Showing papers on "Revolute joint published in 2012"

The effect of the lubricated revolute joint parameters and hydrodynamic force models on the dynamic response of planar multibody systems

Abstract: In this work a comprehensive methodology for dynamic modeling and analysis of planar multibody systems with lubricated revolute joints is presented. In general, this type of mechanical systems includes journal-bearings in which the load varies in both magnitude and direction. The fundamental issues associated with the theory of lubrication for dynamically loaded journal-bearings are revisited that allow for the evaluation of the Reynolds equation for dynamic regime. This approach permits the derivation of the suitable hydrodynamic force laws that are embedded into the dynamics of multibody systems formulation. In this work, three different hydrodynamic force models are considered, namely the Pinkus and Sternlicht approach for long journal-bearings and the Frene et al. models for both long and short journal-bearings. Results for a planar slider–crank mechanism with a lubricated revolute joint between the connecting-rod and slider are presented and utilized to discuss the assumptions and procedures adopted throughout the present study. Different test scenarios are taken into account with the purpose of performing a comparative study for quantifying the effect of the clearance size, lubricant viscosity, input crank speed and hydrodynamic force model on the dynamic response of multibody systems with lubricated revolute joints. From the global results obtained from computational simulations, it can be concluded that the clearance size, the lubricant viscosity and the operating conditions play a key role in predicting the dynamic behavior of multibody systems.

Dynamic analysis of planar multi-body systems with LuGre friction at differently located revolute clearance joints

Abstract: In this paper, the dynamic response of a planar rigid multi-body system with stick–slip friction in revolute clearance joints is studied. LuGre friction law is proposed to model the stick–slip friction at the revolute clearance joints. This is because using this law, one can capture the variation of the friction force with slip velocity, thus making it suitable for studies involving stick–slip motions. The effective coefficient of friction is represented as a function of the relative tangential velocity of the contacting bodies, that is, the journal and the bearing, and an internal state. In LuGre friction model, the internal state is considered to be the average bristle deflection of the contacting bodies. By applying the LuGre friction law on a typical slider–crank mechanism, the friction force in the revolute joint having clearance is seen not to have a discontinuity at zero slip velocity throughout the simulation unlike in static friction models. In addition, LuGre model was observed to capture the Stribeck effect which is a phenomenon associated directly with stick–slip friction. The friction forces are seen to increase with increase in input speed. The effect of stick–slip friction on the overall dynamic behavior of a mechanical system at different speeds was seen to vary from one clearance joint to another.

Investigation of joint clearance effects on welding robot manipulators

Abstract: In this study, effects of joint clearance on a welding robot manipulator are investigated. Theoretical analysis is performed for different clearance sizes. By using the nonlinear spring-damper characteristic, contact model in revolute joint with clearance is established and the friction effect is performed using the Coulomb friction model. Then the simulation is carried out to investigate the kinematic and dynamic characteristics of the welding robot manipulator with joint clearance. For the case of two different clearance sizes, the results show that the joint clearance causes to degradation of kinematic and dynamic performance of the system. Even if the clearance size is small, it has a crucial role on amplitudes of the end-effector's accelerations and joint forces.

Vehicle seat backrest with flexural joint motion-control

Abstract: A vehicle seat includes a backrest coupled to an upwardly extending support frame. The backrest includes a deformable seat shell adapted to assume various shapes between an initial position and a final position in response to variable rearward loads applied by the torso of a seated passenger. The seat shell is coupled to the support frame by a compliant shell-motion controller via upper and lower motion-control links. At least one of the motion-control links includes a flexural portion configured to bend about a pivot axis to establish a flexural joint. The lower motion-control link may include a flexural joint and/or a revolute joint, and the upper motion control link may include a flexural, revolute, or spheroidal joint.

Analysis of the Dynamic Behavioral Performance of Mechanical Systems With Multi–Clearance Joints

Abstract: In this investigation, the effect of revolute joints’ clearance on the dynamic performance of mechanical systems is reported. A computation algorithm is developed with the aid of SolidWorks/CosmosMotion software package. A slider-crank mechanism with one and two clearance-joints is studied and analyzed when working in vertical and in horizontal planes. The simulation results point out that the presence of such clearance in the joints of the system understudy leads to high peaks in the characteristic curves of its kinematic and dynamic performance. For a multiclearance joints mechanism, the maximum impact force at its joints takes its highest value at the nearest joint to the input link. This study also shows that, when the mechanism works in horizontal plane, the rate of impacts at each clearance-joint increases and consequently the clearance-joints and actuators will deteriorate faster.

Dynamics modeling and quantitative analysis of multibody systems including revolute clearance joint

Abstract: The dynamics characteristics of multibody mechanical systems including revolute joints with clearance are investigated using a computational methodology and a quantitative analysis method is proposed in this work. The contact force model in revolute joint clearance is performed using a nonlinear continuous contact force model and the friction effect is considered using a modified Coulomb friction model. The planar four-bar mechanism is used as demonstrative application example to validate the quantitative analysis method. Numerical results for four-bar mechanism with revolute clearance joint are presented and discussed. Further, two kinds of dimensionless indicator are defined for quantitative analysis of mechanical system with joint clearance. And the clearance size, friction effects and crank driving speed are analyzed separately.

Occlusion-aware reconstruction and manipulation of 3D articulated objects

Abstract: We present a method to recover complete 3D models of articulated objects. Structure-from-motion techniques are used to capture 3D point cloud models of the object in two different configurations. A novel combination of Procrustes analysis and RANSAC facilitates a straightforward geometric approach to recovering the joint axes, as well as classifying them automatically as either revolute or prismatic. With the resulting articulated model, a robotic system is able to manipulate the object along its joint axes at a specified grasp point in order to exercise its degrees of freedom. Because the models capture all sides of the object, they are occluded-aware, enabling the robotic system to plan paths to parts of the object that are not visible in the current view. Our algorithm does not require prior knowledge of the object, nor does it make any assumptions about the planarity of the object or scene. Experiments with a PUMA 500 robotic arm demonstrate the effectiveness of the approach on a variety of objects with both revolute and prismatic joints.

Aircraft component attitude adjusting assembly system based on parallel mechanism with six degrees of freedom and debugging method

Abstract: The invention discloses an aircraft component attitude adjusting assembly system based on a parallel mechanism with six degrees of freedom, comprising an aircraft part attitude adjusting structure and a laser tracking system, wherein the position relationship therebetween is that the laser tracking system is arranged around the aircraft part attitude adjusting structure. The aircraft component attitude adjusting mechanism comprises an aircraft part the attitude of which to be adjusted, two PSS branch chains, two PRRS branch chains, a quiet platform for fixing the guide rails at the lowest ends of the four branch chains, the position relationship is as follows: two ends of the two PSS branch chains are connected with an aircraft part and a spherical hinge auxiliary sliding block through a spherical hinge, the guide rails are fixed on the quiet platform; one end of the two PRRS branch chains is connected with the aircraft part through the spherical hinge, the other end is connected witha revolute pair sliding block through a revolute pair, the revolute pair sliding block and an upper guide rail from a sliding pair, the upper guide rail and a lower guide rail form a sliding pair, and the lower guide rail is fixed on the quiet platform. The laser tracking system comprises a laser tracker and enclosures thereof. The system adjusting method comprises seven steps. The invention realizes arbitrary adjustment of space of parts to be assembled, employs laser detection, and ensures assembling accuracy.

Contributions to high-gain adaptive control in mechatronics

Abstract: High-gain adaptive control and its applications in mechatronics are discussed. The high-gain adaptive controllers are presented and developed for "minimum-phase" systems with relative degree one or two, known sign of the high-frequency gain, bounded disturbances and state dependent, functional perturbations. System identification or parameter estimation is not required for controller implementation. Structural system knowledge is sufficient. The robust controllers guarantee tracking with prescribed asymptotic or transient accuracy and, in combination with a proportional-integral internal model, may assure steady state accuracy. Finally, the controllers are applied for speed and position control of stiff and flexible industrial servo-systems and it is shown that high-gain adaptive position control with prescribed transient accuracy of rigid revolute joint robotic manipulators is feasible, if the inertia matrix is known.

Design and Modeling of a Large-Range Modular XYZ Compliant Parallel Manipulator Using Identical Spatial Modules

Abstract: A design methodology of XYZ compliant parallel manipulators (CPMs) is introduced at first. A spatial double four-beam module and a compliant P (prismatic) joint, composed of two spatial double four-beam modules, are then proposed. Starting from a 3-PPPR (R: revolute) translational parallel manipulator, a large-range modular XYZ CPM with identical spatial modules is constructed using the proposed design approach. Normalized analytical models for the large-range modular XYZ CPM are further presented. As a case study, a modular XYZ CPM with a motion range of 10mm×10mm×10mm is presented in detail, covering the geometrical parameter determination, performance characteristics analysis, buckling check, and actuation force check. The analytical models are compared with the finite element analysis (FEA) models. Finally, the dynamic issues, manufacturability and merits are discussed. It is shown that the proposed large-range modular XYZ CPM has the following main merits compared with existing designs: (1) large range of motion up to 10mm×10mm×10mm, and (2) reduced number of design parameters through the use of identical spatial modules, although the manufacturability is a challenging issue.

Distance-based Formulations for the Position Analysis of Kinematic Chains

Abstract: This thesis addresses the kinematic analysis of mechanisms, in particular, the position analysis of kinematic chains, or linkages, that is, mechanisms with rigid bodies (links) interconnected by kinematic pairs (joints). This problem, of completely geometrical nature, consists in finding the feasible assembly modes that a kinematic chain can adopt. An assembly mode is a possible relative transformation between the links of a kinematic chain. When an assignment of positions and orientations is made for all links with respect to a given reference frame, an assembly mode is called a configuration. The methods reported in the literature for solving the position analysis of kinematic chains can be classified as graphical, analytical, or numerical. The graphical approaches are mostly geometrical and designed to solve particular problems. The analytical and numerical methods deal, in general, with kinematic chains of any topology and translate the original geometric problem into a system of kinematic analysis of all the Assur kinematic chains resulting from replacing some of its revolute joints by slider joints. Thus, it is concluded that the polynomials of all fully-parallel planar robots can be derived directly from that of the widely known 3-RPR robot. In addition to these results, this thesis also presents an efficient procedure, based on distance and oriented area constraints, and geometrical arguments, to trace coupler curves of pin-jointed Gr¨ubler kinematic chains. All these techniques and results together are contributions to theoretical kinematics of mechanisms, robot kinematics, and distance plane geometry. equations that defines the location of each link based, mainly, on independent loop equations. In the analytical approaches, the system of kinematic equations is reduced to a polynomial, known as the characteristic polynomial of the linkage, using different elimination methods —e.g., Gr¨obner bases or resultant techniques. In the numerical approaches, the system of kinematic equations is solved using, for instance, polynomial continuation or interval-based procedures. In any case, the use of independent loop equations to solve the position analysis of kinematic chains, almost a standard in kinematics of mechanisms, has seldom been questioned despite the resulting system of kinematic equations becomes quite involved even for simple linkages. Moreover, stating the position analysis of kinematic chains directly in terms of poses, with or without using independent loop equations, introduces two major disadvantages: arbitrary reference frames has to be included, and all formulas involve translations and rotations simultaneously. This thesis departs from this standard approach by, instead of directly computing Cartesian locations, expressing the original position problem as a system of distance-based constraints that are then solved using analytical and numerical procedures adapted to their particularities. In favor of developing the basics and theory of the proposed approach, this thesis focuses on the study of the most fundamental planar kinematic chains, namely, Baranov trusses, Assur kinematic chains, and pin-jointed Gr¨ubler kinematic chains. The results obtained have shown that the novel developed techniques are promising tools for the position analysis of kinematic chains and related problems. For example, using these techniques, the characteristic polynomials of most of the cataloged Baranov trusses can be obtained without relying on variable eliminations or trigonometric substitutions and using no other tools than elementary algebra. An outcome in clear contrast with the complex variable eliminations require when independent loop equations are used to tackle the problem. The impact of the above result is actually greater because it is shown that the characteristic polynomial of a Baranov truss, derived using the proposed distance-based techniques, contains all the necessary and sufficient information for solving the position

Computed muscle control for an anthropomimetic elbow joint

Abstract: The soft robotics approach is widely considered to enable human-friendly robots which are able to work in our future homes and factories. Furthermore, achieving the smooth and natural movements of humans has become a hot topic in robotics, especially when robots are supposed to work in close proximity to humans. The anthropomimetic principle aims at mimicking not only the outside but also the inner mechanisms of the human body in humanoid robots. However, for this class of robots there exist as yet no scalable controllers that might make it possible to control a full body, or even several joints. A very similar problem is ongoing research in biomechanics which is the computation of muscle excitation patterns for coordinated movements. For this purpose, biomechanicists have developed computed muscle control which has proven a very scalable technique. In this paper, we demonstrate the adaptation of computed muscle control for a tendon-driven robot, comparing different methods for obtaining the muscle kinematics, as well as different low-level controllers. Results are shown for the implementation on a distributed control architecture and a single revolute elbow joint.

An autonomous image-guided robotic system simulating industrial applications

Abstract: This paper presents a robotic system based on a serial manipulator. The robot is a vertical articulated arm with 5 revolute joints having 6 Degree Of Freedom. Actuated with six precise servo motors, the system offers positional accuracy of ±0.5mm with a movement speed of 100mm/s. Forward and Inverse Kinematic model of the robot has been developed and its workspace has been analyzed to facilitate the use of robotic arm as a simulated industrial manipulator. Image processing has been done to make system more autonomous. Followed by a user's commands, the system acquires image of the environment using on-board camera. This image is processed to extract information about object's coordinates. Based on these coordinates, Inverse Kinematic model computes the required joint angles for the end-effector to reach at desired position and orientation thus enabling it to manipulate the object. The proposed system can be used in wide range of industrial applications involving pick and place, sorting and other object manipulation tasks. The system can also be potentially useful for heavy and ‘giant’ industrial applications after scaling up i.e. using huge robotic arm, employing multiple and better cameras and optimizing algorithms.

Steerable assembly for surgical catheter

Abstract: A catheter (10) configured for intraluminal delivery to a location in the body of a patient, the catheter comprising a steerable assembly (28) comprising a first segment (50) connected to a second segment (52); the first segment comprises first and second cylindrical elements (30) connected to each other by a first revolute joint in a first single plane; the second segment comprises third and fourth cylindrical elements (30) connected to each other by a second revolute joint in a second single plane, wherein the first single plane and the second single plane are offset by an angle from each other.

Influence of Contact Geometry on Local Friction Energy and Stiffness of Revolute Joints

Abstract: Revolute joints (also called pin joints or hinge joints) are used in many different mechanical systems such as robotic arms, door hinges, folding mechanisms, or hydraulic shovels. Since they transmit forces and give a rotational degree of freedom to the connected parts, revolute joints have a major impact on the dynamic behavior of the system into which they are built. Two main characteristics of these elements are their stiffness and their clearance. Both of them change as the wear between the joint’s pin and the rod hole increases during operation. In order to consider these aspects in a multibody simulation an analytical, numerically effective method has been developed to calculate the stiffness of a revolute joint in dependence of the geometry and the wear state. In addition, the calculation algorithm allows for for the analysis of the local friction energy that occurs in the contact zone. In this paper, the calculation approach is presented together with the results for two different steady loaded revolute joints.

Denavit-Hartenberg Parameterization of Euler Angles

Abstract: Euler angles describe rotations of a rigid body in three-dimensional Cartesian space, as can be obtained by, say, a spherical joint. The rotation carried out by a spherical joint can also be expressed by using three intersecting revolute joints that can be described using the popular Denavit-Hartenberg (DH) parameters. However, the motions of these revolute joints do not necessarily correspond to any set of the Euler angles. This paper attempts to correlate the Euler angles and DH parameters by introducing a concept of DH parameterization of Euler angels. A systematic approach is presented in order to obtain the DH parameters for any Euler angles set. This gives rise to the concept of Euler-angle-joints (EAJs), which provide rotations equivalent to a particular set of Euler angles. Such EAJs can be conveniently used for the modeling of multibody systems having multiple-degrees-of-freedom joints.

Position funnel control for rigid revolute joint robotic manipulators with known inertia matrix

Abstract: This paper presents funnel control for position control of rigid, revolute joint, n-degree-of-freedom (DOF) robotic manipulators with known inertia matrix. The multi-input multi-output (MIMO) funnel controller assures reference tracking with ‘prescribed transient accuracy’, i.e., for each joint, the absolute value of position and speed tracking error (difference between reference and actual value) is bounded by a prescribed, positive (possibly non-increasing) function of time (the ‘funnel boundary’), respectively.

Constraint force design method for topology optimization of planar rigid-body mechanisms

Abstract: This study develops a new design method called the constraint force design method, which allows topology optimization for planar rigid-body mechanisms. In conventional mechanism synthesis methods, the kinematics of a mechanism are analytically derived and the positions and types of joints of a fixed configuration (hereafter the topology) are optimized to obtain an optimal rigid-body mechanism tracking the intended output trajectory. Therefore, in conventional methods, modification of the configuration or topology of joints and links is normally considered impossible. In order to circumvent the fixed topology limitation in optimally designing rigid-body mechanisms, we present the constraint force design method. This method distributes unit masses simulating revolute or prismatic joints depending on the number of assigned degrees of freedom, analyzes the kinetics of unit masses coupled with constraint forces, and designs the existence of these constraint forces to minimize the root-mean-square error of the output paths of synthesized linkages and a target linkage using a genetic algorithm. The applicability and limitations of the newly developed method are discussed in the context of its application to several rigid-body synthesis problems.

Two-orbit switch-pitch structures

Abstract: The Hoberman ‘switch-pitch’ ball is a transformable structure with a single folding and unfolding path. The underlying cubic structure has a novel mechanism that retains tetrahedral symmetry during folding. Here, we propose a generalized class of structures of a similar type that retain their full symmetry during folding. The key idea is that we require two orbits of nodes for the structure: within each orbit, any node can be copied to any other node by a symmetry operation. Each member is connected to two nodes, which may be in different orbits, by revolute joints. We will describe the symmetry analysis that reveals the symmetry of the internal mechanism modes for a switch-pitch structure. To follow the complete folding path of the structure, a nonlinear iterative predictor-corrector algorithm based on the Newton method is adopted. First, a simple tetrahedral example of the class of two-orbit structures is presented. Typical configurations along the folding path are shown. Larger members of the class of structures are also presented, all with cubic symmetry. These switch-pitch structures could have useful applications as deployable structures.

Planar, bimanual, whole-arm grasping

Abstract: We address the problem of synthesizing planar, bimanual, whole-arm grasps by developing the abstraction of an open chain gripper, an open, planar chain of rigid links and revolute joints contacting a planar, polygonal object, and introducing the concept of a generalized contact Since two generalized contacts suffice for planar grasps, we leverage previous work on caging and immobilization for two contact grasps to construct an algorithm which synthesizes contact configurations for stable grasping Simulations show that our methodology can be applied to grasp a wide range of planar objects without relying on special-purpose end-effectors Representative experiments with the PR2 humanoid robot illustrate that this approach is practical

Three-degree-of-freedom parallel-connection mechanical wrist

Abstract: The invention relates to a three-degree-of-freedom parallel-connection mechanical wrist which comprises a base, a movable platform, a constrain driving branch chain used for connecting the base with the movable platform, and two driving branch chains which are same in structure, wherein the two ends of the three branch chains are symmetrically distributed in a regular triangle shape together with the base and the movable platform; the constrain driving branch chain consists of two revolute pairs and a driving sliding pair, so that a resilient packet ring (RPR)-type series-connection structural branch chain can be formed; the constrain driving branch chain is connected with the base and the movable platform by virtue of the revolute pairs; the two driving branch chains which are completely the same as each other respectively comprise a universal pair, a movable driving pair and a spherical hinge, so that an uninterrupted power supply (UPS)-type series-connection structural branch chain can be formed; and the two driving branch chains are respectively connected with the base by virtue of the universal pairs, and connected with the movable platform by virtue of the spherical hinges. The three-freedom parallel-connection mechanical wrist has the advantages of being strong in carrying capacity, good in stability, large in work space, high in flexibility, simple in structure, fewer in moving branch chains, hard to interfere, free from self micro-movement, high in accuracy, easy to control since a driver is close to the base, etc.