Instrumented Tool based Robot Programming - Parameterization of Screwing Process Macros

Abstract

Programming by Demonstration (PbD), is a powerful mechanism for reducing the complexity of search space for learning. Current approaches for skill representation can be broadly divided between two trends. Low-level representations of skills, taking into account the form of a non-linear mapping between sensory and motor information, which is referred to as “trajectories encoding”. On the other hand high-level representations of skills that decompose them in a sequence of action-perception units which is referred to as “symbolic encoding” [1]. While for symbolic encoding visual perception of states and actions is one preferred approach trajectories usually are acquired from direct demonstration by hand guidance of robot arms carrying robotic tools by skilled workers. This approach requires both the process knowledge of the experienced worker and the possibility of intuitive hand guidance of the robotic tool which is negatively affected by the robots limited working space, friction or the reachability of the robot. Therefore and because it is also highly unintuitive to parameterize macro based robot programs with numerical values considering process parameters (like required forces or position parameters) we propose to let the worker use ordinary power tools during demonstration which are instrumented with additional sensors in order to be able to measure relevant parameters, so called “instrumented tools”. The paper presents the concept for a robotic workstation to be programmed by demonstration with an instrumented tool, the components of the instrumented tool as well as relevant calibration steps and results from application of the technology to an automotive preassembly process..