Jaime Álvarez

• PhD
• Professor (Full) at Center for Research and Advanced Studies of the National Polytechnic Institute

Today humanoid robots are an object of study since they perform different tasks such as interacting with people and objects using their hands, pick and place tasks, among others, and one of the most studied is walking. The design of walking trajectories works for both humanoid and bipedal robots depending on the used frame, nevertheless, these traj...

Airborne Wind Energy (AWE) systems take advantage of high altitude wind in order to generate electrical energy. One of the challenges when harvesting energy with an AWE system is to deal with strong disturbances such as changes in the wind velocity. This paper proposes a robust trajectory tracking controller for an AWE system, namely a tethered kit...

This article addresses the time-varying leader–follower formation control problem for nonholonomic mobile robots, under communication and visibility constraints. Although the leader–follower formation control under visibility constraints has been studied, the elimination of the off-tracking effect has not been widely addressed yet. In this work, a...

In this paper, a synchronization approach to solve the formation control problem for three differential-drive wheeled mobile robots from a cluster space perspective is studied. In order to solve the individual trajectory tracking task of each mobile robot while maintaining a desired formation, besides the controller at cluster level, another inner...

In this paper, the trajectory tracking problem of multiple quadrotors while maintaining time-varying spatial formations is addressed through a synchronization approach. The aim is to control each quadrotor to track its desired trajectory while its motion is synchronized with the others within the formation to keep a desired time-varying formation....

The presence of parametric uncertainties decreases the performance in controlling dynamic systems such as the DC motor. In this work, an adaptive control strategy is proposed to deal with parametric uncertainties in the speed regulation task of the DC motor. This adaptive strategy is based on a bio-inspired optimization approach, where an optimizat...

Resumen: Se diseña un algoritmo para la evasión de obstáculos, basado en un control conmutado de planeación de senderos, bajo una estructura de trayectorias definidas como una cadena de funciones paramétricas. El control conmutado de planeación de senderos consiste en dos funciones básicas, evasión y seguimiento. La estrategia de control usada para...

Mobile robots with omnidirectional wheels are expected to perform a wide variety of movements in a narrow space. However, kinematic mobility and dexterity have not been clearly identified as an objective to be considered when designing omnidirectional redundant robots. In light of this fact, this article proposes to maximize the dexterity of the mo...

This paper addresses the control problem of master-slave teleoperation of a class of underactuated mechanical systems with communication delays. The core of the proposed solution introduces a suitable coupling matrix, so the complete error dynamics is written in a linear part, and a nonlinear one, for which the matching condition is satisfied. Then...

Optimization methods have shown to be a very important approach for control engineers. They emulate the decision-making ability of a human expert to tune the control gains for a process or system with the formulation and solution of a mathematical optimization problem. In such formulation, evolutionary algorithms (EAs) have been widely used to obta...

In this paper the robust adaptive control of a multicomponent nonideal distillation column is considered. A simple dynamic neural network is used to estimate the distillation column, then a adaptive controller is proposed. Because the approximation capability of dynamic neural network is limited, a sliding mode compensator is addressed. It is shown...

In this paper we report the use of an extension of the Ott-Grebogi-Yorke (OGY) approach for controlling chaos, but instead of using a Poincaré Map we use the First Return Map (FRM) of the generated flow. This allows us to deal with systems whose chaotic attractors has a fractal dimension close to an integer value. The method uses only a measurement...

This document proposes an energetic output improvement of electric drives for induction motors. This modification pointing toward a better energetic output (improving the efficiency) according to the application, and can be made in the most common control algorithms as the Flux Oriented Control (FOC) and the Direct Torque Control (DTC). The experim...

Resumen: En el presente trabajo se desarrolla el modelo dinámico de un robot móvil diferencial con una distribución de masa no uniforme y un controlador por par calculado, en el cual se incluye un controlador auxiliar diseñado con la técnica de backstepping. Se dan condiciones bajo las cuales el sistema en lazo cerrado es estable. Los resultados ob...

Resumen En este trabajo se describe la aplicación de una estructura de control, llamada control por modelo interno (CMI), con la que es posible mejorar el desempeño de sistemas que presentan cierto tipo de holgura mecánica mejor conocida como juego mecánico u holgura (" backlash " , en inglés). Este fenómeno aparece frecuentemente en dispositivos m...

The principal objective of this work is to show that the performance of the control techniques well known like the Direct Torque Control, can be improved by the introduction of an adaptable state observer structure to estimate variables that cannot be easily measured like the magnetic flux and torque; and that also, allow at the same time to know t...

This paper proposes a synergetic approach to design a planar parallel robot with its control system. In this proposal, the design problem is stated as a dynamic optimization problem with dynamic and static constraints on both the robot parameters and the control input to the robot. Control parameterization via PID controllers is used to rewrite the...

In this paper, a robust formulation for the structure-control design of mechatronic systems is developed. The proposed robust approach aims at minimization of the sensitivity of the nominal design objectives with respect to uncertain parameters. The robust integrated design problem is established as a nonlinear multiobjective dynamic optimization o...

This work presents the development of an experimental platform for remote control of Internet-connected systems. The aim is to describe and to evaluate this platform, which exhibits some interesting peculiarities w.r.t. the mainstream literature: real-time support over the Internet, capacity to handle loss/disorder of packets, and varying delays. P...

A mobile manipulator is a robotic arm mounted on a mobile robot; a particular example is a manipulator arm on a mobile robot with differential traction. Mobile manipulators have many advantages over stationary manipulator, such as a larger work space than a stationary manipulator could have in practice. This paper shows a systematic approach to mod...

A mobile manipulator is a robotic arm mounted on a mobile robot; a particular example is a manipulator arm on a mobile robot with differential traction. Mobile manipulators have many advantages over stationary manipulator, such as a larger work space than a stationary manipulator could have in practice. This paper shows a systematic approach to mod...

In this paper the formulation of the optimal design for wheel location of an omnidirectional mobile robot is proposed as an optimization problem. The empirical com-parison of the SQP algorithm and eight different DE variants for this particular optimization problems is presented. The importance of using heuristic approaches in real world optimizati...

The introduction of mobile manipulators on unstructured environments brings many interesting research problems, such as their modeling and control. This paper shows a systematic approach to modeling mobile manipulators that transforms the problem to the modeling of a stationary manipulator with nonholonomic kinematic constraints on the joints. It i...

Parametric reconfiguration plays a key role in non-iterative concurrent design of mechatronic systems. This is because it allows the designer to select, among different competitive solutions, the most suitable without sacrificing sub-optimal characteristics. This paper presents a method based on an evolutionary algorithm to improve the parametric r...

Using the underlying idea of the most widely accepted controller for power converters, the current-mode control, a new dynamical and sliding-mode control for dc–dc power converters, is proposed. The controller requires only voltage measurements; is easy to design; is robust under load and input voltage variations, exhibits fast response and does no...

Mobile manipulators have attracted a lot attention lately because they have many advantages over stationary manipulator, such as larger a work space than a stationary manipulator could have in practice. However, the proposed methods in the state of the art to obtain the kinematic model of a mobile manipulator are based in modeling separately the mo...

In this paper a robust integrated design methodology for dynamic systems is formulated. The proposed methodology can be applied to design both the system and the control parameters, thus allowing for an optimization based integrated system and controller design under uncertainties or unknown parameters. This design methodology is used to simultaneo...

The present work deals with the use of a constraint-handling differential evolution algorithm to solve a nonlinear dynamic optimization problem (NLDOP) with 51 decision variables. A novel mechatronic design approach is proposed as an NLDOP, where both the structural parameters of a non-redundant parallel robot and the control parameters are simulta...

Resumen— En el presente trabajo se reporta una revisión de la literatura existente con respecto a los manipuladores móviles, limitando la investigación a resultados en el área de control donde el movimiento de los manipuladores móviles es simultáneo en la base móvil y el brazo manipulador; además sólo se consideran los manipuladores móviles que son...

This paper presents a formation control of nonholonomic mobile robots for a leader-follower scheme. The control design is based on a backstepping recursive procedure together with passivity feedback equivalence and sliding mode techniques. In particular, the sliding mode technique allows to get a robust formation control in the sense that it dimini...

The boost inverter is a device that is able to generate a sinusoidal voltage with an amplitude larger than the input voltage. Based on the idea of indirectly controlling the output voltage through the inductor current, a dynamical sliding-mode controller for the boost inverter is proposed in this paper. Unlike the usual approach of generating a sin...

A dynamic design approach for a mechatronic system called task based mechatronic system design approach (TBMSDA) is stated as a nonlinear dynamic optimization problem (NLDOP) and it is solved by using a differential evolution technique. The design of a parallel robot is carried out by this approach which integrates in a simultaneous way both the st...

An interesting problem in robotics is to minimize the required time to force a manipulator to travel between two specific points (positioning time). In this paper a concurrent structure-control redesign approach is proposed in order to find the minimum positioning time of an underactuated robot manipulator, by considering a synergetic combination b...

In this paper, the integrated design of a parallel robot and its controller is stated as a nonlinear dynamic optimization problem (NLDOP), where the robot structural parameters and the controller gains are simultaneously found in order to track a desired trajectory with singularity avoidance. The dynamics of the parallel robot, which is nonlinear d...

This paper deals with the problem of time-delay telecontrol of a class of under-actuated mechanical systems (UMS) in a master-slave configuration. This problem has been solved by designing some discontinuous causal compensators which have proved by formal stability analysis to guarantee position coordination of the mechanisms and to allow good forc...

Se propone una metodología de rediseño paramétrico de sistemas no lineales para control en tiempo mínimo sin restricciones de trayectoria en los estados y con control acotado. Tal metodología consiste en plantear el problema de rediseño óptimo como uno de optimización dinámica, permitiendo encontrar simultáneamente los parámetros estructurales del...

A parametric redesign methodology of nonlinear systems for minimum-time control without constraints on the state trajectory and bounded control is proposed. This methodology states the optimum redesign problem as a dynamic optimization one. This methodology simultaneously finds both the structural parameters of the system and the switching interval...

In this paper we present the mathematical model for a MagLev system with 3 DOFs. A dynamical sliding mode controller is proposed to regulate the levitation to a desired position and stabilize the rotational movements. Finally the mathematical model and the controller are validated and evaluated by means of some experimental tests.

In this paper, a concurrent design methodology to formulate the mechatronic design problem is presented. The methodology proposes to state the mechatronic design problem as a dynamic optimization problem. In order to explain the methodology, the concurrent design of pinion–rack continuously variable transmission (CVT) is carried out. Two optimizati...

This paper deals with the problem of time-delay telecontrol of a class of underactuated mechanical systems (UMS) in a master-slave configuration. This problem has been solved by designing some discontinuous causal compensators which have proved by formal stability analysis to guarantee position coordination of the mechanisms and to allow good force...

Generally, sliding-mode controllers have to be modified to achieve a constant switching frequency or at least to have an upper limit for it. A family of sliding-mode controllers easy to implement is proposed in this paper. If a controller has the form specified in this paper then it can be implemented using a pulse-width modulator assuring a consta...

In this chapter, we present an evolutionary approach to solve a novelmechatronic design problemof a pinion-rack continuously variable transmission (CVT).This problem is stated as a multiobjective optimization problem, because we concurrently optimize the mechanical structure and the controller performance, in order to produce mechanical, electronic...

A sliding-mode control using a new sliding surface just depending on the output voltage is proposed for the boost inverter. It overcomes some disadvantages that the traditional sliding-mode control has. The surface is derived from the current-mode control idea of indirectly controlling the output voltage through the inductor current. The controller...

An experimental evaluation of a dynamical sliding-mode control for power converters which has been recently proposed is presented in this paper. This controller is endowed with notable characteristics predicted in theory and observed in simulations, among others: it is robust under load and input voltage variations and does not require current meas...

This paper presents a dynamic optimization approach based on the differential evolution (DE) strategy which is applied to the concurrent optimal design of a continuously variable transmission (CVT). The structure-control integration approach is used to state the concurrent optimal design as a dynamic optimization problem which is solved using the C...

In this paper, the nonlinear mathematical model with five DOFs of a magnetic levitation system is developed and analyzed. Then a second order sliding mode controller is proposed to regulate the levitation to a desired position, stabilize the other 4 DOFs in the nonlinear system and compensate the unknown increments on the load. Simulation results a...

Se presenta el diseño mecatrónico de un prototipo sistema masa-resorte rotacional para fines experimentales y el diseño e implementación de un controlador Proporcional Integral Generalizado (GPI) basado en el modelo del sistema.

The passivity-based control has been proposed to control different non-linear systems, but practical implementation aspects have not been discussed on most of them. One of those systems is the buck inverter. In some applications it is necessary the boosting capability additionally to the inversion capability, therefore a boost inverter has been pro...

We present the construction of a model of the human skull using the Finite Element Method. The geometry is given by 124 MRI images of the human head. The MRI images are digitized and the data are input into the Ansys Software (Ansys Inc) version 7.0. The model consists of 39,538 elements and 74,781 nodes. The physical properties that were considere...

An alternative method for mechatronic systems concurrent design using the dynamic optimization framework is presented in this paper. A dynamic optimization problem (DOP) is proposed to obtain the optimal mechanical parameters values of a continuously variable transmission (CVT), where the kinematic and dynamic models are considered besides the perf...

Using the underlying idea of the current-mode control, a new dynamical, sliding-mode control for the boost dc-dc converter is proposed. Such controller is easy to design, robust under load and input voltage variations, exhibits fast response, does not depend on the load (although a knowledge of the load range is necessary to tune the controller), r...

This paper describes the development of an experimental platform for robotic teleoperation via Internet. It is obtained by adding Internet capabilities to an industry-standard DSP board, available in many universities and research centers

In this paper, the nonlinear mathematical model with five DOFs (degrees-of-freedom) of a magnetic levitation system is developed and analyzed. Then a second order sliding mode controller is proposed to regulate the levitation to a desired position, stabilize the other 4 DOFs in the nonlinear system and compensate the unknown increments on the load....

This paper is concerned with the design and experimental test of a controller-observer scheme for the angular position of a permanent magnet (PM) stepper motor. First, a discrete-time model of a class of nonlinear singularly perturbed systems is derived which is used to design a controller using the sliding mode technique.This design is then applie...

An experimental setup is presented for the implementation and testing of a rotor position control of a permanent magnet (PM) stepper motor that does not need the measurement of mechanical signals. The control scheme proposed here has been designed using the singular perturbation and sliding mode methodologies.

In this paper, a phase space reconstruction technique and the estimation of the maximum Lyapunov exponent allow to show that the long-term dynamics of a two-link, planar, underactuated manipulator may be chaotic. The problem of stabilizing unstable periodic orbits (UPO's) embedded in the system chaotic set (attractor) is considered. A time delay fe...

Resumen— Mediante la técnica de reconstrucción de atractores y la estimación del máximo exponente de Lyapunov, se muestra que la dinámica a largo plazo de un manipulador planar subactuado puede ser caótica. Se considera entonces el problema de estabiliza orbitas periódicas inestables (OPI's) inmersas en el conjunto invariante caótico del sistema y...

Applying attractor reconstruction techniques and other chaotic measurements, it is shown that the long-term dynamics of a vertical, underactuated, two-degrees-of-freedom robot called Pendubot may exhibit complex dynamics including chaotic behavior. These techniques use only the measurement of some available variable of the system, and the resulting...

Chaos control has been an expanding research area in the last decade, therefore a great amount of techniques have been developed for controlling or suppressing chaos. Some of the most popular techniques are the so-called parametric perturbation methods [4]. These techniques use an accessible system parameter to be changed dynamically to stabilize o...

The boost inverter is a latterly proposed device that is used in applications like uninterruptible power supplies (UPS) and photovoltaic systems. Its main feature is the ability to invert and boost at a single stage. In this paper, the implementation of a recently proposed sliding-mode-based, nonlinear controller for the boost inverter is presented...

In this paper a controller based on the variable structure theory is analyzed: the sliding mode control. The sliding mode control was proposed to control dc/dc converters, due to the good characteristics introduced to the complete system. In order to regulate the output voltage, the sliding mode control require a current loop in order to assure the...

The passivity-based control has been proposed to control different non-linear systems, but practical implementation aspects have not been discussed on most of them. One of those systems is the buck inverter. In some applications it is necessary the boosting capability, additional to the inversion capability, therefore a boost inverter has been prop...

Recently, attempts have been made to construct actuators with similar behaviour to natural muscles. However the results have been inadequate for application to practical prostheses. For example, muscle wire, which has too low an efficiency to be powered by batteries and McKibben muscles which require two power supplies, one electric and one pneumat...

A control scheme based on the singular perturbations methodology and the sliding mode technique is designed for a permanent magnet (PM) stepper motor. The control scheme designed allows the angular velocity and position of the motor to track some given reference trajectories and it is based on the reconstruction of those signals from direct measure...

The parallel prosthesis here described is a novel design that overcomes several problems of traditional serial prosthesis as the developed force, the weight of the prosthesis and the use of the available space. In this work the design, the analysis of the statical and kinematical models and the performance of the prosthesis are discussed. Among the...

The sliding mode control of the boost converter is revisited. Several sliding surfaces are presented and analyzed. Some of the surfaces presented do not depend on the circuit load, eliminating the necessity to measure the current measurement. The analysis presented is based on the switching model of the circuit instead of the average model typicall...

Because stable chronic recordings of electromyographic (EMG) signals are being required in the clinical practice, electrical impedance in the electrode–skin interface and the electrode–muscle location, must be maintained unmodified. However, because of some factors, these requirements have not been completely fulfilled. Implantable electrodes repre...

This paper presents a simplified sinusoidal uninterruptible power supply (UPS) system. The proposed scheme includes features such as high power factor, low total harmonic distortion and good dynamic response at the AC output voltage. In addition, the scheme has the desirable characteristics, of high efficiency, simple circuit and low cost compared...

The design of a stabilizing feedback control law for singularly perturbed discrete-time system is made by decomposing it into the design of slow and fast controllers which are combined to form the composite control. This approach is applied to the model of a permanent magnet (PM) stepper motor.

In this paper the problem of regulation of an underactuated planar 2R manipulator is solved by tracking appropriate planned trajectories. A class of parametric trajectories is propossed to reach a desired configuration. The parameters of the trajectories are found by using an optimization algorithm. Besides, a feedback control is proposed to regula...

An underactuated system is a kind of non-autonomous robotic system in which there are more links than actuators. The complexity of the dynamical behavior of these systems allows a wide variety of steady-state responses. The reconstruction of attractors based on time series obtained from measurements of one of the variables of a two-link, planar, un...

A non-linear controller-observer scheme for the output tracking of a class of non-linear singularly perturbed systems based on a two-time scale sliding-mode technique and a high gain estimator, is presented. An analysis of stability of the resultant closed-loop system is given. The proposed scheme is applied to the model of a two degrees of freedom...

A new controller that uses the boost circuit as a DC-to-AC converter is proposed. It combines a classical and simple procedure used to accomplish the DC-to-DC conversion with a nonlinear control algorithm such that it is possible to estimate a bound on the steady state tracking error. A way to calculate the inductor and capacitor values ensuring a...

The problem of regulation of an underactuated planar 2R manipulator is solved by tracking appropriated off-line planned trajectories. A class of parametric trajectories is proposed to reach a desired configuration. An optimization algorithm is proposed to find the parameters. Besides, a feedback control is proposed to regulate the manipulator under...

This paper is concerned with the design of a controller-observer scheme for the exponential stabilization of a class of singularly perturbed nonlinear systems based on sliding-modes techniques and nonlinear observers. Under the assumption that only the fast state is available for measurement, an observer design is presented in order to estimate the...

Nowadays, myoelectric prostheses for replacement above elbow are serial mechanisms driven by a DC motor and they include only one active articulation for the elbow. Parallel mechanisms are more robust and produce a greater force than serial mechanisms since every actuator participates in the desired movement of the system. Calculating the position...

This paper is concerned with the design of a controller-observer scheme for the exponential stabilization of a class of singularly perturbed nonlinear systems. The controller design uses a sliding mode technique and is divided in two phases: slow feedback control and fast feedback control so that a final composite control is obtained. Assuming that...

The paper addresses the vibration control problem in two different mechanical systems affected by external vibrations. The methodology starts from a proper design of passive dynamic vibration absorbers, which are transformed into active absorbers by the addition of extra actuated degrees of freedom, leading to nonlinear dynamical systems. The activ...

The work describes the attenuation problem of vibrations affecting a nonlinear oscillatory mechanical system using passive and active vibration control methods based on nonlinear techniques. The mechanical system consists of an oscillating rigid bar coupled to a passive absorber. The undesirable vibration is a harmonic torque, with variable frequen...

It is shown how a very simple procedure of time reversal can solve, in a much easier way than other techniques, an important problem arising in some control strategies of two conventional DC-to-DC switched power converters used to generate an alternate voltage signal: the boost and buck-boost circuits. This problem is related to the non-minimum pha...

In this paper, an analysis and experimental study of three kinds of inverters are presented. Beginning with the traditional full-bridge buck inverter; followed by two different inverter approaches, the boost and buck boost ones. These last two converters have the property of producing an output voltage higher or lower than the input voltage additio...

The problem of stabilization of a class of underactuated systems by using backstepping is considered. To use the backstepping technique a suitable change of coordinates is constructed. Using backstepping a simple control law is proposed; this control law ensures the origin is asymptotically stable. The acrobot system is used to illustrate the appli...

A compensation strategy for nonlinear input time delay systems is considered in this work. The regulation problem is addressed by approximating a noncausal feedback that solves the problem by a nonanticipative one. This is done by considering a passivity based scheme proposed originally for nonlinear systems free of delays

The control problem of a multicomponent nonideal distillation column is proposed by using a dynamic neural network approach. The holdup, liquid and vapor flow rates are assumed to be time-vaying (nonideality). The technique proposed in this paper is based on two central notions: a dynamic neural identifier and a neuro-controller for output trajecto...

The authors propose a design of a myoelectric prosthesis with two active and one passive degrees of freedom to fit on a limb with an above elbow amputation. It will be controlled by myoelectric electrodes implanted directly on the muscle surface

In this paper, the analysis and experimental study of three kinds of inverters are presented, beginning with the traditional full bridge buck inverter, followed by two different inverter approaches, the boost and buck boost ones. This last two converters have the property of produce an output voltage higher or lower than the input voltage additiona...

The purpose of the work is the study of the state prediction problem related with a class of single-input single-output linear time-delay systems. A modification of the classical Smith predictor scheme is proposed for a large class of time delay systems in the sense that we allow time-delays not only in the input signal but also in the state of the...

A new method for multiobjective dynamic optimization of discrete time systems is proposed. As a result a stagewise algorithm for such a problem is obtained. The algorithm solves a one stage multiobjective programming subproblem with general constraints at each time step. Hence, the dimension of the decision variables in each subproblem is smaller t...

The long time for getting an acceptable response in myoelectric prosthesis has been a problem. Thanks to DSP processors, the myoelectric signal (MES) processing time has had a drastic reduction. This paper describes a control unit for a myoelectric prosthesis using statistic variables related to contraction force. ANOVA analysis was used to seek th...

This paper describes: (i)a neural network structure referred as simple recurrent neural network (SRNN), (ii)a learning algorithm based on the optimization layer by layer method for the SRNN and (iii)the SRNN applications for controlling both a linear and a nonlinear dynamic system. The main objectives of the SRNN described are: (i) to show the capa...

In this paper some critical aspects for the design of sliding mode control applied to the boost inverter are presented, including a theoretical analysis and the implementation of the control strategy. The SMC has been proposed in different papers as an option to improve the dynamic response of the electronics circuit. In this paper several design i...