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http://hdl.handle.net/10174/903
2024-03-29T16:00:29ZAgent-based hybrid tabu-search heuristic for dynamic scheduling
http://hdl.handle.net/10174/36236
Title: Agent-based hybrid tabu-search heuristic for dynamic scheduling
Authors: Figueiredo, Joao; Firme, B.; Sousa, J.; Vieira, S.
Editors: ELSEVIER
Abstract: Dynamic scheduling has received widespread attention from academia and industry due to the increasing complexity in manufacturing systems. Highly dynamic and adaptable behaviours are necessary for an improved production efficiency in unstable and constantly changing environments. This paper proposes an agent-based hybrid tabu-search heuristic (AB-TSH) to solve dynamic flexible job-shop scheduling problems. The solution is fully implemented and tested in an industrial environment for seven distinct dynamic scenarios derived from a static scenario using the benchmark of AIP-PRIMECA Flexible Manufacturing System. The scheduling plan is obtained by exploitation using a greedy heuristic on tabu search solution points. The hybrid tabusearch heuristic is supported by a multi-agent system that react and re-optimize the scheduling plan in case of disturbances and unpredicted events. The proposed solution demonstrated superior performance in terms of makespan in the majority of dynamic scenarios tested when compared to previous studies in the literature. This improved performance is attributed to the solution’s ability to combine the scheduling plan both statically and dynamically.2023-01-01T00:00:00ZMinimizing total completion time in large-sized pharmaceutical quality control scheduling
http://hdl.handle.net/10174/36235
Title: Minimizing total completion time in large-sized pharmaceutical quality control scheduling
Authors: Figueiredo, Joao; Martins, M.; Viegas, J.; Coito, T.; Firme, B.; Costigliola, A.; Vieira, S.; Sousa, J.
Editors: SPRINGER
Abstract: This paper proposes an algorithm for the effective scheduling of analytical chemistry tests in the context of quality control for pharmaceutical manufacturing. The problem is formulated as an extension of a dual resource constrained flexible job shop scheduling problem for the allocation of both machines and analysts resources for analytical laboratory work of real dimensions. The formulation is novel and custom made to fit real quality control laboratory. The novelty comes from allowing multiple analyst interventions for each machine allocation while minimising the total completion time, formulated as a mixed integer linear programming model. A three-level dynamic heuristic is proposed to solve the problem efficiently for instances representative of real world schedules. The CPLEX solver and a Tabu Search algorithm are used for comparison. Results show that the heuristic is competitive with the other strategies for medium-sized instances while outperforming them for large-sized instances. The dynamic heuristic runs in a very short amount of time, making it suitable for real world environments. This work is valuable for the development of laboratory management solutions for quality control as it presents a way to provide automatic scheduling of resources.2023-01-01T00:00:00ZLow-Cost Multi-Frequency Eddy Current Coating Thickness Measurement System
http://hdl.handle.net/10174/33712
Title: Low-Cost Multi-Frequency Eddy Current Coating Thickness Measurement System
Authors: Santos, Ana C.; Barrancos, André; Rosado, Luís S.; Janeiro, Fernando M.
Abstract: A low-cost coating thickness gauge based on Eddy Current Testing (ECT) is reported in this paper. This measurement system employs a Direct Digital Synthesizer (DDS) to generate pure sinusoidal stimulus applied to a measurement coil whose impedance varies with the measured coating thickness. The coil current and voltage are digitally acquired using an ARM Cortex M4F microcontroller where sine-fitting digital signal processing algorithms are applied to estimate the coil inductance and resistivity at different operation frequencies. Post-processing implements a simple multi-frequency estimate algorithm providing accuracy improvements around 10% when compared with the use of a single frequency.2022-06-30T23:00:00ZImplementation of Goertzel Based Frequency Estimation for Power Quality Monitoring in Embedded Measurement Systems
http://hdl.handle.net/10174/33709
Title: Implementation of Goertzel Based Frequency Estimation for Power Quality Monitoring in Embedded Measurement Systems
Authors: Rodrigues, Nuno M.; Janeiro, Fernando M.; Ramos, Pedro M.
Abstract: International standards from IEC and IEEE regulate power grid parameters such as the RMS value, frequency, harmonic and interharmonic distortion, unbalance or the presence of transients, that are important to assure the quality of distributed power. Standard IEC 61000-4-30 suggests the zero crossing algorithm for the measurement of the power grid frequency, but also states that different algorithms can be used.
This paper proposes a new algorithm, the Fractional Interpolated Discrete Fourier Transform, FracIpDFT, to estimate the power grid frequency, suitable for implementation in resource limited embedded measurement
systems. It is based on the non-integer Goertzel algorithm followed by interpolation at non-integer multiples of the DFT frequency resolution. The proposed algorithm is validated and its performance compared with
other algorithms through numerical simulations. Implementation details of the FracIpDFT in an ARM Cortex M4 processor are presented along with frequency measurement results performed with the proposed algorithm in the developed system.2022-09-29T23:00:00Z