Andreas Bierig

Challenges for Health Monitoring of Electromechanical Flight Control Actuation Systems

Flight control systems of civil aircraft have undergone huge developments in the last decades. The current more/all electric aircraft concepts lead to the replacement of the hydraulic actuators in the primary flight control systems by electromechanical systems. Integrating electromechanical systems in safety critical applications implies three main challenges: (a) the detection of all fault cases which could lead to a safety critical state, (b) finding measurement parameters capable to detect faults, and (c) the development of algorithms to detect faults under all flight conditions. Putting the scope on the health monitoring of the mechanical components of a direct drive actuator, a new technology based on piezoresistive thin film sensors (TFS) is presented and its potential shown by using defective ball bearings as an example.

Robustness Analysis Related to the Control Design of the SHEFEX-II Hypersonic Canard Control Experiment

This paper presents the simulation based robustness analysis w.r.t. parameters and initial conditions, related to the hypersonic flight experiment called SHEFEX-II. The robustness criteria and the parameter limits are obtained from the nominal mission profile, the vehicles configuration, and the results of a previous flight test in 2005. Necessary background knowledge and the nominal mission profile are presented. Simulation results are introduced to define the nominal and the worst case trajectories. Due to the fast changing air density during the reentry flight, simulations with modified initial conditions are used to determine the desired damping. Furthermore, preliminary flight test results are presented and discussed.

Identifying drone-related security risks by a laser vibrometer-based payload identification system

Various drone detection systems (DDS) have been recently developed for civil and military applications. Such DDS are generally based on radio frequency (RF) radars, detecting control signals between drones and their pilots, drones acoustic noise, optical surveillance, or a combination of these. However, existing DDS have safety critical gaps. For example, none of the current state-of-the-art technologies provide remote payload monitoring or verification. The registered payload of some commercial drones can be greatly increased by simple re-configuration procedures that may not be detected by current DDS. This study introduces patent-pending methods for remote identification and payload monitoring of standard and modified drones. Structural frequencies, measured by a long-range laser vibrometer, of commercial drones are proposed as a unique signature for remotely verifying registered specifications of a drone, e.g., payload capacity. In addition, a method is proposed to measure payload capacity of unknown drones based on their motion performance monitored via a motion dynamic model and a laser Doppler vibrometer. Preliminary flight tests have been successfully conducted for a group of standard and modified drones by the Institute of Flight Systems, DLR (German Aerospace Center).

Automated vibration-based fault size estimation for ball bearings using Savitzky–Golay differentiators

Vibration-based fault diagnosis has been utilized as a reliable method for identifying ball bearings health since the 1970s. Recently, there has been an increased research effort to develop methods for fault quantification with the aim of estimating the fault size to allow the service life of a ball bearing to be extended beyond the detection stage. These studies have shown that the vibration signal from a localized spall (e.g. fatigue defect) in a ball bearing exhibits features corresponding to two main events, namely, the entry into and the exit from the spall. The time span between these two events is correlated with the spall size. Studies have shown that the entry into the spall is the more challenging event to identify, which often requires extensive signal processing techniques. This paper introduces an automated vibration-based technique for estimating the size of a spall in a ball bearing under axial loading conditions similar to those of linear electro-mechanical actuators. This technique is based on the extraction of the entry/exit events from the vibrational jerk, which are numerically determined from accelerometer data. The differentiation of the acceleration data to estimate jerk signal is performed using a variant of Savitzky–Golay (SG) differentiators, which provide enhancement for the detection of the entry and exit points. Sensible spall size estimations have been achieved for 24 different scenarios of fault sizes, rotor speeds and loads measured on a test rig provided by DLR (German Aerospace Center).

Design of the general systems for the SAGITTA demonstrator UAV

Unmanned Aerial Vehicles (UAV) with a maximum takeoff weight of up to 150 Kg are enjoying increasing popularity, especially as scaled-down demonstrator aircraft for future civil and military applications. This paper gives an overview about the development of the general systems for the SAGITTA demonstrator aircraft. General systems is an Airbus Defence and Space term and covers all flight safety critical systems except the engine and flight control computers. The SAGITTA demonstrator aircraft is a scaled-down UAV for the purpose of demonstrating capabilities of future Unmanned Combat Aerial Vehicle (UCAV). On system level, the realization of the electrical power supply system, the electromechanical actuation system, the fuel system and the design of a retractable landing gear for the demonstrator aircraft is described. Since there is still no significant market for systems of a relevant size for aircraft of the dimension of SAGITTA, most of the components are essentially new developments. This paper gives an overview about the main design considerations of these systems.

Dynamic reconfigurability of wireless sensor and actuator networks in aircraft

The wireless spectrum is a scarce resource, and the number of wireless terminals is constantly growing. One way to mitigate this strong constraint for wireless traffic is the use of dynamic mechanisms to utilize the spectrum, such as cognitive and software-defined radios. This is especially important for the upcoming wireless sensor and actuator networks in aircraft, where real-time guarantees play an important role in the network. Future wireless networks in aircraft need to be scalable, cater to the specific requirements of avionics (e.g., standardization and certification), and provide interoperability with existing technologies. In this paper, we demonstrate that dynamic network reconfigurability is a solution to the aforementioned challenges. We supplement this claim by surveying several flexible approaches in the context of wireless sensor and actuator networks in aircraft. More specifically, we examine the concept of dynamic resource management, accomplished through more flexible transceiver hardware and by employing dedicated spectrum agents. Subsequently, we evaluate the advantages of cross-layer network architectures which overcome the fixed layering of current network stacks in an effort to provide quality of service for event-based and time-triggered traffic. Lastly, the challenges related to implementation of the aforementioned mechanisms in wireless sensor and actuator networks in aircraft are elaborated, and key requirements to future research are summarized.