Showing papers by "Saab AB published in 2021"

Software product-line evaluation in the large

Abstract: Software product-line engineering is arguably one of the most successful methods for establishing large portfolios of software variants in an application domain. However, despite the benefits, establishing a product line requires substantial upfront investments into a software platform with a proper product-line architecture, into new software-engineering processes (domain engineering and application engineering), into business strategies with commercially successful product-line visions and financial planning, as well as into re-organization of development teams. Moreover, establishing a full-fledged product line is not always possible or desired, and thus organizations often adopt product-line engineering only to an extent that deemed necessary or was possible. However, understanding the current state of adoption, namely, the maturity or performance of product-line engineering in an organization, is challenging, while being crucial to steer investments. To this end, several measurement methods have been proposed in the literature, with the most prominent one being the Family Evaluation Framework (FEF), introduced almost two decades ago. Unfortunately, applying it is not straightforward, and the benefits of using it have not been assessed so far. We present an experience report of applying the FEF to nine medium- to large-scale product lines in the avionics domain. We discuss how we tailored and executed the FEF, together with the relevant adaptations and extensions we needed to perform. Specifically, we elicited the data for the FEF assessment with 27 interviews over a period of 11 months. We discuss experiences and assess the benefits of using the FEF, aiming at helping other organizations assessing their practices for engineering their portfolios of software variants.

Bandpass Filter With Tunable/Switchable In-Band Interference Rejection

Abstract: This letter presents a wideband bandpass filter (BPF) with a tunable and switchable in-band notch. This allows the RF front end to pass the signal of interest uninterrupted in the absence of an in-band interferer and reject part of the passband in case a narrowband interferer exists. The BPF is based on a two-path architecture, loaded with resonators on one of the paths to deliver an absorptive notch. The resonators are tuned with varactor diodes and are deactivated when the diodes are in forward bias. The implemented proof-of-concept hardware operates in the 4.8–7.8-GHz frequency range, with an in-band notch tunable between 5 and 6.25 GHz, when activated. The transmission lines were implemented as striplines, resulting in a measured insertion loss of 0.6 dB.

In-situ growth of cerium nanoparticles for chrome-free, corrosion resistant anodic coatings

Abstract: Chrome-based anodization and sealing combined is a cost-effective solution for developing good corrosion protective coatings on aluminum (Al) and its alloys The toxicity of hexavalent chromium, however, requires new, sustainable, environmentally friendly, and efficient chromate-free sealing procedures Herein, a combination of cerium (Ce) sealing and hydrothermal sealing (HTS) is employed to improve the corrosion resistance of the commonly used alloy AA2024-T3 anodized by tartaric sulfuric acid (TSA) The morphologies and components of the resulting surfaces are systematically studied Characterization technologies such as SEM, TEM, EDX, XRD, and XPS demonstrate the in-situ growth of Ce oxide nanoparticles all through the porous structures of the anodic coating and closing of the pores by additional HTS treatment The results from the standardized corrosion test (ASTM B895) demonstrate an improved corrosion resistance obtained by the utilized chrome-free process

Moisture effect on shape distortions of curved quasi-isotropic prepreg composite laminates

Abstract: The influence from moisture on shape distortion of curved thermoset composite laminates is investigated experimentally. The objects of study are L-shaped carbon/epoxy specimens with a quasi-isotropic layup and a thickness varying between 1 and 12 mm. The effect on the shape distortion is quantified by means of angle measurements vs. accelerated moisture uptake utilising a climate chamber at 90 °C and 95% relative humidity. The results show a strong dependence from laminate moisture content – the effect is in fact in the same order of magnitude as the spring-in from thermal and chemical shrinkage during curing. Moisture does thus not only affect the spring-in angle but also has to be taken into consideration, and be carefully controlled, when assessing shape distortions due to other parameters. Finally, a closed form expression based on the experimental results is presented, predicting how the bracket angle varies with the specimen thickness and moisture content.

Instinctual Interference-Adaptive Low-Power Receiver With Combined Feedforward and Feedback Control

Abstract: Highly adaptive, instinctively interference-tolerant radio frequency (RF) receivers are in high demand today. To achieve high-interference robustness at low average power, receivers need to be dynamically configured to operate in low-power mode in the absence of interference and a high-power interference-tolerant mode as an “instinctual” response to the blocker. In this letter, we present an interference-adaptive receiver with a control loop and on-board commercial off-the-shelf (COTS) components that adapt a 2–6-GHz low-noise amplifier (LNA) from a low-power mode (−10-dBm $P_{\text {1 dB,IN}}$ and $\approx 280$ -mW power) to high-linearity mode (1.5-dBm $P_{\text {1 dB,IN}}$ and $\approx 1.4$ -W power) where the linearity is increased by 11.5 dB ( $> 14\times $ ) with a $5\times $ increase in consumed power. With no interference, the control loop automatically brings the LNA back to the low-power mode.

A matheuristic approach to large-scale avionic scheduling

Abstract: Pre-runtime scheduling of avionic systems is used to ensure that the systems provide the desired functionality at the correct time. This paper considers scheduling of an integrated modular avionic system which from a more general perspective can be seen as a multiprocessor scheduling problem that includes a communication network. The addressed system is practically relevant and the computational evaluations are made on large-scale instances developed together with the industrial partner Saab. A subset of the instances is made publicly available. Our contribution is a matheuristic for solving these large-scale instances and it is obtained by improving the model formulations used in a previously suggested constraint generation procedure and by including an adaptive large neighbourhood search to extend it into a matheuristic. Characteristics of our adaptive large neighbourhood search are that it is made over both discrete and continuous variables and that it needs to balance the search for feasibility and profitable objective value. The repair operation is to apply a mixed-integer programming solver on a model where most of the constraints are treated as soft and a violation of them is instead penalised in the objective function. The largest solved instance, with respect to the number of tasks, has 54,731 tasks and 2530 communication messages.

A Wide Scanning Array of Connected Bowtie Antennas Suitable for Integration in Composite Sandwich Structures With Monte-Carlo Tolerance Analysis

Abstract: A low-profile and wide-scan phased-array antenna of connected cross-bowtie elements is proposed. The design goals and considerations are based on the applications requiring the integration of a large array antenna with composite sandwich structures, such as antennas on aircraft. In a very large array environment (modelled approximately as an infinite array), the main beam of the proposed antenna can be steered up to ±75° at azimuth and ±15° at elevation over bandwidths of 10% and 25% with active reflection coefficients below −10 dB and −5 dB, respectively. A Monte Carlo analysis of critical manufacturing and alignment tolerances shows the desired performance is achieved with the cumulative distribution probability over 80% under the uniformly distributed random combinations of the tolerances. Experimental results of a $7\times 7$ element array prototype agree well with the simulations of this small-scale array case. The experiments show that this small-scale prototype is capable of steering the beam within the range of [−60°, 60°] at azimuth and [−15°, 15°] at elevation with the predicted performance satisfying the targeted application requirements and mechanical constraints. The achieved combination of the wide beam steering performance, relatively low antenna profile, and suitability of its feeding structure for sandwiched electro-mechanical integration makes this design unique with respect to the previously published results.

Fatigue Response Dependence of Thickness Measurement Methods for Additively Manufactured E-PBF Ti-6Al-4 V

Abstract: Light weight metal parts produced with additive manufacturing have gained increasing interest from the aerospace industry in recent years. However, light weight parts often require thin walls which ...

Time Budget Management in Multifunction Radars Using Reinforcement Learning

Abstract: An adaptive revisit interval selection (RIS) in multifunction radars is an integral part of efficient time budget management (TBM). In this paper, the RIS problem is formulated as a Markov decision process (MDP) with unknown state transition probabilities and reward distributions. A reward function is proposed to minimize the tracking load (TL) while maintaining the track loss probability (TLP) at a tolerable level. The reinforcement learning (RL) problem is solved using the Q-learning algorithm with an epsilon-greedy policy. Compared to a baseline algorithm, the RL approach was capable of maintaining the tracks while reducing the tracking load significantly.

Vacuum-Assisted Hot-Forming Using Tailored Laminate Temperature

Abstract: A non-isothermal vacuum assisted hot-forming process using tailored laminate temperature is introduced. By using process simulation and manufacturing experiments, improved laminate quality is achieved compared to the standard hot-forming process. Furthermore, it is also shown that the manufacturing time in the clean room can be reduced to one tenth of the standard process time. In this study 8.4 mm thick quasi-isotropic laminates from unidirectional prepreg were laid up flat with an automatic tape laying machine and hot-formed to a U-shaped laminate. The laminates were then cured in a concave mould with standard bag on the inside. A complete tailored temperature hot-forming cycle of 7.5 min produced a very good final laminate quality with a total thickness variation as low as 4.0% and without wrinkles or indications of porosity. With a 4 min hot-forming cycle the thickness variation was also acceptable at 8%.

The MaLET Model — Maturity Levels for Exploratory Testing

Abstract: Based on multiple series of interviews and workshops, this paper presents the MaLET model – a representation of the typical evolution path for companies who successfully adopt exploratory testing. The model provides a step-by-step approach to systematically improve exploratory testing over time, and shows how and why capabilities may regress. The MaLET model was validated through a series of interviews with 20 interviewees from eight case study companies in separate industry segments. The interviews also revealed examples on improvement initiatives that had failed in the companies, showing that improvement initiatives tend to fail if they are not planned in an order corresponding to the maturity levels in the model. The MaLET model was well received by the interviewees during the validation, describing the model as sound, relevant and useful in practice.

Won’t Somebody Please Think of the Tests? A Grounded Theory Approach to Industry Challenges in Continuous Practices

Abstract: Continuous integration and delivery are well-established paradigms in the software development community. With these continuous practices come many challenges; while some of these challenges are immediate and well documented in literature, others may be revealed only after sustained application of these practices in large-scale and complex contexts. Based on researcher observations and interviews with 22 senior professionals from four companies, all with significant but varied experiences of continuous practices, we present a set of underreported challenges with continuous practices observed in multiple industry settings. Through a grounded theory approach we construct the Tapco model — Test Automation Progression in Continuous Practices — identifying two distinct ways in which companies progress towards continuous delivery, onto which the studied cases are mapped. This model is then validated by presenting it to the four studied companies, operating in disparate industry segments, and to three additional industry cases, letting them evaluate its relevancy, accuracy and novelty. We find that the model provides industry professionals with essential guidance on how to avoid common pitfalls, as well as an understanding of their causes and possible remediation.

ForSyDe-Atom: Taming Complexity in Cyber Physical System Design with Layers

Abstract: We present ForSyDe-Atom, a formal framework intended as an entry point for disciplined design of complex cyber-physical systems. This framework provides a set of rules for combining several domain-specific languages as structured, enclosing layers to orthogonalize the many aspects of system behavior, yet study their interaction in tandem. We define four layers: one for capturing timed interactions in heterogeneous systems, one for structured parallelism, one for modeling uncertainty, and one for describing component properties. This framework enables a systematic exploitation of design properties in a design flow by facilitating the stepwise projection of certain layers of interest, the isolated analysis and refinement on projections, and the seamless reconstruction of a system model by virtue of orthogonalization. We demonstrate the capabilities of this approach by providing a compact yet expressive model of an active electronically scanned array antenna and signal processing chain, simulate it, validate its conformity with the design specifications, refine it, synthesize a sub-system to VHDL and sequential code, and co-simulate the generated artifacts.

Analysis and Design of an 1-20 GHz Track and Hold Circuit

Abstract: This work analyzes the nonlinear effects in the track and hold circuit applied in high-speed ADCs or RF sampling receiver (RX) front-ends. Non-ideal effects inside the main sampling NMOS switch are studied. Parasitic varactor and sampling on-resistance modulation effects are analyzed through frequency domain Volterra series and the EKV MOS transistor model. Polynomial curve fitting is applied showing that the on-resistance modulation dominates. Finally, a novel bootstrap circuit is proposed with a fast settling time and high bootstrap voltage in a 22 nm FD-SOI CMOS technology, with its settling time analyzed using the Elmore delay model.