UNDERWATER ROBOTS: MOTION AND FORCE CONTROL

OF VEHICLE–MANIPULATOR SYSTEMS, G. Antonelli,Springer-Verlag, Berlin, Germany, 2002. ISBN3-540-00054-2

Underwater robotics is a very interesting fieldof study, both for the economical impact thatthe development of efficient robotic tools mayhave on the off-shore industry and for thecomplex scientific and technological problemsit raises. This book addresses a key topic inthis area, namely the control of a robotwhose mechanical structure consists of a manip-ulator mounted on a 6-degrees-of-freedom(DOF) underwater vehicle. The main aspectsof this problem are separately illustrated andinvestigated and several nice contributions}stemming from the work of the author andof the research group he belongs to}to compre-hend it better and, ultimately, to designsatisfactory solutions are presented. Besidestheoretical analysis, a number of simulationsare performed and thoroughly discussed and,in order to clarify the physical behaviourof the system, experimental results aredescribed.In details, the first problem considered in the

book is that of constructing a model forthe underwater vehicle/manipulator system.Although the vehicle, the manipulator and theircoupling may be dealt with in a standardway, modelling of the whole system is quitedifficult, due to the necessity of taking intoaccount the presence of the hydrodynamic effectsof the surrounding fluid. The basic idea, here, isthat of simplifying the situation as muchas possible, by concentrating only on the phenom-ena which affects the dynamical properties ofinterest. Besides hydrodynamics effects, theauthor considers also the interaction with theenvironment due to contact between the manip-ulator’s end effector and an object, using a simplegeneral expression for the resulting reaction force.In this way, keeping also into account experi-mental and theoretical results presented in theliterature, the author obtain a satisfactory, work-able model of the underwater vehicle/manipulatorsystem.The kinematic control problem is then

studied. The system at issue is always redundant,due to the DOF provided by the vehicle,but different movements that give rise to thesame position and orientation of the end effectormay have greatly different costs in terms ofenergy and execution time. In general, it is

preferable to perform fast motion of smallamplitude by means of the manipulator,while the vehicle keeps its position, and to employthe vehicle’s mobility only for performingslow, gross motions. To handle this situation,the use of a redundancy resolution techniquethat allows to divide the global task intoa primary (sub)task and a secondary one,to be performed with different priorities, isproposed.. This approach is then enhanced bythe use of variable parameters (weights) that areadjusted by means of a fuzzy inference system.This allows to distribute the motion betweenvehicle and manipulator in accordance withspecific requirements.Dynamic control of the underwater vehicle/

manipulator system is then considered.After pointing out the particular features whichcharacterize this problem and differentiate itfrom similar ones, the related literature is brieflysurveyed and the discussion concentrateson a number of classical approaches. Slidingmode control, adaptive control and outputfeedback control schemes are described andanalysed from the point of view of stabilityand error dynamics. An interesting contributionis the application to the control problem atissue of a so-called virtual decomposition basedcontrol scheme. Adopting this approach, theserial chain structure of the underwater vehicle/manipulator system is exploited to reducethe complexity of the control problem and tofacilitate implementation. Then, the authordevelops an innovative adaptive/integral controllaw by designing part of the compensationaction in the inertial reference frame and part inthe vehicle-fixed reference frame. Externaldisturbances like ocean current and restoringforces can be handled easier in this way, facilitat-ing and improving convergence of the adaptationmechanism. Combination of the virtual decom-position based control scheme and of thisadaptive control law is quite reasonably claimedto be a viable way for improving performances inthe control of underwater vehicle/manipulatorsystems.Finally, the last part of the book is devoted

to study the problem of controlling interactionforces between the underwater vehicle/manipula-tor system and the environment. Control ap-proaches used in the case of industrial robots areshown to be in principle applicable for theunderwater vehicle/manipulator system, althoughthe inadequacy of present sensor and actuatortechnology for underwater application greatly

Copyright # 2004 John Wiley & Sons, Ltd. Int. J. Adapt. Control Signal Process. 2004; 18:599–604

BOOK REVIEWS 603

limits the possibility of obtaining satisfactoryresults.In conclusion, the book is very well organized

and it is written in a pleasantly concise style.Graduate students and researchers interested inrobotics and in control theory, besides specialistsof underwater robotics, will find it readable andrich of valuable material.

GIUSEPPE CONTE

Dipartimento di Ingegneria informatica, Gestionalee dell’Automazione,

Universita’ Politecnica delle Marchevia Brecce Bianche-Ancona 60131, Italy

E-mail: gconte@univpm.it

(DOI: 10.1002/acs.837)

Copyright # 2004 John Wiley & Sons, Ltd. Int. J. Adapt. Control Signal Process. 2004; 18:599–604

BOOK REVIEWS604