Wolfgang Zesch

Inertial drives for micro- and nanorobots: analytical study

The need for high precision robots dedicated to the assembly of microsystems has led to the design of new kinds of actuators able to reach very high positional accuracy over large distances. Among these, inertial sliders have received considerably interest in the last years. They have the advantage of being based on a simple principle that leads to a simple mechanical design. However, because they are based on the nonlinearity of friction, it is not easy to predict their stepsize repeatability. In order to understand the most important parameters affecting the precision of inertial drives, a theoretical study of a 1 degree of freedom inertial slider has been established. Analytical formulas describing the influence of different parameters, such as static and dynamic friction and mass distribution, have been developed. The effect of applied functions (sawtooth and parabolic), have also been studied. The theoretical cut off frequency has been found for each of the different waveforms, allowing us to predict the maximal and minimal working frequencies for the system. Thus, for each curve form, the repeatability of inertial sliders can be evaluated taking into account the uncertainties in the friction coefficients. The best suited waveforms for given constraints can therefore be selected. Simulations carried out from this have been successfully compared to experimental results.

Foldable magnetic wheeled climbing robot for the inspection of gas turbines and similar environments with very narrow access holes

Purpose – The purpose of this paper is to describe the design and prototype implementation of a miniature climbing robot with magnetic adhesion, developed for the inspection of gas turbines and other environments that require vertical mobility along curved steel surfaces, but only offer very narrow access holes – in the case of turbines only O15 mm.Design/methodology/approach – After a detailed description and analysis of the industrial environment where the robot is supposed to be used (inspection of gas turbines, housing not opened), the paper describes the basic mechanical concept which is based on two traction units on magnetic wheels and a folding mechanism which allows the robot for changing between two configurations – one for passing through the narrow access holes and one for climbing with 2D mobility on curved surfaces. A special focus is put on how the most difficult design challenges were solved – torque transmission at this very small size and the design of the folding mechanism.Findings – Th...

A modular inspection robot platform for power plant applications

This paper presents a novel approach for a modular robotic platform to support power plant inspection. In a first part the paper gives an overview over the challenges and benefits of robotic inspection on power generation equipment. The industry requirements are presented and discussed on a general level. The second part of the paper focus on the modular platform itself. The overall modular architecture is described and the various robotic modules with the various design features are presented and discussed. Based on the modular architecture a local navigation and control system is introduced providing the details on the architecture, the sensors used and the different algorithms implemented. At the example of a volumetric non destructive inspection of steam turbine rotor shafts and the inspection of electro static precipitators the variety of possible system configurations is presented. The paper closes with a brief discussion of the results achieved.

Automated boiler wall cleaning and inspection

Power plant boilers need to be cleaned and inspected on a regular basis. Boiler chambers can be up to 50m high requiring scaffolding for all works on the water walls. The scaffolding itself can take several weeks. To overcome the disadvantage of the time consuming scaffolding work an automated boiler wall crawler for wall cleaning and inspection is being developed by Alstom in collaboration with Alstom Inspection Robotics and Waterjet Technologies. The automated system will be able to drive up the water wall with the cleaning or inspection application integrated and no scaffolding will be required anymore. The cleaning application consists of a patented suspension cleaning technology where abrasive and water are mixed and pumped up to a defined pressure. The inspection will be done using latest ultrasonic technology to measure remaining wall thicknesses of the tubes. The deployment system consists of two magnetic track drives connected by a frame and two passive magnetic wheels. Laboratory tests have shown promising results. The system is able to drive up and down the water wall during the cleaning with the system running at around 100 bar.