The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and inte...The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and interaction forces of cationic surfactants at solid-solution interfaces were measured in tapping mode and Pico Force mode, respectively. The images demonstrated that the adsorbed structure was varied by a variety of surfactant concentrations. The adsorbed layer on mica was monolayer at first, and then became bilayer. A striped adsorbed structure was observed in a higher concentration of CTAC,which could not be found in any other concentrations of DTAC. For force measurements, the repulsive force was exponentially decreasing with the concentration increasing till a net attractive force appeared. A largest attractive force could be observed at a certain concentration, which was close to the point of charge neutralization. The results also showed a significant impact of hydrocarbon chain length on adsorption. An adsorption simulation was established to give a clear understanding of the interaction between cationic surfactants and mica.展开更多
The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation ...The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation genetic algorithm （MPGA） based on real coding that can contemporarily process the data of free running model and simulation of ship maneuvering was applied to solve the problem. Accordingly the optimal individual was obtained using the method of genetic algorithm. The parallel processing of multiopulation solved the prematurity in the identification for single population, meanwhile, the parallel processing of the data of ship maneuvering （turning motion and zigzag motion） is an attempt to solve the coefficient drift problem. In order to validate the method, the interaction force coefficients were verified by the procedure and these coefficients measured were compared with those ones identified. The maximum error is less than 5%, and the identification is an effective method.展开更多
It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening co...It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,wake fraction coefficients are larger for the large drafts,however,become small as the trims increase. The resistance is obviously different in fully loaded condition with the trims by stern,however ,the difference is not evident when the draft decreases and the bulbous bow is above the water surface.展开更多
The discrete element method(DEM)model calculates interaction forces between each pair of particles.However,it becomes computational expensive especially when the number of particles is large.In this study,a novel arti...The discrete element method(DEM)model calculates interaction forces between each pair of particles.However,it becomes computational expensive especially when the number of particles is large.In this study,a novel artificial neural network(ANN)model is proposed to replace the model of interaction forces between multiple particles in DEM including contact force and electrostatic force.The ANN model combines the residual network(ResNet)with the physics informed neural network(PINN).The physical loss term is derived from the Newton's third law about internal forces in multi-particle system.The performance of the ANN model is evaluated based on the DEM simulation data of 100,200,and 300-particle system in a wall-bounded 2D swirling flow.It is found that the computing time is reduced nearly an order of magnitude(7–10 times)compared with the DEM model.In addition,the accuracy of the ANN model achieves the R^(2)>0.93 with only≤2%particles are not well predicted.展开更多
Robot teleoperation plays an important role in industrial manufacturing in unknown and dangerous environments beyond human reach.In telerobotic manufacturing tasks,environmental interaction forces may vary significant...Robot teleoperation plays an important role in industrial manufacturing in unknown and dangerous environments beyond human reach.In telerobotic manufacturing tasks,environmental interaction forces may vary significantly from task to task.Therefore,it is crucial to provide operators with the specific proportional feedback of environmental interaction forces to enhance their environmental awareness and manipulation capabilities.However,variable time delays and various scales of environmental interaction force feedback seriously affect the system stability,which should be rigorously addressed when designing control parameters.To cope with these difficulties,a position and scaled force tracking control framework is proposed and the LyapunovKrasovskii theory is used to obtain a simple algebraic stability criterion with the scaling factor of the environmental interaction force feedback.In addition,a low-pass filter-based radial basis function neural network is designed to avoid the effect of the measurement noise and the sudden change of the non-passive environmental interaction force on the system stability.Compared with different controllers in various telerobotic manufacturing tasks such as heavy lifting,cutting,and polishing,our proposed method achieves better position and scaled force tracking performance.展开更多
Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally ...Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally derived from monodisperse systems, with ad hoc modifications to account for polydispersity. In previous work it was shown that for bidisperse systems with moderate diameter ratios of 1：2 to 1：4, this approach leads to discrepancies, and a correction factor is needed. In this work we demonstrate that this correction factor also holds for more extreme diameter ratios of 1：5, 1：7 and 1： 10, although the force on the large particles is slightly overestimated when using the correction factor. The main origin of the correction is that the void surrounding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.展开更多
Exoskeleton robots and their control methods have been extensively developed to aid post-stroke rehabilitation. Most of the existing methods using linear controllers are designed for position control and are not suita...Exoskeleton robots and their control methods have been extensively developed to aid post-stroke rehabilitation. Most of the existing methods using linear controllers are designed for position control and are not suitable for human-machine interaction(HMI) force control, as the interaction system between the human body and exoskeleton is uncertain and nonlinear. We present an approach for HMI force control via model reference adaptive impedance control(MRAIC) to solve this problem in case of index finger exoskeleton control. First, a dynamic HMI model, which is based on a position control inner loop, is formulated. Second, the theoretical MRAC framework is implemented in the control system. Then, the adaptive controllers are designed according to the Lyapunov stability theory. To verify the performance of the proposed method, we compare it with a proportional-integral-derivative(PID) method in the time domain with real experiments and in the frequency domain with simulations. The results illustrate the effectiveness and robustness of the proposed method in solving the nonlinear HMI force control problem in hand exoskeleton.展开更多
In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed t...In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed that force relationships based on Lattice-Boltzmann simulations did not perform as well as other inter- action types tested. Nonetheless, it is apparent that, in the case of a suspension of different particle types, it is important that the correct choice is made as to how the contribution to the overall fluid-particle interaction force is split between buoyancy and drag. Experimental evidence clearly suggests that the ＂generalized＂ Archimedes＇ principle （where the foreign particle is considered to displace the whole suspension and not just the fluid） provides the best result.展开更多
The existing fixed gait lower limb rehabilitation robots perform a predetermined walking trajectory for patients,ignoring their residual muscle strength.To enhance patient participation and safety in training,this pap...The existing fixed gait lower limb rehabilitation robots perform a predetermined walking trajectory for patients,ignoring their residual muscle strength.To enhance patient participation and safety in training,this paper aims to develop a lower limb rehabilitation robot with adaptive gait training capability relying on human–robot interaction force measurement.Firstly,a novel lower limb rehabilitation robot system with several active and passive driven joints is developed,and 2 face-to-face mounted cantilever beam force sensors are employed to measure the human–robot interaction forces.Secondly,a dynamic model of the rehabilitation training robot is constructed to estimate the driven forces of the human lower leg in a completely passive state.Thereafter,based on the theoretical moment from the dynamics and the actual joint interaction force collected by the sensors,an adaptive gait adjustment method is proposed to achieve the goal of adapting to the wearer’s movement intention.Finally,interactive experiments are carried out to validate the effectiveness of the developed rehabilitation training robot system.The proposed rehabilitation training robot system with adaptive gaits offers great potential for future highquality rehabilitation training,e.g.,improving participation and safety.展开更多
Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there ...Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.展开更多
Swift perception of interaction forces is a crucial skill required for legged robots to ensure safe human-robot interaction and dynamic contact management.Proprioceptive-based interactive force is widely applied due t...Swift perception of interaction forces is a crucial skill required for legged robots to ensure safe human-robot interaction and dynamic contact management.Proprioceptive-based interactive force is widely applied due to its outstanding cross-platform versatility.In this paper,we present a novel interactive force observer,which possesses superior dynamic tracking performance.We propose a dynamic cutoff frequency configuration method to replace the conventional fixed cutoff frequency setting in the traditional momentum-based observer(MBO).This method achieves a balance between rapid tracking and noise suppression.Moreover,to mitigate the phase lag introduced by the low-pass filtering,we cascaded a Newton Predictor(NP)after MBO,which features simple computation and adaptability.The precision analysis of this method has been presented.We conducted extensive experiments on the point-foot biped robot BRAVER to validate the performance of the proposed algorithm in both simulation and physical prototype.展开更多
To develop sophisticated and efficient control strategies for exoskeleton devices,acquiring the information of interaction forces between the wearer and the wearable device is essential.However,obtaining the interacti...To develop sophisticated and efficient control strategies for exoskeleton devices,acquiring the information of interaction forces between the wearer and the wearable device is essential.However,obtaining the interaction force via conventional methods,such as direct measurement using force sensors,is problematic.This paper proposes a kinematic data-based estimation method to evaluate the interaction force between human lower limbs and passive exoskeleton links during level ground walking.Unlike conventional methods,the proposed method requires no force sensors and is computationally cheaper to obtain the calculation results.To obtain more accurate kinematic data,a marker refinement algorithm based on bilevel optimization framework is adopted.The interaction force is evaluated by a spring model,which is used to imitate the binding behavior between human limbs and the exoskeleton links.The deflection of the spring model is calculated based on the assumption that the phase delay between human limb and exoskeleton link can be presented by the sequence of frames of kinematic data.Experimental results of six subjects indicate that our proposed method can estimate the interaction forces during level ground walking.Moreover,a case study of bandage location optimization is conducted to demonstrate the usefulness of obtaining the interaction information.展开更多
The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force betwe...The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency.In this paper,based on the extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory,the van der Waals,electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first,and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration,mineral particle size,air bubble size,collector type(dodecylamine hydrochloride(DAH)and sodium oleate(NaOL))and concentration,and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles.The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution.The increase in electrolyte concentration reduced the interaction force or even changed the direction of the force under certain circumstances.The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinitebubble and diaspore-bubble respectively.Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values.The research results have theoretical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.展开更多
Understanding the regulatory mechanism of self-assembly processes is a necessity to modulate nanostructures and their properties. Herein, we have studied the mechanism of self-assembly in the C3 symmetric 1,3,5-benzen...Understanding the regulatory mechanism of self-assembly processes is a necessity to modulate nanostructures and their properties. Herein, we have studied the mechanism of self-assembly in the C3 symmetric 1,3,5-benzentricarboxylic amino acid methyl ester enantiomers(TPE) in a mixed solvent system consisting of methanol and water. The resultant chiral structure was used for chiral recognition. The formation of chiral structures from the synergistic effect of multiple noncovalent interaction forces was confirmed by various techniques. Molecular dynamics simulations were used to characterize the time evolution of TPE structure and properties in solution. The theoretical results were consistent with the experimental results. Furthermore, the chiral structure assembled by the building blocks of TPE molecules was highly stereoselective for diamine compounds.展开更多
Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonablenes...Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.展开更多
A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test cas...A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.展开更多
Dear Editor,This letter proposes a novel Nash bargaining solution-based multiobjective model predictive control(MPC)scheme to deal with the interaction force control and the path-following problem of the constrained i...Dear Editor,This letter proposes a novel Nash bargaining solution-based multiobjective model predictive control(MPC)scheme to deal with the interaction force control and the path-following problem of the constrained interactive robot.Considering the elastic interaction force model,a mechanical trade-off always exists between the interaction force and position,which means that neither force nor path following can satisfy their desired demands completely.Based on this consideration,two irreconcilable control specifications,the force object function and the position track object function,are proposed,and a new multi-objective MPC scheme is then designed.展开更多
In the past three decades, numerous papers have bee n publishedon the dynamics of rotating discs. most of them have focused on the ma thematical modeling and solution for a specific interactive force, such as a n elas...In the past three decades, numerous papers have bee n publishedon the dynamics of rotating discs. most of them have focused on the ma thematical modeling and solution for a specific interactive force, such as a n elastic force produced by a stationary spring or a damping force from a statio nary viscous damper. Few of them have looked into the instability mechanisms. This study has established a generalized approach to investigate the instability mechanisms that are involved in the interaction between a rotating and an arbit rary interactive force. An energy flux equation has been developed, which leads to the following conclusions: (1) The possibility of the occurrence of instability due to any interactive forc es may be identified based on the energy flux analysis, even without solving equ ations. (2) Instabilities will occur if the interactive forces are in phase with the vel ocity measured at the interactive point from the coordinates rotating with the d isc. (3) Instability cannot occur when a rotating disc is subjected to a stationary c onstant lateral force, but a stationary harmonic lateral force, a moving constan t lateral force or a moving harmonic lateral force may cause instability. (4) Conservative forces may only cause coupling instability associated with two modes, and non-conservative forces usually cause terminal instability where onl y one mode is involved.展开更多
Studies of interactions between wind and saltating particles （i.e., the wind-saltation interaction） are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with l...Studies of interactions between wind and saltating particles （i.e., the wind-saltation interaction） are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with limited size, this gradient is required to maintain the movement of the saltation cloud. Attempts are made to investigate the effects of the downwind air pressure gradient on the wind-saltation interaction in a saltation boundary layer based on the experimental results from a wind tunnel with a relatively small cross-sectional area. The wind-saltation interaction is characterized by airborne stress, grain-borne stress, and the force exerted on the wind by the saltation cloud. Basic equations were developed for wind-saltation interactions without and with a downwind air pressure gradient. The results reveal that unacceptable values of negative grain-borne stress and negative force exerted on the wind by the saltation cloud are obtained if the downwind air pressure gradient is ignored. When this air pressure gradient is defined using the measured wind velocity profiles in the presence of saltation and the downwind air pressure gradient is taken into account, reasonable values for grain-borne stress and the force exerted on the wind by the saltation cloud are obtained. These results suggest that attention must be paid to the effects of downwind air pressure gradients when studying the wind-saltation interaction in a wind tunnel. Consideration of the downwind air pressure gradient, inertial forces, and other unidentified variables will provide a more thorough understanding of the interactions within a saltation boundary layer.展开更多
There is an intrinsic traction force in the technological development which has various manifestations. It is from nonlinear interaction that occurs among the essential elements of technology and among the relevant te...There is an intrinsic traction force in the technological development which has various manifestations. It is from nonlinear interaction that occurs among the essential elements of technology and among the relevant technology. It is not the only decisive factor but to interweave with other tensions in the development of technology.展开更多
基金Project(50974134)supported by the National Natural Science Foundation of China
文摘The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and interaction forces of cationic surfactants at solid-solution interfaces were measured in tapping mode and Pico Force mode, respectively. The images demonstrated that the adsorbed structure was varied by a variety of surfactant concentrations. The adsorbed layer on mica was monolayer at first, and then became bilayer. A striped adsorbed structure was observed in a higher concentration of CTAC,which could not be found in any other concentrations of DTAC. For force measurements, the repulsive force was exponentially decreasing with the concentration increasing till a net attractive force appeared. A largest attractive force could be observed at a certain concentration, which was close to the point of charge neutralization. The results also showed a significant impact of hydrocarbon chain length on adsorption. An adsorption simulation was established to give a clear understanding of the interaction between cationic surfactants and mica.
基金the Knowledge-based Ship-designHyper-integrated Platform (KSHIP) of Ministry ofEducation, China
文摘The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation genetic algorithm （MPGA） based on real coding that can contemporarily process the data of free running model and simulation of ship maneuvering was applied to solve the problem. Accordingly the optimal individual was obtained using the method of genetic algorithm. The parallel processing of multiopulation solved the prematurity in the identification for single population, meanwhile, the parallel processing of the data of ship maneuvering （turning motion and zigzag motion） is an attempt to solve the coefficient drift problem. In order to validate the method, the interaction force coefficients were verified by the procedure and these coefficients measured were compared with those ones identified. The maximum error is less than 5%, and the identification is an effective method.
基金the Foundation Item "Knowledge-based Ship-design Hyper-integrated Platform(KSHIP)" of Ministry of Education of China
文摘It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,wake fraction coefficients are larger for the large drafts,however,become small as the trims increase. The resistance is obviously different in fully loaded condition with the trims by stern,however ,the difference is not evident when the draft decreases and the bulbous bow is above the water surface.
基金support from National Natural Science Foundation of China(grant No.22308212)Science and Technology Innovation Committee of Shenzhen Municipality(grant Nos.RCBS 20200714114910354,JCYJ 20220530141016036)the fruitful discussion with Dr.Jerol Soibam from Malardalen University.
文摘The discrete element method(DEM)model calculates interaction forces between each pair of particles.However,it becomes computational expensive especially when the number of particles is large.In this study,a novel artificial neural network(ANN)model is proposed to replace the model of interaction forces between multiple particles in DEM including contact force and electrostatic force.The ANN model combines the residual network(ResNet)with the physics informed neural network(PINN).The physical loss term is derived from the Newton's third law about internal forces in multi-particle system.The performance of the ANN model is evaluated based on the DEM simulation data of 100,200,and 300-particle system in a wall-bounded 2D swirling flow.It is found that the computing time is reduced nearly an order of magnitude(7–10 times)compared with the DEM model.In addition,the accuracy of the ANN model achieves the R^(2)>0.93 with only≤2%particles are not well predicted.
基金supported by the National Natural Science Foundation of China(Grant Nos.52188102,52105515,62373161)。
文摘Robot teleoperation plays an important role in industrial manufacturing in unknown and dangerous environments beyond human reach.In telerobotic manufacturing tasks,environmental interaction forces may vary significantly from task to task.Therefore,it is crucial to provide operators with the specific proportional feedback of environmental interaction forces to enhance their environmental awareness and manipulation capabilities.However,variable time delays and various scales of environmental interaction force feedback seriously affect the system stability,which should be rigorously addressed when designing control parameters.To cope with these difficulties,a position and scaled force tracking control framework is proposed and the LyapunovKrasovskii theory is used to obtain a simple algebraic stability criterion with the scaling factor of the environmental interaction force feedback.In addition,a low-pass filter-based radial basis function neural network is designed to avoid the effect of the measurement noise and the sudden change of the non-passive environmental interaction force on the system stability.Compared with different controllers in various telerobotic manufacturing tasks such as heavy lifting,cutting,and polishing,our proposed method achieves better position and scaled force tracking performance.
基金funded by the Nederlandse Organisatievoor Wetenschappelijk Onderzoek(Netherlands Organization forScientific Research,NWO)
文摘Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally derived from monodisperse systems, with ad hoc modifications to account for polydispersity. In previous work it was shown that for bidisperse systems with moderate diameter ratios of 1：2 to 1：4, this approach leads to discrepancies, and a correction factor is needed. In this work we demonstrate that this correction factor also holds for more extreme diameter ratios of 1：5, 1：7 and 1： 10, although the force on the large particles is slightly overestimated when using the correction factor. The main origin of the correction is that the void surrounding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.
基金Project supported by the National Natural Science Foundation of China(No.51221004)
文摘Exoskeleton robots and their control methods have been extensively developed to aid post-stroke rehabilitation. Most of the existing methods using linear controllers are designed for position control and are not suitable for human-machine interaction(HMI) force control, as the interaction system between the human body and exoskeleton is uncertain and nonlinear. We present an approach for HMI force control via model reference adaptive impedance control(MRAIC) to solve this problem in case of index finger exoskeleton control. First, a dynamic HMI model, which is based on a position control inner loop, is formulated. Second, the theoretical MRAC framework is implemented in the control system. Then, the adaptive controllers are designed according to the Lyapunov stability theory. To verify the performance of the proposed method, we compare it with a proportional-integral-derivative(PID) method in the time domain with real experiments and in the frequency domain with simulations. The results illustrate the effectiveness and robustness of the proposed method in solving the nonlinear HMI force control problem in hand exoskeleton.
文摘In this work several relationships governing solid-fluid dynamic interaction forces were validated against experimental data for a single particle settling in a suspension of other smaller particles. It was observed that force relationships based on Lattice-Boltzmann simulations did not perform as well as other inter- action types tested. Nonetheless, it is apparent that, in the case of a suspension of different particle types, it is important that the correct choice is made as to how the contribution to the overall fluid-particle interaction force is split between buoyancy and drag. Experimental evidence clearly suggests that the ＂generalized＂ Archimedes＇ principle （where the foreign particle is considered to displace the whole suspension and not just the fluid） provides the best result.
基金supported in part by the National Natural Science Foundation of China under Grants 62373353,and 62033013in part by Youth Innovation Promotion Association CAS(2019138).
文摘The existing fixed gait lower limb rehabilitation robots perform a predetermined walking trajectory for patients,ignoring their residual muscle strength.To enhance patient participation and safety in training,this paper aims to develop a lower limb rehabilitation robot with adaptive gait training capability relying on human–robot interaction force measurement.Firstly,a novel lower limb rehabilitation robot system with several active and passive driven joints is developed,and 2 face-to-face mounted cantilever beam force sensors are employed to measure the human–robot interaction forces.Secondly,a dynamic model of the rehabilitation training robot is constructed to estimate the driven forces of the human lower leg in a completely passive state.Thereafter,based on the theoretical moment from the dynamics and the actual joint interaction force collected by the sensors,an adaptive gait adjustment method is proposed to achieve the goal of adapting to the wearer’s movement intention.Finally,interactive experiments are carried out to validate the effectiveness of the developed rehabilitation training robot system.The proposed rehabilitation training robot system with adaptive gaits offers great potential for future highquality rehabilitation training,e.g.,improving participation and safety.
基金supported by the National Natural Science Foundation of China(Nos.62271238,22372074,62301240)Yunnan Fundamental Research Projects(Nos.202201AT070078,202201BE070001-009 and 202301AW070017)+2 种基金the Major Basic Research Project of Science and Technology of Yunnan(202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(202305AS350017)Graphene Application and Engineering Research Centre of Education Department of Yunnan Providence(KKPP202351001).
文摘Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.
基金supported in part by the National Key Research and Development Program of China(2022YFB4701504)the National Natural Science Foundation of China(62373223 and 62203268)Youth Innovation and Technology Support Plan for Higher Education Institutions in Shandong Province(2023KJ029).
文摘Swift perception of interaction forces is a crucial skill required for legged robots to ensure safe human-robot interaction and dynamic contact management.Proprioceptive-based interactive force is widely applied due to its outstanding cross-platform versatility.In this paper,we present a novel interactive force observer,which possesses superior dynamic tracking performance.We propose a dynamic cutoff frequency configuration method to replace the conventional fixed cutoff frequency setting in the traditional momentum-based observer(MBO).This method achieves a balance between rapid tracking and noise suppression.Moreover,to mitigate the phase lag introduced by the low-pass filtering,we cascaded a Newton Predictor(NP)after MBO,which features simple computation and adaptability.The precision analysis of this method has been presented.We conducted extensive experiments on the point-foot biped robot BRAVER to validate the performance of the proposed algorithm in both simulation and physical prototype.
基金This work was supported in part by the National Natural Science Foundation of China under grant nos.61603284 and 61903286.
文摘To develop sophisticated and efficient control strategies for exoskeleton devices,acquiring the information of interaction forces between the wearer and the wearable device is essential.However,obtaining the interaction force via conventional methods,such as direct measurement using force sensors,is problematic.This paper proposes a kinematic data-based estimation method to evaluate the interaction force between human lower limbs and passive exoskeleton links during level ground walking.Unlike conventional methods,the proposed method requires no force sensors and is computationally cheaper to obtain the calculation results.To obtain more accurate kinematic data,a marker refinement algorithm based on bilevel optimization framework is adopted.The interaction force is evaluated by a spring model,which is used to imitate the binding behavior between human limbs and the exoskeleton links.The deflection of the spring model is calculated based on the assumption that the phase delay between human limb and exoskeleton link can be presented by the sequence of frames of kinematic data.Experimental results of six subjects indicate that our proposed method can estimate the interaction forces during level ground walking.Moreover,a case study of bandage location optimization is conducted to demonstrate the usefulness of obtaining the interaction information.
基金supported by the National Natural Science Foundation of China(No.51904240,51904239,52104268)the Natural Science Foundation of Shaanxi Province(No.2020JQ-752,2021JQ-571)+3 种基金the Postdoctoral Science Foundation of China(No.2019M653877XB)the Outstanding Youth Science Foundation of Xi’an University of Science and Technology(No.2019YQ3-08)the Huo Yingdong Education Foundation(No.171102)the 2019 Merit-based Science and Technology Project Foundation for Shannxi Overseas-educated Scholars(No.14).
文摘The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency.In this paper,based on the extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory,the van der Waals,electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first,and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration,mineral particle size,air bubble size,collector type(dodecylamine hydrochloride(DAH)and sodium oleate(NaOL))and concentration,and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles.The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution.The increase in electrolyte concentration reduced the interaction force or even changed the direction of the force under certain circumstances.The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinitebubble and diaspore-bubble respectively.Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values.The research results have theoretical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.
基金supported by the National Natural Science Foundation of China(No.21962003)the Natural Science Foundation of Jiangsu Province(No.BK20190056)the“Fundamental Research Funds for the Central Universities”(No.021514380014)。
文摘Understanding the regulatory mechanism of self-assembly processes is a necessity to modulate nanostructures and their properties. Herein, we have studied the mechanism of self-assembly in the C3 symmetric 1,3,5-benzentricarboxylic amino acid methyl ester enantiomers(TPE) in a mixed solvent system consisting of methanol and water. The resultant chiral structure was used for chiral recognition. The formation of chiral structures from the synergistic effect of multiple noncovalent interaction forces was confirmed by various techniques. Molecular dynamics simulations were used to characterize the time evolution of TPE structure and properties in solution. The theoretical results were consistent with the experimental results. Furthermore, the chiral structure assembled by the building blocks of TPE molecules was highly stereoselective for diamine compounds.
文摘Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.
文摘A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.
基金supported by the National Natural Science Foundation of China(62303095)the Natural Science Foundation of Sichuan Province(2023NSFSC0872).
文摘Dear Editor,This letter proposes a novel Nash bargaining solution-based multiobjective model predictive control(MPC)scheme to deal with the interaction force control and the path-following problem of the constrained interactive robot.Considering the elastic interaction force model,a mechanical trade-off always exists between the interaction force and position,which means that neither force nor path following can satisfy their desired demands completely.Based on this consideration,two irreconcilable control specifications,the force object function and the position track object function,are proposed,and a new multi-objective MPC scheme is then designed.
文摘In the past three decades, numerous papers have bee n publishedon the dynamics of rotating discs. most of them have focused on the ma thematical modeling and solution for a specific interactive force, such as a n elastic force produced by a stationary spring or a damping force from a statio nary viscous damper. Few of them have looked into the instability mechanisms. This study has established a generalized approach to investigate the instability mechanisms that are involved in the interaction between a rotating and an arbit rary interactive force. An energy flux equation has been developed, which leads to the following conclusions: (1) The possibility of the occurrence of instability due to any interactive forc es may be identified based on the energy flux analysis, even without solving equ ations. (2) Instabilities will occur if the interactive forces are in phase with the vel ocity measured at the interactive point from the coordinates rotating with the d isc. (3) Instability cannot occur when a rotating disc is subjected to a stationary c onstant lateral force, but a stationary harmonic lateral force, a moving constan t lateral force or a moving harmonic lateral force may cause instability. (4) Conservative forces may only cause coupling instability associated with two modes, and non-conservative forces usually cause terminal instability where onl y one mode is involved.
基金the funding received from the Natural Science Foundation of China (40638038)
文摘Studies of interactions between wind and saltating particles （i.e., the wind-saltation interaction） are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with limited size, this gradient is required to maintain the movement of the saltation cloud. Attempts are made to investigate the effects of the downwind air pressure gradient on the wind-saltation interaction in a saltation boundary layer based on the experimental results from a wind tunnel with a relatively small cross-sectional area. The wind-saltation interaction is characterized by airborne stress, grain-borne stress, and the force exerted on the wind by the saltation cloud. Basic equations were developed for wind-saltation interactions without and with a downwind air pressure gradient. The results reveal that unacceptable values of negative grain-borne stress and negative force exerted on the wind by the saltation cloud are obtained if the downwind air pressure gradient is ignored. When this air pressure gradient is defined using the measured wind velocity profiles in the presence of saltation and the downwind air pressure gradient is taken into account, reasonable values for grain-borne stress and the force exerted on the wind by the saltation cloud are obtained. These results suggest that attention must be paid to the effects of downwind air pressure gradients when studying the wind-saltation interaction in a wind tunnel. Consideration of the downwind air pressure gradient, inertial forces, and other unidentified variables will provide a more thorough understanding of the interactions within a saltation boundary layer.
文摘There is an intrinsic traction force in the technological development which has various manifestations. It is from nonlinear interaction that occurs among the essential elements of technology and among the relevant technology. It is not the only decisive factor but to interweave with other tensions in the development of technology.
