MARKSMAN DP-INS DYNAMIC POSITIONING INERTIAL REFERENCE SYSTEM

Transcription

1 cc MARKSMAN DP-INS DYNAMIC POSITIONING INERTIAL REFERENCE SYSTEM Sonardyne s Marksman DP-INS is an advanced navigation-based Position Measuring Equipment (PME) source for dynamically positioned (DP) rigs. The independence and redundancy provided through inertial augmentation of Sonardyne s Marksman acoustic positioning system delivers improved performance and reliability whilst reducing operational cost. DP-INS combines the complementary characteristics of the latest Sonardyne Wideband 2 acoustic signal technology with high integrity inertial measurements. The resulting output is resilient to acoustic disruptions and completely independent from Global Navigation Satellite System (GNSS). Acoustically Aided INS The seamless integration of acoustics and inertial technologies combines the long term accuracy of acoustic positioning with the short term precision and fast update rate from high grade inertial sensors. A single navigation solution is computed and output to a display with intuitive status and quality metrics. Marksman DP-INS is the only system available that is proven offshore to work together with all DP systems including; GE, Kongsberg, MT, Navis, Rolls-Royce and Wärtsilä. The tightly integrated acoustic-inertial navigation provides accuracy, robustness and DP weighting that is comparable in performance to GNSS when operating with three or more transponders. The additional robustness offered by Marksman DP-INS, significantly reduces operational delays during periods of challenging subsea acoustic conditions such as aeration and noise. In addition, the high update rate and independence from GNSS will allow the vessel to continue operating in periods of GNSS instability or outage, for example due to scintillation. Marksman DP-INS does not need a full seabed Long BaseLine (LBL) array. For drilling operations, only three transponders are deployed below the vessel for each system, Marksman DP-INS at a glance Accuracy and DP weighting on a par with GNSS Tight coupling for added robustness Independence from GNSS disruptions Reduced transponder maintenance Reduced number of transponders without compromising robustness GyroUSBL to eliminate installation errors Integrates into existing Marksman console Proven offshore with GE, Kongsberg, MT, Navis, Rolls-Royce and Wärtsilä

2 MARKSMAN DP-INS DYNAMIC POSITIONING INERTIAL REFERENCE SYSTEM reducing the equipment inventory to be purchased and maintained, along with the set-up time. The need for only occasional acoustic aiding to the INS provides additional operational cost saving benefits by extending transponder life and reducing maintenance operations. Lodestar INS Lodestar, the core of DP-INS, uses the highest grade inertial sensors with proven reliability. System Configuration Lodestar Hardware Platform The core of the system is the Lodestar platform. Lodestar was released to the market in 2007 as a premium quality, survey grade Attitude and Heading Reference System (AHRS) for surface and subsea applications. Using the same hardware platform, Lodestar is now configured for tightly integrated, acoustically aided INS operations for DP applications. Lodestar makes use of three ring laser gyroscopes that measure the angular rate and three accelerometers that measure the specific force of a moving platform. The highest quality, field proven sensors have been selected for use due to their performance, high mean time between failure (MTBF) and ease of export (non ITAR). These sensors have highly stable error characteristics and are compensated for temperature variation, making them ideally suited to DP applications. The INS sensor outputs are combined mathematically to compute the position, velocity and attitude of the vessel. The output is extremely low noise and very accurate in the short term but slowly degrades over time. Therefore it is necessary to seamlessly aid the INS with complimentary acoustic positioning observations. Acoustic Tracking DP-INS removes the need to deploy a full seabed transponder array. This reduces set up time and saves operational costs. Acoustic Aiding Input Marksman DP-INS uses a tightly coupled integration of range and bearing measurements from at least three transponders to aid the INS and control integration drift. Tight coupling makes optimum use of Sonardyne Wideband acoustics to exploit and enhance the positive characteristics of the inertial sensors. This adds robustness, particularly in marginal acoustic conditions, as a full acoustic observation set is not continuously needed in order to aid the inertial navigation unit. Sonardyne s latest Sixth Generation (6G ) vessel-based transceivers and subsea transponders maximise the benefits of the system by providing the most precise and reliable acoustic aiding input. Whilst only one transponder is needed to aid navigation, two or three are typically deployed to optimise the robustness for drilling applications. Before the system is used operationally, the vessel s GNSS receiver is used to calibrate the real-world position of the transponders. Once this is complete, the system no longer requires GNSS as an input. Previous generation Sonardyne transceivers and transponders are also compatible with DP-INS. Bridge Installation The Lodestar INS and acoustic transceiver are interfaced to, and powered from, the Navigation Sensor Hub (NSH), which in turn is connected to a dedicated Navigation Computer running the Marksman software. DP-INS is fully integrated into the Marksman system so an additional workstation console is not needed. Independent DP Reference Sonardyne s acoustically aided DP-INS meets the need for a third independent DP vessel reference. The Navigation Computer is a powerful, purpose-built unit that has been specifically designed to run Sonardyne s family of acoustic and inertial navigation software applications. The operator interface can be fully integrated within DP consoles from all the leading manufacturers. Alternatively, a separate rack-mountable monitor and keyboard can be supplied. Dual-screen and touch-screen options are also available. The vessel s Marksman software displays both the vessel s LUSBL position and the INS position in an intuitive format alongside essential status information. The display gives the system operator access to all the information required to monitor DP-INS performance without significantly increasing their workload.

3 cc Wiring The Lodestar and USBL transceiver are connected through to the bridge where they interface to a Navigation Sensor Hub (NSH). The NSH provides power and serial communications via a junction box at the deployment pole or machine. For the Lodestar, 1x CAT6 or better is needed for INS communications and 1x copper pair used for power. For the LUSBL transceiver, a second CAT6 is used for acoustic transceiver communications and a second copper pair used for power. Connections to external sensors such as ships gyros, VRUs and GNSS are all on the bridge making installation easy with no routing of sensor data over long cable runs through the vessel. Transceiver and Lodestar Deployment In order to achieve optimum system performance, it is important that the inertial and acoustic systems experience the same dynamic motion. Therefore the Lodestar INS and vessel s acoustic transceiver should, wherever possible, be co-located on the same deployment pole using either a through-hull or through-tube arrangement. Vessel Position The INS sensor outputs are combined mathematically to compute the position, velocity and attitude of the vessel. Vessel Transceiver Sonardyne s latest HPT acoustic transceivers maximise the performance available from DP-INS by providing the most precise and reliable acoustic aiding input. Sonardyne s design of through-hull deployment machine has a rigid, one piece Inconel clad steel pole that hydraulically lowers and raises the transceiver through a gate valve. A sea chest with inspection hatch allows for ease of installation and cleaning of the transceiver. To allow the Marksman transceiver and INS sensor to be fitted to older vessels, Sonardyne also offers a through-tube method of deployment. As through-tube poles are less rigid than through-hull deployment poles, it is recommended that GyroUSBL is used, a unit which integrates a HPT acoustic transceiver and Lodestar INS in a single mechanical housing. GyroUSBL offers further operational savings as the unit can be pre-calibrated and delivered to the vessel ready to use. Unlike conventional acoustic transceivers, GyroUSBL doesn t need re-calibrating if it is removed and refitted for maintenance or even transferred to another vessel.

4 Dynamic Positioning System Lodestar Acoustically Aided INS AAINS IMU: Inertial Measurement Unit AINS: Aided INS INS: Inertial Navigation System Velocity Orientation v θ IMU Data Hz v, θ Position Acoustic INS Position Correction Kalman Filter (error state) Ultra Tight Integration Tight Integration Raw USBL Measurements: Phase (Bearing), Travel time (Range), SNR,... Loose Integration Acoustic Positioning System Acoustic Position System Architecture The figure above shows the system architecture of Sonardyne s acoustically aided DP-INS, including the different levels of integration. Orthogonal accelerometer and gyroscope triads within the IMU (Inertial Measurement Unit) measures change in velocity ( v) and orientation ( Θ). INS algorithms integrate the IMU data to output position, orientation and velocity. Aided INS (AINS) uses an error state Kalman filter to continuously estimate and correct INS error by processing measurements from external sensors here USBL. Loose, Tight and Ultra-Tight INS Integration (Left) Acoustic positioning, loose and tightly integrated INS in conditions of noise and aeration. A dotted red line in the vessel illustrations above indicates a failed acoustic measurement. System Performance (Left) INS positioning performance as compared to reference GNSS. 1DRMS ~0.2m. INS perfectly follows true vessel motion.

5 Marksman DP-INS System Performance The typical accuracy (excluding systematic error) of Sonardyne DP-INS when compared to other PMEs is shown in Table 1 below: Marksman DP-INS Key Technology System Accuracy (1DRMS) Update rate Marksman LUSBL 0.1m 0.5m 1 per 5 / 6 seconds DP-INS 1 transponder)* % depth 1 to 5Hz DP-INS (at least 3 transponders) 0.1m 0.2m 1 to 5 Hz DGNSS 0.1m 0.5m 1Hz * Single transponder aiding. Actual performance is system and environment dependent. Marksman DP INS Equipment List Key: = Required 6G Sonardyne s sixth generation (6G ) technology platform provides robust performance, ease of use, greater functionality, equipment flexibility and compatibility with aided inertial technologies. Its features reduce operational risk, deliver more efficient operations and lower the cost of ownership. Software Marksman DP-INS Type 8026 Navigation Computer Additional Requirements Type 8098 Navigation Sensor Hub Type 8024 Lodestar Subsea Acoustically Aided INS Seamlessly integrates Sonardyne LBL, USBL and Lodestar INS technologies to offer a combined acoustic and inertial navigation solution suitable for the most demanding subsea tracking and vessel positioning applications. Marksman LUSBL System Marksman LUSBL Wideband 2 Sonardyne Wideband 2 is an ultra-wide bandwidth signal architecture exclusively developed for 6G hardware. Delivering seamless acoustic navigation and telemetry of subsea data, the technology offers a host of benefits; fast and robust transmission of data, precise ranging, wide area coverage, mitigation from multipath signals and greater immunity to noise from vessels and other acoustic systems. Other Drilling Systems from Sonardyne Marksman LUSBL Marksman MRAMS Emergency BOP Controller Downhole Data Logger Riser Profiling System Dynamic Positioning From deep water drilling rigs to construction support vessels, Sonardyne Wideband positioning systems are optimised to provide Dynamic Positioning systems with accurate and repeatable position referencing. Compatible with all leading makes of DP with options for system redundancy and inertial aiding.

6 Global Headquarters T. +44 (0) F. +44 (0) Aberdeen, UK T. +44 (0) F. +44 (0) Houston, USA T F Singapore T F Rio das Ostras, Brasil T F Sonardyne International Limited All rights reserved. 08/2015