This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response,...This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one. Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers.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
Shape memory alloy ( SMA) torsion actuator is one of the key approaches realizing adaptive wings in airplanes. In this paper,the actuator is made up of SMA wires and a thin-walled tube,in which the SMA wires are twist...Shape memory alloy ( SMA) torsion actuator is one of the key approaches realizing adaptive wings in airplanes. In this paper,the actuator is made up of SMA wires and a thin-walled tube,in which the SMA wires are twisted and affixed around the surface of the tube at an angle referenced to the center axis of the tube. A thermo-mechanical constitutive model is developed to predict the thermo-mechanical behaviors of the SMA torsion actuator based on the knowledge of solid mechanics. The relationship between the torsion-angle and tem- perature is numerically calculated by using the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. The numerical results are compared with the relative experimental results finished by Xiong and Shen. Influences of the twist-angle of SMA wires and geometrical factors on the primary actuation performances of the SMA torsion actuator are also numerically investigated based on the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. Results show that the thermo-mechanical constitutive model can well predict the thermo-mechanical behaviors of the SMA torsion actuator.展开更多
Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum (r...Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum (recovery) stress. The thermal strain rate of the SMA wires upon heating is more sensitive to the matrix properties than the stress rate does. Additional fibers embedded in the matrix have significant effect on the stress distribution between the SMA wires and the matrix, and thus affect the interface quality significantly. Fibers with negative thermal expansion coefficient are beneficial to the interface between shape memory alloy wires and the epoxy matrix. All conclusions based on the numerical modeling can find experimental supports.展开更多
Over the years, there has been increased research interest in the application of Nitinol as an actuator, due to its shape memory behaviour, simplicity, high power-to-weight ratio, compactness, and extreme high fatigue...Over the years, there has been increased research interest in the application of Nitinol as an actuator, due to its shape memory behaviour, simplicity, high power-to-weight ratio, compactness, and extreme high fatigue resistance to cyclic motion, and noiseless operation. Nitinol has found application in tactile displays which reproduce tactile parameters such as texture and shape, depending on the application. This paper presents the effects of thermal interference between adjacent Nitinol spring actuators in a tactile display. The tactile display is made of a 3 by 3 pin array whose spatial resolution was varied from 4 mm to 6 mm in steps of 1 mm while a current of 1.5 A was used to actuate 8 of the springs, and the centre spring was left unactivated to observe the thermal effects on it due to the heat gradient formed. A Finite Element (FE) model was developed using COMSOL Multiphysics and the results were further verified through experimentation. In both cases, there was visible thermal interference between actuators. The increase in spatial resolution saw a decrease in thermal interference by 12.7%. Using a fan to introduce forced convection, reduced the thermal interference in the simulation by 20% and during experimentation by 11%. The results of this research indicate a spatial resolution of 6 mm reduced the thermal inference to a negligible rate. However, thermal interference could not be eliminated with these two methods.展开更多
The actuation mechanism of TiNi shape memory alloy wires, which were deformed at parent phase followed by a cooling process under constant strain constraint, was investigated. The experimental results show that the tw...The actuation mechanism of TiNi shape memory alloy wires, which were deformed at parent phase followed by a cooling process under constant strain constraint, was investigated. The experimental results show that the two-step reverse martensitic transformation behavior occurs during the heating process, and the temperature range of reverse transformation was obviously widened with the increasing of prestrain. The recovery strain vs temperature curves exhibits an actuation characteristic of linear output recovery strain in a wide temperature range.展开更多
Purpose–The purpose of the current investigation is to design a robust and reliable computational framework to effectively identify the nonlinear behavior of shape memory alloy(SMA)actuators,as one of the most applic...Purpose–The purpose of the current investigation is to design a robust and reliable computational framework to effectively identify the nonlinear behavior of shape memory alloy(SMA)actuators,as one of the most applicable types of actuators in engineering and industry.The motivation of proposing such an intelligent paradigm emanates in the pursuit of fulfilling the necessity of devising a simple yet effective identification system capable of modeling the hysteric dynamical respond of SMA actuators.Design/methodology/approach–To address the requirements of designing a pragmatic identification system,the authors integrate a set of fast yet reliable intelligent methodologies and provide a predictive tool capable of realizing the nonlinear hysteric behavior of SMA actuators in a computationally efficient fashion.First,the authors utilize the governing equations to design a gray box Hammerstein-Wiener identifier model.At the next step,they adopt a computationally efficient metaheuristic algorithm to elicit the optimum operating parameters of the gray box identifier.Findings–Applying the proposed hybrid identifier framework allows the authors to find out its advantages in modeling the behavior of SMA actuator.Through different experiments,the authors conclude that the proposed identifier can be used for identification of highly nonlinear dynamic behavior of SMA actuators.Furthermore,by extending the conclusions and expounding the obtained results,one can easily infer that such a hybrid method may be conveniently applied to model other engineering phenomena that possess dynamic nonlinear reactions.Based on the exerted experiments and implementing the method,the authors come to the conclusion that integrating the power of metaheuristic exploration/exploitation with gray box identifier results a predictive paradigm that much more computationally efficient as compared with black box identifiers such as neural networks.Additionally,the derived gray box method has a higher degree of preference over the black box identifiers,as it allows a manipulated expert to extract the knowledge of the system at hand.Originality/value–The originality of the research paper is twofold.From the practical(engineering)point of view,the authors built a prototype biased-spring SMA actuator and carried out several experiments to ascertain and validate the parameters of the model.From the computational point of view,the authors seek for designing a novel identifier that overcomes the main flaws associated with the performance of black-box identifiers that are the lack of a mean for extracting the governing knowledge of the system at hand,and high computational expense pertinent to the structure of black-box identifiers.展开更多
Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable...Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in complex pipes. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. In the present paper, we propose a globular magnetic actuator group that exhibits a very high thrust force and is capable of free reversible motion in complex pipes. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 29 mm/s in a straight pipe while pulling a load mass of 48 g. In addition, the average speeds for two patterns of movement in a complex pipe with several curved sections and step sections were measured. The prototype actuator group is able to move in a complex pipe at an average speed of over 30 mm/s. This actuator group has several possible applications, including inspection using a micro-camera and pipe maintenance.展开更多
The martensitic phase transformation in Ti_(40.4)Ni_(48)Hf_(11.6) shape memory alloys is leveraged for bi-directional actuation with TiNiHf/SiO_(2)/Si com-posites.The shape memory properties of magnetron sputtered Ti_...The martensitic phase transformation in Ti_(40.4)Ni_(48)Hf_(11.6) shape memory alloys is leveraged for bi-directional actuation with TiNiHf/SiO_(2)/Si com-posites.The shape memory properties of magnetron sputtered Ti_(40.4)Ni_(48)Hf_(11.6) films annealed at 635℃-5 min are influenced by film thickness and the underlying substrate.Decreasing TiNiHf film thick-ness from 21μm to 110 nm results in the reduction of all characteristic transformation temperatures until a critical thickness is reached.Particularly,Ti_(40.4)Ni_(48)Hf_(11.6) thin films as low as 220 nm show transfor-mations above room temperature when deposited on SiO_(2) buffer layer,which is of great interest in nano-actuation.In comparison,220 nm films on Si substrates are austenitic at room temperature,and thus not suitable for actuation.Thermal fatigue tests on TiNiHf/SiO_(2)/Si bimorphs demonstrate better functional fatigue characteristics than freestanding films,with an average reduction of 15℃ after 125 cycles,with tempera-ture stabilization subsequently.Experimental bi-directional actuation results are promising in the development of bistable actuators within a PMMA/TiNiHf/Si trimorph composite,whereby the additional PMMA layer undergoes a glass transition at 105℃.With the aid of constitutive modeling,a route is elaborated on how bistable actuation can be achieved at micro-to nanoscales by showing favorable thickness combinations of PMMA/TiNiHf/Si composite.展开更多
文摘This paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one. Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers.
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Sponsored by the Postdoctoral Science Foundation of China (Grant No. 20080430933)the National Natural Science Foundation of China (Grant No.90505010)
文摘Shape memory alloy ( SMA) torsion actuator is one of the key approaches realizing adaptive wings in airplanes. In this paper,the actuator is made up of SMA wires and a thin-walled tube,in which the SMA wires are twisted and affixed around the surface of the tube at an angle referenced to the center axis of the tube. A thermo-mechanical constitutive model is developed to predict the thermo-mechanical behaviors of the SMA torsion actuator based on the knowledge of solid mechanics. The relationship between the torsion-angle and tem- perature is numerically calculated by using the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. The numerical results are compared with the relative experimental results finished by Xiong and Shen. Influences of the twist-angle of SMA wires and geometrical factors on the primary actuation performances of the SMA torsion actuator are also numerically investigated based on the thermo-mechanical constitutive model coupled with the SMA phase transformation model developed by Zhou and Yoon. Results show that the thermo-mechanical constitutive model can well predict the thermo-mechanical behaviors of the SMA torsion actuator.
文摘Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum (recovery) stress. The thermal strain rate of the SMA wires upon heating is more sensitive to the matrix properties than the stress rate does. Additional fibers embedded in the matrix have significant effect on the stress distribution between the SMA wires and the matrix, and thus affect the interface quality significantly. Fibers with negative thermal expansion coefficient are beneficial to the interface between shape memory alloy wires and the epoxy matrix. All conclusions based on the numerical modeling can find experimental supports.
文摘Over the years, there has been increased research interest in the application of Nitinol as an actuator, due to its shape memory behaviour, simplicity, high power-to-weight ratio, compactness, and extreme high fatigue resistance to cyclic motion, and noiseless operation. Nitinol has found application in tactile displays which reproduce tactile parameters such as texture and shape, depending on the application. This paper presents the effects of thermal interference between adjacent Nitinol spring actuators in a tactile display. The tactile display is made of a 3 by 3 pin array whose spatial resolution was varied from 4 mm to 6 mm in steps of 1 mm while a current of 1.5 A was used to actuate 8 of the springs, and the centre spring was left unactivated to observe the thermal effects on it due to the heat gradient formed. A Finite Element (FE) model was developed using COMSOL Multiphysics and the results were further verified through experimentation. In both cases, there was visible thermal interference between actuators. The increase in spatial resolution saw a decrease in thermal interference by 12.7%. Using a fan to introduce forced convection, reduced the thermal interference in the simulation by 20% and during experimentation by 11%. The results of this research indicate a spatial resolution of 6 mm reduced the thermal inference to a negligible rate. However, thermal interference could not be eliminated with these two methods.
基金FundedbytheNationalNaturalScienceFoundationofChi na (No .5 0 0 710 37)
文摘The actuation mechanism of TiNi shape memory alloy wires, which were deformed at parent phase followed by a cooling process under constant strain constraint, was investigated. The experimental results show that the two-step reverse martensitic transformation behavior occurs during the heating process, and the temperature range of reverse transformation was obviously widened with the increasing of prestrain. The recovery strain vs temperature curves exhibits an actuation characteristic of linear output recovery strain in a wide temperature range.
文摘Purpose–The purpose of the current investigation is to design a robust and reliable computational framework to effectively identify the nonlinear behavior of shape memory alloy(SMA)actuators,as one of the most applicable types of actuators in engineering and industry.The motivation of proposing such an intelligent paradigm emanates in the pursuit of fulfilling the necessity of devising a simple yet effective identification system capable of modeling the hysteric dynamical respond of SMA actuators.Design/methodology/approach–To address the requirements of designing a pragmatic identification system,the authors integrate a set of fast yet reliable intelligent methodologies and provide a predictive tool capable of realizing the nonlinear hysteric behavior of SMA actuators in a computationally efficient fashion.First,the authors utilize the governing equations to design a gray box Hammerstein-Wiener identifier model.At the next step,they adopt a computationally efficient metaheuristic algorithm to elicit the optimum operating parameters of the gray box identifier.Findings–Applying the proposed hybrid identifier framework allows the authors to find out its advantages in modeling the behavior of SMA actuator.Through different experiments,the authors conclude that the proposed identifier can be used for identification of highly nonlinear dynamic behavior of SMA actuators.Furthermore,by extending the conclusions and expounding the obtained results,one can easily infer that such a hybrid method may be conveniently applied to model other engineering phenomena that possess dynamic nonlinear reactions.Based on the exerted experiments and implementing the method,the authors come to the conclusion that integrating the power of metaheuristic exploration/exploitation with gray box identifier results a predictive paradigm that much more computationally efficient as compared with black box identifiers such as neural networks.Additionally,the derived gray box method has a higher degree of preference over the black box identifiers,as it allows a manipulated expert to extract the knowledge of the system at hand.Originality/value–The originality of the research paper is twofold.From the practical(engineering)point of view,the authors built a prototype biased-spring SMA actuator and carried out several experiments to ascertain and validate the parameters of the model.From the computational point of view,the authors seek for designing a novel identifier that overcomes the main flaws associated with the performance of black-box identifiers that are the lack of a mean for extracting the governing knowledge of the system at hand,and high computational expense pertinent to the structure of black-box identifiers.
文摘Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in complex pipes. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. In the present paper, we propose a globular magnetic actuator group that exhibits a very high thrust force and is capable of free reversible motion in complex pipes. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 29 mm/s in a straight pipe while pulling a load mass of 48 g. In addition, the average speeds for two patterns of movement in a complex pipe with several curved sections and step sections were measured. The prototype actuator group is able to move in a complex pipe at an average speed of over 30 mm/s. This actuator group has several possible applications, including inspection using a micro-camera and pipe maintenance.
文摘The martensitic phase transformation in Ti_(40.4)Ni_(48)Hf_(11.6) shape memory alloys is leveraged for bi-directional actuation with TiNiHf/SiO_(2)/Si com-posites.The shape memory properties of magnetron sputtered Ti_(40.4)Ni_(48)Hf_(11.6) films annealed at 635℃-5 min are influenced by film thickness and the underlying substrate.Decreasing TiNiHf film thick-ness from 21μm to 110 nm results in the reduction of all characteristic transformation temperatures until a critical thickness is reached.Particularly,Ti_(40.4)Ni_(48)Hf_(11.6) thin films as low as 220 nm show transfor-mations above room temperature when deposited on SiO_(2) buffer layer,which is of great interest in nano-actuation.In comparison,220 nm films on Si substrates are austenitic at room temperature,and thus not suitable for actuation.Thermal fatigue tests on TiNiHf/SiO_(2)/Si bimorphs demonstrate better functional fatigue characteristics than freestanding films,with an average reduction of 15℃ after 125 cycles,with tempera-ture stabilization subsequently.Experimental bi-directional actuation results are promising in the development of bistable actuators within a PMMA/TiNiHf/Si trimorph composite,whereby the additional PMMA layer undergoes a glass transition at 105℃.With the aid of constitutive modeling,a route is elaborated on how bistable actuation can be achieved at micro-to nanoscales by showing favorable thickness combinations of PMMA/TiNiHf/Si composite.
