Papers by Enrique Ferreira
IFAC-PapersOnLine, 2016
This paper extends the distance-based formation control for the case of holonomic robots moving i... more This paper extends the distance-based formation control for the case of holonomic robots moving in 3D space. The approach is addressed for agents modeled as double-integrators with any undirected communication graphs. The control strategy uses a combined distance-based attractive-repulsive potentials to ensure convergence to the formation pattern avoiding possible inter-robot collisions. In order to avoid unwanted formation patterns that verify the distance constraints, each robot control law includes a volume condition which provides information about the unique desired position of each robot in the formation pattern. The proposed algorithm is tested by numerical simulations and extended to the case of quadcopters UAV's by an input-output linearization showing good behavior.
Revista Argentina de Bioingeniería, Nov 7, 2020
Revista Argentina de Bioingeniería, Nov 7, 2020
Advanced Robotics, 2016
Formation control analyses the convergence of a group of mobile agents to predefined geometric pa... more Formation control analyses the convergence of a group of mobile agents to predefined geometric patterns. In traditional approaches, it is assumed that each agent knows the exact position of certain members of the group with respect to a reference frame and the associated control laws are designed according to inter-robot relative positions. Designing a more decentralized scheme, this paper proposes a formation scheme, using Lyapunov techniques, considering that the local controllers of the agents can be equipped with distance and orientation sensors. The main result of the paper applies to certain distance-based potential functions with inter-robot collision avoidance and an arbitrary undirected formation graph. Also, the control law includes an integral-type control that eliminates the effects of the dead-zone of actuators in order to avoid the standard techniques of normalization. The control approach is analyzed for omnidirectional robots with numerical simulations and extended for unicycle-type robots with real-time experiments. Graphical Abstract
We seperate Gyrover into 4 parts: wheel, pendulum, tilt mechanism, gyro. For each part, we de ne ... more We seperate Gyrover into 4 parts: wheel, pendulum, tilt mechanism, gyro. For each part, we de ne a body-xed (local) coordinate system. Labeling numbers as: W heel! 0, P endulum! 1, T ilt mechanism! 2, Gyro! 3. The wheel contains polycarburet dome, tire and rim. ...
2017 IEEE URUCON
This work describes an IoT solution that was designed, developed and implemented to acquire time-... more This work describes an IoT solution that was designed, developed and implemented to acquire time-series, physiological data, simultaneously from different legacy medical device sources such as the communications ports of a commonly used patient monitoring system and specialized sensors. Data acquired can be further processed to observe anomalies and trends. A communications platform was also implemented for remote data visualization. A prototype of this system was then successfully deployed to collect, analyze, and visualize physiological data from patients undergoing “Tilt Table Testing” at the British Hospital in Montevideo, Uruguay, South America.
2017 IEEE URUCON, 2017
This work describes an IoT solution that was designed, developed and implemented to acquire time-... more This work describes an IoT solution that was designed, developed and implemented to acquire time-series, physiological data, simultaneously from different legacy medical device sources such as the communications ports of a commonly used patient monitoring system and specialized sensors. Data acquired can be further processed to observe anomalies and trends. A communications platform was also implemented for remote data visualization. A prototype of this system was then successfully deployed to collect, analyze, and visualize physiological data from patients undergoing “Tilt Table Testing” at the British Hospital in Montevideo, Uruguay, South America.
Acta Oto-Laryngologica, 2013
The measurement of the energy consumption (EC) of the body&am... more The measurement of the energy consumption (EC) of the body's center of pressure (COP) to maintain the upright stance position was higher in elderly patients with bilateral vestibular hypofunction (BVH) compared with a control group and may be a valid parameter in the assessment of balance disorders. The aim of the study was to evaluate the energy consumption of the COP in elderly patients with BVH. The COP was recorded on a force platform (FP) for eight elderly patients with BVH related to aging and eight normal control group subjects. The EC of the COP was calculated using the discrete wavelet transform. The two groups were tested in standing position on the FP in three sensory conditions:1, eyes open; 2, eyes closed; and 3, standing on a foam pad placed on the force platform. Wilcoxon's rank test and multi-factor analysis of variance were used, with the level of significance set at 0.05. BVH patients showed higher values of EC of the COP signal measured in arbitrary units compared with the control group (conditions 1 and 2). None of the BVH patients could perform the test in condition 3. BVH patients had increased EC in the frequency band between 0.1 and 0.78 Hz when the visual information was canceled (condition 2).
Abstract. The introduction of new in situ sensing creates the possibility of directly controlling... more Abstract. The introduction of new in situ sensing creates the possibility of directly controlling critical process variables in plasma enhanced chemical vapor deposition systems (PECVD). The complexity of this process makes it necessary to develop empirical models of the system dynamics. This paper describes the experimental and numerical procedures for identifying both transfer function and recurrent neural net multi-input multi-output models of PECVD dynamics. The models are compared in terms of the resulting mean-squared-prediction-error for veri cation data sets. The neural net models are shown to be mildly superior in cases where the input signals vary widely, stimulating the nonlinear response of the system.
The Gyrover is a single wheel gyroscopically stabilized mobile robot developed at Carnegie Mellon... more The Gyrover is a single wheel gyroscopically stabilized mobile robot developed at Carnegie Mellon University. An internal pendulum serves as a counter weight for a drive motor that causes fore/aft motion, while a tilt-mechanism on a large gyroscope provides a mechanism for lateral actuation. In this paper, we develop a detailed dynamic model for the Gyrover, and use this model in an extended Kalman filter to estimate the complete state. A linearized version of the model is used to develop a state feedback controller. The design methodology is based on a semidefinite programming procedure which optimize the stability region subject to a set of Linear Matrix Inequalities that capture stability and pole placement constraints. Finally, the controller design combined with the extended Kalman filter are verified on the prototype.
In this thesis we explore the use of neural networks to evaluate the performance of nonlinear sys... more In this thesis we explore the use of neural networks to evaluate the performance of nonlinear systems and to switch among a pool of controllers to achieve a desired closed-loop performance. This method is motivated on the needs of a automated way to generate controller schedules and the development of a control architecture for evolvable systems called SIMPLEX. The method is based on two neural network estimates for each controller, one for its region of stability and another for a performance index. Neurodynamic programming techniques are used for neural network training providing a way to realize the architecture in real-time. Several types of estimates are developed to handle uncertainties and disturbances. Convergence of the algorithms and confidence intervals are analyzed. The architecture and controller scheduling algorithm developed in this thesis allows us to assure stability of the closed-loop system and improve closed-loop performance by combining tested and new controller...
El presente artículo introduce una aproximación al problema de “Anomaly Intrusion Detection” basa... more El presente artículo introduce una aproximación al problema de “Anomaly Intrusion Detection” basada en una combinación de algoritmos de “Machine Learning” (ML) supervisados y no supervisados. Los objetivos que se persiguen son: el modelar en forma efectiva el tráfico de una organización y el reducir en forma substancial el porcentaje de Falsos Positivos mientras se mantiene un nivel razonable de detección de anomalías. Se presenta una arquitectura basada en un conjunto de “Self-Organizing Maps” (SOM) para el modelado del tráfico y en el uso de “Linear Vector Quantization” (LVQ) para la clasificación definitiva de los paquetes de tráfico. Los algoritmos desarrollados usan Snort para el preprocesamiento del tráfico de red, y están pensados para ser un complemento de esta herramienta. Los resultados alcanzados hasta el momento muestran que se pueden lograr niveles aceptables de acierto en comparación con otras técnicas. Al final se plantean las conclusiones extraídas del trabajo y dire...
: In this report, we present preliminary results on the design of the baseline controller for an ... more : In this report, we present preliminary results on the design of the baseline controller for an F-16 aircraft automatic landing system using linear matrix inequalities (LMI)-based approaches. We start with a general study of aircraft control and dynamics to gain knowledge of the structure of an aircraft dynamic model and its inner loop control system. We then identify a linear model along the glide path for the inner loop control system in the simulator. With this linear model, the control objective is to solve a stabilization problem-stabilizing the aircraft along the glide path using linear state feedback controls. Expressing the stability criterion and the constraints in LMIs, we cast the stabilization problem as an optimization problem. Using the SDPSOL software package developed by Wu and Boyd, we solve this optimization problem for the control gain and stability region, which completes the controller design.
Cochlear Implants International
Aims/Objectives: Understand the relationship between auditory input and balance motor control. Ma... more Aims/Objectives: Understand the relationship between auditory input and balance motor control. Material and Methods: Twelve prelingual adolescent cochlear implant users (CIU) and 12 adult postlingual CIU were tested by posturography on a force platform with eyes open in two conditions, with the cochlear implant (CI) on and off. Energy consumption (EC) of the body center of pressure sway signal was measured, calculating total EC and divided into three bands of frequencies; low (B1) 0–0.1 Hz, medium (B2) 0.1–1 Hz, and high (B3)1–2 Hz. Wilcoxon and Mann–Whitney tests were used for statistical analysis and the significance level was P ≤ 0.05. Results: Prelingual CIU decrease the EC in low and high frequencies throughout the adolescence (P < 0.05) assessed with the CI turned on, while it did not show any modification with the CI off. Postlingual CIU showed a deterioration of PR related to aging when evaluated with the CIU turned off, P < 0.05 in band 1. However, with the CI turned on they had no significant increase in this age range. Conclusions and Significance: The acoustic input improved EC of postural responses in higher and lower frequencies in adolescence and with aging which suggests a relationship with gross and fine movements involved in postural control.
Acta Oto-Laryngologica
Abstract Background: Information about the role of auditory input and motor control is limited. O... more Abstract Background: Information about the role of auditory input and motor control is limited. Objectives: Assessment the relationship between auditory and vestibular information with specific motor and cognitive functions. Methods: Posturography in 17 Pre-lingual Cochlear Implant Adolescents, (PCIA) age 14.06 ± 3.05 in four sensory conditions was analyzed: (A) eyes open, cochlear implant (CI) on, (B) eyes open, CI off, (C) eyes closed standing on a foam over a platform (ECFP) with CI on, and (D) ECFP, CI off. Gait velocity (GV) was registered by inertial sensors using a 10-meter test. Vestibulo-ocular reflex (VOR) was evaluated with the video head impulse test (VHIT) and visual spatial skill (VS) assessed with the WISC-V test. Results: SV had no significant difference between conditions A and B (p = .2461). Comparing C and D, SV values decreased when CI was turned on (p = .0036). A significant linear relationship between VOR and GV (p = .0064) generating the VOR gain loss lower gait. Relationship between VOR and VS scores was no significant (p = .685). Conclusions and significance: Auditory information is a relevant cue when somatosensory and visual inputs are modified and range of vestibular function influence in a dynamic motor activity as gait, facts which must be considered in the neurodevelopment control.
IFAC Proceedings Volumes
The introduction of new in situ sensing creates the possibility of directly controlling critical ... more The introduction of new in situ sensing creates the possibility of directly controlling critical process variables in plasma enhanced chemical vapor deposition systems PECVD. The complexity of this process makes it necessary to develop empirical models of the system dynamics. This paper describes the experimental and numerical procedures for identifying both transfer function and recurrent neural net multi-input multi-output models of PECVD dynamics. The models are compared in terms of the resulting mean-squared-prediction-error for veri cation data sets. The neural net models are shown to be mildly superior in cases where the input signals vary widely, stimulating the nonlinear response of the system.
Computers & Chemical Engineering
Acta Oto-Laryngologica, 2016
The results suggest that auditory input is not neutral in motor skills and the complex interactio... more The results suggest that auditory input is not neutral in motor skills and the complex interaction between them is generated in the earlier stages of childhood development. Objective The assessment of gait performance in pre-lingual deaf children with cochlear implant (CI). Gait velocity (GV), using a 10-meter test, was measured by means of three inertial sensors in 10 pre-lingual cochlear implant users (CIU) (10-16 years old) in three sensory conditions: (1) cochlear implant turned on with environmental noise (EN), (2) cochlear implant turned on with EN and with cognitive dual task (DT), and (3) CI turned off (CI-OFF). GV with EN and DT was assessed in a normal hearing control group (CG) (n = 14). Mann-Whitney and Wilcoxon Signed ranked test were used for significance validation. (1) GV in CG was lower in DT than with EN (p = .019). (2) GV was faster in CG with EN compared with the three conditions in CIU (EN, p = .006; DT, p = .0001; CI-OFF, p = .03). (3) CIU had slower GV walking with EN (p = .037) and with DT (p = .022). (4) Dividing the CIU sample by age, the acoustic information generates a slower gait for those implanted after 3 years old.
IFAC-PapersOnLine, 2015
This paper presents a two-level control strategy for the trajectory tracking of the quadcopter. T... more This paper presents a two-level control strategy for the trajectory tracking of the quadcopter. The external loop is designed to move the translational dynamics of the robot to follow smooth parametric functions using an appropriate variables substitution. The outer loop generates the desired trajectories of the orientation angles, which are controlled in the inner loop. The parameter gains are calculated using linear optimal control in order to minimize the energy consumption of the rotors. The control architecture is designed to be compatible with standard electronic platforms of commercial quadcopters and incorporates the purpose of maximizing flight time, an important requirement in real applications of multi-rotor aerial vehicles. Some numerical simulations show the performance of the control approach.
Uploads
Papers by Enrique Ferreira