Jonas Jonsson

Miniaturized submersible for exploration of small aqueous environments

Remotely operated vehicles (ROVs) are commonly used for sub-surface exploration. However, multi-functional ROVs tend to be fairly large, while preferred small and compact ROVs suffer from limited functionality. The Deeper Access, Deeper Understanding (DADU) project aims to develop a small submersible concept using miniaturization technologies to enable a high functionality. An operator is able to maneuver the vehicle with five degrees of freedom using eight small thrusters, while a set of accelerometers and gyros monitor the orientation of the submersible. A single fiber optic cable will connect the submersible to a control station and enable simultaneous data and command transfers. Rechargeable battery packs provide power to the submersibles subsystems during operation. These will be rechargeable through the fiber connection. A forward looking camera is aided by a laser topography measurement system, where distances, sizes and shapes of objects in view can be determined to within 0.5 cm. For murkier environments, or when a more extensive mapping of the surroundings is needed, the small high-frequency side-scanning sonar can be used. Salinity calculations of the water will be available through measurements of the conductivity, temperature and depth. Samples of water and particles within it will be enabled through a water sampler with an enriching capability. Flow sensors will be able to measure the water movement around the submersibles hull. The submersible and its subsystems are under continuous development. The vehicle itself, and its subsystems as stand-alone instruments, will enable the exploration of previously unreachable submerged environments, such as the sub-glacial lakes found in Iceland and Antarctica, or other submerged small environments, such as pipe and cave systems.

A latchable high-pressure composite valve actuator combining paraffin and a low melting point alloy

This work presents a latchable valve microactuator for use in high-pressure environments, for instance deep-sea sampling in missions of long duration. Mounted on a minisubmersible, it can be used in confined spaces, earlier virtually unreachable. However, the device can be used in any high-pressure application where long open and/or closed times are required, and power supply is an issue. The actuator is fabricated using standard batch-processes as photochemical machining, wet etching and lithography. Focus of this work is on the endurance of the actuator to facilitate a bistable valve. The actuator managed to keep a deflected position for almost 50 hours at 1.8 MPa applied pressure, after which the experiment was aborted.

Towards Chip-Based Salinity Measurements for Small Submersibles and Biologgers

Water’s salinity plays an important role in the environment. It can be determined by measuring conductivity, temperature, and depth (CTD). The corresponding sensor systems are commonly large and cumbersome. Here, a 7.5 × 3.5 mm chip, containing microstructured CTD sensor elements, has been developed. On this, 1.5 mm2 gold finger electrodes are used to measure the impedance, and thereby the conductivity of water, in the MHz frequency range. Operation at these frequencies resulted in higher sensitivities than those at sub-MHz frequencies. Up to 14 kΩ per parts per thousand salt concentration was obtained repeatedly for freshwater concentrations. This was three orders of magnitude higher than that obtained for concentrations in and above the brackish range. A platinum electrode is used to determine a set ambient temperature with an accuracy of 0.005°C. Membranes with Nichrome strain gauges responded to a pressure change of 1 bar with a change in resistance of up to 0.21 . A linear fit to data over 7 bars gave a sensitivity of 0.1185 /bar with an of 0.9964. This indicates that the described device can be used in size-limited applications, like miniaturized submersibles, or as a bio-logger on marine animals.

2-D Thermal Velocity Sensor for Submersible Navigation and Minute Flow Measurements

A 2-D thermal velocity microsensor for use as a navigational aid and for flow measurements on a miniaturized submersible is developed in this paper. The sensor with nickel heater and temperature sensors on a Pyrex substrate, designed for mounting on the outside of the submersible hull, is fabricated and tested in an application-like environment and proven to be able to measure water speed from zero to 40 mm/s with a power consumption less than 15 mW and determine the flow direction with an error less than ±8°. Finite Element Analysis is used to investigate design and operation parameters and possible biofouling effects on the sensor signal. The effect on shape and orientation of the sensors mounting surface is also studied.

Enclosure-Induced Interference Effects in a Miniaturized Sidescan Sonar

On, for instance, the miniaturized submersible explorer, Deeper Access, Deeper Understanding (DADU), only 20 cm in length and 5 cm in diameter, the sidescan sonar needs to be tightly mounted in the hull. Finite element analysis (FEA) as well as physical measurements were used to investigate the effects of beam interaction with acoustically nearby rigid boundaries. Computer simulations showed the first major dip in the beam shape to vary in strength, size, and position with the enclosure wall height, from a position of 47 at 0.0-mm wall height to 32 at 3.0-mm wall height. Hydrophonic measurements on the manufactured test device confirmed these values to within 9%, varying between 47 and 29 . In addition, Schlieren imaging was proposed and used as a noninvasive means of qualitative beam shape characterization. A field test was performed with the enclosure height set to 0 and 3 mm. With the latter height, a dark band, corresponding to a sonar sensitivity dip at about 30 in the beam, appeared in the sonar image. It was found that the beam shape is sensitive to small mounting errors, in this case where the wavelength of the sonar is on the same size scale as the enclosure. Furthermore, it was found that FEA models can be used to accurately predict enclosure effects on sonar beam shapes, and Schlieren imaging can be used to visually detect the shape deformations in mounted sonar devices.

A compact projection system enabling topographical measurements for a miniaturized submersible explorer

To enable photogrammetry of underwater images using a miniaturized submersible explorer, a compact projection system has been developed. By registering the deformation of a known projected pattern, using a laser and a diffractive optical element (DOE), the distance to, shape and size of an object can be calculated. The DOE has been designed, using in-house developed software, and manufactured using microstructure technology. Distances to objects 45 to 30 cm away were determined to within 0.5 cm, and the developed GUI was able to recreate the shape from the measurements for easier examination of the object.