Lars Ebrecht

Starting Model-Based Testing Based on Existing Test Cases Used for Model Creation

Model-based testing has a significant impact on test quality and test effort. However, many industrial projects still rely on the traditional testing methods. The biggest concerns against model-based testing are the need of formal knowledge and high initial costs for introducing the formal model. In this paper we show how it is possible to introduce model-based testing to a large scale industrial project by using the existing test cases as a basis for the model creation, thus effectively reducing concerns and efforts introducing the model-based testing approach. Additionally the created model can be used to simulate the reference behavior in an early development stage, resulting in a comprehensive prototype. The used context is a project in the railway industry domain, the European Train Control System, in which a lot of effort has been spent with the generation of high quality test cases.

Integration of a 3D perspective view in the navigation display: featuring pilot's mental model

Synthetic vision systems (SVS) appear as spreading technology in the avionic domain. Several studies prove enhanced situational awareness when using synthetic vision. Since the introduction of synthetic vision a steady change and evolution started concerning the primary flight display (PFD) and the navigation display (ND). The main improvements of the ND comprise the representation of colored ground proximity warning systems (EGPWS), weather radar, and TCAS information. Synthetic vision seems to offer high potential to further enhance cockpit display systems. Especially, concerning the current trend having a 3D perspective view in a SVS-PFD while leaving the navigational content as well as methods of interaction unchanged the question arouses if and how the gap between both displays might evolve to a serious problem. This issue becomes important in relation to the transition and combination of strategic and tactical flight guidance. Hence, pros and cons of 2D and 3D views generally as well as the gap between the egocentric perspective 3D view of the PFD and the exocentric 2D top and side view of the ND will be discussed. Further a concept for the integration of a 3D perspective view, i.e., bird’s eye view, in synthetic vision ND will be presented. The combination of 2D and 3D views in the ND enables a better correlation of the ND and the PFD. Additionally, this supports the building of pilot’s mental model. The authors believe it will improve the situational and spatial awareness. It might prove to further raise the safety margin when operating in mountainous areas.

Inverse Model Based Testing -- Generating Behavior Models from Abstract Test Cases

test cases contain a huge amount of domain specific knowledge of experts. Engineers may not use this knowledge only for validation purposes, e.g., applying test cases to software and hardware units, it can be also a starting point for modeling the product prototypically. This paper addresses the issue of generating a functional behavior model from abstract test cases. The test cases belong to the conformity and interoperability test standard for train-borne control units of the European Train Control System (ETCS). The contribution illustrates the approach and its advantages.

Integration of an Exocentric Orthogonal Coplanar 360 Degree Top View in a Head Worn See-Through Display Supporting Obstacle Awareness for Helicopter Operations

The objective was the development of an HMI for helicopter obstacle awareness and warning systems in order to improve the situational and spatial awareness as well as the workload of helicopter pilots. The related work concerning obstacle awareness and warning systems, situational awareness, orthogonal coplanar and perspective representations plus previous work done by DLR was depicted and discussed. The two main aspects of the developed HMI concept were explained, i.e., the combination of the exocentric orthogonal coplanar top view with the egocentric perspective view, and secondly three ways for the integration of the obstacle awareness display inside a head-worn see-through display. The developed HMI concept was applied to two helicopter offshore operations and its specific obstacle situation. The first operation is a hoist operation at the lower access point of an offshore wind turbine. The second regards the landing operation on an offshore platform. From a technical point of view, especially concerning available sensor technologies, helicopter might be fitted with obstacle awareness systems in future. The HMI design is still under investigation in order to support the pilot in a holistic and balanced way.

360 Degree Top View inside a Helmet Mounted Display providing Obstacle Awareness for Helicopter Operations

This paper introduces a display concept for helicopter obstacle awareness and warning systems. The key feature of the concept is the integration of a 360-degree coplanar orthogonal top view in the egocentric perspective of a helmet mounted see-through display. The concept intends to provide obstacle awareness while pilots are looking outside. The concept should further improve the situational and spatial awareness as well as the workload of helicopter pilots when operating in challenging surroundings. The display concept is applied to two helicopter off-shore operations and its specific obstacle situation. The first operation represents a hoist operation at the lower access point of an off-shore wind turbine. The second regards an off-shore platform landing operation. The paper depicts the two use cases, related work concerning obstacle awareness and warning systems, and recapitulates situational awareness plus the properties of orthogonal coplanar in comparison to the properties of perspective representations. Thereafter the two main aspects of the developed HMI concept were presented, i.e., the combination of the exocentric orthogonal coplanar top view with the egocentric perspective view, and secondly three ways for the integration of the top view inside the helmet mounted display. The implemented HMI design represents work in progress, i.e., looking forward to develop an optimal holistic and balanced display concept featuring helicopter obstacle awareness and warning systems.

Synthetic vision on a head-worn display supporting helicopter offshore operations

Helicopters play an important role during construction and operation of o shore wind farms. Most of the time helicopter offshore operations are conducted over open water and often in degraded visual environment. Such scenarios provide very few usable visual cues for the crew to safely pilot the aircraft. For instance, no landmarks exist for navigation and orientation is hindered by weather phenomena that reduce visibility and obscure the horizon. To overcome this problem, we are developing an external vision system which uses a non-see-through, head-worn display (HWD) to show fused sensor and database information about the surroundings. This paper focuses on one aspect of our system: the computer-generated representation of relevant visual cues of the water surface. Our motivation is to develop a synthetic view of the surroundings that is superior to the real out-the-window view. The moving water surface does not provide fixed references for orientation and sometimes even produces wrong motion cues. Thus, we replace it by a more valuable, computer-generated clear view. Since pilots estimate wind direction and speed by checking the movement characteristics of the water surface, our synthetic display also integrates this information. This paper presents several options for a synthetic vision display supporting offshore operations. Further, it comprises results from simulator trials, where helicopter pilots performed final approaches and landings on an offshore platform supported by our display. The results will contribute to the advancement of our HWD-based virtual cockpit concept. Additionally, our findings may be relevant to conventional, head-down synthetic vision displays visualizing offshore environments.

Designing a virtual cockpit for helicopter offshore operations

In recent years the number of offshore wind farms is rapidly increasing. Especially coastal European countries are building numerous offshore wind turbines in the Baltic, the North, and the Irish Sea. During both construction and operation of these wind farms, many specially-equipped helicopters are on duty. Due to their flexibility, their hover capability, and their higher speed compared to ships, these aircraft perform important tasks like helicopter emergency medical services (HEMS) as well as passenger and freight transfer flights. The missions often include specific challenges like platform landings or hoist operations to drop off workers onto wind turbines. However, adverse weather conditions frequently limit helicopter offshore operations. In such scenarios, the application of aircraft-mounted sensors and obstacle databases together with helmet-mounted displays (HMD) seems to offer great potential to improve the operational capabilities of the helicopters used. By displaying environmental information in a visual conformal manner, these systems mitigate the loss of visual reference to the surroundings. This helps the pilots to maintain proper situational awareness. This paper analyzes the specific challenges of helicopter offshore operations in wind parks by means of an online survey and a structured interview with pilots and operators. Further, the work presents how our previously introduced concept of an HMD-based virtual flight deck could enhance helicopter offshore missions. The advantages of this system – for instance its “see-through the airframe”-capability and its highly-flexible cockpit setup – enable us to design entirely novel pilot assistance systems. The gained knowledge will be used to develop a virtual cockpit that is tailor-made for helicopter offshore maneuvers

Route augmentation enhancing situational awareness and flight management

Synthetic vision systems (SVS) improved cockpit display systems a lot facing situational awareness and safety issues. Pilots get detailed comprehensive information timely during flight. Besides, cockpit display systems become more and more complex due to the fact that they increasingly provide various detailed information on smaller or larger display units. The pilot is in charge to manage and observe all the different flight relevant information. Upon terrain visualization weather data represent quite essential information concerning safety. Nearly every SVS provide weather information. Due to the dissimilarity of terrain and weather information the following contribution will discuss which representation might be the best for the one and the other. The intention behind is how the pilot may take greatest benefit from terrain and weather information in order to be aware of these aspects when necessary. This issue comprises the comparison of 2D and 3D views. Additionally, this contribution introduces a concept how flight relevant information, here weather data, might be related to the active route. This intends to provide an overview from where pilots can manage the indication of weather and terrain views for a proper situational awareness and flight management. The concept is depicted on the example of a curved approach in a mountainous region that is affected by emerging thunder storm.

Modulare Echtzeit-Testarchitektur

Der folgende Artikel stellt einen generischen Ansatz fur eine modulare Echtzeit-Testarchitektur vor. Anhand der im Bahnlabor RailSiTe®realisierten Test- und Simulationsumgebung wird vorgestellt, wie basierend auf plattform- und programmiersprachenunabhangigen Testbeschreibungen in Verbindung mit anwendungsspezifischen Hardware-Schnittstellenadapter ereignisdiskrete sowie kontinuierliche Signale generiert werden. Dieser Ansatz ermoglicht eine frei konfigurierbare und flexible Basisarchitektur fur Hardware-in-the-Loop-Tests. Das Prinzip wird exemplarisch an einem Hochfrequenzsignalubertragungskanal zur Eurobalisen- und Euroloop-Nachrichtenubertragung fur eine fahrzeugseitige Leit- und Sicherungseinheit verdeutlicht.

Das atomare Element als Meta-Modell zur tabellarischen Verhaltensbeschreibung von Echtzeitsystemen

Testen komplexer Funktionen sicherheitsgerichteter Echtzeitsysteme ist sehr aufwandig und kompliziert. In dem Beitrag wird eine tabellarische Verhaltensbeschreibung vorgestellt, die auf Basis des atomaren Elements, das Systemverhalten transparenter und besser verstandlich machen soll. Mit Hilfe des atomaren Elements als Meta-Modell kann das Verhalten nicht nur eindeutig, konsistent und genau beschrieben werden, vielmehr kann das Verhalten hierarchisch strukturiert,verfeinert und bzgl. verschiedener systemtechnischer Aspekte differenziert werden.