| Ankle prosthesis have been playing an irreplaceable important role as rehabilitation assistant devices.At present,the performance of ankle prosthesis is getting improved with the relative studies development.Ankle prosthesis can be classified as passive,active,and hybrid type.The active and the hybrid type have complex electromechanical control systems and can adapt to different walking situations,but their stability is reduced,the energy consumption ratio is high,and wearing comfortability is poor due to the high fabrication,maintenance cost,and their own bigger weight.etc.Meanwhile,most of the existing passive prosthetics are mainly designed with mechanical hinges,which cannot assist amputees to regain the natural motion gait effectively.The rigid prosthesis cannot better reappear motion functional characteristics of the human ankle articulation due to the limitation of their own construction design.So it is essential to develop ankle prosthesis with more accessibility to the biomechanical characteristics of the human ankle articulation motion.Human ankle articulation appears as a 3D composite motion in space,it behaves the particular motion characteristics in different stages of the gait period,and the simple fixed-axis structure cannot reappear the biomechanical characteristics of the ankle articulation perfectly.In our work,Considering the unnatural locomotion,and poor wearing comfortability of the rigid ankle prosthesis,the human skeleton muscle system is selected as the bionic prototype,the design principle of the flexible ankle articular prosthesis with bionic human skeleton muscle system is proposed in order to better simulate the motion functional characteristics of the ankle articulation.Compared to the traditional rigid prosthesis,the bionic flexible prosthesis can provide a larger range of motion while ensuring stability,and it can partially simulate the kinematics and dynamics characteristics of the human ankle articulation to restore the 3D natural motion of the patient’s leg and improve the wearing comfortability.In our research,Firstly,the prosthesis of the ankle and its articulation were designed inspired by the human skeleton muscle system.Then,the prosthesis of the multi curved surface fitting type and multi-articulation surface morphology optimized type were designed by the morphological optimization of the human skeleton muscle system.Finally,the prosthesis of the anatomical articular axis type and the motorial functional axis type were designed iteratively inspired by the ankle articular skeleton muscle system.The main content and conclusions of the work are as follows:(1)Four types of traditional rigid ankle prosthesis were designed and optimized.They are the bionic rigid single degree of freedom(DOF)prosthesis first generation(XJL2S01)and its second generation(XJL2S01A),the bionic rigid double DOF prosthesis first generation(XJL2P01),and its second generation(XJL2P01A).For the purpose to evaluate the designed prosthesis,a series of bench tests were conducted based on Chinese National Standards.The test results show,all the above four types of prosthesis meet the relevant requirements.XJL2P01 A type performed best in the statics tests,followed by XJL2P01 type,XJL2S01 A type,and XJL2S01 type.(2)The human skeleton muscle system was rebuilt by reverse engineering technology.Rigid-flexible coupling prosthesis and flexible prosthesis bio-inspired by ankle structure were designed by the inspiration.During the design of the rigid-flexible coupling prosthesis,the structural characteristics of the human articular capsule,ligament,and other tissues were simulated.The human ankle skeleton is fabricated of flexible materials is located and connected,and the motion style and range of the articulation were determined.During the design of the flexible prosthesis bio-inspired by ankle structure,the ankle articulation remained merely,and the flexible inclusion configuration was selected as the alternative human soft tissue was determined by the finite element analysis(FEA).Besides,The designed prosthesis have brilliant variable stiffness performance verified by the FEA method,and the motion of the internal rotation axis of the human ankle articulation can be copied.(3)In order to improve the process efficiency and enhance the bearing capacity of the prosthesis,two types of bionic flexible prosthesis were designed by the optimized3 D morphology of the human ankle articulation surface.They are multi curved surface fitting bionic prosthesis and multi-articulation surface morphology optimized bionic prosthesis.In the design of the multi curved surface fitting bionic prosthesis,the prosthesis can imitate the motion characteristics of the human ankle articulation better by the curved surface meshing among different bionic skeleton modules in the prosthesis.In the design of the multi-articulation surface morphology optimized bionic prosthesis,the planar rotation of the prosthesis can be achieved,the prosthesis can get a larger motion range by the combing design of the rotating pairs among bionic skeleton modules.All the inner bionic skeleton modular configurations of the two types of prosthesis were bio-inspired by the nature which optimized abstracted from the human corresponding skeleton surface morphology.(4)For the purpose of improving the recurrent range of the ankle articulation locomotive function reproduced by the prosthesis,combining optimization of the ankle skeleton muscle system and the calculation,and the simulation of the inner rotation axis during its locomotion,The anatomical articular axis prosthesis and the motorial functional axis prosthesis were designed iteratively to reproduce the biomechanical characteristics better.In the design of the anatomical articular axis prosthesis,the inspiration was referenced from the relative definition of the ankle rotation axis in the anatomy.In the design of the motorial functional axis prosthesis,the inspiration was referenced by the corresponding theory of ankle articular momentary rotation axis.(5)Synthesizing the four types of traditional rigid prosthesis and the four types of bionic flexible prosthesis,human wearing,and energy consumption tests were conducted.The test results can be concluded.For the data fitting degree of the kinematics and dynamics of the healthy side limbs,the groups wearing bionic flexible prosthesis are better than the groups wearing bionic rigid prosthesis.The parameters of the sagittal plane under normal speed can be selected as examples,the root mean square error of the motion angle of female and male groups that wear bionic motorial functional axis prosthesis is 49.78% and 32.38% lower than that of the bionic rigid single DOF prosthesis(XJL2S01),the mean square error of torque is 35.48% and 20.01%lower respectively.Besides,for oxygen absorption efficiency,the groups wearing bionic flexible prosthesis are better than the groups wearing traditional rigid prosthesis.For the male examinees,the slope value of the oxygen absorption efficiency,the highest bionic motorial functional axis prosthesis group is higher than the lowest traditional rigid single-DOF prosthesis(XJL2S01)about 63.63%,and the difference value in female examinees is 81.32%.The two types combined the skeleton muscle system morphological optimized and the ankle rotation axis with motorial functional copy are superior to the two types based on the skeleton muscle system morphological optimization merely.As a result,the motorial functional axis prosthesis performs best,followed by the anatomical articular axis prosthesis,multi-articulation surface morphology optimized bionic prosthesis,and the multi curved surface fitting bionic prosthesis.Besides,the multi-DOF prosthesis is superior to the single DOF prosthesis,and the second-generation prosthesis with the inner structure loading improved is superior to the first-generation prosthesis with the simple structure designed. |
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