Unmanned Untethered Submersible Research Articles

On the Linear Hydrodynamic Forces and the Maneuverability of an Unmanned Untethered Submersible with Streamlined Body (2nd Report : Lateral Motions)

A series of captive model tests was carried out to unmanned untethered submersible AUV-HMl testbed, which has a body of a streamlined section, developed at National Taiwan University. Furthermore, for estimating its lateral stability derivatives the same method, which is based on the empirical formula proposed by Bottaccini and used in previous paper, is applied. As a result, both of the two sets of stability indices evaluated with estimated values of stability derivatives as well as those obtained by measurement, show that AUV-HMl testbed is unstable on lateral mode. This result agrees well with the tendency shown by the vehicle responses for step heading commands in the pool test performed with the AUV-HMl testbed.

On the Linear Hydrodynamic Forces and the Maneuverability of an Unmanned Untethered Submersible with Streamlined Body

A series of captive model tests was carried out to measure the stability derivatives of an unmanned untethered submersible AUV-HM1 testbed, which has a body of a streamlined section, developed at National Taiwan University. Furthermore, for estimating its' stability derivatives, a method based on the empirical formula proposed for standard torpedoes by Bottaccini is investigated. The estimated values of stability derivatives are examined and compared with those obtained by measurement. As a result of comparison, the validity of the method is confirmed. It was also shown that the maneuverability of the submersible can be evaluated by the method with accuracy enough for practical use.

Study on Linear Hydrodynamic Forces and Control Response on Unmanned Untethered Submersible

A method for estimating the linear hydrodynamic forces acting on unmanned untethered submersibles is investigated. Two models are selected as examples, one has a slender body with a purpose to lower drag as in the case of a laminar flow aerofoil section, and the other has a body of an aerofoil section suited for gliding performance.The estimated values of stability derivatives are examined and compared with the measured values by PMM test, and are proved to be satisfactorily accurate. To analyze dynamic motion characteristics, simulations of stability and control response are carried out. The advantage of the proposed method of estimation are demonstrated for the stage of initial design.

Design of Unmanned Untethered Submersible for Quick Swimming

Unmanned vehicles have great advantage for' survey of sea bed in the deep sea. Many models of tethered submersibles have been developed as devices for exploitation of subsea oil resources. In the deep sea, drag force acting on the umbilical cable prevents tethered submersible from swimming freely ; therefore, the development of untethered submersibles is highly expected, which are free from restriction of the umbilical cable. But few researches relating to unmanned untethered submersibles have been performed because of their disadvantages such as slow rate of communication between the surface support ship and the vehicle, and limit of energy supply. It is essential for unmanned untethered submersibles to swim autonomously and with a small amount of battery energy consumption.In this paper, a concept of gliding submersibles is proposed for inspection of the surface of sea bed along a long measurement line. The submersible glides, descents autonomously from the surface without consuming battery energy and comes to the target point. Then it swims above the surface keeping constant height. A pilot model named PTEROA 40 is designed and its characteristics of longitudinal behaviors are examined analytically and experimentally.It is shown that a model of 1. 5 m length swims over 7 knots when the weight is 5% larger than the buoyancy of the vehicle. Longitudinal stability and maneuverability are also acceptable as a vehicle which should climb when there is an obstacle along the line of measurement.

Acoustic transmission of images using a microprocessor-based video bandwidth reduction technique

The problems associated with the acoustic transmission of real-time television pictures are considered in this paper. A solution to the high data rate video source is found in the application of a spatial data redundancy reduction algorithm, Micro Adaptive Picture Sequencing (MAPS). This algorithm has been implemented on two commercially available microprocessors (M68000), which operate on a digitized image to produce a coded image which is transmitted and reconstructed. Using the spatial data reduction algorithm it is possible to transmit 1 to 2 frames per second of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">96 \times 96 pixel \times 4</tex> bits gray level image over a 9600 baud link. Although these images do not possess the full dynamic range and resolution of home quality video, this work suggests that the acoustic channel could be utilized for control of an unmanned untethered submersible. Also, the transmission of high resolution information is made practical when some data reductions are performed prior to acoustic transmission.