Markus Klotzbücher

Bayesian time-series models for continuous fault detection and recognition in industrial robotic tasks

This paper presents the application of a Bayesian nonparametric time-series model to process monitoring and fault classification for industrial robotic tasks. By means of an alignment task performed with a real robot, we show how the proposed approach allows to learn a set of sensor signature models encoding the spatial and temporal correlations among wrench measurements recorded during a number of successful task executions. Using these models, it is possible to detect continuously and on-line deviations from the expected sensor readings. Separate models are learned for a set of possible error scenarios involving a human modifying the workspace configuration. These non-nominal task executions are correctly detected and classified with an on-line algorithm, which opens the possibility for the development of error-specific recovery strategies. Our work is complementary to previous approaches in robotics, where process monitors based on probabilistic models, but limited to contact events, were developed for control purposes. Instead, in this paper we focus on capturing dynamic models of sensor signatures throughout the whole task, therefore allowing continuous monitoring and extending the system ability to interpret and react to errors.

Reusable hybrid force-velocity controlled motion specifications with executable Domain Specific Languages

Most of todays robotic task descriptions are designed for a single software and hardware platform and thus can not be reused without modifications. This work follows the meta-model approach of Model Driven Engineering (MDE) to introduce the concepts of Domain Specific Languages (DSL) and of Model Transformations to the domain of hybrid force-velocity controlled robot tasks, as expressed in (i) the Task Frame formalism (TFF), and (ii) a Statechart model representing the discrete coordination between TFF tasks. The result is a representation in MDEs M0, M1, M2 and M3 form, with increasingly robot and software independent representations, that do remain instantaneously executable, except obviously for the M3 metametamodel. The Platform Specific Model information can be added in three steps: (i) the type of the hybrid force-velocity controlled task, (ii) the hardware properties of the robot, tool and sensor, and (iii) the software properties of the applied execution framework. We demonstrate the presented approach by means of an alignment task executed on a Willow Garage PR2 and a KUKA Light Weight Robot (LWR) arm.

A Lightweight, Composable Metamodelling Language for Specification and Validation of Internal Domain Specific Languages

This work describes a declarative and lightweight metamodelling framework called uMF for modelling and validating structural constraints on programming language data-structures. By depending solely on the Lua language, uMF is embeddable even in very constrained embedded systems. That way, models can be instantiated and checked close to or even within the final run-time environment, thus permitting validation to take the current state of the system into account. In contrast to classical metamodelling languages such as ECore, uMF supports open world models that are only partially constrained. We illustrate the use of uMF with a real-world example of a robot control formalism and compare it with a previously hand-written implementation. The results indicate that strict formalization was facilitated while flexibility and readability of the constraints were improved.

Service Component Architectures in Robotics: The SCA-Orocos Integration

Recent robotics studies are investigating how robots can exploit the World Wide Web in order to offer their functionality and retrieve information that is useful for completing their tasks. This new trend requires the ability of integrating robotics and information systems technology. On the first side a set of robotics component based frameworks, which are typically data flow oriented, have been developed throughout the last years and Orocos is one of the most mature. On the other side the state of the art is represented by the Service Oriented Architecture, where the Service Component Architecture defines a component-based implementation of this approach.

Service component architecture in robotics: the SCA-Orocos integration

Recent robotics studies are investigating how robots can exploit the World Wide Web in order to offer their functionality and retrieve information that is useful for completing their tasks. This new trend requires the ability of integrating robotics and information systems technology. On the first side a set of robotics component based frameworks, which are typically data flow oriented, have been developed throughout the last years and Orocos is one of the most mature. On the other side the state of the art is represented by the Service Oriented Architecture, where the Service Component Architecture defines a component-based implementation of this approach.