Showing papers on "Revolute joint published in 2002"

Design of large-displacement compliant joints

Abstract: Flexure joints are widely used to approximate the function of traditional mechanical joints, while offering the benefits of high precision, long life, and ease of manufacture. This paper investigates and catalogs the drawbacks of typical flexure connectors and presents several new designs for highly-effective, kinematically-behaved compliant joints. A revolute and a translational compliant joint are proposed (Figure 1), both of which offer great improvements over existing flexures in the qualities of (1) large range of motion, (2) minimal axis drift, (3) increased off-axis stiffness, and (4) reduced stress-concentrations. Analytic stiffness equations are developed for each joint and parametric computer models are used to verify their superior stiffness properties. A catalog of design charts based on the parametric models is also presented, allowing for rapid sizing of the joints for custom performance. Finally, two multi-degree-of-freedom joints are proposed as modifications to the revolute joint. These include a compliant universal joint and a compliant spherical joint, both designed to provide high degrees of compliance in the desired direction of motion and high stiffness in other directions.Copyright © 2002 by ASME

Design and experiment of a 3 DOF parallel micro-mechanism utilizing flexure hinges

Abstract: Flexure hinge has been commonly used as a substitute for mechanical joints in the design of micropositioning mechanisms. However, inaccurate modeling of flexure hinges deteriorates the positioning accuracy. In this paper, a planar 3-DOF parallel-type micropositioning mechanism is designed with the intention of accurate flexure hinge modeling. For this, a preliminary kinematic analysis that includes inverse kinematics, internal kinematics, and analytic stiffness modeling referenced to the task coordinate is presented. First, the revolute type of 1-DOF flexure hinge is considered. The simulation result based on the finite element method, however, is not coincident to the analytic result. This is due to the minor axial elongation along the link direction that keeps the mechanism from precise positioning. To cope with this problem, a 2-DOF flexure hinge model that includes this additional motion degree as a prismatic joint is employed in part, and additional actuators are added to compensate for the motion of this new model. On the basis of this model, the positional accuracy is ensured. The effectiveness of this accurate model is shown through both simulation and experimentation. This paper emphasizes that the precise modeling of a flexure hinge is significant to guarantee the positional accuracy of parallel micromechanisms using flexure hinge.

Design Optimization of a Cartesian Parallel Manipulator

Abstract: This paper introduces a new 3-DOF translational parallel manipulator named the Cartesian Parallel Manipulator (CPM). The manipulator consists of a moving platform that is connected to a fixed base by three limbs. Each limb is made up of one prismatic and three revolute joints and all joint axes are parallel to one another. In this way, each limb provides two rotational constraints to the moving platform and the combined effects of the three limbs lead to an over-constrained mechanism with three translational degrees of freedom. The manipulator behaves like a conventional X-Y-Z Cartesian machine due to the orthogonal arrangement of the three limbs. Two actuation methods are analyzed. However, the rotary actuation method is discarded because of the existence of singularities within the workspace. For the linear actuation method, there exists a one-to-one correspondence between the input and output displacements of the manipulator. However, each limb structure is exposed to a relatively large moment about an axis perpendicular to the prismatic joint axis. In order to compensate for this shortcoming, a method to maximize the stiffness is suggested. Finally, a numerical example of the optimal design is presented.Copyright © 2002 by ASME

Complete Path Planning for Closed Kinematic Chains with Spherical Joints

Abstract: We study the path planning problem, without obstacles, for closed kinematic chains with n links connected by spherical joints in space or revolute joints in the plane. The configuration space of such systems is a real algebraic variety whose structure is fully determined using techniques from algebraic geometry and differential topology. This structure is then exploited to design a complete path planning algorithm that produces a sequence of compliant moves, each of which monotonically increases the number of links in their goal configurations. The average running time of this algorithm is proportional to n3. While less efficient than the O(n) algorithm of Lenhart and Whitesides, our algorithm produces paths that are considerably smoother. More importantly, our analysis serves as a demonstration of how to apply advanced mathematical techniques to path planning problems.Theoretically, our results can be extended to produce collision-free paths, paths avoiding both link—obstacle and link—link collisions. An...

The 3-RRS Wrist: A New, Very Simple and Not Over-Constrained Spherical Parallel Manipulator

Abstract: Orientating a rigid body without changing its position is required in many technical applications. This manipulation task is accomplished by manipulators (spherical manipulators) that are just able to make the end effector move according to controlled spherical motions. Spherical manipulators can be either serial or parallel. Parallel architectures are usually more stiff and precise than the serial ones, whereas their structures are more complex than the serial ones. This paper presents a new three-equal-legged spherical parallel manipulator, named 3-RRS wrist. The 3-RRS wrist is not overconstrained and exhibits a very simple architecture employing just three passive revolute pairs, three passive spherical pairs and three actuated revolute pairs adjacent to the frame. The kinematic analysis of the 3-RRS wrist is addressed and fully solved. Finally, its singularity conditions are written in explicit form and discussed. The results of this analysis lead to the conclusion that the new manipulator has only two types of singularities both easy to be identified with geometric reasoning.Copyright © 2002 by ASME

Solving the Geometric Design Problem of Spatial 3R Robot Manipulators Using Polynomial Homotopy Continuation

Abstract: In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints is solved using a polynomial homotopy continuation method. Three spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these three pre-specified locations. Denavit and Hartenberg parameters and 4X4 homogeneous matrices are used to formulate the problem and obtain eighteen design equations in twenty-four design unknowns. Six of the design parameters are set as free choices and their values are selected arbitrarily. Two different cases for selecting the free choices are considered and their design equations are solved using polynomial homotopy continuation. In both cases for free choice selection, eight distinct manipulators are found that will be able to place their end-effector at the three specified spatial positions and orientations.

Design and Experiment of a 3DOF Parallel Micro-Mechanism Utilizing Flexure Hinges

Abstract: Flexure hinge has been commonly used as a substitute for mechanical joints in the design of micro- positioning mechanisms. However, inaccurate modeling of that must be specified in order to locate the elements of an object relative to another. It is described by (7) i=l mechanism is designed with the intention of accurate flexure hinge modeling. For this, a preliminary kinematic analysis that includes inverse kinematics, internal kinematics, and analytic stifhess modeling referenced to the task coordinate is presented. First, the revolute type of lDOF flexure hinge is considered. The simulation result based on FEM, however, is not coincident to the analytic result. This is due to the minor axial elongation along the link direction that keeps the mechanism from precise positioning. To cope with this problem, a 2DOF flexure hinge model that includes this additional motion degree as a prismatic joint is employed in part. On the basis of this model, the positional accuracy is ensured. The effectiveness of this accurate model is shown through both simulation and experimentation This work emphasizes that the precise modeling of a flexure hinge is significant to guarantee the positional accuracy of parallel micro-mechanisms using flexure hinge.

Design and Singularity Analysis of a 3-Translational-DOF In-Parallel Manipulator*

Abstract: In this work, we shall present a novel design of a 3-translational-DOF in-parallel manipulator having 3 linear actuators. Three variable length legs constitute the actuators of this manipulator, whereas two other kinematic chains with passive joints are used to eliminate the three rotations of the platform with respect to the base. This design presents several advantages compared to other designs of similar 3-translational-dof parallel manipulators. First, the proposed design uses only revolute or spherical joints as passive joints and hence, it avoids problems that are inherent to the nature of prismatic joints when loaded in arbitrary way. Second, the actuators are chosen to be linear and to be located in the three legs since this design presents higher rigidity than other. In the second part of this paper, we addressed the problem of kinematic analysis of the proposed in-parallel manipulator. A mixed geometric and vector formulation is used to show that two solutions exist for the forward kinematic analysis. The problem of singularities is also investigated using the same method. In this work, we investigated the singularities of the active legs and the two types of singularity were identified: architectural singularities and configurational singularities. The singularity of the passive chains, used to restrict the motion of the platform to only three translations, is also investigated. In the last part of this paper we built a 3D solid model of the platform and the amplitude of rotation due to the deformation of the different links under some realistic load was determined. This allowed us to estimate the orientation error of the platform due to external moments. Moreover, this analysis allowed us to compare the proposed design (over constrained) with a modified one (not over constrained). This comparison confirmed the conclusion that the over constraint design has a better rigidity.

An inverse position analysis of five-bar planar parallel manipulators

Abstract: In this paper, we present a simple method to obtain joint inputs needed to attain any point in the reachable workspace of a class of five-bar planar parallel manipulators which are based on five rigid links and five single degree of freedom joints – revolute and prismatic joints. Depending on the topology of the manipulators, two mathematical expressions describing the path traced by the tip of two links connected to each other are obtained and solved simultaneously in order to determine the intersection points of the two paths which are the Cartesian coordinates of the connection points for the links. For the class of manipulators considered in this study, one of the links is the link activated by an actuator fixed to the ground. So, rotational and/or translational joint inputs can be determined from the Cartesian coordinates of the tip of the activated links. Sylvester's dialytic elimination method is employed to solve the equations. Such a methodology is easy to implement, computationally efficient and sound to compute all possible solutions. A numerical example is provided for each manipulator and the inverse position solutions are verified by substituting them into forward position equations. It is concluded that the proposed method is useful in trajectory planning and control of five-bar planar parallel manipulators in joint space.

Five Precision Point Synthesis of Spatial RRR Manipulators Using Interval Analysis

Abstract: In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints is solved for the first time using an interval analysis method. In this problem, five spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these pre-specified locations. Denavit and Hartenberg parameters and 4×4 homogeneous matrices are used to formulate the problem and obtain the design equations and an interval method is used to search for design solutions within a predetermined domain. At the time of writing this paper, six design solutions within the search domain and an additional twenty solutions outside the domain have been found.Copyright © 2002 by ASME

Singularity Loci of a Special Class of Spherical Three-degree-of-freedom Parallel Mechanisms with Revolute Actuators:

Abstract: In this paper, we study the singularity loci of a special class of spherical three-degree-of-freedom parallel manipulators. The concise analytical expressions describing the singularity loci are ob...

Goniometer-based body-tracking device

Abstract: A sensing system is provided for measuring various joints of a human body for applications for performance animation, biomechanical studies and general motion capture. One sensing device of the system is a linkage-based sensing structure comprising rigid links interconnected by revolute joints, where each joint angle is measured by a resistive bend sensor or other convenient goniometer. Such a linkage-based sensing structure is typically used for measuring joints of the body, such as the shoulders, hips, neck, back and forearm, which have more than a single rotary degree of freedom of movement. In one embodiment of the linkage-based sensing structure, a single long resistive bend sensor measures the angle of more than one revolute joint. A second sensing device of the sensing system comprises a flat, flexible resistive bend sensor guided by a channel on an elastic garment.

Advances in Robot Kinematics: Theory and Applications

Abstract: Performance Evaluation. A kinematic calibration of in-parallel actuated mechanisms using Fourier series (evaluation index for determination of the set of measurement paths) G. Shen, et al. Dynamic performance indices for 3-DOF parallel manipulators R. Di Gregorio, V. Parenti-Castelli. Evaluation of a Caresian parallel manipulator H.S. Kim, L.-W. Tsai. Rotation symmetry axes and the quality index in a 3D octahedral parallel robot manipulator system T.K. Tanev, J. Rooney. Linearized kinematics for state estimation in robotics K. Parsa, et al. Performance evaluation of the grasp of two cooperating robots using a type map N. Gascons, et al. On the invariance of manipulability indices E. Staffetti, et al. Influence of the manipulability index on trajectory planning for robots in a workspace with obstacles F. Valero, et al. Design and Control of Special-Type Mechanisms. Humanoid humeral pointing kinematics J. Lenarcic, et al. Efficient algorithms for robots with human-like structures and interactive haptic simulation O. Khatib, et al. Particular aspects in designing anthropomorphic mechanisms C. Brisan, M. Hiller. Uncertainty model and singularities of 3-2-1 wire-based tracking systems F. Thomas, et al. Tension distribution in tendon-based Stewart platforms R. Verhoeven, M. Hiller. Trajectory tracking control for a cable suspension manipulator T. Heyden, et al. Is design of new drugs a challenge for kinematics? K. Kazerounian. Redundancy, Singularity, and Self-Motion. Redundant spatial Stewart-Gough platform with a maximal forward kinematics solution set M. Husty, et al. Singularities and self-motions of a special type of platforms A. Karger. Investigation of singularities and self-motions of the 3-UPU robot A. Wolf, et al. On closure modes and singular configurations of kinematic chains J.E. Baker. Constraint singularities as c-space singularities D. Zlatanov, et al. Hierarchical kinematic analysis of a redundant robot D. Martins, R. Guenther. Motion planning of redundant manipulators for specified trajectory tasks J.A. Pamanes, et al. Realtime coordinated redundant motion of a nonholonomic mobile manipulator G. Schreiber, G. Hirzinger. Methods in Kinematics. Using body flexibility to simplify the solution of kinematic equations in the dynamic analysis of robot mechanisms and multibody systems P. Fanghella, C. Galletti. Subdivision algorithms for motion design based on homologous points M. Hofer, et al. Group theory can explain the mobility of paradoxical linkages J.M. Ribo, B. Ravani. Solving multi-loop linkages by iterating 2D clippings J.M. Porta, et al. Revisiting Plucker coordinates in vision-based control N. Andreff, B. Espiau. On displacing a screw about a screw I.A. Parkin, J.E. Baker. Algebraic solution of inverse kinematics revisited W. Korb, et al. A variant of a 6-RKS hunt-type parallel manipulator to easily use insensitivity position configurations I. Zabalza, et al. Kinematic Design. On the kinematics of parallel mechanisms with bi-stable polymer actuators A. Wingert, et al. The kinetostatic design of a Schonflies-motion generator K. Al-Widyan, J. Angeles. Design of 2-DOF parallel mechanisms for machining applications F. Majou, et al. Kinematically equivalent spatial mechanisms with revolute pair at input and prismatic pair at output E. Peisach. The optimal synthesis of parallel manipulators for desired work-spaces A.M. Hay, J.A. Snyman. Connecting assembly modes for

Micro-motion machine and micro-element fabricating machine using a 3 degree of freedom parallel mechanism

Abstract: The present invention is related to micro-motion machine and micro-element fabricating machine using a 3-degree-of-freedom parallel mechanism. A micro-motion machine achieves a 3-degree-of-freedom micro movement by connecting two arms connected to prismatic flexible joints respectively, adapted to conduct vertical movements, by revolute flexible joints, and one arm connected to another prismatic flexible joint, adapted to conduct vertical movements by universal joint, to a platform by universal joint. This micro-motion machine has a relatively simple and inexpensive construction, high stiffness, and high accuracy, while exhibiting reduced inertia. Where the parallel mechanism is applied to micro-element fabricating machines, and a tool device or workpiece table is positioned at the platform of the parallel mechanism to perform a desired one of cutting, electro-discharging, and laser machining processes suitable for the machining of micro-elements, it is possible to design a micro-element fabricating machine having advantages of a relatively large workspace, especially high mobility, and an ability to fabricate three dimensional micro-elements having diverse shapes, along with the advantages of parallel mechanisms.

CAT4 (Cable Actuated Truss—4 Degrees of Freedom): A Novel 4 DOF Cable Actuated Parallel Manipulator

Abstract: The CAT4 (Cable Actuated Truss—4 degrees of freedom) robot is a novel, passively jointed, parallel robot utilizing six control cables for actuation. The architecture has been under development at the Queen's University Robotics Laboratory. The robot utilizes a passive jointed linkage with 18 revolute joints to constrain the end effector motion and provide the desired structural stability, restricting the end effector to 3 translational degrees of freedom (DOF) and 1 DOF for end effector pitch. This central mechanism together with winched cable actuation gives a number of important benefits for applications where the advantages of a parallel robot are required in conjunction with light weight. Six electric motor driven winches control the length of the cable actuators that extend from the top frame to points on the end effector raft and jointed linkage to create a stiff, but lightweight, actuated robot. Simulation work on the robot is presented giving the kinematics, including a computational estimate of the workspace for a specific configuration. Results of computational simulation of the motion of the manipulator and a discussion of the advantages and potential difficulties are also presented. © 2002 Wiley Periodicals, Inc.

Two-freedom translational parallel robot mechanism containing only rotating sets

Abstract: A two degree-of-freedom translational parallel robot mechanism only containing a revolute pair is composed of a machine frame, two servo motors installed on the frame, a moving platform connected with the said frame via two branches to form a parallel closed-loop structure, and two branch chains eash containing two parallelogram mechanisms and used as drive and driven rod groups respectively. Itsadvantages include high speed, simple structure, low cost and light weight.

Fault-tolerant gaits of quadruped robots for locked joint failures

Abstract: This paper lays a theoretical foundation for fault detection and tolerance in static walking of legged robots. Legged robots considered in this paper have symmetric structures and legs which have the form of an articulated arm with three revolute joints. A kind of fault event (locked joint failure) is defined, and its properties are closely investigated in the frame of gait study and robot kinematics. For the purpose of tolerating a locked joint failure, an algorithm of fault-tolerant gaits for a quadruped robot is proposed in which the robot can continue its walking after a locked failure occurs to a joint of a leg. In particular, a periodic gait is proposed as a special form of the proposed algorithm and its existence and efficiency are analytically proven. A case study on applying the proposed scheme to wave gaits verifies its applicability and capability.

Mechanism design of a simplified 6-DOF 6-RUS parallel manipulator

Abstract: This paper concerns the issue of mechanism design of a simplified 6-DOF 6-RUS parallel manipulator. The design of robotic mechanisms, especially for 6-DOF parallel manipulators, is an important and challenging problem in the field of robotics. This paper presents a design method for robotic mechanisms, which is based on the physical model of the solution space. The physical model of the solution space, which can transfer a multi-dimensional problem to a two or three-dimensional one, is a useful tool to obtain all kinds of performance atlases. In this paper, the physical model of the solution space for spatial 6-RUS (R stands for revolute joint, U universal joint and S spherical joint) parallel manipulators is established. The atlases of performances, such as workspace and global conditioning index, are plotted in the physical model of the solution space. The atlases are useful for the mechanism design of the 6-RUS parallel manipulators. The technique used in this paper can be applied to the design of other robots.

Modelling of a novel rotary pneumatic muscle

Abstract: This paper describes a mathematical model for a novel rotary pneumatic rotary actuator with potential applications in revolute direct robotic mechanisms. The analytical model describes the behaviour of the rotary pneumatic actuator and simulated results using this model are generated. Potential applications of this model are discussed in the context of soft model based controllers used in prosthetic devices.

Solving the burmester problem using kinematic mapping

Abstract: Planar kinematic mapping is applied to the five-position Burmester problem for planar four-bar mechanism synthesis. The problem formulation takes the five distinct rigid body poses directly as inputs to generate five quadratic constraint equations. The five poses are on the fourth order curve of intersection of up to four hyperboloids of one sheet in the image space. Moreover, the five poses uniquely specify these two hyperboloids. So, given five positions of any reference point on the coupler and five corresponding orientations, we get the fixed revolute centres, the link lengths, crank angles, and the locations of the coupler attachment points by solving a system of five quadratics in five variables that always factor in such a way as to give two pairs of solutions for the five variables (when they exist).Copyright © 2002 by ASME

A Characterization of the Workspace Boundary of Three-Revolute Manipulators

Abstract: The aim of this work is to characterize the boundary workspace of three-revolute open chain manipulators by analyzing cusp points. A study is presented for the characteristic points of the workspace boundary of the three-revolute manipulators by using an algebraic formulation.Copyright © 2002 by ASME

A Polynomial Equation for a Coupler Curve of the Double Butterfly Linkage

Abstract: This paper presents a closed-form polynomial equation for the path of a point fixed in the coupler links of the single degree-of-freedom eight-bar linkage commonly referred to as the double buttery linkage. The revolute joint that connects the two coupler links of this planar linkage is a special point on the two links and is chosen to be the coupler point. A systematic approach is presented to obtain the coupler curve equation, which expresses the Cartesian coordinates of the coupler point as a function of the link dimensions only; i.e., the equation is independent of the angular joint displacements of the linkage. From this systematic approach, the polynomial equation describing the coupler curve is shown to be, at most, forty-eighth order. This equation is believed to be an original contribution to the literature on coupler curves of a planar eight-bar linkage. The authors hope that this work will result in the eight-bar linkage playing a more prominent role in modern machinery.

Workspace analysis and singularity representation of three-legged parallel manipulators

Abstract: This paper presents a numerical algorithm for the analysis of reachable workspace and singularity representation of three-legged parallel manipulators. After finding out the approximate maximum workspace, a radial and equal area discretization is done. Then, a multitasking search is performed to determine the exact workspace boundary. The volume of the workspace is determined easily by a numerical integration method. Any void inside the workspace is found out. information about its position and stretch is determined and singularity curves inside the workspace is also drawn. A three-legged modular parallel manipulator is considered to demonstrate the effectiveness of the algorithm and found to work quite satisfactorily. The model is based on Product-of-Exponential scheme of formulation and, hence, the algorithm is uniformly applicable to any combinations of revolute and prismatic joints in the configuration of the leg.

Interlocked open linkages with few joints

Abstract: We advance the study of collections of open linkages in 3-space that may be interlocked in the sense that the linkages cannot be separated without one bar crossing through another. We consider chains of bars connected with rigid joints, revolute joints, or universal joints and explore the smallest number of chains and bars needed to achieve interlock. Whereas previous work used topological invariants that applied to single or to closed chains, this work relies on geometric invariants and concentrates on open chains.