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[Part 1 of this article discusses the major components of a typical remotely operated vehicle system along with everyday underwater tasks ROVs perform. Part 2 looks at the primary subsystems of an ROV - including lighting, cameras, sensors and manipulators - and considers specific issues regarding the tether, power, data, and the connectors.]
3.4 CONTROL SYSTEMS
The control system controls the different functions of the ROV, from controlling the propulsion system to switching of the light(s) and video camera(s). From simple relay control systems in the past to today's digital fiber optics, these systems are equipped with a computer and subsystem control interface. The control system has to manage the input from the operator at the surface and convert it into actions subsea. The data required by the operator on the surface to accurately determine the position in the water is collected by sensors (sonar and acoustic positioning) and transmitted to the operator.
Over the last 10-15 years, computers utilized for these purposes have been designer computers with sophisticated computer programs and control sequences. Today, one can find standard computers in the heart of these systems. There has been a shift back to simpler control systems recently with the commercial advent of the PLC (Programmable Logic Computer). This is used in numerous manufacturing processes since it consists of easily assembled modular building blocks of switches, analog in/outputs, and digital in/outputs.
3.4.1 The Control Station
Control stations vary from large containers, with their spacious enclosed working area for work class systems, to simple PC gaming joysticks with PHDs (personal head-mounted displays) for some micro-ROV systems. All have in common a video display and some form of controlling mechanism (normally a joystick, such as at Figure 3.23). On older analog systems, a simple rheostat controls the variable power to the electric motors, while newer digital controls are necessary for more advanced vehicle movements.
Figure 3.23 Industrial joystick and circuit board used in vehicle control.
With the rise of robotics as a sub-discipline within electronics, further focus highlighted the need to control robotic systems based upon intuitive interaction through emulation of human sensory inputs. Under older analog systems, a command of 'look left/go left' was a complex control command requiring the operation of several rheostats to gain vector thrusting to achieve the desired motion. As digital control systems arose, more complex control matrices could be implemented much more easily through allowing the circuit to proportionally control a thruster based upon the simple position of a joystick control.
The advent of the modern industrial joystick coupled with programmable logic circuits has allowed easier control of the vehicle while operating through a much simpler and more intuitive interface. The more sensors available to the 'human' that allow intuitive interaction with the 'robot', the easier it is for the operator to figuratively operate the vehicle from the vehicle's point of view. This interaction protocol between operator and vehicle has become known as the Human-Robot Interface and is the subject of intensive current research. Look for major developments within this area of robotics over both the short and long terms.