project specification

µAUV²

A small, autonomous underwater vehicle for deep sea exploration. A system for evaluating behavior-based controls for autonomous underwater vehicles under conditions that approximate those found at the ocean depths. The system operates in fields of application where bigger systems would fail. The µAUV² has four active degrees of freedom that allow freedom of movement in all directions. It can recognize underwater obstacles and signal sources through the use of light sensors and LEDs. Sensors such as cameras have to be mounted in a way that the acquired data can be used for navigation as well as inspection tasks.

Specifications

Length 270 mm
Width 156 mm
Height 182 mm
Degrees of freedom (DOF) 4
Weight1.2 kg
Maximum speed 1.5
Thrusters Maxon RE 10 DC motors in a 6V/1.5W configuration
rotated by Krick micro pile gear motors
Camera 2 Semiconductor MT9V022 digital cameras with wide VG

Overview

A system for evaluating behavior-based controls for autonomous underwater vehicles under conditions that approximate those found at the ocean depths. The system operates in fields of application where bigger systems would fail. 

The µAUV² has four active degrees of freedom that allow freedom of movement in all directions. It can recognize underwater obstacles and signal sources through the use of light sensors and LEDs. Sensors
such as cameras have to be mounted in a way that the acquired data can be used for navigation as well as inspection tasks.

  • The main body of the μAUV2 consists of three parts:
    2 hollow acrylic glass domes, one at the front of the system and one at the back. These two domes build the hull protecting the inner part of the AUV from water up to a depth of 2.5 m. Both domes are transparent to allow optical sensors to monitor the environment.
  • 1 central base frame made of aluminium which connects the two acrylic domes. This frame also serves as a carrier for all three thrusters and the battery pack.

3 thrusters are responsible for moving the μAUV2 in all directions. The top thrusters can be turned independently at 90 degrees. The two side thrusters can be synchronously turned 90 degrees as well.

The μAUV2 contains a buoyancy tank. This buoyancy or ballast water tank enables the μAUV2 to float energy efficiently at a certain depth in the water column. The tank can be filled and emptied with a peristaltic pump. The ballast water tank itself is a simple convoluted rubber gaiter.

The μAUV2 has several complementary sensors to control the thrusters and to navigate autonomously
under water. It's equipped with two digital cameras, one pointing downward and one pointing ahead. To measure the attitude of the vehicle, an Inertial Measurement Unit (IMU) is added. A differential pressure sensor is used to determine the depth of the vehicle. The current inclination of the thrusters can be measured by potentiometers which are mounted on the turning axis. The speed of the thruster and pump motors is measured with quadrature encoders.

Long range communication channels like Long Baseline Modems (LBLs) are too bulky for a miniaturized AUV and due to their low frequency range acoustic methods do not have the capability to transmit a huge amount of data in an appropriate time. In contrast, optical communication methods provide a throughput which is high for certain wavelengths. For these reasons, the μAUV2 is equipped with an optical communication module that was developed at the DFKI.

References

Presents the system design and development, the identification of system parameters and first control approaches.

H. Hanff, P. Kloss, K. Schmid, et al. - August 2016.

Wevolver 2022