Self-propulsion of a deformable ellipse immersed in an unbounded inviscid fluid is discussed in order to explore the effect of the deformation and controlled rotation of the body coupled with the shift of its internal...Self-propulsion of a deformable ellipse immersed in an unbounded inviscid fluid is discussed in order to explore the effect of the deformation and controlled rotation of the body coupled with the shift of its internal mass on the self-motion.The ellipse is capable of symmetric deformation along the two orthogonal axes and endowed with some self-regulation ability via the shift and rotation of its internal mass.From the model,the appropriate velocity potential induced by the motion of the ellipse with the deformation in an otherwise undisturbed fluid is derived,and then the equations of motion are obtained by means of integrals of the unsteady fluid pressure.The equations are utilized to explore self-translational behaviors of the ellipse through the cyclic shift of its internal mass and deformation coupled with its own controllable rotation.Analysis and numerical results show that the ellipse can break the kinematic time-reversal symmetry by properly adjusting its own rotation to coordinate with the deformation and the cyclic shift of the inner mass to meet a forward criterion,and push itself to move persistently forward without a regression at zero system momentum,exhibiting some basic serpentine movements according as the ellipse performs complete revolutions or oscillates between two extreme yaw angles during its self-motion.展开更多
This paper addresses an integrated relative position and attitude control strategy for a pursuer spacecraft flying to a space target in proximity operation missions. Relative translation and rotation dynamics are both...This paper addresses an integrated relative position and attitude control strategy for a pursuer spacecraft flying to a space target in proximity operation missions. Relative translation and rotation dynamics are both presented, and further integratedly considered due to mutual couplings, which results in a six degrees-of-freedom (6-DOF) control system. In order to simultaneously achieve relative position and attitude requirements, an adaptive backstepping control law is designed, where a command filter is introduced to overcome 'explosion of terms'. Within the Lyapunov framework, the proposed controller is proved to ensure the ultimate boundedness of relative position and attitude signals, in the presence of external disturbances and unknown system parameters. Numerical simulation demonstrates the effect of the designed control law.展开更多
With the development of production and science and technology, automatic control is widely used in electronics, electricity and other disciplines, engineering and many other social life fields. The research of automat...With the development of production and science and technology, automatic control is widely used in electronics, electricity and other disciplines, engineering and many other social life fields. The research of automatic control in swimming pool automatic control technology is of great significance. This project adopts Siemens PLC + human-computer interface (touch screen). PLC collects data of field pool level, water temperature, Ph, residual chlorine and other field sensing feedback devices, and displays parameters through human-computer interface. PLC program realizes temperature control, time control and rotation control of the whole process through data processing, so as to realize a closed-loop automatic control system.展开更多
Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a c...Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.展开更多
In an extraction turbine, pressure of the extracted steam and rotate speed of the rotor are two important controlled quantities. The traditional linear state feedback control method is not perfect enough to control th...In an extraction turbine, pressure of the extracted steam and rotate speed of the rotor are two important controlled quantities. The traditional linear state feedback control method is not perfect enough to control the two quantities accurately because of existence of nonlinearity and coupling. A generalized minimum variance control method is studied for an extraction turbine. Firstly, a nonlinear mathematical model of the control system about the two quantities is transformed into a linear system with two white noises. Secondly, a generalized minimum variance control law is applied to the system. A comparative simulation is done. The simulation results indicate that precision and dynamic quality of the regulating system under the new control law are both better than those under the state feedback control law.展开更多
The moving behaviors of a prolate spheroidal complex with the controllable rotation in an ideal fluid without vortex shedding are investigated to find out the self-propelled mechanism of a non-spherical swimmer via th...The moving behaviors of a prolate spheroidal complex with the controllable rotation in an ideal fluid without vortex shedding are investigated to find out the self-propelled mechanism of a non-spherical swimmer via the self-controlled rotation coupled with shift of its internal mass.Based on the model,algebraic velocity vector equations for the complex are derived from the Kirchhoff equations.Several simple cases reveal that the single non-spherical body can push itself to move persistently forward to break the kinematic time-reversal symmetry through coupling the specially-appointed rotation with the corresponding cyclic shift of the internal mass,and some typical self-motion patterns such as trochoids in two dimensions and unidirectional spatial helical motions are identified.The study aims to provide a potential swimming manner of underwater vehicles.展开更多
An improved Narendra model reference adaptive control (MRAC) scheme isproposed to research one variable displacement pump driving four hydraulic variable displacementmotors. This approach not only ensures the underdam...An improved Narendra model reference adaptive control (MRAC) scheme isproposed to research one variable displacement pump driving four hydraulic variable displacementmotors. This approach not only ensures the underdamped and unstable system be global uniformasymptotic stability, but also has good robustness in these aspects of modeling uncertainty,pressure fluctuation of constant pressure network, and disturbance from external load, which alsoupgrades the rapidity of system response so as to make controlled system with nicer dynamic quality.The scheme of one pump driving four motors can meet the demand on off-road mobility of engineeringvehicles and armored cars. A proof of stability about improved Narendra MRAC scheme is also given.展开更多
An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors ar...An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows： （1） The pump is inherently designed as smaller sized and at lower rotational speed. （2） A stable head-characteristic curve for flow rate with negative slope appears. （3） As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows： （1） The structure of double shaft system becomes complex. （2） The pump performance is inferior at over flow rate as the rear rotor loading is weakened. （3） The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.展开更多
Owing to the ubiquity and easy-to-shape property of optical intensity,the intensity gradient force of light has been most spectacularly exploited in optical manipulation.Manifesting the intensity gradient as an optica...Owing to the ubiquity and easy-to-shape property of optical intensity,the intensity gradient force of light has been most spectacularly exploited in optical manipulation.Manifesting the intensity gradient as an optical torque to spin particles is of great fascination on both fundamental and practical sides but remains elusive.Here,we theoretically predict the existence of the optical intensity-gradient torque in the interaction of light with chiral particles.Such a new type of torque derives from the interplay between chirality-induced multipoles,which switches its direction for particles with opposite chirality.We show that this torque can be directly detected by a simple standing wave field,created with the interference of two counterpropagating plane-like waves.Our work offers a unique route to achieve rotational control of matter by tailoring the field intensity of Maxwell waves,demonstrated through three-dimensional spinning of a trapped chiral particle.It also establishes a framework that maps a remarkable connection between the optical forces and torques,across chiral to non-chiral.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11672182).
文摘Self-propulsion of a deformable ellipse immersed in an unbounded inviscid fluid is discussed in order to explore the effect of the deformation and controlled rotation of the body coupled with the shift of its internal mass on the self-motion.The ellipse is capable of symmetric deformation along the two orthogonal axes and endowed with some self-regulation ability via the shift and rotation of its internal mass.From the model,the appropriate velocity potential induced by the motion of the ellipse with the deformation in an otherwise undisturbed fluid is derived,and then the equations of motion are obtained by means of integrals of the unsteady fluid pressure.The equations are utilized to explore self-translational behaviors of the ellipse through the cyclic shift of its internal mass and deformation coupled with its own controllable rotation.Analysis and numerical results show that the ellipse can break the kinematic time-reversal symmetry by properly adjusting its own rotation to coordinate with the deformation and the cyclic shift of the inner mass to meet a forward criterion,and push itself to move persistently forward without a regression at zero system momentum,exhibiting some basic serpentine movements according as the ellipse performs complete revolutions or oscillates between two extreme yaw angles during its self-motion.
基金supported by Innovative Team Program of the National Natural Science Foundation of China (No.61021002)
文摘This paper addresses an integrated relative position and attitude control strategy for a pursuer spacecraft flying to a space target in proximity operation missions. Relative translation and rotation dynamics are both presented, and further integratedly considered due to mutual couplings, which results in a six degrees-of-freedom (6-DOF) control system. In order to simultaneously achieve relative position and attitude requirements, an adaptive backstepping control law is designed, where a command filter is introduced to overcome 'explosion of terms'. Within the Lyapunov framework, the proposed controller is proved to ensure the ultimate boundedness of relative position and attitude signals, in the presence of external disturbances and unknown system parameters. Numerical simulation demonstrates the effect of the designed control law.
文摘With the development of production and science and technology, automatic control is widely used in electronics, electricity and other disciplines, engineering and many other social life fields. The research of automatic control in swimming pool automatic control technology is of great significance. This project adopts Siemens PLC + human-computer interface (touch screen). PLC collects data of field pool level, water temperature, Ph, residual chlorine and other field sensing feedback devices, and displays parameters through human-computer interface. PLC program realizes temperature control, time control and rotation control of the whole process through data processing, so as to realize a closed-loop automatic control system.
基金supported by the National Natural Science Fundation of China(61074031)
文摘Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.
文摘In an extraction turbine, pressure of the extracted steam and rotate speed of the rotor are two important controlled quantities. The traditional linear state feedback control method is not perfect enough to control the two quantities accurately because of existence of nonlinearity and coupling. A generalized minimum variance control method is studied for an extraction turbine. Firstly, a nonlinear mathematical model of the control system about the two quantities is transformed into a linear system with two white noises. Secondly, a generalized minimum variance control law is applied to the system. A comparative simulation is done. The simulation results indicate that precision and dynamic quality of the regulating system under the new control law are both better than those under the state feedback control law.
基金supported by the National Natural Science Foundation of China(Grant No 11672182).
文摘The moving behaviors of a prolate spheroidal complex with the controllable rotation in an ideal fluid without vortex shedding are investigated to find out the self-propelled mechanism of a non-spherical swimmer via the self-controlled rotation coupled with shift of its internal mass.Based on the model,algebraic velocity vector equations for the complex are derived from the Kirchhoff equations.Several simple cases reveal that the single non-spherical body can push itself to move persistently forward to break the kinematic time-reversal symmetry through coupling the specially-appointed rotation with the corresponding cyclic shift of the internal mass,and some typical self-motion patterns such as trochoids in two dimensions and unidirectional spatial helical motions are identified.The study aims to provide a potential swimming manner of underwater vehicles.
文摘An improved Narendra model reference adaptive control (MRAC) scheme isproposed to research one variable displacement pump driving four hydraulic variable displacementmotors. This approach not only ensures the underdamped and unstable system be global uniformasymptotic stability, but also has good robustness in these aspects of modeling uncertainty,pressure fluctuation of constant pressure network, and disturbance from external load, which alsoupgrades the rapidity of system response so as to make controlled system with nicer dynamic quality.The scheme of one pump driving four motors can meet the demand on off-road mobility of engineeringvehicles and armored cars. A proof of stability about improved Narendra MRAC scheme is also given.
文摘An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows： （1） The pump is inherently designed as smaller sized and at lower rotational speed. （2） A stable head-characteristic curve for flow rate with negative slope appears. （3） As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows： （1） The structure of double shaft system becomes complex. （2） The pump performance is inferior at over flow rate as the rear rotor loading is weakened. （3） The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.
基金National Natural Science Foundation of China(12174076,12204117,12274181)National Key Research and Development Program of China(2023YFF0613700)+1 种基金Guangxi Science and Technology Project(2023GXNSFFA026002,2024GXNSFBA010261,2021GXNSFDA196001,AD23026117)Open Project of State Key Laboratory of Surface Physics at Fudan University(KF2022_15).
文摘Owing to the ubiquity and easy-to-shape property of optical intensity,the intensity gradient force of light has been most spectacularly exploited in optical manipulation.Manifesting the intensity gradient as an optical torque to spin particles is of great fascination on both fundamental and practical sides but remains elusive.Here,we theoretically predict the existence of the optical intensity-gradient torque in the interaction of light with chiral particles.Such a new type of torque derives from the interplay between chirality-induced multipoles,which switches its direction for particles with opposite chirality.We show that this torque can be directly detected by a simple standing wave field,created with the interference of two counterpropagating plane-like waves.Our work offers a unique route to achieve rotational control of matter by tailoring the field intensity of Maxwell waves,demonstrated through three-dimensional spinning of a trapped chiral particle.It also establishes a framework that maps a remarkable connection between the optical forces and torques,across chiral to non-chiral.
