalent to the center of gravity, thereby reducing the energy metabolism consumption of the whole body and improving walking efficiency.

[0005] A plantar exoskeleton for changing the trajectory of the center of gravity during walking comprises a base plate, a driving mechanism, a vertical elastic guide mechanism and a plantar contact plate;

[0006] The plantar contact plate is arranged above the base plate. Along the length direction of the foot, two sets of driving mechanisms are arranged at the front and rear parts of the base plate respectively. The four sets of driving mechanisms are arranged in an array. The left and right parts of the base plate are respectively provided with a set of vertical elastic guide mechanisms. The two sets of vertical elastic guide mechanisms are connected by a rotating shaft. The rotating shaft is rotatably set on the plate surface of the plantar contact plate. The four sets of driving mechanisms work synchronously to realize the rotation of the plantar contact plate relative to the rotating shaft and the vertical movement relative to the base plate.

[0007] Furthermore, each set of the driving mechanism includes a servo, an output rod and a driven rod; the servo is installed on the base plate, the output end of the servo is connected to one end of the output rod, the other end of the output rod is rotatably connected to one end of the driven rod, and the other end of the driven rod is rotatably set on the surface of the sole contact plate.

[0008] Furthermore, each set of the vertical elastic guide mechanism includes a guide shaft, an oil-free bushing and a spring; the lower end of the guide shaft is installed on the base plate, and an oil-free bushing is provided on the guide shaft. The guide shaft can slide on the oil-free bushing, and the two oil-free bushings are connected by a rotating shaft. A spring is sleeved on the guide shaft, and the two ends of the spring are respectively against the oil-free bushing and the base plate.

[0009] The present invention has the following beneficial effects compared with the prior art:

[0010] 1. This application proposes a new type of walking-assisting exoskeleton. The plantar exoskeleton changes the trajectory of the center of gravity to make the assisting position equivalent to the center of gravity of the human body.

[0011] 2. The exoskeleton utilizes active control from parallel servos and passive balancing from high-strength compression springs to precisely control the height of the left and right soles, changing the vertical height of the human center of gravity and reducing center of gravity fluctuations. Simultaneously, the torque actively applied by the servos to the soles of the feet assists walking, reducing energy consumption and improving walking efficiency.

[0012] The present application will be further described below with reference to the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A three-dimensional diagram of a plantar exoskeleton for changing the trajectory of the center of gravity while walking according to the present application;

[0014] Figure 2 It is a schematic diagram of the specific structure of the driving mechanism and the vertical elastic guiding mechanism;

[0015] Figure 3 This is a partial schematic diagram after removing the base plate and servo for this application. DETAILED DESCRIPTION

[0016] The following is a detailed description of the embodiments of the technical solution of the present application in conjunction with the accompanying drawings. Unless otherwise specified, the technical terms or scientific terms used in this application have the common meanings understood by those skilled in the art.

[0017] The study of the power assist position of the exoskeleton robot is one of the key factors affecting balance stability. During walking, in a stable gait cycle, the center of gravity will fluctuate up and down in the sagittal plane. At this time, most of the energy will be consumed to balance the fluctuation of the center of gravity, and a large amount of work is required to overcome gravity.

[0018] In view of this, the present application provides a plantar exoskeleton for changing the trajectory of the center of gravity of walking, referring to Figure 1 , which comprises a base plate 1, a driving mechanism 2, a vertical elastic guide mechanism 3 and a foot contact plate 4;

[0019] The sole contact plate 4 is arranged above the base plate 1. Along the length direction of the foot, two sets of driving mechanisms 2 are respectively arranged at the front and rear parts of the base plate 1. The four sets of driving mechanisms 2 are arranged in an array, for example, two sets of driving mechanisms 2 are arranged in parallel at the front, and two sets of driving mechanisms 2 are arranged in parallel at the rear. A set of vertical elastic guide mechanisms 3 is respectively provided at the left and right parts of the base plate 1. The two sets of vertical elastic guide mechanisms 3 are connected by a rotating shaft 5, and the rotating shaft 5 is rotatably set on the board surface of the sole contact plate 4. The four sets of driving mechanisms 2 work synchronously to realize the rotation of the sole contact plate 4 relative to the rotating shaft 5 and the vertical movement relative to the base plate 1.

[0020] This embodiment adopts the active control of the driving mechanism and the passive balance of the vertical elastic guide mechanism, which can accurately control the height of the left and right soles, change the longitudinal height of the human body's center of gravity, and reduce the fluctuation amplitude of the center of gravity during walking.

[0021] Optionally, refer to Figure 1 and Figure 2 Each set of the driving mechanism 2 includes a steering gear 21, an output rod 22 and a driven rod 23;

[0022] The servo 21 is mounted on the base plate 1. The output end of the servo 21 is connected to one end of an output rod 22. The other end of the output rod 22 is rotatably connected to one end of a driven rod 23. The other end of the driven rod 23 is rotatably mounted on the surface of the sole contact plate 4. Each set of the vertical elastic guide mechanisms 3 includes a guide shaft 31, an oil-free bushing 32, and a spring 33. The lower end of the guide shaft 31 is mounted on the base plate 1. The guide shaft 31 is provided with an oil-free bushing 32, on which the guide shaft 31 can slide. The two oil-free bushings 32 are connected by a rotating shaft 5. The guide shaft 31 is sleeved with a spring 33, and the ends of the spring 33 respectively abut against the oil-free bushing 32 and the base plate 1.

[0023] The four holes 41 are used for fixing straps. After the human body wears the plantar exoskeleton, the feet are fixed by the straps at the holes. The servo will actively adjust the height of the left and right soles according to the gait, thereby reducing the longitudinal fluctuation amplitude of the center of gravity, changing the trajectory of the center of gravity, and providing positive torque to the soles of the feet to assist walking, thereby reducing the energy metabolism consumption of the human body.

[0024] This embodiment designs a bilaterally symmetrical mechanical structure consisting of a five-bar linkage and a guide shaft, achieving two degrees of freedom overall. The output shaft of the servo controls the rotation of the two connecting rods, with two follower rods 23 and the sole contact plate 4 forming the three follower components. This five-bar linkage, combined with the constraints of a fixed ground surface, enables two degrees of freedom of movement and one degree of freedom of rotation for the sole contact plate 4 in the sagittal plane. To achieve this, a longitudinally arranged guide shaft 31 is added. The guide shaft 31 is connected to the sole contact plate 4 via a rotating shaft 5 and a revolving pair (e.g., a bearing 6). The guide shaft 31 is secured to the base plate 1 via a sleeve 34, which is mounted to the sleeve 34, which is in turn mounted to the base plate 1. This design eliminates the degree of freedom of movement along the x-axis. A revolving pair, namely an oil-free bushing 32, is added between the guide shaft 31 and the sole contact plate 4 to ensure longitudinal movement, thereby forming a two-degree-of-freedom device: movement along the z-axis and rotation about the y-axis. The plantar exoskeleton is fixed to the sole of the foot by toothed straps and safety buckles, ensuring comfort while saving time in putting on and taking off.

[0025] The control method for the plantar exoskeleton utilizes a state machine model, converting the device's motion into several discrete states based on the human gait pattern. A distributed IMU is used to detect human posture. Depending on the gait conditions, the motion state of the servo 21 varies. When the IMU detects the sole of the foot is in the stance phase, the pitch angle is zero, the sole is parallel to the ground, and the longitudinal height is at its lowest. When the sole of the foot transitions from the stance phase to the swing phase, the longitudinal height reaches its highest point, and the upper plane of the plantar exoskeleton rotates forward ahead of the sole, providing a positive torque to the sole, thereby reducing energy consumption in the ankle joint and calf muscles. When the sole of the foot is in the swing phase, the pitch angle remains equal to the sole's y-axis motion angle, and the longitudinal height decreases as the swing amplitude of the legs increases. Using this state machine algorithm, the plantar exoskeleton of this embodiment is controlled to change the height of the left and right soles, thereby altering the trajectory of the human center of gravity and reducing the amplitude of center of gravity fluctuation.

[0026] Furthermore, the base plate 1 is made of carbon fiber. The sole contact plate 4 is made of carbon fiber. The guide shaft 31 is also made of carbon fiber. The output rod 22 and the driven rod 23 are made of aluminum alloy, which is lightweight, strong, and has good toughness. Four parallel servos and two high-strength springs are used. The sole exoskeleton made of these materials weighs approximately 0.95 kg per unit, and the entire system, including the electrical system, weighs approximately 2.76 kg (including 0.565 kg of batteries), making it comfortable and convenient to wear.

[0027] Working Principle: Four servos 21 are fixed to the base plate 1. The output rod 22 and the driven rod 23 are assembled together through bearings and rotatably connected to the boss 7 arranged on the sole contact plate 4. The guide shaft 31 and the sleeve 34 are fixed by four screws, and the sleeve 34 is fixed to the base plate 1. The guide shaft 31 can slide freely within the oil-free bushing 32. The two oil-free bushings 32 are fixed together by a rotating shaft 5. The rotating shaft 5 is assembled with the sole contact plate 4 through two bearings 6, allowing the oil-free bushings 32 to rotate freely on both sides of the sole contact plate 4. The spring 33 (such as a compression spring) is fixed between the base plate 1 and the oil-free bushing 32. The upper and lower surfaces are provided with grooves. During walking, the high-strength spring 33 bears most of the force on the sole of the foot. The elastic coefficient can be calculated according to the following formula:

[0028]

[0029] Where n t ——Number of servos, 4 in total;

[0030] l1——the length of the output rod 22;

[0031] α——the angle between the output rod 22 and the ground;

[0032] n k ——Number of springs, 2 in total;

[0033] Δh——Spring compression, unit: mm.

[0034] To meet the needs of users weighing 68-80kg, the selected spring coefficient is 4.25N / mm. The spring is easily removable, so the spring type can be changed according to actual conditions to improve walking comfort.

[0035] This application has been disclosed as above with preferred implementation cases, but it is not intended to limit this application. Any technician familiar with this profession can make slight changes or modifications to the above-disclosed structures and technical contents without departing from the scope of the technical solution of this application, and the equivalent implementation cases with equivalent changes are still within the scope of the technical solution of this application.

Claims

1. A plantar exoskeleton for changing the trajectory of the center of gravity while walking, characterized by: It comprises a base plate (1), a driving mechanism (2), a vertical elastic guide mechanism (3) and a foot contact plate (4); The sole contact plate (4) is arranged above the base plate (1). Two sets of driving mechanisms (2) are arranged at the front and rear parts of the base plate (1) along the length direction of the foot. The four sets of driving mechanisms (2) are arranged in an array. Each set of the driving mechanisms (2) includes a steering gear (21), an output rod (22) and a driven rod (23). The steering gear (21) is installed on the base plate (1). The output end of the steering gear (21) is connected to one end of the output rod (22). The other end of the output rod (22) is rotatably connected to one end of the driven rod (23). The other end of the driven rod (23) is rotatably arranged on the surface of the sole contact plate (4). The left and right parts of the base plate (1) are respectively provided with a set of vertical elastic guide mechanisms. The invention relates to a structure (3), wherein two sets of vertical elastic guide mechanisms (3) are connected via a rotating shaft (5), wherein the rotating shaft (5) is rotatably arranged on the plate surface of the sole contact plate (4), and each set of the vertical elastic guide mechanism (3) comprises a guide shaft (31), an oil-free bushing (32) and a spring (33); the lower end of the guide shaft (31) is mounted on the base plate (1), and the guide shaft (31) is provided with an oil-free bushing (32), and the guide shaft (31) can slide on the oil-free bushing (32), and the two oil-free bushings (32) are connected via the rotating shaft (5), and a spring (33) is sleeved on the guide shaft (31), and the two ends of the spring (33) are respectively against the oil-free bushing (32) and the base plate (1); The four sets of driving mechanisms (2) work synchronously to realize the rotation of the sole contact plate (4) relative to the rotating shaft (5) and the vertical movement relative to the bottom plate (1).

2. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The base plate (1) is made of carbon fiber.

3. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The material of the sole contact plate (4) is carbon fiber.

4. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The output rod (22) and the driven rod (23) are made of aluminum alloy.

5. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The guide shaft (31) is made of carbon fiber.

6. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The spring (33) is a compression spring.

7. The plantar exoskeleton for changing the trajectory of the center of gravity while walking according to claim 1, characterized in that: The guide shaft (31) is mounted on the sleeve (34), and the sleeve (34) is mounted on the base plate (1).

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