第11页 英语原文：Adhesion Control for the Alicia3 Climbing RobotD. Longo and G. MuscatoDipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, Universita degliStudi di Catania, viale A. Doria 6, 95125 Catania ItalyAbstract. Climbing robots are useful devices that can be adopted in a variety ofapplications like maintenance, building, inspection and safety in the process andconstruction industries. The main target of the Alicia3 robot is to inspect non porous vertical wall with any regard for the material of the wall. To meet this target, a pneumatic-like adhesion for the system has been selected. Also the system can move over the surface with a suitable velocity by means of two DC motors and overcomesome obstacle thanks to a special cup sealing. This adhesion technology requires a suitable controller to improve system reliability. This is because small obstacles passing under the cup and wall irregularitycan vary the value of the internal pressure of the cup putting the robot in some anomalous working conditions. The methodologies used for deriving an accuratesystem model and controller will be explained and some result will be presented inthis work.1 Introduction Climbing robots can be used to inspect vertical walls to search for potential damage or problems on external or internal surface of aboveground/underground etrochemical storage tanks, concrete walls and metallic structures14. By using this system as carrier, it will be possible to conduct anumber of NDI over the wall by carrying suitable instrumentation 5, 6.The main application of the proposed system is the automatic inspectionof the external surface of aboveground petrochemical storage tanks where it is very important to perform periodic inspections (rate of corrosion, risk of air or water pollution) at different rates, as standardized by the AmericanPetroleum Institute 7. The system can be also adopted to inspect concrete dams. While these kinds of inspections are important to prevent ecologicaldisasters and risks for the people working around the plant, these are veryexpensive because scaffolding is often required and can be very dangerous Fig. 1. Typical operating environment and the Alicia3 robotfor technicians that have to perform these inspections. Moreover, for safetyreasons, plant operations must be stopped and the tank must be emptied,cleaned and ventilated when human operators are conducting inspections. InFig. 1(a) and 1(b) typical environments for climbing robots are shown. Figure1c shows the Alicia3 robot prototype while attached to a concrete wall duringa system test.2 System Description The Alicia II system (the basic module for the Alicia3 system) is mainlycomposed by a cup, an aspirator, two actuated wheels that use two DC motorswith encoders and gearboxes and four passive steel balls with clearance toguarantee plain contact of the cup to the wall. The cup can slide over a wallby means of a special sealing that allows maintaining a suitable vacuum insidethe cup and at the same time creating the right amount of friction with respectsystem weight and a range of a target wall kind. The structure of the Alicia II module, shown in Fig. 2, currently comprisesthree concentric PVC rings held together by an aluminums disc. The biggerring and the aluminums disc have a diameter of 30 cm. The sealing system isallocated in the first two external rings. Both the two rings and the sealing are Fig. 2. Structure of the Alicia II moduledesigned to be easily replaceable, as they wear off while the robot is running.Moreover the sealing allows the robot passing over small obstacles (about 1 cmheight) like screws or welding traces. The third ring (the smallest one) is usedas a base for a cylinder in which a centrifugal air aspirator and its electricalmotor are mounted. The aspirator is used to depressurize the cup formed bythe rings and the sealing, so the whole robot can adhere to the wall like astandard suction cup. The motor/aspirator set is very robust and is capable of working in harshenvironments. The total weight of the module is 4 Kg. The Alicia3 robot is made with the three modules linked together by meansof two rods and a special rotational joint. By using two pneumatic pistons it ispossible to rise and to lower each module to overcome obstacles. Each modulecan be raised 15 cm with respect to the wall, so obstacles that are 1012 cmheight, can be easily overcame. The system is designed to be able to stayattached using only two cups while the third, any of the three, is raised up.The total weight of the system is about 20 Kg.3 Electro-Pneumatic System Model By using this kind of movement and sealing method, it is possible, due tounexpected small obstacles on the surface, to have some air leakage in thecup. This leakage can cause the internal negative pressure