A comprehensive review on bio-inspired fish robots has been done in this article with an enhanced focus on swimming styles,actuators,hydrodynamics,kinematic-dynamic modeling,and controllers.Swimming styles such as bod...A comprehensive review on bio-inspired fish robots has been done in this article with an enhanced focus on swimming styles,actuators,hydrodynamics,kinematic-dynamic modeling,and controllers.Swimming styles such as body and/or caudal fin and median and/or paired fin and their variants are discussed in detail.Literature shows that most fish robots adapt carangiform in body and/or caudal fin type swimming as it gives significant thrust with a maximum speed of 3.7 ms 1 in iSplash-II.Applications of smart or soft actuators to enhance real-time dynamics was studied from literature,and it was found that the robot built with polymer fiber composite material could reach a speed of 0.6 m s However,dynamic modeling is relatively complex,and material selection needs to be explored.The numerical and analytical methods in dynamic modeling have been investigated highlighting merits and demerits.Hydrodynamic parameter estimation through the data-driven model is widely used in offline,however online estimation of the same need to be explored.Classical controllers are frequently used tor navigation and stabilization,which often encounters the linearization problem and hence,can be replaced with the state-of-the-art adaptive and intelligent controller.This article also summarizes the potential research gaps and future scopes.展开更多
This article describes an experimental prototype flying fish II and builds a dynamic model that is a novel type of autonomous underwater vehicle(AUV)under the condition of negative buoyancy vehicle(NBV) without large ...This article describes an experimental prototype flying fish II and builds a dynamic model that is a novel type of autonomous underwater vehicle(AUV)under the condition of negative buoyancy vehicle(NBV) without large buoyancy mechanism.Compared with the AUV Remus 100,the flying fish II can cruise with double speeds within the same range and dimensions.The static stability and motion modes of flying fish II in the longitudinal plane are analyzed through the linear system theory.The flying fish II has static stability in the longitudinal plane and the motion mode is related to metacentric height.展开更多
Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can inve...Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can investigate the effects of the clearances on the dynamics of the multibody system. A revolute joint with clearance exhibits three motions which are;free-flight, impact and continuous contact motion modes. Therefore, a multibody system with n-number of revolute clearance joints will exhibit 3n motion modes which are a combination of the three motions in each joint. This study investigates experimentally the nine motion modes in a mechanical system with two revolute clearance joints. A slider crank mechanism has been used as the demonstrative example. We observed that the experimental curve exhibits a greater impact compared to the simulation curve. In conclusion, this experimental investigation offers valuable insights into the dynamics of planar mechanical systems with multiple clearance revolute joints. Utilizing a slider-crank mechanism for data acquisition, the study successfully confirmed seven out of nine motion modes previously identified in numerical research. The missing modes are attributed to inherent complexities in real-world systems, such as journal-bearing misalignment.展开更多
Due to autorotation,samaras can fly efficiently and stably to be dispersed over a great distance under various weather conditions.Here,we provide a quantitative analysis of the dynamic stability of free-falling maple ...Due to autorotation,samaras can fly efficiently and stably to be dispersed over a great distance under various weather conditions.Here,we provide a quantitative analysis of the dynamic stability of free-falling maple samara(Acer grosseri Pax)and verify whether they are dynamically stable as observed.Morphological and kinematic parameters were obtained based on the existing experimental data of the maple seed.Then the linearized equations of motion were derived,and the stability derivatives were calculated by a computational fluid dynamics method.The techniques of eigenvalue and eigenvector analysis were also used to examine the stability characteristics.It is found that there are five natural modes of motion of the maple seed:one stable oscillatory mode,one fast subsidence mode,one slow subsidence mode,and two neutral stable modes.The two neutral modes are manifested as the seed moving horizontally at a low speed under disturbance.Results show that the maple seed has dynamic stability in sustaining the steady autorotation and descent,exhibiting a minor horizontal motion when disturbed.These findings can beapplied to biomimetic aircraft.展开更多
The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified an...The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified and the hovering flight in longitudinal is unstable.However,in lateral,the modal structure for hovering insects could be different and the stability property of lateral disturbance motion is not as robust as that of longitudinal motion.The cranefly possesses larger aspect ratio and lower Reynolds number,and such differences in morphology and kinematics may make the lateral dynamic stability different.In this paper,the lateral flight stability of the cranefly in hover is investigated by numerical simulation.Firstly,the stability derivatives are acquired by solving the incompressible Navier–Stokes equations.Subsequently,the dynamic stability characteristics are checked by analyzing the eigenvalues and eigenvectors of the linearized system.Computational results indicate that the lateral dynamic modal structure of cranefly is different from most other insects,consisting of three natural modes,and the weakly oscillatory mode illustrates the hovering lateral flight is nearly neutral.This neutral stability is mainly caused by the negative derivative of roll-moment vs.sideslip-velocity,which can be attributed to the weaker‘changingLEV-axial-velocity’effect.These results suggest that insects in nature may exhibit different dynamic stabilities with different morphological and kinematic parameters,which should be considered in the designs of flapping wing air vehicles.展开更多
The equations of motion of an insect with flapping wings are derived and then simplified to that of a flying body using the ＂rigid body＂ assumption. On the basis of the simplified equations of motion, the longitudin...The equations of motion of an insect with flapping wings are derived and then simplified to that of a flying body using the ＂rigid body＂ assumption. On the basis of the simplified equations of motion, the longitudinal dynamic flight stability of four insects （hoverfly, cranefly, dronefly and hawkmoth） in hovering flight is studied （the mass of the insects ranging from 11 to 1,648 mg and wingbeat frequency from 26 to 157Hz）. The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. The validity of the ＂rigid body＂ assumption is tested and how differences in size and wing kinematics influence the applicability of the ＂rigid body＂ assumption is investigated. The primary findings are： （1） For insects considered in the present study and those with relatively high wingbeat frequency （hoverfly, drone fly and bumblebee）, the ＂rigid body＂ assumption is reasonable, and for those with relatively low wingbeat frequency （cranefly and howkmoth）, the applicability of the ＂rigid body＂ assumption is questionable. （2） The same three natural modes of motion as those reported recently for a bumblebee are identified, i.e., one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. （3） Approximate analytical expressions of the eigenvalues, which give physical insight into the genesis of the natural modes of motion, are derived. The expressions identify the speed derivative Mu （pitching moment produced by unit horizontal speed） as the primary source of the unstable oscillatory mode and the stable fast subsidence mode and Zw （vertical force produced by unit vertical speed） as the primary source of the stable slow subsidence mode.展开更多
The lateral dynamic flight stability of a hovering model insect （dronefly） was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigen...The lateral dynamic flight stability of a hovering model insect （dronefly） was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. The main results are as following. （i） Three natural modes of motion were identified： one unstable slow divergence mode （mode 1）, one stable slow oscillatory mode （mode 2）, and one stable fast subsidence mode （mode 3）. Modes 1 and 2 mainly consist of a rotation about the horizontal longitudinal axis （x-axis） and a side translation; mode 3 mainly consists of a rotation about the x-axis and a rotation about the vertical axis. （ii） Approximate analytical expressions of the eigenvalues are derived, which give physical insight into the genesis of the natural modes of motion. （iii） For the unstable divergence mode, td, the time for initial disturbances to double, is about 9 times the wingbeat period （the longitudinal motion of the model insect was shown to be also unstable and td of the longitudinal unstable mode is about 14 times the wingbeat period）. Thus, although the flight is not dynamically stable, the instability does not grow very fast and the insect has enough time to control its wing motion to suppress the disturbances.展开更多
Most hovering insects flap their wings in a horizontal plane, called ＇normal hovering＇. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudina...Most hovering insects flap their wings in a horizontal plane, called ＇normal hovering＇. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudinal dynamic flight stability of a model hoverfly in inclined-stroke-plane hovering was studied. Computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was used to solve the equations of motion. The primary findings are as follows. （1） For inclined-stroke-plane hovering, the same three natural modes of motion as those for normal hovering were identified： one unstable oscillatory mode, one stable fast subsidence mode, and one stable slow subsidence mode. The unstable oscillatory mode and the fast subsidence mode mainly have horizontal translation and pitch rotation, and the slow subsidence mode mainly has vertical translation. （2） Because of the existence of the unstable oscillatory mode, inclined-stroke-plane hov- ering flight is not stable. （3） Although there are large differences in stroke plane and body orientations between the in- clined-stroke-plane hovering and normal hovering, the relative position between the mean center of pressure and center of mass for these two cases is not very different, resulting in similar stability derivatives, hence similar dynamic stability properties for these two types of hovering.展开更多
Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation cou...Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.展开更多
The longitudinal dynamic flight stability of a bumblebee in forward flight is studied. The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eig...The longitudinal dynamic flight stability of a bumblebee in forward flight is studied. The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are employed for solving the equations of motion. The primary findings are as the following. The forward flight of the bumblebee is not dynamically stable due to the existence of one （or two） unstable or approximately neutrally stable natural modes of motion. At hovering to medium flight speed [flight speed Ue = （0-3.5）m s^-1; advance ratio J = 0-0.44], the flight is weakly unstable or approximately neutrally stable; at high speed （Ue = 4.5 m s^-1; J = 0.57）, the flight becomes strongly unstable （initial disturbance double its value in only 3.5 wingbeats）.展开更多
文摘A comprehensive review on bio-inspired fish robots has been done in this article with an enhanced focus on swimming styles,actuators,hydrodynamics,kinematic-dynamic modeling,and controllers.Swimming styles such as body and/or caudal fin and median and/or paired fin and their variants are discussed in detail.Literature shows that most fish robots adapt carangiform in body and/or caudal fin type swimming as it gives significant thrust with a maximum speed of 3.7 ms 1 in iSplash-II.Applications of smart or soft actuators to enhance real-time dynamics was studied from literature,and it was found that the robot built with polymer fiber composite material could reach a speed of 0.6 m s However,dynamic modeling is relatively complex,and material selection needs to be explored.The numerical and analytical methods in dynamic modeling have been investigated highlighting merits and demerits.Hydrodynamic parameter estimation through the data-driven model is widely used in offline,however online estimation of the same need to be explored.Classical controllers are frequently used tor navigation and stabilization,which often encounters the linearization problem and hence,can be replaced with the state-of-the-art adaptive and intelligent controller.This article also summarizes the potential research gaps and future scopes.
基金the China Postdoctoral Science Foundation(No.20100480588)the National High Technology Research and Development Program(863)of China(No.2007AA09Z215)the Program of Key Laboratories of Shanghai Jiaotong University(No.GKZD010043)
文摘This article describes an experimental prototype flying fish II and builds a dynamic model that is a novel type of autonomous underwater vehicle(AUV)under the condition of negative buoyancy vehicle(NBV) without large buoyancy mechanism.Compared with the AUV Remus 100,the flying fish II can cruise with double speeds within the same range and dimensions.The static stability and motion modes of flying fish II in the longitudinal plane are analyzed through the linear system theory.The flying fish II has static stability in the longitudinal plane and the motion mode is related to metacentric height.
文摘Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can investigate the effects of the clearances on the dynamics of the multibody system. A revolute joint with clearance exhibits three motions which are;free-flight, impact and continuous contact motion modes. Therefore, a multibody system with n-number of revolute clearance joints will exhibit 3n motion modes which are a combination of the three motions in each joint. This study investigates experimentally the nine motion modes in a mechanical system with two revolute clearance joints. A slider crank mechanism has been used as the demonstrative example. We observed that the experimental curve exhibits a greater impact compared to the simulation curve. In conclusion, this experimental investigation offers valuable insights into the dynamics of planar mechanical systems with multiple clearance revolute joints. Utilizing a slider-crank mechanism for data acquisition, the study successfully confirmed seven out of nine motion modes previously identified in numerical research. The missing modes are attributed to inherent complexities in real-world systems, such as journal-bearing misalignment.
基金supported by the National Natural Science Foundation of China(Grant No.11832004)。
文摘Due to autorotation,samaras can fly efficiently and stably to be dispersed over a great distance under various weather conditions.Here,we provide a quantitative analysis of the dynamic stability of free-falling maple samara(Acer grosseri Pax)and verify whether they are dynamically stable as observed.Morphological and kinematic parameters were obtained based on the existing experimental data of the maple seed.Then the linearized equations of motion were derived,and the stability derivatives were calculated by a computational fluid dynamics method.The techniques of eigenvalue and eigenvector analysis were also used to examine the stability characteristics.It is found that there are five natural modes of motion of the maple seed:one stable oscillatory mode,one fast subsidence mode,one slow subsidence mode,and two neutral stable modes.The two neutral modes are manifested as the seed moving horizontally at a low speed under disturbance.Results show that the maple seed has dynamic stability in sustaining the steady autorotation and descent,exhibiting a minor horizontal motion when disturbed.These findings can beapplied to biomimetic aircraft.
基金This work was supported by grants from the National Natural Science Foundation of China(Nos.11802262 and 11502228).
文摘The dynamic flight stability of hovering insects includes the longitudinal and lateral motion.Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified and the hovering flight in longitudinal is unstable.However,in lateral,the modal structure for hovering insects could be different and the stability property of lateral disturbance motion is not as robust as that of longitudinal motion.The cranefly possesses larger aspect ratio and lower Reynolds number,and such differences in morphology and kinematics may make the lateral dynamic stability different.In this paper,the lateral flight stability of the cranefly in hover is investigated by numerical simulation.Firstly,the stability derivatives are acquired by solving the incompressible Navier–Stokes equations.Subsequently,the dynamic stability characteristics are checked by analyzing the eigenvalues and eigenvectors of the linearized system.Computational results indicate that the lateral dynamic modal structure of cranefly is different from most other insects,consisting of three natural modes,and the weakly oscillatory mode illustrates the hovering lateral flight is nearly neutral.This neutral stability is mainly caused by the negative derivative of roll-moment vs.sideslip-velocity,which can be attributed to the weaker‘changingLEV-axial-velocity’effect.These results suggest that insects in nature may exhibit different dynamic stabilities with different morphological and kinematic parameters,which should be considered in the designs of flapping wing air vehicles.
基金The project supported by the National Natural Science Foundation of China(10232010 and 10472008)
文摘The equations of motion of an insect with flapping wings are derived and then simplified to that of a flying body using the ＂rigid body＂ assumption. On the basis of the simplified equations of motion, the longitudinal dynamic flight stability of four insects （hoverfly, cranefly, dronefly and hawkmoth） in hovering flight is studied （the mass of the insects ranging from 11 to 1,648 mg and wingbeat frequency from 26 to 157Hz）. The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. The validity of the ＂rigid body＂ assumption is tested and how differences in size and wing kinematics influence the applicability of the ＂rigid body＂ assumption is investigated. The primary findings are： （1） For insects considered in the present study and those with relatively high wingbeat frequency （hoverfly, drone fly and bumblebee）, the ＂rigid body＂ assumption is reasonable, and for those with relatively low wingbeat frequency （cranefly and howkmoth）, the applicability of the ＂rigid body＂ assumption is questionable. （2） The same three natural modes of motion as those reported recently for a bumblebee are identified, i.e., one unstable oscillatory mode, one stable fast subsidence mode and one stable slow subsidence mode. （3） Approximate analytical expressions of the eigenvalues, which give physical insight into the genesis of the natural modes of motion, are derived. The expressions identify the speed derivative Mu （pitching moment produced by unit horizontal speed） as the primary source of the unstable oscillatory mode and the stable fast subsidence mode and Zw （vertical force produced by unit vertical speed） as the primary source of the stable slow subsidence mode.
基金supported by the National Natural Science Foundation of China(10732030)the 111 Project(B07009)
文摘The lateral dynamic flight stability of a hovering model insect （dronefly） was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. The main results are as following. （i） Three natural modes of motion were identified： one unstable slow divergence mode （mode 1）, one stable slow oscillatory mode （mode 2）, and one stable fast subsidence mode （mode 3）. Modes 1 and 2 mainly consist of a rotation about the horizontal longitudinal axis （x-axis） and a side translation; mode 3 mainly consists of a rotation about the x-axis and a rotation about the vertical axis. （ii） Approximate analytical expressions of the eigenvalues are derived, which give physical insight into the genesis of the natural modes of motion. （iii） For the unstable divergence mode, td, the time for initial disturbances to double, is about 9 times the wingbeat period （the longitudinal motion of the model insect was shown to be also unstable and td of the longitudinal unstable mode is about 14 times the wingbeat period）. Thus, although the flight is not dynamically stable, the instability does not grow very fast and the insect has enough time to control its wing motion to suppress the disturbances.
文摘Most hovering insects flap their wings in a horizontal plane, called ＇normal hovering＇. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudinal dynamic flight stability of a model hoverfly in inclined-stroke-plane hovering was studied. Computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was used to solve the equations of motion. The primary findings are as follows. （1） For inclined-stroke-plane hovering, the same three natural modes of motion as those for normal hovering were identified： one unstable oscillatory mode, one stable fast subsidence mode, and one stable slow subsidence mode. The unstable oscillatory mode and the fast subsidence mode mainly have horizontal translation and pitch rotation, and the slow subsidence mode mainly has vertical translation. （2） Because of the existence of the unstable oscillatory mode, inclined-stroke-plane hov- ering flight is not stable. （3） Although there are large differences in stroke plane and body orientations between the in- clined-stroke-plane hovering and normal hovering, the relative position between the mean center of pressure and center of mass for these two cases is not very different, resulting in similar stability derivatives, hence similar dynamic stability properties for these two types of hovering.
基金supported by the National Natural Science Foundation of China(Grant No.50979069)the Science and Technology Project of West China Traffic Construction(Grant No.200632800003-06)
文摘Corresponding to the sliding and the overturning failure,the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion,the horizontal sliding-rotational oscillation coupled motion,the horizontal vibrating-uplift rocking coupled motion,and the horizontal sliding-uplift rocking coupled motion.The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson.The numerical models of four motion modes of caisson are developed,and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment.It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters.
基金the National Natural Science Foundation of China (10732030)
文摘The longitudinal dynamic flight stability of a bumblebee in forward flight is studied. The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are employed for solving the equations of motion. The primary findings are as the following. The forward flight of the bumblebee is not dynamically stable due to the existence of one （or two） unstable or approximately neutrally stable natural modes of motion. At hovering to medium flight speed [flight speed Ue = （0-3.5）m s^-1; advance ratio J = 0-0.44], the flight is weakly unstable or approximately neutrally stable; at high speed （Ue = 4.5 m s^-1; J = 0.57）, the flight becomes strongly unstable （initial disturbance double its value in only 3.5 wingbeats）.
