1,568 research outputs found
Safety-related Tasks within the Set-Based Task-Priority Inverse Kinematics Framework
In this paper we present a framework that allows the motion control of a
robotic arm automatically handling different kinds of safety-related tasks. The
developed controller is based on a Task-Priority Inverse Kinematics algorithm
that allows the manipulator's motion while respecting constraints defined
either in the joint or in the operational space in the form of equality-based
or set-based tasks. This gives the possibility to define, among the others,
tasks as joint-limits, obstacle avoidance or limiting the workspace in the
operational space. Additionally, an algorithm for the real-time computation of
the minimum distance between the manipulator and other objects in the
environment using depth measurements has been implemented, effectively allowing
obstacle avoidance tasks. Experiments with a Jaco manipulator, operating in
an environment where an RGB-D sensor is used for the obstacles detection, show
the effectiveness of the developed system
Singularity Analysis of a Snake Robot and an Articulated Mobile Robot With Unconstrained Links
In this paper, we analyze the conditions related to singular configurations with unconstrained links and present related theorems and lemmas for a snake robot and an articulated mobile robot. A snake robot and an articulated mobile robot have links that have passive or active wheels and the links are serially connected by active joints. The singular configuration should be avoided if the robots are automatically controlled because they cannot execute intended motion when they are in the singular configuration. We derive a novel necessary and sufficient condition for the singular configurations of the snake robot; this removes some limitations of the traditional condition for a snake robot without unconstrained links. We also derive the necessary and sufficient conditions for the singular configurations of the articulated mobile robot, and the structural conditions under which a real articulated mobile robot does not have a singular configuration. These conditions are proved by analyzing the elements of matrices included in the kinematic model and considering the geometrical meaning of the elements. In addition, we propose evaluation indices representing the distance from the singular configurations of a snake robot. We verify the effectiveness of these indices through simulations
Range-Sensor-Based Semiautonomous Whole-Body Collision Avoidance of a Snake Robot
This brief presents a control system for a snake robot based on range sensor data that semiautonomously aids the robot in avoiding collisions with obstacles. In the proposed system, an operator indicates the desired velocity of the first link of the robot using a joystick, and the joint input which accomplishes both the desired velocity of the first link and collision avoidance between subsequent links and obstacles is automatically calculated by the controller, which selects the links needed to be grounded and exploits redundancy. The controller uses real-time data from range sensors for obstacle positions. The experimental system, which has range sensors and the function generating environmental map using simultaneous localization and mapping, was developed with decreasing calculation cost, and experiments were performed to verify the effectiveness of the proposed system in unknown environments
Planning and Real Time Control of a Minimally Invasive Robotic Surgery System
This paper introduces the planning and control software of a teleoperating robotic system for minimally invasive surgery. It addresses the problem of how to organize a complex system with 41 degrees of freedom including robot setup planning, force feedback control and nullspace handling with three robotic arms. The planning software is separated into sequentially executed planning and registration procedures. An optimal setup is first planned in virtual reality and then adapted to variations in the operating room. The real time control system is composed of hierarchical layers. The design is flexible and expandable without losing performance. Structure, functionality and implementation of planning and control are described. The robotic system provides the surgeon with an intuitive hand-eye-coordination and force feedback in teleoperation for both hands
A modal approach to hyper-redundant manipulator kinematics
This paper presents novel and efficient kinematic modeling techniques for “hyper-redundant” robots. This approach is based on a “backbone curve” that captures the robot's macroscopic geometric features. The inverse kinematic, or “hyper-redundancy resolution,” problem reduces to determining the time varying backbone curve behavior. To efficiently solve the inverse kinematics problem, the authors introduce a “modal” approach, in which a set of intrinsic backbone curve shape functions are restricted to a modal form. The singularities of the modal approach, modal non-degeneracy conditions, and modal switching are considered. For discretely segmented morphologies, the authors introduce “fitting” algorithms that determine the actuator displacements that cause the discrete manipulator to adhere to the backbone curve. These techniques are demonstrated with planar and spatial mechanism examples. They have also been implemented on a 30 degree-of-freedom robot prototype
COCrIP: Compliant OmniCrawler In-pipeline Robot
This paper presents a modular in-pipeline climbing robot with a novel
compliant foldable OmniCrawler mechanism. The circular cross-section of the
OmniCrawler module enables a holonomic motion to facilitate the alignment of
the robot in the direction of bends. Additionally, the crawler mechanism
provides a fair amount of traction, even on slippery surfaces. These advantages
of crawler modules have been further supplemented by incorporating active
compliance in the module itself which helps to negotiate sharp bends in small
diameter pipes. The robot has a series of 3 such compliant foldable modules
interconnected by the links via passive joints. For the desirable pipe diameter
and curvature of the bends, the spring stiffness value for each passive joint
is determined by formulating a constrained optimization problem using the
quasi-static model of the robot. Moreover, a minimum friction coefficient value
between the module-pipe surface which can be vertically climbed by the robot
without slipping is estimated. The numerical simulation results have further
been validated by experiments on real robot prototype
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