Control System

The standard sensors of ISiMI include an AHRS (attitude heading reference system), a pressure sensor, a CCD camera, and a voltage sensor to check the battery voltage. The AHRS supplies information on the 3-axis angular velocities, 3-axis accelerations, 2-axis inclinations, and heading to the control system. The depth information is gathered from the pressure sensor. A CCD camera mounted on the nose is used to detect the underwater dock at the final stage of the underwater docking for the terminal guidance.

The general arrangement of the parts of ISiMI is shown in Fig. 6. The core of ISiMI's control system is a single-board computer interfaced with a frame grabber, a serial extension board, and a controller area network (CAN) module via a PC104 bus. Figure 4 shows a block diagram of ISiMI's control system. The operating system of the main computer is Windows XP, with real-time extension (RTX). The application software for the graphic user interface and the dynamic control of ISiMI is implemented with Visual C++. To interface sensors and actuators with the main controller, a sub-controller using a Micro Controller Unit (MCU) was developed. The sub-controller communicated with the main controller via a CAN. It controlled the linear actuators and digital and analog I/O intraface. A block diagram of the sub-controller is shown in Fig. 5. The operating duration of ISiMI was estimated at four hours with lithium-polymer batteries of a 207Wh capacity, as shown in Table 4. The total weight of ISiMI in air is 20 kg, including an additional payload of 5 kg. The CCD camera and the frame grabber constitued a vision-guidance system. Fig. 7 is a block diagram of the vision-guidance system. The CCD camera transmitted the Consultative Committee on International Radio (CCIR) signal to the frame grabber. The frame grabber was a PC/104+ type and grabbed image frames at 10-15 Hz. Specifications for each are shown in Table 5 and Table 6, respectively. The image frames were processed on a Windows timer which was not deterministic. Because the image processing could take a lot of time, it was not possible to do it using a deterministic timer. Results of the image processing were stored in the shared memory. The real-time controller extracted and used the results from the shared memory.

Scuba Models
Fig. 4. Control system diagram of ISiMI.
Scuba Models
Fig. 5. Sub-controller.
Auv Magnetometer General Arrangement
Fig. 6. General arrangement of the AUV ISiMI system.
Scuba Diving
Fig. 7. Block diagram of the vision-guidance system.

Model

OceanSpy

Manufacturer

Tritech

Scanning

2:1 Interlace

Lens

3.6mm F2

Angular view in air

51o vertical 40o horizontal

Iris

Auto iris

Operating depth

6,000m water depth

Power

12-30V, 120mA

Dimension

10cm length, 3.4cm diameter

Table 5. Specifications of the CCD camera

Model

Matrox Meteor II+

Manufacturer

Matrox Imaging

Interface

PC/104+

Video source

NTSC, PAL, RS-170, CCIR

Channel

Up to 12 video inputs

Pixel format

RGB 8:8:8 or YU 4:2:2

Dimension

11.56cm length, 9.6cm width

Table 6. Specifications of the frame grabber 3.4 Communication system

A wireless local area network (LAN) was adopted as the communication system between ISiMI and a surface computer, which is used for offline communication for the mission allocation and data downloading. A wired LAN is additionally used as backup. A radio frequency (R/F) modem is installed for online communication between ISiMI and the surface computer for real-time data exchange. Generally, radio frequency cannot be used underwater because of the severe attenuation. We experimentally confirmed, however, that it is practical to transmit packets bi-directionally up to 3.5 meters deep in the OEB with an R/F modem with a bandwidth of 151.3 MHz and an output of 10 mW. With the R/F link, the user's commands and ISiMI's position are transmitted from the surface PC to ISiMI, and acknowledgments of reception are returned to the surface PC.

Table 6. Specifications of the frame grabber 3.4 Communication system

A wireless local area network (LAN) was adopted as the communication system between ISiMI and a surface computer, which is used for offline communication for the mission allocation and data downloading. A wired LAN is additionally used as backup. A radio frequency (R/F) modem is installed for online communication between ISiMI and the surface computer for real-time data exchange. Generally, radio frequency cannot be used underwater because of the severe attenuation. We experimentally confirmed, however, that it is practical to transmit packets bi-directionally up to 3.5 meters deep in the OEB with an R/F modem with a bandwidth of 151.3 MHz and an output of 10 mW. With the R/F link, the user's commands and ISiMI's position are transmitted from the surface PC to ISiMI, and acknowledgments of reception are returned to the surface PC.

Photoshop CS Mastery

Photoshop CS Mastery

Artists, photographers, graphic artists and designers. In fact anyone needing a top-notch solution for picture management and editing. Set Your Photographic Creativity Free. Master Adobe Photoshop Once and For All - Create Flawless, Dramatic Images Using The Tools The Professionals Choose. Get My Video Tutorials and Retain More Information About Adobe Photoshop.

Get My Free Videos


Post a comment