Centro de Investigación en Tecnoloxías Intelixentes (CITIUS)http://hdl.handle.net/10347/29902024-03-23T04:44:33Z2024-03-23T04:44:33ZGlobal shutter CMOS vision sensors and event cameras for on‐chip dynamic informationJaklin, MarkoGarcía Lesta, DanielLópez Martínez, PaulaBrea Sánchez, Víctor Manuelhttp://hdl.handle.net/10347/332582024-03-22T01:02:51Z2024-01-01T00:00:00ZGlobal shutter CMOS vision sensors and event cameras for on‐chip dynamic information
Jaklin, Marko; García Lesta, Daniel; López Martínez, Paula; Brea Sánchez, Víctor Manuel
The on-chip extraction of dynamic information from a scene can be addressed with either frame-based CMOS vision, also called smart image sensors, or dynamic vision sensors, also known as event cameras. When implemented with a pinned photodiode (PPD) as a 4-transistor active pixel sensor (4T-APS), the former brings about the benefits of low temporal noise and dark current but without high dynamic range (HDR). The latter comes with the benefits of HDR and a fast event detection rate with low power consumption. The drawback is the background activity noise, which leads to additional hardware or algorithms to keep it low. This paperanalyses the mismatch and noise of a global shutter 4T-APS implementation with local HDR through an overflow capacitor and correlated double sampling (CDS) to provide low noise events through frame differencing. The aim is to narrow the gap with dynamic vision sensors in terms of event rate and dynamic range. We show that our solution would be competitive with event cameras in scenarios with slow moving objects and a relatively wide dynamic range (85 dB).
2024-01-01T00:00:00ZSimultaneous Multifrequency Demodulation for Single-Shot Multiple-Path ToF ImagingShahandashti, Peyman FayyazLópez Martínez, PaulaBrea Sánchez, Víctor ManuelGarcía Lesta, DanielHeredia Conde, Miguelhttp://hdl.handle.net/10347/332462024-03-21T09:21:41Z2024-01-01T00:00:00ZSimultaneous Multifrequency Demodulation for Single-Shot Multiple-Path ToF Imaging
Shahandashti, Peyman Fayyaz; López Martínez, Paula; Brea Sánchez, Víctor Manuel; García Lesta, Daniel; Heredia Conde, Miguel
Indirect Time-of-Flight (iToF) sensors measure the received signal's phase shift or time delay to calculate depth. In realistic conditions, however, recovering depth is challenging as reflections from secondary scattering areas or translucent objects may interfere with the direct reflection, resulting in inaccurate 3D estimates. We propose a new measurement concept including a single-shot on-chip multifrequency demodulation method with periodically-repeated ultrashort-pulsed illumination using a novel pixel array architecture to address a main limitation of conventional iToF, the Multi-Path Interference (MPI). Due to the careful hardware/software codesign, the proposed single-shot architecture provides close-to-optimal Fourier measurements to a spectral estimation algorithm that retrieves the unknown parameters of the interfering return paths in a closed form. Electrical simulations of the on-chip multifrequency demodulation circuit demonstrate the feasibility of distance retrieval in double and triple bounce conditions in a single shot with high accuracy. Furthermore, we propose a set of methods for processing the resulting sensor measurements that exploit valuable a priori information and structural constraints of the data and observe that they yield a substantial increase in accuracy
2024-01-01T00:00:00ZMaximum output power point tracking for photovoltaic energy harvesting systems: Mathematical model and circuit implementationVicente García, LauraPereira Rial, ÓscarLópèz Martínez, Paulahttp://hdl.handle.net/10347/329322024-03-21T09:21:43Z2023-01-01T00:00:00ZMaximum output power point tracking for photovoltaic energy harvesting systems: Mathematical model and circuit implementation
Vicente García, Laura; Pereira Rial, Óscar; Lópèz Martínez, Paula
Maximizing the power transferred to the load is a key feature in any energy harvesting system. Contrary to traditional approaches, this paper mathematically demonstrates that performing a maximum power point tracking on the power delivered to the load instead of on the photogenerated power allows to harvest up to 25% more power due to setting less demanding operating conditions. A circuit implementation of a system that successfully maximizes its output by exclusively taking measurements of the output voltage is designed and demonstrated using a 180 nm commercial CMOS process. The system operates at μW range and achieves a peak power conversion efficiency of 79.04% at 30.74 μW output
2023-01-01T00:00:00ZREACH: Researching Efficient Alignment-based Conformance CheckingCasas-Ramos, JacoboMucientes, ManuelLama Penín, Manuelhttp://hdl.handle.net/10347/329312024-03-21T09:21:42Z2024-01-01T00:00:00ZREACH: Researching Efficient Alignment-based Conformance Checking
Casas-Ramos, Jacobo; Mucientes, Manuel; Lama Penín, Manuel
Conformance checking techniques compare how a process is supposed to be executed according to a model with how it is executed in reality according to an event log. Alignment-based approaches are the most successful solutions for conformance checking. Optimal alignments are a way of finding the best match between the real and the modeled behavior and identifying the differences. However, finding these optimal alignments is a challenging task, especially for complex cases where the log and the model have many events and paths. The difficulty lies in the computational complexity required to find these alignments. To address this problem, we propose an efficient algorithm named REACH based on the A* search algorithm. The core components of the proposal are the use of a partial reachability graph for faster execution of process models for alignment computation and a set of optimization techniques for reducing the number of states explored by the A* algorithm. These improve performance by both reducing the required computation time per state and the number of states to process respectively. To evaluate the performance and scalability, we conducted tests using 227 pairs of logs and models, comparing the results obtained with those from 10 state-of-the-art approaches. Results show that REACH outperforms the other proposals in runtimes, and even aligns logs and models that no other algorithm is able to align.
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