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On 19 September 2021, a strombolian volcanic eruption began on the island of La Palma in the Canary Islands. This event resulted in the destruction of 73 km of roads, urban infrastructure, numerous houses, and agricultural crops, affecting approximately 7200 people and causing losses exceeding 1.2 billion euros. Around 12 km2 were covered by aa and pahoehoe lava flows, which reached thicknesses of over 70 m. Following the end of the eruption, thermal, geological, and geotechnical site investigations were carried out for the reconstruction and territorial and urban planning, with the main objectives focused on opening roads through hot lava, constructing new urban settlements in areas covered by lava flows, and facilitating the agricultural recovery. The primary challenges to reconstruction included the very slow cooling rate of the lava, resulting in persistent high temperatures, exceeding 500 °C, its highly heterogeneous geotechnical properties with numerous cavities and lava caves, and the presence of toxic gases. Site investigations included geotechnical boreholes, seismic geophysics and ground-penetration radar, and temperature measurements of lava flows using drones and thermocouple devices inside boreholes. To estimate the cooling rates of the lava flows, two physical cooling models were developed based on thermal behavior and geological–geotechnical data. The results indicated that lava cooling durations in some areas exceed practical waiting times for commencing reconstruction. This led to the development of geological engineering solutions that permit road construction and urban and agricultural reconstruction to begin sooner than estimated by the cooling models. On the other hand, potential hazards arising from the eruption process have also been taken into account. Stability analyses of the 200 m high volcanic cone formed during the eruption indicate the possibility of failure in the event of heavy rain and consequently lahar hazards. The results of the investigations carried out and their applications to post-disaster reconstruction may be useful for other volcanic regions, contributing to minimizing risk to infrastructure and urban settlements. [ABSTRACT FROM AUTHOR]

In this paper, we propose the design of a robust control strategy for the trajectory tracking problem in perturbed unicycle mobile robots. The proposed strategy comprises the design of a robust control law, which is based on an Integral Sliding‐Mode Control (ISMC) approach together with an interval predictor‐based state‐feedback controller through a Model Predictive Control (MPC) scheme. The robust controller deals with some perturbations in the kinematic model, which represent slipping effects, and with state and input constraints that are related to restrictions on the workspace and saturated actuators, respectively. The proposed approach guarantees the exponential convergence to zero of the tracking error. The performance of the proposed approach is validated through some simulations tracking a lemniscate and a circumference curve. [ABSTRACT FROM AUTHOR]

Copyright of AIS: Ars Iuris Salmanticensis is the property of Ediciones Universidad de Salamanca and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: The purpose of this Special Issue on "Sliding–mode algorithms for state estimation and fault diagnosis" is to present a collection of articles showing novel developments and results in the theory and practice of sliding–mode algorithms for state estimation and fault diagnosis. This collection also includes some advanced and non–standard methods to deal with the fault–tolerant control problem. [ABSTRACT FROM AUTHOR]

Summary: In this paper a family of homogeneity–based observers is proposed to estimate the state of a class of multiple–outputs linear systems with some parametric uncertainties and unknown inputs. Such a family of observers possesses robustness, finite– and fixed–time convergence properties depending on the considered parametric uncertainties and unknown inputs. The structure of these observers is simple since requires neither additional observers, for an a priori stabilization, nor complex transformations, and allows us to straightforwardly apply the observers for the case of multiple–outputs. The proposed structure is based on relative degree sufficient conditions that imply the strong observability of the system. Some simulation results illustrate the performance of the proposed homogeneous observers. [ABSTRACT FROM AUTHOR]

Summary: This article contributes with a fault‐tolerant control (FTC) for uncertain systems under the effect of some possible time‐ and state‐dependent actuator faults and/or failures, and component faults, which are zero at the initial time. The proposed scheme is based on a continuous integral sliding‐mode control approach and a fixed control allocation technique. The integral sliding‐mode control strategy allows us to design a robust linear controller and a multivariable Super‐Twisting algorithm, which deals with the faults. The proposed scheme guarantees the fulfilment of an output regulation task, with an arbitrarily small regulation error, and does not require a fault diagnosis stage but full‐state availability. The performance of the proposed FTC is illustrated through some simulations on a benchmark B747 aircraft model. [ABSTRACT FROM AUTHOR]

In this article, a solution to the output tracking problem is proposed for linear systems affected by external disturbances. The proposed robust control approach has a discontinuous integral term that provides exact and finite‐time convergence to zero of the output tracking error in the presence of external disturbances. The proposed nonlinear controller is non‐homogeneous. A constructive method to compute the controller gains is provided in order to ensure the convergence to zero of the output tracking error. Some simulation results are presented in order to illustrate the feasibility of the proposed robust control approach. [ABSTRACT FROM AUTHOR]

In this article, an adaptive observer is designed for patients with Type 1 Diabetes Mellitus. The adaptive observer, synthesized using the so‐called Bergman's Minimal Model, simultaneously estimates the states and the parameter corresponding to the insulin‐independent glucose disappearance rate. The adaptive observer deals with parameter uncertainties, whereas the food intake is regarded as an external disturbance. The adaptive observer relies on intravenous glucose measurements. The state estimation error converges to a neighborhood of the origin despite the effects of the external disturbances and uncertainties, while the parameter estimation error converges in a fixed time to a neighborhood of the origin. The adaptive observer synthesis is given by a constructive method based on linear matrix inequalities. Simulation results show the feasibility of the proposed scheme. Moreover, the approach is validated in UVA/Padova metabolic simulator for ten in silico adult patients. [ABSTRACT FROM AUTHOR]

Stability problems in rock masses are one of the main causes of subsidence events in underground mining areas. Zaruma, in the South of Ecuador, is characterised by mineral wealth, in which 65% of the population depends directly on artisanal mining activity. However, mineral extraction, without technical considerations and in many cases illegal, has negatively impacted the stability of tunnels generated under the city's urban area, reporting subsidence events in recent years. The aim of this study is to geomechanically characterise the main gallery of the tourist mine "El Sexmo" using two classic methods of geomechanical classification for the configuration of a model that complies with the 3G's (geotourism, geoconservation, and geoeducation) and supports the culture of sustainability in all areas of the sector. The methodology consists of (i) a field study design, (ii) a geological–geomechanical survey of the rock mass of a tourist mine using rock mass rating (RMR) and the Q-Barton index, and (iii) establishing a 3G's model for sustainable development. The results reveal that 100% of the rock mass of the tourist mine presents a rock quality classified as "Fair" (class III) by the RMR method, while, via the Q-Barton method, 92.9% of the rock mass obtains a "Poor" rating, except for station S05, rated "Very Poor". Furthermore, the study proposes additional support measures for three specific stations based on Q-Barton assessments, including fibre-reinforced sprayed concrete and bolting and reinforced ribs of sprayed concrete, considering that the mine is more than 500 years old and maintains geological features for geoeducation in geotechnical mining. Technical and social problems demand an innovative strategy, which, in this work, focuses on the 3G's model based on the quintuple innovation helix to develop sustainable underground geotourism. [ABSTRACT FROM AUTHOR]

This article proposes a solution to the output regulation problem for uncertain linear systems with input saturation, state constraints, and external disturbances. The proposed robust control is composed of a linear and a nonlinear part. Each part of the control can be designed independently due to the use of an integral sliding‐mode control approach. The linear control, whose design is based on the barrier Lyapunov function and the attractive ellipsoid method, considers the input saturation, the state constraints, and the parameter uncertainties. The nonlinear part is based on an integral sliding‐mode control approach and it can compensate the effect of some matched disturbances. Also, a safe set where the system trajectories do not transgress the state constraints and input saturation, is provided. The proposed scheme guarantees asymptotic convergence to zero of the output regulation error coping with the system constraints and disturbances. A constructive and simple method, based on linear matrix inequalities, is proposed to compute the controller gains. Some simulation results illustrate the feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this article an active fault‐tolerant control (FTC) is developed for the tracking problem in a quad‐rotor under the effects of a rotor failure and external disturbances. Such a strategy is composed of a finite‐time sliding‐mode observer, which estimates the full state from the measurable output and identifies uniformly bounded and Lipschitz disturbances. The failure scenario is analyzed in order to identify how it affects the dynamics. It is assumed that the failure has been isolated. The FTC design is composed of PID and continuous high‐order sliding‐modes controllers that allow the yaw angular velocity to remain bounded and the position tracking to be achieved even in the presence of some external disturbances. The closed‐loop stability is formally proven. Numerical simulations show the performance of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This article contributes with a finite-time model reference adaptive control approach to solve the robust tracking problem for a class of disturbed scalar linear systems. A nonlinear continuous control law, composed of nonlinear adaptive gains, provides a finite-time rate of convergence. For the ideal case, that is, without external disturbances, the tracking and the parameter (ideal control gains) identification error converge to zero in a finite time. For the disturbed case, the tracking and the parameter identification error dynamics are finite-time input-to-state stable with respect to the external disturbance. The corresponding convergence proofs and the robustness analysis are based on a Lyapunov function approach, input-to-state stability theory, and homogeneity theory. Finally, simulation and experimental results show the feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

To evaluate root resorption of lower incisors and canines quantitatively in a group of patients who underwent orthodontic treatment with piezocision and/or a collagen reinforcement technique with a fully resorbable three-dimensional (3D) collagen xenograft matrix compared with a control group. The study sample of this secondary analysis consisted of 32 periodontally healthy patients with angle Class I malocclusion or mild Class II or III malocclusion and moderate irregularity index scores who underwent orthodontic treatment and had before (T0) and after treatment (T1) cone-beam computed tomography scans. Root resorption of lower incisors and canines was assessed quantitatively in the following four groups: the control group received orthodontic treatment without piezocision, experimental group 1 received orthodontic treatment with piezocision, experimental group 2 received orthodontic treatment with piezocision and a 3D collagen matrix, and experimental group 3 received orthodontic treatment with a 3D collagen matrix. An overall statistically significant decrease in root length from T0 to T1 for all groups was observed (P <.05). However, there was no significant difference among the groups in the amount of root length decrease from T0 to T1. Orthodontic treatment combined with piezocision does not increase the risk of root resorption of lower incisors and canines when compared with orthodontic treatment without acceleration techniques. More studies with larger samples should be undertaken to confirm these results. [ABSTRACT FROM AUTHOR]

In diabetes mellitus (DM) treatment, Continuous Glucose Monitoring (CGM) linked with insulin delivery becomes the main strategy to improve therapeutic outcomes and quality of patients' lives. However, Blood Glucose (BG) regulation with CGM is still hampered by limitations of algorithms and glucose sensors. Regarding sensor technology, current electrochemical glucose sensors do not capture the full spectrum of other physiological signals, i.e., lipids, amino acids or hormones, relaying the general body status. Regarding algorithms, variability between and within patients remains the main challenge for optimal BG regulation in closed-loop therapies. This work highlights the simulation benefits to test new sensing and control paradigms which address the previous shortcomings for Type 1 Diabetes (T1D) closed-loop therapies. The UVA/Padova T1DM Simulator is the core element here, which is a computer model of the human metabolic system based on glucose-insulin dynamics in T1D patients. That simulator is approved by the US Food and Drug Administration (FDA) as an alternative for pre-clinical testing of new devices and closed-loop algorithms. To overcome the limitation of standard glucose sensors, the concept of an islet-based biosensor, which could integrate multiple physiological signals through electrical activity measurement, is assessed here in a closed-loop insulin therapy. This investigation has been addressed by an interdisciplinary consortium, from endocrinology to biology, electrophysiology, bio-electronics and control theory. In parallel to the development of an islet-based closed-loop, it also investigates the benefits of robust control theory against the natural variability within a patient population. Using 4 meal scenarios, numerous simulation campaigns were conducted. The analysis of their results then introduces a discussion on the potential benefits of an Artificial Pancreas (AP) system associating the islet-based biosensor with robust algorithms. [ABSTRACT FROM AUTHOR]

In this paper, the problem of state estimation for a class of uncertain, and possibly unbounded, nonlinear systems is tackled. In order to deal with such a problem, a nonlinear observer is proposed based on a continuous homogeneous and Levant's nth order differentiators. The proposed nonlinear observer provides finite-time convergence and the observer synthesis is formulated in terms of some linear matrix inequalities (LMIs). Moreover, contrary to what the literature shows, the finite-time observer does not require any type of Bounded-Input Bounded-State (BIBS) condition. Some simulation results illustrate the effectiveness of the proposed finite-time observer applied to an unstable nonlinear system. [ABSTRACT FROM AUTHOR]

Copyright of Advocatus is the property of Universidad Libre Seccional Barranquilla and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Cuestiones de Filosofia is the property of Universidad Pedagogica y Tecnologica de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: This article deals with the problem of adaptive estimation, that is, the simultaneous estimation of the state and time‐varying parameters, in the presence of measurement noise and state disturbances, for a class of uncertain nonlinear systems. An adaptive observer is proposed based on a nonlinear time‐varying parameter identification algorithm and a sliding‐mode observer. The nonlinear time‐varying parameter identification algorithm provides a fixed‐time rate of convergence, to a neighborhood of the origin, while the sliding‐mode observer ensures ultimate boundedness for the state estimation error attenuating the effects of the external disturbances. Linear matrix inequalities are provided for the synthesis of the adaptive observer while the convergence proofs are given based on the Lyapunov and input‐to‐state stability theory. Finally, some simulation results show the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel computed voltage based control law for an omnidirectional wheeled mobile robot equipped with four mecanum wheels. First, the dynamical model for the mechanical part is originally introduced by means of the Euler-Lagrange formulation. The motion constraints are added to the dynamic model using the Lagrange multipliers. Then, the dynamic model is completed by incorporating the dynamics of the actuators. Therefore, the dynamical model input signals are the armature voltage of the motors. The control law requires only the feedback of position and velocity of the whole robot, unlike most controllers in the literature that also need wheel speed feedback. The position and velocity are obtained by means of a multicam vision system, so measurements from motor encoders are not needed. A high-order sliding modes differentiator is included to estimate linear and angular velocities in a finite time. A stability proof is presented by means of the direct Lyapunov method, and furthermore, an analysis about parametric uncertainties in the mechanical parameters is introduced. The experimental results validate the theoretical proposal and show the good performance of the approach. [ABSTRACT FROM AUTHOR]

The aim of this study is to design a robust output‐based control to regulate the output for a class of linear systems with input saturation and affected by parameter uncertainties and external disturbances. The proposed robust control approach is composed of a homogeneous observer and a linear control law. The design and convergence analysis of the homogeneous observer is based on the implicit Lyapunov function theorem guaranteeing the finite‐time convergence of the state estimation error to a neighbourhood of the origin. The linear control law, that uses the estimated states and takes into account the saturated input constraint, is designed based on the attractive ellipsoid method and a barrier Lyapunov function approach. The synthesis of the robust‐output based control is given in terms of linear matrix inequalities. Simulation results are presented to illustrate the feasibility of the proposed robust control approach. [ABSTRACT FROM AUTHOR]

Summary: In order to solve the state estimation problem for linear hybrid systems with periodic jumps and unknown inputs, some hybrid observers are proposed. The proposed observers admit a Luenberger‐like structure and the synthesis is given in terms of linear matrix inequalities (LMIs). Therefore, the proposed observer designs are completely constructive and provide some input‐to‐state stability properties with respect to unknown inputs. It is worth mentioning that the structure of the hybrid observers, as well as the structure of the LMIs, depends on some observability properties of the flow and jump dynamics, respectively. Then, in order to compensate the effect of the unknown inputs, a hybrid sliding‐mode observer is added to the Luenberger‐like observer structure, providing exponential convergence to zero of the state estimation error despite certain class of unknown inputs. The existence of the hybrid observers and the unknown input hybrid observer is guaranteed if and only if the hybrid system is observable and strongly observable, respectively. Some numerical examples illustrate the feasibility of the proposed estimation approach. [ABSTRACT FROM AUTHOR]

This paper deals with the robust tracking problem for a group of Quad-Rotors forming a time-varying geometric pattern, i.e. formation control, in the presence of external disturbances. Such a robust control strategy is able to deal with any formation scheme such that there exists a directed spanning tree from the leader agent to all other agents. The proposed output-control strategy is based on a Continuous Sliding-Mode Control (Continuous-SMC) approach which is composed of a Finite-Time Sliding-Mode Observer (FT-SMO) and hierarchical cascade Continuous-SMCs. It is assumed that only the positions and angles of each Quad-Rotor are available to measure. Despite the disturbances acting on all the Quad-Rotor dynamics, this control strategy provides uniform finite-time stability for the altitude and yaw angle tracking and formation errors, and uniform exponential stability for the forward and lateral tracking and formation errors. Moreover, four different types of Continuous-SMCs can be used in the proposed strategy. Numerical simulations illustrate the performance of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper is focused on solving the collision avoidance problem for a group of Quad-Rotors which are affected by external disturbances when they are moving in a horizontal plane by means of Repulsive Vector Fields (RVFs). The RVFs are included in an attractive potential function control strategy, that allows the Quad-Rotors to reach the desired position in a geometric pattern, together with a Continuous Sliding-Mode Control (C-SMC) strategy based on Sliding-Mode Observers (SMOs) that are used to estimate, in a finite-time, the linear and angular velocities, respectively. For this purpose, a parameter, which depends on the distance among the Quad-Rotors and their velocities, is designed in order to scale the RVFs properly. In this sense, the repulsion force will be proportional to the velocity and acceleration of the Quad-Rotor when it detects any obstacle. A RVF not properly scaled may result in a collision or a Quad-Rotor movement far away from its desired position. The combination between the C-SMC strategy, the SMOs, the attractive potential functions and the RVFs robustly solves the formation control and avoidance collision problem under the presence of disturbances. Numerical simulations illustrate the performance of the RVFs when the Quad-Rotors are in risk of collision. [ABSTRACT FROM AUTHOR]

This study presents an output-feedback controller for a cart-pole system via coupled sliding-mode algorithms. Due to the fact that this system is underactuated, a special type of sliding surface is employed instead of using a transformation to the regular form. Then, a continuous sliding-mode controller is designed using the super-twisting algorithm so that robustness of the control scheme is guaranteed. Since the proposed controller requires the knowledge of the velocities, a homogeneous slidingmode observer is introduced to estimate such velocities. Then, in order to improve the control effort, a variable gain supertwisting algorithm is also proposed. The closed-loop stability is also guaranteed by means of input-to-state stability properties and Lyapunov function approaches. All the results are validated by means of real-time experiments, providing also a comparison between the proposed controllers and a chattering attenuation approach. [ABSTRACT FROM AUTHOR]

This study presents an output‐feedback controller for a cart–pole system via coupled sliding‐mode algorithms. Due to the fact that this system is underactuated, a special type of sliding surface is employed instead of using a transformation to the regular form. Then, a continuous sliding‐mode controller is designed using the super‐twisting algorithm so that robustness of the control scheme is guaranteed. Since the proposed controller requires the knowledge of the velocities, a homogeneous sliding‐mode observer is introduced to estimate such velocities. Then, in order to improve the control effort, a variable gain super‐twisting algorithm is also proposed. The closed‐loop stability is also guaranteed by means of input‐to‐state stability properties and Lyapunov function approaches. All the results are validated by means of real‐time experiments, providing also a comparison between the proposed controllers and a chattering attenuation approach. [ABSTRACT FROM AUTHOR]

Robust output tracking control of Van der Pol oscillator is an important practical problem from an application point of view. Output feedback‐based robust tracking control strategies are proposed in this work for that purpose. First, a high‐order sliding‐mode observer is used to estimate the oscillator states from the measurable output and to identify some types of disturbances. Then, five different continuous sliding‐modes controllers (Continuous‐SMCs) are provided to robustly track a desired time‐varying trajectory, exponentially or in a finite time, for the Van der Pol oscillator despite the presence of external disturbances. The closed‐loop stability for each Continuous‐SMC is given based on input‐to‐state stability properties. Finally, experimental validations are also provided to show the feasibility of the proposed controllers in real time. [ABSTRACT FROM AUTHOR]

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This article provides a comparative study of four different second-order sliding-mode (SOSM) differentiators proposed in the literature, namely, standard higher-order sliding-mode (HOSM) differentiator, non-homogeneous HOSM differentiator, uniform robust exact differentiator and hybrid fixed-time differentiator. Based on sliding-mode principles, these differentiators can provide robust exact differentiation with finite/fixed-time convergence. First, a comprehensive summary of the different methods is provided. Then, the differentiators are applied experimentally to estimate the states of a Van der Pol oscillator. Through experiments, it is shown that the different differentiators outperformed a Kalman-like observer, high-gain differentiator and extended Kalman filter. Finally, some suggestions are provided on the selection of SOSM differentiators for various applications. [ABSTRACT FROM AUTHOR]

Copyright of Dimensión Empresarial is the property of Universidad Autonoma del Caribe, Departamento del Atlantico and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Dimensión Empresarial is the property of Universidad Autonoma del Caribe, Departamento del Atlantico and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Zaruma is host to the "El Sexmo" tourist mine, the galleries of which extend below the city, and its exploitation dates back to precolonial times. The mining boom created important development in the area, but informal mining also emerged causing environmental issues and safety problems. This study presents a qualitative and quantitative assessment of the "El Sexmo" Tourist Mine in the context of its potential as a tourism geosite and mining site. The methodological stages included: (i) The process and systematization of the general mine information and its surroundings; (ii) the assessment of the geological and mining interest of the mine, through GAM and Brilha method; and (iii) description and proposal of action strategies through Delphi analysis and a Strengths, Weaknesses, Opportunities, and Threats (SWOT) matrix. Based on the results of the quantitative evaluation, the high values in the educational, scientific, and tourist aspects of the two applied methodologies, show the mine as a potential geosite and mining site with added cultural value. In addition, the quantitative assessment in correspondence with the qualitative analysis, allowed to propose improvement strategies to take advantage of the geological resources and mining identity of the area, as an alternative that strengthens the infrastructure of the mine and consolidates the geotouristic development of the area. [ABSTRACT FROM AUTHOR]