Showing papers on "Robot kinematics published in 2003"

Nonholonomic navigation and control of cooperating mobile manipulators

Abstract: This paper presents the first motion planning methodology applicable to articulated, nonpoint nonholonomic robots with guaranteed collision avoidance and convergence properties. It is based on a new class of nonsmooth Lyapunov functions and a novel extension of the navigation function method to account for nonpoint articulated robots. The dipolar inverse Lyapunov functions introduced are appropriate for nonholonomic control and offer superior performance characteristics compared to existing tools. The new potential field technique uses diffeomorphic transformations and exploits the resulting point-world topology. The combined approach is applied to the problem of handling deformable material by multiple nonholonomic mobile manipulators in an obstacle environment to yield a centralized coordinating control law. Simulation results verify asymptotic convergence of the robots, obstacle avoidance, boundedness of object deformations, and singularity avoidance for the manipulators.

Large deflection dynamics and control for planar continuum robots

Abstract: This paper focuses on a class of robot manipulators termed "continuum" robots - robots that exhibit behavior similar to tentacles, trunks, and snakes. In previous work, we studied details of the mechanical design, kinematics, path-planning and small-deflection dynamics for continuum robots such as the Clemson "tentacle manipulator". In this paper, we discuss the dynamics of a planar continuum backbone section, incorporating a large-deflection dynamic model. Based on these dynamics, we formulate a vibration-damping setpoint controller, and include experimental results to illustrate the efficacy of the proposed controller.

Approximate Jacobian control for robots with uncertain kinematics and dynamics

Abstract: Most research so far in robot control has assumed either kinematics or Jacobian matrix of the robots from joint space to Cartesian space is known exactly. Unfortunately, no physical parameters can be derived exactly. In addition, when the robot picks up objects of uncertain lengths, orientations, or gripping points, the overall kinematics from the robot's base to the tip of the object becomes uncertain and changes according to different tasks. Consequently, it is unknown whether stability of the robot could be guaranteed in the presence of uncertain kinematics. In order to overcome these drawbacks, in this paper, we propose simple feedback control laws for setpoint control without exact knowledge of kinematics, Jacobian matrix, and dynamics. Lyapunov functions are presented for stability analysis of feedback control problem with uncertain kinematics. We shall show that the end-effector's position converges to a desired position in a finite task space even when the kinematics and Jacobian matrix are uncertain. Experimental results are presented to illustrate the performance of the proposed controllers.

Actuator failure detection and isolation using generalized momenta

Abstract: We present a method based on the use of generalized momenta for detecting and isolating actuator faults in robot manipulators. The FDI scheme does not need acceleration estimates or simulation of the nominal robot dynamics and covers a general class of input faults. Numerical results for a 2R robot undergoing also concurrent actuator faults are reported. This method is extended to robots with joint elasticity and to the inclusion of actuator dynamics.

A mobile hyper redundant mechanism for search and rescue tasks

Abstract: In this work we introduce a new concept of a search and rescue robotic system that is composed of an elephant trunk-like robot mounted on a mobile base. This system is capable not only of inspecting areas reachable by the mobile base but also to inspect unreachable areas such as small cracks, and pipes, using the camera mounted on its elephant trunk robot. In the report we describe the mechanical structure of the elephant trunk robot, the kinematic analysis of the structure, the robot control, and its human interface systems.

Kinematic and dynamic analysis of Stewart platform-based machine tool structures

Abstract: In this paper, an analytical study of the kinematics and dynamics of Stewart platform-based machine tool structures is presented. The kinematic study includes the derivation of closed form expressions for the inverse Jacobian matrix of the mechanism and its time derivative. An evaluation of a numerical iterative scheme for an on-line solution of the forward kinematic problem is also presented. Effects of different configurations of the unpowered joints on the angular velocities and accelerations of the links are considered. The Newton-Euler formulation is used to derive the rigid body dynamic equations. Inclusion of models for actuator dynamics and joint friction is discussed.

Composition of local potential functions for global robot control and navigation

Abstract: This paper develops a method of composing simple control policies, applicable over a limited region in a dynamical system's free space, such that the resulting composition completely solves the navigation and control problem for the given system operating in a constrained environment. The resulting control policy deployment induces a global control policy that brings the system to the goal, provided that there is a single connected component of the free space containing both the start and goal configurations. In this paper, control policies for both kinematic and simple dynamical systems are developed. This work assumes that the initial velocities are somewhat aligned with the desired velocity vector field. We conclude by offering an outline of an approach for accommodating arbitrary dynamical constraints and initial conditions.

Human-like motion of a humanoid robot arm based on a closed-form solution of the inverse kinematics problem

Abstract: Humanoid robotics is a new challenging field. To cooperate with human beings, humanoid robots not only have to feature human-like form and structure but, more importantly, they must possess human-like characteristics regarding motion, communication and intelligence. In this paper, we propose an algorithm for solving the inverse kinematics problem associated with the redundant robot arm of the humanoid robot ARMAR. The formulation of the problem is based on the decomposition of the workspace of the arm and on the analytical description of the redundancy of the arm. The solution obtained is characterized by its accuracy and low cost of computation. The algorithm is enhanced in order to generate human-like manipulation motions from object trajectories.

Cooperative works by a human and a humanoid robot

Abstract: We have developed a humanoid robot HRP-2P with a biped locomotion controller, stereo vision software and aural human interface to realize cooperative works by a human and a humanoid robot. The robot can find a target object by the vision, and carry it cooperatively with a human by biped locomotion according to the voice commands by the human. A cooperative control is applied to the arms of the robot while it carries the object, and the walking direction of the robot is controlled by the interactive force and torque through the force/torque sensor on the wrists. The experimental results are presented in the paper.

Development of a flexible tactile sensor system for a humanoid robot

Abstract: The application of robots in the same workspace with humans results, intended or unintended, in direct mechanical interaction. This requires additional sensory abilities of the robots. Besides sensor systems that help the robots to structure their environment, like cameras, radar sensors, etc., a sensor system on the robot's surface is needed that is able to detect mechanical contacts of the robot with its environment. Because of shadings it is not possible to exclude potential collisions in spite of the "structuring" sensor systems. Therefore a tactile sensor system is essential for reasons of security but also as support of the robot control system and additional communication channel. In this paper we propose the requirements to such a system related to its application on an autonomous humanoid robot. According to these postulated requirements a prototypal system was built and integrated in an existing experimental setup which consists of a redundant robot arm with 7 degrees of freedom in a human-similar kinematics. The sensor and its technical specifications as well as the experimental setup are described in the second part of this paper.

A review on vision-based control of robot manipulators

Abstract: Recent vision-based control algorithms for robot manipulators are reviewed. Vision is essential for robots working in an unstructured environment. There are numerous research results in vision-based control. Thus, the scope of this review is limited to providing a brief description on visual servo schemes for manipulators. First, a control architecture for vision-based control is reviewed and some basic ideas for visual servo control are presented. On the basis of these ideas recent research results, especially robust and globally stable controllers, are discussed in detail.

I4: A new parallel mechanism for Scara motions

Abstract: This paper presents a new robot which produces four motions for high speed handling (three translations and one rotation about a given axis in world coordinates). This machine is an evolution of H4's architecture. First, H4's advantages are recalled, and some limitations are mentioned. To compensate for these limitations a new design of the traveling plate is proposed. A description of the whole mechanism is given. The structure's ability to provide Scara motions is presented. Geometrical conditions that must be followed in order to obtain desired motions are discussed. Kinematics models are derived. The design of the first prototype is described.

Dual quaternion synthesis of constrained robotic systems

Abstract: Constrained robotics systems are serial or parallel robots with less than six degrees of freedom. Dimensional synthesis is defined as the process of dimensioning a robot, that is, designing the link dimensions for a given task or set of tasks. In finite-position synthesis, we define the task as a series of positions that the robot must reach. Dimensional synthesis of planar mechanisms was first solved using graphic methods, and later those methods were transformed into algebraic equations that described the constraints on the movement of the mechanism. This approach was successfully applied to spherical mechanisms and simple cases of spatial mechanisms. The methodology was not extended to general constrained robots due to the difficulty in stating the geometric constraints for robots with more than three links. A systematic approach for the synthesis of spatial robots was developed based on using the kinematics equations of the robot. The kinematics equations are spatial transformations from a fixed frame to the end-effector of the robot, parameterized by both the dimensions of the links and the joint variables. In this dissertation, a method for the kinematic synthesis of constrained robots is presented. It is based on the use of dual quaternions to construct the kinematics equations of the robot from a reference position and to equate them to a set of task positions. A calculation was devised to compute the maximum number of task positions for each robot topology, and a classification of constrained robots was obtained according to this. The design equations produced using this methodology have been solved numerically for both the link dimensions and the joint variables, and also a scheme has been introduced to eliminate the joint variables in order to obtain algebraic equations. These have been further simplified to closed algebraic expressions in several cases. The dual quaternion synthesis methodology provides with a tool for the systematic design of constrained robots. Some of these results have been implemented in computer-aided design systems.

Development of mobile inspection robot for rescue activities: MOIRA

Abstract: In this paper we introduce our developed prototype mobile inspection robot for rescue activities named MOIRA. The robot consists of multi links and the four directions of each link are equipped with small crawlers. Due to the structural features, MOIRA has the following features. (a) MOIRA can go into the debris even if there is a restraint from the four directions (up-side, down-side, right-side and left side). (b) MOIRA does not have a concept of the four directions. That is, MOIRA can be operated even if the robot sideslips without any recover actions.

The first human-size humanoid that can fall over safely and stand-up again

Abstract: This paper investigates a method through which human-size humanoid robot can fall over backwards safely. Squatting-extending motion of legs reduce impact of falling and shock-absorbing parts of the robot keep the force at a permissible range. The robot could stand up itself again after falling.

Omni-directional mobile robot controller design by trajectory linearization

Abstract: In this paper, modeling and nonlinear controller design for an omnidirectional mobile robot are presented. Based on the robot dynamics model, a nonlinear controller is designed using the trajectory linearization control (TLC) method. Some simulation results of the controller are presented.

The Tricept robot: dynamics and impedance control

Abstract: The Tricept is a novel industrial robot characterized by a hybrid kinematic design featuring a three-degrees-of-freedom (3-DOF) structure of parallel type and a 3-DOF spherical wrist. In this work the authors focus on the derivation of a dynamic model to be used for both simulation and control purposes. Two different approaches are discussed and compared in terms of inverse dynamics computation. Then, a model-based control is derived aimed at enforcing a 6-DOF impedance behavior at the end effector to manage interaction with the environment. Simulation results are presented to evaluate the accuracy of an approximate dynamic model computation as well as to test the effectiveness of the proposed impedance control strategy.

Nonholonomic motion planning based on Newton algorithm with energy optimization

Abstract: Discusses a modification of the Newton algorithm applied to nonholonomic motion planning with energy optimization. The energy optimization is performed either by optimizing motion in the null space of the Jacobian matrix derived from the nonholonomic system or coupling this motion with movement toward the goal. Resulting controls are smooth and easily generated by motors or thrusters. The two methods can be used, when kinematics are considered, to steer any driftless nonholonomic systems particular free-floating objects, underactuated manipulators, mobile robots (with trailers). Similarities and differences are also discussed in the Newton algorithm for holonomic and nonholonomic systems.

Motion planning a aerial robot using rapidly-exploring random trees with dynamic constraints

Abstract: We describe some recent work on randomized motion planning algorithms and consider the problem of motion planning for systems with both kinematic and dynamic constraints. Such a problem is often referred to as kinodynamic motion planning. A rapidly-exploring random tree (RRT) is used for the motion planning of a blimp system, and some techniques for improving the performance of the planner are proposed. Based on a dynamic model of a blimp, dynamic constraints are introduced into the algorithm design and simulations are conducted for trajectory generation.

Analysis of creeping locomotion of a snake robot on a slope

Abstract: Biological snakes' diverse locomotion modes and physiology make them supremely adapted for environment. To realize these snakes' noticeable features, we have developed a snake-like robot that has no any forward direction driving force. To enlarge the environment-adaptable ability of our robot, in this study we discuss the creeping locomotion of our snake-like robot on a slope. A computer simulator is presented for analysis of the creeping locomotion of our snake-like robot on a slope, and the environment-adaptable body shape for the creeping locomotion of the snake-like robot on slope is also derived through this simulator.

Pushing manipulation by humanoid considering two-kinds of ZMPs

Abstract: This paper discusses the pushing manipulation of an object by a humanoid robot. For such a pushing task, we show that there are two kinds of ZMPs, i.e., the conventional "Zero Moment Point (ZMP)" considering all sources of the force/moment acting in the foot supporting area, and the "Generalized Zero Moment Point (GZMP)" which is an generalization of ZMP for a humanoid robot whose hands do not contact with an object. We first obtain the stable region of the GZMP on the floor. Moreover, since the difference between these two ZMPs corresponds to the magnitude of contact force applied by the hands, we propose the pushing manipulation by a humanoid robot by modifying the desired ZMP trajectory for a humanoid. The effectiveness of the proposed method is confirmed by simulation results.

A new high-speed 4-DOF parallel robot synthesis and modeling issues

Abstract: This paper presents a new family of fully-parallel robots producing motions of the Schoenflies displacements subgroup (three translations and one rotation about a given axis in world coordinates) for high-speed handling and machining. First, the structure's ability to provide this four-degrees-of-freedom motion is presented. Then, two of its possible designs are analyzed: the symmetrical and the asymmetrical one. Constructive designs are then presented. Some of the prototype's preliminary control results are given to prove the H4 robot's efficiency.

Body movement analysis of human-robot interaction

Abstract: This paper presents a method for analyzing human-robot interaetion by body movements. Future intelligent robots will communicate with humans and perform physical and communicative tasks to participate in daily life. A human-like body will provide an abundance of non-verbal information and enable us to smoothly communicate with the robot. To achieve this, we have developed a humanoid robot that autonomously interacts with humans by speaking and making gestures. It is used as a testbed for studying embodied communication. Our strategy is to analyze human-robot interaction in terms of body movements using a motion capturing system, which allows us to measure the body movements in detail. We have performed experiments to compare the body movements with subjective impressions of the robot. The results reveal the importance of well-coordinated behaviors and suggest a new analytical approach to human-robot interaction.

Kinematics and dynamics of a cable-like hyper-flexible manipulator

Abstract: A Hyper-Flexible Manipulator (HFM, for short) is a kind of continuum robots with a simple mechanical structure like a cable, rope and string, which are useful tools utilized everywhere in various forms. In this paper, in order to achieve dexterous and useful manipulation by this type of robot, we discuss kinematics and dynamics of an HFM. We rigorously derive a spatial, nonlinear and continuum dynamics model with an underactuated mechanism using special kinematics based on curve geometry and theory of robot manipulation.

Motion planning of a climbing parallel robot

Abstract: Proposes an application of the Stewart-Gough parallel platform as a climbing robot and its kinematics control to climb through long structures describing unknown spatial trajectories, such as palm trunks, tubes, etc. First, the description and design of the climbing parallel robot is presented. Second, the inverse and forward kinematics analysis of a mobile six-degrees-of-freedom parallel robot is described, based on spatial constraint formulation. Finally, the gait pattern and the climbing strategy of the parallel robot is described. The information from this research is being used in an actual climbing parallel robot design at Miguel Hernandez University of Elche (Alicante), Spain.

Enabling real-time full-body imitation: a natural way of transferring human movement to humanoids

Abstract: We seek intuitive, efficient ways to create and direct human-like behaviors for humanoid robots. Here we present a method to enable humanoid robots to acquire movements by imitation. The robot uses 3D vision to perceive the movements of a human teacher, and then estimates the teacher's body postures using a fast full-body inverse kinematics method that incorporates a kinematic model of the teacher. This solution is then mapped to the robot and reproduced in real-time. The robustness of the method is tested on a 30-degree-of-freedom Sarcos humanoid robot located at ATR using 3D vision data from external cameras and from head-mounted cameras.

Mechanical system of a small biped entertainment robot

Abstract: SDR-4X is the latest prototype model, which is a small humanoid type robot. We reported the outline of this robot last year. In this paper we discuss more about mechanical system, which is important and original for a small biped entertainment robot, which will be used, in home environment. One technology is the design of actuators alignment in the body, which enables dynamic motion performance. Another technology is the actuator technology, which we originally developed, named intelligent servo actuator (ISA). We explain the specification and the important technical points. Next technology is the sensor system, which supports the high performance of the robot, especially the detection of outside objects, ability of stable walking motion and safe interaction with human. The robot is used in normal home environment, so we should strongly consider the falling-over of the robot. We propose the ideas against falling-over which makes the robot as safe as possible.

The first humanoid robot that has the same size as a human and that can lie down and get up

Abstract: This paper presents a humanoid robot that has the same size as a human and that can lie down to the floor and get up from the floor with the robot face upward and downward. We believe that the robot is the first life-size humanoid robot with the capability. The motions are realized by the combination of novel hardware and software. The features of the hardware are a human-like proportion and joints with wide movable ranges including two waist joints. The software segments the motion into the sequence of the contact states between the robot and the floor and assigns an appropriate controller to each transition between the consecutive states. The experimental results are presented.