Page 168 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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156 CHAPTER 7 Power and Telemetry
hydraulics as tooling is typically interchangeable and will often induce contaminated oil into an otherwise sanitary hydraulic system. Clogged valves for manipulators or thrusters will produce unexpected movements, possibly compromising safety.
Other manufacturers use variations on this combination with single hydraulic circuits but intro- ducing multiple layers of filtering to reduce the possibility of oil contamination from tooling components.
7.2 Control systems
The control system manages the different functions of the ROV, from the propulsion system to driving valve packs and to the switching on and off of the light(s) and video camera(s). From sim- ple 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 past 1015 years, computers utilized for these purposes have been designer computers with sophisticated computer programs and control sequences. Today, one can find standard compu- ters 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.
7.2.1 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 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 that in Figure 7.15). On older analog systems, a simple rheostat con- trols the variable power to the electric motors, while newer digital controls are necessary for more advanced vehicle movements.
With the rise of robotics as a subdiscipline 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 com- mand 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 humanrobot interaction and is the subject of intensive current research. Look for major developments within this area of robotics over both the short and long terms.
