Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at s...Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at specific moments during dynamic motion.Although hydraulic actuators can provide a large force,they are relatively inefficient,large,and heavy.Industrial electric actuators are incapable of providing instant high power.In addition,the constant reduction ratio of the reducer makes it difficult to eliminate the tradeoff between high speed and high torque in a given system.This study proposes an explosive electric actuator and an associated control method for legged robots.First,a high-power-density variable transmission is designed to enable continuous adjustment of the output speed to torque ratio.A heat-dissipating structure based on a composite phase-change material(PCM)is used.An integral torque control method is used to achieve periodic and controllable explosive power output.Jumping experiments are conducted with typical legged robots to verify the effectiveness of the proposed actuator and control method.Single-legged,quadruped,and humanoid robots jumped to heights of 1.5,0.8,and 0.5 m,respectively.These are the highest values reported to date for legged robots powered by electric actuators.展开更多
Research on micro-machines is becoming popular.In this paper,the electric driving behavior of liquid metal columns in confining channel was studied.When the electric field was applied,the liquid metal near the negativ...Research on micro-machines is becoming popular.In this paper,the electric driving behavior of liquid metal columns in confining channel was studied.When the electric field was applied,the liquid metal near the negative electrode became flat,longer.The NaOH electrolyte(1.0 mol/L)could flow from the positive electrode to the negative electrode from a small space above the liquid metal column.Besides,the length and volume of the liquid metal would affect its motion and deformation behavior.Both cylindrical liquid column(R=5 mm,L=5 cm)and linear liquid column(R=5 mm,L=40 cm)exhibit deformable movements,which are similar to the bionic movements of earthworms.The electrically driven liquid metal in closed systems could provide a theoretical basis for droplet actuation in microtubes.It has a very wide application prospect in the field of micro-drive machines.展开更多
Subsea development is moving constantly toward simplification,digitalization,and cost-out strategies because the exploration and production of hydrocarbons are moving toward deeper and remote sea water areas.Usage of ...Subsea development is moving constantly toward simplification,digitalization,and cost-out strategies because the exploration and production of hydrocarbons are moving toward deeper and remote sea water areas.Usage of all-electric subsea technology instead of hydraulic technology is growing and will be the future of subsea systems due to the former’s environmental and functional advantages and reduced costs.The benefits of all-electric subsea systems are health,safety,and environment(HSE)and improved reliability,flexibility,and functionality compared with traditional hydraulic-electrical systems.Existing electrohydraulic technology for a typical subsea system,hydraulic and electric actuators,and subsea manifold valves including valve types and selection philosophy have been reviewed in this paper.Some major worldwide oil companies such as Equinor and Schlumberger have successful experiences with subsea electric actuators.Considering the benefits of all-electric technology especially in terms of cost and HSE,as well as successful experiences of two major oil companies,further research in this area is warranted.One of the gaps in existing reviewed literature is the effect of using all-electric actuators for manifold valves.Thus,three main questions related to electric actuator selection,requirement of safety integrity level(SIL),and effect of using electric actuators on manifold valve selection have been addressed and answered.Forty hydraulic actuated manifold valves from nine past subsea projects in different parts of the world,mainly Africa and Australia,have been selected for the analysis of all-electric actuators.Results show that 93%of the valves require spring-return electric actuators,whereas 7%can be operated with conventional electric actuators without any spring.The manifold valves do not require SIL certification because they are not connected to an emergency shut down system.Introducing the electric actuators to the manifold valve will not change the valve selection philosophy.展开更多
Shape-memory polymers(SMPs)are one of the most popular smart materials due to their light weight and high elastic deformation capability.The synergistic effect of carbon nanofiber(CNF)and carbon nanofiber paper(CNFP)o...Shape-memory polymers(SMPs)are one of the most popular smart materials due to their light weight and high elastic deformation capability.The synergistic effect of carbon nanofiber(CNF)and carbon nanofiber paper(CNFP)on the electro-actuation of SMP nanocomposites was studied.The electrical conductivity of SMPs was significantly improved by incorporating CNF and CNFP into them.The dynamic mechanical analysis result reveals good thermal stability of SMP nanocomposites even after they were mixed with CNFs.A vision-based control system is designed to precisely control the shape recovery of SMP composites.Any quasi-state shape between the permanent shape and a temporary shape can be achieved by adjusting the electrical energy input.Experimental results demonstrated that(1)compared with the baseline material,the full recovery time of the SMP nanocomposites was decreased by 1000%to less than 80 s;(2)a good repeatability was shown in the developed vision system in 10 experimental trials and the accuracy of the controlled deflection angle of SMPs was within a 5%error bound.展开更多
To develop self-recovery intelligent components based on resistance heating and obtain satisfactory performance in practical applications,this study optimized the forming quality,dimensional accuracy,and phase transfo...To develop self-recovery intelligent components based on resistance heating and obtain satisfactory performance in practical applications,this study optimized the forming quality,dimensional accuracy,and phase transformation temperatures of Nickel-titanium(NiTi)alloys by controlling the process parameters.The tensile properties and shape-memory effects of the NiTi alloys prepared using the optimized process were clarified.The relationship between the change in temperature and the shape recovery process of the deformed structure under electrical excitation was investigated.The results show that the suitable processing window for ensuring the forming quality without noticeable distortion and macro cracks depends on the laser parameters.In both the X and Y directions,the measured dimensions increased with an increase in laser power and first decreased and then stabilized with an increase in scanning speed.The XRD results showed that all the as-built samples consisted of B2 austenite and B19’martensite phases and Ni3Ti.Mechanical tests suggested that excellent tensile properties with a tensile strength of 753.28 MPa and elongation of 6.81%could be obtained under the optimal parameters of 250 W and 1200 mm/s.An excellent shape-recovery rate of 88.23%was achieved under the optimal parameters.Subsequently,chiral lattice structures were successfully fabricated by laser powder bed fusion(LPBF)under the optimal parameters,and a shape-recovery rate of 96.7%was achieved under electrical actuation for a structure with a pre-compressed strain of 20%.This study also found that the temperatures at the grasp regions were always higher than those at other positions because of the generation of contact resistance at the grasp regions.This facilitates the rapid recovery of the structure at the grasp regions,which has important implications for the design iteration of NiTi smart components.展开更多
Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduc...Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduced into polydimethyl-siloxane(PDMS)elastomer to simultaneously increase the dielectric constant(k)and mechanical properties of PDMS.Then,the in situ thermal reduction of GO@SiO_(2)/PDMS composites was conducted at 180℃ for 2 h to increase the interfacial polariz-ability of GO@SiO_(2).As a result,the values of k at 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO_(2)(RGO@SiO_(2))/PDMS elastomer.Meanwhile,the dielectric loss of the composites remains low(<0.2 at 1000 Hz).More importantly,the actuated strain at low electric field(5 kV/mm)obviously increases from 0.3%for pure PDMS to 2.59%for the composites with 60 phr of RGO@SiO_(2),an eightfold increase in the actuated strain.In addition,both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO_(2),indicating a good reinforcing effect of RGO@SiO_(2) on PDMS.Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application.展开更多
基金supported by the National Key Research Program of China (2018YFB1304500)the National Natural Science Foundation of China (91748202 and 62073041)
文摘Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at specific moments during dynamic motion.Although hydraulic actuators can provide a large force,they are relatively inefficient,large,and heavy.Industrial electric actuators are incapable of providing instant high power.In addition,the constant reduction ratio of the reducer makes it difficult to eliminate the tradeoff between high speed and high torque in a given system.This study proposes an explosive electric actuator and an associated control method for legged robots.First,a high-power-density variable transmission is designed to enable continuous adjustment of the output speed to torque ratio.A heat-dissipating structure based on a composite phase-change material(PCM)is used.An integral torque control method is used to achieve periodic and controllable explosive power output.Jumping experiments are conducted with typical legged robots to verify the effectiveness of the proposed actuator and control method.Single-legged,quadruped,and humanoid robots jumped to heights of 1.5,0.8,and 0.5 m,respectively.These are the highest values reported to date for legged robots powered by electric actuators.
基金Natural Science Foundation of Chongqing(Grant Nos.cstc2019jcyj-msxmX0788,cstc2020jcyj-msxmX0925)Science and Technology Research Program of Chongqing Municipal Education Commission China(Grant Nos.KJQN201901342,KJQN202001317).
文摘Research on micro-machines is becoming popular.In this paper,the electric driving behavior of liquid metal columns in confining channel was studied.When the electric field was applied,the liquid metal near the negative electrode became flat,longer.The NaOH electrolyte(1.0 mol/L)could flow from the positive electrode to the negative electrode from a small space above the liquid metal column.Besides,the length and volume of the liquid metal would affect its motion and deformation behavior.Both cylindrical liquid column(R=5 mm,L=5 cm)and linear liquid column(R=5 mm,L=40 cm)exhibit deformable movements,which are similar to the bionic movements of earthworms.The electrically driven liquid metal in closed systems could provide a theoretical basis for droplet actuation in microtubes.It has a very wide application prospect in the field of micro-drive machines.
文摘Subsea development is moving constantly toward simplification,digitalization,and cost-out strategies because the exploration and production of hydrocarbons are moving toward deeper and remote sea water areas.Usage of all-electric subsea technology instead of hydraulic technology is growing and will be the future of subsea systems due to the former’s environmental and functional advantages and reduced costs.The benefits of all-electric subsea systems are health,safety,and environment(HSE)and improved reliability,flexibility,and functionality compared with traditional hydraulic-electrical systems.Existing electrohydraulic technology for a typical subsea system,hydraulic and electric actuators,and subsea manifold valves including valve types and selection philosophy have been reviewed in this paper.Some major worldwide oil companies such as Equinor and Schlumberger have successful experiences with subsea electric actuators.Considering the benefits of all-electric technology especially in terms of cost and HSE,as well as successful experiences of two major oil companies,further research in this area is warranted.One of the gaps in existing reviewed literature is the effect of using all-electric actuators for manifold valves.Thus,three main questions related to electric actuator selection,requirement of safety integrity level(SIL),and effect of using electric actuators on manifold valve selection have been addressed and answered.Forty hydraulic actuated manifold valves from nine past subsea projects in different parts of the world,mainly Africa and Australia,have been selected for the analysis of all-electric actuators.Results show that 93%of the valves require spring-return electric actuators,whereas 7%can be operated with conventional electric actuators without any spring.The manifold valves do not require SIL certification because they are not connected to an emergency shut down system.Introducing the electric actuators to the manifold valve will not change the valve selection philosophy.
文摘Shape-memory polymers(SMPs)are one of the most popular smart materials due to their light weight and high elastic deformation capability.The synergistic effect of carbon nanofiber(CNF)and carbon nanofiber paper(CNFP)on the electro-actuation of SMP nanocomposites was studied.The electrical conductivity of SMPs was significantly improved by incorporating CNF and CNFP into them.The dynamic mechanical analysis result reveals good thermal stability of SMP nanocomposites even after they were mixed with CNFs.A vision-based control system is designed to precisely control the shape recovery of SMP composites.Any quasi-state shape between the permanent shape and a temporary shape can be achieved by adjusting the electrical energy input.Experimental results demonstrated that(1)compared with the baseline material,the full recovery time of the SMP nanocomposites was decreased by 1000%to less than 80 s;(2)a good repeatability was shown in the developed vision system in 10 experimental trials and the accuracy of the controlled deflection angle of SMPs was within a 5%error bound.
基金National Natural Science Foundation of China(Grant Nos.52225503,U1930207,and 51735005)Basic Strengthening Program of China(Grant No.2019-JCJQ-JJ-331)+1 种基金National Natural Science Foundation of China for Creative Research Groups of China(Grant No.51921003)Postgraduate Research&Practice Innovation Program of Jiangsu Provincial of China(Grant No.KYCX21-0207).
文摘To develop self-recovery intelligent components based on resistance heating and obtain satisfactory performance in practical applications,this study optimized the forming quality,dimensional accuracy,and phase transformation temperatures of Nickel-titanium(NiTi)alloys by controlling the process parameters.The tensile properties and shape-memory effects of the NiTi alloys prepared using the optimized process were clarified.The relationship between the change in temperature and the shape recovery process of the deformed structure under electrical excitation was investigated.The results show that the suitable processing window for ensuring the forming quality without noticeable distortion and macro cracks depends on the laser parameters.In both the X and Y directions,the measured dimensions increased with an increase in laser power and first decreased and then stabilized with an increase in scanning speed.The XRD results showed that all the as-built samples consisted of B2 austenite and B19’martensite phases and Ni3Ti.Mechanical tests suggested that excellent tensile properties with a tensile strength of 753.28 MPa and elongation of 6.81%could be obtained under the optimal parameters of 250 W and 1200 mm/s.An excellent shape-recovery rate of 88.23%was achieved under the optimal parameters.Subsequently,chiral lattice structures were successfully fabricated by laser powder bed fusion(LPBF)under the optimal parameters,and a shape-recovery rate of 96.7%was achieved under electrical actuation for a structure with a pre-compressed strain of 20%.This study also found that the temperatures at the grasp regions were always higher than those at other positions because of the generation of contact resistance at the grasp regions.This facilitates the rapid recovery of the structure at the grasp regions,which has important implications for the design iteration of NiTi smart components.
基金We would like to express our sincere thanks to the National Natural Science Foundation of China[grant number 51173007],[grant number 51103090],[grant number 51221002]for financial support.
文摘Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduced into polydimethyl-siloxane(PDMS)elastomer to simultaneously increase the dielectric constant(k)and mechanical properties of PDMS.Then,the in situ thermal reduction of GO@SiO_(2)/PDMS composites was conducted at 180℃ for 2 h to increase the interfacial polariz-ability of GO@SiO_(2).As a result,the values of k at 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO_(2)(RGO@SiO_(2))/PDMS elastomer.Meanwhile,the dielectric loss of the composites remains low(<0.2 at 1000 Hz).More importantly,the actuated strain at low electric field(5 kV/mm)obviously increases from 0.3%for pure PDMS to 2.59%for the composites with 60 phr of RGO@SiO_(2),an eightfold increase in the actuated strain.In addition,both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO_(2),indicating a good reinforcing effect of RGO@SiO_(2) on PDMS.Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application.
