Nylon fibre rope moorings for wave energy converters
The wave energy market has traditionally employed mooring concepts adopted from the mature technology of the oil and gas industry. However, this approach may not always be appropriate to satisfy the particular requirements of Wave Energy Converter (WEC) mooring systems, especially the need for very compliant moorings. Specific challenges are: the huge 1st order motion induced forces generated by storm waves in shallow water; the potential for slack-snap loading on a mooring; and, the fatigue performance of the mooring components. This paper describes the benefits of employing high compliance fibre rope in mooring systems of less than 100 m water depth. Nylon fibre ropes are a very attractive proposition because of their low modulus and cost but have previously been thought to have a poor wet fatigue performance. A specially designed long-lay-length Superline subrope has been tested both for compliance and for wet fatigue performance. The rope compliance is about twice that of parallel-subrope construction polyester rope. The fatigue performance is less than that of parallel-subrope polyester rope but is comparable to that of conventional construction polyester rope and to that of the chain and steel wire ropes which must also be used as mooring components. The high compliance of the nylon subrope construction together with the more than adequate fatigue performance demonstrated in this study qualify such nylon ropes as ideal for WEC mooring systems.
A novel mooring tether for highly dynamic offshore applications
Please note the following corrections to this text: 
 
Abstract, page 3, para 4: 72 kN should read 172 kN 
 
Page 134, Table 6.7: 74 should read 174, 72 should read 172
L1 Adaptive Controller for Attitude Control of Multirotors
In this work we show an application of L1 Adaptive control theory for attitude control of UAVs. We implement the flight control system on a multirotor to show robustness and precise attitude tracking in the presence of modeling uncertainties and environmental disturbances. We choose backstepping control architecture, since the kinematics and dynamics of multirotors in most cases can be written in strict feedback form. We further exploit the fact that the kinematics of the plant, while free of uncertainties, is nonlinear, which makes it highly suitable for dynamic inversion control at each level of backstepping. On the other hand, plant dynamics is uncertain and is affected by environmental disturbances such as wind gusts, unmodeled dynamics etc. Therefore, we consider 3 variants of the control architecture. The first method uses backstepping to determine the moment demand and augments it with the L1 adaptive controller to account for uncertainties and provide robustness with guaranteed transient performance. The second architecture apply the concept of L1 adaptive backstepping to the same problem; and the third architecture uses L1 backstepping for quaternion representation of the system dynamics, which helps to avoid the singularities associated with Euler angles.