Due to the dynamic stiffness characteristics of human joints, it is easy to cause impact and disturbance on normal movements during exoskeleton assistance. This not only brings strict requirements for exoskeleton cont...Due to the dynamic stiffness characteristics of human joints, it is easy to cause impact and disturbance on normal movements during exoskeleton assistance. This not only brings strict requirements for exoskeleton control design, but also makes it difficult to improve assistive level. The Variable Stiffness Actuator (VSA), as a physical variable stiffness mechanism, has the characteristics of dynamic stiffness adjustment and high stiffness control bandwidth, which is in line with the stiffness matching experiment. However, there are still few works exploring the assistive human stiffness matching experiment based on VSA. Therefore, this paper designs a hip exoskeleton based on VSA actuator and studies CPG human motion phase recognition algorithm. Firstly, this paper puts forward the requirements of variable stiffness experimental design and the output torque and variable stiffness dynamic response standards based on human lower limb motion parameters. Plate springs are used as elastic elements to establish the mechanical principle of variable stiffness, and a small variable stiffness actuator is designed based on the plate spring. Then the corresponding theoretical dynamic model is established and analyzed. Starting from the CPG phase recognition algorithm, this paper uses perturbation theory to expand the first-order CPG unit, obtains the phase convergence equation and verifies the phase convergence when using hip joint angle as the input signal with the same frequency, and then expands the second-order CPG unit under the premise of circular limit cycle and analyzes the frequency convergence criterion. Afterwards, this paper extracts the plate spring modal from Abaqus and generates the neutral file of the flexible body model to import into Adams, and conducts torque-stiffness one-way loading and reciprocating loading experiments on the variable stiffness mechanism. After that, Simulink is used to verify the validity of the criterion. Finally, based on the above criterions, the signal mean value is removed using feedback structure to complete the phase recognition algorithm for the human hip joint angle signal, and the convergence is verified using actual human walking data on flat ground.展开更多
DNA methylation is a critical epigenetic regulator in the occurrence and development of diseases and is closely related to various functional responses in relation to spinal cord injury.To investigate the role of DNA ...DNA methylation is a critical epigenetic regulator in the occurrence and development of diseases and is closely related to various functional responses in relation to spinal cord injury.To investigate the role of DNA methylation in spinal cord injury,we constructed a library with reduced-representation bisulfite sequencing data obtained at various time points(day 0-42)after spinal cord injury in mice.Global DNA methylation levels,specifically non-CpG(CHG and CHH)methylation levels,decreased modestly following spinal cord injury.Stages post-spinal cord injury were classified as early(day 0-3),intermediate(day7-14),and late(day 28-42)based on similarity and hie rarchical cluste ring of global DNA methylation patterns.The non-CpG methylation level,which included CHG and CHH methylation levels,was markedly reduced despite accounting for a minor proportion of total methylation abundance.At multiple genomic sites,including the 5’untranslated regions,promoter,exon,intron,and 3’untranslated regions,the non-CpG methylation level was markedly decreased following spinal cord injury,whereas the CpG methylation level remained unchanged at these locations.Approximately one-half of the differentially methylated regions were located in intergenic areas;the other differentially methylated regions in both CpG and non-CpG regions were cluste red in intron regions,where the DNA methylation level was highest.The function of genes associated with differentially methylated regions in promoter regions was also investigated.From Gene Ontology analysis results,DNA methylation was implicated in a number of essential functional responses to spinal cord injury,including neuronal synaptic connection creation and axon regeneration.Notably,neither CpG methylation nor non-CpG methylation was implicated in the functional response of glial or inflammatory cells.In summary,our work elucidated the dynamic pattern of DNA methylation in the spinal co rd following injury and identified reduced nonCpG methylation as an epigenetic target after spinal cord injury in mice.展开更多
文摘Due to the dynamic stiffness characteristics of human joints, it is easy to cause impact and disturbance on normal movements during exoskeleton assistance. This not only brings strict requirements for exoskeleton control design, but also makes it difficult to improve assistive level. The Variable Stiffness Actuator (VSA), as a physical variable stiffness mechanism, has the characteristics of dynamic stiffness adjustment and high stiffness control bandwidth, which is in line with the stiffness matching experiment. However, there are still few works exploring the assistive human stiffness matching experiment based on VSA. Therefore, this paper designs a hip exoskeleton based on VSA actuator and studies CPG human motion phase recognition algorithm. Firstly, this paper puts forward the requirements of variable stiffness experimental design and the output torque and variable stiffness dynamic response standards based on human lower limb motion parameters. Plate springs are used as elastic elements to establish the mechanical principle of variable stiffness, and a small variable stiffness actuator is designed based on the plate spring. Then the corresponding theoretical dynamic model is established and analyzed. Starting from the CPG phase recognition algorithm, this paper uses perturbation theory to expand the first-order CPG unit, obtains the phase convergence equation and verifies the phase convergence when using hip joint angle as the input signal with the same frequency, and then expands the second-order CPG unit under the premise of circular limit cycle and analyzes the frequency convergence criterion. Afterwards, this paper extracts the plate spring modal from Abaqus and generates the neutral file of the flexible body model to import into Adams, and conducts torque-stiffness one-way loading and reciprocating loading experiments on the variable stiffness mechanism. After that, Simulink is used to verify the validity of the criterion. Finally, based on the above criterions, the signal mean value is removed using feedback structure to complete the phase recognition algorithm for the human hip joint angle signal, and the convergence is verified using actual human walking data on flat ground.
基金National Key Research and Development Program of China,No.2016YFA0100800(to LC)International(Regional)Cooperation and Communication Program of the National Natural Science Foundation of China,No.81820108013(to LC)+3 种基金State Key Program of the National Natural Science Foundation of China,No.81330030(to LC)National Natural Science Foundation of China,Nos.82071370(to ZW),81301042(to LC)Shanghai Pujiang Program,No.19PJ1409200(to ZW)Shanghai Sailing Program,No.21YF1442400(to CL)。
文摘DNA methylation is a critical epigenetic regulator in the occurrence and development of diseases and is closely related to various functional responses in relation to spinal cord injury.To investigate the role of DNA methylation in spinal cord injury,we constructed a library with reduced-representation bisulfite sequencing data obtained at various time points(day 0-42)after spinal cord injury in mice.Global DNA methylation levels,specifically non-CpG(CHG and CHH)methylation levels,decreased modestly following spinal cord injury.Stages post-spinal cord injury were classified as early(day 0-3),intermediate(day7-14),and late(day 28-42)based on similarity and hie rarchical cluste ring of global DNA methylation patterns.The non-CpG methylation level,which included CHG and CHH methylation levels,was markedly reduced despite accounting for a minor proportion of total methylation abundance.At multiple genomic sites,including the 5’untranslated regions,promoter,exon,intron,and 3’untranslated regions,the non-CpG methylation level was markedly decreased following spinal cord injury,whereas the CpG methylation level remained unchanged at these locations.Approximately one-half of the differentially methylated regions were located in intergenic areas;the other differentially methylated regions in both CpG and non-CpG regions were cluste red in intron regions,where the DNA methylation level was highest.The function of genes associated with differentially methylated regions in promoter regions was also investigated.From Gene Ontology analysis results,DNA methylation was implicated in a number of essential functional responses to spinal cord injury,including neuronal synaptic connection creation and axon regeneration.Notably,neither CpG methylation nor non-CpG methylation was implicated in the functional response of glial or inflammatory cells.In summary,our work elucidated the dynamic pattern of DNA methylation in the spinal co rd following injury and identified reduced nonCpG methylation as an epigenetic target after spinal cord injury in mice.
