An industrial robot as carrier of a laser profile scanner : motion control, data capturing and path planning

University dissertation from Örebro : Örebro universitet

Abstract: Geometric Reverse Engineering (RE) is concerned with the problem of creating CAD-models of real objects by measuring point data from their surfaces. In the aim of creating a fully automatic RE system there is a need to automate also the measuring process. The work presented in this thesis deals with issues concerning the use of an industrial robot and a laser profile scanner as a platform to achieve this.The initial work presented mainly threats the hardware and software components used and the efforts needed to integrate them into a working system. The components used are basically an industrial robot with attached turntable, a laser scanner and a programable CAD-system (computer aided design). Worth to mention is the approach to use the robot also as a measuring device. This work also describes the project’s long term objective - a fully automatic system for Geometric Reverse Engineering of unknown objects.The second study is concerned with motion control and data capturing. Motion control is here understood as the process of realizing a robot driven scanner movement along a path defined by 3D curves in a CAD-system. Issues such as avoiding collisions, finding suitable robot configurations and data transfer are treated. The data capture section of the work deals with the problem of merging the measured data from the two systems. During the datacapture the robot and the scanner work separately with their own sampling intervals. The data merging procedure involves a technique based on timestamps and interpolation.The third study deals with the problem of automatic path planning for a system that can move along curved paths. The system works without knowing the shape of the object to examine in advance. It is therefore suited to fulfil the requirements as the core part of the automatic RE-system we have in mind. With this abilitycomes the problems of planning upcoming scan operations in a way that will likely cover as much new, unseen surface as possible, but still plan and perform smoothly shaped scanner movements. A concluding paper treats the different sources of errors that will affect the measuring quality in terms of absolute accuracy.

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