Showing papers on "Revolute joint published in 2019"
TL;DR: In this paper, the effects of joint clearance, panel flexibility and their coupling on dynamic behavior of planar rigid-flexible coupling solar array system considering joint clearance in depth are numerically analyzed.
85 citations
TL;DR: In this article, a hybrid friction model is presented to analyze the dynamics of planar mechanical systems, considering sliding, sticking and Stribeck effect in revolute clearance joints, where the relative tangential motion between the journal and the bearing is categorized as sticking state, sliding state and transitional state.
Abstract: The phenomena of friction in clearance joints have time- dependent nonlinear characteristics, which could lead to undesirable and unstable dynamic behavior of mechanical systems. Various mathematical models have been proposed to describe friction force in clearance joints. However, most of the previous models have different limitations, such as discontinuity at zero velocity or disability of detecting stick-slip motion. In this paper, a hybrid friction model is presented to analyze the dynamics of planar mechanical systems, considering sliding, sticking and Stribeck effect in revolute clearance joints. According to the kinematic analysis, the relative tangential motion between the journal and the bearing is categorized as sticking state, sliding state and transitional state. In the sticking state, an assumed acceleration constraint for the contact points is proposed to estimate the static friction force. This method not only eliminates the calculation of the implicit external force, but also accurately reflects the sticking process in accordance with the friction physics. Furthermore, the Stribeck effect is introduced in the description of the friction force in the sliding state, revealing the influence of the sliding velocity on the friction force. The stick-slip motion could also be accurately described by the Stribeck effect, which guarantees the continuity of the friction force during the transition process. Finally, a space robot manipulator is taken as an example to demonstrate the hybrid friction model. Dynamics of the space robot manipulator with Coulomb friction model, LuGre friction model, Wojewoda friction model and the hybrid friction model are compared, respectively. And the effects of clearance size, static friction coefficient and sliding friction coefficient on the dynamics of the manipulator are also analyzed.
41 citations
TL;DR: A novel revolute joint of variable stiffness with reconfigurability (JVSR) is presented, which is able to vary widely its stiffness in multiple modes, namely, linear, hardening and softening modes.
40 citations
TL;DR: The SSM represents a simplification of a spatial spherical mechanism design and overcomes the need for the use of redundant links and optimization routines.
39 citations
TL;DR: The approach of synthesis based on manifold-operation provides a distinct rationale for this paper, and analysis of motion and constraint conditions transmitted to the platform through subchains is essential, to enable the reconfiguration aimed type synthesis of metamorphic parallel mechanisms.
38 citations
TL;DR: A simple and highly visual approach for the type synthesis of a family of overconstrained parallel mechanisms that have one translational and two rotational movement capabilities, leading to a novel five degrees of freedom hybrid module named TriMule.
Abstract: This paper presents a simple and highly visual approach for the type synthesis of a family of overconstrained parallel mechanisms that have one translational and two rotational movement capabilities. It considers, especially, mechanisms offering the accuracy and dynamic response needed for machining applications. This family features a spatial limb plus a member of a class of planar symmetrical linkages, the latter connected by a revolute joint either to the machine frame at its base link or to the platform at its output link. Criteria for selecting suitable structures from among numerous candidates are proposed by considering the realistic practical requirements for reconfigurability, movement capability, rational component design and so on. It concludes that a few can simultaneously fulfil the proposed criteria, even though a variety of structures have been presented in the literature. Exploitation of the proposed structures and evaluation criteria then leads to a novel five degrees of freedom hybrid module named TriMule. A significant potential advantage of the TriMule over the Tricept arises because all the joints connecting the base link and the machine frame can be integrated into one single, compact part, leading to a lightweight, cost effective and flexible design particularly suitable for configuring various robotized manufacturing cells.
37 citations
TL;DR: Results of six comparison models show that the coupling effect of thermal environment and overall motion brings dramatic and unmanageable shock to the system with clearance joint, that is no longer can be seen as a simple superposition of each single condition effect like theSystem with ideal joint.
Abstract: This paper establishes a thermal-structural coupling model of planar spacecraft system with large flexible composite solar array under nodal coordinate formulation and absolute nodal coordinate formulation framework. Perfect revolute joint is adopted as connection type to give the different influences from fixed constraint used in previous researches, and consequently, torsional spring, latch mechanism, and attitude controller are involved into the spacecraft system. Imperfect revolute joint is further introduced to investigate the coupling effects of thermal load, adjustment motion, and joint clearance on dynamics of the system, including spacecraft attitude, solar panel responses, and wear prediction. Results of six comparison models (with or without clearance joint, considering thermal environment, or adjustment motion, and considering both these two conditions) show that the coupling effect of thermal environment and overall motion brings dramatic and unmanageable shock to the system with clearance joint, that is no longer can be seen as a simple superposition of each single condition effect like the system with ideal joint, although the suspension damper property of clearance joint can weaken thermal-induced vibration or motion induced vibration separately. For a period after attitude adjustment, wear depth of the system subjected to solar radiation is two orders of magnitude lager than that of the system without considering thermal environment. Joint clearance and thermal environment should be considered both; for on-orbit spacecraft system, the coupling effects of them are significant and non-ignorable for relevant mechanism design and performance analysis.
33 citations
TL;DR: A comprehensive methodology to study the dynamic responses of multibody dynamics with revolute clearance joint is presented, which is based on an improved nonlinear impact force model and a modified friction force model.
32 citations
TL;DR: The main objective is to develop the dynamics of closed kinematic cooperative manipulators by defining constraints in mobile form while considering the geometric dimensions of the common object instead of assuming a concentrated mass in the gripper as the application of manipulator with flexible links and revolute-prismatic joints in the constrained cooperative mobile form.
32 citations
23 Jun 2019
TL;DR: From the experiments conducted, it is concluded that both ANN and ANFIS converged to some degree to the underlying inverse kinematics function, however approximation errors and the time and effort required to achieve those results may not justify their use vis-a-vis other methods in the literature.
Abstract: One of the most important problems in robotics is the computation of the inverse kinematics (IK). This apparently simple task is necessary to determine how to move each joint in order to reach a desired end-effector pose in Cartesian space. However, the associated forward kinematics can be a highly nonlinear, non-bijective, and multidimensional function for which it may be difficult or even impossible to find closed-form solutions for its inverse – especially as the number of Degrees of Freedom (DoF) increases. Several approaches have been taken using non-linear approximators to solve IK problems. In this paper, we present a study on solving the inverse kinematics of multiple robotic arms using Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference Systems (ANFIS). For this study, we experimented with 4, 5, 6 and 7 DoF serial robots, with combinations of prismatic and revolute joints. Unlike other task-oriented solvers, our goal was not to predict poses based on specific trajectories (linear or otherwise), but instead to learn the entire robot workspaces. This goal better addresses real-world uses of robotic IK, where any end-effector pose should be reachable from any current pose. From the experiments conducted, we conclude that both ANN and ANFIS converged to some degree to the underlying inverse kinematics function, however approximation errors and the time and effort required to achieve those results may not justify their use vis-a-vis other methods in the literature.
31 citations
TL;DR: In this article, a numerical model for the lubricated full-floating pin bearings in multibody mechanical systems was developed by embedding the hydrodynamic lubrication and solid contact forces in the revolute joint clearance.
TL;DR: A prehensive assessment of the current contact force models implemented in the MultiBody Dynamics (MBD) approach is performed, validating the need of a new model that is able to evaluate with accuracy the contact forces obtained, and a benchmark problem is presented through a 3D slider–crank mechanism.
Abstract: In this work a new approach to deal with non-ideal operative aspects of spatial revolute joints by means of a three-dimensional finite element analysis (3D-FEA) is presented. The developed model incorporates the inertia of the joint components and the corresponding material properties. The fact that actual joint mechanical components present dimensional and geometrical deviations resulting from the assembly process and operative conditions lead to frequent modifications relative to the design conditions that are worth analyzing. Such nonconformities include manufacturing tolerances and assembly errors, thermal effects, local deformations and clearances that directly affect the behavior and reliability of a mechanism, as they are typically at the origin of vibrations, noise and wear. In this work, a comprehensive assessment of the current contact force models implemented in the MultiBody Dynamics (MBD) approach is performed with the aim of understanding its main flaws and weaknesses, validating the need of a new model that is able to evaluate with accuracy the contact forces obtained. Finally, a benchmark problem is presented through a 3D slider–crank mechanism, allowing for the recognition of the differences that exist when the problem is analyzed by means of the MBD and FEM formulations. For this purpose, one of the joints is modeled as non-ideal, with both radial and axial clearances, the ultimate goal of which is to combine both approaches and, thus establish a crucial and pioneering connection to solve the contact problem.
TL;DR: An improved computational methodology for the modeling and simulation of a planar flexible MLM with clearance and spindle-bearing structure is presented considering the effect of clearance, flexibility of crankshaft and linkage, and bearing stiffness together, and its corresponding dynamic dimension chain between the slider and crank shaft is constructed.
TL;DR: The dynamic transmission error, computed on the basis of the proposed methodology, has been successfully compared with experimental data available in literature and allows to evaluate the accuracy of the estimated stiffness values.
TL;DR: This paper proposes a method to analyze the angular errors of the multi-closed-loop deployable mechanism of the planar synthetic-aperture radar antenna considering link deviations and joint clearances using the rotatability law of the single-loop linkage.
TL;DR: A novel robotic tail system capable of spatial motion to generate spatial loading, and a dynamic model of the tail is presented, along with considerations for sensing the robot's state and controlling the tail.
Abstract: In nature, tails are a key feature in numerous animals that help stabilize, maneuver, manipulate, and/or propel. However, prior research on robotic tails has focused on limited degree of freedom (DOF), pendulum-like structures designed for a single function. This paper presents a novel robotic tail system capable of spatial motion to generate spatial loading. The roll–revolute–revolute robotic tail (R3RT) is a serpentine robotic structure with a roll-DOF at the tail base, and two independently actuated coplanar bending segments composed of several links connected by parallel revolute joints. A dynamic model of the tail is presented, along with considerations for sensing the robot's state and controlling the tail. The inertial loading capabilities of the tail are analyzed using the dynamics model and experimentally validated using an integrated prototype of the R3RT to present loading analysis and the performance benefits of tail articulation. Results of the analysis are promising and indicate clear directions for improvement in a future work.
22 Jul 2019
TL;DR: A novel three degree-of-freedom finger mechanism that features excellent impact absorbing performance, high force, and precision comparable to human hands and a unique tendon guiding structure, which enables accurate kinematic modeling even though it is composed of soft and flexible materials is proposed.
Abstract: This letter presents a novel three degree-of-freedom finger mechanism that features excellent impact absorbing performance, high force, and precision comparable to human hands. Inspired by human fingers, it has a simple structure with a minimum number of rigid components: seven rigid frames, several polymer wires, and flexible sheets. For impact absorption, rolling contact joints with a center ligament, instead of conventional revolute joints with bearings or bushings, were used. While this mechanism can be dislocated in the event of off-axis bending or twisting force and impact, it can return afterward without degrading precision. To achieve precise manipulation performance, a unique tendon guiding structure, which enables accurate kinematic modeling even though it is composed of soft and flexible materials, is proposed. To prevent loss of precision and robustness against friction, the whole mechanism is covered by an artificial skin and filled with lubrication liquid, which is similar to human synovial fluid. The developed finger mechanism can exert 40 N fingertip force in a straight pose and has 0.2 mm repeatability of fingertip position under multiple impacts. Various experiments including button clicking and wheel rotation of a computer mouse demonstrated the performance and potential usefulness of the proposed mechanism.
TL;DR: An integrated non-probabilistic kinematic analysis of precision mechanisms with non-uniform wear in joint is presented by combining multi-body dynamic analysis, wear prediction and kinematics reliability analysis.
TL;DR: In this article, the effect of friction on the dynamic behavior of a crank-slider mechanism with clearance joint was investigated. But the authors only considered the acceleration and energy consumption of the mechanism, and they did not consider the clearance existence in the revolute joint.
Abstract: In this paper, we are interested in the effect of friction on dynamic behavior of a crank-slider mechanism with clearance joint. Due to the clearance existence in the revolute joint, it is important to choose an appropriate contact force model to analyze the dynamic response, the dynamic equations are established by combining Lagrange’s equation of the first kind with modified contact force model and LuGre friction model, the Baumgarte stabilization approach was used to improve the numerical stability. Simulation and experimental tests were carried out to verify this model. The system dynamic response hysteresis, and the more energy consumption when friction is considered in the mechanism. The influence of friction coefficient on the nonlinear dynamic characteristics of the mechanism with clearance joint is analyzed. The dynamic performance of the mechanism considering friction presents significant differences at the accelerations level. Friction plays a positive role in the stability of the system.
TL;DR: In this paper, a novel 6R metamorphic mechanism by inserting two revolute joints to a Bennett mechanism is presented, which is a special case of the Bricard 6R line-symmetric mechanism while the closure equation gives constraint conditions of joints.
TL;DR: In this paper, a multi-objective optimization game algorithm (MOOGA) for parallel manipulators (PMs) is proposed, which considers the volume of the regular cylindrical workspace, motion/force transmission performance, and stiffness performance as objective functions.
TL;DR: The finite element kinematic and dynamic formulation was successfully developed and validated for the flexible robot, in which a transformation matrix is proposed to describe the kinematics of both the joint motion and the link deformation.
TL;DR: An approach for modelling a clearance revolute joint with a constantly updating wear profile in a multibody system is proposed and the results verified that the extent of wear on the joint bushing profile is nonuniform, which is related to the kinetic characteristics of the mechanism.
Abstract: An approach for modelling a clearance revolute joint with a constantly updating wear profile in a multibody system is proposed. Before the contact analysis, the continuous geometric shape of the joint bushing is dispersed to obtain a series of uniformly distributed points of a certain density. By analysing the relative positions between the discrete points and geometric centre of the joint pin, the contact area between the bushing and pin can be estimated and the maximum contact depth can be obtained. Then, the normal contact force and the tangential friction force acting on the point of force application are calculated: after an analysis of the contact force, the wear depth on the contact discrete points is calculated based on Archard’s wear model. The location of the contact discrete point is updated to reconstruct the geometric shape of joint bushing. Finally, taking a planar slider–crank mechanism as an example, the wear characteristics and dynamic response of a revolute joint with clearance are studied by numerical simulation and experimental testing. The results verified that the extent of wear on the joint bushing profile is nonuniform, which is related to the kinetic characteristics of the mechanism. Due to wear, the joint clearance is increased, which further affects the dynamic performance of the mechanism.
TL;DR: Analysis of the effect of multiple clearances and different friction models on the dynamic behavior of a planar multi-DOF mechanism can provide theoretical basis for grasping the dynamic behaviors of the planar rigid-body mechanism with clearancesand identifying chaos of clearance joints.
Abstract: The clearance joint is one of the important factors which influence system performance and dynamic characteristics. Traditional studies are mainly focused on the planar single degree of freedom (DOF) simple mechanism with one joint clearance, only few researchers investigated mechanisms with more than one DOF considering more than one clearance joint as an object, and few studies systematically analyzed nonlinear characteristics of the clearance joints. This article is devoted to analyzing the effect of multiple clearances and different friction models on the dynamic behavior of a planar multi-DOF mechanism. The 2 DOFs nine bar planar mechanism is selected as the research object. The dynamic model of the planar mechanism with two revolute clearances is built by considering Lagrange equation. The influence of LuGre model and modified Coulomb friction model on the dynamic response of the nine bar mechanism is studied. The effects of the number of clearance joints, clearance values, driving speeds and friction coefficients on the dynamic responses of the mechanism are analyzed. The chaos phenomenon existing in the clearance revolute joints is identified by phase diagram, Poincare map and largest Lyapunov exponent (LLE). Bifurcation diagrams of revolute clearance joints with changing clearance values, driving speeds and friction coefficients are also drawn. A virtual prototype model of 2 DOF nine bar mechanism containing two revolute clearances is built by using ADAMS software to verify the correctness of the numerical results. This research can provide theoretical basis for grasping the dynamic behavior of the planar rigid-body mechanism with clearances and identifying chaos of clearance joints.
TL;DR: A simple and effective methodology for modeling and simulating frictional translational clearance joint in planar multibody systems including a flexible slider part using the finite element method.
TL;DR: A monocular camera mounted on the end-effector of an industrial robot KUKA KR5 Arc as the measurement sensor and the kinematic parameters identified using the proposed approach were compared with those obtained using other measurement devices, namely, a total station and a laser tracker.
Abstract: We propose a generic formulation to identify the kinematic parameters of an industrial robot using a geometric approach when no prior information about the robot’s kinematics is available. The joint axes were estimated using the singular value decomposition applied to the pose data of the robot’s end-effector. These data were obtained by actuating one joint of the robot at a time. The approach is first illustrated using the CAD model of the robot. Next, a simulation study was performed to decide on the number of data points and angular actuation required by a revolute joint to estimate the kinematic parameters. This was done considering the fact that there exist noise in the measurements from the sensors. In this paper, we used a monocular camera mounted on the end-effector of an industrial robot KUKA KR5 Arc as the measurement sensor. We used ArUco Marker maps instead of a single calibration grid to enhance the range of actuation for each joint that was otherwise restricted due to the Field of View of the camera. The robot’s kinematic parameters were then identified using the proposed approach. The identified parameters using the monocular camera were compared with those obtained using other measurement devices, namely, a total station and a laser tracker.
TL;DR: In this article, a theoretical contact model of revolute joints with planar rough contacting surface is established, and the influence of roughness is introduced in this model, where the effects of impact velocity, restitution coefficient and roughness on dynamic characteristics are analyzed.
TL;DR: A new algorithm based on the parameters of degree, weight, degree-sequence and weight-sequence is developed to detect isomorphism and is helpful to design mechanisms with P-pairs, and can be extended to mechanisms with other types of kinematic pairs.
TL;DR: In this article, a change-point Wiener and Inverse Gaussian process is used to capture the two-phase degradation of the revolute joints in a lock mechanism, and the degradation parameter estimation based on Bayesian method is addressed.
01 Jan 2019
TL;DR: A novel method to determine 4-RUU parallel manipulator's operation modes as functions of the orientation of its base revolute joint axes, which leads to a dual reconfigurable 4-rRUU mechanism.
Abstract: A lower-mobility parallel manipulator with multiple operation modes can be considered as inherently reconfigurable. 4-RUU parallel manipulator is one such manipulator with three different operation modes. Allowing the first revolute joint axis to have any horizontal orientation leads to a dual reconfigurable 4-rRUU mechanism. This paper presents a novel method to determine its operation modes as functions of the orientation of its base revolute joint axes. Moreover, it's transla-tional workspace is plotted for three mutually perpendicular orientations of its base revolute joint axes. With a goal to realize a working prototype, pareto optimization is used to determine its design parameters such that it has a larger singularity-and interference-free workspace while having a smaller size.