Carlos F Rengifo | Universidad del Cauca (original) (raw)

Papers by Carlos F Rengifo

Research paper thumbnail of A Multidisciplinary Approach Integrating Emergy Analysis and Process Modeling for Agricultural Systems Sustainable Management—Coffee Farm Validation

Sustainability

Agricultural production operates via the existing relationships between nature and economy. Its s... more Agricultural production operates via the existing relationships between nature and economy. Its sustainable development requires tools that provide a broad vision of the energy flows that intervene in these systems, to support the decision-making process in energy management. To quantify the environmental resources and economic inputs involved, emergy analysis has been used, as well as process modeling, to make a detailed record of the system inputs. The research aim is to propose a multidisciplinary approach that integrates emergy analysis and process modeling in agricultural systems, promoting their sustainable management. This approach was validated in the Los Naranjos coffee farm in Popayán, Colombia, during the years 2018–2020. The results show that the farm achieved its best energy performance and was more sustainable in 2020, producing 1693 kg/ha of green coffee, with the lowest Unit Emergy Value (UEV; 1.12 × 106 seJ/J) and the highest Emergy Sustainability Index (0.24), for ...

Research paper thumbnail of A low-cost, portable, two-dimensional bioimpedance distribution estimation system based on the AD5933 impedance converter

Research paper thumbnail of Virtual haptic training compared with a conventional exercise for the improvement of upper limb gross motor skills

2017 International Conference on Virtual Rehabilitation (ICVR), 2017

The aim of this paper is to present a comparison between the performance of virtual and conventio... more The aim of this paper is to present a comparison between the performance of virtual and conventional rehabilitation of upper limb gross motor function. To this purpose we define two rehabilitation exercises with a high degree of similarity. The virtual exercise is a computer implementation of the well known game “whack a mole” and the conventional exercise is based on a “shape-sorter” didactic toy. The population involved in the present study, composed of 20 healthy individuals was split into two groups of 10 individuals each. The evaluation of the performance for the two groups shows that the participants using the virtual environment with haptic feedback achieved a greater and more prominent progress than the group performing the conventional exercise. Another participant involved in the study is a female of 52 years with an early stage of Parkinson's disease. In her case the progress obtained with the conventional and with the virtual training sessions were quite similar. However, her progress per session was more prominent than that of the healthy group.

Research paper thumbnail of Affordable Human Gait Analysis Using a Virtual Reality-Based Platform

IEEE Revista Iberoamericana de Tecnologias del Aprendizaje, 2020

This article presents a low-cost educational platform to teach human gait instability assessment ... more This article presents a low-cost educational platform to teach human gait instability assessment using the Lyapunov exponents. The system consists of a cellphone used to measure the acceleration or angular velocity of human body segments, a head-mounted display device, a second cellphone used to visualize the virtual environment developed in Unity3D, a device used to measure the gait speed, and a MATLAB application for data processing. The proposed platform was tested on ten healthy subjects (33.4±9.1 years) under three walking conditions: (i) in a real-world environment, (ii) in a virtual corridor, and (iii) by adding optical flow perturbations to the virtual environment. A survey conducted in the elective class Automatic Systems of Analysis and Capture of Human Gait at Universidad del Cauca, showed the usability of the proposed platform.

Research paper thumbnail of Modelado y control de un sistema de levitación magnética

En este artículo se realizó el modelado y control de un sistema de levitación magnética ( MAGLEV)... more En este artículo se realizó el modelado y control de un sistema de levitación magnética ( MAGLEV). Para ello se construyó un prototipo con materiales de bajo costo con el objetivo de realizar prácticas experimentales para la enseñaanza de sistemas de control en el programa de Ingeniería Física. Los resultados muestran que es posible utilizar el sistema para controlar la posición de una bola mediante una estrategia de control lineal.

Research paper thumbnail of Gait Phase Detection for Lower Limb Prosthetic Devices

Biosystems & Biorobotics, 2018

A prosthesis is an electronic-mechanical device that allows the replacement of a lost limb functi... more A prosthesis is an electronic-mechanical device that allows the replacement of a lost limb functionality. These features require strict control of the energy used for increment the operating time and patient’s safety. In lower limb prosthetic control, it is fundamental to detect each of the phases of the human gait cycle. For example, during the swing phase, the prosthesis must duplicate the movement of the healthy limb, and in load phase, this movement must be adapted. This article presents the algorithm for spatiotemporal human gait parameter using Teager-Kaiser energy operator and its partial validation.

Research paper thumbnail of Comparative Analysis between Computed Torque Control, LQR Control and PID Control for a Robotic Bicycle

The aim of this article is to make a comparison between the performance of a dynamic control and ... more The aim of this article is to make a comparison between the performance of a dynamic control and two linear controllers: PID Control and a Linear Quadratic Regulator (LQR) Control when they are designed for the balance of a Robotic Bicycle. The research is focused on determining the best controller for the robot using two different performance indexes: (i) the standard deviation of the lean angle, (ii) the root mean square value of the signal control. From the experimental test was observed that the LQR control presents a lower energy consumption and lower standard deviation of the error with respect to the PID control; however the dynamic control presents the least standard deviation of the error than the two linear controllers.

Research paper thumbnail of Control of a Robotic Bicycle

This paper presents a simplified second-order dynamic model of the Arduino Engineering Kit roboti... more This paper presents a simplified second-order dynamic model of the Arduino Engineering Kit robotics bicycle. We design and implement a closed loop control strategy, that minimizes the tracking error and rejects disturbances generated by uncertainties and unmodeled dynamics. The proposed controller allows the steering to rotate to the right or to the left to counteract its inclination similar to an inverted pendulum type mobile robot. In addition, performance indexes such as the standard deviation of the error and of the control effort and the ranges of initial angular values for which the robotic bicycle has convergence to the desired equilibrium point. Finally, we tested the proposed control strategy on a real robotic bicycle prototype.

Research paper thumbnail of Modelo Biomecde una Pr´ otesis de Pierna

Research paper thumbnail of A Music Therapy Serious Game with Dynamic Difficulty Adjustment for Stimulating Short-Term Memory

Biosystems & Biorobotics, 2021

Research paper thumbnail of Generación de trayectorias de marcha para un robot humanoide a partir de captura de movimiento

Ciencia en Desarrollo, 2021

En este trabajo se propone un método para adaptar las trayectorias de marcha de un ser humano a ... more En este trabajo se propone un método para adaptar las trayectorias de marcha de un ser humano a un robot humanoide. Las trayectorias obtenidas mediante captura de movimiento sirven como entrada a un generador de trayectorias off-line, llamado filtro dinámico en el que se tienen en cuenta las restricciones cinemáticas y dinámicas necesarias para impedir que el robot caiga mientras camina. Para validar las trayectorias se uso un simulador para el robot Bioloid Premium kit basado en el entorno V-Rep y después se implementaron sobre el robot real. A pesar de que la generación de trayectorias se lleva a cabo fuera de línea, el filtro dinámico es una buena opción para generar trayectorias que permitan mantener la estabilidad del robot.

Research paper thumbnail of Electronic system for step width estimation using programmable system-on-chip technology and time of flight cameras

Research paper thumbnail of A Project-Based Learning Approach to Teach Identification and Control Systems

IEEE Revista Iberoamericana de Tecnologias del Aprendizaje, 2020

This paper presents a teaching tool for modeling and control of dynamical systems using a project... more This paper presents a teaching tool for modeling and control of dynamical systems using a project-based learning approach, which allows engineering and basic science students to develop programming and electronic design skills through the use of fundamental physics. The tool has two main components. The first one is a program that obtains the mathematical model of an electrical circuit from experimental data, and this model is used to design a discrete-time controller. The second component is a C language code generator that takes the controller designed by the first component and implements it on an Arduino board. This tool was tested in the Identification and Simulation undergraduate class at the Universidad del Cauca, proving to be easy to use and motivating for the students within the Industrial Automation Engineering program.

Research paper thumbnail of Estudio de la Dinámica y Control de una Bicicleta Robótica

Revista Mexicana de Física E, 2020

En este trabajo se realiza un estudio de modelo cinemático y dinámico de una bicicleta robótica (... more En este trabajo se realiza un estudio de modelo cinemático y dinámico de una bicicleta robótica (Arduino Engineering Kit) con el propósito de desarrollar algoritmos de control para la estabilización automática de la bicicleta. Se muestra el modelo matemático de la bicicleta mediante la formulación Euler-Lagrange. Este modelo permite el diseño y la implementación de dos estrategías de control para garantizar el equilibrio automático. El estudio de este sistema dinámico se presenta como una excelente oportunidad para integrar las destrezas adquiridas por los estudiantes en materias como física, programación y matemáticas con el propósito de diseñar, modelary controlar sistemas dinámicos.

Research paper thumbnail of Dynamics and Preview Control of a Robotics Bicycle

Advances in Automation and Robotics Research, 2020

This paper presents the dynamic model of the Arduino Engineering Kit robotics bicycle. We design ... more This paper presents the dynamic model of the Arduino Engineering Kit robotics bicycle. We design and implement a closed loop control strategy (preview control), that minimizes the tracking error and rejects disturbances generated by uncertainties and unmodeled dynamics. The preview control is a servo controller that permits the tracking of desired trajectories in the handlebar, maintaining the stability of the bicycle. Finally, we tested the proposed control strategy on a real robotic bicycle prototype.

Research paper thumbnail of Reactive Power Compensation in Mechanical Systems

In this paper the problem of energy consumption in mechanical systems is approached from an elect... more In this paper the problem of energy consumption in mechanical systems is approached from an electrical engineering point of view. To achieve this objective classical concepts in electrical networks theory like apparent power, reactive power and power factor have been extended to mechanical systems. This paper focus on the role of springs in mechanical systems to avoid power oscillations between joint actuators and loads. Such oscillations are a major problem because they unnecessarily increases the mean-square value of joint torques and by consequence Joule effect losses in the actuators. The minimization of these oscillations is known as "reactive power compensation". The main points illustrated in this paper are the fundamental limitations on reactive power compensation and the negative effect on the energy consumption of the harmonic content of the reference trajectory.

Research paper thumbnail of A penalty-based approach for contact forces computation in bipedal robots

2009 9th IEEE-RAS International Conference on Humanoid Robots, 2009

Computation of contact forces is essential for the simulation of mechanical systems with unilater... more Computation of contact forces is essential for the simulation of mechanical systems with unilateral constraints, like bipedal robots. Most methods are based on the rigid body assumption. They can be categorized into constraint-based and penalty-based approaches. In the former, contact forces are computed by solving an optimization problem based on linear or nonlinear complementarity conditions. Unfortunately, these methods cannot be directly applied to articulated systems described in generalized coordinates. In the second approach, spring-damper models are used to minimize interpenetration between the surfaces in contact. The main criticism to penalty approaches are parameter tunning, static friction handling, and the difficulties to treat multiple simultaneous unilateral contacts. In this work we present a new compliant approach based on input-output feedback linearization. The main advantages of the proposed approach are, the spring-damper parameters are independent of the parameters of the system (i.e masses, inertias), no a priori-defined velocity thresholds are required to distinguish between dynamic and static friction, multiple simultaneous unilateral contacts are naturally handled. The proposition has been succesfully applied to the simulation of a 3D bipedal walking robot.

Research paper thumbnail of Distribution of Forces Between Synergistics and Antagonistics Muscles Using an Optimization Criterion Depending on Muscle Contraction Behavior

Journal of Biomechanical Engineering, 2010

In this paper, a new neuromusculoskeletal simulation strategy is proposed. It is based on a casca... more In this paper, a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascade control approach with an inner muscular-force control loop and an outer joint-position control loop. The originality of the work is located in the optimization criterion used to distribute forces between synergistic and antagonistic muscles. The cost function and the inequality constraints depend on an estimation of the muscle fiber length and its time derivative. The advantages of a such criterion are exposed by theoretical analysis and numerical tests. The simulation model used in the numerical tests consists in an anthropomorphic arm model composed by two joints and six muscles. Each muscle is modeled as a second-order dynamical system including activation and contraction dynamics. Contraction dynamics is represented using a classical Hill’s model.

Research paper thumbnail of Dataset for gait analysis and assessment of fall risk for older adults

Research paper thumbnail of A Sinusoidal Current Source for Bioimpedance Applications Based on a Nonlinear Discrete Time Closed Loop Control Algorithm

CIENCIA EN DESARROLLO

Sinusoidal current sources are fundamental components of electronic equipment used in bioimpedanc... more Sinusoidal current sources are fundamental components of electronic equipment used in bioimpedanceanalysis and in electrical impedance tomography. Currently, these sources are mostly implemented asanalog electronic systems. The aim of this paper is to present a new approach to current sources designbased on discrete-time closed-loop control systems. The experimental results are obtained by implementingthe current source in a system of analog and digital programmable blocks, and using as a controllera nonlinear difference equation proposed by the authors. This controller guarantees the convergence ofthe amplitude of the current flowing through the load, towards a user-desired level. This new control lawdoes not require any parametric adjustment nor knowledge of the load . The developed device is able toproduce a sinusoidal current signal of a frequency ranging from 100 Hz to 120 kHz and currents from500 μA to 2 mA. The amplitude error of the current signal remained below 1% for tests...

Research paper thumbnail of A Multidisciplinary Approach Integrating Emergy Analysis and Process Modeling for Agricultural Systems Sustainable Management—Coffee Farm Validation

Sustainability

Agricultural production operates via the existing relationships between nature and economy. Its s... more Agricultural production operates via the existing relationships between nature and economy. Its sustainable development requires tools that provide a broad vision of the energy flows that intervene in these systems, to support the decision-making process in energy management. To quantify the environmental resources and economic inputs involved, emergy analysis has been used, as well as process modeling, to make a detailed record of the system inputs. The research aim is to propose a multidisciplinary approach that integrates emergy analysis and process modeling in agricultural systems, promoting their sustainable management. This approach was validated in the Los Naranjos coffee farm in Popayán, Colombia, during the years 2018–2020. The results show that the farm achieved its best energy performance and was more sustainable in 2020, producing 1693 kg/ha of green coffee, with the lowest Unit Emergy Value (UEV; 1.12 × 106 seJ/J) and the highest Emergy Sustainability Index (0.24), for ...

Research paper thumbnail of A low-cost, portable, two-dimensional bioimpedance distribution estimation system based on the AD5933 impedance converter

Research paper thumbnail of Virtual haptic training compared with a conventional exercise for the improvement of upper limb gross motor skills

2017 International Conference on Virtual Rehabilitation (ICVR), 2017

The aim of this paper is to present a comparison between the performance of virtual and conventio... more The aim of this paper is to present a comparison between the performance of virtual and conventional rehabilitation of upper limb gross motor function. To this purpose we define two rehabilitation exercises with a high degree of similarity. The virtual exercise is a computer implementation of the well known game “whack a mole” and the conventional exercise is based on a “shape-sorter” didactic toy. The population involved in the present study, composed of 20 healthy individuals was split into two groups of 10 individuals each. The evaluation of the performance for the two groups shows that the participants using the virtual environment with haptic feedback achieved a greater and more prominent progress than the group performing the conventional exercise. Another participant involved in the study is a female of 52 years with an early stage of Parkinson's disease. In her case the progress obtained with the conventional and with the virtual training sessions were quite similar. However, her progress per session was more prominent than that of the healthy group.

Research paper thumbnail of Affordable Human Gait Analysis Using a Virtual Reality-Based Platform

IEEE Revista Iberoamericana de Tecnologias del Aprendizaje, 2020

This article presents a low-cost educational platform to teach human gait instability assessment ... more This article presents a low-cost educational platform to teach human gait instability assessment using the Lyapunov exponents. The system consists of a cellphone used to measure the acceleration or angular velocity of human body segments, a head-mounted display device, a second cellphone used to visualize the virtual environment developed in Unity3D, a device used to measure the gait speed, and a MATLAB application for data processing. The proposed platform was tested on ten healthy subjects (33.4±9.1 years) under three walking conditions: (i) in a real-world environment, (ii) in a virtual corridor, and (iii) by adding optical flow perturbations to the virtual environment. A survey conducted in the elective class Automatic Systems of Analysis and Capture of Human Gait at Universidad del Cauca, showed the usability of the proposed platform.

Research paper thumbnail of Modelado y control de un sistema de levitación magnética

En este artículo se realizó el modelado y control de un sistema de levitación magnética ( MAGLEV)... more En este artículo se realizó el modelado y control de un sistema de levitación magnética ( MAGLEV). Para ello se construyó un prototipo con materiales de bajo costo con el objetivo de realizar prácticas experimentales para la enseñaanza de sistemas de control en el programa de Ingeniería Física. Los resultados muestran que es posible utilizar el sistema para controlar la posición de una bola mediante una estrategia de control lineal.

Research paper thumbnail of Gait Phase Detection for Lower Limb Prosthetic Devices

Biosystems & Biorobotics, 2018

A prosthesis is an electronic-mechanical device that allows the replacement of a lost limb functi... more A prosthesis is an electronic-mechanical device that allows the replacement of a lost limb functionality. These features require strict control of the energy used for increment the operating time and patient’s safety. In lower limb prosthetic control, it is fundamental to detect each of the phases of the human gait cycle. For example, during the swing phase, the prosthesis must duplicate the movement of the healthy limb, and in load phase, this movement must be adapted. This article presents the algorithm for spatiotemporal human gait parameter using Teager-Kaiser energy operator and its partial validation.

Research paper thumbnail of Comparative Analysis between Computed Torque Control, LQR Control and PID Control for a Robotic Bicycle

The aim of this article is to make a comparison between the performance of a dynamic control and ... more The aim of this article is to make a comparison between the performance of a dynamic control and two linear controllers: PID Control and a Linear Quadratic Regulator (LQR) Control when they are designed for the balance of a Robotic Bicycle. The research is focused on determining the best controller for the robot using two different performance indexes: (i) the standard deviation of the lean angle, (ii) the root mean square value of the signal control. From the experimental test was observed that the LQR control presents a lower energy consumption and lower standard deviation of the error with respect to the PID control; however the dynamic control presents the least standard deviation of the error than the two linear controllers.

Research paper thumbnail of Control of a Robotic Bicycle

This paper presents a simplified second-order dynamic model of the Arduino Engineering Kit roboti... more This paper presents a simplified second-order dynamic model of the Arduino Engineering Kit robotics bicycle. We design and implement a closed loop control strategy, that minimizes the tracking error and rejects disturbances generated by uncertainties and unmodeled dynamics. The proposed controller allows the steering to rotate to the right or to the left to counteract its inclination similar to an inverted pendulum type mobile robot. In addition, performance indexes such as the standard deviation of the error and of the control effort and the ranges of initial angular values for which the robotic bicycle has convergence to the desired equilibrium point. Finally, we tested the proposed control strategy on a real robotic bicycle prototype.

Research paper thumbnail of Modelo Biomecde una Pr´ otesis de Pierna

Research paper thumbnail of A Music Therapy Serious Game with Dynamic Difficulty Adjustment for Stimulating Short-Term Memory

Biosystems & Biorobotics, 2021

Research paper thumbnail of Generación de trayectorias de marcha para un robot humanoide a partir de captura de movimiento

Ciencia en Desarrollo, 2021

En este trabajo se propone un método para adaptar las trayectorias de marcha de un ser humano a ... more En este trabajo se propone un método para adaptar las trayectorias de marcha de un ser humano a un robot humanoide. Las trayectorias obtenidas mediante captura de movimiento sirven como entrada a un generador de trayectorias off-line, llamado filtro dinámico en el que se tienen en cuenta las restricciones cinemáticas y dinámicas necesarias para impedir que el robot caiga mientras camina. Para validar las trayectorias se uso un simulador para el robot Bioloid Premium kit basado en el entorno V-Rep y después se implementaron sobre el robot real. A pesar de que la generación de trayectorias se lleva a cabo fuera de línea, el filtro dinámico es una buena opción para generar trayectorias que permitan mantener la estabilidad del robot.

Research paper thumbnail of Electronic system for step width estimation using programmable system-on-chip technology and time of flight cameras

Research paper thumbnail of A Project-Based Learning Approach to Teach Identification and Control Systems

IEEE Revista Iberoamericana de Tecnologias del Aprendizaje, 2020

This paper presents a teaching tool for modeling and control of dynamical systems using a project... more This paper presents a teaching tool for modeling and control of dynamical systems using a project-based learning approach, which allows engineering and basic science students to develop programming and electronic design skills through the use of fundamental physics. The tool has two main components. The first one is a program that obtains the mathematical model of an electrical circuit from experimental data, and this model is used to design a discrete-time controller. The second component is a C language code generator that takes the controller designed by the first component and implements it on an Arduino board. This tool was tested in the Identification and Simulation undergraduate class at the Universidad del Cauca, proving to be easy to use and motivating for the students within the Industrial Automation Engineering program.

Research paper thumbnail of Estudio de la Dinámica y Control de una Bicicleta Robótica

Revista Mexicana de Física E, 2020

En este trabajo se realiza un estudio de modelo cinemático y dinámico de una bicicleta robótica (... more En este trabajo se realiza un estudio de modelo cinemático y dinámico de una bicicleta robótica (Arduino Engineering Kit) con el propósito de desarrollar algoritmos de control para la estabilización automática de la bicicleta. Se muestra el modelo matemático de la bicicleta mediante la formulación Euler-Lagrange. Este modelo permite el diseño y la implementación de dos estrategías de control para garantizar el equilibrio automático. El estudio de este sistema dinámico se presenta como una excelente oportunidad para integrar las destrezas adquiridas por los estudiantes en materias como física, programación y matemáticas con el propósito de diseñar, modelary controlar sistemas dinámicos.

Research paper thumbnail of Dynamics and Preview Control of a Robotics Bicycle

Advances in Automation and Robotics Research, 2020

This paper presents the dynamic model of the Arduino Engineering Kit robotics bicycle. We design ... more This paper presents the dynamic model of the Arduino Engineering Kit robotics bicycle. We design and implement a closed loop control strategy (preview control), that minimizes the tracking error and rejects disturbances generated by uncertainties and unmodeled dynamics. The preview control is a servo controller that permits the tracking of desired trajectories in the handlebar, maintaining the stability of the bicycle. Finally, we tested the proposed control strategy on a real robotic bicycle prototype.

Research paper thumbnail of Reactive Power Compensation in Mechanical Systems

In this paper the problem of energy consumption in mechanical systems is approached from an elect... more In this paper the problem of energy consumption in mechanical systems is approached from an electrical engineering point of view. To achieve this objective classical concepts in electrical networks theory like apparent power, reactive power and power factor have been extended to mechanical systems. This paper focus on the role of springs in mechanical systems to avoid power oscillations between joint actuators and loads. Such oscillations are a major problem because they unnecessarily increases the mean-square value of joint torques and by consequence Joule effect losses in the actuators. The minimization of these oscillations is known as "reactive power compensation". The main points illustrated in this paper are the fundamental limitations on reactive power compensation and the negative effect on the energy consumption of the harmonic content of the reference trajectory.

Research paper thumbnail of A penalty-based approach for contact forces computation in bipedal robots

2009 9th IEEE-RAS International Conference on Humanoid Robots, 2009

Computation of contact forces is essential for the simulation of mechanical systems with unilater... more Computation of contact forces is essential for the simulation of mechanical systems with unilateral constraints, like bipedal robots. Most methods are based on the rigid body assumption. They can be categorized into constraint-based and penalty-based approaches. In the former, contact forces are computed by solving an optimization problem based on linear or nonlinear complementarity conditions. Unfortunately, these methods cannot be directly applied to articulated systems described in generalized coordinates. In the second approach, spring-damper models are used to minimize interpenetration between the surfaces in contact. The main criticism to penalty approaches are parameter tunning, static friction handling, and the difficulties to treat multiple simultaneous unilateral contacts. In this work we present a new compliant approach based on input-output feedback linearization. The main advantages of the proposed approach are, the spring-damper parameters are independent of the parameters of the system (i.e masses, inertias), no a priori-defined velocity thresholds are required to distinguish between dynamic and static friction, multiple simultaneous unilateral contacts are naturally handled. The proposition has been succesfully applied to the simulation of a 3D bipedal walking robot.

Research paper thumbnail of Distribution of Forces Between Synergistics and Antagonistics Muscles Using an Optimization Criterion Depending on Muscle Contraction Behavior

Journal of Biomechanical Engineering, 2010

In this paper, a new neuromusculoskeletal simulation strategy is proposed. It is based on a casca... more In this paper, a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascade control approach with an inner muscular-force control loop and an outer joint-position control loop. The originality of the work is located in the optimization criterion used to distribute forces between synergistic and antagonistic muscles. The cost function and the inequality constraints depend on an estimation of the muscle fiber length and its time derivative. The advantages of a such criterion are exposed by theoretical analysis and numerical tests. The simulation model used in the numerical tests consists in an anthropomorphic arm model composed by two joints and six muscles. Each muscle is modeled as a second-order dynamical system including activation and contraction dynamics. Contraction dynamics is represented using a classical Hill’s model.

Research paper thumbnail of Dataset for gait analysis and assessment of fall risk for older adults

Research paper thumbnail of A Sinusoidal Current Source for Bioimpedance Applications Based on a Nonlinear Discrete Time Closed Loop Control Algorithm

CIENCIA EN DESARROLLO

Sinusoidal current sources are fundamental components of electronic equipment used in bioimpedanc... more Sinusoidal current sources are fundamental components of electronic equipment used in bioimpedanceanalysis and in electrical impedance tomography. Currently, these sources are mostly implemented asanalog electronic systems. The aim of this paper is to present a new approach to current sources designbased on discrete-time closed-loop control systems. The experimental results are obtained by implementingthe current source in a system of analog and digital programmable blocks, and using as a controllera nonlinear difference equation proposed by the authors. This controller guarantees the convergence ofthe amplitude of the current flowing through the load, towards a user-desired level. This new control lawdoes not require any parametric adjustment nor knowledge of the load . The developed device is able toproduce a sinusoidal current signal of a frequency ranging from 100 Hz to 120 kHz and currents from500 μA to 2 mA. The amplitude error of the current signal remained below 1% for tests...