Leonardo Acho - Academia.edu (original) (raw)
Papers by Leonardo Acho
Mechanical Systems and Signal Processing, 2011
Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de ... more Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de la versió author's final draft d'un article publicat a la revista Mechanical Systems and Signal Processing.
Apple Academic Press eBooks, Feb 6, 2014
This paper considers power generation control in variable-speed variable-pitch horizontal-axis wi... more This paper considers power generation control in variable-speed variable-pitch horizontal-axis wind turbines operating at high wind speeds. A dynamic chattering torque control and a proportional integral (PI) pitch control strategy are proposed and validated using the National Renewable Energy Laboratory wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. Validation results show that the proposed controllers are effective for power regulation and demonstrate high-performances for all other state variables (turbine and generator rotational speeds; and smooth and adequate evolution of the control variables) for turbulent wind conditions. To highlight the improvements of the provided method, the proposed controllers are compared to relevant previously published studies.
This work is concerned with active vibration mitigation in wind turbines (WT) but not through the... more This work is concerned with active vibration mitigation in wind turbines (WT) but not through the use of specifically tailored devices. Instead, a general control scheme is designed for torque and pitch controllers based on a super-twisting algorithm, which uses additional feedback of the fore-aft and side-to-side acceleration signals at the top of the WT tower to mitigate the vibrational behavior. In general, proposed methods to improve damping through pitch and torque control suffer from increased blade pitch actuator usage. However, in this work the blade pitch angle is smoothed leading to a decrease of the pitch actuator effort, among other benefits evidenced through numerical experiments. The most frequent faults induce vibrations in the corresponding WT subsystems. In fact, vibration monitoring has been recently used for fault diagnosis Thus, by means of vibration mitigation, different faulty conditions can be alleviated leading to a passive fault tolerant control. In this work, coupled non-linear aero-hydroservo-elastic simulations of a floating offshore wind turbine are carried out for one of the most common pitch actuator faults.
A second-order LuGre friction model is presented which can be viewed as an extension of the well ... more A second-order LuGre friction model is presented which can be viewed as an extension of the well known LuGre friction model. This model is based on a dynamic extension, which can be seen as an extra dynamic to capture some kind of periodic motion produced by the bristles in motion. The additional dynamic can be viewed as an internal disturbance due to the vibration associated with the use of motors. Our model can capture the friction phenomena of the original LuGre friction model and presents two new behaviors, one is the multi-loop behavior in the hysteresis curve when velocity is varied during unidirectional motion, and the other, in the presliding motion curve of friction force versus displacement in the spring regime, where two jumps appear.
Mathematical Problems in Engineering, Feb 12, 2021
e main contribution of this paper is the proposal of a recent hysteresis dynamic model which is s... more e main contribution of this paper is the proposal of a recent hysteresis dynamic model which is successfully employed within a posited signal modulator. e modulation of signals is a commonly required stage in many engineering applications, such as telecommunications, power electronics, and control, among others. In this paper, the effectiveness of a signal modulator based on the well-known Delta modulator when it contains a dynamic hysteresis system within its main structure is presented. To do that, it is resorted to an application of the granted Hysteresis-Delta Modulator. is application consists of including the modulator within an adaptive scheme, since it is well known that the persistent excitation condition is required, for instance, in parameter estimation tasks. Hence, the main functional property of the modulator with hysteresis is its ability of producing a modulated signal with uniform high-frequency content even when its input is not a permanent persistent excitation signal. To highlight the main contribution of this paper, a numerical experiment of a parameter estimation system is developed to compare the performance of the modulator with the proposed hysteresis model and two other previously reported hysteresis systems. at is, three different scenarios have been tested in the parameter estimation of a nonminimum phase system. Finally, the numerical experiments confirm that the proposed hysteresis model along with the modulator provides the best performance as expected.
Machines, Jul 14, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper describes how to construct a low-cost magnetic levitation system (MagLev). 1 The MagLe... more This paper describes how to construct a low-cost magnetic levitation system (MagLev). 1 The MagLev has been intensively used in the engineering education, allowing instructors and 2 students to learn through hands-on experiments essential concepts, such as electronics, electromag-3 netism, and control systems. Built from scratch, the proposed MagLev depends only on simple, 4 low-cost components readily available on the market. In addition to showing how to construct 5 the MagLev, this paper presents a semi-active control strategy which seems novel when applied 6 in the MagLev. Experiments performed in the laboratory have compared the proposed control 7 scheme with the classical PID control. The corresponding real-time experiments illustrate both the 8 effectiveness of the approach and the potential of the MagLev for education.
IFAC Proceedings Volumes, Dec 1, 2004
Orbital stabilization of a simple underactuted manipulator, namely, two-link PENDUlum roBaf is un... more Orbital stabilization of a simple underactuted manipulator, namely, two-link PENDUlum roBaf is under study. Since underactuated systems can not be locally stabilized by means of smooth feedback, the solution to the stabilization problem is sought within switched control methods. The quasihomogeneity-based synthesis is applied to design a switched controller that drives the PENDUBaf to its zero dynamics in finite time and maintains it there in sliding mode. The constructed controller is such that the pendubot zero dynamics is generated by a modified Van der Pol oscillator,. being viewed as the reference model. The proposed Van der Pol modification aims to enlarge the region of attraction of the zero dynamics while also exhibiting a desired stable periodic behavior. Performance issues of the controller constructed are illustrated in a simulation study.
IFAC Proceedings Volumes, 2011
Hysteresis is a property of systems that do not instantly follow the forces applied to them, but ... more Hysteresis is a property of systems that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state. A velocity based active vibration control, along with a special class of hysteretic models using passive functions are presented in this paper. This hysteretic model is based on a modification of the Bouc-Wen model, where a nonlinear term is replaced by a passive function. The proposed class retains the rateindependence property of the original Bouc-Wen model, and it is able to reproduce several kinds of hysteretic loops that cannot be reproduced with the original Bouc-Wen model. Using this class of hysteretic models, a chattering velocity-based active vibration control scheme is developed to mitigate seismic perturbations on hysteretic base-isolated structures. Our hysteretic model is used because of its simplicity in proving the stability of the closed-loop system; i.e., a controller is designed using the proposed model, and its performance is tested on the original hysteretic system, modeled with Bouc-Wen. Numerical experiments show the robustness and efficiency of the proposed control algorithm.
American Control Conference, 2002
Nonlinear H∞-controller synthesis is developed for position tracking control of friction mechanic... more Nonlinear H∞-controller synthesis is developed for position tracking control of friction mechanical manipulators. To facilitate exposition, the friction model chosen for the treatment is confined to the Dahl model augmented with viscous friction. A local solution is derived by means of a certain perturbation of the differential Riccati equations, appearing in solving the H∞-control problem for the linearized system, when
Automatica, Sep 1, 2003
Nonlinear H∞-controller synthesis is developed for nonsmooth time-varying systems via measurement... more Nonlinear H∞-controller synthesis is developed for nonsmooth time-varying systems via measurement feedback. A local H∞-controller is derived by means of a certain perturbation of the differential Riccati equations, appearing in solving the H∞-control problem for the linearized system, when these unperturbed equations have bounded positive semidefinite solutions. Stabilizability and detectability properties of the control system are thus ensured by the
Sustainable Energy Technologies and Assessments, Oct 1, 2022
IFAC Proceedings Volumes, 2008
The main objective of applying robust active control to base-isolated structures is to protect th... more The main objective of applying robust active control to base-isolated structures is to protect them in the event of an earthquake. Taking advantage of discontinuous control theory, a static discontinuous active bang-bang type control is developed using as a feedback only the measure of the velocity at the base. Moreover, due to that in many engineering applications, accelerometers are the only devices that provide information available for feedback, our velocity feedback controller could be easily extended by using just acceleration information through a filter. The main contributions of this paper are the development and application of (a) a static velocity feedback controller design, and (b) a dynamic acceleration feedback controller design, to a benchmark problem which is recognized as a state-of-the-art model for numerical experiments of seismic control attenuation. The performance indices show that the proposed controller behaves satisfactorily and with a reasonable control effort.
IFAC Proceedings Volumes, 2008
A second order sliding mode (SOSM) approach is proposed for orbital stabilization of a friction p... more A second order sliding mode (SOSM) approach is proposed for orbital stabilization of a friction pendulum, operating under uncertain conditions. Only position measurements are assumed to be available. A SOSM velocity observer is developed and included into the closedloop system, driven by the quasihomogeneous controller that provides orbital stabilization of the pendulum. Performance issues of the observer-based position feedback synthesis are illustrated in a simulation study.
The main objective of applying robust active control to base-isolated structures is to protect th... more The main objective of applying robust active control to base-isolated structures is to protect them in the event of an earthquake. Taking advantage of discontinuous control theory, a static discontinuous active control is developed using as a feedback only the measure of the velocity at the base. Moreover, due to that in many engineering applications, accelerometers are the only devices that provide information available for feedback, our velocity feedback controller could be easily extended by using just acceleration information through a filter. The main contributions of this paper are: (a) a static velocity feedback controller design, and (b) a dynamic acceleration feedback controller design, for seismic attenuation of structures. Robustness performance is analyzed by means of numerical experiments using the 1940 El Centro earthquake.
Magnetorheological (MR) dampers have received special attention as semi-active devices for mitiga... more Magnetorheological (MR) dampers have received special attention as semi-active devices for mitigation of structural vibrations. Because of the inherent nonlinearity of these devices, it is difcult to obtain a reasonable mathematical inverse model. This paper is concerned with two related concepts. On one hand, it presents a new inverse model of MR dampers based on the normalized Bouc-Wen model. On the other hand, it considers a hybrid seismic control system for building structures, which combines a class of passive nonlinear base isolator with a semi-active control system. In this application, the MR damper is used as a semi-active device in which the voltage is updated by a feedback control loop.The management of MR dampers is performed in a hierarchical way according to the desired control force, the actual force of the dampers and its capacity to react. The control is applied to a numerical three-dimensional benchmark problem which is used by the structural control community as a state-of-the-art model for numerical experiments of seismic control attenuation. The performance indices show that the proposed semi-active controller behaves satisfactorily.
IFAC Proceedings Volumes, 2010
This paper is about chaotic logistic system realization using the PIC12F629 microcontroller manuf... more This paper is about chaotic logistic system realization using the PIC12F629 microcontroller manufactured by Microchip Technology Inc.. Implemetation done by using just assembler language machine. An appropriate scale change transformation and a re-definition of the system parameter are carried out to the logistic map to fit its microcontroller actualization. Resistive-Capacitive circuits are employed to transform binary chaotic signals into continuous ones. The obtained strange chaotic attractor is displayed on an analog oscilloscope.
Mechanical Systems and Signal Processing, 2011
Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de ... more Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de la versió author's final draft d'un article publicat a la revista Mechanical Systems and Signal Processing.
Apple Academic Press eBooks, Feb 6, 2014
This paper considers power generation control in variable-speed variable-pitch horizontal-axis wi... more This paper considers power generation control in variable-speed variable-pitch horizontal-axis wind turbines operating at high wind speeds. A dynamic chattering torque control and a proportional integral (PI) pitch control strategy are proposed and validated using the National Renewable Energy Laboratory wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. Validation results show that the proposed controllers are effective for power regulation and demonstrate high-performances for all other state variables (turbine and generator rotational speeds; and smooth and adequate evolution of the control variables) for turbulent wind conditions. To highlight the improvements of the provided method, the proposed controllers are compared to relevant previously published studies.
This work is concerned with active vibration mitigation in wind turbines (WT) but not through the... more This work is concerned with active vibration mitigation in wind turbines (WT) but not through the use of specifically tailored devices. Instead, a general control scheme is designed for torque and pitch controllers based on a super-twisting algorithm, which uses additional feedback of the fore-aft and side-to-side acceleration signals at the top of the WT tower to mitigate the vibrational behavior. In general, proposed methods to improve damping through pitch and torque control suffer from increased blade pitch actuator usage. However, in this work the blade pitch angle is smoothed leading to a decrease of the pitch actuator effort, among other benefits evidenced through numerical experiments. The most frequent faults induce vibrations in the corresponding WT subsystems. In fact, vibration monitoring has been recently used for fault diagnosis Thus, by means of vibration mitigation, different faulty conditions can be alleviated leading to a passive fault tolerant control. In this work, coupled non-linear aero-hydroservo-elastic simulations of a floating offshore wind turbine are carried out for one of the most common pitch actuator faults.
A second-order LuGre friction model is presented which can be viewed as an extension of the well ... more A second-order LuGre friction model is presented which can be viewed as an extension of the well known LuGre friction model. This model is based on a dynamic extension, which can be seen as an extra dynamic to capture some kind of periodic motion produced by the bristles in motion. The additional dynamic can be viewed as an internal disturbance due to the vibration associated with the use of motors. Our model can capture the friction phenomena of the original LuGre friction model and presents two new behaviors, one is the multi-loop behavior in the hysteresis curve when velocity is varied during unidirectional motion, and the other, in the presliding motion curve of friction force versus displacement in the spring regime, where two jumps appear.
Mathematical Problems in Engineering, Feb 12, 2021
e main contribution of this paper is the proposal of a recent hysteresis dynamic model which is s... more e main contribution of this paper is the proposal of a recent hysteresis dynamic model which is successfully employed within a posited signal modulator. e modulation of signals is a commonly required stage in many engineering applications, such as telecommunications, power electronics, and control, among others. In this paper, the effectiveness of a signal modulator based on the well-known Delta modulator when it contains a dynamic hysteresis system within its main structure is presented. To do that, it is resorted to an application of the granted Hysteresis-Delta Modulator. is application consists of including the modulator within an adaptive scheme, since it is well known that the persistent excitation condition is required, for instance, in parameter estimation tasks. Hence, the main functional property of the modulator with hysteresis is its ability of producing a modulated signal with uniform high-frequency content even when its input is not a permanent persistent excitation signal. To highlight the main contribution of this paper, a numerical experiment of a parameter estimation system is developed to compare the performance of the modulator with the proposed hysteresis model and two other previously reported hysteresis systems. at is, three different scenarios have been tested in the parameter estimation of a nonminimum phase system. Finally, the numerical experiments confirm that the proposed hysteresis model along with the modulator provides the best performance as expected.
Machines, Jul 14, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper describes how to construct a low-cost magnetic levitation system (MagLev). 1 The MagLe... more This paper describes how to construct a low-cost magnetic levitation system (MagLev). 1 The MagLev has been intensively used in the engineering education, allowing instructors and 2 students to learn through hands-on experiments essential concepts, such as electronics, electromag-3 netism, and control systems. Built from scratch, the proposed MagLev depends only on simple, 4 low-cost components readily available on the market. In addition to showing how to construct 5 the MagLev, this paper presents a semi-active control strategy which seems novel when applied 6 in the MagLev. Experiments performed in the laboratory have compared the proposed control 7 scheme with the classical PID control. The corresponding real-time experiments illustrate both the 8 effectiveness of the approach and the potential of the MagLev for education.
IFAC Proceedings Volumes, Dec 1, 2004
Orbital stabilization of a simple underactuted manipulator, namely, two-link PENDUlum roBaf is un... more Orbital stabilization of a simple underactuted manipulator, namely, two-link PENDUlum roBaf is under study. Since underactuated systems can not be locally stabilized by means of smooth feedback, the solution to the stabilization problem is sought within switched control methods. The quasihomogeneity-based synthesis is applied to design a switched controller that drives the PENDUBaf to its zero dynamics in finite time and maintains it there in sliding mode. The constructed controller is such that the pendubot zero dynamics is generated by a modified Van der Pol oscillator,. being viewed as the reference model. The proposed Van der Pol modification aims to enlarge the region of attraction of the zero dynamics while also exhibiting a desired stable periodic behavior. Performance issues of the controller constructed are illustrated in a simulation study.
IFAC Proceedings Volumes, 2011
Hysteresis is a property of systems that do not instantly follow the forces applied to them, but ... more Hysteresis is a property of systems that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state. A velocity based active vibration control, along with a special class of hysteretic models using passive functions are presented in this paper. This hysteretic model is based on a modification of the Bouc-Wen model, where a nonlinear term is replaced by a passive function. The proposed class retains the rateindependence property of the original Bouc-Wen model, and it is able to reproduce several kinds of hysteretic loops that cannot be reproduced with the original Bouc-Wen model. Using this class of hysteretic models, a chattering velocity-based active vibration control scheme is developed to mitigate seismic perturbations on hysteretic base-isolated structures. Our hysteretic model is used because of its simplicity in proving the stability of the closed-loop system; i.e., a controller is designed using the proposed model, and its performance is tested on the original hysteretic system, modeled with Bouc-Wen. Numerical experiments show the robustness and efficiency of the proposed control algorithm.
American Control Conference, 2002
Nonlinear H∞-controller synthesis is developed for position tracking control of friction mechanic... more Nonlinear H∞-controller synthesis is developed for position tracking control of friction mechanical manipulators. To facilitate exposition, the friction model chosen for the treatment is confined to the Dahl model augmented with viscous friction. A local solution is derived by means of a certain perturbation of the differential Riccati equations, appearing in solving the H∞-control problem for the linearized system, when
Automatica, Sep 1, 2003
Nonlinear H∞-controller synthesis is developed for nonsmooth time-varying systems via measurement... more Nonlinear H∞-controller synthesis is developed for nonsmooth time-varying systems via measurement feedback. A local H∞-controller is derived by means of a certain perturbation of the differential Riccati equations, appearing in solving the H∞-control problem for the linearized system, when these unperturbed equations have bounded positive semidefinite solutions. Stabilizability and detectability properties of the control system are thus ensured by the
Sustainable Energy Technologies and Assessments, Oct 1, 2022
IFAC Proceedings Volumes, 2008
The main objective of applying robust active control to base-isolated structures is to protect th... more The main objective of applying robust active control to base-isolated structures is to protect them in the event of an earthquake. Taking advantage of discontinuous control theory, a static discontinuous active bang-bang type control is developed using as a feedback only the measure of the velocity at the base. Moreover, due to that in many engineering applications, accelerometers are the only devices that provide information available for feedback, our velocity feedback controller could be easily extended by using just acceleration information through a filter. The main contributions of this paper are the development and application of (a) a static velocity feedback controller design, and (b) a dynamic acceleration feedback controller design, to a benchmark problem which is recognized as a state-of-the-art model for numerical experiments of seismic control attenuation. The performance indices show that the proposed controller behaves satisfactorily and with a reasonable control effort.
IFAC Proceedings Volumes, 2008
A second order sliding mode (SOSM) approach is proposed for orbital stabilization of a friction p... more A second order sliding mode (SOSM) approach is proposed for orbital stabilization of a friction pendulum, operating under uncertain conditions. Only position measurements are assumed to be available. A SOSM velocity observer is developed and included into the closedloop system, driven by the quasihomogeneous controller that provides orbital stabilization of the pendulum. Performance issues of the observer-based position feedback synthesis are illustrated in a simulation study.
The main objective of applying robust active control to base-isolated structures is to protect th... more The main objective of applying robust active control to base-isolated structures is to protect them in the event of an earthquake. Taking advantage of discontinuous control theory, a static discontinuous active control is developed using as a feedback only the measure of the velocity at the base. Moreover, due to that in many engineering applications, accelerometers are the only devices that provide information available for feedback, our velocity feedback controller could be easily extended by using just acceleration information through a filter. The main contributions of this paper are: (a) a static velocity feedback controller design, and (b) a dynamic acceleration feedback controller design, for seismic attenuation of structures. Robustness performance is analyzed by means of numerical experiments using the 1940 El Centro earthquake.
Magnetorheological (MR) dampers have received special attention as semi-active devices for mitiga... more Magnetorheological (MR) dampers have received special attention as semi-active devices for mitigation of structural vibrations. Because of the inherent nonlinearity of these devices, it is difcult to obtain a reasonable mathematical inverse model. This paper is concerned with two related concepts. On one hand, it presents a new inverse model of MR dampers based on the normalized Bouc-Wen model. On the other hand, it considers a hybrid seismic control system for building structures, which combines a class of passive nonlinear base isolator with a semi-active control system. In this application, the MR damper is used as a semi-active device in which the voltage is updated by a feedback control loop.The management of MR dampers is performed in a hierarchical way according to the desired control force, the actual force of the dampers and its capacity to react. The control is applied to a numerical three-dimensional benchmark problem which is used by the structural control community as a state-of-the-art model for numerical experiments of seismic control attenuation. The performance indices show that the proposed semi-active controller behaves satisfactorily.
IFAC Proceedings Volumes, 2010
This paper is about chaotic logistic system realization using the PIC12F629 microcontroller manuf... more This paper is about chaotic logistic system realization using the PIC12F629 microcontroller manufactured by Microchip Technology Inc.. Implemetation done by using just assembler language machine. An appropriate scale change transformation and a re-definition of the system parameter are carried out to the logistic map to fit its microcontroller actualization. Resistive-Capacitive circuits are employed to transform binary chaotic signals into continuous ones. The obtained strange chaotic attractor is displayed on an analog oscilloscope.