Doctoral School

Reading date: 05/02/2025

• SALAS I BARENYS, BERNAT: Precision Agriculture in Fruit Orchards: Development and Evaluation of a Smart Sprayer for Variable Rate Pesticide Application in 3D crops
  
  Author: SALAS I BARENYS, BERNAT
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AGRI-FOOD TECHNOLOGY AND BIOTECHNOLOGY
  Department: Department of Agri-Food Engineering and Biotechnology (DEAB)
  Mode: Article-based thesis
  Deposit date: 09/01/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: GIL MOYA, EMILIO | SALCEDO CIDONCHA, RAMON
  Committee:
       PRESIDENT: BAPTISTA, FÁTIMA DE JESUS FOLGÔA
       SECRETARI: CAMPOS TOBAJAS, JAVIER
       VOCAL: GIOELLI, FABRIZIO STEFANO
  Thesis abstract: European agriculture is currently experiencing an intense debate about the production model, linked to a growing social awareness regarding the use of agrochemicals in general, and plant protection products in particular. In this sense, there is a notable increasing focus on precision agriculture, which aims to optimize the use of these inputs by considering the intra-field variability among trees or plants. One example is the OPTIMA project (Optimised PesT Integrated MAnagement), funded by the EU under the H2020 program (http://optima-h2020.eu/en), within which this doctoral thesis has been developed. For the UMA-UPC research group, the goal was to design and integrate a novel system for applying plant protection products in a conventional hydropneumatic sprayer with constant flow for treatments in fruit trees. This system was designed to be able to adjust the amount of liquid sprayed based on the width and density of the tree canopies, thus avoiding excess or insufficient presence of pesticides on the target vegetation of the treatment. To achieve this, it uses a set of ultrasonic sensors to determine the size and leaf density of the canopy, sending this information to a computer that regulates a set of motorized valves to modify the flow rate in real time through the nozzles.With these premises, the present thesis encompasses, in the first part, the characterization of the sprayer, the design and implementation of the intelligent spraying system and the validation of the prototype conducted through field trials on apple applications. In these experiments, the coating and deposition of product on leaves were evaluated, both in terms of quantity and distribution uniformity, as well as the direct losses of plant protection product to the soil.The results of the sprayer characterization showed that the asymmetry of air velocities from the fan was accentuated as the airflow increased. Additionally, it was observed that the homogeneity of the coating on the tree canopies increased when working with larger droplet sizes along with higher airflow configurations in the fan. These results helped establish the configuration of the prototype during subsequent field trials (fan and nozzle parameters). Regarding the results of the second part, the prototype's ability to continuously modify the flow rate of the nozzles according to crop characteristics was successfully demonstrated, in terms of speed and precision level. The efficiency and robustness of the prototype and its components were successfully evaluated, including an in-depth analysis of the ultrasonic sensor configurations. All of this allowed for the selection of the appropriate configuration of both sensors and actuators as well as the parameters introduced into the algorithm for the final part of the thesis.The results obtained in this thesis demonstrate the success of the VRA system in achieving its fundamental objectives: reducing the volume of plant protection products applied and minimizing environmental impact. The intelligent spraying system allowed for a significant reduction of 45% in liquid use compared to conventional sprayers, maintaining optimal levels of leaf deposition. This optimization not only improves the efficiency of plant protection treatments but also reduces the direct losses of product to the soil, decreasing the risk of environmental contamination. Thus, the implementation of this technology contributes to more sustainable agriculture, aligning with the principles of the EU's Sustainable Use of Pesticides Directive and other regulatory frameworks that promote reducing dependence on chemical products in crop protection.
  

• VERA I FERNÁNDEZ, JORDI: Development of Algorithms for Enhancing Numerical Simulations in CFD & HT: Conjugate Heat Transfer, Moving Bodies, Indoor Air Quality, and Thermal Energy Storage
  
  Author: VERA I FERNÁNDEZ, JORDI
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN THERMAL ENGINEERING
  Department: Department of Heat Engines (MMT)
  Mode: Normal
  Deposit date: 09/01/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: OLIVA LLENA, ASENSIO | PEREZ SEGARRA, CARLOS DAVID
  Committee:
       PRESIDENT: CORTÉS GRACIA, CRISTÓBAL
       SECRETARI: TRIAS MIQUEL, FRANCESC XAVIER
       VOCAL: FERNÁNDEZ SEARA, JOSÉ
  Thesis abstract: This thesis consists of the enhancement of numerical simulations in CFD \& HT (Computational Fluid Dynamics and Heat Transfer). The contents are divided into three blocks: CFD numerical methods, indoor air quality, and thermal energy storage (TES).The first block focuses on simulation methods for moving bodies. A new approach is introduced to enhance Conjugate Heat Transfer (CHT) simulations using the Immersed Boundary Method (IBM). This algorithm uses a two-mesh system to eliminate numerical errors in the solid energy equation caused by convective schemes that transport the solid's temperature field when using a single mesh.For rotating bodies, the Sliding Mesh Method (SMM) is applied, and an improvement to the face intersection algorithm is proposed. Additionally, a comparison between the IBM and the SMM is made using both a reference case and a newly proposed testing case.The second block studies the infection probability and air quality in indoor domains using CFD tools. A new methodology based on the Wells-Riley model is proposed to assess infection risk. The novel approach assesses various scenarios by performing a permutation for all possible locations of both infectious and susceptible individuals, generating an infection probability matrix that helps identify airflow patterns with either positive or negative impacts on infection rates.Finally, the new methodology, along with other air quality studies, is applied in a practical case involving an urban bus.The third block presents an advanced numerical simulation of a structured thermocline thermal energy storage system integrated with Concentrated Solar Power (CSP) plants. This storage system employs a single-tank configuration with a packed bed of ceramic filler materials, featuring channels for circulation of the Heat Transfer Fluid (HTF), a molten salt, to reduce costs and enhance thermal performance.A detailed mathematical model is developed to solve the unsteady 3D heat equation within the solid domain, coupled with 1D models for the HTC flow. This numerical model is then used for a parametric study to assess the impacts of geometric configurations, operational conditions, and cycle durations on the system's performance.In addition to the previously mentioned sections, two appendixes are included. The first appendix is closely related to the third block, focusing on the design of an experimental unit to validate the numerical models presented in that section. It provides a detailed description of the necessary components, including their operational and functional conditions. Preliminary experimental tests are conducted to assess the compatibility of filler materials and the properties of molten salts.Certain components, such as the heat exchanger, are analyzed in more detail using the methodology outlined in the second appendix. This second appendix compares the results of different CHT methodologies, including a 1D coupled model and a multidimensional CFD approach, to evaluate the behavior of heat exchangers under both steady and transient conditions. A new heat exchanger design is proposed and analyzed using this methodology. Finally, an experimental setup for the proposed design has been developed and prepared for testing.
  

Reading date: 06/02/2025

• BENADOUDA IVARS, SALIM: Exploring dissipative systems with non-Hermitian modulations
  
  Author: BENADOUDA IVARS, SALIM
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 10/01/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: HERRERO SIMON, RAMON | STALIUNAS, KESTUTIS
  Committee:
       PRESIDENT: V. GUREVICH, SVETLANA
       SECRETARI: ARTIGAS GARCIA, DAVID
       VOCAL: MAS ARABÍ, CARLOS
  Thesis abstract: The aim of this thesis is to explore the effect of non-Hermitian potentials in different nonlinear systems. Specifically, in the different sections of this work we focus on the stabilisation of various states. We consider mainly two systems due to their universality: the Gizburg Landau and the Lugiato Lefever equations. Both models correspond to generalisations of the nonlinear Schrödinger equation. The Ginzburg-Landau equation represents the dissipative extension of physical systems with active media. It has been extensively studied and praised as a foundational model for phenomena such as turbulence, lasers or Bose Einstein condensates. In contrast, the Lugiato-Lefever equation addresses dissipative systems with lossy media, where energy is injected. Recently, this model has gained renewed attention due to its accurate representation of fields in micro-resonators and the rapid advancements in mastering their fabrication. Through analytical and numerical studies we investigate how introducing non-Hermitian potentials leads to the stabilisation of different coherent structures. For laser-like models that exhibit strong and persistent turbulence regimes, this approach results in an effective stabilisation and control of the system. In turn, for micro-resonators, the stabilisation of periodic structures uncovers a novel and hybrid formation mechanism for solitons.
  

• ZHANG, SHUANG: STATE ESTIMATION, DIAGNOSIS AND CONTROL USING SET-BASED APPROACHES FOR LPV SYSTEMS
  
  Author: ZHANG, SHUANG
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AUTOMATIC CONTROL, ROBOTICS AND VISION
  Department: Institute of Industrial and Control Engineering (IOC)
  Mode: Normal
  Deposit date: 10/01/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: PUIG CAYUELA, VICENÇ | IFQIR, SARA
  Committee:
       PRESIDENT: MAMMAR, SAID
       SECRETARI: NEJJARI AKHI-ELARAB, FATIHA
       VOCAL: COMBASTEL, CHRISTOPHE
  Thesis abstract: Considering that Linear Parameter-Varying (LPV) technique has beendemonstrated as an effective way to represent nonlinear systems, results concerning the design of observers and controllers in LPV framework have been widely studied.This thesis contributes to the state-of-the-art in the field of robust state estimation, fault diagnosis and control for LPV systems, particularly in the presence of processing disturbances and measurement noise. The research is motivated by the safety-critical systems, such as autonomous vehicles, which require reliable fault diagnosis schemes for detecting and identifying potential actuator/sensor faults under uncertainties, and control strategies that are able to handle both the uncertainties and faults to achieve optimal and reliable performance. State estimation plays a crucial role in both fault diagnosis and controller design. To ensure robust performance, a set-membership state estimation method is developed for LPV systems subject to disturbances and measurement noises. These uncertainties are assumed to be unknown but bounded by zonotopes. The optimal state estimates are obtained by minimizing the radius of the bounding zonotope, formulated as an optimization problem in the form of Linear Matrix Inequalities (LMIs). Furthermore, the proposed method is extended to handle fault detection and estimation in more complex scenarios, including switched LPV systems and Nonlinear Parameter-Varying (NLPV) systems. In addition, Minimum Detectable Fault (MDF) and Minimum Isolable Fault (MIF) are characterized using zonotopic set-invariance approach. In the area of control, this thesis develops a Linear Quadratic Zonotopic (LQZ) control for the state feedback problem in the presence of uncertainties, in which the feedback loop is closed using the optimal estimates provided by a Zonotopic Kalman Filter (ZKF). The proposed LQZ control is less conservative, as it models uncertainties using zonotopic sets rather than Gaussian probability distributions. This formulation establishes the LQZ control as a zonotopic counterpart to the well-known Linear Quadratic Gaussian (LQG) control. Furthermore, in the presence of actuator fault, a Fault Tolerant Tracking Control (FTTC) strategy is developed. This strategy comprises a ZKF for state and fault estimation, a fault compensation mechanism and a state-feedback controller designed to achieve $\mathscr{H}_\infty$ performance.The above-mentioned contributions have been applied to state estimation, fault diagnosis and path-tracking control in vehicle lateral dynamics. Application to real data recorded with a prototype equipped vehicle demonstrates the relevance and efficiency of the proposed approaches.
  

Reading date: 07/02/2025

• GONZÁLEZ ÁVALOS, RAÚL ALEXIS: High-Fidelity Modelling of Aquaculture Net Cages in Waves and Currents Using Smoothed Particle Hydrodynamics
  
  Author: GONZÁLEZ ÁVALOS, RAÚL ALEXIS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MARINE SCIENCES
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Article-based thesis
  Deposit date: 13/01/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ALTOMARE, CORRADO | GIRONELLA I COBOS, FRANCESC XAVIER
  Committee:
       PRESIDENT: CASTRO RODRÍGUEZ, MARIA TERESA
       SECRETARI: MARZEDDU, ANDREA
       VOCAL: ROMANO, ALESSANDRO
  Thesis abstract: As aquaculture expands into areas exposed to unfavourable climatic conditions, it becomes imperative to develop numerical models capable of predicting the behaviour of these systems under severe environmental scenarios. The complexity of aquaculture systems, which encompass nets, floating structures, and mooring lines, presents a significant challenge for traditional low- and medium-fidelity numerical approaches. These methods often rely on simplifying assumptions that are not applicable in such contexts. Modelling these systems in energetic seas necessitates solving multi-body problems subject to non-linear loads, wherein components such as nets undergo substantial deformations and exhibit non-linear behaviour. High-fidelity numerical models are therefore essential to accurately capture the intricate interactions between the fluid and the structuresThis thesis investigates the use of Computational Fluid Dynamics (CFD), based on the Smoothed Particle Hydrodynamics (SPH) method, as a high-fidelity tool for the numerical modelling of marine aquaculture systems in complex environmental settings. A methodology has been proposed and developed in which the net is represented as a set of fluid-driven elements connected through dynamic moorings. In this scheme, the particles that make up these elements interact directly with the particles that constitute the fluid, thereby establishing the fluid-structure interaction. This approach differs from other recent advances in the numerical modelling of these systems by integrating the net elements within the same simulation domain as the fluid, representing a significant advancement in the numerical modelling of these structures.This thesis is presented as a compendium of scientific articles organised into chapters, including conclusions and recommendations for future research. In Chapter 1, the context and relevance of the research problem are introduced. Chapter 2 presents the first article of the compendium, which describes the application and validation of the proposed methodology for the numerical modelling of aquaculture nets in currents. Chapter 3 includes the second article, which expands the approach by applying it to the modelling of an aquaculture cage with copper alloy nets at a 1:15 scale, subjected to current conditions representative of high-energy zones, and validates the results through comparison with experimental data. Chapter 4 presents a manuscript under review, which validates the modelling of the net cage under regular wave conditions and extends its application to a multi-component aquaculture system (cage and mooring system) subjected to the combined action of waves and currents. Finally, Chapter 5 presents the discussions and conclusions of this thesis. The results obtained demonstrate the effectiveness of the proposed approach as a high-fidelity tool for modelling aquaculture systems in challenging marine environments.