Controllability Analysis and Degraded Control for a Class of Hexacopters Subject to Rotor Failures

This paper considers the controllability analysis and fault tolerant control problem for a class of hexacopters. It is shown that the considered hexacopter is uncontrollable when one rotor fails, even though the hexacopter is over-actuated and its controllability matrix is row full rank. According to this, a fault tolerant control strategy is proposed to control a degraded system, where the yaw states of the considered hexacopter are ignored. Theoretical analysis indicates that the degraded system is controllable if and only if the maximum lift of each rotor is greater than a certain value. The simulation and experiment results on a prototype hexacopter show the feasibility of our controllability analysis and degraded control strategy.Comment: 21 pages, 7 figures, submitted to Journal of Intelligent & Robotic System

Evaluation and Stabilisation of an Embankment at Sebastopol, South Wales, UK

This paper introduces a slope movement and related railway track movement at Sebastopol, South Wales, UK. The monitoring results including slope movements and groundwater levels are summarised and presented. The slope at Sebastopol has a long history of instability. Because of continued gradual movement of the railway line and accelerated movement in 2004, a series of small diameter ‘Grundomat’ micro-piles were installed alongside the track early in 2005 to increase the shear resistance of the underlying soil and to reduce the rate of slope movement to a small but manageable amount. The slope movements have been continuously monitored since the piles were installed whilst the slope above the railway has continued creeping down-slope. In early 2007, the slope movement was accelerating and the railway itself was again involved in movements of about 20 mm per week. Given the increased movement of the bank it was considered likely that the Grundomat piles were either rotating or failing in bending. To gain further temporary stability, additional Grundomat piles were installed. Back-analyses of slope stability with and without the piles were carried out