This operating handbook aims to guide users for DVL sensor installation and configuration in marine environments. This guide is intended for the integration of any DVL systems outputting Teledyne RDI PD0 or PD6 or Wayfinder message or Nortek message.

Use this document in complement of the Operating Handbook “Use in Marine Applications”.

Mechanical installation

DVL frame update

Since the release of the HPI firmware 5.2.1203, The SBG products now support DVLs with a NED or ENU frame convention.

The DVL must be rigidly fixed to the vessel structure.

It is recommended to align the DVL forward mark toward the vessel bow.

For a DVL with NED frame convention

The settings are straight forward, you just need to report the misalignment angles from vehicle reference frame


DVL1

The axis alignement is X-Forward, Y-Right (Z-Down) and alignment angle to enter in the inertial system configuration is Roll=0°, Pitch=0°, Yaw=0°.

For a DVL with ENU frame convention

DVL2

The axis alignement is X-Backward, Y-Right (Z-UP) and the alignment angle to enter in the inertial system configuration is Roll=0°, Pitch=0°, Yaw=-45°.

Electrical connections

The typical DVL electrical integration takes care of two main aspects:

  1. The DVL data output
  2. Synchronization between DVL and INS

Data output connection

Regarding the data output, a simple serial connection is generally used, by connecting the DVL serial port to one of the SBG INS available serial ports (eg. PORT A Rx), either in RS-232 or in RS-422.

Synchronization between DVL and SBG INS

DVL Master

In this mode of operation, the DVL runs on its own and can send a synchronization pulse to the SBG INS whenever a new velocity measurement is available.

The measurement rate might be not constant depending on water conditions.

To operate in this mode, the DVL synchronization output must be connected to one of the available SBG INS SYNC IN pins.

DVL Slave

In this mode of operation, the SBG INS generates a regular pulse signal to trigger each measurements of the DVL.

The measurement rate can be constant in this mode, driven by the SBG INS SYNC OUT rate.

However care must be taken in setting up the SYNC OUT Rate to mach the minimum DVL's timing requirement, based on DVL type, configuration, and maximum depth during the mission.

In other words, the DVL must be able to send a ultrasonic pulse, wait for the echo and process the data before the next trigger shall occur.

Setting the right rate

SBG Systems recommends you to contact your DVL's manufacturer to know what allowable SYNC OUT rates can be used depending on your system configuration and water environment.

As a rule of thumb, an update rate between 1Hz and 10Hz is feasible in shallow water conditions.

Software configuration

Aiding Assignment

Select the DVL on the input port of your choice (COM or ETH port) and the synchronization source used to time stamp DVL data.

DVL Aiding Assignment modified2

Aiding Settings

In Aiding tab we select the frames model, rough orientation, fine misalignment and lever arms, then finally the rejection of the DVL. (Auto rejection is recommended)

DVL settings modified

  1. Select the communication protocol : Teledyne for PD0 (binary) , Generic PD6 (ASCII) , Teledyne Wayfinder (binary) or Nortek (DF21/DF22) message format.

  2. Set the rough orientation axis and fine misalignment angles  of the DVL in the vehicle reference frame. (The orientation should be left to zero in DVL software to be entered here).
  3. Select the lever arm from the IMU to the DVL position in the vehicle reference frame (with X forward, Y to the right, and Z down).

  4. The Aiding rejection Automatic  is advised for both Bottom and Water, so the Kalman filter determines the confidence of this parameter by itself.

Input / Output

COM Ports

Configure the baudrate of the serial port you chose in the Aiding Assignment section. Also configure the mode (RS-232 or RS-422) for the relevant  serial port.

DVL IO modified

Logic I/O

Configure the synchronization input or output, making sure it matches the DVL polarity and timing requirements. Our example shows that we use the DVL in a slave mode and an update rate of 5Hz.

DVL event IO

Data Output

For data check, make sure you output the DVL Bottom Track and DVL Water Layer on “New Data” in the ETH 0 interface:

DVL data output modified

This is not mandatory for DVL use, but will allow to check the data received from the DVL in the sbgCenter.

It is also strongly recommended to use the “Support” output preset in the Data Logger section, and let it activated for the test run. This way logs can be replayed and data checked later in the sbgCenter or in a text file export.

Installation Overview

The whole configuration can easily be checked in the Setup Overview section. It features a 3D display that can be modified by simply clicking on an item, then changing the orientation or lever arm values. Any change will be directly visible.

Operation

Data check

You can also check the DVL data directly in the sbgCenter: Please note the velocities will be directly the ones from the DVL, so no orientation compensation will be applied (it is only applied internally by the Kalman filter).

In the following example, we got a velocity on the X and Y axes because the DVL was installed with a 45° angle.

HPI DVL Graphs

This requires that you output the DVL Bottom Track and DVL Water Layer in the Data Output section.

DVL Calibration

At each start, your INS will automatically calibrate and adjust your DVL installation parameters, as well as DVL's scale factor. This process can be performed in the following conditions:

  • Good GNSS reception: To Initialize and warm-up the INS and be used as a reference for DVL alignment and gain estimations.
  • Dynamic motion : DVL calibration parameters need some dynamic maneuvers to be "observed" and refined by the Kalman filter.

  A typical alignment pattern is shown in the next picture: