Advances in and extended application areas for Doppler sonar

Acoustic Doppler Current Profilers (ADCP´s) and Doppler Velocity Logs (DVL´s) are sonar sensors which apply principles of Doppler shift to measure velocity of particles in water, or to measure the velocity of vehicles moving in the water with respect to the ocean floor. They have been in use for 30 years for measuring currents and flow in oceans, rivers, and lakes, and as navigation instruments that allow autonomy in Remote Operated Vehicles (ROV´s) and Autonomous Underwater Vehicles (AUV´s). Classically, because of size and weight, the use of these sensors has been restricted to larger underwater vehicles and have been limited to medium ranges measurement of a few hundred meters. Longer range, lower frequency sensors have classically been limited to surface operations. Recent advances in materials and in design over the past few years have significantly extended the application areas where these sensors can be adopted, both for large low frequency sensors capable of greater depths, and for very small sensors opening up the realm of autonomous control to more small size vehicles. This presentation will describe the advances in designs and materials, will demonstrate the increased range achieved by new sensors, and will demonstrate how small sensors have expanded the application of small AUV´s and ROV´s. In terms of design, Phased Array technologies present significant advantages over piston arrays in terms of weight, size, and range. The presentation will describe the benefits as well as the drawbacks and compromises that the Phased Array sensors provide. Examples of integration into small one-man portable AUV´s such as the OceanServer IVER-2 and ROV´s such as the VideoRay Pro-IV that were not possible using earlier piston array sensors will be shown. Results of the navigation improvement that was achieved on these vehicles as a result of the integration will also be shown. Similarly, results showing the extended range that has been achieved with phased arr- ys compared to the equivalent Piston Array sensor will also be shown for 150 kHz and 600 kHz sensors. Both simulation and ocean test results will be shown. Advances in depth-rating of large Phased Array sensors using oil-filling techniques have extended the areas of application for these sensors that were previously only vessel or platform mounted at the surface. With extended depth-rating, applications in the oil and gas and renewable energies areas for current profiling which were not previously possible can now be achieved. This will have an effect on monitoring of currents for safety, efficiency, and general oceanographic current measurements. Oceanographic studies for current profiling which often require expensive deployments using lowered ADCP techniques can be performed more efficiently and continuously, and more cost-effectively, using these depth-rated low frequency phased array sensors. In addition to increased depth-rating due to oil-filling, the migration of integrated electronics from smaller sensors onto the large low frequency sensors provide a new long-range navigation capability that can be used on large submersible platforms which could never previously be achieved. Bottom-Tracking Ranges approaching 2000 meters from a submerged platform are now possible. This presentation will demonstrate test results and simulation for depth rating and range of these new platforms.