A wearable elbow exoskeleton rehabilitation device with variable stiffness

Abstract

This invention relates to the field of upper limb rehabilitation devices, specifically a wearable elbow exoskeleton rehabilitation device with variable stiffness. Addressing the problem that current elbow rehabilitation devices often have only one degree of freedom and are overly flexible, resulting in insufficient mechanical stiffness and low reliability, this invention proposes a mechanical structure for an elbow rehabilitation device with two degrees of freedom and variable stiffness at the elbow flexion / extension degrees of freedom. Utilizing fundamental theories of the human elbow joint and the principle of variable stiffness, a double-flange structure is employed on the variable stiffness structure to achieve variable stiffness while simplifying the mechanical structure. It also provides driving force for elbow flexion and forearm pronation / supination movements. The elbow flexion / extension range is 0°–130°, and the forearm pronation / supination range is -25°–50°, fully meeting the needs of daily elbow joint rehabilitation.

Description

Technical Field

[0001] This invention relates to the field of upper limb rehabilitation devices, and specifically to a wearable elbow joint exoskeleton rehabilitation device based on a flange structure with a variable stiffness mechanism. Background Technology

[0002] Stroke is clinically defined as an acute focal neurological syndrome attributable to vascular injury (infarction, hemorrhage) of the central nervous system. Stroke is the second leading cause of death or disability worldwide.

[0003] In recent years, scholars both domestically and internationally have conducted in-depth research and analysis on the structure and movement of the elbow joint. Based on the characteristics of elbow joint movement, they have developed various elbow joint rehabilitation devices with different features and applications. Since there is relatively little research on rehabilitation devices that only target the elbow joint, upper limb rehabilitation devices that include elbow joint rehabilitation are also included in the research scope.

[0004] Current trends in elbow rehabilitation devices are towards portability, lightweight design, and exoskeleton-like features. However, some research findings only have a single degree of freedom, while others are overly flexible, leading to problems such as insufficient rigidity, low reliability, and high maintenance difficulty. Furthermore, most are non-variable stiffness structures, lacking adaptability during movement.

[0005] Existing research on rehabilitation devices has focused on relatively simple lower limb movement modules, with limited research on upper limb movement modules, and even fewer devices specifically targeting single-joint movements. Therefore, research on rehabilitation devices targeting the elbow joint is of significant importance.

[0006] Currently, most elbow joint rehabilitation devices, both domestically and internationally, are rigid mechanisms, lacking adaptability and safety; furthermore, most elbow joint rehabilitation devices only have one degree of freedom. To address this, this invention proposes a mechanical structure for an elbow joint rehabilitation device with two degrees of freedom and variable stiffness at the elbow flexion / extension degrees of freedom. The combination of these variable stiffness mechanisms allows for variable stiffness in the elbow flexion / extension motion modules, providing a certain degree of shock absorption and cushioning. Summary of the Invention

[0007] In light of the current research background on elbow joint rehabilitation devices, the purpose of this patent is to provide a wearable elbow joint exoskeleton rehabilitation device with variable stiffness. It adopts a variable stiffness mechanism based on flanges and utilizes relevant theoretical knowledge for the design of elbow joint rehabilitation devices: the basic theory of human elbow joints, the principle of variable stiffness, and conforms to the development trend of elbow rehabilitation devices.

[0008] To achieve the above objectives, the technical solution of the present invention is: a wearable elbow joint exoskeleton rehabilitation device with variable stiffness, comprising an upper arm support frame (1), an upper arm support frame end cap (2), a deep groove ball bearing (3), a variable stiffness mechanism (4), a large worm gear shaft (5), a large worm (6), a worm support frame (7), an upper forearm rib plate (8), a forearm rotation fixation device (9), and a forearm rotation device (10). The upper arm support frame (1) is attached to the upper arm of the human body by a strap. The upper arm support frame (1) and the forearm rotation fixation device (9) are connected by the variable stiffness mechanism (4). The forearm rotation fixation device (9) and the forearm rotation device (10) are connected by gear meshing. The variable stiffness mechanism (4) includes a housing 1 (11), a housing 2 (12), a small worm gear shaft (13), a small worm gear rod (14), a worm gear bracket (15), a worm gear support end cap (16), a pulley fixing plate (17), a preload wheel (18), a large support cover (19), a small support cover (20), an input flange (21), an output flange (22), a tension spring (23), a cable (24), and a pulley (25). The variable stiffness mechanism (4) is connected to the housing 1 (11), housing 2 (12), input flange (21), and output flange (22) by screws. The large support cover (19) supports the output shaft, and the small support cover (20) supports the small worm gear rod (13). 4) At the same time, the keyway on the small support cover (20) and the preload wheel (18) jointly positions the small turbine rod (14). The variable stiffness mechanism (4) consists of two coaxial shafts, including an input flange (21) and an output flange (22), which are designed on the output shaft and the input shaft respectively. Several pulleys are installed on the two flanges. The cable (24) is wound on several pulleys (25) to couple the motion from input to output. In order to expand the stiffness adjustment range, a manually adjustable preload wheel (18) and a tension spring (23) are added to both sides of the cable. The contact surface of the two flanges has a thrust cylindrical roller bearing, and the center of the input flange (21) has a protrusion of the positioning bearing. The elbow flexion / extension movement is realized by the variable stiffness device, and the worm gear is driven by the motor to rotate, providing the driving force for the elbow flexion / extension movement. The variable stiffness mechanism is located at the connection between the upper arm support frame and the upper rib plate of the forearm, which increases the range of motion of the elbow joint, which can reach 0°-130°. The combination of variable stiffness mechanisms allows for variable stiffness in the elbow flexion / extension motion module, which can absorb shocks and provide cushioning. This provides a degree of safety and adaptability.

[0009] The forearm rotation device uses gear transmission. The motor drives a small gear to rotate, which in turn drives a ring rack. To accommodate the movement of the ring rack, a slider is added to the rack, allowing it to rotate around a ring track. This forearm rotation device increases the range of motion for forearm pronation / supination, achieving a range of -25° to 50°, fully meeting the needs of daily elbow joint rehabilitation.

[0010] The beneficial effects of this invention are:

[0011] 1. This invention is portable and allows for elbow joint rehabilitation training anytime and anywhere, without being restricted by location;

[0012] 2. This invention, while achieving variable stiffness, increases the forearm pronation / supination motion degree of freedom;

[0013] 3. This device has a relatively simple structure, is lightweight, and can be attached to the user's arm. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0015] Figure 2 This is the front view of the present invention.

[0016] Figure 3 This is a three-dimensional structural diagram of the variable stiffness structure described in this invention.

[0017] Figure 4 This is a front view of the variable stiffness mechanism described in this invention.

[0018] Figure 5 This is a diagram showing the internal structure of the variable stiffness mechanism described in this invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings. The wearable elbow joint exoskeleton rehabilitation device with variable stiffness includes an upper arm support frame (1), an upper arm support frame end cap (2), a deep groove ball bearing (3), a variable stiffness mechanism (4), a large worm gear shaft (5), a large worm (6), a worm support frame (7), an upper forearm rib plate (8), a forearm rotation fixation device (9), and a forearm rotation device (10). The upper arm support frame (1) is attached to the upper arm of the human body by a strap, the upper arm support frame (1) and the forearm rotation fixation device (9) are connected by the variable stiffness mechanism (4), and the forearm rotation fixation device (9) and the forearm rotation device (10) are connected by gear meshing.

[0020] The variable stiffness mechanism (4) uses pulleys (25) and cables (24) to simplify the model of a zero-length basic four-bar linkage and design a variable stiffness mechanism. To make it more practical, the relative relationship of the model is maintained, and the model is arranged in a circular array. Considering the rationality of space allocation, the array number is selected as three. Then, according to the winding method of the cable, three configurations can be realized. Changing the configuration can adjust the stiffness. The specific mechanism that realizes the above theory is as follows: Figure 5As shown, configuration N=3 is used as an example. To ensure strength, the cable (24) wound around several pulleys (25) is made of steel. The variable stiffness mechanism (4) consists of two coaxial shafts, an output shaft and an input shaft. There are two flanges, an input flange (21) and an output flange (22), which are designed on the output shaft and the input shaft, respectively. Several pulleys (25) are mounted on the two flanges. The cable (24) wound around the pulleys (25) is used to couple the motion from input to output. One end of the cable (24) is connected to a tension spring (23) with a stiffness coefficient of k. The other end is wound by a preload wheel (18), which is connected to a small worm gear shaft (13). The small worm gear rod (14) is used to manually adjust the preload of the spring. The small worm gear rod (14) is supported and positioned by two bearings on a support frame connected to the input flange by bolts and nuts. There is a bearing at the center of the contact surface of the two flanges, which serves as a positioning support. The input flange (21) has a locating bearing protrusion at its center. A complete variable stiffness mechanism requires an outer casing, such as... Figure 4 As shown. The outer casing 1 (11), outer casing 2 (12), and input flange (21) are connected by screws and move together. Two bearings are positioned on the back of the mechanism via the geometry of two connecting covers. The large support cover (19) supports the output shaft, and the small support cover (20) supports the small worm gear (14). The keyway on the preload wheel (18) together positions the small worm gear (14). Due to the combination of the variable stiffness mechanism, the elbow flexion / extension motion module has variable stiffness, which can absorb shocks and provide cushioning. It has a certain degree of safety and adaptability.

[0021] The entire elbow flexion / extension structure described above, such as Figure 2 As shown, the view is taken when the posture is 0°, i.e., the forearm is vertically hanging down. In order to make the space allocation more reasonable, the large worm gear shaft (5) is connected to the input shaft of the input flange (21) by screws. The large worm (6) is connected to the motor, which drives the large worm gear and the stiffness variable mechanism (4) to rotate together. The stiffness variable mechanism (4) is connected to the elbow joint lower rib plate by screws through the output shaft. The arrangement of the threaded holes of the forearm upper rib plate (8) and the output shaft is convenient for installation. All the above structures are installed on the worm support frame (7). The forearm upper rib plate (8) and the worm support frame (7) are integrated.

[0022] Due to the unique nature of forearm pronation / supination freedom, a gear transmission method is used in the design of the forearm rotation device. The forearm rotation motor (28) drives the pinion (27) to rotate, and the pinion (27) drives the ring rack (26) to rotate, thereby realizing the forearm pronation and supination freedom. Considering the movement of the ring rack, a slider is added to the rack to rotate around the ring track to achieve the purpose.

[0023] Because only elbow joint movement is involved, and the upper arm only serves a stabilizing function, the length from the center of the elbow joint to the end of the upper arm device is fixed. However, the forearm involves the entire length, and the length from the center of the elbow joint to the end of the forearm device is variable, with an adjustable length mechanism within a range of ±15mm. This design achieves length adjustment by using different bolt hole sets and bolt-nut combinations on the upper and middle rib plates of the forearm. The upper arm of the designed device is connected to the human upper arm via the upper arm rib plate and a strap of a certain thickness, while the forearm is connected to the human wrist via the lower forearm rib plate and a strap of a certain thickness.

Claims

1. A wearable elbow joint exoskeleton rehabilitation device with variable stiffness, comprising an upper arm support frame (1), an upper arm support frame end cap (2), a deep groove ball bearing (3), a variable stiffness mechanism (4), a large worm gear shaft (5), a large worm (6), a worm support frame (7), an upper forearm rib plate (8), a forearm rotation fixation device (9), and a forearm rotation device (10). The upper arm support frame (1) is attached to the upper arm of the human body by a strap. The upper arm support frame (1) and the forearm rotation fixation device (9) are connected by the variable stiffness mechanism (4). The forearm rotation fixation device (9) and the forearm rotation device (10) are connected by gear meshing. The variable stiffness mechanism (4) includes a housing 1 (11), a housing 2 (12), a small worm gear shaft (13), a small worm gear rod (14), a worm gear bracket (15), a worm gear support frame end cap (16), a pulley fixing plate (17), a preload wheel (18), a large support cover (19), a small support cover (20), an input flange (21), an output flange (22), a tension spring (23), a cable (24), and a pulley (25); wherein the housing 1 (11) and the housing 2 (12) are respectively connected to the input flange (21) and the output flange (22) by screws; the large support cover (19) supports the output shaft, and the small support cover (20) is used to support the small worm gear rod (14), while the small support cover (20) is connected to the preload wheel. The keyway of the tension wheel (18) is used to axially position the small turbine rod (14); at the same time, the variable stiffness mechanism (4) consists of two coaxially arranged shafts, in which the input flange (21) and the output flange (22) are respectively installed on the output shaft and the input shaft, and several pulleys (25) are installed on the two flanges. The cable (24) is wound on several pulleys (25) to realize the motion coupling between the input shaft and the output shaft. In order to expand the stiffness adjustment range, a preload wheel (18) and a tension spring (23) that can be manually adjusted are added to both sides of the cable. A thrust cylindrical roller bearing is provided between the contact surfaces of the two flanges, and a protrusion structure for positioning the bearing is provided in the center of the input flange (21).

2. The wearable elbow exoskeleton rehabilitation device with variable rigidity according to claim 1, characterized in that, The forearm rotation fixing device (9) and forearm rotation device (10) are gear transmissions. The forearm rotation motor (28) drives the pinion (27) to rotate, and the pinion (27) drives the ring rack (26) to rotate, thereby realizing the forearm pronation and supination degrees of freedom.

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