Michael Schulze

Programming abstractions and middleware for building control systems as networks of smart sensors and actuators

Developing complex sensor/actuator systems, like robot applications, is challenged by a multitude of different hardware platforms, networks, programming languages, data formats, etc. In this paper, we present our architecture that copes with this heterogeneity and allows for a flexible composition of smart sensors and actuators. The main focus lies on a two layered approach combining the communication middleware FAMOUSO and the programming abstraction MOSAIC. FAMOUSO enables the information exchange between networked systems, hides the high degree of heterogeneity on hardware and network level, and is usable from different programming environments. MOSAIC uses FAMOUSO and provides a generic access to the exchanged information. Furthermore, it offers a way to abstract from different sensor and actuator hardware and provides a framework for application development with predefined components, enabling comprehensive fault detection. The paper concludes with a case study that shows how the middleware and programming abstractions are used to build a distributed modular system for a robot manipulator.

Exploiting publish/subscribe communication in wireless mesh networks for industrial scenarios

This paper addresses questions of using wireless mesh networks (WMNs) in heterogeneous industrial infrastructures. This implies several problems like global addressing, handling of QoS requirements, interconnection with embedded networks. Our proposed solution is a publish/subscribe middleware. We discuss how it solves the mentioned problems. Real-world measurements and simulation results give an idea of QoS properties. A case study of controlling a mobile robot is presented. The results show that the middleware is well suited for non-critical control and monitoring tasks.

Exploiting the FAMOUSO middleware in multi-robot application development with Matlab/Simulink

We describe a framework for the development of distributed systems combining real and virtual components, sensors and actuators. We show the benefits of our approach for the development and validation of multi robot applications. Based on our middleware, which provides a flexible communication for distributed systems, virtual and real components are seamlessly exchangeable during different development steps. This modularity and compatibility allows appropriate adjustments for design, rapid prototyping and examination as soon as an opportunity to reduce the hardware effort for large scenarios.

Visualization of robot's awareness and perception

Today, direct interaction between humans and robots is limited, although the combination of human flexibility and robots power enables a growing productivity. The problem for humans lies in the nearly unpredictable behavior and motion of the robot itself. However, we can enhance humans view with more information to get knowledge about robots perception and awareness. We use Augmented Reality methods for providing the information in an adaptable visualization for different user types. We show that our approach leads to shorter development cycles as well as to safer human-robot interaction.

Sentient Objects for Designing and Controlling Service Robots

Abstract Services related to healthcare and the support for elderly people become more and more important. Autonomous or semi-autonomous robots may play an important role in this area. From a control system point of view these robots are networks of distributed smart components to perceive their environment and react on it in real time. The problem of developing or extending such a robot often is that the designer has to start from scratch struggling with low level issues, where reusability of already designed components would be highly desirable. The paper describes a robot application in the area of a meals distribution service that combines two design worlds. One is the conventional world of modelling the functional properties without any structural considerations, the other is the world of cooperating sentient objects. We explain how the notion of sentient objects will assist the design, simulation and also later extensions and adaptations of the robot.

MLCCA — Multi-Level Composability Check Architecture for dependable communication over heterogeneous networks

During the design of complex networked systems, it is cruical to ensure the composability of the deployed applications and network protocols. Special care has to be taken to provide non-functional requirements like bandwidth and latency. Existing solutions only tackle this problem during the design phase; later refactoring or added components are not covered, potentially causing QoS violations. We propose MLCCA, a multi-level architecture which complements the design-time composability checks with additional automatic checks performed at compiletime and at run-time. The required infrastructure is embedded into our communication middleware FAMOUSO, making it transparent to application developers. The architecture has been evaluated in a tele-operated mobile robot case study. If the QoS attributes could not be fulfilled due to refactoring or changed conditions, no communication was allowed by the middleware, ensuring that the application could enter a fail-safe state. No data was sent over insufficient channels. Thus, our combination of FAMOUSO and MLCCA enables the sustainable deployment of complex networked systems.

Latency analysis for the cooperation of event and time-triggered networks

The paper describes the analysis of cross network latencies occurring when federating an asynchronous, event-triggered CAN-bus and a synchronous time-triggered TTP/C network. The connection of networks is motivated by both cost-efficiency trade-offs in various network types and reasons of isolating highly critical from less critical communication. The intrinsic latencies incurred when crossing network boundaries are evaluated under various conditions - either in some form of synchronisation with a global time or in completely unsynchronised networks. The results from the formal analysis are compared to experimental results obtained in a mobile robot where the critical reactive control components are connected by a TTP/C network while additional sensor information improving the quality of control is obtained via a CAN-bus.

Reliable fault-tolerant sensors for distributed systems

Providing reliable fault-tolerant sensors is a challenge for distributed systems. The demonstration setup combines three sensors and allows to inject different faults that are reliably detected by our system.

AFP - an Adaptive Fragmentation Protocol Supporting Large Datagram Transmissions

Transferring datagrams is essential for a lot of tasks. If the data does not fit into one network packet,fragmentation is needed. We propose a fragmentation protocol that adapts to different MTUs and to the datagram size, ensuring efficient bandwidth utilization. The protocol is extensible to allow tailoring to network and application demands. Thus, it is suitable for deploying it in various scenarios and under different conditions, whereas other protocols do not scale well. We demonstrate the applicability on low-end embedded devices and in a tele-operated robot scenario. Additionally, we analyze the scalability of our protocol, evaluate the induced overhead for different MTUs and datagram sizes, and compare it to other fragmentation protocols.

Identifying patients and visualize their vitality data through augmented reality

Hospitals aim at an extensive continuous monitoring of patients. This enables the personal to check the conditions of a patient anywhere at any given time and allows them to immediately react to anomalies and emergencies. The same technology can be used to instantaneously visualize available patient data using augmented reality techniques.