This paper proposes a trajectory tracking control scheme for vertical/short take-off and landing(V/STOL)vehicles.Owing to their high number of controllable degrees of freedom and strong nonlinearity,the design of flig...This paper proposes a trajectory tracking control scheme for vertical/short take-off and landing(V/STOL)vehicles.Owing to their high number of controllable degrees of freedom and strong nonlinearity,the design of flight control systems for such vehicles presents considerable challenges,particularly in developing controllers capable of accurately tracking specified trajectories.Building on existing control strategies for various vehicle types,this study introduces an extended control framework tailored for V/STOL systems.The proposed scheme consists of two nested loops:an outer position control loop and an inner attitude control loop.The position loop employs a proportional-integral-derivative(PID)control algorithm,whereas the attitude loop utilizes an anti-saturation integral sliding mode control algorithm.This approach effectively alleviates the integral oversaturation issue inherent in conventional sliding mode methods and suppresses buffeting through a boundary layer technique.Simulation results demonstrate the efficacy of the proposed control strategy.展开更多
In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical f...In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical formula on the basis of estimations. Next, we design a scheme for evaluating the transfer alignment on a moving base, for which the attitude error cannot be directly measured. Then, we build a mathematic estimation model and discuss Fixed Point Smoothing(FPS), Returns to Scale(RTS), Inverted Sequence Recursive Estimation(ISRE), and Kalman filter estimation methods, which can be used when evaluating alignment accuracy. Our theoretical calculations and simulated analyses show that the DOA reflects not only the alignment time and accuracy but also differences in the maneuver schemes, and is suitable for use as an integrated evaluation index. Furthermore, all four of these algorithms can be used to identify the transfer alignment and evaluate its accuracy. We recommend RTS in particular for engineering applications. Generalized DOAs should be calculated according to the tactical requirements.展开更多
Earth sensors are widely used in spacecraft for attitude determination. They need to have a very large field of view(FOV)( > 120°) and relatively low accuracy while being used in the aircrafts around orbit. A ...Earth sensors are widely used in spacecraft for attitude determination. They need to have a very large field of view(FOV)( > 120°) and relatively low accuracy while being used in the aircrafts around orbit. A triple-FOV infrared earth sensor is proposed in this paper. It uses three pieces of standard infrared detectors with a wavelength range of 14;16μm,to sense the horizontal circle by detecting the infrared light emitted from the earth. From which,the geocentric vector can be obtained. A mathematic model is established and a validation model is set up to provide input parameters for the mathematic model. The simulation results of the two models show that the output of the mathematic model coincides with the known parameters. Based on the above analysis,a prototype has been built and tested. The test results show that the angle measurement error is about 0. 002° and hence such a triple-FOV earth sensor is capable to provide high-precision position information for autonomous navigation.展开更多
Birefringence-Zeeman dual frequency lasers are capable of producing frequency difference from several kilohertz to hundreds of megahertz, but the precision of giving and stabilizing of the beat frequency still needs i...Birefringence-Zeeman dual frequency lasers are capable of producing frequency difference from several kilohertz to hundreds of megahertz, but the precision of giving and stabilizing of the beat frequency still needs improvement to the range of ±200 kHz. We design a new elastic force-exerting device comprised of the bottom part, two arms and two pieces of force-exerting sheets. The frequency difference smoothly tuning is realized with this device in a large range of 2 MHz to 20 MHz. Power-balance frequency stabilization system is used to investigate characters of the temperature, frequency difference and laser power. The precision of the frequency difference has reach up to ±100 kHz after system temperature balance. Analyses of the laser frequency difference and power character are carried out.展开更多
Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the ...Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.展开更多
The study of BiFeO_(3)-0.3BaTiO_(3) ceramics has gained significant attention due to their high Curie temperature(TC≥450℃)and excellent piezoelectric properties(d33≥200 pC·N^(−1)).These are particularly pronou...The study of BiFeO_(3)-0.3BaTiO_(3) ceramics has gained significant attention due to their high Curie temperature(TC≥450℃)and excellent piezoelectric properties(d33≥200 pC·N^(−1)).These are particularly pronounced near the morphotropic phase boundary(MPB)region where coexisting rhombohedral and pseudocubic(R-PC)phases are observed.In addition,as the BaTiO_(3) content increases,BiFeO_(3)-BaTiO_(3) ceramics gradually become dominated by a single pseudocubic(PC-)phase.This shift results in a decrease in piezoelectric properties but an enhancement in strain performance.However,the underlying mechanism remains unclear.The high strain properties observed in non-MPB compositions provide a motivation for further investigation into these mechanisms.This paper presents a detailed analysis of the electric-field and temperature-induced domain structure evolution in BiFeO_(3)-0.4BaTiO_(3),which is predominately characterized by the PC phase.Piezoresponse force microscope(PFM)observations reveal the presence of nanodomains and stripy domains associated with polar nanoregions(PNRs),as well as relaxor ferroelectrics(RFEs)and/or ferroelectrics(FEs).The RFEs exhibit a significantly better strain response than the FEs,providing direct evidence for the enhanced strain properties of RFEs.Elevated-temperature Raman spectroscopy confirms a decrease in B-O bonding and BO6 deformation,along with an increase in structural symmetry,indicating the formation of RFEs and/or PNRs.The phase diagram shows the Burns temperature(TB),dielectric maxima temperature(Tm)and freezing temperature(Tf)evaluated from the dielectric spectra;the temperature-induced evolution of domain structures;and the sequential quasi-dielectric states:PNRs,RFEs and FEs.The evolution of the domain structure,including the morphology and ratio of FEs,RFEs and PNRs,induced by either electric-fields or temperature strongly affects the strain properties of RFEs.A superior piezoelectric coefficient of d33*=533 pm·V^(−1) at 40 kV·cm^(−1) and a large electric strain of Suni=0.285%are obtained.These results further validate that domain modulation can effectively enhance the strain properties of BiFeO_(3)-BaTiO_(3) ceramics,which makes them promising candidates for actuator applications.展开更多
Lipidomics is an emerging discipline that systematically studies the various types,functions,and metabolic pathways of lipids within living organisms.This field compares changes in diseases or drug impact,identifying ...Lipidomics is an emerging discipline that systematically studies the various types,functions,and metabolic pathways of lipids within living organisms.This field compares changes in diseases or drug impact,identifying biomarkers and molecular mechanisms present in lipid metabolic networks across different physiological or pathological states.Through employing analytical chemistry within the realm of lipidomics,researchers analyze traditional Chinese medicine(TCM).This analysis aids in uncovering potential mechanisms for treating diverse physiopathological conditions,assessing drug efficacy,understanding mechanisms of action and toxicity,and generating innovative ideas for disease prevention and treatment.This manuscript assesses recent literature,summarizing existing lipidomics technologies and their applications in TCM research.It delineates the efficacy,mechanisms,and toxicity research related to lipidomics in Chinese medicine.Additionally,it explores the utilization of lipidomics in quality control research for Chinese medicine,aiming to expand the application of lipidomics within this field.Ultimately,this initiative seeks to foster the integration of traditional medicine theory with modern science and technology,promoting an organic fusion between the two domains.展开更多
Waveguide quantum electrodynamics(QED)system manifests an ideal platform for studying many-body physics.When multiple emitters are coupled to a common waveguide,subradiant states may arise because of the waveguide-med...Waveguide quantum electrodynamics(QED)system manifests an ideal platform for studying many-body physics.When multiple emitters are coupled to a common waveguide,subradiant states may arise because of the waveguide-mediated interaction,leading to a long lifetime because of their immunity to the waveguide modeinduced dissipation.However,they can still be influenced by local environments,which are incoherent for different emitters and cannot be canceled out through interference.Herein,a new mechanism termed energy quantum confinement effect(EQCE)is proposed in a non-Markovian waveguide QED system to suppress the local dissipation.The energy quantum is confined in the waveguide by emitters,suppressing spontaneous decay of the emitters.The EQCE makes the system partly free from local dissipation of emitters,leading to a total decay rate lower than the local decay rate.We further show that similar effect occurs spontaneously by self-interference and can be stressed by cooperative coupling,relaxing the requirement for initializing the emitters into a remotely entangled state.展开更多
Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of thes...Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of these two Sr OLCs,a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus.Two commercial optical frequency combs(OFCs)with adapted single-branch 698/1542nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser.The fractional instability of the comparison yields 3.1×10^(−17)at 10000 s averaging time.The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2)×10^(−17),which is within their claimed uncertainties.This result demonstrates the consistency of their frequencies when they serve as optical frequency standards.Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.展开更多
Efficient exciton transport over long distances is crucial for organic optoelectronics.Despite efforts to improve the transport properties of organic semiconductors,the limited exciton diffusion remains a significant ...Efficient exciton transport over long distances is crucial for organic optoelectronics.Despite efforts to improve the transport properties of organic semiconductors,the limited exciton diffusion remains a significant obstacle for light-harvesting applications.In this study,we observe phenomena where exciton transport is significantly enhanced by light irradiation in the organic molecular crystal of 2,2'-(2,5-bis(2,2-diphenylvinyl)-1,4-phenylene)dinaphthalene(BDVPN).The exciton transport in this material is improved,as evidenced by the increased diffusion coefficient from 10^(−3) cm^(2)·s^(−1) to over 1 cm^(2)·s^(−1) and a prolonged diffusion length from less than 50 nm to nearly 700 nm characterized by time-resolved photoluminescence microscopy(TPLM).Additionally,we confirmed the enhancement of charge transport capability under irradiation as additional evidence of improved transport properties of the material.These intriguing phenomena may be associated with the material’s twisted molecular conformation and rotatable single bonds,which facilitate light-induced structural alterations conducive to efficient transport properties.Our work provides a novel insight into developing organic semiconductors with efficient exciton transport.展开更多
War rehearsals have become increasingly important in national security due to the growing complexity of international affairs.However,traditional rehearsal methods,such as military chess simulations,are inefficient an...War rehearsals have become increasingly important in national security due to the growing complexity of international affairs.However,traditional rehearsal methods,such as military chess simulations,are inefficient and inflexible,with particularly pronounced limitations in command and decision-making.The overwhelming volume of information and high decision complexity hinder the realization of autonomous and agile command and control.To address this challenge,an intelligent warfare simulation framework named Command-Agent is proposed,which deeply integrates large language models(LLMs)with digital twin battlefields.By constructing a highly realistic battlefield environment through real-time simulation and multi-source data fusion,the natural language interaction capabilities of LLMs are leveraged to lower the command threshold and to enable autonomous command through the Observe-Orient-Decide-Act(OODA)feedback loop.Within the Command-Agent framework,a multimodel collaborative architecture is further adopted to decouple the decision-generation and command-execution functions of LLMs.By combining specialized models such as Deep Seek-R1 and MCTool,the limitations of single-model capabilities are overcome.MCTool is a lightweight execution model fine-tuned for military Function Calling tasks.The framework also introduces a Vector Knowledge Base to mitigate hallucinations commonly exhibited by LLMs.Experimental results demonstrate that Command-Agent not only enables natural language-driven simulation and control but also deeply understands commander intent.Leveraging the multi-model collaborative architecture,during red-blue UAV confrontations involving 2 to 8 UAVs,the integrated score is improved by an average of 41.8%compared to the single-agent system(MCTool),accompanied by a 161.8%optimization in the battle loss ratio.Furthermore,when compared with multi-agent systems lacking the knowledge base,the inclusion of the Vector Knowledge Base further improves overall performance by 16.8%.In comparison with the general model(Qwen2.5-7B),the fine-tuned MCTool leads by 5%in execution efficiency.Therefore,the proposed Command-Agent introduces a novel perspective to the military command system and offers a feasible solution for intelligent battlefield decision-making.展开更多
With the convergence of sensor technology,artificial intelligence,and the Internet of Things,intelligent vibration monitoring systems are undergoing transformative development.This evolution imposes stringent demands ...With the convergence of sensor technology,artificial intelligence,and the Internet of Things,intelligent vibration monitoring systems are undergoing transformative development.This evolution imposes stringent demands on the miniaturization,low power consumption,high integration,and environmental adaptability of transducers.Graphene,renowned for its superlative physicochemical attributes,holds significant promise for application in micro-and nanoelectromechanical systems(M/NEMS).However,the inherent central symmetry of graphene restricts its utility in piezoelectric devices.Inspired by the sensilla trichoidea of spiders,a threedimensional(3D)cilia-like monolayer graphene omnidirectional vibration transducer(CGVT)based on a stress-induced self-assembly mechanism is fabricated,demonstrating notable performance and high-temperature resistance.Furthermore,3D vibration vector decoding is realized via an omnidirectional decoupling algorithm based on one-dimensional convolutional neural networks(1DCNN)to achieve precise discrimination of vibration directions.The 3D bionic vibration-sensing system incorporates a spider web structure into a bionic cilia MEMS chip through a gold wire bonding process,enabling the realization of three distinct mechanisms for vibration detection and recognition.In particular,these devices are manufactured using silicon-based semiconductor processing techniques and MEMS fabrication methodologies,leading to a substantial reduction in the dimensions of individual components compared to traditional counterparts.展开更多
A Stewart platform is introduced in thc 500 m aperture spherical radio telescope（FAST） as an accuracy adjustable mechanism for teed receivers. Accuracy analysis is the basis of accuracy design. However, a rapid and ...A Stewart platform is introduced in thc 500 m aperture spherical radio telescope（FAST） as an accuracy adjustable mechanism for teed receivers. Accuracy analysis is the basis of accuracy design. However, a rapid and effective accuracy analysis method for parallel manipulator is still needed. In order to enhance solution efficiency, an interval analysis method（lA method） is introduced to solve the terminal error bound of the Stewart platform with detailed solution path. Taking a terminal pose of the Stewart platform in FAST as an example, the terminal error is solved by the Monte Carlo method（MC method） by 4 980 s, the stochastic mathematical method（SM method） by 0.078 s, and the IA method by 2.203 s. Compared with MC method, the terminal error by SM method leads a 20% underestimate while the IA method can envelop the real error bound of the Stewart platform. This indicates that the IA method outperforms the other two methods by providing quick calculations and enveloping the real error bound of the Stewart platform. According to the given structural error of the dimension parameters of the Stewart platform, the IA method gives a maximum position error of 19.91 mm and maximum orientation error of 0.534°, which suggests that the IA method can be used for accuracy design of the Stewart platfbnn in FAST. The 1A method presented is a rapid and effective accuracy analysis method for Stewart platform.展开更多
Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method fo...Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method for engineering application is a very challenging issue, which should be further studied in the field. Grassmann line geometry, which can investigate the dimensions of spatial line-clusters in a concise way, is taken as the mathematic foundation. Atlas method is introduced to visually describe the degrees of freedom（DOFs） and constraints of a mechanism, and the dual rule is brought in to realize the mutual conversion of the freedom-space and constraint-space. Consequently, a systematic method based on Grassmann line geometry and Atlas method is generated and the entire type synthesis process is presented. Three type 4-DOF PKMs, i.e., 1T3R, 2T2R and 3T1R（T： translational DOF; R： rotational DOF）, are classified according to the different combinations of the translational DOFs and rotational DOFs. The type synthesis of 4-DOF PKMs is carried out and the possible configurations are thoroughly investigated. Some new PKMs with useful functions are generated during this procedure. The type synthesis method based on Grassmann line geometry and Atlas method is intuitive and concise, and can reduce the complexity of the PKMs＇ type synthesis. Moreover, this method can provide theoretical guidance for other PKMs＇ type synthesis and engineering application. A novel type synthesis method is proposed, which solves the existing methods＇ problems in terms of complicated, not intuitive and unsuitable for practical application.展开更多
Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)...Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)Tx(PVA/MXene)nanofibers film and monolayer molybdenum diselenide(MoSe2)piezoelectric nanogenerator(PENG)was reported for the first time.The monolayer MoSe_(2)-based PENG was fabricated by atmospheric pressure chemical vapor deposition techniques,which can generate a peak output of 35 mV and a power density of42 mW m^(-2).The flexible PENG integrated on polyethylene terephthalate(PET)substrate can harvest energy generated by different parts of human body and exhibit great application prospects in wearable devices.The electrospinned PVA/MXene nanofiber-based humidity sensor with flexible PET substrate under the driven of monolayer MoSe_(2) PENG,shows high response of~40,fast response/recovery time of 0.9/6.3 s,low hysteresis of 1.8%and excellent repeatability.The self-powered flexible humidity sensor yields the capability of detecting human skin moisture and ambient humidity.This work provides a pathway to explore the high-performance humidity sensor integrated with PENG for the self-powered flexible electronic devices.展开更多
A multiple-legged robot is traditionally controlled by using its dynamic model.But the dynamic-model-based approach fails to acquire satisfactory performances when the robot faces rough terrains and unknown environmen...A multiple-legged robot is traditionally controlled by using its dynamic model.But the dynamic-model-based approach fails to acquire satisfactory performances when the robot faces rough terrains and unknown environments.Referring animals＇ neural control mechanisms,a control model is built for a quadruped robot walking adaptively.The basic rhythmic motion of the robot is controlled by a well-designed rhythmic motion controller（RMC） comprising a central pattern generator（CPG） for hip joints and a rhythmic coupler（RC） for knee joints.CPG and RC have relationships of motion-mapping and rhythmic couple.Multiple sensory-motor models,abstracted from the neural reflexes of a cat,are employed.These reflex models are organized and thus interact with the CPG in three layers,to meet different requirements of complexity and response time to the tasks.On the basis of the RMC and layered biological reflexes,a quadruped robot is constructed,which can clear obstacles and walk uphill and downhill autonomously,and make a turn voluntarily in uncertain environments,interacting with the environment in a way similar to that of an animal.The paper provides a biologically inspired architecture,with which a robot can walk adaptively in uncertain environments in a simple and effective way,and achieve better performances.展开更多
Structural deformation monitoring of flight vehicles based on optical fiber sensing(OFS)technology has been a focus of research in the field of aerospace.After nearly 30 years of research and development,Chinese and i...Structural deformation monitoring of flight vehicles based on optical fiber sensing(OFS)technology has been a focus of research in the field of aerospace.After nearly 30 years of research and development,Chinese and international researchers have made significant advances in the areas of theory and methods,technology and systems,and ground experiments and flight tests.These advances have led to the development of OFS technology from the laboratory research stage to the engineering application stage.However,a few problems encountered in practical applications limit the wider application and further development of this technology,and thus urgently require solutions.This paper reviews the history of research on the deformation monitoring of flight vehicles.It examines various aspects of OFS-based deformation monitoring including the main varieties of OFS technology,technical advantages and disadvantages,suitability in aerospace applications,deformation reconstruction algorithms,and typical applications.This paper points out the key unresolved problems and the main evolution paradigms of engineering applications.It further discusses future development directions from the perspectives of an evolution paradigm,standardization,new materials,intelligentization,and collaboration.展开更多
The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and en...The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.展开更多
Inertia match of the parallel manipulator means the ratio of the inertial load of the parallel manipulator converted to each actuator shaft and the moment of inertia of the actuator is kept within a reasonable range.C...Inertia match of the parallel manipulator means the ratio of the inertial load of the parallel manipulator converted to each actuator shaft and the moment of inertia of the actuator is kept within a reasonable range.Currently there are many studies on parallel manipulators,but few mention inertia parameters and inertia match of parallel manipulators.This paper focuses on the inertia characteristics of the 3-RRR reconfigurable planar parallel manipulator.On the basis of the inverse dynamic formulations deduced with the principle of virtual work,the inertia matrix of the 3-RRR planar parallel manipulator in the actuator space is obtained in algebraic form.Then,by unifying the dimension and averaging diagonal elements of the inertia matrix,the equivalent inertia of the parallel manipulator,which is the inertial load of the parallel manipulator converted to each actuator shaft,is determined.By transforming the inertia problem of the 3-RRR parallel manipulator into that of the serial multi-bar manipulator,the practicality of the equivalent inertia deduced by inverse dynamics is demonstrated.According to the physical meaning of the inertia equation,the manipulator is divided in to three parts.Further analysis is carried out on the contribution of each part to the equivalent inertia and their distributions in the required workspace,revealing that the passive links cannot ignored in calculating the equivalent inertia of the parallel manipulator.Finally,the inertia match for the 3-RRR reconfigurable parallel manipulator under three configurations is accomplished,and reducers are selected.The equivalent inertia calculation and the inertial match results illustrate that the inertia math is a necessary step to the design of the parallel manipulator,and inertia parameters dramatically affect dynamic performances of parallel manipulators.Besides,the equivalent inertia and inertial match principles,proposed in the paper,can be widely applied in the dynamic analysis and servomotors selecting for the parallel manipulator.展开更多
Needle insertion is a common surgical procedure used in diagnosis and treatment.The needle steering technologies make continuous developments in theoretical and practical aspects along with the in-depth research on ne...Needle insertion is a common surgical procedure used in diagnosis and treatment.The needle steering technologies make continuous developments in theoretical and practical aspects along with the in-depth research on needle insertion.It is necessary to summarize and analyze the existing results to promote the future development of theories and applications of needle insertion.Thus,a survey of the state of the art of research is presented on algorithms of needle steering techniques,the surgical robots and devices.Based on the analysis of the needle insertion procedure,the concept of needle steering is defined as a kinematics problem,which is to place the needle at the target and avoid the obstacles.The needle steering techniques,including the artificial potential field method and the nonholonomic model,are introduced to control the needles for improving the accuracy.Based on the quasi-static thinking,the virtual spring model and the cantilever-beam model are developed to calculate the amount of needle deflection and generate the needle path.The phantoms instead of the real tissue are used to verify the models mentioned in most of the experimentations.For the desired needle trajectories,the image-guided robotic devices and some novel needles are presented to achieve the needle steering.Finally,the challenges are provided involving the controllability of the long flexible needle and the properties of soft tissue.The results and investigations can be used for further study on the precision and accuracy of needle insertion.展开更多
基金supported in part by National Key Laboratory Foundation(No.STSL2024-A-04(C))。
文摘This paper proposes a trajectory tracking control scheme for vertical/short take-off and landing(V/STOL)vehicles.Owing to their high number of controllable degrees of freedom and strong nonlinearity,the design of flight control systems for such vehicles presents considerable challenges,particularly in developing controllers capable of accurately tracking specified trajectories.Building on existing control strategies for various vehicle types,this study introduces an extended control framework tailored for V/STOL systems.The proposed scheme consists of two nested loops:an outer position control loop and an inner attitude control loop.The position loop employs a proportional-integral-derivative(PID)control algorithm,whereas the attitude loop utilizes an anti-saturation integral sliding mode control algorithm.This approach effectively alleviates the integral oversaturation issue inherent in conventional sliding mode methods and suppresses buffeting through a boundary layer technique.Simulation results demonstrate the efficacy of the proposed control strategy.
基金Supported by the National Natural Science Foundation of China （61633008）, the National Natural Science Foundation of China （61203225）, the Natural Science Foundation of Heilongjiang Province of China（QC2014C069）, the Special fund for the Central Universities （HEUCF160401）, and Provincial Postdoctoral Scientific Research Foundation （LBH-Q 15032）.
文摘In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical formula on the basis of estimations. Next, we design a scheme for evaluating the transfer alignment on a moving base, for which the attitude error cannot be directly measured. Then, we build a mathematic estimation model and discuss Fixed Point Smoothing(FPS), Returns to Scale(RTS), Inverted Sequence Recursive Estimation(ISRE), and Kalman filter estimation methods, which can be used when evaluating alignment accuracy. Our theoretical calculations and simulated analyses show that the DOA reflects not only the alignment time and accuracy but also differences in the maneuver schemes, and is suitable for use as an integrated evaluation index. Furthermore, all four of these algorithms can be used to identify the transfer alignment and evaluate its accuracy. We recommend RTS in particular for engineering applications. Generalized DOAs should be calculated according to the tactical requirements.
基金financially supported by the National High Technology Research and Development Program of China(863 Program)(No.2012AA121503 and No.2012AA120603)the National Natural Science Foundation of China(No.61377012)the Tsinghua University Initiative Scientific Research Program(No.20131089242)。
文摘Earth sensors are widely used in spacecraft for attitude determination. They need to have a very large field of view(FOV)( > 120°) and relatively low accuracy while being used in the aircrafts around orbit. A triple-FOV infrared earth sensor is proposed in this paper. It uses three pieces of standard infrared detectors with a wavelength range of 14;16μm,to sense the horizontal circle by detecting the infrared light emitted from the earth. From which,the geocentric vector can be obtained. A mathematic model is established and a validation model is set up to provide input parameters for the mathematic model. The simulation results of the two models show that the output of the mathematic model coincides with the known parameters. Based on the above analysis,a prototype has been built and tested. The test results show that the angle measurement error is about 0. 002° and hence such a triple-FOV earth sensor is capable to provide high-precision position information for autonomous navigation.
基金Supported by the National Natural Science Foundation of China under Grant No 50575110
文摘Birefringence-Zeeman dual frequency lasers are capable of producing frequency difference from several kilohertz to hundreds of megahertz, but the precision of giving and stabilizing of the beat frequency still needs improvement to the range of ±200 kHz. We design a new elastic force-exerting device comprised of the bottom part, two arms and two pieces of force-exerting sheets. The frequency difference smoothly tuning is realized with this device in a large range of 2 MHz to 20 MHz. Power-balance frequency stabilization system is used to investigate characters of the temperature, frequency difference and laser power. The precision of the frequency difference has reach up to ±100 kHz after system temperature balance. Analyses of the laser frequency difference and power character are carried out.
基金the funding provided by the National Helicopter Development Project of China。
文摘Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.
基金supported by the National Key Research and Development Program(No.2022YFB3807400)the National Natural Science Foundation of China(Nos.52072028 and 52032007).
文摘The study of BiFeO_(3)-0.3BaTiO_(3) ceramics has gained significant attention due to their high Curie temperature(TC≥450℃)and excellent piezoelectric properties(d33≥200 pC·N^(−1)).These are particularly pronounced near the morphotropic phase boundary(MPB)region where coexisting rhombohedral and pseudocubic(R-PC)phases are observed.In addition,as the BaTiO_(3) content increases,BiFeO_(3)-BaTiO_(3) ceramics gradually become dominated by a single pseudocubic(PC-)phase.This shift results in a decrease in piezoelectric properties but an enhancement in strain performance.However,the underlying mechanism remains unclear.The high strain properties observed in non-MPB compositions provide a motivation for further investigation into these mechanisms.This paper presents a detailed analysis of the electric-field and temperature-induced domain structure evolution in BiFeO_(3)-0.4BaTiO_(3),which is predominately characterized by the PC phase.Piezoresponse force microscope(PFM)observations reveal the presence of nanodomains and stripy domains associated with polar nanoregions(PNRs),as well as relaxor ferroelectrics(RFEs)and/or ferroelectrics(FEs).The RFEs exhibit a significantly better strain response than the FEs,providing direct evidence for the enhanced strain properties of RFEs.Elevated-temperature Raman spectroscopy confirms a decrease in B-O bonding and BO6 deformation,along with an increase in structural symmetry,indicating the formation of RFEs and/or PNRs.The phase diagram shows the Burns temperature(TB),dielectric maxima temperature(Tm)and freezing temperature(Tf)evaluated from the dielectric spectra;the temperature-induced evolution of domain structures;and the sequential quasi-dielectric states:PNRs,RFEs and FEs.The evolution of the domain structure,including the morphology and ratio of FEs,RFEs and PNRs,induced by either electric-fields or temperature strongly affects the strain properties of RFEs.A superior piezoelectric coefficient of d33*=533 pm·V^(−1) at 40 kV·cm^(−1) and a large electric strain of Suni=0.285%are obtained.These results further validate that domain modulation can effectively enhance the strain properties of BiFeO_(3)-BaTiO_(3) ceramics,which makes them promising candidates for actuator applications.
基金funded by the Sanming Project of Medicine in Shenzhen,China(Grant No.:SZZYSM202106004)the National Natural Science Foundation of China(Grant No.:82272960)+1 种基金the Shenzhen Science and Technology Innovation Commission,China(Grant No.:JCYJ20210324142012033)the Scientific Research Project of Guangdong Provincial Bureau of Traditional Chinese Medicine,China(Grant No.:20252037).
文摘Lipidomics is an emerging discipline that systematically studies the various types,functions,and metabolic pathways of lipids within living organisms.This field compares changes in diseases or drug impact,identifying biomarkers and molecular mechanisms present in lipid metabolic networks across different physiological or pathological states.Through employing analytical chemistry within the realm of lipidomics,researchers analyze traditional Chinese medicine(TCM).This analysis aids in uncovering potential mechanisms for treating diverse physiopathological conditions,assessing drug efficacy,understanding mechanisms of action and toxicity,and generating innovative ideas for disease prevention and treatment.This manuscript assesses recent literature,summarizing existing lipidomics technologies and their applications in TCM research.It delineates the efficacy,mechanisms,and toxicity research related to lipidomics in Chinese medicine.Additionally,it explores the utilization of lipidomics in quality control research for Chinese medicine,aiming to expand the application of lipidomics within this field.Ultimately,this initiative seeks to foster the integration of traditional medicine theory with modern science and technology,promoting an organic fusion between the two domains.
基金support from the National Key Research and Development Program of China(grant 2020YFA0715000)the National Natural Science Foundation of China(grant 62075111)+2 种基金the Tsinghua University Initiative Scientific Research ProgramH.-B.S.acknowledges support from the National Natural Science Foundation of China(grant 61960206003)Tsinghua-Foshan Innovation Special Fund(grant 2021THFS0102).
文摘Waveguide quantum electrodynamics(QED)system manifests an ideal platform for studying many-body physics.When multiple emitters are coupled to a common waveguide,subradiant states may arise because of the waveguide-mediated interaction,leading to a long lifetime because of their immunity to the waveguide modeinduced dissipation.However,they can still be influenced by local environments,which are incoherent for different emitters and cannot be canceled out through interference.Herein,a new mechanism termed energy quantum confinement effect(EQCE)is proposed in a non-Markovian waveguide QED system to suppress the local dissipation.The energy quantum is confined in the waveguide by emitters,suppressing spontaneous decay of the emitters.The EQCE makes the system partly free from local dissipation of emitters,leading to a total decay rate lower than the local decay rate.We further show that similar effect occurs spontaneously by self-interference and can be stressed by cooperative coupling,relaxing the requirement for initializing the emitters into a remotely entangled state.
基金supported by the National Key R&D Program of China(Grant No.2021YFF0603802)the National Natural Science Foundation of China(Grant No.61905231)+1 种基金the State Administration for Market Regulation(Grant No.CXTD202301)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300902)。
文摘Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of these two Sr OLCs,a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus.Two commercial optical frequency combs(OFCs)with adapted single-branch 698/1542nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser.The fractional instability of the comparison yields 3.1×10^(−17)at 10000 s averaging time.The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2)×10^(−17),which is within their claimed uncertainties.This result demonstrates the consistency of their frequencies when they serve as optical frequency standards.Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.
基金the National Natural Science Foundation of China(No.62075115,62335013,22275065,52073116)the National Key R&D Program of China(No.2022YFB4600400)the Natural Science Foundation of Jilin Province(20240101003JJ)for their financial support.
文摘Efficient exciton transport over long distances is crucial for organic optoelectronics.Despite efforts to improve the transport properties of organic semiconductors,the limited exciton diffusion remains a significant obstacle for light-harvesting applications.In this study,we observe phenomena where exciton transport is significantly enhanced by light irradiation in the organic molecular crystal of 2,2'-(2,5-bis(2,2-diphenylvinyl)-1,4-phenylene)dinaphthalene(BDVPN).The exciton transport in this material is improved,as evidenced by the increased diffusion coefficient from 10^(−3) cm^(2)·s^(−1) to over 1 cm^(2)·s^(−1) and a prolonged diffusion length from less than 50 nm to nearly 700 nm characterized by time-resolved photoluminescence microscopy(TPLM).Additionally,we confirmed the enhancement of charge transport capability under irradiation as additional evidence of improved transport properties of the material.These intriguing phenomena may be associated with the material’s twisted molecular conformation and rotatable single bonds,which facilitate light-induced structural alterations conducive to efficient transport properties.Our work provides a novel insight into developing organic semiconductors with efficient exciton transport.
文摘War rehearsals have become increasingly important in national security due to the growing complexity of international affairs.However,traditional rehearsal methods,such as military chess simulations,are inefficient and inflexible,with particularly pronounced limitations in command and decision-making.The overwhelming volume of information and high decision complexity hinder the realization of autonomous and agile command and control.To address this challenge,an intelligent warfare simulation framework named Command-Agent is proposed,which deeply integrates large language models(LLMs)with digital twin battlefields.By constructing a highly realistic battlefield environment through real-time simulation and multi-source data fusion,the natural language interaction capabilities of LLMs are leveraged to lower the command threshold and to enable autonomous command through the Observe-Orient-Decide-Act(OODA)feedback loop.Within the Command-Agent framework,a multimodel collaborative architecture is further adopted to decouple the decision-generation and command-execution functions of LLMs.By combining specialized models such as Deep Seek-R1 and MCTool,the limitations of single-model capabilities are overcome.MCTool is a lightweight execution model fine-tuned for military Function Calling tasks.The framework also introduces a Vector Knowledge Base to mitigate hallucinations commonly exhibited by LLMs.Experimental results demonstrate that Command-Agent not only enables natural language-driven simulation and control but also deeply understands commander intent.Leveraging the multi-model collaborative architecture,during red-blue UAV confrontations involving 2 to 8 UAVs,the integrated score is improved by an average of 41.8%compared to the single-agent system(MCTool),accompanied by a 161.8%optimization in the battle loss ratio.Furthermore,when compared with multi-agent systems lacking the knowledge base,the inclusion of the Vector Knowledge Base further improves overall performance by 16.8%.In comparison with the general model(Qwen2.5-7B),the fine-tuned MCTool leads by 5%in execution efficiency.Therefore,the proposed Command-Agent introduces a novel perspective to the military command system and offers a feasible solution for intelligent battlefield decision-making.
基金supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1003100)the National Key R&D Program of China(Grant No.2024YFC2813700)。
文摘With the convergence of sensor technology,artificial intelligence,and the Internet of Things,intelligent vibration monitoring systems are undergoing transformative development.This evolution imposes stringent demands on the miniaturization,low power consumption,high integration,and environmental adaptability of transducers.Graphene,renowned for its superlative physicochemical attributes,holds significant promise for application in micro-and nanoelectromechanical systems(M/NEMS).However,the inherent central symmetry of graphene restricts its utility in piezoelectric devices.Inspired by the sensilla trichoidea of spiders,a threedimensional(3D)cilia-like monolayer graphene omnidirectional vibration transducer(CGVT)based on a stress-induced self-assembly mechanism is fabricated,demonstrating notable performance and high-temperature resistance.Furthermore,3D vibration vector decoding is realized via an omnidirectional decoupling algorithm based on one-dimensional convolutional neural networks(1DCNN)to achieve precise discrimination of vibration directions.The 3D bionic vibration-sensing system incorporates a spider web structure into a bionic cilia MEMS chip through a gold wire bonding process,enabling the realization of three distinct mechanisms for vibration detection and recognition.In particular,these devices are manufactured using silicon-based semiconductor processing techniques and MEMS fabrication methodologies,leading to a substantial reduction in the dimensions of individual components compared to traditional counterparts.
基金supported by National Natural Science Foundation of China (Grant Nos. 10973023,11103046,11203048)
文摘A Stewart platform is introduced in thc 500 m aperture spherical radio telescope（FAST） as an accuracy adjustable mechanism for teed receivers. Accuracy analysis is the basis of accuracy design. However, a rapid and effective accuracy analysis method for parallel manipulator is still needed. In order to enhance solution efficiency, an interval analysis method（lA method） is introduced to solve the terminal error bound of the Stewart platform with detailed solution path. Taking a terminal pose of the Stewart platform in FAST as an example, the terminal error is solved by the Monte Carlo method（MC method） by 4 980 s, the stochastic mathematical method（SM method） by 0.078 s, and the IA method by 2.203 s. Compared with MC method, the terminal error by SM method leads a 20% underestimate while the IA method can envelop the real error bound of the Stewart platform. This indicates that the IA method outperforms the other two methods by providing quick calculations and enveloping the real error bound of the Stewart platform. According to the given structural error of the dimension parameters of the Stewart platform, the IA method gives a maximum position error of 19.91 mm and maximum orientation error of 0.534°, which suggests that the IA method can be used for accuracy design of the Stewart platfbnn in FAST. The 1A method presented is a rapid and effective accuracy analysis method for Stewart platform.
基金supported by National Natural Science Foundation of China(Grant No.51135008)National Basic Research Program of China(973 Program,Grant No.2013CB035400)China Postdoctoral Science Foundation(Grant Nos.2012M520256,2013T60107)
文摘Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method for engineering application is a very challenging issue, which should be further studied in the field. Grassmann line geometry, which can investigate the dimensions of spatial line-clusters in a concise way, is taken as the mathematic foundation. Atlas method is introduced to visually describe the degrees of freedom（DOFs） and constraints of a mechanism, and the dual rule is brought in to realize the mutual conversion of the freedom-space and constraint-space. Consequently, a systematic method based on Grassmann line geometry and Atlas method is generated and the entire type synthesis process is presented. Three type 4-DOF PKMs, i.e., 1T3R, 2T2R and 3T1R（T： translational DOF; R： rotational DOF）, are classified according to the different combinations of the translational DOFs and rotational DOFs. The type synthesis of 4-DOF PKMs is carried out and the possible configurations are thoroughly investigated. Some new PKMs with useful functions are generated during this procedure. The type synthesis method based on Grassmann line geometry and Atlas method is intuitive and concise, and can reduce the complexity of the PKMs＇ type synthesis. Moreover, this method can provide theoretical guidance for other PKMs＇ type synthesis and engineering application. A novel type synthesis method is proposed, which solves the existing methods＇ problems in terms of complicated, not intuitive and unsuitable for practical application.
基金supported by the National Natural Science Foundation of China(51777215)National Natural Science Foundation of China(51775306)+1 种基金Beijing Municipal Natural Science Foundation(4192027)the Graduate Innovation Fund of China University of Petroleum(YCX2020097)。
文摘Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)Tx(PVA/MXene)nanofibers film and monolayer molybdenum diselenide(MoSe2)piezoelectric nanogenerator(PENG)was reported for the first time.The monolayer MoSe_(2)-based PENG was fabricated by atmospheric pressure chemical vapor deposition techniques,which can generate a peak output of 35 mV and a power density of42 mW m^(-2).The flexible PENG integrated on polyethylene terephthalate(PET)substrate can harvest energy generated by different parts of human body and exhibit great application prospects in wearable devices.The electrospinned PVA/MXene nanofiber-based humidity sensor with flexible PET substrate under the driven of monolayer MoSe_(2) PENG,shows high response of~40,fast response/recovery time of 0.9/6.3 s,low hysteresis of 1.8%and excellent repeatability.The self-powered flexible humidity sensor yields the capability of detecting human skin moisture and ambient humidity.This work provides a pathway to explore the high-performance humidity sensor integrated with PENG for the self-powered flexible electronic devices.
基金supported by National Natural Science Foundation of China (Grant No. 50905012)the Fundamental Research Funds for the Central Universities of China (Grant No. 2012JBM088)
文摘A multiple-legged robot is traditionally controlled by using its dynamic model.But the dynamic-model-based approach fails to acquire satisfactory performances when the robot faces rough terrains and unknown environments.Referring animals＇ neural control mechanisms,a control model is built for a quadruped robot walking adaptively.The basic rhythmic motion of the robot is controlled by a well-designed rhythmic motion controller（RMC） comprising a central pattern generator（CPG） for hip joints and a rhythmic coupler（RC） for knee joints.CPG and RC have relationships of motion-mapping and rhythmic couple.Multiple sensory-motor models,abstracted from the neural reflexes of a cat,are employed.These reflex models are organized and thus interact with the CPG in three layers,to meet different requirements of complexity and response time to the tasks.On the basis of the RMC and layered biological reflexes,a quadruped robot is constructed,which can clear obstacles and walk uphill and downhill autonomously,and make a turn voluntarily in uncertain environments,interacting with the environment in a way similar to that of an animal.The paper provides a biologically inspired architecture,with which a robot can walk adaptively in uncertain environments in a simple and effective way,and achieve better performances.
基金funded by the National Natural Science Foundation of China(51705024,51535002,51675053,61903041,61903042,and 61903041)the National Key Research and Development Program of China(2016YFF0101801)+4 种基金the National Hightech Research and Development Program of China(2015AA042308)the Innovative Equipment Pre-Research Key Fund Project(6140414030101)the Manned Space Pre-Research Project(20184112043)the Beijing Municipal Natural Science Foundation(F7202017 and 4204101)the Beijing Nova Program of Science and Technology(Z191100001119052)。
文摘Structural deformation monitoring of flight vehicles based on optical fiber sensing(OFS)technology has been a focus of research in the field of aerospace.After nearly 30 years of research and development,Chinese and international researchers have made significant advances in the areas of theory and methods,technology and systems,and ground experiments and flight tests.These advances have led to the development of OFS technology from the laboratory research stage to the engineering application stage.However,a few problems encountered in practical applications limit the wider application and further development of this technology,and thus urgently require solutions.This paper reviews the history of research on the deformation monitoring of flight vehicles.It examines various aspects of OFS-based deformation monitoring including the main varieties of OFS technology,technical advantages and disadvantages,suitability in aerospace applications,deformation reconstruction algorithms,and typical applications.This paper points out the key unresolved problems and the main evolution paradigms of engineering applications.It further discusses future development directions from the perspectives of an evolution paradigm,standardization,new materials,intelligentization,and collaboration.
基金supported by National Natural Science Foundation of China(Grant No.51021064)National Key Scientific and Technological Program of China(Grant No.2010ZX04004-116)
文摘The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2006AA04Z133)National Natural Science Foundation of China(Grant No.50605035,10778625)
文摘Inertia match of the parallel manipulator means the ratio of the inertial load of the parallel manipulator converted to each actuator shaft and the moment of inertia of the actuator is kept within a reasonable range.Currently there are many studies on parallel manipulators,but few mention inertia parameters and inertia match of parallel manipulators.This paper focuses on the inertia characteristics of the 3-RRR reconfigurable planar parallel manipulator.On the basis of the inverse dynamic formulations deduced with the principle of virtual work,the inertia matrix of the 3-RRR planar parallel manipulator in the actuator space is obtained in algebraic form.Then,by unifying the dimension and averaging diagonal elements of the inertia matrix,the equivalent inertia of the parallel manipulator,which is the inertial load of the parallel manipulator converted to each actuator shaft,is determined.By transforming the inertia problem of the 3-RRR parallel manipulator into that of the serial multi-bar manipulator,the practicality of the equivalent inertia deduced by inverse dynamics is demonstrated.According to the physical meaning of the inertia equation,the manipulator is divided in to three parts.Further analysis is carried out on the contribution of each part to the equivalent inertia and their distributions in the required workspace,revealing that the passive links cannot ignored in calculating the equivalent inertia of the parallel manipulator.Finally,the inertia match for the 3-RRR reconfigurable parallel manipulator under three configurations is accomplished,and reducers are selected.The equivalent inertia calculation and the inertial match results illustrate that the inertia math is a necessary step to the design of the parallel manipulator,and inertia parameters dramatically affect dynamic performances of parallel manipulators.Besides,the equivalent inertia and inertial match principles,proposed in the paper,can be widely applied in the dynamic analysis and servomotors selecting for the parallel manipulator.
基金supported by National Natural Science Foundation of China (Grant Nos. 51165040,50775119)Visiting Scholar Foundation of Key Lab in University of China (Grant No. GZKF-201020)
文摘Needle insertion is a common surgical procedure used in diagnosis and treatment.The needle steering technologies make continuous developments in theoretical and practical aspects along with the in-depth research on needle insertion.It is necessary to summarize and analyze the existing results to promote the future development of theories and applications of needle insertion.Thus,a survey of the state of the art of research is presented on algorithms of needle steering techniques,the surgical robots and devices.Based on the analysis of the needle insertion procedure,the concept of needle steering is defined as a kinematics problem,which is to place the needle at the target and avoid the obstacles.The needle steering techniques,including the artificial potential field method and the nonholonomic model,are introduced to control the needles for improving the accuracy.Based on the quasi-static thinking,the virtual spring model and the cantilever-beam model are developed to calculate the amount of needle deflection and generate the needle path.The phantoms instead of the real tissue are used to verify the models mentioned in most of the experimentations.For the desired needle trajectories,the image-guided robotic devices and some novel needles are presented to achieve the needle steering.Finally,the challenges are provided involving the controllability of the long flexible needle and the properties of soft tissue.The results and investigations can be used for further study on the precision and accuracy of needle insertion.
