Planificación local basada en sensores para un manipulador móvil en tareas de colaboración con humanos

Un manipulador móvil, como cualquier otro sistema que opere en entornos reales, debe ser capaz de evitar los obstáculos que se presenten en su camino. Sin embargo, en el caso del manipulador móvil, la solución de este problema es mucho más compleja. Esta tesis propone una estrategia para dotar al manipulador móvil de esta habilidad basándose en la información del entorno proporcionada por un telémetro láser. Se ha optado por un modelo único del entorno, el Diagrama de Voronoi Local, construido a partir de los datos sensoriales, que se utiliza por igual en los módulos de planificación y localización. El algoritmo propuesto puede utilizarse en línea para construir el DVL de una zona restringida del entorno alrededor de la posición actual del robot. La limitación en el tiempo de cómputo, permite actualizar el modelo del entorno con suficiente rapidez para detectar la presencia de obstáculos inesperados y planificar una trayectoria local que permita evitarlos. El diseño de los módulos de construcción del mapa local, localización y planificación se ha hecho con la idea de que puedan ser aplicados a cualquier tipo de robot móvil dotado de un telémetro láser. De esta forma, los algorit mos desarrollados y presentados en esta tesis son aplicables a un considerable número de sistemas. Su funcionamiento ha podido comprobarse en la eje cución de una serie de experimentos cuyos resultados quedan recogidos a lo largo de este trabajo. Por último, se presentan las adaptaciones de los algoritmos desarrollados para su integración en el sistema de control de un manipulador móvil. Te niendo como objetivo la colaboración del sistema con operarios humanos en tareas de transporte de piezas, el planificador de trayectorias locales se conec ta directamente con el módulo de control cinemático coordinado y el bucle de control de impedancia previamente diseñados. A su vez, la realimentación de la señal de fuerza en el módulo de planificación permite estimar la dirección de movimiento del operario. Con esta información el planificador escoge, si es posible, aquella trayectoria local libre de obstáculos que más se adecúe al movimiento del operario. _________________________________________________A mobile manipulator, just like any other system operating in real envi ronments, must be able to avoid obstacles that appear on its way. This thesis proposes a strategy to provide the mobile manipulator with this ability. It is based 011 environment information supplied by a laser range scanner. The Local Voronoi Diagram (LVD), built from sensor data, has been adopted like the only one environment model. It is used the same in planning as localization modules. The proposed algorithm is able to be used on-line to construct the LVD of a visible region around the current location of the robot. Computing time is limited, this allows up to update the environment model in a short time, detecting the presence of unexpected obstacles and planning a local path to avoid its. The design of local map construction, localization and planification mo dules have been developed with the intention to be putting in practice on any mobile robot with a scanner laser on board. Then, algorithms described in this thesis can be applied to a lot of systems. The algorithms performance has been tested running a sequence of experiments on real systems. The results are presented along this document. Finally, the algorithms have been adapted to be integrated on the mobile manipulator control system. In order to collaborate with human operator in material handling tasks, the local path planning module is connected with the coordinated kinematic control module and with the damping control module previously designed. Force signal is used in planning module to estimate movement direction for the operator. The planning module uses this information to choose the best local free path, closer to the human movement

Compact Modeling Technique for Outdoor Navigation

16 pages, 46 figures.In this paper, a new methodology to build compact local maps in real time for outdoor robot navigation is presented. The environment information is obtained from a 3-D scanner laser. The navigation model, which is called traversable region model, is based on a Voronoi diagram technique, but adapted to large outdoor environments. The model obtained with this methodology allows a definition of safe trajectories that depend on the robot's capabilities and the terrain properties, and it will represent, in a topogeometric way, the environment as local and global maps. The application presented is validated in real outdoor environments with the robot called GOLIAT.This work was supported by the Spanish Government through the MICYT project DPI2003-01170.Publicad

L1-L2 norms comparison in global localization of mobile robots

The global localization methods deal with the estimation of the pose of a mobile robot assuming no prior state information about the pose and a complete a priori knowledge of the environment where the mobile robot is going to be localized. Most existing algorithms are based on the minimization of an L2-norm loss function. In spite of the extended use of the L2-norm, the use of the L1-norm offers some alternative advantages. The present work compares the L1-norm and the L2-norm with the same basic optimization mechanism to determine the advantages of each norm when applied to the global localization problem. The algorithm has been tested subject to different noise levels to demonstrate the accuracy, effectiveness, robustness, and computational efficiency of both L1-norm and L2-norm approaches.This work has been supported by the CAM Project S2009/DPI-1559/ROBOCITY2030 II, developed by the research team RoboticsLab at the University Carlos III of Madrid.Publicad

Application of the fast marching method for outdoor motion planning in robotics

In this paper, a new path planning method for robots used in outdoor environments is presented. The proposed method applies Fast Marching to a 3D surface represented by a triangular mesh to calculate a smooth trajectory from one point to another. The method uses a triangular mesh instead of a square one since this kind of grid adapts better to 3D surfaces. The novelty of this approach is that, before running the algorithm, the method calculates a weight matrix W based on the information extracted from the 3D surface characteristics. In the presented experiments these features are the height, the spherical variance, and the gradient of the surface. This matrix can be viewed as a difficulty map situated over the 3D surface and is used to limit the propagation speed of the Fast Marching wave in order to find the best path depending on the task requirements, e.g., the least energy consumption path, the fastest path, or the most plain terrain. The algorithm also gives the speed for the robot, which depends on the wave front propagation speed. The results presented in this paper show how, by varying this matrix W, the paths obtained are different. Moreover, as it is shown in the experimental part, this algorithm is also useful for calculating paths for climbing robots in much more complex environments. Finally, at the end of the paper, it is shown that this algorithm can also be used for robot avoidance when two robots approach each other, and they know each other's position.Comunidad de Madri

Flexible shape-memory alloy-based actuator: Mechanical design optimization according to application

This article belongs to the Special Issue Actuators Based on Shape Memory Alloys.New robotic applications, among others, in medical and related fields, have in recent years boosted research in the development of new actuators in the search for solutions that are lighter and more flexible than conventional actuators. Shape-Memory Alloy (SMA)-based actuators present characteristics that make them an excellent alternative in a wide variety of applications. This paper presents the design, tests (with the control description) and analysis of various configurations of actuators based on SMA wires: flexible SMA actuators, different mechanical design to multiply the displacement and different configurations for actuators with multiple SMA wires. The performance of the actuators has been analyzed using wires of different activation temperatures. The influence of the Bowden sheath of the flexible actuator has been tested, as has the thermal behavior of actuators with several wires. This work has allowed determination of the most effective configuration for the development of a flexible actuator based on SMA, from the point of view of dimensions, efficiency, and work frequency. This type of actuator has been applied in the development of soft robots and light robotic exoskeletons.The research leading to these results has received funding from the Exoesqueleto para Diagnostico y Asistencia en Tareas de Manipulación (DPI2016-75346-R) Spanish research project and from RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub, S2018/NMT-4331, funded by ¿Programas de Actividades I+D en la Comunidad de Madrid¿ and cofunded by Structural Funds of the EU

Two-stage shape memory alloy identification based on the Hammerstein - Wiener model

from the two stages was obtained for a specific shape memory alloy wire and for specific environmental conditions. This data was used in the modeling process. The final model consists of a combination of the models from the two stages, which represent the behavior of the shape memory alloy actuator where the input signal is the pulse-width modulation signal and the output signal are the position of the actuator. Our results indicate that our model has a very similar response to the behavior of the real actuator. This model can be used to tune different control algorithms, simulate the entry system before manufacture and test on real devices.The research leading to these results has received funding from the Exoesqueleto para Diagnostico y Asistencia en Tareas de Manipulación (DPI2016-75346-R) Spanish research project and from RoboCity2030-DIH-CM, Madrid Robotics Digital Innovation Hub, S2018/NMT-4331, funded by Programas de Actividades I + D en la Comunidad de Madrid and cofunded by Structural Funds of the EU

SLAM and exploration using differential evolution and fast marching

The exploration and construction of maps in unknown environments is a challenge for robotics. The proposed method is facing this problem by combining effective techniques for planning, SLAM, and a new exploration approach based on the Voronoi Fast Marching method. The final goal of the exploration task is to build a map of the environment that previously the robot did not know. The exploration is not only to determine where the robot should move, but also to plan the movement, and the process of simultaneous localization and mapping. This work proposes the Voronoi Fast Marching method that uses a Fast Marching technique on the Logarithm of the Extended Voronoi Transform of the environment"s image provided by sensors, to determine a motion plan. The Logarithm of the Extended Voronoi Transform imitates the repulsive electric potential from walls and obstacles, and the Fast Marching Method propagates a wave over that potential map. The trajectory is calculated by the gradient method

Robotic Motion using Harmonic Functions and Finite Elements

The harmonic functions have proved to be a powerful technique for motion planning in a known environment. They have two important properties: given an initial point and an objective in a connected domain, a unique path exists between those points. This path is the maximum gradient path of the harmonic function that begins in the initial point and ends in the goal point. The second property is that the harmonic function cannot have local minima in the interior of the domain (the objective point is considered as a border). This paper proposes a new method to solve Laplace's equation. The harmonic function solution with mixed boundary conditions provides paths that verify the smoothness and safety considerations required for mobile robot path planning. The proposed approach uses the Finite Elements Method to solve Laplace's equation, and this allows us to deal with complicated shapes of obstacles and walls. Mixed boundary conditions are applied to the harmonic function to improve the quality of the trajectories. In this way, the trajectories are smooth, avoiding the corners of walls and obstacles, and the potential slope is not too small, avoiding the difficulty of the numerical calculus of the trajectory. Results show that this method is able to deal with moving obstacles, and even for non-holonomic vehicles. The proposed method can be generalized to 3D or more dimensions and it can be used to move robot manipulators

High-accuracy global localization filter for three-dimensional environments

The localization problem in mobile robotics can be defined as the search of the robot's coordinates in a known environment. If there is no information about the initial location, we are talking about global localization. In this work, we have developed an algorithm that solves this problem in a three-dimensional (3D) environment using evolutionary computation concepts. The method has been called RELF-3D and has many features that make it very robust and reliable: thresholding and discarding mechanisms, different cost functions, effective convergence criteria, and so on. The resulting global localization module has been tested in numerous experiments and the most important improvement obtained is the accuracy of the method, allowing its application in manipulation tasksThe localization problem in mobile robotics can be defined as the search of the robot's coordinates in a known environment. If there is no information about the initial location, we are talking about global localization. In this work, we have developed an algorithm that solves this problem in a three-dimensional (3D) environment using evolutionary computation concepts. The method has been called RELF-3D and has many features that make it very robust and reliable: thresholding and discarding mechanisms, different cost functions, effective convergence criteria, and so on. The resulting global localization module has been tested in numerous experiments and the most important improvement obtained is the accuracy of the method, allowing its application in manipulation tasksThis work has been supported by the CAM Project S2009/DPI-1559/ROBOCITY2030 II, developed by the research team RoboticsLab at the University Carlos III of Madrid.Publicad

Global localization based on a rejection differential evolution filter

Autonomous systems are able to move from one point to another in a given environment because they can solve two basic problems: the localization problem and the navigation problem. The localization purpose is to determine the current pose of the autonomous robot or system and the navigation purpose is to find out a feasible path from the current pose to the goal point that avoids any obstacle present in the environment. Obviously, without a reliable localization system it is not possible to solve the navigation problem. Both problems are among the oldest problems in human travels and have motivated a considerable amount of technological advances in human history. They are also present in robot motion around the environment and have also motivated a considerable research effort to solve them in an efficient way