Multiple-Mode Dynamic Model for Piezoelectric Micro-Robot Walking

2016 ◽  
Author(s):  
Jinhong Qu ◽  
Kenn R. Oldham
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Beam Theory ◽  
Body Motion ◽  
Six Degrees Of Freedom ◽  
Robot Locomotion ◽  
Multiple Mode ◽  
Micro Robot ◽  
Actuation Scheme ◽  
Robot Body

A multiple-mode dynamic model is developed for a piezoelectrically-actuated micro-robot with multiple legs. The motion of the micro robot results from dual direction motion of piezoelectric actuators in the legs, while the complexity of micro robot locomotion is increased by impact dynamics. The dynamic model is developed to describe and predict the micro robot motion, in the presence of asymmetrical behavior due to non-ideal fabrication and variable properties of the underlying terrain. The dynamic model considers each robot leg as a continuous structure moving in two directions derived from beam theory with specific boundary condition. Robot body motion is modeled in six degrees of freedom using a rigid body approximation. Individual modes of the resulting multimode robot are treated as second order linear systems. The dynamic model is tested with a meso-scale robot prototype having a similar actuation scheme as micro-robots. In accounting for the interaction between robot and ground, the dynamic model with first two modes of each leg shows good match with experimental results for the mesoscale prototype, in terms of both magnitude and the trends of robot locomotion with respect to actuation conditions.

scholarly journals Modeling Legged Microrobot Locomotion Based on Contact Dynamics and Vibration in Multiple Modes and Axes

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Jinhong Qu ◽  
Clark B. Teeple ◽  
Kenn R. Oldham
Keyword(s):  
Rigid Body ◽  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Beam Theory ◽  
Contact Dynamics ◽  
Body Motion ◽  
Small Scale ◽  
Robot Locomotion ◽  
Actuation Scheme ◽  
Dynamics And Vibration

A dynamic model is developed for small-scale robots with multiple high-frequency actuated compliant elastic legs and a rigid body. The motion of the small-scale robots results from dual-direction motion of piezoelectric actuators attached to the legs, with impact dynamics increasing robot locomotion complexity. A dynamic model is developed to describe the small-scale robot motion in the presence of variable properties of the underlying terrain. The dynamic model is derived from beam theory with appropriate boundary and loading conditions and considers each robot leg as a continuous structure moving in two directions. Robot body motion is modeled in up to five degrees-of-freedom (DOF) using a rigid body approximation for the central robot chassis. Individual modes of the resulting multimode robot are treated as second-order linear systems. The dynamic model is tested with two different centimeter-scale robot prototypes having an analogous actuation scheme to millimeter-scale microrobots. In accounting for the interaction between the robot and ground, a dynamic model using the first two modes of each leg shows good agreement with experimental results for the centimeter-scale prototypes, in terms of both magnitude and the trends in robot locomotion with respect to actuation conditions.

Comparisons of Turning Abilities of Submarine With Different Rudder Configurations

2018 ◽  
Author(s):  
Dakui Feng ◽  
Xuanshu Chen ◽  
Hao Liu ◽  
Zhiguo Zhang ◽  
Xianzhou Wang
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Control Device ◽  
Body Motion ◽  
The Real ◽  
Six Degrees Of Freedom ◽  
Overlapping Grids ◽  
Free Running ◽  
Turning Radius ◽  
Time Changes

Submarine is usually equipped with two different control device arrangements, namely a cruciform and a X rudder configuration. In this paper, numerical simulations of the DARPA Suboff submarine and its retrofitted submarine with a X rudder configuration are presented. Turning simulations in model scale were studied to compare the turning abilities of the two different control device arrangements. The computations were performed with a house viscous CFD solver based on the conservative finite difference method. In the solver, RANS equation are solved coupled with six degrees of freedom (6DOF) solid body motion equations of the submarine in real time. The structured dynamic overlapping grids were used to simulate the real-time changes of the attitude of the submarine and the rotation of the rudder. The volume force method was used to replace the real propeller to realize the self-propelled movement of submarine. In the free running maneuvering simulations, the submarines move at the same initial velocity and rudder angle, restricted to the horizontal plane with four degrees of freedom (4DOF). Comparisons of the trajectory and kinematic parameters including relative turning radius and turning period between the two cases were presented in this paper. The results show that, compared with the cruciform rudder configuration, the X rudder configuration has obvious advantages for submarine in the turning abilities.

A Three-Dimensional Dynamic Model for Determining the Equilibrium Configurations of Buoyantly Unstable Icebergs

1990 ◽  
Vol 112 (3) ◽  
pp. 253-262
Author(s):  
R. G. Jessup ◽  
S. Venkatesh
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Static Potential ◽  
Initial State ◽  
Model Simulations ◽  
Six Degrees Of Freedom ◽  
Equilibrium Configurations ◽  
Variation Range

This paper describes a dynamic model developed for the purpose of determining the final equilibrium configurations of buoyantly unstable icebergs. The model places no restrictions on the size, shape, or dimensionality of the iceberg, or on the variation range of the configuration coordinates. Furthermore, it includes all six degrees of freedom and is based on a Lagrangian formulation of the dynamic equations of motion. It can be used to advantage in those situations in which the iceberg has a complicated potential function and can acquire enough momentum and kinetic energy in the initial phase of its motion to make its final configuration uncertain on the basis of a static potential analysis. The behavior of the model is examined through several model simulations. The sensitivity of the final equilibrium position to the initial orientation and shape of the iceberg is clearly evident in the model simulations. Model simulations also show that when an iceberg is released from a nonequilibrium initial state, the time taken for it to settle down varies from about 40 s for a growler to nearly 400 s for a large iceberg. While these absolute times may change with better parameterization of the forces, the relative variations with iceberg size are likely to be preserved.

Model-Based Verifying and Design of Autonomous Airship

2011 ◽  
Vol 66-68 ◽  
pp. 1748-1754
Author(s):  
Yu Liu ◽  
Yi Lin Wu
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Boundary Layer Theory ◽  
Wind Effect ◽  
Nonlinear Dynamic Model ◽  
Kirchhoff Equations ◽  
Six Degrees Of Freedom ◽  
Motion Characteristics ◽  
Linearized Model ◽  
Rotational Damping

Based on the Kirchhoff equations, Newton-Euler laws, boundary layer theory and mass definition, the six degrees of freedom dynamic model of airship complete with aerodynamic forces, wind effect is presented. Then, the nonlinear dynamic model is divided into three group equations by restricting airship motion in different planes respectively. The motion characteristics of airship, including stability, the effect of ballast position and rotational damping, are studied using linearized model. The results of simulation verify the correctness of the theoretical analysis and airship design.

Modeling the Dynamics of Five-Axis Machine Tool Using the Multibody Approach

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Hoai Nam Huynh ◽  
Yusuf Altintas
Keyword(s):  
Rigid Body ◽  
Machine Tool ◽  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Dynamic Performance ◽  
Body Motion ◽  
Proposed Model ◽  
Multibody Dynamic ◽  
Machining Operations ◽  
Five Axis

Abstract A systematic modeling of multibody dynamics of five-axis machine tools is presented in this article. The machine is divided into major subassemblies such as spindle, column, bed, tool changer, and longitudinal and rotary drives. The inertias and mass center of each subassembly are calculated from the design model. The subassemblies are connected with elastic springs and damping elements at contact joints to form the complete multibody dynamic model of the machine that considers the rigid body kinematics and structural vibrations of the machine at any point. The unknown elastic joint parameters are estimated from the experimental modal analysis of the machine tool. The resulting position-dependent multibody dynamic model has the minimal number of degrees-of-freedom that is equivalent to the number of measured modes, as opposed to thousands used in finite element models. The frequency response functions of the machine can be predicted at any posture of the five-axis machine, which are compared against the directly measured values to assess the validity of model. The proposed model can predict the combined rigid body motion and vibrations of the machine with computational efficiency, and hence, it can be used as a digital twin to simulate its dynamic performance in machining operations and tracking control tests of the servo drives.

Numerical Simulation of Ship-Ship Interactions in Waves

2019 ◽  
Author(s):  
Xueshen Xie ◽  
Yuxiang Wan ◽  
Qing Wang ◽  
Hao Liu ◽  
Dakui Feng
Keyword(s):  
Numerical Simulation ◽  
Degrees Of Freedom ◽  
Simulation Analysis ◽  
Turbulence Models ◽  
Body Motion ◽  
Structured Grid ◽  
Six Degrees Of Freedom ◽  
Unsteady Rans ◽  
Small Ship ◽  
The Impact

Abstract A numerical simulation of the hydrodynamic interaction and attitude of a ship and two ships of different sizes navigating in parallel in waves were carried out in this paper. The study of the two ships navigating in parallel is of great significance in marine replenishment. This paper used in house computational fluid dynamics (CFD) code to solve unsteady RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations. URANS equations are solved by finite difference method and PISO algorithm. Structured grid with overset technology have been used to make computations. Turbulence models used the Shear Stress Transport (SST) k-ω model. The method used for free surface simulation is single phase level set. In this paper, two DTMB 5415 with different scales are selected for simulation analysis. This paper analyzed the impact of the big ship on the small ship when the two ships were navigating in parallel. This paper also analyzed the relationship between interaction and velocity between hulls, which has certain guiding significance for the ship’s encounter on the sea.

Numerical Simulation of Damaged Ship’s Motion in Beam Waves

2019 ◽  
Author(s):  
Qing Wang ◽  
Xuanshu Chen ◽  
Liwei Liu ◽  
Xianzhou Wang ◽  
MingJing Liu
Keyword(s):  
Degrees Of Freedom ◽  
Body Motion ◽  
Ship Motions ◽  
Rans Equations ◽  
Six Degrees Of Freedom ◽  
Calm Water ◽  
Unsteady Simulation ◽  
Ship Hydrodynamic ◽  
Physical Phenomena ◽  
Damaged Ship

Abstract The dangerous situation caused by the breakage of the ship will pose a serious threat to crew and ship safety. If the ship’s liquid cargo or fuel leaks, it will cause serious damage to the marine environment. If damage occurs accompanied by roll and other motions, it may cause more dangerous consequences. It is an important issue to study the damaged ship in time-domain. In this paper, the motions of the damaged DTMB 5512 in calm water and regular beam waves are studied numerically. The ship motions are analyzed through CFD methods, which are acknowledged as a reliable approach to simulate and analyze these complex physical phenomena. An in-house CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for solving RANS equations coupled with six degrees of freedom (6DOF) solid body motion equations. RANS equations discretized by finite difference method and solved by PISO algorithm. Level set was used for free surface simulation. The dynamic behavior of model was observed in both intact and damaged condition. The heave, roll and pitch amplitudes of the damaged ship were studied in calm water and beam wave of three wavelengths.

A nonlinear six degrees of freedom dynamic model of planetary roller screw mechanism

2018 ◽  
Vol 119 ◽  
pp. 22-36 ◽  
Author(s):  
Xiaojun Fu ◽  
Geng Liu ◽  
Ruiting Tong ◽  
Shangjun Ma ◽  
Teik C. Lim
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Six Degrees Of Freedom ◽  
Roller Screw ◽  
Screw Mechanism

Dynamic Model of the Piston-Ring Assembly Using Curved Beam Finite Elements

2011 ◽  
Author(s):  
Mohannad Hakeem ◽  
Nabil G. Chalhoub ◽  
Peter Schihl
Keyword(s):  
Rigid Body ◽  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Piston Ring ◽  
Translational Motion ◽  
Total Duration ◽  
Variable Structure ◽  
Body Motion ◽  
Curved Beam ◽  
Connecting Rod

A dynamic model for the crankshaft/connecting-rod/piston-assembly for a single cylinder engine is developed. The model considers the rigid body motion of the crank-slider mechanism including the piston secondary motions such as the piston-slap and piston-tilting. The formulation considers the ring to have three rigid body degrees of freedom in addition to its longitudinal and in-plane transverse deformations. The structural flexibility terms are approximated by using curved beam finite element method. The dynamic model has a variable structure whereby the number of degrees of freedom depends on the piston-liner and piston-ring interactions. Its formulation does not include frictional losses. The simulation results illustrate the piston secondary motions along with the ring tilting angles relative to the piston orientation for the total duration of the engine cycle. In addition, they exhibit the translational motion of the ring within the piston groove.

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