Cable-driven ankle–foot exoskeletons have attracted numerous researchers over the previous decade.The assistive forces of most exoskeletons pulled the back bottom of the shoes,across talocrural and subtalar joints.Th...Cable-driven ankle–foot exoskeletons have attracted numerous researchers over the previous decade.The assistive forces of most exoskeletons pulled the back bottom of the shoes,across talocrural and subtalar joints.The talocrural joint is inherently mediolateral unstable at the plantarflexion position due to its sliding mortise structure,while the subtalar joint allows inversion/eversion.In this paper,a biologically inspired cross-type double-cable-driven ankle–foot exotendon was proposed to assist not only the plantarflexion moment but also the movement stability.The novel structure was bio-inspired by the behind-calf anatomically symmetric layout and under-foot cross-configuration of the ankle–foot muscles.To examine the combined functions,we conducted a forward pelvis perturbed standing experiment on five subjects without and with exotendon assistance and recorded the biomechanical data.Compared to the unpowered condition,the biological ankle plantarflexion moment was reduced by 39 with 0.1 Nm/kg exotendon assistance for one leg.Besides,the forward margin of stability was increased by 17 during the late perturbation period,which indicated the improvement of balance in the sagittal plane.In addition,the standard deviation of the lateral CoP and three-dimensional marker trajectories for the ankle condylar and heel all descended,which provided evidence for ankle–foot stability improvement.The results suggested that the proposed biological exotendon can provide the compound ankle–foot assistance,reducing plantarflexion moment and improving movement stability.展开更多
Energetic electron measurement is of great significance to theoretical space physics research and space weather applications.Current energetic electron detectors must cooperate with a spin-stabilized satellite platfor...Energetic electron measurement is of great significance to theoretical space physics research and space weather applications.Current energetic electron detectors must cooperate with a spin-stabilized satellite platform to achieve high angular resolution in pitch angle distribution and three-dimensional(3D)imaging measurement of energetic electrons.This article introduces a cross-type quasi-3D imaging electron spectrometer(IES)based on pinhole imaging technology developed in the laboratory.The imager is composed of five imaging units,including a nine-pixel area array Si-PIN detector imaging unit in the middle and four three-pixel linear array Si-PIN detector imaging units placed in a cross-shape around it.The combination of five imaging units forms two orthogonal nine-pixel linear array detectors(with a common pixel in the middle).There are four pixels with a view angle of 20°×20°in the 45°oblique directions of the cross-type detection array.There are 21 imaging pixels in the entire crosstype sensor head,corresponding to 21 directions.Two multichannel integrated preamplifier ASICs are integrated in the sensor head to realize particle signal readout from 21 pixels.With a back-end electronics system,each pixel can achieve high energy resolution detection of 50–600 keV electrons.Radioactive sources and electron accelerators are used to calibrate the cross-type imaging sensor head,and the results demonstrate its good energy and directional detection characteristics(the energy resolution reaches 6.9 keV for the incident 200 keV electron beam).We performed simulations on the imaging sensor head’s ability to measure the electron pitch angle distribution on the three-axis stabilized platform,and the results show that the sensor head can perform quasi-three-dimensional detection of electrons incident within 2πsolid angles on the three-axis stabilized satellite platform,with an average angular resolution of the electron pitch angle distribution of less than 6°.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.U21A20121,Grant No.52027806)。
文摘Cable-driven ankle–foot exoskeletons have attracted numerous researchers over the previous decade.The assistive forces of most exoskeletons pulled the back bottom of the shoes,across talocrural and subtalar joints.The talocrural joint is inherently mediolateral unstable at the plantarflexion position due to its sliding mortise structure,while the subtalar joint allows inversion/eversion.In this paper,a biologically inspired cross-type double-cable-driven ankle–foot exotendon was proposed to assist not only the plantarflexion moment but also the movement stability.The novel structure was bio-inspired by the behind-calf anatomically symmetric layout and under-foot cross-configuration of the ankle–foot muscles.To examine the combined functions,we conducted a forward pelvis perturbed standing experiment on five subjects without and with exotendon assistance and recorded the biomechanical data.Compared to the unpowered condition,the biological ankle plantarflexion moment was reduced by 39 with 0.1 Nm/kg exotendon assistance for one leg.Besides,the forward margin of stability was increased by 17 during the late perturbation period,which indicated the improvement of balance in the sagittal plane.In addition,the standard deviation of the lateral CoP and three-dimensional marker trajectories for the ankle condylar and heel all descended,which provided evidence for ankle–foot stability improvement.The results suggested that the proposed biological exotendon can provide the compound ankle–foot assistance,reducing plantarflexion moment and improving movement stability.
基金supported by the National Natural Science Foundation of China(Grant Nos.42274225,41374167 and 41674175)。
文摘Energetic electron measurement is of great significance to theoretical space physics research and space weather applications.Current energetic electron detectors must cooperate with a spin-stabilized satellite platform to achieve high angular resolution in pitch angle distribution and three-dimensional(3D)imaging measurement of energetic electrons.This article introduces a cross-type quasi-3D imaging electron spectrometer(IES)based on pinhole imaging technology developed in the laboratory.The imager is composed of five imaging units,including a nine-pixel area array Si-PIN detector imaging unit in the middle and four three-pixel linear array Si-PIN detector imaging units placed in a cross-shape around it.The combination of five imaging units forms two orthogonal nine-pixel linear array detectors(with a common pixel in the middle).There are four pixels with a view angle of 20°×20°in the 45°oblique directions of the cross-type detection array.There are 21 imaging pixels in the entire crosstype sensor head,corresponding to 21 directions.Two multichannel integrated preamplifier ASICs are integrated in the sensor head to realize particle signal readout from 21 pixels.With a back-end electronics system,each pixel can achieve high energy resolution detection of 50–600 keV electrons.Radioactive sources and electron accelerators are used to calibrate the cross-type imaging sensor head,and the results demonstrate its good energy and directional detection characteristics(the energy resolution reaches 6.9 keV for the incident 200 keV electron beam).We performed simulations on the imaging sensor head’s ability to measure the electron pitch angle distribution on the three-axis stabilized platform,and the results show that the sensor head can perform quasi-three-dimensional detection of electrons incident within 2πsolid angles on the three-axis stabilized satellite platform,with an average angular resolution of the electron pitch angle distribution of less than 6°.
