Modeling the Flow over Planing Hulls with Ventilated or Cavitating Steps

2015 ◽  
Author(s):  
Christopher O'Reilly ◽  
Matthew Murphy ◽  
Dominic Piro ◽  
Neal Fine
Keyword(s):  
Numerical Model ◽  
Three Dimensional ◽  
Degree Of Freedom ◽  
Linear Solution ◽  
3 Dimensional ◽  
Six Degree Of Freedom

A numerical model is being developed to solve for six-degree-of-freedom forces experienced by a cavitating, stepped planing hull. An approach to solving the cavitation or ventilation problem is described. Next a method for solving for spray roots on the hull is detailed and a method for approximating the transom wake for a 3 dimensional planing hull is discussed. Results of the cavity solver for a three-dimensional linear solution are presented. Finally results in the context of three-dimensional planing hull steady resistance simulations are presented and compared to RANS CFD and tow tank experiments.

Force-based delay compensation for hardware-in-the-loop simulation divergence of 6-DOF space contact

2017 ◽  
Vol 233 (1) ◽  
pp. 151-165
Author(s):  
Qian Wang ◽  
Chenkun Qi ◽  
Feng Gao ◽  
Xianchao Zhao ◽  
Anye Ren ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Dynamic Models ◽  
Contact Process ◽  
Three Dimensional ◽  
Compensation Method ◽  
Degree Of Freedom ◽  
Hardware In The Loop ◽  
Delay Compensation ◽  
Measurement Delay ◽  
Six Degree Of Freedom

The contact process of a space docking device needs verification before launching. The verification cannot only rely on the software simulation since the contact dynamic models are not accurate enough yet, especially when the geometric shape of the device is complex. Hardware-in-the-loop simulation is a choice to perform the ground test, where the contact dynamic model is replaced by a real device and the real contact occurs. However, the Hardware-in-the-loop simulation suffers from energy increase and instability since time delay is unavoidable. The existing delay compensation methods are mainly focused on a uniaxial or three-dimensional contact. In this paper, a force-based delay compensation method is proposed for the hardware-in-the-loop simulation of a six degree-of-freedom space contact. A six degree-of-freedom dynamic model of the spacecraft motion is derived, and a six degree-of-freedom delay compensation method is proposed. The delay is divided into track delay and measurement delay, which are compensated individually. Experiment results show that the proposed delay compensation method is effective for the six degree-of-freedom space contact.

Determination of the Workspace of 6-DOF Parallel Manipulators

1989 ◽  
Author(s):  
C. Gosselin
Keyword(s):  
Parallel Manipulator ◽  
Graphical Representation ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Geometrical Properties ◽  
Cartesian Space ◽  
Six Degree Of Freedom

Abstract This paper presents an algorithm for the determination of the workspace of parallel manipulators. The method described here, which is based on geometrical properties of the workspace, leads to a simple graphical representation of the regions of the three-dimensional Cartesian space that are attainable by the manipulator with a given orientation of the platform. Moreover, the volume of the workspace can be easily computed by performing an integration on its boundary, which is obtained from the algorithm. Examples are included to illustrate the application of the method to a six-degree-of-freedom fully-parallel manipulator.

New Machine for Complex Structure Decoration Materials

2012 ◽  
Vol 178-181 ◽  
pp. 262-266
Author(s):  
Jian Guo Luo ◽  
Mao Yan He
Keyword(s):  
Complex Structure ◽  
Three Dimensional ◽  
Influential Factors ◽  
Degree Of Freedom ◽  
Topological Graph ◽  
Working Space ◽  
Hybrid Mechanism ◽  
Definition Of ◽  
Six Degree Of Freedom ◽  
Necessary And Sufficient

A new type of machine for complex structure decoration materials based on hybrid cubic manipulator with six degree of freedom(DOF) suggested in view of traditional serial manipulator and parallel manipulator, three dimensional translation and rotation of output shaft obtained through lineal driving. Define the description of spacial moving capability of common couples and translation base and rotation base of mechanism, based on the fact of mechanism consists of components, a new description method by topological graph theory of components relationship suggested, new description of serial mechanism and parallel mechanism and hybrid mechanism obtained with this method, description elements include component pane and constrained component pane and component relationship line and constrained component relationship line and spacial relative moving capability between adjacent components. DOF(degree of freedom) of hybrid mechanism analysised with example based on the definition of dimensionity of branch spacial moving capability and mechanism spacial moving capability, necessary and sufficient condition of nonsingularity of mechanism presented. Method of analytic geometry used to find the regular cuboid of the reachable working space shape of mechanism, the volume of the reachable working space rest with the limit of translation of couplers, its influential factors obtained, limit length of guideway etc. are the primary influential factors.

Active disturbance rejection guidance and control scheme for homing missiles with impact angle constraints

2018 ◽  
Vol 233 (3) ◽  
pp. 1133-1146
Author(s):  
Jian Hua Wang ◽  
Yuan Wen Cai ◽  
Long Cheng ◽  
Yan Li ◽  
Chao Jun Xin ◽  
...  
Keyword(s):  
Disturbance Rejection ◽  
Three Dimensional ◽  
Impact Angle ◽  
Degree Of Freedom ◽  
Guidance And Control ◽  
Active Disturbance Rejection ◽  
Control Scheme ◽  
Homing Missiles ◽  
Six Degree Of Freedom ◽  
And Control

An active disturbance rejection guidance and control scheme for homing missiles with three-dimensional impact angle constraints is proposed. The six-degree-of-freedom dynamical and kinematical models containing model uncertainties and disturbances are established. A strict feedback relative dynamics between the target and homing missile in three-dimensional space are deduced. A reconstructed reduced-order attitude controller design model is proposed. A two-loop control structure with respect to the centroid guidance loop and rotational control loop is conducted to implement the six-degree-of-freedom guidance and control system with the help of second-order sliding mode approach and extended state observers. The tracking loop of the Euler angles of the missile can be elided and the number of six-degree-of-freedom control parameters can be reduced. Finally, the effectiveness and robustness of the newly proposed guidance and control scheme are investigated and verified via six-degree-of-freedom nonlinear simulation studies.

Three-dimensional numerical modeling of a four-pin probe for soil water content

Soil Research ◽  
2006 ◽  
Vol 44 (2) ◽  
pp. 183 ◽  
Author(s):  
D. Ma ◽  
Y. Sun ◽  
M. Wang ◽  
Y. Gao
Keyword(s):  
Numerical Model ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Three Dimensional ◽  
Time Domain Reflectometry ◽  
Dielectric Constants ◽  
3 Dimensional ◽  
High Frequency Structure Simulator ◽  
Sample Test

Soil probes with 4-pin configuration have been widely used in frequency domain (FD) and time domain reflectometry methods for determining soil water content. The techniques of FD sensors largely rely on the port impedance of the probe. This study provided a 3-dimensional numerical model to represent the electric behaviours of the 4-pin probe, which is valuable for analysing the effect of the soil dielectric constant, geometry, and the operating frequency on the port impedance of the probe. The model was performed with high frequency structure simulator software based on Maxwell’s equations and finite element method. A typical 3-dimensional electromagnetic distribution of the 4-pin probe was presented. The model was validated with 3 experiments under the aid of a network analyser. First, the experiment was performed using a series of fluids of known relative dielectric constants, then numerical simulations were carried out and confirmed by soil sample test with varying frequencies and the probe lengths. The effects of these parameters on FD methods are discussed based on the 4-pin probes. The 3-dimensional numerical model appears to be a meaningful tool to investigate more deeply a 4-pin probe in FD method.

A New Method to Calculate the Force and Moment Workspaces of Actuation Redundant Spatial Parallel Manipulators

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Venus Garg ◽  
Juan A. Carretero ◽  
Scott B. Nokleby
Keyword(s):  
Three Dimensional ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
New Method ◽  
Task Planning ◽  
Cartesian Space ◽  
Redundantly Actuated ◽  
Six Degree Of Freedom

A new method for obtaining the force and moment workspaces of spatial parallel manipulators (PMs) is presented. Force and moment workspaces are regions within which a manipulator can sustain/apply at least a certain value of force or moment in all directions. Here, the force and moment workspaces are found using a method, which explicitly sets the largest possible number of actuators to their maximum limits ensuring that the manipulator is performing at its best possible wrench capabilities. Two cases for obtaining these workspaces are used. The first gives the applicable/sustainable force with a prescribed moment whereas the second one gives the applicable/sustainable moment with a prescribed force. For illustration purposes, the method is applied to a six-degree-of-freedom (DOF) redundantly-actuated spatial PM, the 3-RRṞS. The results are represented graphically as the boundaries of the workspace in the three-dimensional Cartesian space. These workspaces can be used as a powerful tool for path/task planning and PM design.

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