Community Research and Development Information Service - CORDIS


HEXATERRA Report Summary

Project ID: 605420
Funded under: FP7-SME
Country: Greece

Final Report Summary - HEXATERRA (The development of a modular ‘stepping locomotion’ system for installation on subsea trenching machines used for subsea energy cable burial)

Executive Summary:
Offshore wind and tidal energy generation is becoming an increasingly important component of the world’s energy mix with Europe at the forefront of this technological revolution. Continued strong growth is predicted.

However, a growing problem is manifesting itself within the industry. The submarine cables that are an essential infrastructural component of offshore energy now account for 80% of insurance claims related offshore renewables. Unfortunately, current practice is to simply lay these cables on top of the seabed without burial or protection, as the traditional tracked trenching machines originally developed for deep sea oil and gas applications are inadequate for the harsh coastal terrain. Cables are therefore exposed to numerous risks such as tidal forces, rock abrasion, snagging from fishing nets etc. Furthermore, unburied HV cables present serious environmental concerns related to local habitat & water temperature.

Existing technologies cannot address this growing problem. HexaTerra will develop a novel solution to the problem that builds upon recent advances made in ‘stepping’ locomotion systems for traversing undulated harsh terrain. This system will provide a robust solution for its environment, by achieving the following objectives:

Project Context and Objectives:
The HexaTerra system is a modular ‘bolt-on’ locomotion system for existing underwater heavy equipment trenching machines. HexaTerra enables the trenching machine to move in all directions; to turn on the spot, forwards and backwards, sideways and diagonally, an important requirement for this application especially around the wind turbine foundations.

HexaTerra overcomes the limitations that have prevented tracked trenching equipment from negotiating and traversing the harsh and rocky terrain where wind turbines are typically sited. New and existing cables, which would otherwise lie unprotected for years, can now be buried safely

- Modular design suited to existing trenching machines
- Mechanical movement subsystem with <5% error in motion tracking & <1cm in actual tracking
- Control subsystem capable of negotiating +/-0.5m 90° step in terrain & turn on-the-spot
- Complete simulated locomotion cycle in under 5mins, with <5% desired motion tracking error

Using this solution the project expects to comprehensively address the problem of damage to subsea energy cables, thereby maximising offshore energy reliability, maintain renewable energy affordability, & minimise the marine environmental impact of cables. In turn, we will deliver a profit of €10.95m & 100 new high skill jobs to the SME partners after 5 years.

Project Results:
The innovations generated by the HexaTerra project include:

- Mechanically actuated ‘legged’ locomotion hardware, which remains stable under the influence of a number of disturbances, exhibits the desired manoeuvrability, avoids interference between the trenching process and its own motion, and is as efficient as possible.
- Locomotion control firmware and hardware, achieving a dynamic positioning (of each leg and the main body) and orientation (of the main body) to counterbalance sea wave, tidal current and seabed trench cutting induced forces and moments, as well as modelling uncertainties.
- Visual and haptic user machine interface provides a readily digestible and ‘non-confusing’ user interface; the ergonomics of the visual interface design accommodate the presentation of key data from the SONAR and visible light images overlaid on one display to provide a detailed image and reference frame. Haptic feedback is used to provide the user with the feeling lost in the control of remote equipment.
- Sensor fusion is intrinsically linked to all of the HexaTerra innovative components. This technology is based upon Magnetic, Angular Rate and Gravity (MARG) sensors, in using several types of sensors and a Kalman filter, the characteristics of one type of sensor helps to overcome the limitation of the other sensors.

Potential Impact:
The HexaTerra is a modular ‘bolt-on’ locomotion system for existing underwater heavy equipment trenching machines machine to move in all directions; to turn on the spot, forwards and backwards, sideways and diagonally, an important requirement for this application especially around the wind turbine foundations. The system adapts automatically to the terrain to keep the trench ‘cutting tool’ dynamically stable at all times. Responding to sensor input, the machine distributes its weight evenly over the ground and finds a base of support for each of the six legs, resulting in incredible stability and optimal weight distribution. Depending on the irregularity of the ground, the machine operator can adjust both the ground clearance of the machine and the height of each step. It has exact step positioning and spot contact with the ground, with the ability to step over obstacles.

By addressing the issues that have thus far prevented the burial of subsea HV cables which are used to transfer electrical power from the offshore energy transformers back to the inland substation, we expect to achieve the following aims:

- Address the emerging threat of failure to HV cables caused by tides, nets and anchor damage.
- Help maximise the reliability of renewable energy networks by preventing failures to unburied cables.
- Maintain affordability in the price to the consumer of renewable energy. This will be achieved through the removal of unnecessary substantial insurance and repair costs related to unburied cable failures.
- Greatly minimise the environmental impact of HV cables on subsea habitat and water temperature.
- Create 100 new, and safeguard existing jobs for heavy engineering manufacturers, and their supply chains, through the introduction of an effective and innovative new system into an emerging and rapidly growing market.
- Generate exploitable IPR and a competitive advantage for the SMEs involved in this project.

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Panagiotis Chatzakos, (Managing Director)
Tel.: +30 6977467158
Record Number: 192472 / Last updated on: 2016-12-13