A method for solving the complete dynamic problem in robots with rigid links and ideal joints usi... more A method for solving the complete dynamic problem in robots with rigid links and ideal joints using the Gibbs-Appell equations as starting point is presented. The inverse dynamic problem is solved through a algorithm OðnÞ, where tensor notation is used. The terms of the generalized inertia matrix are calculated by means of the Hessian of the Gibbs function with respect to generalized accelerations, and a recursive algorithm of order Oðn 2 Þ is developed. Proposed algorithms are computationally efficient for serial-robots with moderately large numbers of joints. The numerical stability of the proposed algorithms is analyzed and compared with those of other methods by the use of numerical examples. Ó 2002 Elsevier Science Ltd. All rights reserved.
Mechanics Based Design of Structures and Machines, Nov 10, 2008
Advanced model-based control schemes and the solution of the direct dynamic problem require accur... more Advanced model-based control schemes and the solution of the direct dynamic problem require accurate knowledge of the dynamic parameters of robotic systems, mainly the inertial properties of the links and the friction parameters at the kinematic joints. A well-known and a very useful tool for their determination is through a dynamic identification process. Normally, in this process, only a subset
This paper describes a method for calculating the vectorial kinematic parameters of 3D human move... more This paper describes a method for calculating the vectorial kinematic parameters of 3D human movement by stereophotogrammetry, with special emphasis on an accurate characterization of the Instantaneous Helical Axis. That method is applied to the measure of trunk flexion in sitting posture, the results being interpreted in biomechanical terms, and compared to the mechanical design of articulated work chairs. The axes of pelvic and thoracic movements are found to be located above the seat plane, and to displace vertically as trunk is being flexed, contrary to the usually fixed axes of chairs below the seat. This leads to some discussion about ergonomic shortcomings of chair design for dynamic sitting.
This paper presents a model to determine the optimal average path traced by the instantaneous scr... more This paper presents a model to determine the optimal average path traced by the instantaneous screw axis (ISA) of human joints in cyclical motions with one functional degree of freedom. The experimental determination of the ISA is very sensitive to experimental errors, artifacts and natural intrasubject variability. These sources of variability are strongly and nonlinearly amplified when calculating the ISA, which may lead to erratic results and nega-tively affects the estimation of an average representation of motion. The proposed method eliminates the need to calculate the ISA from the instantaneous, time-dependent kinematic variables (positions, angles and their time derivatives). For this, we represent the motion magnitudes (measured over several cycles) as functions of a single joint position variable. In other words, we move the problem from the time domain to the geometric domain. Thus an average trajectory over the range of motion can be obtained for each position and veloci...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
In this paper the dynamic parameter identification of parallel robots starting from the measureme... more In this paper the dynamic parameter identification of parallel robots starting from the measurement of positions and forces in the actuators is addressed. Methods for obtaining the time derivatives from the measurement of the angular displacement are evaluated. The procedures used are: a) Local Fitting, b) Finite Fourier series and c) Central differences. The identification is carried out by means of a linear model, with respect to the inertial parameters, obtained from the Newton-Euler equations. Linear models are used for friction modelling in the robot joints. Finally the parameter identification is evaluated experimentally over a 3-RPS parallel robot.
Parallel robots have been a very active research field over the last 20 years. Compared to serial... more Parallel robots have been a very active research field over the last 20 years. Compared to serial robots, parallel robots have essentially two well-known advantages such as a greater precision in positioning and an increased rigidity with respect to the relationship between size and work load limit. The main drawbacks of parallel robots are their small workspace and also specific problems related to control planning.
In this paper, the design, characteristics, kinematics and dynamics of a rehabilitation low-cost ... more In this paper, the design, characteristics, kinematics and dynamics of a rehabilitation low-cost parallel robot developed at the Universitat Politècnica de Valencia have been presented. Several position and force controllers have been tested to ensure accurate results. An orthopedic boot, instrumented with a force sensor, has been placed over the platform of the parallel robot with the aim of perform exercises for sprained ankles. Passive, active-assistive and active-resistive exercises have been implemented training dorsi/plantarflexion, inversion and eversion ankle movements. To implement the controllers, the component-based middleware Orocos has been used. Its advantage over other solutions is that all the scheme control is implemented in modular way. These modules are independent and can be configured and reconfigured in both configuration and runtime. By this way, no specific knowledge is needed by, for example, medical personnel to carry out rehabilitation exercises using this low-cost parallel robot. The integration between Orocos and ROS, with a CAD model displaying in real-time the actual position of the rehabilitation robot, has allowed the development of a teleoperation application. In addition, by means of a WiiMote (or any other Bluetooth device), a teleoperating rehabilitation exercise can be realized by a specialist.
CISM International Centre for Mechanical Sciences, 2000
ABSTRACT A path planning among obstacles is presented as applied to a robot of PUMA 560 type with... more ABSTRACT A path planning among obstacles is presented as applied to a robot of PUMA 560 type with mobile base. From two given configurations – the initial and goal ones – a configuration space is calculated. The robot configurations are expressed in terms of fully Cartesian co-ordinates and are obtained by solving nonlinear optimization problems between adjacent configurations, a variety of constrains is considered in order to take into account different real operation problems. The path is selected from a weighted graph associated to the map of feasible robot configurations. A search algorithm has been used to minimize an objective function in order to obtain a sequence of robot configurations between the initial and goal ones.
CISM International Centre for Mechanical Sciences, 2010
In this paper, an approach for solving the forward dynamic problem by using identified parameters... more In this paper, an approach for solving the forward dynamic problem by using identified parameters is presented. A comparison between the identified models; the so-called reduced model and the complete model, and a model with dynamic parameters obtained by a CAD approach is carried out. The results show that the reduced model, obtained based on a set of so-called relevant parameters, is closely related to the actual system response when compared with the other two models.
Revista Iberoamericana de Automática e Informática Industrial RIAI, 2013
La complejidad actual de los sistemas robotizados y de las aplicaciones queéstos deben realizar r... more La complejidad actual de los sistemas robotizados y de las aplicaciones queéstos deben realizar requiere que los robots dispongan de un control automático que permita la ejecución de las distintas tareas que forman parte del algoritmo de control y que tenga en cuenta cuestiones relacionadas por ejemplo con la periodicidad, el modo de ejecución, el hardware que se utilizará, etc. Para el desarrollo de este tipo de aplicaciones de control en losúltimos años se tiende a la programación basada en componentes puesto queésta permite obtener código reusable. Así mismo también se está incrementando la utilización de middlewares que permiten la abstracción de los sistemas operativos, el soporte de tiempo real y la infraestructura de comunicaciones. En el presente artículo se propone la utilización de un middleware orientado especialmente a la robótica: OROCOS. Así se describe cómo haciendo uso de una de sus librerías, Orocos Toolchain, se han desarrollado una serie de componentes correspondientes a distintos algoritmos para el control dinámico de robots, aplicándose a un robot paralelo de 3 grados de libertad (DOF). Copyright c 2012 CEA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
This paper describes a method for calculating the vectorial kinematic parameters of 3D human move... more This paper describes a method for calculating the vectorial kinematic parameters of 3D human movement by stereophotogrammetry, with special emphasis on an accurate characterization of the Instantaneous Helical Axis. That method is applied to the measure of trunk flexion in sitti ng posture, the results being interpreted in biomechanical terms, a nd compared to the mechanical design of articulated work
ABSTRACT In this article a collision-free robot path planning procedure is presented in which a m... more ABSTRACT In this article a collision-free robot path planning procedure is presented in which a manipulability index has been included as one of the optimality criteria when generating the configuration space. From the set of collision-free configurations, a standard algorithm for obtaining optimal trajectories has been considered, taking into account the dynamical robot characteristics. It has been analyzed the effect of the manipulability index in parameters such as the total time that is necessary to perform the trajectory, while the characteristics of the actuators are taken into account.
ABSTRACT Abstract. In this paper a parallel-populations genetic algorithm procedure is presented ... more ABSTRACT Abstract. In this paper a parallel-populations genetic algorithm procedure is presented for the obtainment of minimum-time trajectories for industrial robots. This algorithm is fed in first place by a sequence of configurations then cubic spline functions are used for the construction of joint trajectories for industrial robots. The algorithm is subjected to two types of constraints: (1) Physical constraints on joint velocities, accelerations, and jerk. (2) Dynamic constraints on torque, power, and energy. Comparison examples are used to evaluate the method with different combinations of crossover and mutation.
When dealing with the development of accurate robot dynamic models, the estimation and validation... more When dealing with the development of accurate robot dynamic models, the estimation and validation of the dynamic parameters through experiments becomes necessary. One of the most important objectives to achieve in the design of the experiment, aimed at identification, is to properly excite the system so that the unknown parameters can be accurately estimated. It is customary to find proper excitations optimizing the observation matrix of the model w.r.t. a certain criterion. In this paper the suitability of some trajectory optimization criteria are evaluated for parallel robots. Moreover, a multicriteria algorithm is proposed in order to reduce the deficiencies derived from the single criterion optimization.
ABSTRACT The identification of dynamic parameters in low-mobility mechanical systems is addressed... more ABSTRACT The identification of dynamic parameters in low-mobility mechanical systems is addressed and applied to short long arm (SLA) front car suspension. The main goal of the identification technique is to obtain, from experimental measurements, the values of those dynamic parameters (masses, location of the centre of masses, terms of the inertial matrix of the links, constant friction terms and elastic and viscous damping constant terms) that affect the dynamic behaviour of the system. Moreover, additional but important information that could be obtained from the procedure is related to the weight of those terms inside the dynamics of the system, so that simplified dynamic models based on relevant and well-identified parameters can be established. First, a systematic procedure will be presented for obtaining the equations of motion in a linear form with regard to the dynamic parameters to be identified. The main drawbacks related to the identification of parameters in low-mobility mechanisms will be pointed out, mainly the difficulty of determining a natural cutoff point into the singular values of the observation matrix which allows us to determine the true dimension of the set of base parameters and of obtaining an observation matrix well conditioned from the numerical point of view that allows an identification in the presence of measurement error. The procedure proposed for overcoming these problems will be based on the development of symbolic relationships among the physical parameters in order to determine the true rank of the observation matrix and on the consideration of a reduced subset of the base parameters set. These relevant parameters will be selected according to their influence on the dynamic behaviour of the mechanical system. A virtual benchmark will be used for testing purposes. The dynamic models based on relevant parameters show a better adjustment than the complete ones, mainly when the level of noise in the measurements used in the identification process increases.
A method for solving the complete dynamic problem in robots with rigid links and ideal joints usi... more A method for solving the complete dynamic problem in robots with rigid links and ideal joints using the Gibbs-Appell equations as starting point is presented. The inverse dynamic problem is solved through a algorithm OðnÞ, where tensor notation is used. The terms of the generalized inertia matrix are calculated by means of the Hessian of the Gibbs function with respect to generalized accelerations, and a recursive algorithm of order Oðn 2 Þ is developed. Proposed algorithms are computationally efficient for serial-robots with moderately large numbers of joints. The numerical stability of the proposed algorithms is analyzed and compared with those of other methods by the use of numerical examples. Ó 2002 Elsevier Science Ltd. All rights reserved.
Mechanics Based Design of Structures and Machines, Nov 10, 2008
Advanced model-based control schemes and the solution of the direct dynamic problem require accur... more Advanced model-based control schemes and the solution of the direct dynamic problem require accurate knowledge of the dynamic parameters of robotic systems, mainly the inertial properties of the links and the friction parameters at the kinematic joints. A well-known and a very useful tool for their determination is through a dynamic identification process. Normally, in this process, only a subset
This paper describes a method for calculating the vectorial kinematic parameters of 3D human move... more This paper describes a method for calculating the vectorial kinematic parameters of 3D human movement by stereophotogrammetry, with special emphasis on an accurate characterization of the Instantaneous Helical Axis. That method is applied to the measure of trunk flexion in sitting posture, the results being interpreted in biomechanical terms, and compared to the mechanical design of articulated work chairs. The axes of pelvic and thoracic movements are found to be located above the seat plane, and to displace vertically as trunk is being flexed, contrary to the usually fixed axes of chairs below the seat. This leads to some discussion about ergonomic shortcomings of chair design for dynamic sitting.
This paper presents a model to determine the optimal average path traced by the instantaneous scr... more This paper presents a model to determine the optimal average path traced by the instantaneous screw axis (ISA) of human joints in cyclical motions with one functional degree of freedom. The experimental determination of the ISA is very sensitive to experimental errors, artifacts and natural intrasubject variability. These sources of variability are strongly and nonlinearly amplified when calculating the ISA, which may lead to erratic results and nega-tively affects the estimation of an average representation of motion. The proposed method eliminates the need to calculate the ISA from the instantaneous, time-dependent kinematic variables (positions, angles and their time derivatives). For this, we represent the motion magnitudes (measured over several cycles) as functions of a single joint position variable. In other words, we move the problem from the time domain to the geometric domain. Thus an average trajectory over the range of motion can be obtained for each position and veloci...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
In this paper the dynamic parameter identification of parallel robots starting from the measureme... more In this paper the dynamic parameter identification of parallel robots starting from the measurement of positions and forces in the actuators is addressed. Methods for obtaining the time derivatives from the measurement of the angular displacement are evaluated. The procedures used are: a) Local Fitting, b) Finite Fourier series and c) Central differences. The identification is carried out by means of a linear model, with respect to the inertial parameters, obtained from the Newton-Euler equations. Linear models are used for friction modelling in the robot joints. Finally the parameter identification is evaluated experimentally over a 3-RPS parallel robot.
Parallel robots have been a very active research field over the last 20 years. Compared to serial... more Parallel robots have been a very active research field over the last 20 years. Compared to serial robots, parallel robots have essentially two well-known advantages such as a greater precision in positioning and an increased rigidity with respect to the relationship between size and work load limit. The main drawbacks of parallel robots are their small workspace and also specific problems related to control planning.
In this paper, the design, characteristics, kinematics and dynamics of a rehabilitation low-cost ... more In this paper, the design, characteristics, kinematics and dynamics of a rehabilitation low-cost parallel robot developed at the Universitat Politècnica de Valencia have been presented. Several position and force controllers have been tested to ensure accurate results. An orthopedic boot, instrumented with a force sensor, has been placed over the platform of the parallel robot with the aim of perform exercises for sprained ankles. Passive, active-assistive and active-resistive exercises have been implemented training dorsi/plantarflexion, inversion and eversion ankle movements. To implement the controllers, the component-based middleware Orocos has been used. Its advantage over other solutions is that all the scheme control is implemented in modular way. These modules are independent and can be configured and reconfigured in both configuration and runtime. By this way, no specific knowledge is needed by, for example, medical personnel to carry out rehabilitation exercises using this low-cost parallel robot. The integration between Orocos and ROS, with a CAD model displaying in real-time the actual position of the rehabilitation robot, has allowed the development of a teleoperation application. In addition, by means of a WiiMote (or any other Bluetooth device), a teleoperating rehabilitation exercise can be realized by a specialist.
CISM International Centre for Mechanical Sciences, 2000
ABSTRACT A path planning among obstacles is presented as applied to a robot of PUMA 560 type with... more ABSTRACT A path planning among obstacles is presented as applied to a robot of PUMA 560 type with mobile base. From two given configurations – the initial and goal ones – a configuration space is calculated. The robot configurations are expressed in terms of fully Cartesian co-ordinates and are obtained by solving nonlinear optimization problems between adjacent configurations, a variety of constrains is considered in order to take into account different real operation problems. The path is selected from a weighted graph associated to the map of feasible robot configurations. A search algorithm has been used to minimize an objective function in order to obtain a sequence of robot configurations between the initial and goal ones.
CISM International Centre for Mechanical Sciences, 2010
In this paper, an approach for solving the forward dynamic problem by using identified parameters... more In this paper, an approach for solving the forward dynamic problem by using identified parameters is presented. A comparison between the identified models; the so-called reduced model and the complete model, and a model with dynamic parameters obtained by a CAD approach is carried out. The results show that the reduced model, obtained based on a set of so-called relevant parameters, is closely related to the actual system response when compared with the other two models.
Revista Iberoamericana de Automática e Informática Industrial RIAI, 2013
La complejidad actual de los sistemas robotizados y de las aplicaciones queéstos deben realizar r... more La complejidad actual de los sistemas robotizados y de las aplicaciones queéstos deben realizar requiere que los robots dispongan de un control automático que permita la ejecución de las distintas tareas que forman parte del algoritmo de control y que tenga en cuenta cuestiones relacionadas por ejemplo con la periodicidad, el modo de ejecución, el hardware que se utilizará, etc. Para el desarrollo de este tipo de aplicaciones de control en losúltimos años se tiende a la programación basada en componentes puesto queésta permite obtener código reusable. Así mismo también se está incrementando la utilización de middlewares que permiten la abstracción de los sistemas operativos, el soporte de tiempo real y la infraestructura de comunicaciones. En el presente artículo se propone la utilización de un middleware orientado especialmente a la robótica: OROCOS. Así se describe cómo haciendo uso de una de sus librerías, Orocos Toolchain, se han desarrollado una serie de componentes correspondientes a distintos algoritmos para el control dinámico de robots, aplicándose a un robot paralelo de 3 grados de libertad (DOF). Copyright c 2012 CEA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
This paper describes a method for calculating the vectorial kinematic parameters of 3D human move... more This paper describes a method for calculating the vectorial kinematic parameters of 3D human movement by stereophotogrammetry, with special emphasis on an accurate characterization of the Instantaneous Helical Axis. That method is applied to the measure of trunk flexion in sitti ng posture, the results being interpreted in biomechanical terms, a nd compared to the mechanical design of articulated work
ABSTRACT In this article a collision-free robot path planning procedure is presented in which a m... more ABSTRACT In this article a collision-free robot path planning procedure is presented in which a manipulability index has been included as one of the optimality criteria when generating the configuration space. From the set of collision-free configurations, a standard algorithm for obtaining optimal trajectories has been considered, taking into account the dynamical robot characteristics. It has been analyzed the effect of the manipulability index in parameters such as the total time that is necessary to perform the trajectory, while the characteristics of the actuators are taken into account.
ABSTRACT Abstract. In this paper a parallel-populations genetic algorithm procedure is presented ... more ABSTRACT Abstract. In this paper a parallel-populations genetic algorithm procedure is presented for the obtainment of minimum-time trajectories for industrial robots. This algorithm is fed in first place by a sequence of configurations then cubic spline functions are used for the construction of joint trajectories for industrial robots. The algorithm is subjected to two types of constraints: (1) Physical constraints on joint velocities, accelerations, and jerk. (2) Dynamic constraints on torque, power, and energy. Comparison examples are used to evaluate the method with different combinations of crossover and mutation.
When dealing with the development of accurate robot dynamic models, the estimation and validation... more When dealing with the development of accurate robot dynamic models, the estimation and validation of the dynamic parameters through experiments becomes necessary. One of the most important objectives to achieve in the design of the experiment, aimed at identification, is to properly excite the system so that the unknown parameters can be accurately estimated. It is customary to find proper excitations optimizing the observation matrix of the model w.r.t. a certain criterion. In this paper the suitability of some trajectory optimization criteria are evaluated for parallel robots. Moreover, a multicriteria algorithm is proposed in order to reduce the deficiencies derived from the single criterion optimization.
ABSTRACT The identification of dynamic parameters in low-mobility mechanical systems is addressed... more ABSTRACT The identification of dynamic parameters in low-mobility mechanical systems is addressed and applied to short long arm (SLA) front car suspension. The main goal of the identification technique is to obtain, from experimental measurements, the values of those dynamic parameters (masses, location of the centre of masses, terms of the inertial matrix of the links, constant friction terms and elastic and viscous damping constant terms) that affect the dynamic behaviour of the system. Moreover, additional but important information that could be obtained from the procedure is related to the weight of those terms inside the dynamics of the system, so that simplified dynamic models based on relevant and well-identified parameters can be established. First, a systematic procedure will be presented for obtaining the equations of motion in a linear form with regard to the dynamic parameters to be identified. The main drawbacks related to the identification of parameters in low-mobility mechanisms will be pointed out, mainly the difficulty of determining a natural cutoff point into the singular values of the observation matrix which allows us to determine the true dimension of the set of base parameters and of obtaining an observation matrix well conditioned from the numerical point of view that allows an identification in the presence of measurement error. The procedure proposed for overcoming these problems will be based on the development of symbolic relationships among the physical parameters in order to determine the true rank of the observation matrix and on the consideration of a reduced subset of the base parameters set. These relevant parameters will be selected according to their influence on the dynamic behaviour of the mechanical system. A virtual benchmark will be used for testing purposes. The dynamic models based on relevant parameters show a better adjustment than the complete ones, mainly when the level of noise in the measurements used in the identification process increases.
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