Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acce...Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acceleration and jerk of the vehicle in order to improve passenger comfort.However,naturalistic driving studies demonstrate that such simple characteristics are insufficient for accurately evaluating passenger comfort.This study identifies motion complexity as a key factor of passenger comfort.A series of naturalistic driving studies are conducted,during which passenger comfort is assessed using a 5-point Likert scale.Moreover,a real-time passenger comfort measurement based on electromyography(EMG)and stepwise regression is proposed to facilitate seamless data collection.Time-series features representing motion complexity are then introduced to better describe passenger comfort.Hierarchical regression confirms that simple characteristics of motion are insufficient to explain passenger comfort,and shows that the proposed motion complexity features have a substantial effect on passenger comfort.Finally,a machine learning-based real-time passenger comfort estimation method is developed according to the foregoing findings.Experimental results show that the proposed method can accurately estimate passenger comfort in real-time using only vehicle motion information.The findings of this study suggest that vehicle motion complexity should be considered in future passenger comfort studies.展开更多
For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,...For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,a distributed ISAR imaging algorithm is proposed to improve the cross-range resolution for the ship target.Multiple stations are used to observe the target in a short time,thereby the effect of incoherence caused by the complex motion of the ship can be reduced.The signal model of ship target with three-dimensional(3-D)rotation is constructed firstly.Then detailed analysis about the improvement of crossrange resolution is presented.Afterward,we propose the methods of parameters estimation to solve the problem of the overlap or gap,which will cause a loss of resolution and is necessary for subsequent processing.Besides,the compressed sensing(CS)method is applied to reconstruct the echoes with gaps.Finally,numerical simulations are presented to verify the effectiveness and the robustness of the proposed algorithm.展开更多
Flexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications.Although considerable efforts have been made to construct anisotropic ...Flexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications.Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities,existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity.Here,an ultrasensitive,highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers.The bilayer sensor consists of an aligned carbon nanotube(CNT)array assembled on top of a periodically wrinkled and cracked CNT-graphene oxide film.The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched,leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100%strain.The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3,to the benefit of accurate detection of loading directions by the multidirectional sensor.This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity,selectivity,and stretchability,demonstrating promising applications in full-range,multi-axis human motion detection for wearable electronics and smart robotics.展开更多
Digitization precision analysis is an important tool to ensure the design precision of machine tool currently. The correlative research about precision modeling and analysis mainly focuses on the geometry precision an...Digitization precision analysis is an important tool to ensure the design precision of machine tool currently. The correlative research about precision modeling and analysis mainly focuses on the geometry precision and motion precision of machine tool, and the forming motion precision of workpiece surface. For the machine tool with complex forming motion, there is not accurate corresponding relationship between the existing criterion on precision design and the machining precision of workpiece. Therefore, a design scheme on machine tool precision based on error prediction is proposed, which is divided into two-stage digitization precision analysis crucially. The first stage aims at the technology system to complete the precision distribution and inspection from the workpiece to various component parts of technology system and achieve the total output precision of machine tool under the specified machining precision; the second stage aims at the machine tool system to complete the precision distribution and inspection from the output precision of machine tool to the machine tool components. This article serves YK3610 gear hobber as the example to describe the error model of two systems and basic application method, and the practical cutting precision of this machine tool achieves to 5-4-4 grade. The proposed method can provide reliable guidance to the precision design of machine tool with complex forming motion.展开更多
In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, an...In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, and different complex impact-sliding motions exist on the tribology surfaces. In this study, an impact-sliding wear test rig is developed to investigate the wear effect of different complex motions. Using this rig, multi-type impact-sliding wear effects are realized and measured, such as those derived from unidirectional, reciprocating, and multi-mode combination motions. These three types of impact–sliding wear running behavior are tested and the wear damage mechanism is discussed.展开更多
High-performance wearable sensors that detect complex,multidimensional signals are indispensable in practical applica-tions.Most existing sensors can only detect axial deformations or single stimuli,dramatically limit...High-performance wearable sensors that detect complex,multidimensional signals are indispensable in practical applica-tions.Most existing sensors can only detect axial deformations or single stimuli,dramatically limiting their application fields.In this study,anisotropic strain and deformation-insensitive pressure sensors were effectively constructed based on a rigid-flexible synergistic stretchable substrate.Furthermore,we developed a three-dimensional integrated sensor with highly directional selective sensing through reasonable design and assembly.This integrated sensor recognizes the amplitude and direction of strain in the plane with a maximum gauge factor of 635 and an unprecedented selectivity of 13.99.Additionally,this device can also monitor the pressure outside the plane with a sensitivity of 0.277 kPa^(-1).We further investigated the working mechanism of sensor anisotropy and confirmed the application of the sensor in detecting complex multifreedom human joint movements.This research discovery provides new ideas and methods for developing multidimensional sensors,which is essential for broadening the application field of wearable electronic products.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52221005)Tsinghua-Toyota Joint Research Fund.
文摘Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acceleration and jerk of the vehicle in order to improve passenger comfort.However,naturalistic driving studies demonstrate that such simple characteristics are insufficient for accurately evaluating passenger comfort.This study identifies motion complexity as a key factor of passenger comfort.A series of naturalistic driving studies are conducted,during which passenger comfort is assessed using a 5-point Likert scale.Moreover,a real-time passenger comfort measurement based on electromyography(EMG)and stepwise regression is proposed to facilitate seamless data collection.Time-series features representing motion complexity are then introduced to better describe passenger comfort.Hierarchical regression confirms that simple characteristics of motion are insufficient to explain passenger comfort,and shows that the proposed motion complexity features have a substantial effect on passenger comfort.Finally,a machine learning-based real-time passenger comfort estimation method is developed according to the foregoing findings.Experimental results show that the proposed method can accurately estimate passenger comfort in real-time using only vehicle motion information.The findings of this study suggest that vehicle motion complexity should be considered in future passenger comfort studies.
基金supported by the National Natural Science Foundation of China(61871146)the Fundamental Research Funds for the Central Universities(FRFCU5710093720)。
文摘For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,a distributed ISAR imaging algorithm is proposed to improve the cross-range resolution for the ship target.Multiple stations are used to observe the target in a short time,thereby the effect of incoherence caused by the complex motion of the ship can be reduced.The signal model of ship target with three-dimensional(3-D)rotation is constructed firstly.Then detailed analysis about the improvement of crossrange resolution is presented.Afterward,we propose the methods of parameters estimation to solve the problem of the overlap or gap,which will cause a loss of resolution and is necessary for subsequent processing.Besides,the compressed sensing(CS)method is applied to reconstruct the echoes with gaps.Finally,numerical simulations are presented to verify the effectiveness and the robustness of the proposed algorithm.
基金This project was financially supported by the Research Grants Council(GRF Projects:16229216,16209917,16205517)the Innovation and Technology Commission(ITS/012/19)of Hong Kong SAR.
文摘Flexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications.Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities,existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity.Here,an ultrasensitive,highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers.The bilayer sensor consists of an aligned carbon nanotube(CNT)array assembled on top of a periodically wrinkled and cracked CNT-graphene oxide film.The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched,leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100%strain.The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3,to the benefit of accurate detection of loading directions by the multidirectional sensor.This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity,selectivity,and stretchability,demonstrating promising applications in full-range,multi-axis human motion detection for wearable electronics and smart robotics.
基金supported by National Natural Science Foundation of China (Grant No. 51075419)Chongqing Municipal Natural Science Foundation of China (Grant No. CSTC,2009BB3234)
文摘Digitization precision analysis is an important tool to ensure the design precision of machine tool currently. The correlative research about precision modeling and analysis mainly focuses on the geometry precision and motion precision of machine tool, and the forming motion precision of workpiece surface. For the machine tool with complex forming motion, there is not accurate corresponding relationship between the existing criterion on precision design and the machining precision of workpiece. Therefore, a design scheme on machine tool precision based on error prediction is proposed, which is divided into two-stage digitization precision analysis crucially. The first stage aims at the technology system to complete the precision distribution and inspection from the workpiece to various component parts of technology system and achieve the total output precision of machine tool under the specified machining precision; the second stage aims at the machine tool system to complete the precision distribution and inspection from the output precision of machine tool to the machine tool components. This article serves YK3610 gear hobber as the example to describe the error model of two systems and basic application method, and the practical cutting precision of this machine tool achieves to 5-4-4 grade. The proposed method can provide reliable guidance to the precision design of machine tool with complex forming motion.
基金supported by the National Natural Science Foundation of China (Nos.51375407,U1530136,and 51627806)the Young Scientific Innovation Team of Science and Technology of Sichuan (No.2017TD0017)
文摘In many industrial devices, impact-sliding wear is caused by a variety of complex vibrations between the contacted interfaces. Under actual conditions, impact and sliding motions do not occur in only one direction, and different complex impact-sliding motions exist on the tribology surfaces. In this study, an impact-sliding wear test rig is developed to investigate the wear effect of different complex motions. Using this rig, multi-type impact-sliding wear effects are realized and measured, such as those derived from unidirectional, reciprocating, and multi-mode combination motions. These three types of impact–sliding wear running behavior are tested and the wear damage mechanism is discussed.
基金Anhui Province Science and Technology Major Project(no.202203A07020022).
文摘High-performance wearable sensors that detect complex,multidimensional signals are indispensable in practical applica-tions.Most existing sensors can only detect axial deformations or single stimuli,dramatically limiting their application fields.In this study,anisotropic strain and deformation-insensitive pressure sensors were effectively constructed based on a rigid-flexible synergistic stretchable substrate.Furthermore,we developed a three-dimensional integrated sensor with highly directional selective sensing through reasonable design and assembly.This integrated sensor recognizes the amplitude and direction of strain in the plane with a maximum gauge factor of 635 and an unprecedented selectivity of 13.99.Additionally,this device can also monitor the pressure outside the plane with a sensitivity of 0.277 kPa^(-1).We further investigated the working mechanism of sensor anisotropy and confirmed the application of the sensor in detecting complex multifreedom human joint movements.This research discovery provides new ideas and methods for developing multidimensional sensors,which is essential for broadening the application field of wearable electronic products.
