Mr. Christian Walko Profile

Christian Walko

at German Aerospace Center

Publications (4)

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SPIE Journal Paper | 21 October 2021 Open Access

Flying a helicopter with the HoloLens as head-mounted display

Christian Walko, Malte-Jörn Maibach

OE, Vol. 60, Issue 10, 103103, (October 2021) https://doi.org/10.1117/12.10.1117/1.OE.60.10.103103

KEYWORDS: Head, Head-mounted displays, Holograms, Cameras, Calibration, Optical engineering, Optical tracking, Filtering (signal processing), Electromagnetism, Augmented reality

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We describe the flight testing and the integration process of the Microsoft HoloLens 2 as head-mounted display (HMD) with DLR’s research helicopter. In the previous work, the HoloLens was integrated into a helicopter simulator. Now, while migrating the HoloLens into a real helicopter, the main challenge was the head tracking of the HoloLens, because it is not designed to operate on moving vehicles. Therefore, the internal head tracking is operated in a limited rotation-only mode, and resulting drift errors are compensated for with an external tracker, several of which have been tested in advance. The fusion is done with a Kalman filter, which contains a non-linear weighting. Internal tracking errors of the HoloLens caused by vehicle accelerations are mitigated with a system identification approach. For calibration, the virtual world is manually aligned using the helicopter’s noseboom. The external head tracker (EHT) is largely automatically calibrated using an optimization approach and therefore, works for all trackers and regardless of its mounting positions on vehicle and head. Most of the pretests were carried out in a car, which indicates the flexibility in terms of vehicle type. The flight tests have shown that the overall quality of this HMD solution is very good. The conformal holograms are almost jitter-free, there is no latency, and errors of lower frequencies are identical with the performance that the EHT can provide, which in combination greatly improves immersion. Profiting from almost all features of the HoloLens 2 is a major advantage, especially for rapid research and development.

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Proceedings Article | 12 April 2021 Presentation + Paper

Flying a helicopter with the HoloLens as head-mounted display

Christian Walko, Malte-Jörn Maibach

Proceedings Volume 11759, 117590F (2021) https://doi.org/10.1117/12.2588764

KEYWORDS: Head, Head-mounted displays, Error analysis, Cameras, Calibration, System identification, Reverse engineering, Neural networks, Light emitting diodes, Infrared radiation

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This paper describes the flight testing and the integration process of the Microsoft HoloLens 2 as head-mounted display with DLR's research helicopter ACT/FHS. In previous work, the HoloLens was integrated into a helicopter simulator. Now, while migrating the HoloLens into a real helicopter, the main challenge was the head tracking of the HoloLens, because it is not designed to operate on moving vehicles. Therefore, the internal head tracking is operated in a limited rotation-only mode and resulting drift errors are compensated with an external tracker, various of which have been tested in advance. The fusion is done with a Kalman filter, which contains a nonlinear weighting. Internal tracking errors of the HoloLens caused by vehicle accelerations are mitigated with a system identification approach. For calibration, the virtual world is manually aligned using the helicopter's noseboom. The external head tracker is largely automatically calibrated using an optimization approach, and therefore works for all trackers and regardless of its mounting positions on vehicle and head. Most of the pre-tests were carried out in a car, which indicates the flexibility in terms of vehicle type. The flight tests have shown that the overall quality of this head-mounted display solution is very good. The conformal holograms are jitter-free, there is no latency and errors of lower frequencies are small enough, which greatly improves immersion. Profiting from almost all features of the HoloLens 2 is a major advantage, especially for rapid research and development.

SPIE Journal Paper | 28 April 2020

Integration and use of an augmented reality display in a maritime helicopter simulator

Christian Walko, Niklas Peinecke

OE, Vol. 59, Issue 04, 043104, (April 2020) https://doi.org/10.1117/12.10.1117/1.OE.59.4.043104

KEYWORDS: Holograms, Augmented reality, Head, Sensors, LIDAR, Visualization, Head-mounted displays, Glasses, Optical spheres, Optical engineering

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Operating a helicopter in offshore wind parks with degraded visual environments from clouds or fog can endanger crew and material due to the presence of unseen obstacles. Utilizing on-board sensors such as LIDAR or radar, one can sense and record obstacles that could be potentially dangerous. One major challenge is to display the resulting raw sensor data in a way that the crew, especially the pilot, can make use of it without distracting them from their actual task. Augmented reality and mixed reality applications play an important role here. By displaying the data in a see-through helmet-mounted display (HMD), the pilot can be made aware of obstacles that are currently obscured by degraded visual conditions or even parts of the helicopter. This can be accomplished in one HMD. No attention sharing between the outside view and a head-down instrument is necessary. The German Aerospace Center (DLR) is continuously aiming at testing and evaluating both flight-proof and consumer grade HMDs. One particular widely known system is the Microsoft HoloLens. DLR will integrate this low-cost HMD into their experimental helicopter. For this, as a first step, a Microsoft HoloLens was integrated into DLR’s Air Vehicle Simulator (AVES). The integration process is detailed. The simulation capabilities are described, especially for conformal, open-loop LIDAR sensor data. Furthermore, first concepts of the display format are shown, and strengths and drawbacks of the HoloLens in a cockpit environment are discussed.

Proceedings Article | 1 May 2019 Paper

Integration and use of an AR display in a maritime helicopter simulator

Christian Walko, Niklas Peinecke

Proceedings Volume 11019, 1101905 (2019) https://doi.org/10.1117/12.2520142

KEYWORDS: Holograms, Head, Sensors, Glasses, LIDAR, Augmented reality, Visualization, Head-mounted displays

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Operating a helicopter in off-shore wind parks in DVE from clouds or fog can endanger crew and material due to the presence of unseen obstacles. Utilizing on-board sensors like Lidar or radar one can sense and record obstacles that could be potentially dangerous. One major challenge is then to display the resulting raw sensor data in a way that the crew, especially the pilot can make use of without distracting them from their actual task. Augmented and mixed reality applications are thought to play an important role here. By displaying the data in a see-through helmet mounted display (HMD) the pilot can be made aware of obstacles that are currently obscured by degraded visual conditions or even parts of the own helicopter. This can be accomplished in one HMD. No attention sharing between the outside view and a headdown instrument is necessary. DLR is continuously aiming at testing and evaluating both flight-proof and consumer grade HMDs. One particular widely known system is the Microsoft HoloLens. DLR will integrate this low-cost HMD into their test helicopter ACT/FHS. For this, as a first step a Microsoft HoloLens was integrated into DLR's simulator AVES. In this paper the integration process is detailed. The simulation capabilities are described, especially for conformal, open-loop Lidar sensor data. Furthermore, first concepts of the display format are shown, and strengths and drawbacks of the HoloLens in a cockpit environment are discussed.

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