Due to the growing threat of a wide range of unmanned aerial vehicles (UAVs), including consumer micro-drones that are increasingly used for defense purposes, the need to develop active and passive countermeasures against armed and intelligence gathering UAVs has been identified in order to increase force protection, critical infrastructure resilience, and information security. Several counter-drone solutions have been reported. To accomplish the task of UAV localization, in addition to electro-optical detection and tracking, we consider the distance determination as a fundamental task for stand-alone observation stations. Laser Ranging is one of the promising tools and currently widely used in determination of distance to large objects or slow-moving targets. Within the scope of this paper we are going to evaluate the features and limitations, when applying it for performing laser ranging on UAV. As a target, we are using a typical representative of commercial micro UAV. In this paper, we will present theoretical analysis and experimental results of UAV laser range measurements under realistic environmental conditions. Investigations about the laser transmitter signal are included. We are going to describe qualitative results of laser ranging at different operational modes. Research is based on ranging micro UAV from different directions and various distances. To estimate the maximum ranging distance on the limits of our system, we are going to apply an artificial scaled reference target. This target creates the same optical reflectance cross section as our commercial micro UAV with a given distance.
We present a new approach to an optical UAS detection system that confirms several requirements specified by the authorities. Our UAS detection system consists of a ground unit and a folding mirror located in the air. The ground based unit contains high resolution camera system mounted on a pan tilt unit. Therefore, the lens of the camera system can be actively aligned to a convex mirror which is located in vertical distance over the ground unit on the lower side of a raised captive balloon. The focal length of the ground based lens, the altitude of the balloon and the curvature of the mirror define the field of view towards the ground. The recorded video streams are processed in a vision system using change detection and other algorithms to alert a UAS intrusion. We will outline the design parameters of the optical system, the requirements and the implementation of the mechanical system as well as the active alignment system and show first results of outdoor operation
Lasers arouse an increasing interest in remote sensing applications. In order to deliver as much as possible of the available laser power onto a flying object the subsystems of a beam control system have to operate precisely together. One important subsystem is responsible for determination of the target’s angular position.
Here, we focus on an optical system for measuring precisely the angular position of flying objects. We designed this subunit of a beam control system exclusively from readily available commercial-off-the-shelf components. Two industrial cameras were used for angle measuring and for guiding the system to the position of the flying object. Both cameras are mounted on a modified astronomical mount with high-precision angle encoders. To achieve a high accuracy we temporally synchronize the acquisition of the angle from the pan tilt unit with the exposure of the camera. Therefore, a FPGA-based readout device for the rotary encoders was designed and implemented. Additionally, we determined and evaluated the influence of the distortion of the lenses to the measurement.
We investigated various scenarios to determine the accuracy and the limitations of our system for angular position determination of flying targets. Performance tests were taken indoor and outdoor at our test sites. A target can be mounted on a fast moving linear stage. The position of this linear stage is continuously read out by a high resolution encoder so we know the target’s position with a dynamic accuracy in the range of a few μm. With this setup we evaluated the spatial resolution of our tracking system. We showed that the presented system can determine the angular position of fast flying objects with an uncertainty of only 2 μrad RMS. With this mobile tracking system for angular position determination of flying targets we designed an accurate cost-efficient opportunity for further developments.
Different types of high power or high energy lasers in the multi kW class are currently available or are under development with promising progress reports. A major challenge is to deliver as much as possible of the available power onto a small and fast moving target over a long distance through a disturbing atmosphere.
High resolution imaging is a common way to identify the category of targets dedication and to determine the spatial position relative to the observer. By illuminating the target with a laser the imaging system becomes more resilient towards ambient light and the exposure time can be reduced drastically. Fast and deterministic control loops are demanding for the moving parts in order to maintain a high accuracy for the pointing of the turret and aiming of the laser countermeasure system.
Here, we report on the progress of such a beam control system developed at the Institute of Technical Physics of DLR. In an overview we present the beam control system and explain different sub-systems. Performance tests were taken at our test. At a distance we simulated various scenarios for probing the limits of the tracking and pointing accuracy with a target on a fast moving linear stage. We present first results of the beam control system performance.