Memorias de investigación
Book chapters:
New visual servoing control strategies in tracking tasks using a PKM

Research Areas
  • Perception,
  • Visual control

Vision allows a robotic system to obtain a lot of information on the surrounding environment to be used for motion planning and control. When the control is based on feedback of visual information is called Visual Servoing. Visual Servoing is a powerful tool which allows a robot to increase its interaction capabilities and tasks complexity. In this chapter we describe the architecture of the Robotenis system in order to design two different control strategies to carry out tracking tasks. Robotenis is an experimental stage that is formed of a parallel robot and vision equipment. The system was designed to test joint control and Visual Servoing algorithms and the main objective is to carry out tasks in three dimensions and dynamical environments. As a result the mechanical system is able to interact with objects which move close to 2m=s. The general architecture of control strategies is composed by two intertwined control loops: The internal loop is faster and considers the information from the joins, its sample time is 0:5ms. Second loop represents the visual Servoing system and it is an external loop to the first mentioned. The second loop represents the main study purpose, it is based in the prediction of the object velocity that is obtained from visual information and its sample time is 8:3ms. The robot workspace analysis plays an important role in Visual Servoing tasks, by this analysis is possible to bound the movements that the robot is able to reach. In this article the robot jacobian is obtained by two methods. First method uses velocity vector-loop equations and the second is calculated from the time derivate of the kinematical model of the robot. First jacobian requires calculating angles from the kinematic model. Second jacobian instead, depends on physical parameters of the robot and can be calculated directly. Jacobians are calculated from two different kinematic models, the first one determines the angles each element of the robot. Fist jacobian is used in the graphic simulator of the system due to the information that can be obtained from it. Second jacobian is used to determine off-line the work space of the robot and it is used in the joint and visual controller of the robot (in real time). The work space of the robot is calculated from the condition number of the jacobian (this is a topic that is not studied in article). The dynamic model of the mechanical system is based on Lagrange multipliers, and it uses forearms and end effector platform of non-negligible inertias for the development of control strategies. By means of obtaining the dynamic model, a nonlinear feed forward and a PD control is been applied to control the actuated joints. High requirements are required to the robot. Although requirements were taken into account in the design of the system, additional protection is added by means of a trajectory planner. The trajectory planner was specially designed to guarantee soft trajectories and protect the system from exceeding its Maximum capabilities. Stability analysis, system delays and saturation components has been taken into account and although we do not present real results, we present two cases: Static and dynamic. In previous works we present some results when the static case is considered.
Book Edition
Book Publishing
Book title
Mechatronic Systems Simulation Modeling and Control
From page
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Research Group, Departaments and Institutes related
  • Creador: Grupo de Investigación: Robots y máquinas inteligentes
  • Departamento: Automática, Ingeniería Electrónica e Informática Industrial
  • Centro o Instituto I+D+i: Centro de Automática y Robótica (CAR). Centro Mixto UPM-CSIC