Maritime Tutorial 5 : Adding Heave Compensation

In this training pack, we will go over key concepts and guidelines to get you started with nautical simulations in Vortex® Studio.

This module focuses on using Vortex Studio a Python script coupled with the GSPID Controller object to implement a heave compensation system.

Prerequisites

You need to have Vortex® Studio and the Vortex Studio Demo Scenes installed to be able to follow all steps in this tutorial. Working knowledge of Python or coding languages in general will facilitate the understanding of this module as well.

Adding a GSPID Controller

1. Start the Vortex Studio Editor. Open OffshoreCrane.vxmechanism. This is the mechanism you created in Marine Module 3: Building an Offshore Crane

2. Double-click on GSPID Controller from the Dynamics section of the Toolbox to add it to the scene.

3. Rename the GSPID to "Heave Compensation Controller".

Modifying the Control Script

1. Right-click on the ControlScript script and click on Edit.

2. Add the following inputs:

   
   
   

3. Add the following outputs:

   
   
   

   
   
   

4. In the Code section of the script, replace the code with the following:

   from VxSim import *     def on_add_to_universe(self, universe):     self.heaveCompToggle = False     self.activateHeaveComp = False     def pre_step(self):     # Toggle Heave Compensation     if self.inputs.Activate_Heave_Comp.value and not self.heaveCompToggle:         self.heaveCompToggle = True         self.activateHeaveComp = not self.activateHeaveComp     elif not self.inputs.Activate_Heave_Comp.value:         self.heaveCompToggle = False       self.outputs.Arm_Actuator_Velocity.value = self.inputs.Arm_Actuator.value * 0.2     self.outputs.Elbow_Actuator_Velocity.value = self.inputs.Elbow_Actuator.value * 0.2       if (self.inputs.Hoist_Up.value):         drumVelocity = -0.2     elif (self.inputs.Hoist_Down.value):         drumVelocity = 0.2     else:         drumVelocity = 0.0       self.outputs.Hook_Current_Position.value = self.inputs.Hook_Position.value.z       if not self.activateHeaveComp:           self.outputs.Drum_Velocity.value = drumVelocity         self.outputs.Hook_Desired_Position.value = self.outputs.Hook_Current_Position.value       elif self.activateHeaveComp:                   self.outputs.Hook_Desired_Position.value += 0.1*drumVelocity         self.outputs.Drum_Velocity.value = self.inputs.PID_Value.value               self.outputs.Turret_Slew_Velocity.value = self.inputs.Turret_Slew.value * 0.2

   
   
   

5. Click on Apply.

6. Save the mechanism.

Connecting the PID's Inputs and Outputs

1. Access the Connection Container by double-clicking on it.

2. From the ControlScript script, drag-and-drop the recently added Inputs and Outputs.

3. From the Heave Compensation Controller, drag-and-drop Setpoint, Process Variable and Control Output.

4. From the Joystick, drag-and-drop the Y button (Button4) to the Connection Container.

5. Drag-and-drop the World Transform of the Platform_KnuckleBoom_Hook part of the Hook assembly into the Connection Container.

6. Make the connections as shown:
   
   

   Open

   

Testing and Adjusting the PID's Parameters

1. Access the Properties of the Heave Compensation Controller PID.

2. From the Gain Range section, set the gain ranges of the PID to these values :
   
   

   Open

   

3. Save the mechanism.

4. Open MarineScene.vxscene

5. Open a Plotter Window by clicking on the Plotter button.

6. Drag-and-drop Current Value and Desired Value inputs from the Heave Compensation Controller script into the plotter window.

7. Start the simulation and activate the heave compensation by clicking on the Y button on the gamepad.

8. Modify the PID parameters in order to fine tune the response of the module's depth.

Up Next: Maritime Tutorial 6 : Adding an Animated Buoy