A bionic intelligent ankle prosthesis based on complex conjugate curved surface rolling

Abstract

A kind of bionic intelligent foot ankle prosthesis based on complex conjugate surface rolling, including foot sole structure, talus structure is connected on foot sole structure, talus structure is connected with talus rolling joint;Talus structure is connected with ball screw sliding block through achilles tendon structure, ball screw nut is connected on ball screw sliding block, ball screw is installed between screw base and motor screw fixed block, screw base, motor screw fixed block are fixed on tibia structure;Tibia structure bottom is connected with tibia rolling joint, tibia rolling joint is connected with talus rolling joint and rolls, is constrained by parallel spring, both ends of parallel spring are connected on tibia structure and talus structure;Ball screw is driven by motor, motor is fixed on tibia structure;The present application can accurately fit the motion characteristics of human ankle joint, effectively promote lower limb movement mode of foot ankle amputee, so that prosthesis gait is more smooth and natural, with wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of rehabilitation equipment technology, and in particular to a biomimetic intelligent foot and ankle prosthesis based on the rolling of complex conjugate surfaces. Background Technology

[0002] Lower limb amputees suffer both physical and psychological torment, losing not only the ability to live independently but also being highly susceptible to secondary injuries. One effective way to address these problems is to provide lower limb amputees with appropriate prostheses to compensate for their lost motor functions.

[0003] As the only platform for lower limb amputees to contact the ground, foot and ankle prostheses must possess strong adaptability, capable of adapting to irregular terrain while meeting the demands of weight support and propulsion. Existing prosthetic joints mostly employ single rotary joints or linkage mechanisms (Pi Ming, Research on Key Technologies of Intelligent Lower Limb Prosthetic Control, 2021, University of Science and Technology of China, p. 106). Rotary joints cannot accurately replicate the motion characteristics of the human ankle joint, while linkage mechanisms can achieve trajectory fitting to some extent, but the fitting effect deteriorates with increasing trajectory complexity. Therefore, it is necessary to explore a novel prosthetic structure that can fully realize biomimetic functions of the human foot and ankle, while simultaneously developing an intelligent prosthetic control system. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling, which can accurately fit the motion characteristics of the human ankle joint, effectively improve the lower limb movement pattern of ankle amputees, and make the prosthetic gait more smooth and natural, with broad application prospects.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling includes a foot structure 1, a talus structure 2 connected to the foot structure 1, and the talus structure 2 connected to the talus rolling joint 3; the talus structure 2 is connected to one end of the Achilles tendon structure 4, and the other end of the Achilles tendon structure 4 is connected to the ball screw slider 5, a ball screw nut 17 is connected to the ball screw slider 5, a ball screw 16 is installed between the screw base 19 and the motor screw fixing block 7, the screw base 19 and the motor screw fixing block 7 are fixed to the tibia structure 6, a ball screw guide rod 18 is installed between the screw base 19 and the motor screw fixing block 7, and the ball screw slider 5 is guided by the ball screw guide rod 18; the bottom of the tibia structure 6 is connected to the tibia rolling joint 14, the tibia rolling joint 14 is rollingly connected to the talus rolling joint 3 and constrained by a parallel spring 15, the two ends of the parallel spring 15 are connected to the tibia structure 6 and the talus structure 2;

[0007] The ball screw 16 is driven by a motor 10 to drive a drive pulley 24, which in turn is driven by a synchronous belt 23 to drive a driven pulley 22. The driven pulley 22 drives the ball screw 16 to move. The motor 10 is fixed to the tibial structure 6.

[0008] The foot structure 1 is designed based on the shape of the human foot, and its complex curved surface is processed by mold layering. The foot structure 1 is composed of three layers of materials, from bottom to top: bottom rubber foot structure, middle distributed flexible film foot pressure sensor and top carbon fiber foot structure. The three layers are bonded together with flexible adhesive.

[0009] The foot structure 1, made of composite materials, is equivalent to adding an elastomer to the end of the actuator. The elastomer stores the torque applied to the load through a considerable amount of elastic deformation. The elastic strain energy response of carbon fiber foot structures of different thicknesses is different, and its energy storage characteristics vary with its thickness, enabling the foot structure 1 to be used in a variety of applications.

[0010] The groove on the talus rolling joint 3 is fitted with the corresponding boss of the talus structure 2 for lateral positioning, and is connected with bolts and spring washers to ensure reliable connection; the groove on the tibia rolling joint 14 is fitted with the corresponding boss of the tibia structure 6 for lateral positioning, and is connected with bolts and spring washers to ensure reliable connection.

[0011] The talar rolling joint 3 and the tibial rolling joint 14 are connected to a parallel spring 15 via a flexible cross aluminum plate 20. The parallel spring 15 is connected to a fixed pin 21. The flexible cross aluminum plate 20 reduces wear on the talar rolling joint 3 and the tibial rolling joint 14, while reducing the relative friction between the two during movement and ensuring constant contact without slippage, thus improving the accuracy of motion fitting. The parallel spring 15 compensates for the role of flexible connecting tissues in the human body. By symmetrically installing parallel springs 15 on both sides of the talar structure 2 and the tibial structure 6, a suitable contact force is provided to the rolling joint.

[0012] The complex conjugate surface shapes of the talus rolling joint 3 and the tibia rolling joint 14 are based on a set trajectory. The complex conjugate surface is a rolling conjugate trajectory curve obtained by capturing the motion data of the human ankle joint using VICON three-dimensional motion. The conjugate surface is then designed to realize the structural function of the human ankle joint. The original covering conjugate surface of the human ankle joint is improved into a pair of anti-rolling conjugate surfaces, realizing the mixed motion process of sliding and rolling during the original motion. While ensuring the biomimetic nature of the mechanism's motion, the driving complexity of the system is reduced.

[0013] The motor 10 is fixedly inserted into the square hole on the side of the tibial structure 6 by the motor mounting bracket 11 through the second pad 12. The motor mounting bracket 11 and the second pad 12 are fixed by the tapered set screw on the side of the tibial structure 6 to reduce the vibration of the motor 10 during operation. The motor screw fixing block 7 is installed on the tibial structure 6 through the first pad 8. The first pad 8 and the second pad 12 reduce the wear of the tibial structure 6 and extend its service life. The height of the tibial structure 6 can be finely adjusted by replacing the first pad 8 with different models.

[0014] The motor 10 adopts a mode of electromyography (EMG) signal and foot pressure feedback control. The host computer collects and decodes the surface EMG signals of the rectus femoris muscle of the lower limb, selects the corresponding movement mode according to the classification results, converts the movement mode into the corresponding position control command and sends it to the main control module. The prosthesis starts to move under the set target. The encoder 13 feeds back the current movement information of the motor 10, and the distributed flexible film plantar pressure sensor in the foot structure 1 feeds back the plantar pressure information, thereby realizing the closed-loop feedback control of the system.

[0015] The beneficial effects of this invention are:

[0016] This invention extracts typical human ankle joint features, simulates the human foot arch transmission principle based on human biomechanical structure, and uses carbon fiber reinforced resin matrix composite material to make an energy storage foot, realizing energy storage and release during the wearer's walking process, with a high energy release / storage ratio; the properties of carbon fiber material cause the foot to deform to a certain extent during movement, thereby realizing the energy storage and release process, and its heel shock absorption effect makes the wearer's walking dynamic feedback better.

[0017] This invention extracts the motion trajectory of the human ankle joint and, based on this, obtains a talus rolling joint 3 and a tibia rolling joint 14 based on a complex conjugate surface, which can accurately fit the rolling and sliding motion characteristics of the human ankle joint. In addition, based on the human foot contour design, an integrated carbon fiber energy storage foot is obtained, which effectively simulates the energy storage and release process of the human foot. The mechanism has good biomimetic motion function and reduces the energy consumption during the movement of the ankle prosthesis.

[0018] This invention uses a host computer to collect and decode the surface electromyography (EMG) signals of the rectus femoris muscle in the lower limb. Based on the classification results, it selects the corresponding movement mode, converts the movement mode into a corresponding position control command, and sends it to the main control module. The prosthesis begins to move under the set target. The encoder feeds back the current movement information of the motor, and the distributed flexible film plantar pressure sensor in the foot structure feeds back the plantar pressure information, thereby realizing the closed-loop feedback control of the system and improving the natural interaction between the patient and the prosthesis. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall assembly structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the foot structure of the present invention.

[0021] Figure 3 This is a schematic diagram of the talus structure of the present invention.

[0022] Figure 4 This is a schematic diagram of the rolling joint assembly of the present invention.

[0023] Figure 5 This is a schematic diagram of the cross aluminum sheet structure of the present invention.

[0024] Figure 6 This is a schematic diagram of the tibia structure of the present invention.

[0025] Figure 7 This is a schematic diagram of the ball screw slider structure of the present invention.

[0026] Figure 8 This is a schematic diagram of the Achilles tendon structure of the present invention.

[0027] Figure 9 This is a schematic diagram of the motor lead screw fixing plate structure of the present invention.

[0028] Figure 10 This is a schematic diagram of the motor lead screw fixing plate pad structure of the present invention.

[0029] Figure 11 This is a schematic diagram of the motor bracket pad structure of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] Reference Figure 1A biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling includes a foot structure 1, a talus structure 2 connected to the foot structure 1, and the talus structure 2 connected to the talus rolling joint 3; the talus structure 2 is connected to one end of the Achilles tendon structure 4, and the other end of the Achilles tendon structure 4 is connected to a ball screw slider 5; a ball screw nut 17 is connected to the ball screw slider 5; and a ball screw 16 cooperating with the ball screw nut 17 is mounted between a screw base 19 and a motor screw fixing block 7 via bearings. 19 is fixed to the tibial structure 6. The motor screw fixing block 7 is fixed to the tibial structure 6 through the first pad 8. A ball screw guide rod 18 is installed between the screw base 19 and the motor screw fixing block 7. The ball screw slider 5 is guided by the ball screw guide rod 18. The bottom of the tibial structure 6 is connected to the tibial rolling joint 14. The tibial rolling joint 14 is rolledly connected to the talus rolling joint 3 and constrained by the parallel spring 15. The two ends of the parallel spring 15 are connected to the tibial structure 6 and the talus structure 2.

[0032] The ball screw 16 is driven by a motor 10 through a reducer 9 to drive a drive pulley 24. The reducer 9 is fixed to the motor screw fixing block 7 by bolts. The driven pulley 22 is driven by a synchronous belt 23. The driven pulley 22 drives the ball screw 16 to move. The motor 10 is fixed to the tibial structure 6 through a motor fixing bracket 11 and a second pad 12.

[0033] Reference Figure 2 The foot structure 1 is designed based on the shape of the human foot, and its complex curved surface is processed using mold layering. The foot structure 1 is composed of three layers of materials, from bottom to top: a bottom layer of rubber foot structure, a middle layer of distributed flexible film plantar pressure sensors, and an upper layer of carbon fiber foot structure. These three layers are bonded together with flexible adhesive. The foot structure 1 is lightweight, has high specific strength, and outstanding specific modulus; its bending strength is unmatched by ordinary metals. Furthermore, carbon fiber has high machinability, allowing for the fabrication of complex curved surfaces according to design requirements. The distributed flexible film plantar pressure sensors can detect the plantar pressure distribution in real time, and the rubber foot structure effectively protects the sensors, extending their service life. The foot structure 1 has three bolt holes for connection to the talus structure 2.

[0034] The foot structure 1, made of composite materials, gives the ankle prosthesis better impact resistance, higher force fidelity, and lower impedance. It is equivalent to adding an elastomer to the end of the actuator. The shock absorption and cushioning effect of the elastomer can effectively reduce the vibration of the actuator. The elastomer stores the torque applied to the load through a considerable amount of elastic deformation, which can effectively improve the stability of the system. The elastic strain energy response of carbon fiber foot with different thicknesses is different, and its energy storage characteristics vary with its thickness, realizing the diversified application of foot structure 1.

[0035] Reference Figure 3The talus structure 2 is a symmetrical integral structure. To enhance the stability of the structure, the rear end of the talus structure 2 is provided with a first boss structure 25, and the first boss structure 25 is provided with a first threaded hole 26. The first boss structure 25 and the first threaded hole 26 are used for assembly with the talus rolling joint 3. The parallel spring 15 and the talus structure 2 are connected by a fixing pin 21. The rear end of the talus structure 2 is provided with a first assembly hole 28 for the fixing pin 21. The talus structure 2 and the Achilles tendon structure 4 are connected by a fixing pin 21 and a bearing. The rear end of the talus structure 2 is provided with a bearing assembly hole 27 for connecting the Achilles tendon structure 4 and the talus structure 2.

[0036] Reference Figures 4-5 To enhance structural stability, the talus rolling joint 3 and the tibia rolling joint 14 are two identical support blocks, arranged symmetrically vertically, and connected to the talus structure 2 and the tibia structure 6 respectively through the central second threaded hole 29. The complex conjugate surface shape of the talus rolling joint 3 and the tibia rolling joint 14 follows a predetermined trajectory. The connection between the talus rolling joint 3 and the tibia rolling joint 14 is achieved through cross aluminum plates 20. Two sets of cross aluminum plates 20 are arranged symmetrically from left to right, and each set of cross aluminum plates 20 consists of 3 pieces. The connection through the cross aluminum plates 20 provides accurate positioning, ensuring that the two rolling joints always move along the conjugate trajectory without slippage or other abnormal connections. The talus rolling joint 3 and the talus structure 2, and the tibia rolling joint 14 and the tibia structure 6 are separate units, facilitating replacement and assembly, and extending the service life of the foot and ankle prosthesis as much as possible.

[0037] The complex conjugate surfaces of the talar rolling joint 3 and the tibial rolling joint 14 are obtained by using the VICON three-dimensional motion capture of the human ankle joint motion data to obtain the rolling conjugate trajectory curves. The conjugate surfaces are then designed and placed between the talar rolling joint 3 and the tibial rolling joint 14 to realize the structural function of the human ankle joint. The original covering conjugate surface of the human ankle joint is improved into a pair of anti-rolling conjugate surfaces, which can realize the mixed motion process of sliding and rolling in the original motion process. While ensuring the biomimetic nature of the mechanism's motion, the driving complexity of the system is effectively reduced.

[0038] Reference Figure 6To improve the product's compactness, the tibia structure 6 is an integral symmetrical structure. A second boss structure 30 is provided at the bottom of the tibia structure 6. The second boss structure 30 is used to assemble with the groove on the tibial rolling joint 14, enhancing the structural connection stability. The first back mounting hole 32 and the bottom groove 31 of the tibia structure 6 are used to install the lead screw base 19, and the lead screw base 19 is locked in the third threaded hole 40 by a tapered set screw. The motor mounting bracket 11 and the second pad 12 are installed on the second back mounting hole of the tibia structure 6. The motor mounting bracket 11 and the second pad 12 are respectively locked in the fourth threaded hole 37 and the fifth threaded hole 38 by tapered set screws in the hole 33; the top threaded hole 34 of the tibia structure 6 is used to assemble the prosthesis receiving cavity; the shoulder 35 of the tibia structure 6 is used to limit the motor screw fixing block 7 and the first pad 8 to prevent them from moving back and forth during the working process and to ensure the stability of the transmission; the sixth threaded hole 36 is used to fix the motor screw fixing block 7 and the first pad 8; and the fixing pin 21 is installed in the second assembly hole 39.

[0039] Reference Figures 7-8 To conform to the movement characteristics of the foot, the Achilles tendon structure 4, talus structure 2, and ball screw slider 5 are connected by bearings, which reduces friction and increases rotational freedom to ensure the flexibility of the mechanism during movement. The ball screw slider 5 is designed with a third mounting hole 41 for installing the ball screw nut 17 and four seventh threaded holes 42 to ensure the reliability of the connection of the ball screw nut 17. The third mounting hole 41 is used to install bushings, which reduces the relative friction between the ball screw nut 17 and the screw guide rod 18, reduces the replacement frequency of the ball screw slider 5, and improves the transmission reliability.

[0040] Reference Figures 9-11 To improve the smoothness of motion transmission and reduce the replacement frequency of the tibial structure 6, a first pad 8 and a second pad 12 are respectively placed under the motor screw fixing block 7 and the motor fixing bracket 11. At the same time, the first slot 44 of the motor screw fixing block 7 and the second slot 45 on the first pad 8 are embedded in the shoulder 35 of the tibial structure 6, which effectively reduces the loosening and forward and backward displacement caused by the vibration of the motor 10 during the transmission process, and ensures the reliable operation of the transmission mechanism.

[0041] The motor 10 adopts a mode of electromyography (EMG) signal and foot pressure feedback control. The host computer collects and decodes the surface EMG signals of the rectus femoris muscle of the lower limb, selects the corresponding movement mode according to the classification results, converts the movement mode into the corresponding position control command and sends it to the main control module. The prosthesis starts to move under the set target. The encoder 13 feeds back the current movement information of the motor 10, and the distributed flexible film plantar pressure sensor in the foot structure 1 feeds back the plantar pressure information, thereby realizing the closed-loop feedback control of the system.

[0042] The working principle of this invention is as follows:

[0043] The control motor 10 drives the active pulley 24 through the reducer 9, which in turn drives the driven pulley 22 through the synchronous belt 23, thereby controlling the movement of the ball screw 16. This causes the ball screw nut 17 to reciprocate linearly along the ball screw 16. The Achilles tendon structure 4 drives the talus structure 2 to roll along the conjugate surface, thereby realizing the flexion and extension movements of the ankle joint and driving the foot structure 1 to realize dorsiflexion and plantarflexion movements, thus supporting the foot and ankle prosthesis patient to complete daily routine activities.

[0044] The foot and ankle prosthesis control system collects and decodes the surface electromyography signals of the rectus femoris muscle of the lower limb through the host computer. Based on the classification results, the system selects the corresponding movement mode and converts the movement mode into the corresponding position control command, which is then sent to the main control module. The prosthesis begins to move under the set target. The encoder feeds back the current movement information of the motor 10, and the distributed flexible film plantar pressure sensor in the foot structure 1 provides real-time feedback of plantar pressure information, thereby realizing the closed-loop feedback control of the system.

[0045] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the scope of protection of the present invention should be defined by the claims.

Claims

1. A biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling, comprising a foot structure (1), characterized in that: The foot structure (1) is connected to the talus structure (2), which is connected to the talus rolling joint (3); the talus structure (2) is connected to one end of the Achilles tendon structure (4), and the other end of the Achilles tendon structure (4) is connected to the ball screw slider (5). The ball screw slider (5) is connected to the ball screw nut (17). The ball screw (16) is installed between the screw base (19) and the motor screw fixing block (7). The screw base (19) and the motor screw fixing block (7) are fixed to the tibia. On the bone structure (6), a ball screw guide rod (18) is installed between the screw base (19) and the motor screw fixing block (7), and the ball screw slider (5) is guided by the ball screw guide rod (18); the bottom of the tibial structure (6) is connected to the tibial rolling joint (14), the tibial rolling joint (14) is rolledly connected to the talus rolling joint (3), and is constrained by the parallel spring (15), the two ends of the parallel spring (15) are connected to the tibial structure (6) and the talus structure (2); The ball screw (16) is driven by a motor (10) to drive the active pulley (24), and driven by a synchronous belt (23) to drive the driven pulley (22). The driven pulley (22) drives the ball screw (16) to move. The motor (10) is fixed on the tibial structure (6). The complex conjugate surface shape of the talus rolling joint (3) and the tibia rolling joint (14) is a set trajectory. The complex conjugate surface is a rolling conjugate trajectory curve obtained by capturing the motion data of the human ankle joint using VICON three-dimensional motion. Then, the conjugate surface is designed to realize the structural function of the human ankle joint. The original covering conjugate surface of the human ankle joint is improved into a pair of anti-rolling conjugate surfaces to realize the mixed motion of sliding and rolling during the original motion. While ensuring the bionic nature of the mechanism's motion, the driving complexity of the system is reduced. The talus rolling joint (3) and the tibia rolling joint (14) are connected by a flexible cross aluminum plate (20) and a parallel spring (15). The parallel spring (15) is connected to a fixed pin (21). The flexible cross aluminum plate (20) reduces the wear of the talus rolling joint (3) and the tibia rolling joint (14), while reducing the relative friction between the two during movement and ensuring that they are in constant contact without any forward or backward slippage, thus improving the accuracy of motion fitting. The parallel spring (15) compensates for the role of the flexible connecting tissue of the human body. By symmetrically installing parallel springs (15) on both sides of the talus structure (2) and the tibia structure (6), the rolling joint is provided with contact force. The motor (10) is fixedly inserted into the square hole on the side of the tibial structure (6) by the motor mounting bracket (11) through the second pad (12). The motor mounting bracket (11) and the second pad (12) are fixed by the tapered set screw on the side of the tibial structure (6) to reduce the vibration of the motor (10) during operation. The motor screw fixing block (7) is installed on the tibial structure (6) through the first pad (8). The first pad (8) and the second pad (12) reduce the wear of the tibial structure (6) and extend its service life. The height of the tibial structure (6) can be finely adjusted by replacing the first pad (8) of different models.

2. The biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling according to claim 1, characterized in that: The foot structure (1) is designed based on the shape of the human foot, and its complex curved surface is processed by mold layering. The foot structure (1) is composed of three layers of materials, from bottom to top: bottom rubber foot structure, middle distributed flexible film foot pressure sensor and top carbon fiber foot structure. The three layers of materials are bonded together by flexible glue.

3. The biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling according to claim 2, characterized in that: The foot structure (1) made of composite materials is equivalent to adding an elastomer to the end of the actuator. The elastomer stores the torque applied to the load through a considerable amount of elastic deformation. The elastic strain energy response of carbon fiber foot with different thicknesses is different, and its energy storage characteristics vary with its thickness, thus realizing the diversified application of the foot structure (1).

4. The biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling according to claim 1, characterized in that: The groove on the talus rolling joint (3) is fitted with the corresponding boss of the talus structure (2) for lateral positioning and is connected with bolts and spring washers; the groove on the tibia rolling joint (14) is fitted with the corresponding boss of the tibia structure (6) for lateral positioning and is connected with bolts and spring washers.

5. The biomimetic intelligent foot and ankle prosthesis based on complex conjugate surface rolling according to claim 1, characterized in that: The motor (10) adopts the electromyography signal and foot pressure feedback control mode. The upper computer collects the surface electromyography signal of the rectus femoris muscle of the lower limb and decodes it. According to the classification result, the corresponding movement mode is selected and the movement mode is converted into the corresponding position control command and sent to the main control module. The prosthesis starts to move under the set target. The encoder (13) feeds back the current movement information of the motor (10). The distributed flexible film foot pressure sensor in the foot structure (1) feeds back the foot pressure information, thereby realizing the closed-loop feedback control of the system.

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