Niklas Goddemeier

Role-Based Connectivity Management with Realistic Air-to-Ground Channels for Cooperative UAVs

Ad-hoc aerial sensor networks leveraging MUAVs (Micro Unmanned Aerial Vehicles) are ideally suited to cost-efficiently explore unknown or hostile environments for example in case of incidents producing harmful gases or radiation. In this manuscript we present results on the investigations of communication-aware steering algorithms for cooperative MUAV swarms. The mission objective is to achieve a maximum spatial exploration efficiency with the simultaneous ability to self-optimize the communication links by exploiting controlled mobility. While our previous work has mainly considered the performance of the Air-to-Air mesh network, in this paper we focus on the Air-to-Ground-link connectivity control. To achieve appropriate communication links to a central sensor data sink even while exploring larger search areas, an agent-based role management strategy is used to provide suitable multi-hop connectivity. The novel algorithms are investigated for static as well as dynamically changing environments. Key results include a detailed realistic aerial channel characterization and network dimensioning analysis considering numbers of MUAVs and density of ground stations vs. exploration speed and sensor data latency.

Cognitive Agent Mobility for Aerial Sensor Networks

For efficient sensor coverage of large industrial and incident areas, fast and flexible strategies for collecting sensor data through an autonomous, wirelessly connected swarm of (Micro) Unmanned Aerial Vehicles (MUAVs) are still an emerging challenge. Deploying multiple MUAVs which stably carry sensing equipment in hostile environments yields cost efficiency and reducing the risk to human life. The use of an aerial ad hoc sensor network based on MUAV agents promises more timely and accurate information by fusing measurements from different types of sensors. In this paper, we examine agent-based mobility algorithms that target high spatial coverage distribution, high total coverage, and high-quality communication links. For these key figures, the performance of the different novel mobility algorithms is evaluated. We particularly focus on channel aware mobility and on self-organizing mesh topologies of MUAV-based sensor swarms with respect to communication constraints.

Attitude estimation and control of a quadrocopter

The research interest in unmanned aerial vehicles (UAV) has grown rapidly over the past decade. UAV applications range from purely scientific over civil to military. Technical advances in sensor and signal processing technologies enable the design of light weight and economic airborne platforms. This paper presents a complete mechatronic design process of a quadrotor UAV, including mechanical design, modeling of quadrotor and actuator dynamics and attitude stabilization control. Robust attitude estimation is achieved by fusion of low-cost MEMS accelerometer and gyroscope signals with a Kalman filter. Experiments with a gimbal mounted quadrotor testbed allow a quantitative analysis and comparision of the PID and Integral-Backstepping (IB) controller design for attitude stabilization with respect to reference signal tracking, disturbance rejection and robustness.

Coverage evaluation of wireless networks for Unmanned Aerial Systems

Unmanned Aerial Vehicles (UAVs) gained a lot popularity during the last years and are used in many applications ranging from reconnaissance over disaster recovery to remote sensing [1][2]. In most applications some sort of communication link is needed to transmit telemetry and payload data. Especially for homeland security and civil operations the realization is sometimes very demanding due to missing radio frequencies. In order to overcome this constraint we investigate the usability of existing cellular networks. Considering these UAVs to communicate by means of cellular networks for establishing reliable air-to-ground links, claims an analysis and evaluation of the cellular channel characteristics in the low altitude operational area. In this paper we present a coverage analysis for cellular networks for altitudes up to 500m based on aerial RSSI measurements.

Link quality dependent mobility strategies for distributed aerial sensor networks

The in-depth reconnaissance and surveillance of incidents that are caused by uncontrolled emissions of liquid or gaseous contaminants, e.g. in cases of volcanic eruptions, large fires, industrial incidents or terrorist attacks, is still an emerging challenge. Mounting sensors on unmanned aerial vehicles (UAV) is a feasible approach since recent advances in the area of propulsion, carbon reinforced materials and batteries enable for miniaturization and cost-efficient deployment. Our proposed system makes use of an autonomous, wireless connected swarm of Micro UAVs, that is featured with a lightweight mobile sensor system. For this purpose a mobile ad hoc remote sensing network is set up in the air, that allows for calculation of potential fields like a aerosol propagation maps or 3D geomorphologies. Next to this system-of-systems approach, we uniquely show how to optimize the spatial sensor coverage while maintaining the communication quality. In this paper we analyze the equilibrium between coverage and link quality for a cluster based mobility scheme which is combined with randomized cognitive repelling walks.

AVIGLE: A system of systems concept for an avionic digital service platform based on Micro Unmanned Aerial Vehicles

Miniaturized unmanned flying robots, also referred to as MUAVs (Micro Unmanned Aerial Vehicles) open up completely new fields of innovative applications in the areas of civil security, cellular networks, surveying, entertainment and media. The AVIGLE project is based on the vision of a novel, widely applicable avionic service platform which supports multiple high-tech services by using open interfaces. Recent developments in the area of lithium polymer batteries and carbon fiber-reinforced plastic materials let MUAVs become an aerial platform, that can be equipped with a variety of sensors such as image or time of flight (ToF) cameras. Furthermore, it is also possible to mount communication technologies on the platform in order to let the MUAVs work as communication hot spots or relais at places where no cellular networks are available. In this paper we present a system of systems concept of an Unmanned Aerial System working as a service platform for different Concepts of Operations (ConOps).

PASER: Secure and Efficient Routing Approach for Airborne Mesh Networks

Low-altitude unmanned aerial vehicles (UAVs) combined with WLAN mesh networks (WMNs) have facilitated the emergence of airborne network-assisted applications. In disaster relief, they are key solutions for (1) on-demand ubiquitous network access and (2) efficient exploration of sized areas. Nevertheless, these solutions still face major security challenges as WMNs are prone to routing attacks. Consequently, the network can be sabotaged, and the attacker might manipulate payload data or even hijack the UAVs. Contemporary security standards, such as the IEEE 802.11i and the security mechanisms of the IEEE 802.11s mesh standard, are vulnerable to routing attacks as we experimentally showed in previous works. Therefore, a secure routing protocol is indispensable for making feasible the deployment of UAV-WMN. As far as we know, none of the existing research approaches have gained acceptance in practice due to their high overhead or strong assumptions. Here, we present the position-aware, secure, and efficient mesh routing approach (PASER). Our proposal prevents more attacks than the IEEE 802.11sΓi security mechanisms and the well-known, secure routing protocol ARAN, without making restrictive assumptions. In realistic UAV-WMN scenarios, PASER achieves similar performance results as the well-established, nonsecure routing protocol HWMP combined with the IEEE 802.11s security mechanisms.

Experimental validation of RSS driven UAV mobility behaviors in IEEE 802.11s networks

In this research work, we describe and analyze the transition from simulation to experimental validation of communication-aware mobility behaviors for unmanned aerial vehicles (UAVs). Two reference scenarios are simulated and carried out using an experimental UAV testbed. The results are compared to determine the gap between simulation and reference implementation. In this work, we show that the received signal strength (RSS) can be used as a steering metric in communication-aware mobility behaviors. The proposed concept from simulation to outdoor experiments helps to reduce development time and failure risk due to the incremental substitution of simulated components with real implementations.

Channel Aware mobility for self organizing wireless sensor swarms based on low altitude platforms

Based on the recent developments in the area of lithium polymer batteries and carbon fiber-reinforced plastic materials Micro Unmanned Aerial Vehicles (MUAV) significantly gain in importance. The use of cognitive MUAV swarms for distributing mobile sensors is a significant value add for chemical plume detection in rescue missions and also in particular for remote sensing and surveillance purposes [1][2]. The objective of our proposed cognitive and sensor aided mesh network is to maximize the spatial sensing coverage on the one hand and the connectivity between the cooperative MUAVs on the other. Next to these contrary optimization goals we developed bio-inspired algorithms seeking concurrently for a global target and a coherent topology of the swarm in order to avoid self-separations. In this paper we particularly focus on an agent-based methodology for communication aware mobility behavior of self-organizing MUAVs at high vehicular speeds which provoke fast topology changes and lead to a transient aerial mesh network. To determine the key figures of the system, the performance of dynamically adapted mobility algorithms is analyzed and compared under lognormal channel conditions.

Communication constrained mobility and topology management for relay sensor networks

In this paper we propose distributed algorithms that solve the coverage problem in 3D space. In particular, we use a swarm of unmanned aerial vehicles (UAVs) in order to explore a possibly unknown area. Actual use cases include the automated acquisition of sensory data in operations that try to gain extensive knowledge about an area. First, we try to efficiently cover a predefined 3D space with multiple UAVs. Second, we target to maintain intra-swarm connectivity during the whole operation. Consequently, we develop and enhance metrics for benchmarking the resulting system with respect to coverage and communication capabilities. The algorithms were optimized towards getting a quick overview that is iteratively refined by getting more accurate data. This principle is similar to mip-mapping in computer graphics.