Reducing the peak actuating force(PAF)and parasitic displacement is of high significance for improving the performance of compliant parallel mechanisms(CPMs).In this study,a 2-DOF 4-4R compliant parallel pointing mech...Reducing the peak actuating force(PAF)and parasitic displacement is of high significance for improving the performance of compliant parallel mechanisms(CPMs).In this study,a 2-DOF 4-4R compliant parallel pointing mechanism(4-4R CPPM)was used as the object,and the actuating force of the mechanism was optimized through redundant actuation.This was aimed at minimizing the PAF and parasitic displacement.First,a kinetostatic model of the redundantly actuated 4-4R CPPM was established to reveal the relationship between the input forces/displacements and the output displacements of the mobile platform.Subsequently,based on the established kinetostatic model,methods for optimizing the actuating force distribution with the aim of minimizing the PAF and parasitic displacement were introduced successively.Second,a simulated example of a mobile platform’s spatial pointing trajectory validated the accuracy of the kinetostatic model.The results show a less than 0.9%relative error between the analytical and finite element(FE)results,and the high consistency indicates the accuracy of the kinetostatic model.Then,the effectiveness of the method in minimizing the PAF and parasitic displacement was validated using two simulated examples.The results indicate that compared with the non-redundant actuation case,the PAF of the mechanism could be reduced by up to 50%,and the parasitic displacement was reduced by approximately three-four orders of magnitude by means of redundant actuation combined with the optimal distribution of the actuating force.As expected,with the reduction in parasitic displacement,the FE-results of the output angular displacements(θ_(x) andθ_(z))of the mobile platform were closer to the target oscillation trajectory.This further verified that the reduction in parasitic displacement is indeed effective in improving the motion accuracy of the mechanism.The advantage of this proposed method is that it reduces the PAF and parasitic displacement from the perspective of the actuating force control strategy,without the requirement of structural changes to the original mechanism.展开更多
The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centraliz...The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centralized,inefficient,and bulky during application,which limits its development in the exoskeleton.For improving the robot's performance,its hydraulic actuating system should be optimized further.In this paper a novel hydraulic actuating system(HAS)based on electric-hydrostatic actuator is proposed,which is applied to hip and knee joints.Each HAS integrates an electric servo motor,a high-speed micro pump,a specific tank,and other components into a module.The specific parameters are obtained through relevant simulation according to human motion data and load requirements.The dynamic models of the HAS are built,and validated by the system identification.Experiments of trajectory tracking and human-exoskeleton interaction are carried out,which demonstrate the proposed HAS has the ability to be applied to the exoskeleton.Compared with the previous prototype,the total weight of the HAS in the robot is reduced by about 40%,and the power density is increased by almost 1.6 times.展开更多
Piezoelectric ceramic element (PCE) is a kind of actuator applied widely on the intelligent material & structure. Establishing the relationship between the transferring stress and the controlling signal, namely t...Piezoelectric ceramic element (PCE) is a kind of actuator applied widely on the intelligent material & structure. Establishing the relationship between the transferring stress and the controlling signal, namely the transferring and actuating equation, is a key step to analyze the actuating performance of the PCE. Based on the method of the shear lag theory, the procedure of the stress transferring is analyzed and the transferring and actuating model is established in this paper. Some measurements for PCE(PZT5) actuating the Glass Fiber/Epoxy laminate have been done to verify the model established. The experimental results show that the theoretical model agrees well with the practice. Finally, the effect of the main factors on PCE actuating the laminate is studied by using the experimental and theoretical results.展开更多
Three kinds of landing gear actuating cylinder inner-locks of an aircrafi ： block ring lock, steel ball lock, finger lock are taken as the study object based on the mechanics, geometry, materials, technology etc and ...Three kinds of landing gear actuating cylinder inner-locks of an aircrafi ： block ring lock, steel ball lock, finger lock are taken as the study object based on the mechanics, geometry, materials, technology etc and some aircrafi typical inner-lock practical applications. The working principle of the three typical actuating cylinder innerlocks are expounded and the stress and workmanship requirements of the three inner-lock core components are analyzed. The advantages and disadvantages of different kinds are compared and the characteristics and applications of the three inner-locks investigated. The research and analysis results provide valuable information for the actuating cylinder inner-lock of the aircraft landing gear design.展开更多
In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting...In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.展开更多
The influence of actuating voltage and discharge gap on plasma assisted detonation initiation by alternating current dielectric barrier discharge was studied in detail.A loose coupling method was used to simulate the ...The influence of actuating voltage and discharge gap on plasma assisted detonation initiation by alternating current dielectric barrier discharge was studied in detail.A loose coupling method was used to simulate the detonation initiation process of a hydrogen–oxygen mixture in a detonation tube under different actuating voltage amplitudes and discharge gap sizes.Both the discharge products and the detonation forming process assisted by the plasma were analyzed.It was found that the patterns of the temporal and spatial distributions of discharge products in one cycle keep unchanged as changing the two discharge operating parameters.However,the adoption of a higher actuating voltage leads to a higher active species concentration within the discharge zone,and atom H is the most sensitive to the variations of the actuating voltage amplitude among the given species.Adopting a larger discharge gap results in a lower concentration of the active species,and all species have the same sensitivity to the variations of the gap.With respect to the reaction flow of the detonation tube,the corresponding deflagration to detonation transition（DDT） time and distance become slightly longer when a higher actuating voltage is chosen.The acceleration effect of plasma is more prominent with a smaller discharge gap,and the benefit builds gradually throughout the DDT process.Generally,these two control parameters have little effect on the amplitude of the flow field parameters,and they do not alter the combustion degree within the reaction zone.展开更多
Aiming at studying the influence of actuating frequency on plasma assisted detonation initiation by alternating current dielectric barrier discharge, a loosely coupled method is used to simulate the detonation initiat...Aiming at studying the influence of actuating frequency on plasma assisted detonation initiation by alternating current dielectric barrier discharge, a loosely coupled method is used to simulate the detonation initiation process of a hydrogenoxygen mixture in a detonation tube at different actuating frequencies. Both the discharge products and the detonation forming process which is assisted by the plasma are analyzed. It is found that the patterns of the temporal and spatial distributions of discharge products in one cycle are not changed by the actuating frequency. However, the concentration of every species decreases as the actuating frequency rises, and atom O is the most sensitive to this variation, which is related to the decrease of discharge power. With respect to the reaction flow of the detonation tube, the deflagration-todetonation transition（DDT） time and distance both increase as the actuating frequency rises, but the degree of effect on DDT development during flow field evolution is erratic. Generally, the actuating frequency affects none of the amplitude value of the pressure, temperature, species concentration of the flow field, and the combustion degree within the reaction zone.展开更多
The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （...The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （FSMA） composite and hybrid mechanism that can provide a fast response and a strong thrust. The caudal peduncle actuator was inspired by Scomber Scombrus which utilises thunniform mode swimming, which is the most efficient locomotion mode evolved in the aquatic environment, where the thrust is generated by the lift-based method, allowing high cruising speeds to be maintained for a long period of time. The morphology of an average size Scomber Scombrus （length in 310 mm） was investigated, and a 1：1 scale caudal peduncle actuator prototype was modelled and fabricated. The propulsive wave characteristics of the fish at steady speeds were employed as initial design objectives. Some key design parameters are investigated, i.e. aspect ratio （AR） （AR = 3.49）, Reynolds number （Re = 429 649）, reduced frequency （σ = 1.03）, Strouhal number （St = 0.306） and the maximum strain of the bent tail was estimated at ε = 1.11% which is in the range of superelasticity. The experimental test of the actuator was carried out in a water tank. By applying 7 V and 2.5 A, the actuator can reach the tip-to-tip rotational angle of 85° at 4 Hz.展开更多
In micro-electrochemical machining(μECM), material dissolution takes place at very close vicinity of tool electrode due to localization of electric field. Controlling the gap between tool electrode and workpiece is t...In micro-electrochemical machining(μECM), material dissolution takes place at very close vicinity of tool electrode due to localization of electric field. Controlling the gap between tool electrode and workpiece is the key to μECM. Therefore, a new method is proposed to solve a variety of problems in small gap control. In the present context, experiments were carried out with an indigenously developed setup to fabricate cylindrical arrays. During the machining process, the flat electrode bends due to electrostatic force in pulse on-time, which self-adaptively narrows the gap between the electrode and the workpiece. The workpiece material will be removed once the gap meets the processing condition. Therefore, this method has advantages of reducing dependence on high precision machine tools and of avoiding complex servo control. The flat electrode quickly restores to its original condition when it is in pulse off-time, making the gap much larger than that in traditional electrochemical machining(ECM). The large gap benefits debris removing, which improves the machining accuracy. The influence of different experimental parameters on accuracy and efficiency during the machining process has been investigated. It is observed that with the increase in applied voltage or concentration of electrolyte, the material removal rate and the process gap both increase. The detailed analysis of the experimental results is described in this paper.展开更多
Multi-functional smart textiles are receiving a lot of attention for their tremendous application devel-opment in the fields of personal thermal management,artificial muscle,electronic skin,and human-machine interacti...Multi-functional smart textiles are receiving a lot of attention for their tremendous application devel-opment in the fields of personal thermal management,artificial muscle,electronic skin,and human-machine interaction.For the complex use of many different smart textiles,designing a multifunctional textile that integrates personal thermal management,smart sensing,and flexible actuating is still a great challenge.Here,we decorated MXene on elastic fabrics by simple dip-coating and asymmetric Ecoflex encapsulation protocol to obtain electrical/optical dual-energy-driven wearable heaters with highly re-sponsive actuating and strain-sensing performance.The MXene fabric-based heaters(MFHs)have high efficiency of Joule heating(Steady state temperature of 116.7℃ at 12 V)and photothermal conversion performance(180.3℃ in 60 s under the near infrared lamp irradiation,up to 57.5℃ under 600 W m^(-2) simulated solar irradiation).Benefiting from high electrical/optical dual-energy conversion efficiency,MFH has a fast photothermal driving effect(bending angle up to 360°in 5 s)due to the different curvature of thermal expansion on both sides of the fabric.Interestingly,MFH has the capability to monitor human strain(such as muscle and joint movements).Based on the above excellent performance,we finally be-lieve that the MFHs have broad application prospects in the fields of all-weather body heat management,health monitoring,thermal health care,and thermal robotics.展开更多
Achieving autonomously responding to external stimuli and providing real-time feedback on their motion state are key challenges in soft robotics.Herein,we propose an asymmetric three-layer hydrogel muscle with integra...Achieving autonomously responding to external stimuli and providing real-time feedback on their motion state are key challenges in soft robotics.Herein,we propose an asymmetric three-layer hydrogel muscle with integrated sensing and actuating performances.The actuating layer,made of p(NIPAm-HEMA),features an open pore structure,enabling it to achieve 58%volume shrinkage in just 8 s.The customizable heater allows for efficient programmable deformation of the actuating layer.A strain-responsive hydrogel layer,with a linear response of up to 50%strain,is designed to sense the deformation process.Leveraging these actuating and sensing capabilities,we develop an integrated hydrogel muscle that can recognize lifted objects with various weights or grasped objects of different sizes.Furthermore,we demonstrate a self-crawling robot to showcase the application potential of the hydrogel muscle for soft robots working in aquatic environments.This robot,featuring a modular distributed sensing and actuating layer,can autonomously move forward under closed-loop control based on self-detected resistance signals.The strategy of modular distributed stimuli-responsive sensing and actuating materials offers unprecedented capabilities for creating smart and multifunctional soft robotics.展开更多
Despite enormous efforts in actuators,most researches are only limited to various actuation behaviors and demonstrations of soft materials.It has not yet been reported to capture and monitor its movement status in an ...Despite enormous efforts in actuators,most researches are only limited to various actuation behaviors and demonstrations of soft materials.It has not yet been reported to capture and monitor its movement status in an invisible environment.Therefore,it is of great significance to develop a self-sensing and self-actuating dual-function hydrogel actuator system to realize real-time monitoring.Here,we report a bifunctional hydrogel system with self-actuating and self-monitoring abilities,which combines the functions of photothermal actuation and electrical resistance sensing into a single material.The bilayer tough conductive hydrogel synthesized by unconventional complementary concentration recombination and cryogenic freezing technique presents a dense conductive network and high-porosity structure,achieving high toughness at 190.3 kPa of tensile strength,high stretchability(164.3%strain),and the toughness dramatically(1,471.4 kJ·m^(−3)).The working mechanism of the monitoring and self-sensing system is accomplished through the integrated monitoring device of surface temperature–bending angle–electron current,to solve the problem of not apperceiving actuator motion state when encountering obstacles in an invisible environment.We demonstrated for the first time a photothermal actuator’s motion of a football player and goalkeeper to finish the penalty and a soft actuator hand,which can achieve the action of sticking to grab and release under photo-thermal actuation.When connected to the control closed circuit,the actuator realized closed-loop monitoring and sensing feedback.The development of bifunctional hydrogel systems may bring new opportunities and ideas in the fields of material science,circuit technology,sensors,and mechanical engineering.展开更多
Multifunctionality has become a mainstream trend in the development of smart clothing and flexible wearable devices.Nevertheless,it remains a grand challenge to realize multiple functions,such as sensing,actuating and...Multifunctionality has become a mainstream trend in the development of smart clothing and flexible wearable devices.Nevertheless,it remains a grand challenge to realize multiple functions,such as sensing,actuating and information displaying,in one single multifunctional material.Here,we present one multifunctional integration strategy by employing monolithic superaligned carbon nanotube(SACNT)composite,which can leverage three different functions through fascinating features of SACNT.Firstly,by using thermochromic dye as a color-memorizing component and SACNT as a photothermal converter,the composite film can be utilized as a flexible rewritable medium.It demonstrates excellent rewriting performances(reversibility>500 times).Secondly,the composite can be tailored to fabricate an actuator,when its length direction is along the SACNT alignment.The actuator shows a bending-morphing when illuminated by near-infrared light.The morphing is attributed to a large difference in volume change between the SACNT and polymer when the SACNT absorbs the optical energy and heats the composite.Thirdly,owing to the unique anisotropy of SACNT,the composite is easily to be stretched in the direction perpendicular to the SACNT alignment,accompanied by a change in electrical resistance.Therefore,the composite is able to be used as a strain sensor.Finally,we fabricate two smart wearable devices to demonstrate the applications,which realize the functions of human-motion detection(sensing)and rewritable information display(rewriting)simultaneously.This multifunctional SACNT composite is expected to have potential applications in the next-generation wearable devices,smart clothing and so on.展开更多
Anisotropic composite hydrogels have wide applications in the fields of materials for actuators and sensors.Herein,we report an anisotropic composite hydrogel prepared by a mechanical-strain-induced method.Polymer net...Anisotropic composite hydrogels have wide applications in the fields of materials for actuators and sensors.Herein,we report an anisotropic composite hydrogel prepared by a mechanical-strain-induced method.Polymer networks including poly(N-isopropylacrylamide)(PNIPAM)and sodium alginate(SA),as well as carbon nanotubes(CNTs)are found to align simultaneously by stretching,and then fixed by physical crosslinking through non-covalent bonds.Composite hydrogels with doubly aligned polymer networks showed anisotropic optical and mechanical properties.The actuation performance of the anisotropic composite hydrogels as compared with the isotropic ones was found to be enhanced,which showed the capability of lifting 100 times its weight with 20%contraction strain.Besides,a bilayer hydrogel was designed to bend with a maximum of 390°to mimic the tendril behavior of plants.展开更多
Integrating energy-storage devices(supercapacitors)and shape-deformation devices(actuators)advances the miniaturization and multifunctional development of soft robots.However,soft robots necessitate supercapacitors wi...Integrating energy-storage devices(supercapacitors)and shape-deformation devices(actuators)advances the miniaturization and multifunctional development of soft robots.However,soft robots necessitate supercapacitors with high energy-storage performance and actuators with excellent actuation capability.Here,inspired by ant nests,we present a porous structure fabricated by MXene-graphene-methylcellulose(M-GMC)composite,which overcomes the self-stacking of MXene nanosheets and offers a larger specific surface area.The porous structure provides more channels and active sites for electrolyte ions,resulting in high energy storage performance.The areal capacitance of the M-GMC electrode reaches up to 787.9 mF·cm^(−2),significantly superior to that of the pristine MXene electrode(449.1 mF·cm^(−2)).Moreover,the M-GMC/polyethylene bilayer composites with energy storage and multi-responsive actuation functions are developed.The M-GMC is used as the electrode and the polyethylene is used as the encapsulation layer of the quasi-solid-state supercapacitor.Meanwhile,the actuators fabricated by the bilayer composites can be driven by light or low voltage(≤9 V).The maximum bending curvature is up to 5.11 cm^(−1).Finally,a smart gripper and a fully encapsulated smart integrated circuit based on the M-GMC/polyethylene are designed.The smart gripper enables programmable control with multi-stage deformations.The applications realize the intelligence and miniaturization of soft robots.The ant-nest-inspired M-GMC composites would provide a promising development strategy for soft robots and smart integrated devices.展开更多
Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices...Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices[1].Thermal expansion is a pivotal aspect in solid state chemistry,intricately intertwined with various factors such as crystal structure,chemical composition,electronic configuration,microstructure,and defects.Most materials undergo isotropic and positive thermal expansion(PTE)because of the disharmonic vibrational amplitudes of their chemical bonds.Moreover,anisotropic thermal expansion(ATE)and negative thermal expansion(NTE)are fascinating physical attributes of solids,which can originate from electronic or magnetic mechanisms,as well as through a transverse phonon mechanism in insulating lattice solids.展开更多
Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and el...Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.展开更多
This work proposes the application of an iterative learning model predictive control(ILMPC)approach based on an adaptive fault observer(FOBILMPC)for fault-tolerant control and trajectory tracking in air-breathing hype...This work proposes the application of an iterative learning model predictive control(ILMPC)approach based on an adaptive fault observer(FOBILMPC)for fault-tolerant control and trajectory tracking in air-breathing hypersonic vehicles.In order to increase the control amount,this online control legislation makes use of model predictive control(MPC)that is based on the concept of iterative learning control(ILC).By using offline data to decrease the linearized model’s faults,the strategy may effectively increase the robustness of the control system and guarantee that disturbances can be suppressed.An adaptive fault observer is created based on the suggested ILMPC approach in order to enhance overall fault tolerance by estimating and compensating for actuator disturbance and fault degree.During the derivation process,a linearized model of longitudinal dynamics is established.The suggested ILMPC approach is likely to be used in the design of hypersonic vehicle control systems since numerical simulations have demonstrated that it can decrease tracking error and speed up convergence when compared to the offline controller.展开更多
This paper endeavours to bridge the existing gap in muscular actuator design for ligament-skeletal-inspired robots,thereby fostering the evolution of these robotic systems.We introduce two novel compliant actuators,na...This paper endeavours to bridge the existing gap in muscular actuator design for ligament-skeletal-inspired robots,thereby fostering the evolution of these robotic systems.We introduce two novel compliant actuators,namely the Internal Torsion Spring Compliant Actuator(ICA)and the External Spring Compliant Actuator(ECA),and present a comparative analysis against the previously conceived Magnet Integrated Soft Actuator(MISA)through computational and experimental results.These actuators,employing a motor-tendon system,emulate biological muscle-like forms,enhancing artificial muscle technology.Then,applications of the proposed actuators in a robotic arm inspired by the human musculoskeletal system are presented.Experiments demonstrate satisfactory power in tasks like lifting dumbbells(peak power:36 W),playing table tennis(end-effector speed:3.2 m/s),and door opening,without compromising biomimetic aesthetics.Compared to other linear stiffness serial elastic actuators(SEAs),ECA and ICA exhibit high power-to-volume(361×10^(3)W/m^(3))and power-to-mass(111.6 W/kg)ratios respectively,endorsing the biomimetic design’s promise in robotic development.展开更多
As a kind of ionic artificial muscle material,Ionic Polymer-Metal Composites(IPMCs)have the advantages of a low drive current,light weight,and significant flexibility.IPMCs are widely used in the fields of biomedicine...As a kind of ionic artificial muscle material,Ionic Polymer-Metal Composites(IPMCs)have the advantages of a low drive current,light weight,and significant flexibility.IPMCs are widely used in the fields of biomedicine,soft robots,etc.However,the displacement and blocking force of the traditional sheet-type Nafion-IPMC need to be improved,and it has the limitation of unidirectional actuation.In this paper,a new type of short side chain Aquivion material is used as the polymer in the IPMC.The cylindrical IPMC is prepared by extrusion technology to improve its actuation performance and realize multi-degree-of-freedom motion.In comparison to the traditional Nafion-IPMC,the ion exchange capacity,specific capacitance,and conductivity of Aquivion-IPMC are improved by 28%,27%,and 32%,respectively,and the displacement and blocking force are improved by 57%and 25%,respectively.The cylindrical actuators can be deflected in eight directions.This indicates that Aquivion,as a polymer membrane for IPMC,holds significant application potential.By designing a cylindrical IPMC electrode distribution,the multi-degree-of-freedom deflection of IPMC can be realized.展开更多
基金Supported by Key Project of Hubei Provincial Department of Education Research Program(Grant No.D20211401).
文摘Reducing the peak actuating force(PAF)and parasitic displacement is of high significance for improving the performance of compliant parallel mechanisms(CPMs).In this study,a 2-DOF 4-4R compliant parallel pointing mechanism(4-4R CPPM)was used as the object,and the actuating force of the mechanism was optimized through redundant actuation.This was aimed at minimizing the PAF and parasitic displacement.First,a kinetostatic model of the redundantly actuated 4-4R CPPM was established to reveal the relationship between the input forces/displacements and the output displacements of the mobile platform.Subsequently,based on the established kinetostatic model,methods for optimizing the actuating force distribution with the aim of minimizing the PAF and parasitic displacement were introduced successively.Second,a simulated example of a mobile platform’s spatial pointing trajectory validated the accuracy of the kinetostatic model.The results show a less than 0.9%relative error between the analytical and finite element(FE)results,and the high consistency indicates the accuracy of the kinetostatic model.Then,the effectiveness of the method in minimizing the PAF and parasitic displacement was validated using two simulated examples.The results indicate that compared with the non-redundant actuation case,the PAF of the mechanism could be reduced by up to 50%,and the parasitic displacement was reduced by approximately three-four orders of magnitude by means of redundant actuation combined with the optimal distribution of the actuating force.As expected,with the reduction in parasitic displacement,the FE-results of the output angular displacements(θ_(x) andθ_(z))of the mobile platform were closer to the target oscillation trajectory.This further verified that the reduction in parasitic displacement is indeed effective in improving the motion accuracy of the mechanism.The advantage of this proposed method is that it reduces the PAF and parasitic displacement from the perspective of the actuating force control strategy,without the requirement of structural changes to the original mechanism.
基金Supported by Nati onal Key R&D Program of China(Grant No.2018YFB1305400,2018YFB1305402)National Natural Science Foundation of China(Grant No.518902883)Fun dame ntal Resea rch Funds for the Central Universities(Grant No.2018XZZX001-04).
文摘The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centralized,inefficient,and bulky during application,which limits its development in the exoskeleton.For improving the robot's performance,its hydraulic actuating system should be optimized further.In this paper a novel hydraulic actuating system(HAS)based on electric-hydrostatic actuator is proposed,which is applied to hip and knee joints.Each HAS integrates an electric servo motor,a high-speed micro pump,a specific tank,and other components into a module.The specific parameters are obtained through relevant simulation according to human motion data and load requirements.The dynamic models of the HAS are built,and validated by the system identification.Experiments of trajectory tracking and human-exoskeleton interaction are carried out,which demonstrate the proposed HAS has the ability to be applied to the exoskeleton.Compared with the previous prototype,the total weight of the HAS in the robot is reduced by about 40%,and the power density is increased by almost 1.6 times.
文摘Piezoelectric ceramic element (PCE) is a kind of actuator applied widely on the intelligent material & structure. Establishing the relationship between the transferring stress and the controlling signal, namely the transferring and actuating equation, is a key step to analyze the actuating performance of the PCE. Based on the method of the shear lag theory, the procedure of the stress transferring is analyzed and the transferring and actuating model is established in this paper. Some measurements for PCE(PZT5) actuating the Glass Fiber/Epoxy laminate have been done to verify the model established. The experimental results show that the theoretical model agrees well with the practice. Finally, the effect of the main factors on PCE actuating the laminate is studied by using the experimental and theoretical results.
文摘Three kinds of landing gear actuating cylinder inner-locks of an aircrafi ： block ring lock, steel ball lock, finger lock are taken as the study object based on the mechanics, geometry, materials, technology etc and some aircrafi typical inner-lock practical applications. The working principle of the three typical actuating cylinder innerlocks are expounded and the stress and workmanship requirements of the three inner-lock core components are analyzed. The advantages and disadvantages of different kinds are compared and the characteristics and applications of the three inner-locks investigated. The research and analysis results provide valuable information for the actuating cylinder inner-lock of the aircraft landing gear design.
文摘In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.
基金supported by National Natural Science Foundation of China with grant numbers 91441123,51777214the Open Project of Science and Technology on Scramjet Laboratory with grant number CG-2014-05-118 under the technical monitor of program manager Dr Zhiyong Lin
文摘The influence of actuating voltage and discharge gap on plasma assisted detonation initiation by alternating current dielectric barrier discharge was studied in detail.A loose coupling method was used to simulate the detonation initiation process of a hydrogen–oxygen mixture in a detonation tube under different actuating voltage amplitudes and discharge gap sizes.Both the discharge products and the detonation forming process assisted by the plasma were analyzed.It was found that the patterns of the temporal and spatial distributions of discharge products in one cycle keep unchanged as changing the two discharge operating parameters.However,the adoption of a higher actuating voltage leads to a higher active species concentration within the discharge zone,and atom H is the most sensitive to the variations of the actuating voltage amplitude among the given species.Adopting a larger discharge gap results in a lower concentration of the active species,and all species have the same sensitivity to the variations of the gap.With respect to the reaction flow of the detonation tube,the corresponding deflagration to detonation transition（DDT） time and distance become slightly longer when a higher actuating voltage is chosen.The acceleration effect of plasma is more prominent with a smaller discharge gap,and the benefit builds gradually throughout the DDT process.Generally,these two control parameters have little effect on the amplitude of the flow field parameters,and they do not alter the combustion degree within the reaction zone.
基金Project supported by the Open Project of Science and Technology on Scramjet Laboratory,China(Grant No.CG-2014-05-118)the National Natural Science Foundation of China(Grant No.91441123)
文摘Aiming at studying the influence of actuating frequency on plasma assisted detonation initiation by alternating current dielectric barrier discharge, a loosely coupled method is used to simulate the detonation initiation process of a hydrogenoxygen mixture in a detonation tube at different actuating frequencies. Both the discharge products and the detonation forming process which is assisted by the plasma are analyzed. It is found that the patterns of the temporal and spatial distributions of discharge products in one cycle are not changed by the actuating frequency. However, the concentration of every species decreases as the actuating frequency rises, and atom O is the most sensitive to this variation, which is related to the decrease of discharge power. With respect to the reaction flow of the detonation tube, the deflagration-todetonation transition（DDT） time and distance both increase as the actuating frequency rises, but the degree of effect on DDT development during flow field evolution is erratic. Generally, the actuating frequency affects none of the amplitude value of the pressure, temperature, species concentration of the flow field, and the combustion degree within the reaction zone.
文摘The paper addresses the designs of a caudal peduncle actuator, which is able to furnish a thrust for swimming of a robotic fish. The caudal peduncle actuator is based on concepts of ferromagnetic shape memory alloy （FSMA） composite and hybrid mechanism that can provide a fast response and a strong thrust. The caudal peduncle actuator was inspired by Scomber Scombrus which utilises thunniform mode swimming, which is the most efficient locomotion mode evolved in the aquatic environment, where the thrust is generated by the lift-based method, allowing high cruising speeds to be maintained for a long period of time. The morphology of an average size Scomber Scombrus （length in 310 mm） was investigated, and a 1：1 scale caudal peduncle actuator prototype was modelled and fabricated. The propulsive wave characteristics of the fish at steady speeds were employed as initial design objectives. Some key design parameters are investigated, i.e. aspect ratio （AR） （AR = 3.49）, Reynolds number （Re = 429 649）, reduced frequency （σ = 1.03）, Strouhal number （St = 0.306） and the maximum strain of the bent tail was estimated at ε = 1.11% which is in the range of superelasticity. The experimental test of the actuator was carried out in a water tank. By applying 7 V and 2.5 A, the actuator can reach the tip-to-tip rotational angle of 85° at 4 Hz.
基金supported by the National Natural Science Foundation of China(Grant No.51105110,51475107)Shenzhen Basic Research Program(Grant No.JCYJ20170811160440239)
文摘In micro-electrochemical machining(μECM), material dissolution takes place at very close vicinity of tool electrode due to localization of electric field. Controlling the gap between tool electrode and workpiece is the key to μECM. Therefore, a new method is proposed to solve a variety of problems in small gap control. In the present context, experiments were carried out with an indigenously developed setup to fabricate cylindrical arrays. During the machining process, the flat electrode bends due to electrostatic force in pulse on-time, which self-adaptively narrows the gap between the electrode and the workpiece. The workpiece material will be removed once the gap meets the processing condition. Therefore, this method has advantages of reducing dependence on high precision machine tools and of avoiding complex servo control. The flat electrode quickly restores to its original condition when it is in pulse off-time, making the gap much larger than that in traditional electrochemical machining(ECM). The large gap benefits debris removing, which improves the machining accuracy. The influence of different experimental parameters on accuracy and efficiency during the machining process has been investigated. It is observed that with the increase in applied voltage or concentration of electrolyte, the material removal rate and the process gap both increase. The detailed analysis of the experimental results is described in this paper.
基金the Key Research and Development Program of the Science and Technology Bureau of Ningbo City(Grant No.2023Z082)supported by the Major scientific and technologic project of Fuzhou Science and Technology Project Plan(No.2022-ZD-007)+2 种基金by the Jiangxi Provincial Administration for Market Regulation(No.GSJK202221)by the Natural Science Foundation Project of Shanghai“science and technology innovation action plan”(Nos.20ZR1400200 and 22ZR1400500)supported by Project(No.Grant52173218)supported by the National Natural Science Foundation of China,and funded by Shanghai Frontiers Science Center of Advanced Textiles.
文摘Multi-functional smart textiles are receiving a lot of attention for their tremendous application devel-opment in the fields of personal thermal management,artificial muscle,electronic skin,and human-machine interaction.For the complex use of many different smart textiles,designing a multifunctional textile that integrates personal thermal management,smart sensing,and flexible actuating is still a great challenge.Here,we decorated MXene on elastic fabrics by simple dip-coating and asymmetric Ecoflex encapsulation protocol to obtain electrical/optical dual-energy-driven wearable heaters with highly re-sponsive actuating and strain-sensing performance.The MXene fabric-based heaters(MFHs)have high efficiency of Joule heating(Steady state temperature of 116.7℃ at 12 V)and photothermal conversion performance(180.3℃ in 60 s under the near infrared lamp irradiation,up to 57.5℃ under 600 W m^(-2) simulated solar irradiation).Benefiting from high electrical/optical dual-energy conversion efficiency,MFH has a fast photothermal driving effect(bending angle up to 360°in 5 s)due to the different curvature of thermal expansion on both sides of the fabric.Interestingly,MFH has the capability to monitor human strain(such as muscle and joint movements).Based on the above excellent performance,we finally be-lieve that the MFHs have broad application prospects in the fields of all-weather body heat management,health monitoring,thermal health care,and thermal robotics.
基金supported by the Science and Technology Development Fund of Macao SAR(File No.0117/2024/AMJ)the University of Macao(MYRGGRG2023-00041-FST-UMDF,MYRG-GRG2024-00121-FST-UMDF,MYRGCRG2024-00014-FST-ICI).
文摘Achieving autonomously responding to external stimuli and providing real-time feedback on their motion state are key challenges in soft robotics.Herein,we propose an asymmetric three-layer hydrogel muscle with integrated sensing and actuating performances.The actuating layer,made of p(NIPAm-HEMA),features an open pore structure,enabling it to achieve 58%volume shrinkage in just 8 s.The customizable heater allows for efficient programmable deformation of the actuating layer.A strain-responsive hydrogel layer,with a linear response of up to 50%strain,is designed to sense the deformation process.Leveraging these actuating and sensing capabilities,we develop an integrated hydrogel muscle that can recognize lifted objects with various weights or grasped objects of different sizes.Furthermore,we demonstrate a self-crawling robot to showcase the application potential of the hydrogel muscle for soft robots working in aquatic environments.This robot,featuring a modular distributed sensing and actuating layer,can autonomously move forward under closed-loop control based on self-detected resistance signals.The strategy of modular distributed stimuli-responsive sensing and actuating materials offers unprecedented capabilities for creating smart and multifunctional soft robotics.
基金the Science Foundation of China University of Petroleum,Beijing(No.2462019BJRC007)the National Natural Science Foundation of China(No.22178384).
文摘Despite enormous efforts in actuators,most researches are only limited to various actuation behaviors and demonstrations of soft materials.It has not yet been reported to capture and monitor its movement status in an invisible environment.Therefore,it is of great significance to develop a self-sensing and self-actuating dual-function hydrogel actuator system to realize real-time monitoring.Here,we report a bifunctional hydrogel system with self-actuating and self-monitoring abilities,which combines the functions of photothermal actuation and electrical resistance sensing into a single material.The bilayer tough conductive hydrogel synthesized by unconventional complementary concentration recombination and cryogenic freezing technique presents a dense conductive network and high-porosity structure,achieving high toughness at 190.3 kPa of tensile strength,high stretchability(164.3%strain),and the toughness dramatically(1,471.4 kJ·m^(−3)).The working mechanism of the monitoring and self-sensing system is accomplished through the integrated monitoring device of surface temperature–bending angle–electron current,to solve the problem of not apperceiving actuator motion state when encountering obstacles in an invisible environment.We demonstrated for the first time a photothermal actuator’s motion of a football player and goalkeeper to finish the penalty and a soft actuator hand,which can achieve the action of sticking to grab and release under photo-thermal actuation.When connected to the control closed circuit,the actuator realized closed-loop monitoring and sensing feedback.The development of bifunctional hydrogel systems may bring new opportunities and ideas in the fields of material science,circuit technology,sensors,and mechanical engineering.
基金This work was supported by the National Natural Science Foundation of China(Nos.51773039 and 11974076)Natural Science Foundation of Fujian Province(Nos.2020J02036 and 2018J06001)+1 种基金Program for New Century Excellent Talents in University of Fujian Province(No.J1-1318)Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(No.KF201810).
文摘Multifunctionality has become a mainstream trend in the development of smart clothing and flexible wearable devices.Nevertheless,it remains a grand challenge to realize multiple functions,such as sensing,actuating and information displaying,in one single multifunctional material.Here,we present one multifunctional integration strategy by employing monolithic superaligned carbon nanotube(SACNT)composite,which can leverage three different functions through fascinating features of SACNT.Firstly,by using thermochromic dye as a color-memorizing component and SACNT as a photothermal converter,the composite film can be utilized as a flexible rewritable medium.It demonstrates excellent rewriting performances(reversibility>500 times).Secondly,the composite can be tailored to fabricate an actuator,when its length direction is along the SACNT alignment.The actuator shows a bending-morphing when illuminated by near-infrared light.The morphing is attributed to a large difference in volume change between the SACNT and polymer when the SACNT absorbs the optical energy and heats the composite.Thirdly,owing to the unique anisotropy of SACNT,the composite is easily to be stretched in the direction perpendicular to the SACNT alignment,accompanied by a change in electrical resistance.Therefore,the composite is able to be used as a strain sensor.Finally,we fabricate two smart wearable devices to demonstrate the applications,which realize the functions of human-motion detection(sensing)and rewritable information display(rewriting)simultaneously.This multifunctional SACNT composite is expected to have potential applications in the next-generation wearable devices,smart clothing and so on.
基金supported by the National Key R&D Program of China(2017YFA0207800)the National Natural Science Foundation of China(KZ75006801)+2 种基金the National Natural Science Funds for Distinguished Young Scholars(21725401)the 111 Project(B14009)Beijing Technology and Business University 2019 postgraduate research capacity improvement plan.
文摘Anisotropic composite hydrogels have wide applications in the fields of materials for actuators and sensors.Herein,we report an anisotropic composite hydrogel prepared by a mechanical-strain-induced method.Polymer networks including poly(N-isopropylacrylamide)(PNIPAM)and sodium alginate(SA),as well as carbon nanotubes(CNTs)are found to align simultaneously by stretching,and then fixed by physical crosslinking through non-covalent bonds.Composite hydrogels with doubly aligned polymer networks showed anisotropic optical and mechanical properties.The actuation performance of the anisotropic composite hydrogels as compared with the isotropic ones was found to be enhanced,which showed the capability of lifting 100 times its weight with 20%contraction strain.Besides,a bilayer hydrogel was designed to bend with a maximum of 390°to mimic the tendril behavior of plants.
基金supported by the National Natural Science Foundation of China(Nos.52373113 and 52302038)Natural Science Foundation of Fujian Province(Nos.2021J02012 and 2021J01186)Top Young Talents Program of Fujian Province and Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(No.KF202214).
文摘Integrating energy-storage devices(supercapacitors)and shape-deformation devices(actuators)advances the miniaturization and multifunctional development of soft robots.However,soft robots necessitate supercapacitors with high energy-storage performance and actuators with excellent actuation capability.Here,inspired by ant nests,we present a porous structure fabricated by MXene-graphene-methylcellulose(M-GMC)composite,which overcomes the self-stacking of MXene nanosheets and offers a larger specific surface area.The porous structure provides more channels and active sites for electrolyte ions,resulting in high energy storage performance.The areal capacitance of the M-GMC electrode reaches up to 787.9 mF·cm^(−2),significantly superior to that of the pristine MXene electrode(449.1 mF·cm^(−2)).Moreover,the M-GMC/polyethylene bilayer composites with energy storage and multi-responsive actuation functions are developed.The M-GMC is used as the electrode and the polyethylene is used as the encapsulation layer of the quasi-solid-state supercapacitor.Meanwhile,the actuators fabricated by the bilayer composites can be driven by light or low voltage(≤9 V).The maximum bending curvature is up to 5.11 cm^(−1).Finally,a smart gripper and a fully encapsulated smart integrated circuit based on the M-GMC/polyethylene are designed.The smart gripper enables programmable control with multi-stage deformations.The applications realize the intelligence and miniaturization of soft robots.The ant-nest-inspired M-GMC composites would provide a promising development strategy for soft robots and smart integrated devices.
基金supported by the National Natural Science Foundation of China(22171155)Natural Science Foundation of Shandong Province(ZR2022YQ07)Taishan Scholar Program(tsqn202306166).
文摘Transducing thermal energy into mechanical movements via molecular reconfigurations offers a cutting-edge approach to thermal actuating materials,which could be applied to sensors,energy harvesting and storage devices[1].Thermal expansion is a pivotal aspect in solid state chemistry,intricately intertwined with various factors such as crystal structure,chemical composition,electronic configuration,microstructure,and defects.Most materials undergo isotropic and positive thermal expansion(PTE)because of the disharmonic vibrational amplitudes of their chemical bonds.Moreover,anisotropic thermal expansion(ATE)and negative thermal expansion(NTE)are fascinating physical attributes of solids,which can originate from electronic or magnetic mechanisms,as well as through a transverse phonon mechanism in insulating lattice solids.
基金Supported by National Natural Science Foundation of China(NSFC)(Grant No.52130505)Zhejiang Provincial Natural Science Foundation of China(Grant No.LD24E050005)+1 种基金Ningbo Key Scientific and Technological Project of China(Grant No.2022Z040)Academic Excellence Foundation of BUAA for PhD Students.
文摘Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.
基金supported by the National Natural Science Foundation of China(12072090).
文摘This work proposes the application of an iterative learning model predictive control(ILMPC)approach based on an adaptive fault observer(FOBILMPC)for fault-tolerant control and trajectory tracking in air-breathing hypersonic vehicles.In order to increase the control amount,this online control legislation makes use of model predictive control(MPC)that is based on the concept of iterative learning control(ILC).By using offline data to decrease the linearized model’s faults,the strategy may effectively increase the robustness of the control system and guarantee that disturbances can be suppressed.An adaptive fault observer is created based on the suggested ILMPC approach in order to enhance overall fault tolerance by estimating and compensating for actuator disturbance and fault degree.During the derivation process,a linearized model of longitudinal dynamics is established.The suggested ILMPC approach is likely to be used in the design of hypersonic vehicle control systems since numerical simulations have demonstrated that it can decrease tracking error and speed up convergence when compared to the offline controller.
基金research project funded by the National Natural Science Foundation of China(NSFC)under Grant 91948302 and Grant 52021003Research England fund at NERIC.
文摘This paper endeavours to bridge the existing gap in muscular actuator design for ligament-skeletal-inspired robots,thereby fostering the evolution of these robotic systems.We introduce two novel compliant actuators,namely the Internal Torsion Spring Compliant Actuator(ICA)and the External Spring Compliant Actuator(ECA),and present a comparative analysis against the previously conceived Magnet Integrated Soft Actuator(MISA)through computational and experimental results.These actuators,employing a motor-tendon system,emulate biological muscle-like forms,enhancing artificial muscle technology.Then,applications of the proposed actuators in a robotic arm inspired by the human musculoskeletal system are presented.Experiments demonstrate satisfactory power in tasks like lifting dumbbells(peak power:36 W),playing table tennis(end-effector speed:3.2 m/s),and door opening,without compromising biomimetic aesthetics.Compared to other linear stiffness serial elastic actuators(SEAs),ECA and ICA exhibit high power-to-volume(361×10^(3)W/m^(3))and power-to-mass(111.6 W/kg)ratios respectively,endorsing the biomimetic design’s promise in robotic development.
基金financial support from the National Natural Science Foundation of China(Grant No.U1637101)The Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures(1005-ZAG23011).
文摘As a kind of ionic artificial muscle material,Ionic Polymer-Metal Composites(IPMCs)have the advantages of a low drive current,light weight,and significant flexibility.IPMCs are widely used in the fields of biomedicine,soft robots,etc.However,the displacement and blocking force of the traditional sheet-type Nafion-IPMC need to be improved,and it has the limitation of unidirectional actuation.In this paper,a new type of short side chain Aquivion material is used as the polymer in the IPMC.The cylindrical IPMC is prepared by extrusion technology to improve its actuation performance and realize multi-degree-of-freedom motion.In comparison to the traditional Nafion-IPMC,the ion exchange capacity,specific capacitance,and conductivity of Aquivion-IPMC are improved by 28%,27%,and 32%,respectively,and the displacement and blocking force are improved by 57%and 25%,respectively.The cylindrical actuators can be deflected in eight directions.This indicates that Aquivion,as a polymer membrane for IPMC,holds significant application potential.By designing a cylindrical IPMC electrode distribution,the multi-degree-of-freedom deflection of IPMC can be realized.
