Dynamic Bending of Bionic Flexible Body Driven by Pneumatic Artificial Muscles(PAMs) for Spinning Gait of Quadruped Robot

The body of quadruped robot is generally developed with the rigid structure. The mobility of quadruped robot depcnds on the mechanical properties of the body mechanism, It is difficult for quadruped robot with rigid structure to achieve better mobility walking or running in the unstructured environment. A kind of bionic flexible body mechanism for quadruped robot is proposed, which is composed of one bionic spine and four pneumatic artificial muscles（PAMs）. This kind of body imitates the four-legged creatures＇ kinematical structure and physical properties, which has the characteristic of changeable stiff＇hess, lightweight, flexible and better bionics. The kinematics of body bending is derived, and the coordinated movement between the flexible body and legs is analyzed. The relationship between the body bending angle and the PAM length is obtained. The dynamics of the body bending is derived by the floating coordinate method and Lagrangian method, and the driving tbrce of PAM is determined. The experiment of body bending is conductcd, and the dynamic bending characteristic of bionic flexible body is evaluated. Experimental results show that the bending angle of the bionic flexible body can reach 18. An innovation body mechanism for quadruped robot is proposed, which has the characteristic of flexibility and achieve bending by changing gas pressure of PAMs. The coordinated movement of the body and legs can achieve spinning gait in order to improve the mobility of quadruped robot.

Analysis on pivot turning of quadruped robot with bionic flexible body driven by the PAMs

The pivot turning function of quadruped bionic robots can improve their mobility in unstructured environment.A kind of bionic flexible body mechanism for quadruped robot was proposed in this paper,which is composed of one bionic spine and four pneumatic artificial muscles(PAMs).The coordinated movement of the bionic flexible body and the leg mechanism can achieve pivot turning gait.First,the pivot turning gait planning of quadruped robot was analyzed,and the coordinated movement sequence chart of pivot turning was presented.Then the kinematics modeling of leg side swing and body bending for pivot turning was derived,which should meet the condition of the coordinated movement between bionic flexible body and leg mechanism.The PAM experiment was conducted to analyze its contraction characteristic.The study on pivot turning of the quadruped robot will lay a theoretical foundation for the further research on dynamic walking stability of the quadruped robot in unstructured environment.

DYNAMIC ANALYSIS OF FLEXIBLE BODY WITH DEFINITE MOVING ATTITUTE

The nonlinear dynamic control equation of a flexible multi-body system with definite moving attitude is discussed. The motion of the aircraft in space is regarded as known and the influence of the flexible structural members in the aircraft on the motion and attitude of the aircraft is analyzed. By means of a hypothetical mode, the defor mation of flexible members is regarded as composed of the line element vibration in the axial direction of rectangular coordinates in space. According to Kane＇ s method in dynamics, a dynamic equation is established, which contains the structural stiffness matrix that represents the elastic deformation and the geometric stiffness matrix that represents the nonlinear deformation of the deformed body. Through simplification the dynamic equation of the influence of the planar flexible body with a windsurfboard structure on the spacecraft motion is obtained. The numerical solution for this kind of equation can be realized by a computer.

Non-linear and non-conservative quasi-variational principle of flexible body dynamics and application in spacecraft dynamics

The law of conservation of energy is one of the most fundamental laws of nature.According to the law of the conservation of energy,the non-linear and non-conservative quasi-variational principle of flexible body dynamics is established.The physical meaning of the quasi-stationary value conditions has been explained in non-linear and non-conservative flexible body dynamics.In the case study,the application in spacecraft dynamics is researched.

Three-dimensional Numerical Simulation of the Movement of the Flexible Body under Different Constraints

For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough problem.In this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1:30.The Reynolds number of the airflow is 513,belonging to the area of low Reynolds number.The control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible body.The numerical results show that it is possible to simulate the characteristics of the flexible body's movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is adopted.Unconstrained flexible body would turn over forward along the airflow's diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible body.The preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.

DYNAMICS OF FLEXIBLE MULTIBODY SYSTEMS WITH TREE TOPOLOGIES

The dynamic equations of flexible multibody systems with tree topological configuration are de- rived by using the Jourdain's principle.The independent joint coordinates are introduced to describe the large displacements of the bodies,and the modal coordinates are used to describe small deformations of flexible bodies based on the consistent mass finite element method and normal vibration mode analysis.The mini- mum differential equations are developed,which are compatible with the equations of multi-rigid body sys- tems or structural dynamics.The stiff problem in the numerical integration is thus alleviated effectively.The method used in this paper can be extended to deal with systems with other topological configurations. Finally,the validity and feasibility of the presented mathematical model are demonstrated by a numerical ex- ample of a manipulator with two elastic links.

Development of a Flexible Multibody Model to Simulate Nonlinear Effects in Printing Process

Modern high speed printing machines are able to print up to 700 m/min. At this rate, little excita-tions lead to vibrations, which may lead to loss of contact between the rollers (bouncing). This bouncing results in white stripes, being visible on the printed image. To enable the simulation of the whole printing process, including effects like bouncing, a discrete multibody model is developed. The rollers are modeled by several rigid bodies. These bodies are connected to each other by rotational springs, which allow simulation of the first bending eigenmodes of each roller. The contact area between the rollers is modeled by several nonlinear translational springs and damping elements. These elements change their stiffness and damping values depending on the distance between the rollers. If a defined distance is exceeded, the values become zero, which represents the loss of contact (bouncing). The unknown spring and damping elements of this model are parametrized with help of an experimental modal analysis. This paper presents the development of a flexible multibody model to simulate nonlinear effects in printing process.

MULTI-FLEXIBLE SYSTEM DYNAMIC MODELING THEORY AND APPLICATION

The flexible body modeling theory was demonstrated. An example of modeling a kind of automobile’s front suspension as a multi-flexible system was shown. Finally, it shows that the simulation results of multi-flexible dynamic model more approach the road test data than those of multi-rigid dynamic model do. Thus, it is fully testified that using multi-flexible body theory to model is necessary and effective.

Dynamic Analysis of Flexible Cage of High-speed Angular Contact Ball Bearing

A dynamics formula was established for the flexible cage of high-speed angular contact ball bearing. A modified Craig-Bampton component mode synthetic method was used to establish the formula with regard to the flexibility of cage and based on a dynamic analysis of angular contact ball bearing,and a rigid-flexible multi-body dynamic analysis program was developed using ADAMS,which is verified by a computation example of Gupta. The results show that it's not likely to keep the rotation smoothness of cage when the ratio of pocket clearance to guiding clearance and the ratio of radial load to axial load become too large or too small. By comparison,the flexible cage runs more smoothly than the rigid cage.

Improved Body Flexibility Following Removal of a Miniscrew Implant

A 65-year-old woman, who had been suffering from inflexibility, neck and eye pain as well as general discomfort and stiffness, experienced an improvement in her symptoms upon the removal of a dental miniscrew implant. However, her symptoms returned when the implant was placed near her foot. Her symptoms continued to improve for 6 months. We hypothesize that the cause of her symptoms is linked to electromagnetic waves attracted by the implant. However, the exact underlying mechanism remains unclear, and further research is required in cooperation with the dental, medical, and related fields.

Numerical Simulation of TWo Different Flexible Bodies Immersed in Moving Flow

The coupled motion of two flexible bodies with different lengths immersed in moving fluid is studied numerically. The flapping frequency, flapping amplitude and average drag coefficient of each body are calculated and the influences of the arranging manner and separation distance are analyzed. In our simulation, when placed in the flow individually, the flexible body with a longer length will flap in period and the shorter one will maintain still straightly in the flow direction. The numerical results show that, two different flexible structures near placed in moving flow would strongly interact. When they are placed side by side, the existence of the stable shorter flexible body will restrain the flapping of the longer one while the existence of the longer flexible body may also induce the shorter one to flap synchronously. When placed in tandem with the shorter flexible body in upstream, the flapping of the longer one in downstream will be obviously enhanced. In the situation for the longer flexible body placed in upstream of the shorter one, the coupled flapping amplitude and average drag coefficients increase and decrease periodically with increasing the arranging space, and peak values appear as a result of the mediate of the tail wakes.

Modeling of large scale solar cell handling robot with belt-driven flexible arms

To increase the competition of the solar energy collection system, the size of the solar panel module during the manufacturing process is being increased continuously. As the size of the solar panel increases, the size of the robot to handle the panel increased also. The change in scale of the robot inevitably results ill the amplification of the adverse effect of tile flexure. The main source of the flexure in the large scale solar cell panel handling system is the long and thin fork fingers of the [land and the solar cell panel. In addition, tile belt-driven actuator system used by most of the large scale panel handling robot is another significant source of the vibration. In this paper, the flexible multi body dynamic model of a large scale solar cell panel handling robot, which is being designed and constructed with the help of Kyung Hee University, is developed. The belt-driven system in the robot is also modeled as flexible system and included ill the robot to represent the actual vibration characteristics of the actuator system. C 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi： 10.1063/2.1301310]

Improved lateral-dynamics-intended railway vehicle model involving nonlinear wheel/rail interaction and car body flexibility

To study the vehicle hunting behavior and its coupling with car body vibrations,a simplified lateral-dynamics-intended railway vehicle model is developed.A two-truck vehicle is modeled as a 17 degrees-of-freedom rigid system,into which the car body flexural vibrations of torsion and bending modes are further integrated.The wheel/rail interaction employs a real-time calculation for the Hertzian normal contact,in which the nonlinear curvatures of wheel and rail profiles are presented as functions of wheelset lateral movement and/or yaw rotation.Then the tangential/creep forces are analytically expressed as the Hertzian contact patch geometry,and lead to a continuous and fast calculation compared to a look-up table interpolation.It is shown that the hunting frequencies of the vehicle model and a truck model differ significantly,which verifies the necessity of the whole vehicle model.In the case of low wheel/rail conicity,the hunting frequency increases linearly with vehicle speed,whereas it rises slowly at high speed for a large conicity.Comparison of hunting frequency and damping ratio between various conicities shows that first hunting(car body hunting)may occur when the vehicle is operated at a low speed in a small conicity case,while a second hunting(truck hunting)appears when the vehicle is operated at a high speed in a large conicity case.Stability analysis of linear and nonlinear vehicle models was carried out through coast down method and constant speed simulations.Results tell that the linear one overestimates the lateral vibrating.Whereas the structural vibrations of car body can be ignored in the stability analysis.Compared to existing simplified models for hunting stability study,the proposed simplified vehicle model released limitations in the nonlinear geometries of wheel/rail profiles,and it is suitable for a frequency-domain analysis by deriving the analytical expressions of the normal and tangential wheel/rail contact forces.

Rigid-Flex Coupling Modeling and Simulation on Multistage Gear Transmission System

As multistage gear transmission systems are complex and precise, the flexibility of shaft can influence the dynamic response of system. In order to study dynamic response of the system, we build the rigid model of gear system and the finite element model of the gear shaft. virtual prototype technology, and a contrast between rigid The rigid-flex coupling model is established with the model and rigid-flex coupling model is constructed. With these methods, the dynamic responses with different rotation speeds and different loading magnitudes are examined. We also analyze the influence of shaft flexibility, rotation speeds and loading magnitudes on the vibration characteristics of gear transmission systems.