Infoscience

Thesis

Interface pour le pilotage et l'analyse des robots basée sur un générateur de cinématiques

In robotics we depend on software tools during design, modeling, programming and testing. These tools are essentials, often indispensable aids for developing and operating sophisticated robotic systems. At the same time, these tools are complex and usually too difficult to be used by non specialists. For example tools used for simulation or off-line programming require significant knowledge and skill. The goal of this thesis is to provide novice users with an intuitive tool (CINEGEN) for designing, studying and controlling robot manipulators without programming. In particular the tool addresses two main problems: 1) modeling a new robot requires an significant amount of time; 2) robot tasks (motion, actions, etc.) are generally difficult for novice users to specify. CINEGEN is a novel tool for kinematic simulation of robot manipulators in a virtual environment. It is easy to use and is capable of handling generic kinematic structures. With CINEGEN the description of robots is easy to perform and enables rapid prototyping. Additionally, CINEGEN's capability for real-time interactive simulation allows novice users to quickly specify and evaluate robot tasks. A new simulation can be created very rapidly by describing the robot in a simple text based configuration file. In this file, robots are defined by the properties of each link and their relationships. Robots are defined as a tree structure from the base to the end-effector. For robots with kinematic loops, each loop is represented with two open sub-chains which are closed using a simple constraint. This same type of constraint is used to define which part of the robot must follow movements generated by input devices to the simulation. Once defined, this file is parsed by CINEGEN which automatically constructs the robot structure and its numerical kinematic model to satisfy all the constraints. Then the kinematic solver computes the robot movements regarding the user inputs and the internal constraints. This allows the user to interactively control the robot in two modes: direct kinematics (independent control of each joint) or inverse kinematics (control of the end effector). This constraint solver scheme provides the user with a unified interface to control robots without requiring thought about direct or inverse kinematics. The user interacts with the model of the robot using a virtual reality based interface. This interface gives the user a direct and intuitive means to study a robot's behavior. The virtual reality based interface implies three fundamentals needs: a visualization of 3-dimensional world, appropriate input devices and real-time simulation. The visualization of the robot in a three dimensional space allows the user to understand the robot and the world in which it moves without any symbolic representation. The design of a new haptic input device extends the use of commercial devices employed, making it easier to generate control inputs as well as to "feel" the robot response. Real-time performance (refresh at more than 25Hz) of the complete simulation (graphics as well as kinematics) is obtained via efficient numerical tools and a constraint solver dedicated to robot kinematics. In short, the project developed in this thesis answer to two principal needs: rapid prototyping and analysis of robot manipulators with general kinematic structure, an intuitive interface for teleoperation (task definition) of new robots without programming.

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