Electro-hydraulic ankle prosthesis and method of designing the same

Abstract

The application discloses a hydraulic integrated block, an electro-hydraulic ankle prosthesis and a design method thereof, and belongs to the technical field of prostheses and additive manufacturing. When the hydraulic integrated block is in passive plantar flexion and passive dorsiflexion, the oil output by a motor pump directly charges a motor energy storage accumulator, when passive dorsiflexion, a hydraulic cylinder directly charges a gravity recovery accumulator, and when active plantar flexion, the total output of the hydraulic system is the sum of the outputs of the motor pump, the gravity recovery accumulator and the motor energy storage accumulator, realizing the storage, recovery and overall regulation and control of the energy of the prosthesis. The electro-hydraulic ankle prosthesis is designed with spatial arrangement of elements and adopts a B-spline curve guide line flow channel to complete the connection of curved pipelines between elements, thereby reducing the overall space volume of the prosthesis, and the overall weight is effectively reduced through filling of a multi-scale porous structure in an internal non-solid area. The design method optimizes the overall element integration, weight and pressure loss of the prosthesis, guarantees the integration and light weight of the prosthesis, and improves the energy utilization efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of prosthetic technology and additive manufacturing, in particular to an electro-hydraulic ankle prosthesis and a design method thereof. BACKGROUND

[0002] The loss of limbs seriously affects the normal life and work of disabled people. Prostheses are one of the important means for the physically disabled to solve the problem of movement obstacles. Unlike upper limb prostheses, the control of lower limb prostheses involves the problem of human body movement balance. Among the active joints of the human lower limbs, the ankle joint is one of the most important weight-bearing joints of the lower limbs, which can bear 5 times the body weight. In addition, the human walking process mainly relies on the coordinated use of ankle joint muscles and hip joint muscles, especially in the power to push the body forward and upward, 60% of which is generated by the ankle joint. The stability and flexibility of the ankle joint play an extremely important role in human movement and coordination. For below-knee amputees, installing an ankle prosthesis can provide basic movement functions and help amputees regain confidence. With the development of technology, prostheses have developed from passive prostheses to active prostheses. Active ankle prostheses are high-tech products that combine bionics, mechanics, control, materials, and electronics. They generally use electric, hydraulic, or pneumatic methods to provide power.

[0003] However, the current active prostheses have some limitations. Due to volume and weight restrictions, they cannot use oversized driving devices and power sources to complete driving, which limits the endurance and power output of ankle prostheses, making it difficult to meet the needs of ankle joints and use characteristics. On the other hand, for hydraulic prostheses, the volume of the hydraulic integrated valve body is large and the weight is heavy due to the limitations of traditional machining methods. The overall wearing feeling is heavy, and traditional machining methods such as drilling, milling, and boring lead to complex process flow, most of the through holes are straight-line pipelines, transmission medium pressure loss is obvious, and additional plugs and other parts are needed, which poses a risk of oil leakage. SUMMARY

[0004] The purpose of the present application is to provide an electro-hydraulic ankle prosthesis and a design method thereof, which can realize the storage, recovery, and overall regulation of prosthesis energy, and effectively reduce the overall space volume and weight of the prosthesis.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0006] A hydraulic integrated block, comprising: a motor pump, a motor energy storage accumulator, a gravity recovery accumulator, an oil storage accumulator, a hydraulic cylinder, an upper end normally open switch valve, an upper end normally closed switch valve, a lower end normally open switch valve, and a lower end normally closed switch valve.

[0007] The oil inlet of the motor pump is connected with the oil port of the oil storage accumulator, the oil outlet of the motor pump is connected with the oil port of the motor energy storage accumulator, one end of the upper normally closed switch valve and one end of the lower normally closed switch valve respectively; when the working state of the hydraulic system is passive plantar flexion and passive dorsiflexion, the oil output by the motor pump directly charges the motor energy storage accumulator;

[0008] The other end of the upper normally closed switch valve is connected with the oil port of the gravity recovery accumulator, and the oil port of the gravity recovery accumulator is also connected with the upper oil port of the hydraulic cylinder; the other end of the lower normally closed switch valve is connected with the lower oil port of the hydraulic cylinder; when the working state of the hydraulic system is passive dorsiflexion, the hydraulic cylinder directly charges the gravity recovery accumulator;

[0009] The oil port of the oil storage accumulator is also connected with one end of the upper normally open switch valve and one end of the lower normally open switch valve, the other end of the upper normally open switch valve is connected with the lower oil port of the hydraulic cylinder, and the other end of the lower normally open switch valve is connected with the upper oil port of the hydraulic cylinder;

[0010] When the working state of the hydraulic system is active plantar flexion, the motor pump pumps the output oil into the upper end of the hydraulic cylinder through the upper normally closed switch valve, the motor energy storage accumulator releases energy and delivers the stored oil to the upper end of the hydraulic cylinder through the upper normally closed switch valve, and at the same time, the gravity recovery accumulator releases energy and directly delivers the stored oil to the upper end of the hydraulic cylinder.

[0011] An electro-hydraulic ankle prosthesis, comprising: a prosthesis connection adapter, a plurality of liquid pressure sensors and the aforementioned hydraulic integrated block;

[0012] The motor energy storage accumulator, the gravity recovery accumulator and the oil storage accumulator in the hydraulic integrated block are arranged at the top, the top of the prosthesis connection adapter, the bottom of the motor energy storage accumulator, the bottom of the gravity recovery accumulator and the bottom of the oil storage accumulator are located at the topmost end, and the plurality of liquid pressure sensors are arranged in the gap between the prosthesis connection adapter and the motor energy storage accumulator, the gravity recovery accumulator and the oil storage accumulator;

[0013] The hydraulic cylinder in the hydraulic integrated block is installed at the front;

[0014] The upper normally open switch valve, the upper normally closed switch valve, the lower normally open switch valve and the lower normally closed switch valve in the hydraulic integrated block are arranged on the right side, and the outer surface of the right side is stepped; the outer surface of the right rear end is cut inward under the premise of ensuring that the motor completely matches the installation plane, and the right front section is cut inward until it just meets the required volume of the pipeline;

[0015] The hydraulic pump in the hydraulic integrated block is placed in the rear along the height direction;

[0016] The bottom is inwardly tapered from the rear side to the front side, so that the bottom front side leaves a hydraulic manifold mounting area;

[0017] The hydraulic manifold adopts a B-spline curve guide line flow channel to complete the curved pipeline connection between elements.

[0018] The non-solid region is filled with a multi-scale porous structure.

[0019] A design method of an electro-hydraulic ankle prosthesis, the design method is applied to the electro-hydraulic ankle prosthesis, and the design method comprises:

[0020] Based on the human joint actuator mechanism and biomechanical analysis, the hydraulic manifold and the working state of the hydraulic manifold are optimized and designed, wherein the working state comprises passive dorsiflexion, passive plantar flexion, active dorsiflexion and active plantar flexion.

[0021] According to the working state of the hydraulic manifold, the working process of the hydraulic manifold is determined.

[0022] Based on the bionic shape of the lower leg, the hydraulic principle and the additive manufacturing processing mode, the arrangement of the elements in the electro-hydraulic ankle prosthesis is optimized.

[0023] Based on the metal additive manufacturing processing mode, the guide line flow channel based on the B-spline curve is generated, and the generated actual pipeline is tangent to each inlet and outlet.

[0024] The flow channel is iteratively optimized for pressure loss by applying flow channel wall thickness constraints and manifold size constraints until the guide line flow channel corresponding to the minimum overall flow channel pressure loss is obtained.

[0025] The non-solid region inside the electro-hydraulic ankle prosthesis is constructed as a porous structure based on a P-type three-period minimal surface array by using the isosurface represented by the three-dimensional body distance field.

[0026] According to the specific embodiments provided by the present application, the following technical effects are disclosed:

[0027] The hydraulic manifold disclosed by the present application can realize the storage, recovery and overall regulation of the prosthesis energy when the working state of the hydraulic system is passive plantar flexion and passive dorsiflexion, the oil output by the motor pump directly charges the motor energy storage accumulator, when the working state of the hydraulic system is passive dorsiflexion, the hydraulic cylinder directly charges the gravity recovery accumulator, and when the working state of the hydraulic system is active plantar flexion, the total output of the hydraulic system is the sum of the outputs of the motor pump, the gravity recovery accumulator and the motor energy storage accumulator.

[0028] The electric-hydraulic ankle joint prosthesis disclosed by the application arranges design elements in space and adopts a B-spline curve guide line flow channel to complete the connection of curved pipelines between elements, reduces the overall space volume of the prosthesis, and effectively reduces the overall weight by filling the internal non-solid area with a multi-scale porous structure.

[0029] The design method of the electric-hydraulic ankle joint prosthesis disclosed by the application optimizes the overall element integration degree of the prosthesis, the weight and pressure loss of the hydraulic integrated block, ensures the integration and light weight of the prosthesis, and improves the energy utilization efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0031] Figure 1 A hydraulic principle diagram of a hydraulic integrated block provided for the embodiment of the application;

[0032] Figure 2 A structural schematic diagram of an electric-hydraulic ankle joint prosthesis provided for the embodiment of the application;

[0033] Figure 3 A main structure diagram of an electric-hydraulic ankle joint prosthesis provided for the embodiment of the application;

[0034] Figure 4 A multi-scale porous structure area filling result cross-sectional view provided for the embodiment of the application;

[0035] Figure 5 A flowchart of a design method of an electric-hydraulic ankle joint prosthesis provided for the embodiment of the application;

[0036] Figure 6 A principle diagram of a design method of an electric-hydraulic ankle joint prosthesis provided for the embodiment of the application.

[0037] Symbol Explanation: 1-Upper normally closed switch valve, 2-Lower normally closed switch valve, 3-Upper normally open switch valve, 4-Lower normally open switch valve, 5-Motor energy storage accumulator, 6-Gravity recovery accumulator, 7-Oil accumulator, 8-Motor pump, 9-Hydraulic cylinder, 10-Installation position of upper normally closed switch valve, 11-Installation position of lower normally closed switch valve, 12-Installation position of upper normally open switch valve, 13-Installation position of lower normally open switch valve, 14-Installation position of motor energy storage accumulator, 15-Installation position of gravity recovery accumulator, 16-Installation position of oil accumulator, 17-Installation position of small motor pump, 18-Installation position of small hydraulic cylinder, 19-Installation position of liquid pressure sensor, 20-Installation position of prosthetic connection adapter, 21-Installation position of foot frame system, 22-Reserved position for control circuit and chip, 23-Internal flow channel, 24-Porous structure filling area. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, an embodiment of the present invention provides a hydraulic integrated block, including: a motor pump 8, a motor energy storage accumulator 5, a gravity recovery energy storage accumulator 6, an oil storage accumulator 7, a hydraulic cylinder 9, an upper normally open switch valve 3, an upper normally closed switch valve 1, a lower normally open switch valve 4, and a lower normally closed switch valve 2.

[0042] The oil inlet of the motor pump 8 is connected to the oil port of the oil accumulator 7, and the oil outlet of the motor pump 8 is connected to the oil port of the motor energy accumulator 5, one end of the upper normally closed switch valve 1, and one end of the lower normally closed switch valve 2, respectively. When the hydraulic system is in passive plantar flexion and passive dorsiflexion, the oil output by the motor pump 8 directly charges the motor energy accumulator 5.

[0043] The other end of the normally closed switch valve 1 at the upper end is connected to the oil port of the gravity recovery accumulator 6, and the oil port of the gravity recovery accumulator 6 is also connected to the upper oil port of the hydraulic cylinder 9; the other end of the normally closed switch valve 2 at the lower end is connected to the lower oil port of the hydraulic cylinder 9; when the working state of the hydraulic system is passive backbend, the hydraulic cylinder 9 directly charges the gravity recovery accumulator 6.

[0044] The oil port of the oil storage accumulator 7 is also connected with one end of the upper end normally open switch valve 3 and one end of the lower end normally open switch valve 4, the other end of the upper end normally open switch valve 3 is connected with the lower end oil port of the hydraulic cylinder 9, and the other end of the lower end normally open switch valve 4 is connected with the upper end oil port of the hydraulic cylinder 9.

[0045] When the working state of the hydraulic system is active plantar flexion, the motor pump 8 pumps the output oil through the upper end normally closed switch valve 1 into the upper end of the hydraulic cylinder 9, the motor energy storage accumulator 5 releases energy and delivers the stored oil through the upper end normally closed switch valve 1 to the upper end of the hydraulic cylinder 9, and the gravity recovery accumulator 6 releases energy and directly delivers the stored oil to the upper end of the hydraulic cylinder 9.

[0046] According to the characteristics of high instantaneous output power and low idle power demand of the ankle joint, the small motor pump 8 and the motor energy storage accumulator 5 are used to store motor energy, the gravity recovery accumulator 6 is used to recover the energy of the passive dorsiflexion stage, and the energy is concentrated and released in the active plantar flexion stage, so that the light and low-power equipment can complete the instantaneous high-power output, and the energy-saving and lightweight demand of the artificial limb is met.

[0047] The four working states of the hydraulic system are controlled by the upper end normally closed switch valve 1, the lower end normally closed switch valve 2, the upper end normally open switch valve 3 and the lower end normally open switch valve 4. At the same time, the opening degree of each high-speed switch valve is controlled by PWM-PFM (pulse width modulation-pulse frequency modulation), so as to complete the damping control of the artificial limb in the passive state.

[0048] According to the dorsiflexion and plantar flexion state of the human ankle, the passive dorsiflexion, passive plantar flexion, active dorsiflexion and active plantar flexion working states of the hydraulic system are divided. Figure 1 The hydraulic principle diagram shown in the figure completes the time domain deployment of energy. The overall power of the device is lower under the premise that the output capacity of the artificial limb meets the requirements.

[0049] Figure 3 The hydraulic principle and working state shown in the figure, the working process mainly consists of four parts:

[0050] 1. During passive plantar flexion, the lower passive chamber and upper active chamber of the small hydraulic cylinder 9 are connected through two normally open valves: the upper normally open valve 3 and the lower normally open valve 4. The upper normally closed valve 1 and the lower normally closed valve 2 remain closed. The small electric pump 8 outputs oil to directly charge the electric accumulator 5. As the piston rod of the small hydraulic cylinder 9 moves downward, the oil flows from the lower chamber of the hydraulic cylinder 9 back to the oil accumulator 7 through the upper normally open valve 3. At this time, the opening of the upper normally open valve 3 is controlled by PWM-PFM, and the damping effect of the hydraulic oil flow allows the prosthesis to absorb the impact of the ground.

[0051] 2. During passive dorsiflexion, the body's weight does work on the prosthesis. The lower active chamber of the small hydraulic cylinder 9 extracts oil from the oil accumulator 7 through the upper normally open switch valve 3, and directly charges the gravity recovery accumulator 6 through the upper passive chamber, completing the recovery of the body's gravity energy. The upper normally closed switch valve 1 and the lower normally closed switch valve 2 remain closed, and the small motor pump 8 outputs power and continues to directly charge the motor energy accumulator 5.

[0052] 3. During active plantar flexion, which is the process of instantaneous high-power output, the prosthesis pushes off the ground. At this time, the output torque and output power of the ankle prosthesis are extremely high. The total output of the hydraulic system at this time is the sum of the outputs of the small electric motor pump 8, the gravity recovery accumulator 6, and the electric motor energy storage accumulator 5. The small electric motor pump 8 outputs energy to the upper end of the small hydraulic cylinder 9 through the normally closed switch valve 1 at the upper end; the gravity recovery accumulator 6 outputs energy recovered by the human body's weight during the passive dorsiflexion phase at the upper end of the small hydraulic cylinder 9 through the normally closed switch valve 1 at the upper end; the electric motor energy storage accumulator 5 outputs energy accumulated by the small electric motor pump 8 during the passive plantar flexion and passive dorsiflexion phases at the upper end of the small hydraulic cylinder 9 through the normally closed switch valve 1 at the upper end. At this time, the hydraulic oil at the lower end of the cylinder flows back to the oil storage accumulator 7 through the normally open switch valve 3 at the upper end, while the normally closed switch valve 2 and the normally open switch valve 4 at the lower end remain closed.

[0053] 4. During the active dorsiflexion phase, the lower normally open valve 4 and the lower normally closed valve 2 are opened, while the upper normally closed valve 1 and the upper normally open valve 3 are closed. The small electric pump 8 directly performs work on the lower end of the small hydraulic cylinder 9 through the lower normally closed valve 2, and the oil flows back to the oil accumulator 7 from the upper end through the lower normally open valve 4, completing the active dorsiflexion of the prosthesis.

[0054] This invention proposes a micro-hydraulic circuit suitable for ankle prostheses. By analyzing human gait and optimizing energy in the time domain, it can store and recover energy at different stages of human walking, reducing unnecessary increases in parameters such as the weight of drive components and energy waste caused by excessive peak power in the prosthesis.

[0055] Example 2

[0056] like Figure 2As shown, the embodiment of the present application provides an electro-hydraulic ankle prosthesis, comprising: a prosthesis connection adapter, a plurality of liquid pressure sensors and the hydraulic integrated block of embodiment one.

[0057] The prosthesis connection adapter, the plurality of liquid pressure sensors and the motor energy storage accumulator 5, the gravity recovery accumulator 6 and the oil storage accumulator 7 in the hydraulic integrated block are all arranged at the top, the top of the prosthesis connection adapter, the bottom of the motor energy storage accumulator 5, the bottom of the gravity recovery accumulator 6 and the bottom of the oil storage accumulator 7 are located at the topmost end, and the plurality of liquid pressure sensors are arranged in the gap between the prosthesis connection adapter and the motor energy storage accumulator 5, the gravity recovery accumulator 6 and the oil storage accumulator 7. The hydraulic cylinder 9 in the hydraulic integrated block is installed at the front. The upper end normally open switch valve 3, the upper end normally closed switch valve 1, the lower end normally open switch valve 4 and the lower end normally closed switch valve 2 in the hydraulic integrated block are arranged on the right side, and the outer surface of the right side is stepped; the outer surface of the right rear end is cut inward under the premise of ensuring that the motor is completely matched with the installation plane, and the right front section is cut inward until it just meets the required volume of the pipeline. The hydraulic pump in the hydraulic integrated block is placed at the rear along the height direction. The bottom is cut inward from the rear side to the front side, so that the front side of the bottom leaves the hydraulic integrated block installation area. The hydraulic integrated block uses a B-spline curve guide line flow channel to complete the curved pipeline connection between elements. A multi-scale porous structure is used to fill the non-solid area.

[0058] Figure 2 The upper end normally closed switch valve installation position 10, the lower end normally closed switch valve installation position 11, the upper end normally open switch valve installation position 12, the lower end normally open switch valve installation position 13, the motor energy storage accumulator installation position 14, the gravity recovery accumulator installation position 15, the oil storage accumulator installation position 16, the small motor pump installation position 17, the small hydraulic cylinder installation position 18, the liquid pressure sensor installation position 19 and the prosthesis connection adapter installation position 20 are shown.

[0059] Further, the left side space of the electro-hydraulic ankle prosthesis is the control circuit and chip reserved position 22. The front side of the bottom is provided with a foot skeleton installation position.

[0060] As Figure 3The main structure of an ankle prosthesis is shown, and the prosthesis is composed of a motor pump 8, a high-speed on-off valve, a sensor system, a hydraulic integrated block and other components. Among them, the hydraulic integrated block is the core component, which has the functions of connection, support, transmission, etc., and should be a high-energy-efficiency lightweight component. The present application realizes high energy efficiency through automatic generation of micro oil circuit and pressure loss optimization, realizes lightweight through three-period minimal surface porous solid region filling and component selection, and realizes integration through overall component arrangement based on additive manufacturing. The optimized hydraulic integrated block component arrangement is more compact, the system energy utilization efficiency is higher, the space volume is smaller, the user's additional burden is less, etc.

[0061] Based on the bionic shape of the lower leg, the layout of each component is carried out. The customization of the flexible flow channel brought by metal additive manufacturing changes the component arrangement mode on the hydraulic integrated block. More components can be placed in a limited space, making full use of the surface area of the integrated block, ultimately reducing the size of the system and reducing the weight of the system. The overall prosthesis is spindle-like, and the specific component arrangement of each part is as follows:

[0062] 1. The top is provided with various types of elongated components with axial length greater than radial diameter: liquid pressure sensor, motor energy storage accumulator 5, gravity recovery accumulator 6, oil storage accumulator 7 and prosthesis connection adapter. The prosthesis adapter is placed in the center as the support main body, three pressure sensors and three accumulators are arranged around it. The adapter flange structure with top large and bottom small and the accumulator with top small and bottom large can be arranged compactly without interfering with each other. The hydraulic sensor is arranged in the gap between the adapter and the accumulator. The overall horizontal projection of each component on the top is the smallest, and the height is consistent with the highest one;

[0063] 2. The front is provided with a small hydraulic cylinder 9 mounting position, and the upper and lower surfaces of the hydraulic cylinder 9 base are flush with the upper and lower surfaces of the integrated block;

[0064] 3. The left side space is reserved for control circuit and chip 22;

[0065] 4. The right side is designed with upper and lower end normally closed and normally open on-off valve mounting positions and oil filling port. In order to further reduce the length of the flow channel and remove unnecessary components of the integrated block, the right side surface is designed as a stepped shape: because the rear surface needs to install a motor, the right rear end surface is cut inward slightly under the premise of ensuring that the motor and the mounting plane cooperate completely, and the right front section is cut inward until it just meets the volume required by the necessary pipeline;

[0066] 5. The rear is provided with a small motor pump 8 mounting position. In order to ensure the spindle-like structure of the overall prosthesis, the hydraulic pump is placed along the height direction, reducing the size of the prosthesis in the horizontal plane;

[0067] 6, The bottom front side is provided with a foot skeleton system mounting position 21, and the volume of the integrated block is reduced inwardly until the necessary integrated block mounting area is left on the front side. The element arrangement on each surface fully utilizes the integrated block space, optimizes the integrated block and prosthesis volume, and simplifies the overall installation and maintenance process.

[0068] In order to ensure the small volume and light weight of the prosthesis as a whole, the hydraulic integrated block is combined with the support body in the present application, and serves as the mounting base of all elements. According to the calf modeling design and the layer-by-layer stacking processing characteristics of additive manufacturing, the element arrangement is compacted, unnecessary space of the integrated block is removed, so that the overall structure of the prosthesis is more compact, and the occupied space is smaller. The integrated block element interface and flow channel pipeline diagram as shown in Figure 2 is obtained. The integrated block pipeline is built-in, reducing the use of external connecting pipelines and reducing system vibration. The distance between elements such as motors and pumps is shorter, reducing the pressure loss along the flow channel. Then under the constraints of flow channel wall thickness and integrated block size, according to the hydraulic schematic diagram pipeline connection and element arrangement, the B-spline curve guide line flow channel generation and optimization iteration of the given inlet and outlet section is completed. The optimized flow channel has smaller pressure loss and higher energy utilization rate compared with the traditional straight flow channel.

[0069] Finally, the internal lightweight of the hydraulic integrated block is realized, as shown in Figure 4 based on the calf modeling design, the non-essential solid area in the integrated block is filled with multi-scale porous structure. The isosurface represented by the three-dimensional body distance field is used to create the polyhedral surface and fill the area. The non-essential area in the valve body is constructed into a porous structure based on a three-period minimal surface to reduce weight. The local lightweight of the integrated block is realized under the premise of ensuring strength.

[0070] The advantages of the embodiment of the present application are:

[0071] (1) The present application completes the oil circuit design according to the processing characteristics of additive manufacturing. Additive manufacturing adopts a bottom-up, layer-by-layer accumulation forming method, which has low geometric sensitivity to the required formed model, so that the element space arrangement can be better designed, and the overall space volume of the prosthesis can be reduced;

[0072] (2) The present application replaces the external connecting pipeline with the pipeline inside the valve block, combines with the support body, saves the overall space of the prosthesis, and reduces the overall weight; at the same time, reduces the pipeline vibration, and the system is more stable;

[0073] (3) The present application completes the connection of customized curved pipelines based on a B-spline curve forming method, avoids the overlapping and complex characteristics of conventional straight pipelines, reduces the overall pressure loss, and improves the energy conversion efficiency;

[0074] (4) The application constructs a multi-scale porous structure in the filling area of the valve block, fills and calculates by using a volume distance field, and fills the solid area by using a three-period minimal surface primitive, which is consistent with the characteristics of additive manufacturing and effectively reduces the overall weight.

[0075] Example Three

[0076] As Figure 5 shown, the embodiment of the application provides a design method of an electro-hydraulic ankle prosthesis, which is applied to the electro-hydraulic ankle prosthesis of example two, and the design method comprises the following steps:

[0077] Step 1: Based on the human joint actuation mechanism and biomechanical analysis, the hydraulic integrated block and the working state of the hydraulic integrated block are optimized and designed, wherein the working state comprises passive dorsiflexion, passive plantar flexion, active dorsiflexion and active plantar flexion.

[0078] The determination of the actuation characteristics of the hydraulic system is based on the human joint actuation mechanism and the biomechanical analysis of power. Then, the energy time domain control and the prosthesis working state switching are performed to obtain the hydraulic integrated block of example one.

[0079] Step 2: According to the working state of the hydraulic integrated block, the working process of the hydraulic integrated block is determined.

[0080] The specific working process of the hydraulic integrated block is described in the working process of the hydraulic integrated block of example one, which is not repeated here.

[0081] Step 3: Based on the bionic shape of the lower leg, the hydraulic principle and the additive manufacturing processing mode, the arrangement of the elements in the electro-hydraulic ankle prosthesis is optimized.

[0082] The close arrangement of the elements in the electro-hydraulic ankle prosthesis is as described in example two.

[0083] Step 4: Based on the metal additive manufacturing processing mode, a guide line flow channel based on B-spline curve is generated, and the generated actual pipeline is tangent to each inlet and outlet.

[0084] Unlike the traditional straight flow channel, the internal flow channel 23 uses B-spline curve as a guide line and sweeps the pipe diameter to form, and on the basis of the given outlet space coordinates and vectors, the flow channel wall thickness constraint and the integrated block size constraint are applied. The elements and pipelines are arranged in the smallest space to reduce the flow channel pressure loss and improve the energy efficiency.

[0085] The B-spline curve is a parametric curve composed of a series of polynomial segments, which is affected by the control points and the B-spline basis function: Wherein is the B-spline curve, is the control point, is the p-th B-spline basis function, and n is the number of control points. The definition of B-spline basis function can be carried out by recursion: for p = 0 (zero order): ; for p > 0 (order greater than zero): ; wherein represents the i-th node vector. Compared with traditional curves, B-spline curves are more flexible and easier to accurately control the curve shape, so they are applied to the flow passage design.

[0086] According to the pipeline interconnection condition shown in the hydraulic system schematic diagram, Figure 1 the B-spline curve guide line flow passage is used to complete the pipeline connection between components, and the actual pipeline generated is tangent to each inlet and outlet. Let the spatial position coordinates of the first i component connection port be , and the flow passage vector at the connection port be . The third-order B-spline curve formula is used to obtain a guide line containing four initial control points, and then the pipeline spatial position set is obtained by sweeping along the guide line with the pipeline diameter D as the contour, and a round corner transition is added to the pipeline intersection part.

[0087] That is, according to the spatial position coordinates of each component connection port and the flow passage vector at the connection port, a guide line containing initial control points is obtained by using B-spline curve; the pipeline spatial position set is obtained by sweeping along the guide line with the pipeline diameter as the contour, and a round corner transition is added to the pipeline intersection part, and based on the metal additive manufacturing processing method, a B-spline curve-based guide line flow passage is generated.

[0088] The flow passage formed by the B-spline curve can well reduce the pressure loss and energy loss of the fluid through simulation verification, so the B-spline curve has great advantages compared with the traditional straight line flow passage / simple curved flow passage. The traditional machining method cannot process the complex curved internal flow passage like B-spline, and only the additive manufacturing processing method can complete the machining, so as to achieve the purpose of reducing pressure loss.

[0089] The customized bendable flow passage brought by metal additive manufacturing changes the arrangement method of components on the hydraulic integrated block, more components can be placed in a limited space, the surface area of the integrated block is fully utilized, and finally the size and weight of the system are reduced.

[0090] Step 5: Apply the flow passage wall thickness constraint and the integrated block size constraint, and iteratively optimize the pressure loss of the flow passage until the guide line flow passage corresponding to the minimum overall flow passage pressure loss under the flow passage wall thickness constraint and the integrated block size constraint is obtained.

[0091] The flow channel wall thickness and the integrated block size constraint are applied, new control points are applied at the interference part to meet the constraint condition, pressure loss analysis is carried out on the flow channel, and iterative optimization is carried out until the minimum overall flow channel pressure loss is obtained under the condition of meeting the constraint condition. The selection of the intermediate control point is limited by the flow channel inlet and outlet position and size wall thickness constraint, wherein the flow channel wall thickness constraint is represented as , wherein B is the wall thickness, P is the internal pressure, D is the pipe diameter, S is the allowable stress of the material, N is the safety factor, and the obtained constraint region is ; ; ; is a B-spline curve parameter equation, and s represents the path length of the flow channel along the B-spline curve. The integrated block size constraint is determined by element selection and biomimetic integrated arrangement, and the pipeline needs to be wrapped in the three-dimensional space of the integrated block, that is , and the optimized pipeline obtained in this example is shown in Figure 2 .

[0092] The detailed process of step 6 is: determining the flow channel wall thickness constraint as , wherein B is the wall thickness, P is the internal pressure, D is the pipe diameter, N is the safety factor, S is the allowable stress of the material; determining the integrated block size constraint as , wherein represents the three-dimensional space coordinates of the intermediate control point b, represents the three-dimensional space coordinates of the hydraulic integrated block, , and , is a cubic B-spline curve parameter equation, s represents the path length of the flow channel along the B-spline curve, represents the B-spline basis function of the intermediate control point b; iterative optimization of the flow channel pressure loss is carried out until the minimum overall flow channel pressure loss is obtained under the condition of meeting the flow channel wall thickness constraint and the integrated block size constraint; and the guide line flow channel corresponding to the minimum overall flow channel pressure loss is taken as the optimal guide line flow channel.

[0093] The B-spline curve is connected with the inlet and outlet and is tangent to them, and the intermediate control point is determined by the hydraulic system schematic diagram, the flow channel wall thickness constraint and the integrated block size constraint.

[0094] Step 6: The equal-area surface represented by the three-dimensional body distance field is used to construct the internal non-solid area of the electro-hydraulic ankle joint prosthesis into a porous structure based on a P-type three-periodic minimal surface array.

[0095] Figure 4The cross-sectional view of the filling result of the multi-scale porous structure region of the hydraulic integrated block of the artificial limb. The complex topology not only shows the best cost-effective mechanical properties in mechanics, but also has a very light weight. The three-period minimal surface shows excellent performance in mechanical properties, and its smoothness, full connectivity and quasi-self-naming can ensure that the internal force can be continuously and smoothly transmitted and kept stable without additional support. Among them, the P-type minimal surface can more evenly distribute stress due to the three-direction periodic prismatic structure, and has superior compression resistance. At the same time, compared with other more complex three-period minimal surfaces, the structure of the P-type surface is relatively simple, so in the additive manufacturing with limited processing precision, the P-type surface is easier to be accurately copied.

[0096] Therefore, the local lightweight filling idea of the integrated block is to create a polyhedral surface and fill the region by using the isosurface represented by the three-dimensional scalar distance field. The unnecessary region inside the valve body is constructed as a porous structure based on an array of P-type three-period minimal surfaces to reduce weight.

[0097] The specific process of step 6 is as follows:

[0098] 6.1: Discretize the three-dimensional model of the electro-hydraulic ankle prosthesis.

[0099] According to the geometric shape of the electro-hydraulic ankle prosthesis, it is discretized into three-dimensional grid or point cloud data.

[0100] 6.2: Calculate the distance from each discrete point to the nearest pipe centerline.

[0101] Adopt the nearest point-based distance estimation, and set the isosurface as the set of minimum distances from each point in space to the pipe centerline .

[0102] 6.3: Determine the distance threshold for solid filling based on human external load simulation and metal additive manufacturing processing condition limitations.

[0103] When calculating the distance threshold for solid filling, human external load simulation results, metal additive manufacturing processing condition limitations and other influencing factors need to be considered. Human external load simulation results include stress distribution, stress conditions and other information. Metal additive manufacturing processing condition limitations include available materials, characteristics of manufacturing equipment, etc. Other influencing factors include design requirements, performance requirements, etc.

[0104] 6.4: Remove the discrete points with a distance greater than the distance threshold, and all removed discrete points constitute a non-solid region, and all unremoved discrete points constitute a solid region.

[0105] Remove the discrete points in space that satisfy , where D is the pipe diameter, B is the safety thickness, and A is the processing error.

[0106] 6.5: The intersection operation between the non-solid region and the P-type three-period minimal surface array is performed to obtain a porous structure based on the P-type three-period minimal surface array.

[0107] Boolean operation on the intersection of the two Obtain the internal porous structure filling region 24. This represents a P-type three-period minimal surface array. This indicates a non-physical region.

[0108] Stress simulation and iterative modifications can then be performed. If the integrated block is subsequently subjected to additional processing or external loads, necessary structures can be added based on the optimization results to ensure operational safety until the integrated block meets the structural strength requirements of the prosthesis under the intended working conditions.

[0109] 6.6: The porous structure based on the P-type three-period minimal surface array is recombined with the solid region to form a three-dimensional model of the electrohydraulic ankle joint prosthesis.

[0110] Therefore, the internal porous structure filling region 24 is obtained by intersecting the P-type three-period minimal surface array with the volume distance field of the filling region. The three-dimensional volume distance field is set as the minimum distance from each point in space to the center line of the pipeline, and is compared with the pipeline diameter and safety thickness constraints to determine the region to be filled. The volume distance field of the filling region is calculated based on the position of the guide line in each pipeline, the flow channel wall thickness, and the integrated block size constraints.

[0111] like Figure 6 The design principles of the electro-hydraulic ankle prosthesis illustrated include human motion characteristic analysis, hydraulic system optimization design, integrated component layout, internal flow channel optimization, and multi-scale porous structure filling. This method provides a technical means for designing and manufacturing a class of high-energy-efficiency, lightweight hydraulic integrated blocks.

[0112] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The methods disclosed in the embodiments are described simply because they correspond to the apparatus disclosed in the embodiments; relevant details can be found in the method section.

[0113] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An electro-hydraulic ankle prosthesis, characterized in that The electro-hydraulic ankle prosthesis comprises a prosthesis connection adapter, a plurality of liquid pressure sensors and a hydraulic integrated block; The hydraulic integrated block comprises a motor pump, a motor energy storage accumulator, a gravity recovery accumulator, an oil storage accumulator, a hydraulic cylinder, an upper end normally open switch valve, an upper end normally closed switch valve, a lower end normally open switch valve and a lower end normally closed switch valve; The oil inlet of the motor pump is connected with the oil port of the oil storage accumulator, and the oil outlet of the motor pump is connected with the oil port of the motor energy storage accumulator, one end of the upper end normally closed switch valve and one end of the lower end normally closed switch valve respectively; when the working state of the hydraulic system is passive plantar flexion and passive dorsiflexion, the oil output by the motor pump directly charges the motor energy storage accumulator; The other end of the upper end normally closed switch valve is connected with the oil port of the gravity recovery accumulator, and the oil port of the gravity recovery accumulator is also connected with the upper end oil port of the hydraulic cylinder; the other end of the lower end normally closed switch valve is connected with the lower end oil port of the hydraulic cylinder; when the working state of the hydraulic system is passive dorsiflexion, the hydraulic cylinder directly charges the gravity recovery accumulator; The oil port of the oil storage accumulator is also connected with one end of the upper end normally open switch valve and one end of the lower end normally open switch valve, the other end of the upper end normally open switch valve is connected with the lower end oil port of the hydraulic cylinder, and the other end of the lower end normally open switch valve is connected with the upper end oil port of the hydraulic cylinder; When the working state of the hydraulic system is active plantar flexion, the motor pump pumps the output oil into the upper end of the hydraulic cylinder through the upper end normally closed switch valve, the motor energy storage accumulator releases energy and delivers the stored oil to the upper end of the hydraulic cylinder through the upper end normally closed switch valve, and at the same time, the gravity recovery accumulator releases energy and directly delivers the stored oil to the upper end of the hydraulic cylinder; The upper end normally open switch valve, the upper end normally closed switch valve, the lower end normally open switch valve and the lower end normally closed switch valve are all controlled by pulse width-pulse frequency modulation; The prosthesis connection adapter, the plurality of liquid pressure sensors and the motor energy storage accumulator, the gravity recovery accumulator and the oil storage accumulator in the hydraulic integrated block are all arranged at the top, the top of the prosthesis connection adapter, the bottom of the motor energy storage accumulator, the bottom of the gravity recovery accumulator and the bottom of the oil storage accumulator are located at the topmost end, and the plurality of liquid pressure sensors are arranged in the gap between the prosthesis connection adapter and the motor energy storage accumulator, the gravity recovery accumulator and the oil storage accumulator; The hydraulic cylinder in the hydraulic integrated block is installed at the front; The upper end normally open switch valve, the upper end normally closed switch valve, the lower end normally open switch valve and the lower end normally closed switch valve in the hydraulic integrated block are arranged at the right side, and the outer surface of the right side is stepped; the outer surface of the right rear end is cut inward under the premise of ensuring that the motor completely matches the installation plane, and the right front section is cut inward until it just meets the required volume of the pipeline; The hydraulic pump in the hydraulic integrated block is placed at the rear along the height direction; The bottom is cut inward from the rear to the front, so that the front side of the bottom leaves the installation area of the hydraulic integrated block; The hydraulic integrated block uses B-spline curve guide flow channel to complete the curved pipeline connection between elements; A multi-scale porous structure is used to fill the non-solid region; The left space of the electro-hydraulic ankle prosthesis is the reserved position of the control circuit and chip; the front side of the bottom is provided with a foot skeleton installation position.

2. A method of designing an electro-hydraulic ankle prosthesis, characterized in that, The design method is applied to the electro-hydraulic ankle prosthesis of claim 1, and the design method comprises: Based on the human joint actuator mechanism and biomechanical analysis, the hydraulic integrated block and the working state of the hydraulic integrated block are optimized; wherein the working state includes passive dorsiflexion, passive plantar flexion, active dorsiflexion and active plantar flexion; According to the working state of the hydraulic integrated block, the working process of the hydraulic integrated block is determined; Based on the bionic shape of the lower leg, the hydraulic principle and the additive manufacturing processing mode, the arrangement of the elements in the electro-hydraulic ankle prosthesis is optimized; Based on the metal additive manufacturing processing mode, the guide line flow channel based on the B-spline curve is generated, and the generated actual pipeline is tangent to each inlet and outlet; The flow channel is iteratively optimized for pressure loss under the constraints of flow channel wall thickness and integrated block size until the guide line flow channel corresponding to the minimum overall flow channel pressure loss under the constraints of flow channel wall thickness and integrated block size is obtained; The isosurface of three-dimensional body distance field is used to construct the internal non-solid area of the electro-hydraulic ankle prosthesis into a porous structure based on a P-type three-period minimum surface array.

3. The method of designing an electro-hydraulic ankle prosthesis according to claim 2, characterized in that, The working process of the hydraulic integrated block comprises: Passive plantar flexion process: the upper end normally open switch valve and the lower end normally open switch valve are both conductive, the upper end normally closed switch valve and the lower end normally closed switch valve remain closed, and the oil output by the motor pump directly charges the motor energy storage accumulator; the piston rod of the hydraulic cylinder moves downward, and the oil flows back to the oil storage accumulator from the lower cavity of the hydraulic cylinder through the upper end normally open switch valve; and the opening degree of the upper end normally open switch valve is controlled by pulse width-pulse frequency modulation; Passive dorsiflexion process: the human body gravity works on the prosthesis, the lower active cavity of the hydraulic cylinder extracts oil from the oil storage accumulator through the upper end normally open switch valve, and directly charges the gravity recovery accumulator through the upper end passive cavity to complete the human body gravity energy recovery; the upper end normally closed switch valve and the lower end normally closed switch valve continue to remain closed, and the oil output by the motor pump continues to directly charge the motor energy storage accumulator; Active plantar flexion process: the total output of the hydraulic system at this time is the sum of the outputs of the motor pump, the gravity recovery accumulator and the motor energy storage accumulator; wherein the oil output by the motor pump passes through the upper end normally closed switch valve to the upper end of the hydraulic cylinder; the gravity recovery accumulator outputs the energy recovered by the human body gravity during the passive dorsiflexion stage at the upper end of the hydraulic cylinder; the motor energy storage accumulator outputs the energy accumulated by the motor pump during the passive plantar flexion and passive dorsiflexion stages at the upper end of the hydraulic cylinder through the upper end normally closed switch valve; at this time, the lower end hydraulic oil of the hydraulic cylinder flows back to the oil storage accumulator through the upper end normally open switch valve, and the lower end normally closed switch valve and the lower end normally open switch valve remain closed; Active dorsiflexion stage process: the lower end normally open switch valve and the lower end normally closed switch valve are opened, and the upper end normally closed switch valve and the upper end normally open switch valve are closed; the motor pump directly works on the lower end of the hydraulic cylinder through the lower end normally closed switch valve, and the oil flows back to the oil storage accumulator from the upper end through the lower end normally open switch valve.

4. The method of designing an electro-hydraulic ankle prosthesis according to claim 2, wherein, Based on the metal additive manufacturing processing mode, the guide line flow channel based on the B-spline curve is generated, specifically comprising: According to the spatial position coordinates of each element connection port and the flow channel vector at the connection port, the guide line containing the initial control point is obtained by using the B-spline curve; A set of pipe spatial positions is obtained by sweeping along the guide line with the pipe diameter as a contour, and a round transition is added at the pipe intersection part, and a guide line runner based on B-spline curve is generated based on the metal additive manufacturing processing mode.

5. The method of designing an electro-hydraulic ankle prosthesis according to claim 2, wherein, The runner is iteratively optimized for pressure loss with application of runner wall thickness constraints and integrated block size constraints until a guide line runner corresponding to the minimum overall runner pressure loss is obtained, specifically including: The flow passage wall thickness constraint is determined as ; wherein, B is the wall thickness, P is the internal pressure, D is the pipe diameter, N is the safety factor, S is the allowable stress of the material; The integrated block size constraint is determined as ; wherein represents the three-dimensional spatial coordinates of the intermediate control point b, represents the three-dimensional spatial coordinates of the hydraulic integrated block, , and , is a cubic B-spline parametric equation, s represents the path length of the flow channel along the B-spline curve, represents the B-spline base function of the intermediate control point b. The runner is iteratively optimized for pressure loss until the minimum overall runner pressure loss is obtained under the satisfaction of runner wall thickness constraints and integrated block size constraints; The guide line runner corresponding to the minimum overall runner pressure loss is taken as the optimal guide line runner.

6. The method of designing an electro-hydraulic ankle prosthesis according to claim 2, wherein, The internal non-solid area of the electro-hydraulic ankle prosthesis is constructed as a porous structure based on a P-type three-period minimal surface array using an isosurface represented by a three-dimensional body distance field, specifically including: Discretize the three-dimensional model of the electro-hydraulic ankle prosthesis; Calculate the distance from each discrete point to the nearest pipe center line; Determine the distance threshold for solid filling based on human body external load simulation and metal additive manufacturing processing condition constraints; Remove discrete points with a distance greater than the distance threshold, and all removed discrete points constitute a non-solid area, and all non-removed discrete points constitute a solid area; Intersect the non-solid area with the P-type three-period minimal surface array to obtain a porous structure based on the P-type three-period minimal surface array; Recombine the porous structure based on the P-type three-period minimal surface array with the solid area into the three-dimensional model of the electro-hydraulic ankle prosthesis.

Images