ISSN:0741-2223    

DOI:10.1002/rob.4620121202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractReaction compensation is necessary for space robot applications because reactional forces/torques will cause undesired movement of the spacecraft. Because the reactional torques can be compensated by the existing torque balancing device in the spacecraft, an additional reaction compensating device is necessary to compensate the reactional forces. In this article we study two types of reactional force compensating devices based on three‐degree‐of freedom, parallel platforms. The first type has three R‐P‐S legs while the second type has three R‐R‐P‐S leg and a passive R‐R‐P leg. A three‐degree of freedom serial manipulator is used to generate reactional forces, which are to be compensated by the paralle platforms. The kinematics and dynamics of both platforms are analyzed and closed form inverse kinematics solutions are derived. We then design a reactional force compensating device that satisfies the strict volume constraint in a spacecraft. The first type of parallel platform is found to require very long legs due to large orientational motion at certain positions. The second type has smooth motion in both position and orientation, and therefore its size can be very compact. It is concluded that the second type of parallel platform has great potential to be used as a compact reactional force compensating device. © 1995

ISSN:0741-2223    

DOI:10.1002/rob.4620121203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractManipulator designs with isotropic architectures have a number of advantages, including high servo accuracy and dexterity. Using the isotropy criterion, isotropic designs of two general classes of planar, three‐degree‐of‐freedom, parallel manipulators with three legs are produced. One of these classes comprises 20 manipulators, while the other, 4. As special cases for each class, the complete set of isotropic designs of 2 manipulators is found. The parameter space of isotropic design of these manipulators is a continuum of at least one dimension. © 2995 John Wiley&Son

ISSN:0741-2223    

DOI:10.1002/rob.4620121204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this article, we investigate and employ torque redistribution and time regulation approaches to track a preplanned trajectory while avoiding actuator saturation for redundantly actuated, fault‐tolerant parallel robots encountering actuator failure. The torque redistribution method utilizes actuation redundancies (if available) after joint failure and/or saturation to alter the torque requirements of the joints so as to avoid saturation. The time regulation method is based upon the alteration of the time to completion of the defined joint‐space trajectory. By searching for a suitable time scaling factor to change (reduce) the inertia load requirements, the robot attempts to slow down or speed up as it moves along the defined trajectory to avoid saturation. The preferred implementation strategy is to use the torque redistribution approach when redundancy is available and actuation capacity is sufficient, otherwise the time regulation approach is employed. For both methods, the computed torque technique, consisting of a model reference algorithm in the feedforward process, and a proportional plus integral plus derivative (PID) controller, to deal with modeling errors and disturbances in the feedback process, are utili

ISSN:0741-2223    

DOI:10.1002/rob.4620121205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractManufacturing tolerances, installation errors, link offsets, and controller errors effect the positioning repeatability of serial and parallel manipulators. A variety of measurement methods have been proposed and used to measure the repeatability of serial manipulators. However, these methods might not be suitable for parallel manipulators due to limited instrumentation accessibility and the large structure involved. This article describes two measurement procedures by which the position of a target point in three‐dimensional space can be determined using a single theodolite that is used to collect two sets of measurements taken from two arbitrary locations. The required hardware needed for the implementation of this method is two standard measuring tapes installed vertically at two arbitrary locations, or one horizontal bar. If the target points are located on the end effector of a manipulator, its repeatability can be measured. The procedure that uses two vertical tapes was used to measure the repeatability of a Stewart Platform and experimental results are provided. © 2995 John Wiley&Sons, I

ISSN:0741-2223    

DOI:10.1002/rob.4620121206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe present a formulation of the direct kinematics of a general six‐degree‐of‐freedom parallel manipulator, sometimes referred to as the generalized Steward platform, whereby the positioning and orientation problems are decoupled by introducing two auxiliary coordinates in the forms of either two angles or two lengths. This is in accordance with the type of extra sensors, i.e., rotary or translational, that are collocated on a leg of the manipulator. Moreover, a real‐time implementation of extra‐sensor data, with a unique direct kinematics solution, is proposed by resorting to an eigenvalue problem. The parallelism in the proposed formulation enables the user to benefit from a parallel computing environment. Hence, we introduce a parallel computing algorithm that highly increases the robustness of the computational algorithm. © 1995 John Wiley

ISSN:0741-2223    

DOI:10.1002/rob.4620121207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dimensionally uniform Jacobian matrix of a novel three‐limbed, six degree‐of‐freedom (DOF) minimanipulator is used to derive its dimensionally uniform stiffness matrix. The minimanipulator limbs are inextensible and its actuators are base‐mounted. The lower ends of the limbs are connected to bidirectional linear stepper motors that are constrained to move on a base plane. The minimanipulator is capable of providing high positional resolution and high stiffness. It is shown that, at a central configuration, the stiffness matrix of the minimanipulator can be decoupled (diagona‐lized), if proper design parameters are chosen. It is also shown that the stiffness of the minimanipulator is higher than that of the Stewart platform. Guidelines for obtaining large minimanipulator stiffness values are established. © 1995 John Wiley

ISSN:0741-2223    

DOI:10.1002/rob.4620121208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractParallel robotic manipulators are complex mechanical systems that lead to involved kinematic and dynamic equations. Hence, the design of such systems is in general not intuitive, and advanced simulation and design tools specialized for this type of architecture are highly desirable. This article discusses the kinematic simulation and computer‐aided design of three‐degree‐of‐freedom spherical parallel manipulators with either prismatic or revolute actuators. The kinematic analysis of spherical parallel manipulators is first reviewed. Solutions for the direct and inverse kinematic problems are given, and the expressions for the singularity loci are then introduced. The determination of the workspace of this type of manipulator is also addressed. Finally, a computer package developed specifically for the CAD of spherical parallel manipulators is presented. This package allows the interactive analysis of manipulators of arbitrary architecture including the representation of the workspace, the representation of singularities, and the graphic animation of trajectories specified either by the direct or the inverse kinematic module. It can be used for the design of any spherical parallel three‐degree‐of‐freedom actuated mechanism, which can find many applications in high‐performance robotic systems. © 3995 John

ISSN:0741-2223    

DOI:10.1002/rob.4620121209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDue to the reliance upon manual operations, conventional loading of munitions on tactical arcraft has several deficiencies including inefficient manpower and time utilization; accident potential; exposure of crew members to chemical, biological, and nuclear agents; and visual obstruction. This article reports on the research and development of a full‐scale prototype robotic system called Robotically Assisted Munition Loading System (RAMLS) comprising a fine motion mechanism (FIMOM), a pose acquisition device (PAD), a manual controller, and a data acquisition and computing system. The FIMOM is a six‐degree‐of‐freedom (DOF) parallel mechanism driven by six hydraulic actuators and the PAD is a passive open kinematic chain mechanism having 6 DOF. The article describes the design and functions of the RAMLS components and presents results of experiments conducted to evaluate the RAMLS's performance. © 3995 John Wiley&S

ISSN:0741-2223    

DOI:10.1002/rob.4620121210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe performance of a Stewart platform‐based force/torque sensor is analyzed. The influence of sensor geometry is assessed with particular reference to the characteristic orientation angles of the arms connecting the platforms, which consist of single‐axis bidirectional force transducers. Static and dynamic performance is analyzed and compared with experimental tests, © 7993 John Wiley&Sons,

ISSN:0741-2223    

DOI:10.1002/rob.4620121211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY