Thinking in Terms of Systems for ROV

Introduction to Systems

In engineering, many complex mechanical and electrical machines may be made of many different and interconnected parts. An underwater vehicle may have hundreds if not thousands of parts that work together to perform an overall function; to dive, to surface, to maneuver, or to record and transmit data, for example.

We may find it difficult to think about the whole as the sum of all of those parts. For example, your body is made up of 100 trillion cells, 22 internal organs, 206 bones, enzymes, biomes, and other parts. One way to make sense of all those parts is to divide them into groups of parts that together perform a collective function. We call these specialized groups of parts a system. For example, your body can be divided into systems, such as the nervous system, the circulatory system, and the digestive system. (Moore et al., 2010, p76)

We can define any system in the following way, “A system is a collection of parts (and/or processes) that work together to do (or be) something the individual parts cannot do (or be) alone.” (Moore et al., 2010, p75)

We can also identify a system by some common characteristics (Moore et al., 2010, p75):

Systems are made up of parts.
All of these parts must interact with each other.
A new feature or function emerges from the interaction of those parts in that system. This new feature or function of the system is called an emergent property.

ROV Systems

In designing and building an ROV, it is possible to arrange many of its different parts into specific systems that exhibit some collective property, its emergent property, that helps us to simplify the complex workings of our ROV.

As an example, a simple ROV can be subdivided into the following systems (Moore et al., 2010, p77):

Structure/Frame

The structure/frame of an ROV holds all of the ROV’s components in a spatial arrangement. All of the parts are attached to a skeletal framework which provides a rigid base to keep all the parts properly aligned and organized. The frame/structure can also provide some protection from collisions or pressure.

Tether

The tether of an ROV refers to the wired connection between the ROV and the surface operations. Tethers transmit power and control to the ROV and can transmit data and visual information to the operator on the surface.

Propulsion

The propulsion system of an ROV provides the trust necessary to move and maneuver the ROV through water. Subsystems of the propulsion system can include the electric motor, propeller, and waterproof housing.

Payload

The payload of an ROV can consist of systems that augment the capabilities of the ROV to perform specific tasks underwater. An example payload can be a remotely operated gripper, or robotic arm, to retrieve items from underwater. Operators need to define the objectives of an underwater mission or task in order to add the proper payload to accomplish the mission.

Ballast

The ballast system adjusts the ROV’s buoyancy to manage the ROV’s tendency to float or sink. Some ROV’s are tuned to be slightly positively buoyant to allow the ROV to passively surface in case the ROV were to malfunction. Many small ROVs also use a static ballast system where the buoyancy is pre-set and remains unchanged throughout the dive and if the ballasting of the ROV is set very close to neutral buoyancy, a vertical thruster is used for depth control (Moore et al., 2010, p282).

Navigation Sensors

The navigation sensors give the human operator the information needed to determine where the ROV is and what it’s doing.

Power

The power system of an ROV provides and distributes the electrical power to run and operate an ROV’s many systems.

Control

The control system is the interface between a human operator and the ROV. This system allows a human operator to control the thrusters, tools, cameras, lights, or other equipment on board an ROV.