Motion-compensated personnel-access system (PAS) and light crane.
The Neptune 20M system enables transfer of personnel or cargo from a vessel to a fixed offshore structure with full motion-compensation so that all wave-induced motions are removed and the payload arrives at the target structure with no relative movement between them.
Six degree of freedom (6DOF) Motion Platform.
A variant of the classic ‘Stewart Table’ or ‘Hexapod’ and is similar to those found in flight simulators. It is commercially available for use for third party work.
Ship-Based Robotic Arm for Autonomous Operations.
The Proteus Launch and Recovery System with integrated machine vision will enable Autonomous Surface Vessels (ASVs) to execute intervention tasks. It will also find applications on-board on manned vessels.
STL Research is a consultancy, design, development and ‘one-off’ project implementation group, specialising in the sub-sea and offshore industries.
You can find a PDF copy of the Neptune datasheet on our Downloads page.
Neptune 20M Personnel Access System
The Neptune system enables transfer of personnel with equipment or cargo, from a vessel via a gondola, to a fixed, or floating, offshore structure with full (6DoF) motion-compensation to remove wave-induced motions.
If the target is fixed and stationary, vessel induced motion is removed from the gondola, and it is said to be “space stabilised”. If the target is floating and also subject to wave action, the gondola and target motions are matched, and it is said to be “synchronised”.
PRINCIPLE:
A stand-alone system that can be installed on any suitable vessel and operates without requiring any vessel services or data, except for the optional use of ship-generated electrical power.
DESCRIPTION:
The system has five ‘joints’ and these are highlighted in Figure 1. The foundation, is fixed to the vessel deck and therefore moves with the vessel.
| Slew: | Rotates the entire Neptune system around the vertical axis. |
| Gimbal: | Keeps the arms in a vertical plane as the vessel rolls and pitches. |
| Shoulder: | Rotates the upper arm relative to the gimbal top frame. |
| Elbow: | Rotates the forearm relative to the upper arm. |
| Wrist: | Rotates the gondola relative to the forearm to keep the floor horizontal. |
MOTION MEASUREMENT:
When in space-stabilised mode, the vessel deck movement is measured in real time using an integral Position and Attitude Sensing System (PASS). This obtains position from Global Navigation Satellite System (GNSS) satellites using Real Time Kinematic (RTK) techniques to enhance precision. This position, along with data from an Inertial Navigation System (INS), is used to generate a PASS output that the Neptune controllers use to calculate joint angles to space-stabilise the gondola.
In synchronised mode (i.e. gondola motion matched with a moving target) a Remote Sensing System (RSS) measures the motion of the floating target. The Neptune controllers use RSS data to derive the joint angles needed to synchronise gondola and moving target motions.
OPERATING WINDOW:
Simulations (Figure 2), and sea trials (Figure 3) have proven Neptune capable of operating at Significant Wave Heights (Hs) up to 2m even on smaller vessels, for example on a 54m mono hull and a 36m catamaran.
SPECIFICATION:
| Height capability above deck: | 20.4m when on a standard mounting frame |
| Typical transfer height: | 17m above sea level |
| The operating height can be increased by mounting the unit on a pedestal. | |
| Reach from centre of slew axis: | greater than 21m |
| Vessel stand-off: | greater than 10m (typically 14 to 17m) |
| Slewing capability: | 295° (typically limited to 233º depending on installation) |
| Motion compensation accuracy: | Better than ± 10 cm |
| Maximum system individual motion compensation ability: | |
| Heave: | 5 m |
| Roll: | ± 10° |
| Pitch: | ± 10° |
| Yaw: | ± 147.5° |
| Sway: | ± 2 m Sway and Surge: in addition to |
| Surge: | ± 2 m a 3m diameter watch keeping circle |
| Weight | 11.3 t (excluding hydraulic power unit) |
| Foundation footprint | 2.5 m x 3 m |
| Hydraulic power unit | 2 x 120 kW (diesel or electric) |
| Gondola capacity | 3 people including PPE and tools |
| Payload in personnel mode | 300kg maximum |
| Payload in crane mode | 700kg maximum |
NOTES:
1. Motion compensation figures can be achieved with wave periods as short as 5 seconds.
2. Computer modelling, with ship-motion predictions, can be carried out to determine performance limits for a specific vessel if required.
PRINCIPAL DIMENSIONS:
Figure 4 shows a typical installation on a Fast Crew Transfer Vessel with an aluminium hull. The components shown in blue are the deck mounting frame and stowage cradle.
FEATURES:
SAFETY:
Design for safety is a key principle and is achieved in the following ways:
CERTIFICATION:
Designed to the requirements of DNV-ST-0358 Standard for Offshore Gangways and
DNV-ST-0378 Standard for Offshore and Platform Lifting Appliances.
Certification available to this or other equivalent classification society standards.
Conforms to HSE recommended ± 10 cm movement envelope.
OPERATING ENVELOPE:
In the future, Autonomous Surface Vessels (ASVs) will play an important role in servicing and repair of offshore installations for wind energy generation and hydrocarbon production. ASVs can operate around the clock in all but the most extreme weather conditions and, being unmanned, savings can be made by eliminating accommodation and equipment related to human safety. However, in order to carry out useful intervention tasks, ASVs need autonomous tools and manipulators.
STL are developing a ship-based multi-axis robotic arm with financial support from the Marine Challenge Fund (part of the ERDF’s European and Structural Funds Growth Programme 2014 – 2020) which was set up to boost marine innovation in Cornwall.
The arm, known as Proteus, will enable Autonomous Surface Vessels (ASVs) to execute intervention tasks – e.g. equipment transfers, survey and inspection, or launch and recovery operations. Space-stabilisation technology as used in STL’s Neptune personnel access system will be further developed to permit synchronous-stabilisation between two moving platforms, such as an ASV and another vessel, a floating wind-turbine, a wave-energy converter, or other target with wave-induced motion.
A stabilised robotic arm will also find applications on-board manned vessels. For example, launch and recovery of underwater ROVs and AUVs is labour-intensive and potentially hazardous to personnel and the equipment itself. A robotic arm could increase efficiency, safety, availability, and expand the weather window for operations.
Keep an eye on our NEWS page for updates.
In September 2019, Submarine Technology Limited (STL) and the Southwest Chapter of The Society for Underwater Technology (SUT) hosted a free workshop exploring the application of robotics in marine operations and their role as an enabling technology for manned and autonomous vessels.
Personnel from STL and the University of Plymouth presented results from the R&D programme together with naval architecture studies and market research findings. The application of robotics to marine operations and its role as an enabling technology for autonomous surface vessels was explored.
A pdf copy of the workshop agenda may be downloaded by clicking here.
The topics discussed at the workshop are listed below for reference. As part of our commitment to publish the results of our ASSP Project, we’ve made copies of the presentations available for download. To download, just click on the relevant topic title.
[Please note that most of the presentations are PowerPoint slide shows. To see all the information, including animations and graphics, it’s important that you ‘play’ the slide show rather than just viewing in edit mode]:-
| Topic | Speaker |
| Autonomous vessels and robotics | Neil Farrington (ORE Catapult) |
| Overview of the ship-based robotics R&D programme | David Kirkley (STL) |
| Test facilities for ship-based robotics | Peter Back (STL) |
| Robotic arm design | Mike Paton (STL) |
| Control System Design – Overview | Lewis Richards (STL) |
| Control System Design – Sensors | Peter Back (STL) |
| Naval Architecture Studies | Simon Hindley (SOLIS Marine Engineering Ltd) |
| Market Research | Paul Weston (Weston Marine Consultancy Ltd) |
| Autonomous systems | Philipp Thies (University of Exeter) |
| Autonomous marine applications | Alex Whatley (University of Plymouth) |
A 3D CAD model of the ASSP RDU may be downloaded by clicking on the image below. Due to file size restrictions, the model is a Solid Works Part file. However, if you’d like a copy of the full mated assembly, please contact us.
Presentations were made at the All-Energy 2019 conference in Glasgow during May and at the Seawork 2019 ASV Conference in Southampton during June. These were at a relatively early stage of the ASSP project and had the aim of alerting interested parties to the work. Copies of the presentations are available for download by clicking on the links below:-
| Event | Speaker |
| All-Energy 2019 Conference, Glasgow | David Kirkley (STL) |
| Seawork 2019 ASV Conference, Southampton | David Kirkley (STL) |
Please refer to the news page
STL’s six degree of freedom (6DOF) Motion Platform is a variant of the Stewart Table or Hexapod and is similar to those found in flight simulators.
It’s commercially available for hire. Please contact us here if you would like to know more.
The Motion Platform may be controlled using the following methods:
Submarine Technology Limited (STL) are committed to taking innovative technological concepts, developing them into a practical and economically viable state, and creating commercially successful ventures using the technologies.
Specialising in Motion Compensation, Control & Automation for maritime and offshore industries, STL is ideally placed to take innovative & cutting-edge sub-sea and offshore technology IP from its infancy, to eventual IPO or trade sale.
If you would like further information or are interested in our services, please contact us here.
STL are pleased to announce that initial, un-manned sea trials of the prototype Neptune motion-compensated personnel access system were successfully completed in March 2023. Sea Trials were carried out on …
As development of our Remote Sensing System (RSS) nears completion, we are pleased to share some of the details in a presentation titled ‘A Motion Compensated Robotic Arm for Use …
We have recently been awarded grant funding by Marine-i, the EU funded programme set up to boost marine innovation in Cornwall. The grant will help fund the development a Remote Sensing System …
