Modeling and Simulations of the Supercavitating Vehicle With Its Tail-Slaps

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Wang Zou ◽  
Hua Liu
Keyword(s):  
Dynamic Equilibrium ◽  
Hydrodynamic Forces ◽  
Rigid Body Dynamics ◽  
Supercavitating Vehicle ◽  
Model Combining ◽  
Motion Modes ◽  
Body Dynamics ◽  
The Stability ◽  
And Control ◽  
Control Surfaces

It is one of the most important stable motion modes to move with tail-slaps for supercavitating vehicle. The periodical tail-slaps provide lift and restoring moment to keep a dynamic equilibrium of the vehicle. Research on the mode is significant to the stability and controllability of supercavity and its vehicle. The effect of the tail-slaps on supercavity is modeled to establish a supercavity model, combining with effects of gravity and angle of attack (AOA). Hydrodynamic forces acting on the vehicle are also formulated in the longitudinal plane based on the supercavity model and rigid body dynamics, considering its tail-slaps and control surfaces. The vehicle, which has a fixed periodical tail-slap, is simulated to calculate its hydrodynamic forces at a constant horizontal speed for different maximum pitch angles using the cavitation number embedded coefficient correction algorithm. The supercavity model is finally verified to some extent by comparing numerical results with experimental ones.

Sensorless Modal Stabilization for Three-Link Robotic Arm With Elastic Wrist Drive Belt

2001 ◽  
Author(s):  
Martin Hosek
Keyword(s):  
Rigid Body ◽  
Robotic Manipulator ◽  
Vibration Damping ◽  
Rigid Body Dynamics ◽  
Limiting Factor ◽  
Direct Drive ◽  
Stability And Control ◽  
Body Dynamics ◽  
Improved Stability ◽  
And Control

Abstract A control system for a three-link direct-drive robotic manipulator with inherent structural flexibilities is presented. The structural flexibilities introduce undesirable vibration modes which may affect operation of the robot motion controller, resulting in destabilization of the closed-loop system. This represents a major limiting factor for implementation of a conventional controller designed solely for the rigid body dynamics of the robotic manipulator. The fundamental idea in the presented approach is to use a composite controller which consists of a trajectory-tracking section designed for the rigid-body dynamics and a vibration-damping compensator added for attenuation of the dominant flexible dynamics. The vibration damping compensator operates on estimated states of the dominant flexible dynamics obtained from a reduced-order state observer. A mechanism is implemented which allows the robotic manipulator to move through or hold in positions where the dominant flexible dynamics is unobservable and uncontrollable. Results of laboratory tests document that the presented approach leads to improved stability and control performance.

Paper 27. The Stability of a Ship in a Simple Sinusoidal Wave

1972 ◽  
Vol 14 (7) ◽  
pp. 194-206 ◽  
Author(s):  
W. G. Price
Keyword(s):  
Differential Equations ◽  
Rigid Body Dynamics ◽  
Linear Differential Equations ◽  
Stability Criteria ◽  
Sinusoidal Wave ◽  
Body Dynamics ◽  
Constant Coefficients ◽  
Linear Differential ◽  
The Stability ◽  
Dynamics Stability

The linear differential equations governing the motion of a ship in a sinusoidal wave disturbance are derived from the principles of rigid body dynamics. Stability criteria are obtained when the linear differential equations have ( a) constant coefficients and ( b) periodic time-dependent coefficients that are needed to describe the ship in a following sinusoidal wave. The frequency of encounter between ship and wave is not necessarily zero.

On the stability and control of unicycles

2010 ◽  
Vol 466 (2118) ◽  
pp. 1849-1869 ◽  
Author(s):  
Robin S. Sharp
Keyword(s):  
Linear Model ◽  
Dynamic Equilibrium ◽  
Linear Equations ◽  
Torque Control ◽  
Upper Body ◽  
Optimal Controls ◽  
Nonlinear Simulation ◽  
Small Perturbations ◽  
The Stability ◽  
And Control

A mathematical model of a unicycle and rider, with a uniquely realistic tyre force and moment representation, is set up with the aid of multibody modelling software. The rider’s upper body is joined to the lower body through a spherical joint, so that wheel, yaw, pitch and roll torques are available for control. The rider’s bandwidth is restricted by low-pass filters. The linear equations describing small perturbations from a straight-running state are shown, which equations derive from a parallel derivation yielding the same eigenvalues as obtained from the first method. A nonlinear simulation model and the linear model for small perturbations from a general trim (or dynamic equilibrium) state are constructed. The linear model is used to reveal the stability properties for the uncontrolled machine and rider near to straight running, and for the derivation of optimal controls. These controls minimize a cost function made up of tracking errors and control efforts. Optimal controls for near-straight-running conditions, with left/right symmetry, and more complex ones for cornering trims are included. Frequency responses of some closed-loop systems, from the former class, demonstrate excellent path-tracking qualities within bandwidth and amplitude limits. Controls are installed for path-following trials. Lane-change and clothoid manoeuvres are simulated, demonstrating good-quality tracking of longitudinal and lateral demands. Pitch torque control is little used by the rider, while yaw and roll torques are complementary, with the former being more useful in transients, while the latter has value also in steady states. Wheel torque is influential on lateral control in turning. Adaptive control by gain switching is used to enable clothoid tracking up to lateral accelerations greater than 1 m s −2 . General control of the motions of a virtual or robotic unicycle will be possible through the addition of more comprehensive adaptation to the control scheme described.

scholarly journals Geometric Pseudospectral Method on SE(3) for Rigid-Body Dynamics with Application to Aircraft

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Jie Li ◽  
Honglei An ◽  
Huayong Zhu ◽  
Lincheng Shen ◽  
Bin Fang
Keyword(s):  
Rigid Body ◽  
Lie Algebra ◽  
Lie Group ◽  
Pseudospectral Method ◽  
Velocity Model ◽  
Rigid Body Dynamics ◽  
Dynamics Simulation ◽  
Configuration Model ◽  
Body Dynamics ◽  
And Control

General pseudospectral method is extended to the special Euclidean group SE(3) by virtue of equivariant map for rigid-body dynamics of the aircraft. On SE(3), a complete left invariant rigid-body dynamics model of the aircraft in body-fixed frame is established, including configuration model and velocity model. For the left invariance of the configuration model, equivalent Lie algebra equation corresponding to the configuration equation is derived based on the left-trivialized tangent of local coordinate map, and the top eight orders truncated Magnus series expansion with its coefficients of the solution of the equivalent Lie algebra equation are given. A numerical method called geometric pseudospectral method is developed, which, respectively, computes configurations and velocities at the collocation points and the endpoint based on two different collocation strategies. Through numerical tests on a free-floating rigid-body dynamics compared with several same order classical methods in Euclidean space and Lie group, it is found that the proposed method has higher accuracy, satisfying computational efficiency, stable Lie group structural conservativeness. Finally, how to apply the previous discretization scheme to rigid-body dynamics simulation and control of the aircraft is illustrated.

INVESTIGATION ON STABILITY IN ROLL OF SQUARE SECTION MISSILE AT HIGH ANGLE OF ATTACK

2010 ◽  
Vol 24 (13) ◽  
pp. 1385-1388 ◽  
Author(s):  
YANG TAO ◽  
ZHAOLIN FAN ◽  
JIFEI WU ◽  
WENHUA WU
Keyword(s):  
Longitudinal Axis ◽  
Rigid Body Dynamics ◽  
High Angle ◽  
Damped Oscillations ◽  
Movement Characteristics ◽  
High Incidence ◽  
Body Dynamics ◽  
The Stability ◽  
Wing Rock Motion ◽  
Fluid Dynamics Equations

An experimental investigation of the stability in roll of a square section missile at high incidence was conducted in FL-23 wind tunnel. Dynamic motions were obtained on a square section missile that is free to rotate about its longitudinal axis. Different dynamic rolling motions were observed depending on the incidence of the model sting. These dynamic regimes include damped oscillations, quasi-limit-cycle wing-rock motion, and constant rolling. A coupling numerical method was established by solving the fluid dynamics equations and the rigid-body dynamics equations synchronously in order to predict the onset and the development of uncommented motions and then explore the unsteady movement characteristics of the aircraft. The study indicates that the aircraft loss stability at high incidence is caused by the asymmetric vertex on the level fin tip liftoff and attach alternately. The computation results are in line with the experiment results.

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