Automation at the process level for machining operations and machine tools has been a focus of re... more Automation at the process level for machining operations and machine tools has been a focus of research attention in both academia and industry alike for several decades. Research in this area has carried strong expectations in the context of increased productivity, improved part quality, reduced costs, and relaxed part design constraints. The basis for these expectations is two-fold. First, machining process automation, if exercised strategically and advantageously, can perform consistently for large batch production or flexibly for small batch jobs. Secondly, process automation can be set up to autonomously tune the machine parameters (feed, speed, depth of cut, etc.) in pursuit of desirable performance (tolerance, finish, cycle time, etc.), thereby bridging the gap between product design and process planning while reaching beyond the human operators' capability. The success of manufacturing process automation hinges primarily on the effectiveness of process monitoring and control systems. This paper reviews the evolution and the state of the art of machining process monitoring and control technologies. Key issues to be presented include sensor techniques, control techniques, hardware availability, and implementation examples. Also to be reviewed are the benefits of the systems and the reasons for their delayed realization in many of today's industrial application domains.
Exigencias de calidad, reduccion de costos y rapida respuesta al mercado requieren de maquinas he... more Exigencias de calidad, reduccion de costos y rapida respuesta al mercado requieren de maquinas herramientas con mayor y mejores prestaciones desde el punto de vista de su control. El conocimiento de la fuerza de mecanizado es de gran importancia tanto para la implementacion de tecnicas de control adaptivas como para el monitoreo del estado de la herramienta de corte (desgaste, rotura del filo, etc.). En este trabajo se presenta el diseno de una celda de carga para medir las fuerzas presentes en procesos de mecanizado, su fabricacion y resultados experimentales. Este dispositivo permite medir fuerzas estaticas a partir de la deformacion captada por galgas extensiometricas (strain-gauge) pegadas en la superficie de elementos deformables o resortes del tipo anillo octogonal. Las condiciones de aplicacion exigen el diseno de una celda de carga capaz de medir las tres componentes ortogonales de una fuerza orientada en el espacio. Ademas, su rigidez debe ser lo suficientemente alta para e...
Soil compaction is an important degradation phenomenon that can affect root growth, and consequen... more Soil compaction is an important degradation phenomenon that can affect root growth, and consequently crop yield. Therefore it becomes relevant to have soil compaction data for future improvements on precision agriculture management. A traditional on-the-field data related to soil compaction is cone index obtained using a penetrometer; however, this methodology is time consuming for a high density data. Therefore, on-the-go sensors have been developed to continually estimate the variable of interest. This work proposes an on-the-go sensor to estimate the soil horizontal resistance at different depths. The main design concept is based on embedded load cells at three different depths, resulting in a robust sensor with high sensitivity. The prototype was first tested and calibrated in laboratory, and then, it was tested in the field. The calculated horizontal resistance index (HRI) at the three depths was correlated with the cone index (CI) using a cone penetrometer, showing that this sensor can replace the penetrometer data, allowing the possibility of taking continuous data on the field.
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering
In the last decades, several friction models suitable for control purposes have been proposed, wh... more In the last decades, several friction models suitable for control purposes have been proposed, which are able to represent most of the observed friction behavior. However, this comes at the cost of an increased complexity, presenting in some cases switched dynamics, as in the generalized Maxwell-slip friction model. Thus, consideration of these models in control design certainly increases the complexity of stability proofs, and thus, their use in control design except for feedforward compensation. The purpose of this work is to provide stability results to facilitate the application of these models in feedback control. First, results are given for a more general model with switched dynamics, and then results are given for the particular case of the generalized Maxwell-slip model. Then, the application of these developments is illustrated for the case of a deterministic robust control design for a linear motor drive. In this case, controllers with feedforward and feedback friction co...
Resumen. La compactación de los suelos agrícolas forma parte de los principales factores de degra... more Resumen. La compactación de los suelos agrícolas forma parte de los principales factores de degradación de los mismos e incide negativamente en el rendimiento de los cultivos. A la hora de elaborar estrategias de manejo de suelos, determinar el grado de compactación del mismo tanto como su variabilidad espacial en una zona determinada, forma parte de los datos de entrada de la toma de decisiones bajo el paradigma de la Agricultura de Precisión sobre y para un modelo de explotación agrícola eficiente y sustentable. En este trabajo se presenta el diseño de un dispositivo que permitirá estimar la compactación del suelo. El mismo consiste en una cuchilla plana que posibilita medir la resistencia mecánica a distintas profundidades, cuando esta se desplaza dentro del mismo. Se utilizan herramientas de cálculo y simulación por elemento finito y conceptos de diseño flexure stage para la obtención de un diseño robusto y simplicidad constructiva.
Revista Iberoamericana De Ingenieria Mecanica, 2012
Quality improvement and cost reduction drives the development of equipment to measure and control... more Quality improvement and cost reduction drives the development of equipment to measure and control the main process variables in mechanical manufacturing. Particularly, in material removal processes, the monitoring of force, temperature and vibration can lead to process optimization and early failure detection. Following this concept, this paper presents de development of a system to monitor the cutting force and the temperature at the tool-chip interface. The force is directly measured using strain gauges in the tool system. Although this is a simple set-up, it is useful to test the complete monitoring system. Whereas, the cutting temperature is estimated using the measurement of a thermocouple placed in the base of the cutting tool together with an iterative filter. Finally, the detailed implementation is presented and experimental results from turning operations are shown.
This work proposes a procedure to sizing a ball-screw feed drive considering the closed-loop perf... more This work proposes a procedure to sizing a ball-screw feed drive considering the closed-loop performance. This is achieved by additional steps to the traditional mechanical sizing, where a high frequency model is used to tune the controller in order to achieve adequate stability margins. After that, the tracking error is evaluated for different screw candidates, under nominal and non-nominal operational conditions for a high speed machine tool. Finally, the optimum screw assemble is selected based on minimum torque requirement. As a main conclusion, the screw lead is identified as a high influencing factor in the system dynamics and then on the closed-loop performance, showing the need of an integrated design.
The ball screw drives are among the most commonly mechanisms used to provide motion in high speed... more The ball screw drives are among the most commonly mechanisms used to provide motion in high speed machine tools. The most important factor that affects high speed positioning accuracy is the closed loop bandwidth, which in turn is affected by the structural vibration modes. In recent years, newer strategies have emerged achieving higher control bandwidth, but requiring higher order plant models as well as a better understanding of the system dynamics. This work presents a dynamic model of a lead screw drive accounting for high frequency modes. The analytical formulation follows a comprehensive approach, where the screw was modeled as a continuous subsystem. The axial and angular displacement fields for this continuous screw were approximated by Ritz series to obtain an approximate N-degree-of-freedom model. Furthermore, it is discussed how to decouple the damping matrix to transform an N-degree-of-freedom system into N one-degree-of-freedom systems, because the advantages that this implies when numerical solution is required. Then, expressions for the displacement fields in terms of modal coordinates are found and a procedure to compute the axial and angular components of the mode functions is discussed, as well as a numerical procedure to compute the system deformation. In order to obtain conclusions about the system behavior in the first modes, the axial an angular components of the mode functions are plotted. Then, an analysis based on a comparison with results from others works is presented.
Friction is a complex phenomenon which has negative effects on the precision of positioning syste... more Friction is a complex phenomenon which has negative effects on the precision of positioning systems. Therefore, friction models for use in friction compensation have to show a good performance while remaining simple enough for its use in control algorithms. In this work, a single-state friction model for control purposes is proposed, aiming to simplify the implementation of such control algorithms, while keeping a good performance in friction compensation. This model has been tested on an experimental setup based on a linear motor, and its performance is compared to that of the Generalized Maxwell-slip (GMS) model, showing better performance on the tracking error for low accelerations.
En este trabajo se presenta el diseno e implementacion de un dispositivo para posicionamientos de... more En este trabajo se presenta el diseno e implementacion de un dispositivo para posicionamientos de precision con un rango de desplazamiento de 18 micrones y resolucion nanometrica. Para la etapa de diseno se impuso que el ancho de banda de lazo cerrado sea relativamente alto, en el orden de 100 Hz. El sistema de guiado es del tipo “flexure stage” y es accionado por un piezoelectrico. El ancho de banda especificado requiere de una rigidez del sistema tal que el primer modo de vibracion del conjunto sea al menos 10 veces superior. Por otro lado, las exigencias de alineacion del piezoelectrico, para evitar esfuerzos de tension destructivas, conducen a la utilizacion de acoples del tipo esfera-superficie plana. El trabajo presenta el proceso de diseno del sistema de posicionamiento y el efecto que introduce el metodo de montaje. Tanto la rigidez del flexure como la del acople provocan una disminucion del recorrido util del actuador. Ademas el sistema de montaje introduce una disminucion ...
Un sistema de posicionamiento nanometrico permite realizar desplazamientos de algunos micrometros... more Un sistema de posicionamiento nanometrico permite realizar desplazamientos de algunos micrometros con resoluciones en el orden de los nanometros. Son utilizados en aplicaciones de alta precision como microscopia, metrologia, fabricacion de sistemas electromecanicos microscopicos (MEMS, siglas en ingles), entre otras. Para su implementacion lo usual es utilizar un actuador piezoelectrico y una estructura flexible para guiar su movimiento. Este trabajo presenta el analisis dinamico de un sistema de posicionamiento nanometrico que fue disenado para alcanzar una velocidad de actuacion relativamente alta. Bajo estas exigencias el primer modo de vibracion del sistema debe ser diez veces mayor al ancho de banda del lazo de control. Mediante simulacion por el metodo de elementos finitos se obtuvieron las frecuencias naturales del sistema, siendo el tercer modo de vibracion coincidente con la direccion del movimiento. Ademas, las mismas permiten observar los restantes modos a partir de los c...
Las exigencias del mercado actual impulsan el desarrollo de ma- quinas y equipos mas eficientes y... more Las exigencias del mercado actual impulsan el desarrollo de ma- quinas y equipos mas eficientes y precisos. La precision de las maquinas herramientas depende fuertemente de sus sistemas de posicionamiento. Para asegurar las especificaciones de alta velocidad y alta precision de posicionamiento se requiere que estos sistemas sean disenados bajo una concepcion mecatronica. Esto es, mediante un proceso que integre tanto el diseno mecanico como el diseno de los controladores de movimiento. Previo al estudio del procedimiento del diseno integrado, es necesario obtener modelos matematicos de la dinamica del sistema, los controladores de movimiento y las condiciones externas que actuan sobre el sistema como por ejemplo las fuerzas de maquinado. En este sentido se pretende avanzar sobre los modelos dinamicos, a partir de los cuales se simularan diferentes tecnicas de control para estudiar su robustez frente a cambios de parametros del sistema y frente a perturbaciones externas. Paralelament...
This paper describes the design of a power controller in cylindrical traverse grinding (CTG), whe... more This paper describes the design of a power controller in cylindrical traverse grinding (CTG), where the power consumed by the grinding wheel is controlled by regulation of the traverse velocity. A mathematical model relating the power to the traverse velocity was developed and quantified with machining data. The controller design was based on the power-velocity model developed and it was tuned to fulfill time response specifications including settling time and overshoot. An inner velocity loop was also designed and implemented inside the power close loop to guaranty a stable power response. The controller was implemented and tested on an open architecture cylindrical grinding machine. The results show that the controlled system response can be regulated to meet the requirements of time specifications, over a wide range of cutting depth and input power reference.
Abstract Discrete modal filters can be obtained as a weighted sum of the output signals from an a... more Abstract Discrete modal filters can be obtained as a weighted sum of the output signals from an array of discrete sensors installed in a flexible structure. Although several researchers proposed different design methodologies and implementation strategies for modal filters based on a particular array of discrete sensors, the noise component of these sensors was not analyzed and included in the design process. Therefore, this work presents a methodology to identify the topology of sensors and filter gains that minimize the noise component in the filter output. The experimental implementation of this methodology shows that an adequate topology of sensors can maintain the same level of noise from the sensors in the filter output. Furthermore, the noise at the filter output can increase considerably if other not suitable topologies are selected.
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2019
While the use of integral action in control is quite common, in part due to its benefits for outp... more While the use of integral action in control is quite common, in part due to its benefits for output regulation, it can also be counterproductive when abrupt changes in disturbance occur during tracking. In order to mitigate its counterproductive effect while at the same time maintaining its advantages for regulation, this work proposes a new type of integral action, including a time-varying forgetting factor suited to the expected behavior of the disturbance during tracking. Also, Lyapunov stability techniques are used to derive general results aiming to reduce the complexity of stability analysis and control design when the proposed integral action is included in a control law. In particular, these results are used for stability analysis when the proposed integral action is implemented in a deterministic robust controller for a linear motor system. Furthermore, the controller is implemented in the corresponding experimental setup, resulting in an improvement on maximum tracking err...
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2018
This work proposes a deterministic robust controller to improve tracking performance for a linear... more This work proposes a deterministic robust controller to improve tracking performance for a linear motor, taking into account the electrical dynamics imposed by a commercial current controller. The design is split in two parts by means of the backstepping technique, in which the first part corresponds to a typical deterministic robust controller, neglecting the electrical dynamics. In the second part, a second-order electrical dynamics is considered using a particular state transformation. There, the proposed control law is composed of a term to compensate the known part of the model and a robust control term to impose a bound on the effect of uncertainties on tracking error. Stability and boundedness results for the complete controller are given. To this effect, a general result on boundedness and stability of nonlinear systems with conditionally bounded state variables is derived first. Finally, experimental results for the complete controller show an improvement on tracking error ...
Automation at the process level for machining operations and machine tools has been a focus of re... more Automation at the process level for machining operations and machine tools has been a focus of research attention in both academia and industry alike for several decades. Research in this area has carried strong expectations in the context of increased productivity, improved part quality, reduced costs, and relaxed part design constraints. The basis for these expectations is two-fold. First, machining process automation, if exercised strategically and advantageously, can perform consistently for large batch production or flexibly for small batch jobs. Secondly, process automation can be set up to autonomously tune the machine parameters (feed, speed, depth of cut, etc.) in pursuit of desirable performance (tolerance, finish, cycle time, etc.), thereby bridging the gap between product design and process planning while reaching beyond the human operators' capability. The success of manufacturing process automation hinges primarily on the effectiveness of process monitoring and control systems. This paper reviews the evolution and the state of the art of machining process monitoring and control technologies. Key issues to be presented include sensor techniques, control techniques, hardware availability, and implementation examples. Also to be reviewed are the benefits of the systems and the reasons for their delayed realization in many of today's industrial application domains.
Exigencias de calidad, reduccion de costos y rapida respuesta al mercado requieren de maquinas he... more Exigencias de calidad, reduccion de costos y rapida respuesta al mercado requieren de maquinas herramientas con mayor y mejores prestaciones desde el punto de vista de su control. El conocimiento de la fuerza de mecanizado es de gran importancia tanto para la implementacion de tecnicas de control adaptivas como para el monitoreo del estado de la herramienta de corte (desgaste, rotura del filo, etc.). En este trabajo se presenta el diseno de una celda de carga para medir las fuerzas presentes en procesos de mecanizado, su fabricacion y resultados experimentales. Este dispositivo permite medir fuerzas estaticas a partir de la deformacion captada por galgas extensiometricas (strain-gauge) pegadas en la superficie de elementos deformables o resortes del tipo anillo octogonal. Las condiciones de aplicacion exigen el diseno de una celda de carga capaz de medir las tres componentes ortogonales de una fuerza orientada en el espacio. Ademas, su rigidez debe ser lo suficientemente alta para e...
Soil compaction is an important degradation phenomenon that can affect root growth, and consequen... more Soil compaction is an important degradation phenomenon that can affect root growth, and consequently crop yield. Therefore it becomes relevant to have soil compaction data for future improvements on precision agriculture management. A traditional on-the-field data related to soil compaction is cone index obtained using a penetrometer; however, this methodology is time consuming for a high density data. Therefore, on-the-go sensors have been developed to continually estimate the variable of interest. This work proposes an on-the-go sensor to estimate the soil horizontal resistance at different depths. The main design concept is based on embedded load cells at three different depths, resulting in a robust sensor with high sensitivity. The prototype was first tested and calibrated in laboratory, and then, it was tested in the field. The calculated horizontal resistance index (HRI) at the three depths was correlated with the cone index (CI) using a cone penetrometer, showing that this sensor can replace the penetrometer data, allowing the possibility of taking continuous data on the field.
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering
In the last decades, several friction models suitable for control purposes have been proposed, wh... more In the last decades, several friction models suitable for control purposes have been proposed, which are able to represent most of the observed friction behavior. However, this comes at the cost of an increased complexity, presenting in some cases switched dynamics, as in the generalized Maxwell-slip friction model. Thus, consideration of these models in control design certainly increases the complexity of stability proofs, and thus, their use in control design except for feedforward compensation. The purpose of this work is to provide stability results to facilitate the application of these models in feedback control. First, results are given for a more general model with switched dynamics, and then results are given for the particular case of the generalized Maxwell-slip model. Then, the application of these developments is illustrated for the case of a deterministic robust control design for a linear motor drive. In this case, controllers with feedforward and feedback friction co...
Resumen. La compactación de los suelos agrícolas forma parte de los principales factores de degra... more Resumen. La compactación de los suelos agrícolas forma parte de los principales factores de degradación de los mismos e incide negativamente en el rendimiento de los cultivos. A la hora de elaborar estrategias de manejo de suelos, determinar el grado de compactación del mismo tanto como su variabilidad espacial en una zona determinada, forma parte de los datos de entrada de la toma de decisiones bajo el paradigma de la Agricultura de Precisión sobre y para un modelo de explotación agrícola eficiente y sustentable. En este trabajo se presenta el diseño de un dispositivo que permitirá estimar la compactación del suelo. El mismo consiste en una cuchilla plana que posibilita medir la resistencia mecánica a distintas profundidades, cuando esta se desplaza dentro del mismo. Se utilizan herramientas de cálculo y simulación por elemento finito y conceptos de diseño flexure stage para la obtención de un diseño robusto y simplicidad constructiva.
Revista Iberoamericana De Ingenieria Mecanica, 2012
Quality improvement and cost reduction drives the development of equipment to measure and control... more Quality improvement and cost reduction drives the development of equipment to measure and control the main process variables in mechanical manufacturing. Particularly, in material removal processes, the monitoring of force, temperature and vibration can lead to process optimization and early failure detection. Following this concept, this paper presents de development of a system to monitor the cutting force and the temperature at the tool-chip interface. The force is directly measured using strain gauges in the tool system. Although this is a simple set-up, it is useful to test the complete monitoring system. Whereas, the cutting temperature is estimated using the measurement of a thermocouple placed in the base of the cutting tool together with an iterative filter. Finally, the detailed implementation is presented and experimental results from turning operations are shown.
This work proposes a procedure to sizing a ball-screw feed drive considering the closed-loop perf... more This work proposes a procedure to sizing a ball-screw feed drive considering the closed-loop performance. This is achieved by additional steps to the traditional mechanical sizing, where a high frequency model is used to tune the controller in order to achieve adequate stability margins. After that, the tracking error is evaluated for different screw candidates, under nominal and non-nominal operational conditions for a high speed machine tool. Finally, the optimum screw assemble is selected based on minimum torque requirement. As a main conclusion, the screw lead is identified as a high influencing factor in the system dynamics and then on the closed-loop performance, showing the need of an integrated design.
The ball screw drives are among the most commonly mechanisms used to provide motion in high speed... more The ball screw drives are among the most commonly mechanisms used to provide motion in high speed machine tools. The most important factor that affects high speed positioning accuracy is the closed loop bandwidth, which in turn is affected by the structural vibration modes. In recent years, newer strategies have emerged achieving higher control bandwidth, but requiring higher order plant models as well as a better understanding of the system dynamics. This work presents a dynamic model of a lead screw drive accounting for high frequency modes. The analytical formulation follows a comprehensive approach, where the screw was modeled as a continuous subsystem. The axial and angular displacement fields for this continuous screw were approximated by Ritz series to obtain an approximate N-degree-of-freedom model. Furthermore, it is discussed how to decouple the damping matrix to transform an N-degree-of-freedom system into N one-degree-of-freedom systems, because the advantages that this implies when numerical solution is required. Then, expressions for the displacement fields in terms of modal coordinates are found and a procedure to compute the axial and angular components of the mode functions is discussed, as well as a numerical procedure to compute the system deformation. In order to obtain conclusions about the system behavior in the first modes, the axial an angular components of the mode functions are plotted. Then, an analysis based on a comparison with results from others works is presented.
Friction is a complex phenomenon which has negative effects on the precision of positioning syste... more Friction is a complex phenomenon which has negative effects on the precision of positioning systems. Therefore, friction models for use in friction compensation have to show a good performance while remaining simple enough for its use in control algorithms. In this work, a single-state friction model for control purposes is proposed, aiming to simplify the implementation of such control algorithms, while keeping a good performance in friction compensation. This model has been tested on an experimental setup based on a linear motor, and its performance is compared to that of the Generalized Maxwell-slip (GMS) model, showing better performance on the tracking error for low accelerations.
En este trabajo se presenta el diseno e implementacion de un dispositivo para posicionamientos de... more En este trabajo se presenta el diseno e implementacion de un dispositivo para posicionamientos de precision con un rango de desplazamiento de 18 micrones y resolucion nanometrica. Para la etapa de diseno se impuso que el ancho de banda de lazo cerrado sea relativamente alto, en el orden de 100 Hz. El sistema de guiado es del tipo “flexure stage” y es accionado por un piezoelectrico. El ancho de banda especificado requiere de una rigidez del sistema tal que el primer modo de vibracion del conjunto sea al menos 10 veces superior. Por otro lado, las exigencias de alineacion del piezoelectrico, para evitar esfuerzos de tension destructivas, conducen a la utilizacion de acoples del tipo esfera-superficie plana. El trabajo presenta el proceso de diseno del sistema de posicionamiento y el efecto que introduce el metodo de montaje. Tanto la rigidez del flexure como la del acople provocan una disminucion del recorrido util del actuador. Ademas el sistema de montaje introduce una disminucion ...
Un sistema de posicionamiento nanometrico permite realizar desplazamientos de algunos micrometros... more Un sistema de posicionamiento nanometrico permite realizar desplazamientos de algunos micrometros con resoluciones en el orden de los nanometros. Son utilizados en aplicaciones de alta precision como microscopia, metrologia, fabricacion de sistemas electromecanicos microscopicos (MEMS, siglas en ingles), entre otras. Para su implementacion lo usual es utilizar un actuador piezoelectrico y una estructura flexible para guiar su movimiento. Este trabajo presenta el analisis dinamico de un sistema de posicionamiento nanometrico que fue disenado para alcanzar una velocidad de actuacion relativamente alta. Bajo estas exigencias el primer modo de vibracion del sistema debe ser diez veces mayor al ancho de banda del lazo de control. Mediante simulacion por el metodo de elementos finitos se obtuvieron las frecuencias naturales del sistema, siendo el tercer modo de vibracion coincidente con la direccion del movimiento. Ademas, las mismas permiten observar los restantes modos a partir de los c...
Las exigencias del mercado actual impulsan el desarrollo de ma- quinas y equipos mas eficientes y... more Las exigencias del mercado actual impulsan el desarrollo de ma- quinas y equipos mas eficientes y precisos. La precision de las maquinas herramientas depende fuertemente de sus sistemas de posicionamiento. Para asegurar las especificaciones de alta velocidad y alta precision de posicionamiento se requiere que estos sistemas sean disenados bajo una concepcion mecatronica. Esto es, mediante un proceso que integre tanto el diseno mecanico como el diseno de los controladores de movimiento. Previo al estudio del procedimiento del diseno integrado, es necesario obtener modelos matematicos de la dinamica del sistema, los controladores de movimiento y las condiciones externas que actuan sobre el sistema como por ejemplo las fuerzas de maquinado. En este sentido se pretende avanzar sobre los modelos dinamicos, a partir de los cuales se simularan diferentes tecnicas de control para estudiar su robustez frente a cambios de parametros del sistema y frente a perturbaciones externas. Paralelament...
This paper describes the design of a power controller in cylindrical traverse grinding (CTG), whe... more This paper describes the design of a power controller in cylindrical traverse grinding (CTG), where the power consumed by the grinding wheel is controlled by regulation of the traverse velocity. A mathematical model relating the power to the traverse velocity was developed and quantified with machining data. The controller design was based on the power-velocity model developed and it was tuned to fulfill time response specifications including settling time and overshoot. An inner velocity loop was also designed and implemented inside the power close loop to guaranty a stable power response. The controller was implemented and tested on an open architecture cylindrical grinding machine. The results show that the controlled system response can be regulated to meet the requirements of time specifications, over a wide range of cutting depth and input power reference.
Abstract Discrete modal filters can be obtained as a weighted sum of the output signals from an a... more Abstract Discrete modal filters can be obtained as a weighted sum of the output signals from an array of discrete sensors installed in a flexible structure. Although several researchers proposed different design methodologies and implementation strategies for modal filters based on a particular array of discrete sensors, the noise component of these sensors was not analyzed and included in the design process. Therefore, this work presents a methodology to identify the topology of sensors and filter gains that minimize the noise component in the filter output. The experimental implementation of this methodology shows that an adequate topology of sensors can maintain the same level of noise from the sensors in the filter output. Furthermore, the noise at the filter output can increase considerably if other not suitable topologies are selected.
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2019
While the use of integral action in control is quite common, in part due to its benefits for outp... more While the use of integral action in control is quite common, in part due to its benefits for output regulation, it can also be counterproductive when abrupt changes in disturbance occur during tracking. In order to mitigate its counterproductive effect while at the same time maintaining its advantages for regulation, this work proposes a new type of integral action, including a time-varying forgetting factor suited to the expected behavior of the disturbance during tracking. Also, Lyapunov stability techniques are used to derive general results aiming to reduce the complexity of stability analysis and control design when the proposed integral action is included in a control law. In particular, these results are used for stability analysis when the proposed integral action is implemented in a deterministic robust controller for a linear motor system. Furthermore, the controller is implemented in the corresponding experimental setup, resulting in an improvement on maximum tracking err...
Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 2018
This work proposes a deterministic robust controller to improve tracking performance for a linear... more This work proposes a deterministic robust controller to improve tracking performance for a linear motor, taking into account the electrical dynamics imposed by a commercial current controller. The design is split in two parts by means of the backstepping technique, in which the first part corresponds to a typical deterministic robust controller, neglecting the electrical dynamics. In the second part, a second-order electrical dynamics is considered using a particular state transformation. There, the proposed control law is composed of a term to compensate the known part of the model and a robust control term to impose a bound on the effect of uncertainties on tracking error. Stability and boundedness results for the complete controller are given. To this effect, a general result on boundedness and stability of nonlinear systems with conditionally bounded state variables is derived first. Finally, experimental results for the complete controller show an improvement on tracking error ...
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Papers by Rogelio Hecker