Semi-Autonomous Underwater Vehicle for Intervention Missions (SAUVIM)

SAUVIM is for 6,000m depth. It has a robotic arm, various on-board sensors, batteries, VxWorks real-time controller, multi CPUs, and various advanced software.

Objective :
The primary research objective is to develop a Semi-Autonomous Underwater Vehicle for Intervention Missions (SAUVIM). Unlike the fly-by autonomous underwater vehicles (AUV), SAUVIM will have a manipulator work package. It will require an advanced control system and a precise sensory system to maintain high accuracy in station keeping and navigation.

Background:
Most intervention missions, including underwater plug/unplug, construction & repair, cable streaming, mine hunting, and munitions retrieval- require physical contact with the surroundings in the unstructured, underwater environment. Such operations always increase the level of risk and present more difficult engineering problems than fly-by and non-contact type operations. For these intervention operations, the vehicle requires a dexterous robotic manipulator; thus the overall system becomes a high degree-of-freedom (dof), multi-bodied system from the coupling effects of the high degreee of accuracy even in the presence of unknown, external disturbances, i.e. undersea currents. All these issues present very complex engineering problems that have hindered the development of AUVs for intervention missions. Currently, the state-of-the-art in machine intelligence is insufficient to create a vehicle of full autonomy and reliability, especially for intervention missions.

Development :
Five major components:

Adaptive, Intelligent Motion Planning;
Automatic Object Ranging and Dimensioning;
Intelligent Coordinated Motion/Force Control;
Predictive Virtual Environment; and
SAUVIM Design.

SAUVIM Design (SD)
This task is the main objective of the SAUVIM project for Phase 1. It is an effort to design and develop efficient, reliable hardware/software architectures of SAUVIM. Due to the immense demand of this task, it is divided into five sub-tasks, which are Reliable, Distributed Control (RDC), Mission Sensor Package (MSP), Hydrodynamic Drag Coefficient Analysis (HDCA), Mechanical Analysis and Fabrication (MAF), and Mechanical-Electrical Design (MED).

The goal of RDC is to develop a reliable and efficient computing architecture for signal and algorithmic processing of the entire SAUVIM system. The proposed system is a multi-processor system based on a 6U VMEbus and the VxWorks real-time operating system. This system is capable of high processing throughput and fault tolerance. Currently the system consists of two VMEbuses, which are the navigation control system and the manipulator control system. The main VMEbus, or the navigation control system, has two Motorola M68060 CPU boards, a multi-port RS232 interface board, and an I/O board with a Pentium MMX processor based PC104+ board, which is connected via a RS232 port. The navigation control system handles the communication, supervision, planning, low-level control, self-diagnostics, video imaging, etc. The data exchange between the two CPUs is conducted via shared memory. The second VMEbus, or the manipulator control system, has one Motorola M68040 CPU and an I/O board. Two PC104 boards are connected serially to this CPU. The manipulator control system is independent and dedicated to the manipulator control. Many of the hardware components have been tested and are being interface with its respective software systems. Various optimization changes have been implemented to minimize communication and computation. This development will continue throughout the vehicle's development process.

The objective of the MSP is to provide semi-continuous records of SAUVIM water depth, temperature, conductivity, computed salinity, dissolved oxygen, magnetic signature of the seafloor, pH and turbidity during the survey mode. In the intervention mode, the MSP also provides compositional parameters at a selected seafloor target, including pumped samples from submarine seeps or vents. The MSP is an independent system with its own PC 104 CPU and its own power supply residing in a separate pressure vessel. All of the sensors have been purchased, and an initial field test at the Loihi Seamount has been conducted. Continual tests are being conducted to optimize the scientific sensor data-gathering capabilities.

The HDCA is used to determine the hydrodynamic coefficients via a numerical solution of full Navier-Stokes equations using PHOENICS, a commercial computational fluid dynamics (CFD) code. Initial results from the PHOENICS software have produced mixed results. The current vehicle fairing has produced a drag coefficient of 0.40; however, it has not yet been verified. Other CFD software and model testing is being conducted to verify the drag coefficient results before the implementation of the vehicle fairing on SAUVIM.

The MAF has three objectives. Its primary goal is to design and fabricate composite pressure vessels with end caps and connector openings for full ocean depths taking stress, buckling, Hygrothermal effects, and fatigue analysis into account; and its two secondary goals are to design and fabricate the SAUVIM fairing and to analyze the SAUVIM frame. A thorough analysis and comparison of the Ti-6Al4V, AS4/Epoxy, and AS4/PEEK pressure vessels manifest the advantage of composite materials in reduction of weight, size and strength. Using these results, a scaled model prototype using AS4/PEEK has been fabricated and tested. A l/3 sized prototype is being fabricated and will also be tested. For the shallow water vehicle test, a full-sized, fiberglass pressure vessel with aluminum end caps have been manufactured and tested. These vessels are being used to determine the final hardware layout. The aluminum frame has been designed and fabricated. A full-ocean depth pressure vessel of AS4/PEEK has been developed and is in its testing phase. The initial fairing analysis has been developed and expanded. Fairing optimizations are being considered.

The MED is the integration of the mechanical and electrical components for SAUVIM. First, the design specifications were established for the fairing, frame, instrument pressure vessels, buoyancy systems, mission sensor, passive arm and robotic manipulator tasks. Second, after scrutinizing review of SAUVlM's major components - i.e. sensors, actuators and infrastructure -in terms of power consumption, compatibility, weight distribution, buoyancy distribution, hydrodynamic effects and task effectiveness, all major components have been purchased. Technical drawings of the vehicle frame, fairing, and related sub-structures have been completed. Many of the mechanical and electrical components have been fabricated and are being integrated with the overall electrical layouts.

Last updated August 17, 2006