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Senast publicerade
- A Benchmarking-Based Framework for Energy Performance Variation Screening in Manufacturing Systems(2026) He, Jiana; Li, ZhuangEnergy data are increasingly available in manufacturing systems, but valid interpretation depends on production context that is often incomplete. This thesis develops a benchmarking-based framework for screening and classifying within-resource energy-performance variation under limited data conditions. The framework is applied to an industrial case using three datasets provided by Volvo Trucks: 30-minute device-level energy records, stop logs, and stop-detail records. The method integrates the datasets at a common resource–time-window level, constructs comparable active-like windows, establishes a local benchmark from historically lower-energy observations, and screens high benchmark-gap windows using the available stop information. Energy use per 30-minute window is treated as a screening variable rather than an output-normalised efficiency indicator. The application identifies distinct variation profiles across resources: some resources show larger relative gaps, whereas others show greater accumulated recorded energy above the local benchmark. Recorded stop events provide candidate explanations for only part of the flagged windows, demonstrating that richer data on output, product type, cycle time, shift, and machine state are required for causal diagnosis. The framework therefore supports transparent screening and prioritisation, but it does not by itself establish energy inefficiency, quantify savings potential, or confirm root causes.
- Fiber-based indoor testing of laser rangefinder extinction ratio(2026) Brink, LinusLaser rangefinders (LRFs) are one of the most prominent optronic systems used for both civilian and military applications. One way to characterize their performance is by measuring the extinction ratio (ER), defined as the attenuation at which the LRF detects 50% of the transmitted pulses. At Lumibird Photonics Sweden AB, the ER is currently determined using an outdoor over-the-air (OTA) test range, where the laser pulse is fired at a well-defined reference target. To eliminate the weather dependence inherent to outdoor OTA testing, this thesis investigates an indoor laboratory test bench using a single-mode fiber to guide the pulses as an alternative ER measurement method. The work focused on establishing stable free-space-to-fiber coupling, selecting a suitable baseline attenuation before fiber injection, and comparing the ER behavior with an OTA reference measurement. Using a deliberately larger focused beam at the fiber input reduced the influence of pulseto- pulse beam variations on the coupling efficiency. In addition, nonlinear propagation in the fiber was found to be the main limitation on the maximum usable coupled intensity, causing pulse distortion when it was too high. With suitable baseline attenuation, the final test bench produced a clear detection roll-off similar to the OTA reference. The test-bench ER was obtained at ≈ 101 dB of added attenuation, and the measured distance agreed with the expected fiber-delay distance within ≈ 1 %. Including estimated setup-specific losses, the same 50% detection point corresponded to a test-bench total attenuation of ≈ 110 dB, compared with ≈ 130 dB for the OTA reference, with the difference likely arising from idealized assumptions regarding losses in the test bench. Overall, the test bench shows potential as an indoor complement to OTA ER testing, but further characterization of losses, repeatability, and uncertainty is required before it can be used for final performance evaluation.
- Monte Carlo simulation of GaAs schottky barrier diodes for THz applications(2026) Lööv, XeniaAccurate models for GaAs Schottky barrier diodes are essential for implementing room-temperature mixers and frequency multipliers for use in the terahertz range. Increased electron temperatures by the Schottky contact and effects from intervalley scattering make traditional drift-diffusion methods unsuitable for simulating such devices. This work implements a Monte Carlo simulator based on a microscopic model for electron transport in GaAs. A three-valley (Γ,𝐿 and 𝑋) spherical non-parabolic band structure is assumed, and impurity, optical phonon and acoustic phonon scattering mechanisms are considered for the model. Homogeneous (bulk) transport properties of GaAs are simulated, showing good agreement with published values of mobility and diffusion coefficient versus field strengths, accurately predicting the critical field and saturation velocity for the carriers as they enter heavier valleys. The simulator is also used to simulate a number of Schottky barrier diodes fabricated at Chalmers University of Technology. The results show good agreement with the measured IV-characteristics, with the ideality factor being within 10% and saturation current within a factor of 3. The voltage-capacitance relationships agree well with the ideal diode model, the zero-voltage capacitance being within a few percent. The simulation shows an increased carrier temperature at the Schottky contact at higher currents, consistent with previous results, indicating an increased noise temperature at higher currents.