Jonas Neander

Asymmetric multihop communication in large sensor networks

With the growing interest in wireless sensor networks, energy efficient communication infrastructures for such networks are becoming increasingly important. In this paper, we compare and simulate asymmetric and symmetric communication in sensor networks. We do this by extending LEACH, a well-known TDMA cluster-based sensor network architecture, to use asymmetric communication. The extension makes it possible to scale up the network size beyond what is feasible with LEACH and its variants LEACH-C and LEACH-F.

Efficient Integration of Secure and Safety Critical Industrial Wireless Sensor Networks

Wireless communication has gained more interest in industrial automation due to flexibility, mobility, and cost reduction. Wireless systems, in general, require additional and different engineering and maintenance tasks, for example cryptographic key management. This is an important aspect that needs to be addressed before wireless systems can be deployed and maintained efficiently in the industry.In this paper, we take an holistic approach that addresses safety and security regardless of the underlying media. In our proposed framework we introduce security modules which can be retrofitted to provide end-to-end integrity and authentication measures by utilizing the black channel concept. With the proposed approach, we can extend and provide end-to-end security as well as functional safety using existing automation equipment and standards, such as Profisafe, Profinet IO, and WirelessHART. Furthermore, we improve the WirelessHART standard with periodic and deterministic downlink transmissions to enable efficient usage of wireless actuators, as well as improving the performance of functional safety protocols.

Experimental study of UWB-based high precision localization for industrial applications

Recent developments in wireless sensor networks have inspired applications which require high accuracy localization. Impulse radio ultra wide-band technology has a fine time resolution, allowing accurate determination of the time of arrival at the receiver, making it a serious contender for accurate ranging, in comparison to narrow-band technologies. In this paper, we present a UWB based 3D real-time indoor positioning system with 802.15.4a compliant wireless nodes. Results from measurement campaigns reveal that for line-of-sight (LOS) scenarios 11 cm accuracy and 2 cm precision without any postprocessing (i.e. filtering) are possible, hence demonstrating the capability of accurate UWB-based localization using trilateration, resulting in a fast and non-complex algorithm that provides high precision positioning. The proposed system presents an initial step in developing a high precision system for localization in industrial applications.

Prolonging wireless HART network lifetime using packet aggregation

Wireless sensor networks are becoming more and more adopted into industrial plants and Wireless HART is the first wireless sensor network standard to emerge, which specifically is designed to support the specific requirements posed by the industry. Automation industry requires wireless sensor network devices to have a very long lifetime, often up to 5 – 10 years without a battery change. This puts requirements on how the wireless sensor network technology should be designed to minimize energy consumption while still fulfilling the application requirements. Packet aggregation is an essential technique in mission critical wireless sensor networks for achieving effective transmission and hence better power conservation. In this article we propose a flexible packet aggregation scheme for Wireless HART which reduces energy consumption of each device. The proposed scheme only requires a minor change to the Wireless HART standard but still preserves the end-to-end security and retains backward compatibility with non aggregating devices. We show by calculations that our proposed packet aggregation solution reduces energy consumption for a network by up to 50%, which will result in a significant increase in lifetime of Wireless HART devices.

Introducing Temporal Analyzability Late in the Lifecycle of Complex Real-Time Systems

Many industrial real-time systems have evolved over a long period of time and were initially so simple that it was possible to predict consequences of adding new functionality by common sense. However, as the system evolves the possibility to predict the consequences of changes become more and more difficult unless models and analysis method can be used. In this paper we describe our approach to re-introducing analyzability into a complex real-time control system at ABB Robotics. The system consists of about 2 500 000 lines of code. Traditional real-time models and analyses, e.g. fixed priority analysis, were not applicable on this large and complex real-time system since the models are too simple for describing the systems behavior accurately, and the analyses are too pessimistic. The proposed method is based on analytical models and discrete-event based simulation of the system behavior based on these models. The models describe execution times as statistical distributions which are measured and calculated in the existing system. Simulation will not only enable models with statistical execution times, but also correctness criterion other than meeting deadlines, e.g. non-empty communication queues. Having accurate system models enable analysis of the impact on the temporal behavior of, e.g. customizing or maintaining the software. The case study presented in the paper shows the feasibility of the method. The method presented is applicable to a large class of complex real-time systems.

Deterministic downlink transmission in WirelessHART networks enabling wireless control applications

Wireless sensor and actuator networks bring many benefits to industrial automation systems. However, unreliable wireless and multihop communications among sensors and actuators cause challenges in designing such systems. Wireless HART is the first standard for wireless real-time industrial applications. However, current Wireless HART standard does not provide services for efficient usage of actuators, which are an essential part of automation. In this paper we focus on Wireless HART and propose a periodic and deterministic downlink transmission functionality which enables efficient usage of actuators and control applications. Furthermore, we define new HART commands extending the interface, without affecting available services, to support the integration of actuators. This can be achieved with minor changes in the current standard.

Integration of WirelessHART networks in Distributed Control Systems using PROFINET IO

In this paper we describe a method to integrate WirelessHART networks in Distributed Control Systems (DCS) using PROFINET IO. By modeling the WirelessHART network in the Generic Station Description file, that describes a PROFINET IO device, the WirelessHART related configuration can be distributed from the central engineering stations. In this way, both process controller configuration and WirelessHART network configuration is engineered and maintained from a central location. Thus the end-user does not need any additional tool-specific training, as the existing tools are used to engineer the WirelessHART networks. We base the method of integration on the keywords simple deployment and maintenance, and flexible topology. A proof-of-concept implementation of the proposed method shows that it is possible to downloadWirelessHART configuration both to the WirelessHART network managers, as well as the WirelessHART sensors. By integrating WirelessHART in this way, maintenance is greatly simplified as the actual configuration will be downloaded automatically by the DCS when faulty field devices are replaced.

Wireless Vibration Monitoring (WiVib) - An industrial case study

Testing in realistic environments is often overlooked in the early development of new technology. This paper describes a test to evaluate the whole chain from an accelerometer mounted on a motor to a sensor node sending wireless data to an access point. A pilot gives a great opportunity to get input from end-users (which could be very useful at the initial stages of a project), and provide potential contacts for next pilots. The goal of the pilot was to get a better understanding of the targeted environment and possible interference It may also lead to the discovery of issues not yet thought of issues important for the resulting design of the end product.

Positioning infrastructure for industrial automation systems based on UWB wireless communication

In various industrial automation applications, positioning enables location awareness which can be exploited in applications such as robotic precision control, amongst others. This paper discusses positioning for industrial automation applications. Examples of applications from an infrastructure perspective are presented, and the integration of high precision positioning technology into existing network infrastructure for such applications is discussed, as well as challenges involved. An impulse-radio ultra-wideband 802.15.4a based system for high accuracy/precision positioning is presented, which shows promising results, therefore motivating the use of UWB as a high accuracy and precision technology for positioning applications in future industrial automation systems.

Evaluation of WirelessHART enabled devices in a controlled simulation environment

Evaluation of Wireless Sensor Networks is difficult. Due to lack of standard implementations, stringent time requirements and security enabled communications evaluation of WirelessHART networks is challenging. This makes it very hard to compare, evaluate and test WirelessHART networks even controlled environments. We propose a hybrid simulation framework that is tailored for the WirelessHART protocol. Our solution enables evaluations and tests of WirelessHART networks and WirelessHART-enabled devices in a controlled simulation environment.