This class provides hydrodynamic behaviour for underwater vehicles It is shamelessly based off Brian Bingham's plugin for VRX. which in turn is based of Fossen's equations described in "Guidance and Control of Ocean Vehicles" [1]. The class should be used together with the buoyancy plugin to help simulate behaviour of maritime vehicles. Hydrodynamics refers to the behaviour of bodies in water. It includes forces like linear and quadratic drag, buoyancy (not provided by this plugin), etc. More...
#include <Hydrodynamics.hh>
Public Member Functions  
Hydrodynamics ()  
Constructor. More...  
~Hydrodynamics () override  
Destructor. More...  
void  Configure (const Entity &_entity, const std::shared_ptr< const sdf::Element > &_sdf, EntityComponentManager &_ecm, EventManager &) override 
Documentation inherited. More...  
void  PreUpdate (const UpdateInfo &_info, EntityComponentManager &_ecm) override 
Documentation inherited. More...  
Public Member Functions inherited from System  
System ()=default  
Constructor. More...  
virtual  ~System ()=default 
Destructor. More...  
Detailed Description
This class provides hydrodynamic behaviour for underwater vehicles It is shamelessly based off Brian Bingham's plugin for VRX. which in turn is based of Fossen's equations described in "Guidance and Control of Ocean Vehicles" [1]. The class should be used together with the buoyancy plugin to help simulate behaviour of maritime vehicles. Hydrodynamics refers to the behaviour of bodies in water. It includes forces like linear and quadratic drag, buoyancy (not provided by this plugin), etc.
System Parameters
The exact description of these parameters can be found on p. 37 of Fossen's book. They are used to calculate added mass, linear and quadratic drag and coriolis force.
 <xDotU>  Added mass in x direction [kg]
 <yDotV>  Added mass in y direction [kg]
 <zDotW>  Added mass in z direction [kg]
 <kDotP>  Added mass in roll direction [kgm^2]
 <mDotQ>  Added mass in pitch direction [kgm^2]
 <nDotR>  Added mass in yaw direction [kgm^2]
 <xUU>  Stability derivative, 2nd order, x component [kg/m]
 <xU>  Stability derivative, 1st order, x component [kg]
 <yVV>  Stability derivative, 2nd order, y component [kg/m]
 <yV>  Stability derivative, 1st order, y component [kg]
 <zWW>  Stability derivative, 2nd order, z component [kg/m]
 <zW>  Stability derivative, 1st order, z component [kg]
 <kPP>  Stability derivative, 2nd order, roll component [kg/m^2]
 <kP>  Stability derivative, 1st order, roll component [kg/m]
 <mQQ>  Stability derivative, 2nd order, pitch component [kg/m^2]
 <mQ>  Stability derivative, 1st order, pitch component [kg/m]
 <nRR>  Stability derivative, 2nd order, yaw component [kg/m^2]
 <nR>  Stability derivative, 1st order, yaw component [kg/m] Additionally the system also supports the following parameters:
 <waterDensity>  The density of the fluid its moving in. Defaults to 998kgm^3. [kgm^3, deprecated]
 <water_density>  The density of the fluid its moving in. Defaults to 998kgm^3. [kgm^3]
 <link_name>  The link of the model that is being subject to hydrodynamic forces. [Required]
 <namespace>  This allows the robot to have an individual namespace for current. This is useful when you have multiple vehicles in different locations and you wish to set the currents of each vehicle separately. If no namespace is given then the plugin listens on the
/ocean_current
topic for aVector3d
message. Otherwise it listens on/model/{namespace name}/ocean_current
.[String, Optional]  <default_current>  A generic current. [vector3d m/s, optional, default = [0,0,0]m/s]
Example
An example configuration is provided in the examples folder. The example uses the LiftDrag plugin to apply steering controls. It also uses the thruster plugin to propel the craft and the buoyancy plugin for buoyant force. To run the example run.
To control the rudder of the craft run the following
To apply a thrust you may run the following command
The vehicle should move in a circle.
Ocean Currents
When underwater, vehicles are often subject to ocean currents. The hydrodynamics plugin allows simulation of such currents. We can add a current simply by publishing the following:
You should observe your vehicle slowly drift to the side.
Citations
[1] Fossen, Thor I. Guidance and Control of Ocean Vehicles. United Kingdom: Wiley, 1994.
Constructor & Destructor Documentation
◆ Hydrodynamics()
Hydrodynamics  (  ) 
Constructor.
◆ ~Hydrodynamics()

override 
Destructor.
Member Function Documentation
◆ Configure()

overridevirtual 
Documentation inherited.
Implements ISystemConfigure.
◆ PreUpdate()

overridevirtual 
Documentation inherited.
Implements ISystemPreUpdate.
The documentation for this class was generated from the following file: