On Design and Control of a Mobile Robot System for Sewerage NetworkMaintenance

The paper sketches KURT, an autonomous robot platform prototype that is able to navigate inside a network of sewage pipes. KURT is a six-wheeled device; it has modular, layered hardware and control architectures. Its sensor connguration consists mostly of stationary and one exible ultrasound sensors and of two inclinometers. In experiments run in a test sewerage system consisting of concrete pipes of 600 mm diameter, it has proven to be able to travel safely through straight pipes, to recognize diierent types of pipe crossings, to turn at crossings, and to navigate from a given start point to arbitrary speciied goal points. 1 Background The public sewerage system in Germany is about 360,000km long, and it is in no good condition (Ke-ding et al., 1990): sewage may leak out, possibly polluting soil and ground water, and it may wash away soil, possibly eroding the foundations of buildings or the underground of streets and pavements. Consequently, considerable eeort must be taken to maintain the sewage pipes, which includes inspection and local repair. However, the sewerage system is no easy place for robots to work. It is narrow, slippery, dirty, and wet. It consists of pipes from diierent materials, where concrete, PVC, and ceramic are the most frequently used. It may include obstacles or damages like sediments , cracks, holes, non-expertly built junctions from smaller pipes, or roots grown into the pipes through cracks or leaking joints. The work we report here was part of the feasibility study LAOKOON 1 whose purpose it was to investigate the feasibility and the prospects of autonomous robots for sewer maintenance. Within 1 The name LAOKOON is an acronym for the German wording of \learning, autonomous, cooperating sewer ro-bots". Figure 1: A schematic representation of the LAOKOON-net. See text for explanations. the overall study, the aim of our work was to build a prototype sewer robot platform that is able to physically navigate through the LAOKOON test sewerage network, or brieey, LAOKOON-net. This test network was built by rhenag and is installed above ground at the GMD site. Figure 1 shows the layout. The task to navigate through the LAOKOON-net is certainly somewhat easier than navigating through an operational sewerage network: The pipes are dry and relatively clean, they are made from a single type of material, and the layout is known with certainty. However, we suspected (and in re