**4. Simulation results with understanding on maritime standards**

By the classification standards in the maritime industry, all virtual simulators are assigned with a "Class" namely: Class A, B, C or Class S [14]. The class of a simulator is assigned based on the requirements of the simulator on the checklist provided by the classification society. The comparisons will be made with the standards proposed by DNV (Det Norske Veritas). The comparisons are not meant to be exhaustive but should provide adequate information for designing the virtual simulator.

From the results presented by the project, according to the standards of the classification society DNV, it can be seen that there are some criteria that the proposed Unity3D simulator could not meet. As seen in **Table 2**, items 1.1.19, 1.1.20 and 1.1.21 or any items related to the instructor, these requirements were not met because of the simulator was developed for a single purpose to train the ROV pilot in detecting a leak on a pipeline inspection. Therefore, it did not take into account an instructor to test the competency of the ROV pilot. Another observation in **Table 3** on the behavioral realism for items 2.1.1, 2.1.2, 2.1.5, 2.1.7 and 2.1.8, the class requirements were not fulfilled as the simulation does not encompass an underwater current acting on the objects in the scene. Simulation of actual underwater currents will affect the virtual objects and ROV to make the simulator more realistic. But one would require real information or data to implement it. It was not performed in this chapter. In **Table 4**, items 3.1.2, 3.1.4, 3.1.6 and 3.1.8 under the operating environment require a basic version of turbidity, sea state, underwater fog and camera in the virtual scene. However, some items were included such as camera and underwater lighting in the scene as shown in **Figure 9**. Others were not added due to the lack of actual specifications of these items.

Lastly, as seen in **Table 5**, casualty simulation was not met. The simulation did not have casualty simulation for the ROV. It did not include other equipment malfunctions besides the leakage that occurred in one of the pipelines (see **Figure 10**). In summary, the primary simulator produced has shown that Unity3D possesses the good capability to develop a more realistic virtual simulation for training purposes. Further developments of the simulator were performed to meet these class requirements. For example, a pathfinding algorithm (see **Figure 11**) was used to simulate the autonomous mode of the ROV.

In the virtual simulation, the pathfinding algorithm helps to build the autonomous mode feature in the ROV. Several waypoints were placed in the scene to better guide the ROV along its inspection path. However, using this method, the ROV would pass through the terrain to reach its next point. Few blocks were placed within the terrain to act as obstacles along the pathfinding. They appeared invisible in the simulator as their mesh renders can be switched off. However, the proposed guidance system would only be applicable if the simulated ROV carries out its autonomous functions at a fixed depth. A comprehensive way to create an autonomous guidance system for the ROV was to use a NavMesh algorithm as implemented in **Figure 11**. Any scene can easily be navigated by a GameObject with a NavMesh agent component. The NavMesh allows the simulated ROV to detect the size and height of objects in the scene that cannot pass through. The UI can be improved through the implementation of the User Interface where control buttons can be placed on the screen to allow the pilot to toggle them easily. The buttons on the GUI will serve to remind the pilot if a specific function is switched "on" or "off". As shown in **Figure 9**, the intended ROV GUI for the simulator with a button in the scene to toggle between the multiple camera views and front light on the ROV was implemented. As mentioned, the simulation of underwater currents will help the simulation to look more realistic for the pilot. With the physics supported by Unity3D, the ROV in the simulation can be subjected to these forces and moments caused by the underwater current. It will be implemented in the future works.

The simulation test results will focus on pipeline inspection tasks near to the seabed. The different parts of developing the simulation are integrated together with a scenario set up where there is a gas leakage in one of the jumpers in the top section of the subsea system. First, the ROV's


**Table 2.** Classification standards for physical realism.

task was to identify the location of the leakage, and second, the ROV will need to deactivate the whole system by pressing the switch on the subsea system. The data for the search operation were exported and plotted into a graph, and a video of the simulation was recorded.




**Table 4.** Classification standards for operating environment.

As seen in **Figures 12** and **13**, the ROV starts at position (0, −793, 0 m), which is at the center of the subsea production layout. The ROV then rotates about its Y-axis in an anti-clockwise direction shown in **Figure 13**, where the ROV's heading is facing approximately 190° away from its global coordinate before it starts moving in X and Z-direction again. As shown in **Figure 14**, the ROV moves along at a constant depth of −793 m for the first 38 s before it moves up as the vehicle is too close to the seabed (to avoid collision). In **Figures 15** and **16**, the forward and lateral thrust (in N) produced by the ROV increases to reach the targeted location, i.e., to maneuver to the desired position. The thrusts reduce once the gas leakage

**Figure 9.** GUI with buttons to toggle between cameras and lighting.


**Table 5.** Classification standards for casualty simulation.

**Figure 10.** Leakage in pipeline.

Virtual Simulation Platform for Training Semi-Autonomous Robotic Vehicles' Operators http://dx.doi.org/10.5772/intechopen.79600 101

**Figure 11.** Obstacles in the virtual scene.

**Figure 12.** X and Y positions of ROV at the different time frame.

**Figure 13.** Z position of ROV at various time frames.

and subsea system are found. **Figures 12**–**14** show less fluctuating in the motion along the X, Z-axis, and yaw. The position of the ROV increases along the Z-axis while its position along the X-axis remains quite constant. The ROV makes a turn around the Y-axis (clockwise) to approximately 280° at 87 s where the position of the ROV increases along the X-axis and remain quite constant on the Z-axis. After approximately 140 s later, the ROV has reached the top section of the subsea system where the gas leakage is located in **Figure 10**.

**Figure 14.** Yaw of ROV at various time frames.

**Figure 15.** Forward thrust at different time frame.

**Figure 16.** Lateral thrust at different time frame.

The left manipulator of the ROV was activated using a button on the GUI control panel to shut down the subsea system due to the leakage. The ROV can reach the targeted position and shut down system successfully after about 202 s. With the presence of the obstacles in the scene, the objects can interact with one another as though in the real environment. There was no obstacle being hit. The ROV pilot managed to find the gas leakage before reaching the targeted top section of the subsea system to deactivate the switch to prevent more leakages from happening. A sample of the simulation results obtained from the ROV simulator is summarized in **Table 6**.


**Table 6.** Simulated results obtained from ROV pilot simulator.
