15 research outputs found
Distributed Coverage Hole Prevention for Visual Environmental Monitoring with Quadcopters via Nonsmooth Control Barrier Functions
This paper proposes a distributed coverage control strategy for quadcopters
equipped with downward-facing cameras that prevents the appearance of
unmonitored areas in between the quadcopters' fields of view (FOVs). We derive
a necessary and sufficient condition for eliminating any unsurveilled area that
may arise in between the FOVs among a trio of quadcopters by utilizing a power
diagram, i.e. a weighted Voronoi diagram defined by radii of FOVs. Because this
condition can be described as logically combined constraints, we leverage
nonsmooth control barrier functions (NCBFs) to prevent the appearance of
unmonitored areas among a team's FOV. We then investigate the symmetric
properties of the proposed NCBFs to develop a distributed algorithm. The
proposed algorithm can support the switching of the NCBFs caused by changes of
the quadcopters composing trios. The existence of the control input satisfying
NCBF conditions is analyzed by employing the characteristics of the power
diagram. The proposed framework is synthesized with a coverage control law that
maximizes the monitoring quality while reducing overlaps of FOVs. The proposed
method is demonstrated in simulation and experiment.Comment: 17 pages, 18 figures, submitted to the IEEE Transactions on Robotic
Laparoscopic Partial Cystectomy With Excision of Mesh Migration Into the Bladder Following Repair of Inguinal Hernia
Migration of hernia mesh into the bladder is a rare complication of inguinal hernioplasty. We present the case of an 85-year-old man who complained of hematuria and fever some 20 years after right hernioplasty. Cystoscopy and computed tomography revealed mesh migration into the right anterior wall of the bladder. Laparoscopic partial cystectomy with excision of the migrated mesh was performed successfully. To our knowledge, this is the first case of mesh migration into the bladder treated by laparoscopic partial cystectomy