Ulf Witkowski

Fachhochschule Südwestfalen · Fachbereich Elektrische Energietechnik

The BLE Mesh standard is well suited for use in IoT applications because of its low energy consumption. The Mesh extension enables communication beyond directly connected devices. The provisioning of the network can be performed using a smartphone utilizing a compatibility layer for traditional BLE. Connectivity to the Internet is required for many...

In agriculture, it becomes more and more important to have detailed data, e.g. about weather and soil quality, not only in large scale classic crop farming applications but also for urban agriculture. This paper proposes a modular wireless sensor node that can be used in a centralized data acquisition scenario. A centralized approach, in this case...

A wireless sensor node with Wi-Fi interface has been developed and applied to measure air quality parameters. The node can be used for different indoor sensing applications, but the currently addressed application context is to reduce the risk of virus infection that is related to the aerosol concentration in a room. As a helpful measure, the carbo...

This paper focuses on the implementation of a Kalman filter for a sensor fusion task and the testing and validation of the implementation by using a test platform. Implementation device for the sensors and the fusion algorithm is the mini-robot platform Zorro that is equipped with multiple sensors. In order to internally develop a consistent model...

High junction temperature of LEDs can significantly decrease their lifespan. The colour and light intensity can also change by LED overheating. Therefore, a thermal management has to be implemented into the LED driver to prevent overheating and to realize long lifetimes of LEDs. Measuring or good estimation of the temperature of the LED junction is...

In this paper, we advance the thesis that educational robots can make a much larger contribution in the classroom than has hitherto been the case. However, to realise this potential, it is necessary to supply teachers with detailed guides for classroom robotic student activities for achieving specific curricular learning objectives. As illustration...

The development of mobile robots or in general autonomous mobile systems is a complex task. These systems are characterized by a set of sensors and actuators as well as software running on computing hardware. Depending on the foreseen tasks of designing a mobile system, the overall complexity of the design may range from a few integrated components...

In contrast to classical light bulbs, LEDs used for lighting applications achieve greater energy efficiency. Nevertheless, LEDs are not lossless; power loss generates heat in the semiconductor junctions as well as in the light conversion material. High temperature significantly impairs the luminescent material and results in degeneration of the lum...

Renewable energy sources continue to gain popularity. However, two major limitations exist that prevent widespread adoption: System power reliability under varying weather conditions and the corresponding system cost. The wide range of performance characteristics of storage technologies motivates the use of hybrid energy storage systems (HESS) to o...

In this paper, the localisation capabilities of ultra-wideband (UWB) communication devices are evaluated. A test platform is designed to perform experiments in indoor environments, to record the data for different node set-ups and to evaluate the results in practice. The platform development comprises hardware design of the anchor and tag node, dev...

Today's LEDs operate with high current, causing a significant increase in the device's temperature despite the LEDs being highly energy efficient. Important for having a long LED lifetime is accurate temperature management which requires sensing the device temperature and knowing the temperature distribution. The underlying aim of the project is to...

This paper describes a low cost autonomous robot platform with an integrated smartphone. The robot is engineered to play robot soccer in the AMiREsot league as well as be used as an educational platform and for research purposes. The robot’s base board includes the electronics required for driving and controlling the motors, accessing the infrared...

The Autonomous Mini-Robot Soccer Tournament (AMiRoSoT) league that we describe in this article uses small size robots and a small size field to make the league widely accessible for education and research by keeping the entry barrier to the competition low. We describe the motivation for small size soccer robots and the design criteria applied to t...

This paper focuses on a resource (people or equipment) tracking approach involving radio localization and wireless communication for use in search and rescue scenarios. Two alternative communication options (ZigBee and GSM) are used to facilitate robust wireless data transfers between nodes through either an ad-hoc network or base station. The onbo...

This paper presents an implementation of a tree network topology which serves as the network backbone for a wireless sensor network (WSN) that is composed out of advanced Bluetooth low energy (BLE) wireless technology. Bluetooth LE supports the star network topology; however the tree network topology is not supported. To implement a tree topology,...

This paper focuses on the design of a low power sensor node that supports wireless communication via Bluetooth Low Energy (BLE) based on the TI System On Chip (SOC) CC2541 device. The network node integrates sensors for ambient monitoring, e.g. the recording of temperature, 3D acceleration and ambient light measurement. Recorded data can be sent vi...

Swarm robotics has pulled the attention of scientists for its flexibility, redundancy, stability, emergent intelligence and many other features. One major issue in design of swarm robots is the communication system. In spite of existence of currently employed communication systems in swarm robots such as IR, Bluetooth, ZigBee, etc. still it has not...

Difficulties in programming and debugging programmable components waste large amounts of development time. In this paper a new technique for programming devices with NFC technology is presented which simplifies the process and significantly reduces the tasks of software developers. In this technique, a PC application reads the content of the data w...

This paper describes an autonomous modular mobile robot platform. The robot is able to play robot soccer in the AMiREsot league. The construction of the robot is based on a chassis with two wheels and two motors. A base board that is attached to the chassis realizes the motor control and generates low-level behaviour like obstacle avoidance and dri...

This paper introduces a concept for the integration of the LEGO MINDSTORMS system into the undergraduate curriculum for electrical engineering students. The concept proposes an optional project-oriented module for students in the first semester and contains typical topics from programming, embedded design and mobile robotics. Besides the positive e...

The general procedure of visual odomentry (VO) for a mobile robot based on a monocular image stream can be subdivided into different subtasks. The minimal configuration of a VO framework illustrated in the following figure contains three major subtasks: feature handling, structure recovery and motion recovery. The motion recovery is solved by incor...

The local behavior and local navigation of a mobile robot depends on the availability and quality of environment data, e.g., the information on the presence of obstacles or free space area as a minimum. In this work we focus on a sensor system that can be used under low and no visibility conditions as they may appear in dense smoke or dust. The rel...

The design of digital hardware is nowadays very well supported by software tools, which allow hardware description, hardware synthesis, and complex simulations ranging from device to system simulations. For teaching at universities often a bunch of complex software tool chains is available and is used in classes and for lab work, but practical expe...

One of the most promising applications of a multi-robot system is to assist humans in urban search and rescue (USAR) scenarios in the aftermath of natural or man-made disasters. The main disaster scenario covered by our system is a large industrial warehouse on fire, described in the GUARDIANS project funded by the European Union 6th Framework Prog...

Mobile robots are widely used in industrial environments and are expected to be widely available in human environments in the near future, for example, in the area of care and service robots. This article proposes an implementation for a highly customizable color recognition module based on Field Programmable Gate Array (FPGA) hardware to accomplis...

Emergencies in industrial warehouses are a major concern for fire fighters. The large dimensions together with the development of dense smoke that drastically reduces visibility, represent major challenges. The Guardians robot swarm is designed to assist fire fighters in searching a large warehouse. In this paper we discuss the technology developed...

This paper presents empirical results of the effect of the global position information on the performance of the modified local navigation algorithm (MLNA) for unknown world exploration. The results show that global position information enables the algorithm to maintain 100% success rate irrespective of initial robot position, movement speed, and e...

This paper presents a flexible prototyping platform that can be efficiently used for vision systems of small mobile robots. The vision module has been integrated into the mini-robot “Khepera”. The module is utilized to realize optical flow algorithm for obstacle avoidance. The obstacles are detected from abrupt change of the normal flow vectors dur...

We present our contribution in projects related to ad-hoc networking using different routing protocols and hardware platforms, showing our results and new solutions regarding topology control and routing protocols. We mainly focus on our work in the GUARDIANS EU-project, where as a main disaster scenario a large industrial warehouse on fire is assu...

Robots exploring unknown territory cannot rely on fixed infrastructure for communication and localization purposes. Therefore an ad-hoc communication and localization system is required to provide such facilities. In this paper a solution for a radio based localization system is presented using a 2.4 GHz wireless radio transceiver based on Chirp Sp...

Mobile robots become more and more important in current research and education. Especially small ’on the table’ experiments attract interest, because they need no additional or special laboratory equipments. In this context platforms are desirable which are small, simple to access and relatively easy to program. An additional powerful information p...

AMiRESot is a new robot soccer league that is played with small autonomous miniature robots. Team sizes are defined with one, two, and three robots per team. Special to the AMiRESot league are the fully autonomous behavior of the robots and their small size. For the matches, the rules mainly follow the FIFA laws with some modifications being useful...

Robot development is a highly complex and interdisciplinary process. It comprises several phases: design, implementation, as well as test and validation to name some of them. In test and validation, simulation is commonly used. However, experiments with real robots still have a very important role since simulations cannot accurately model the real...

Communication has an important role in multi-robot systems. It can facilitate cooperation, therefore, improve the performance of the system significantly. In this study we investigated the benefits of networked communication by experimentally evaluating the results of two search algorithms which are spiral search and informed random search. The exp...

A neural network-based camera calibration method is proposed for mobile robot equipped with a CMOS vision module. Camera calibration is the process of determining the coordinate relationship between a camera image and its real world space. Accurate camera calibration is required for achieving accurate visual measurements. In order to localize and n...

This paper describes a resource-efficient vision system for the mini-robot “Khepera”. It is implemented to perform a fundamental approach of robotic navigation, which is obstacle detection by using an optical flow algorithm. This is inspired by visual perception of insects. The optical flow field is evaluated by implementing the sum of absolute dif...

In this paper, a platform for managing and providing remote access to robots was developed and constructed. The system helps to schedule, perform and analyze experiments using minirobots. A solution for recharging the robots automatically has been included in the system in order to save the time needed for manual recharging. The system can automati...

This paper presents a Modified Multiple Depth First Search algorithm for the exploration of the indoor environments occupied with obstacles in random distribution. The proposed algorithm was designed and implemented to employ one or a team of Khepera II mini robots for the exploration process. In case of multi-robots, the BlueCore2 External Bluetoo...

In this paper, we will consider the localization problem of an autonomous minirobot. Localization is the process of finding both position and orientation of a vehicle. Mobile robots must be able to localize itself in a plane to operate successfully. We propose a new Alternative Geometric Triangulation (AGT) algorithm to the triangulation algorithms...

In this paper, we will consider the localization problem of the autonomous minirobot Khepera II in a known environment. Mobile robots must be able to determine their own position to operate successfully in any environments. Our system combines odometry and a 2-D vision sensor to determine the position of the robot based on a new triangulation algor...

This paper describes a platform for assisting researchers and/or students to perform and validate experiments using real robots in robot soccer domain. Some important features are: live-video of the experiment, recording video for the experiment, data logging of exchanged messages, robots positioning system, downloading user- specific program to ea...

This paper presents a teleoperated robotic-laboratory named Teleworkbench and its benefit for educational purpose. It also presents briefly three issues that we need to take into consid- eration to make such a laboratory more effective.

This paper presents a stereoscopic vision system for the mini-robot Khepera. The vision system performs objects detection by using the stereo disparity and stereo correspondence. The stereoscopic vision system enhances robot's visual perception ability by grabbing stereo images and analysis 3D objects, while the robot doesn't need to move. The simp...

Reconfigurable hardware (e.g., field programmable gate arrays - FPGAs) has been successfully used as processing units in various mini-robotic applications. In this work, we pursue to improve the utilization of reconfigurable hardware by introducing dynamic reconfiguration. A hardware-software architecture is presented, which enables the realization...

In this chapter we discuss an implementation of self-organizing feature maps in reconfigurable hardware. Based on the universal rapid prototyping system RAPTOR2000 a hardware accelerator for self-organizing feature maps has been developed. Using state of the art Xilinx FPGAs, RAPTOR2000 is capable of emulating hardware implementations with a comple...

This paper presents a tool, one component of the Teleworkbench system, for analyzing experiments in multi-robotics. The proposed tool combines the video taken by a web cam monitoring the field where the experiment runs and some computer generated visual objects representing important events and information as well as robots’ behavior into one inter...

This paper describes a tool for analyzing robotic experiments. The proposed tool uses the MPEG-4 standard to visualize information acquired during an experiment. To provide a sense of reality, we use a video taken by an overhead webcam monitoring the field where the experiment runs. On top of the video, we generate some synthetic objects representi...

If robots are deployed in large numbers in our environment in future, collaboration between the presumably specialized robots will be essential for a successful operation. The robots will set up mobile ad-hoc networks for communication and efficient routing and discovery protocols for such robot networks will provide the basic layer for a successfu...

If robots are deployed in large numbers in disaster scenarios, the ability to discover and exchange resources and services with other robots in an open, heterogeneous, large-scale network would be essential for a successful operation. In this paper we present a discovery protocol that enables robots to efficiently locate resources and services avai...

In the field of explorative data analysis self-organizing maps have been used successfully for a lot of applications. In our case, we apply the self-organizing map for the analysis of semiconductor fabrication data by training recorded high dimensional data sets. Usually, the training result is displayed by using appropriate visualization technique...

An analog VLSI implementation of adaptive synapses being part of an associative memory realised with pulsed neurons is presented. VLSI implementations of dynamic synapses and pulsed neurons are expected to provide robustness and low energy consumption like observed in the human brain. We have developed a VLSI implementation of synaptic connections...

This paper describes a communication and control infrastructure for autonomous mini-robots, which is based on Bluetooth wireless communication technology. In mobile robots, one of the most important issues is power consumption which limits the lifetime of the robot. In this respect, for communication, a technology that requires the least energy is...