Page 133 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

Thrusters 6 CHAPTER CONTENTS
6.1 Propulsionandthrust....................................................................................................................122
6.1.1 Propulsion systems...................................................................................................123 6.1.2 Thrusterbasics.........................................................................................................124 6.1.3 Thrusterdesign........................................................................................................126
6.2 Thrusters and speed......................................................................................................................134
6.3 Electric versus hydraulic...............................................................................................................135
As a part of any mobile robotic system, some means of locomotion is necessary in order to move the robotic system. In free-swimming ROV technology, thrusters rule. Thrusters are a critical design consideration for any ROV system. Without the proper thrust the vehicle can be overwhelmed by the environmental conditions and thus unable to perform the desired tasks. This chapter will address the basics of thruster design and placement on the vehicle and pro- vide examples of some of today’s leading thruster designs. The final section will discuss the over-arching question of which type of thruster to choose (electric or hydraulic), and ulti- mately which type of vehicle (all electric, all hydraulic, or a combination) should be chosen for the job. Examples of the full range of electric and hydraulic vehicles currently available on the open market are provided. But first, a discussion of the dreaded “design spiral” is warranted.
It is simple at first blush. The designer must determine what size thruster is needed for the vehi- cle. The decision process goes something like this:
• What is the task that must be done and thus the work system and tools necessary for the ROV? (There is no sense sending in a vehicle if it cannot do the task—which could be as simple as observation or as complex as changing out an AX ring or rigging a shackle.)
• What size power system is necessary to support the work system and tools (and the other electrical components: control system, lights, cameras, etc.)?
• What size frame and amount of buoyancy are necessary to support the power and work system?
• What are the physical and environmental conditions (current, depth, required operational
footprint, etc.)?
• What is the drag on the vehicle and cable to meet the operating conditions and footprint?
The ROV Manual.
© 2014 Robert D Christ and Robert L Wernli. Published by Elsevier Ltd. All rights reserved.
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