Showing papers on "Revolute joint published in 2015"
TL;DR: This work offers the solution at the control feed-back level of the accurate trajectory tracking subject to finite-time convergence of a class of absolutely continuous robust controllers effective in counteracting both uncertain dynamics and unbounded disturbances.
163 citations
TL;DR: Finite-time optimal and suboptimal controls for time-varying systems with state and control nonlinearities for robotic manipulator are investigated and general formulation and stability analysis is provided.
Abstract: This article investigates finite-time optimal and suboptimal controls for time-varying systems with state and control nonlinearities. The state-dependent Riccati equation (SDRE) controller was the main framework. A finite-time constraint imposed on the equation changes it to a differential equation, known as the state-dependent differential Riccati equation (SDDRE) and this equation was applied to the problem reported in this study that provides general formulation and stability analysis. The following four solution methods were developed for solving the SDDRE; backward integration, state transition matrix (STM) and the Lyapunov based method. In the Lyapunov approach, both positive and negative definite solutions to related SDRE were used to provide suboptimal gain for the SDDRE. Finite-time suboptimal control is applied for robotic manipulator, as finite-time constraint strongly decreases state error and operation time. General state-dependent coefficient (SDC) parameterizations for rigid and flexible joint arms (prismatic or revolute joints) are introduced. By including nonlinear control inputs in the formulation, the actuator׳s limits can be inserted directly to the state-space equation of a manipulator. A finite-time SDRE was implemented on a 6R manipulator both in theory and experimentally. And a reduced 3R arm was modeled and tested as a flexible joint robot (FJR). Evaluations of load carrying capacity and operation time were investigated to assess the capability of this approach, both of which showed significant improvement.
105 citations
TL;DR: In this article, an optimization method is proposed to alleviate the undesirable effects of joint clearance in a sliding-crank mechanism, where the main consideration is to optimize the mass distribution of the links of a mechanism to reduce or eliminate the impact forces in the clearance joint.
91 citations
TL;DR: In this paper, the authors derived differential equations of motion for a slider-crank mechanism with clearance in the revolute joint between the slider and connecting rod, and the normal contact force developed in the journal-bearing system was calculated using the continuous contact force model proposed by Lankarani and Nikravesh.
74 citations
TL;DR: In this paper, a hybrid contact force model based on the Lankarani-Nikravesh model and the elastic foundation model is proposed for small clearance and low restitution coefficient situations for a revolute clearance joint in the slider-crank mechanism.
68 citations
TL;DR: In this paper, a family of deployable structures based on the origami flasher, which are rigidly foldable with revolute joints at the creases and planar rigid faces, is presented.
Abstract: We present the design for a family of deployable structures based on the origami flasher, which are rigidly foldable, i.e., foldable with revolute joints at the creases and planar rigid faces. By appropriate choice of sector angles and introduction of a cut, a single degree-of-freedom (DOF) mechanism is obtained. These structures may be used to realize highly compact deployable mechanisms.
66 citations
TL;DR: In this article, a model for 3D revolute joints with radial and axial clearances is proposed, in which a group of contact force models are employed to reflect different contact-impact phenomena.
Abstract: A mechanical system with clearance joints is well known as a nonlinear dynamic system that may exhibit chaotic responses under certain conditions. In the previous literature, the model for clearance joint is extensively investigated since it plays a significant role in prediction of kinematic and dynamic behavior of the system. A large volume of the literature only focuses on radial clearances, whereas, due to manufacturing and assembling errors, axial clearances also exist in joints, which have been scarcely considered. In this study, a comprehensive model for 3D revolute joints with radial and axial clearances is proposed. An experiment of the 3D revolute joint with clearances is firstly conducted to reveal the characteristics of the relative motion between the journal and bearing. According to the kinematic features, a model for 3D revolute joints with radial and axial clearances is proposed. This model presents a comprehensive description of the contact modes in which a group of contact force models are employed to reflect different contact–impact phenomena. Thus, the axial movement of the journal relative to the bearing and misalignment between the two elements could be characterized by this model. Moreover, a numerical simulation of the experiment is performed to validate the model presented in this study. Finally, a four-bar mechanism is taken as an example to illustrate its application and investigate the nonlinear dynamics of this system.
63 citations
TL;DR: The resultant bi-criteria minimization scheme, formulated as the pseudoinverse-type solution, not only avoids the high joint-velocity and joint-acceleration phenomena but also causes the joint velocity to be near zero at the end of motion.
Abstract: In this paper, a pseudoinverse-type bi-criteria minimization scheme is proposed and investigated for the redundancy resolution of robot manipulators at the joint-acceleration level. Such a bi-criteria minimization scheme combines the weighted minimum acceleration norm solution and the minimum velocity norm solution via a weighting factor. The resultant bi-criteria minimization scheme, formulated as the pseudoinverse-type solution, not only avoids the high joint-velocity and joint-acceleration phenomena but also causes the joint velocity to be near zero at the end of motion. Computer simulation results based on a 4-Degree-of-Freedom planar robot manipulator comprising revolute joints further verify the efficacy and flexibility of the proposed bi-criteria minimization scheme on robotic redundancy resolution.
60 citations
TL;DR: In this paper, a flexure hinge for MEMS applications is presented, which combines a curved beam, as a flexible element, and a pair of conjugate surfaces, whose contact depends on load conditions.
Abstract: This paper presents a new concept flexure hinge for MEMS applications and reveals how to design, construct, and experimentally test. This hinge combines a curved beam, as a flexible element, and a pair of conjugate surfaces, whose contact depends on load conditions. The geometry is conceived in such a way that minimum stress conditions are maintained within the flexible beam. A comparison of the new design with the other kind of revolute and flexible joints is presented. Then, the static behavior of the hinge is analyzed by means of a theoretical approach, based on continuum mechanics, and the results are compared to those obtained by means of finite element analysis (FEA) simulation. A silicon hinge prototype is also presented and the construction process, based on single step lithography and reactive ion etching (RIE) technology, is discussed. Finally, a crucial in–SEM experiment is performed and the experimental results are interpreted through the theoretical models.
56 citations
TL;DR: In this article, the authors used a fixed coordinate system to evaluate all quantities required by the contact force model and used the continuous contact force method to calculate the contact forces at any time during the dynamic simulation.
52 citations
TL;DR: In this paper, the equations of motion of N-rigid link manipulators with revolute-prismatic (R-P) joints mounted on a mobile platform are derived using recursive Gibbs-Appell (G-A) formulation.
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TL;DR: In this paper, the authors describe a method by which a robot can acquire an object model by capturing depth imagery of the object as a human moves it through its range of motion.
Abstract: Many functional elements of human homes and workplaces consist of rigid components which are connected through one or more sliding or rotating linkages. Examples include doors and drawers of cabinets and appliances; laptops; and swivel office chairs. A robotic mobile manipulator would benefit from the ability to acquire kinematic models of such objects from observation. This paper describes a method by which a robot can acquire an object model by capturing depth imagery of the object as a human moves it through its range of motion. We envision that in future, a machine newly introduced to an environment could be shown by its human user the articulated objects particular to that environment, inferring from these "visual demonstrations" enough information to actuate each object independently of the user.
Our method employs sparse (markerless) feature tracking, motion segmentation, component pose estimation, and articulation learning; it does not require prior object models. Using the method, a robot can observe an object being exercised, infer a kinematic model incorporating rigid, prismatic and revolute joints, then use the model to predict the object's motion from a novel vantage point. We evaluate the method's performance, and compare it to that of a previously published technique, for a variety of household objects.
01 Jan 2015
TL;DR: This work considers the task of one-shot pose estimation of articulated object instances from an RGB-D image of objects with the topology of a kinematic chain of any length, i.e. objects are composed of a chain of parts interconnected by joints.
Abstract: Accurate pose estimation of object instances is a key aspect in many applications, including augmented reality or robotics. For example, a task of a domestic robot could be to fetch an item from an open drawer. The poses of both, the drawer and the item have to be known by the robot in order to fulfil the task. 6D pose estimation of rigid objects has been addressed with great success in recent years. In large part, this has been due to the advent of consumer-level RGB-D cameras, which provide rich, robust input data. However, the practical use of state-of-the-art pose estimation approaches is limited by the assumption that objects are rigid. In cluttered, domestic environments this assumption does often not hold. Examples are doors, many types of furniture, certain electronic devices and toys. A robot might encounter these items in any state of articulation. This work considers the task of one-shot pose estimation of articulated object instances from an RGB-D image. In particular, we address objects with the topology of a kinematic chain of any length, i.e. objects are composed of a chain of parts interconnected by joints. We restrict joints to either revolute joints with 1 DOF (degrees of freedom) rotational movement or prismatic joints with 1 DOF translational movement. This topology covers a wide range of common objects (see our dataset for examples). However, our approach can easily be expanded to any topology, and to joints with higher degrees of freedom.
TL;DR: In this paper, an optimization method is proposed to alleviate the undesirable effects of joint clearances, where the main consideration is to optimize the mass distribution of links of a mechanism to reduce or eliminate the impact forces in the clearance joints.
Abstract: In practice, clearances in the joints are inevitable due to tolerances, and defects arising from design and manufacturing. It is noteworthy that in the presence of clearance at a joint, a mechanism gains some additional, uncontrollable degrees of freedom which are the source of error. Moreover, joints undergo wear and backlashes and so cannot be used in precision mechanisms. In this paper, an optimization method is proposed to alleviate the undesirable effects of joint clearances. The main consideration here is to optimize the mass distribution of links of a mechanism to reduce or eliminate the impact forces in the clearance joints. An algorithm based on PSO solves this highly nonlinear optimization problem for a slider–crank mechanism with revolute clearance joints. Finally, an example is included to demonstrate the efficiency of the algorithm. The results clearly reveal that the linear and angular accelerations of the links and the contact forces in the optimal design are very smooth and bounded.
TL;DR: In this paper, a sliding velocity observer based adaptive control of flexible-joint free-floating space manipulators with parametric uncertainties and modeling errors is addressed, where a composite controller which consisted of a slow control component and a flexible joint fast control component was proposed.
17 Dec 2015
TL;DR: This work proposes a sliding mode controller for in-hand manipulation that repositions a tool in the robot's hand by using gravity and controlling the slippage of the tool.
Abstract: In this work we propose a sliding mode controller for in-hand manipulation that repositions a tool in the robot's hand by using gravity and controlling the slippage of the tool. In our approach, the robot holds the tool with a pinch grasp and we model the system as a link attached to the gripper via a passive revolute joint with friction, i.e., the grasp only affords rotational motions of the tool around a given axis of rotation. The robot controls the slippage by varying the opening between the fingers in order to allow the tool to move to the desired angular position following a reference trajectory. We show experimentally how the proposed controller achieves convergence to the desired tool orientation under variations of the tool's inertial parameters.
29 Jun 2015
TL;DR: In this article, the authors provide a systematic comparison of various beam models and compare their predictions for four benchmark problems, such as the Princeton beam experiment, the four-bar mechanism, the three-bar model, and the four bar model, focusing on a flexible mechanism involving beams and revolute joints.
Abstract: As the need to model flexibility arose in multibody dynamics, the floating frame of reference formulation was developed, but this approach can yield inaccurate results when elastic displacements becomes large. While the use of three-dimensional finite element formulations overcomes this problem, the associated computational cost is overwhelming. Consequently, beam models, which are one-dimensional approximations of three-dimensional elasticity, have become the workhorse of many flexible multibody dynamics codes. Numerous beam formulations have been proposed, such as the geometrically exact beam formulation or the absolute nodal coordinate formulation, to name just two. New solution strategies have been investigated as well, including the intrinsic beam formulation or the DAE approach. This paper provides a systematic comparison of these various approaches, which will be assessed by comparing their predictions for four benchmark problems. The first problem is the Princeton beam experiment, a study of the static large displacement and rotation behavior of a simple cantilevered beam under a gravity tip load. The second problem, the four-bar mechanism, focuses on a flexible mechanism involving beams and revolute joints. The third problem investigates the behavior of a beam bent in its plane of greatest flexural rigidity, resulting in lateral buckling when a critical value of the transverse load is reached. The last problem investigates the dynamic stability of a rotating shaft. The predictions of eight independent codes are compared for these four benchmark problems and are found to be in close agreement with each other and with experimental measurements, when available.
TL;DR: In this article, the effects of clearance on the dynamic responses of a dual-axis positioning mechanism of a satellite antenna were investigated using a computational methodology, and the results showed that clearance has significant effects on dynamic response of the mechanism.
Abstract: The effects of clearance on dynamic responses of dual-axis positioning mechanism of a satellite antenna are investigated using a computational methodology. Considering clearances in joints, the clearance is defined and the mathematical model of revolute joint with clearance is presented. The normal contact force model and tangential friction model in clearance joint are established using nonlinear continuous contact force model and Coulomb friction model, respectively. Then numerical simulation is used to investigate the dynamic responses of dual-axis positioning mechanism with joint clearance. The results show that clearance has significant effects on dynamic responses of mechanism, and the investigation of the work can predict the dynamic responses of dual-axis positioning mechanism with clearance preferably, which is the basis of mechanism design, precision analysis and control system design.
TL;DR: In this paper, a hybrid robotic wrist with four degrees of freedom (DOF) was developed for assisting physicians to perform minimally invasive surgery (MIS), where the main body of the wrist is a 2DOF parallel mechanism with a remote center of motion (RCM) located outside the mechanism.
Abstract: To deliver more value to the healthcare industry, a specialized surgical robot is needed in the minimally invasive surgery (MIS) field. To fill this need, a compact hybrid robotic wrist with four degrees of freedom (DOFs) is developed for assisting physicians to perform MIS. The main body of the wrist is a 2DOF parallel mechanism with a remote center-of-motion (RCM), which is located outside the mechanism. From the mechanical point of view, it is different from existing 2DOF spherical mechanisms, since there is no physical constraint on the RCM. Other DOFs of the wrist are realized by a revolute joint and a prismatic joint, which are serially mounted on the movable platform of the parallel mechanism. The function of these DOFs is to realize the roll motion and the in-out translation of the surgical tool. Special attention is paid to the parallel RCM mechanism. The detailed design is provided and the kinematic equations are obtained in the paper. Further, the Jacobian matrix is derived based on the kinematic equations. Finally, the paper examines the singularity configurations and implements the condition number analysis to identify the kinematic performance of the mechanism.
TL;DR: This work uses the recently introduced factorization theory of motion polynomials over the dual quaternions for the synthesis of closed kinematic loops with six revolute joints that visit four prescribed poses.
Abstract: We use the recently introduced factorization theory of motion polynomials over the dual quaternions for the synthesis of closed kinematic loops with six revolute joints that visit four prescribed poses. Our approach admits either no or a one-parametric family of solutions. We suggest strategies for picking good solutions from this family.
TL;DR: In this paper, the authors proposed a contact analysis method without the need of releasing the kinematic constraints of joints for the contact analysis of revolute joints, in which the ball that is in contact with its raceways and the contact forces acting on such a ball as well as the instants of likely impacts can be known.
Abstract: In traditional methods of contact analysis, kinematic constraints of joints in a multibody system have to be released and functions of the joints are replaced by contact forces. This methodology is not optimal when the clearance in a joint is extremely small, because in this case unnecessarily releasing joint constraints could bring a negative effect on the numerical stability and efficiency. In practice, a majority of revolute joints are composed of a pair of deep groove ball bearings with tiny clearances. Their contact situations are complex and require a lot of description parameters. In the traditional methods, these parameters are extracted from relative motion between bodies, whereas in this paper they are treated as unknown variables. Among a variety of contacts between a ball and its raceways or its pockets, the most significant one is the stable contact situation where a ball can stably carry loads. The stable contacts impose some restrictions on these parameters, so that five parameters are sufficient for representing contact locations and contact forces of all the balls in the stable contact state. The five variables can be determined by five equations provided by the relationship between contact forces and joint reaction forces. On the basis of these ideas, a methodology without the need of releasing the kinematic constraints of joints is proposed for the contact analysis of such revolute joints. The proposed method, in which the ball that is in contact with its raceways and the contact forces acting on such a ball as well as the instants of likely impacts can be known, is illustrated by the two numerical examples in this paper.
TL;DR: An improved nonlinear elastic-damping contact force model, based on accounting for the axial dimension of bearing and journal, energy dissipation during contact process and the nonlinear power exponent from material, is established to evaluate the contact force of revolute joint with clearance as mentioned in this paper.
Abstract: An improved nonlinear elastic-damping contact force model, based on accounting for the axial dimension of bearing and journal, energy dissipation during contact process and the nonlinear power exponent from material, is established to evaluate the contact force of revolute joint with clearance. The friction effect was also determined using the modified Coulomb friction model. Numerical simulation was carried out to discuss the influence of clearance size on the kinematic and dynamic characteristics of the planar slider-crank mechanism, which has a clearance joint between the connecting rod and slider. The numerical results point out that the existence of joint clearance causes high peaks on the kinematic and dynamic system’s characteristics. Even if the clearance size is small, it also causes obvious high frequency shaking of the slider acceleration, joint reaction force and the crank moment.
TL;DR: This paper presents a method for path following control design applicable to framed curves generated by splines in the workspace of kinematically redundant mechanical systems, which includes self-intersecting curves.
Abstract: Path following controllers make the output of a control system approach and traverse a prespecified path with no a priori time-parametrization. In this paper, we present a method for path following control design applicable to framed curves generated by splines in the workspace of kinematically redundant mechanical systems. The class of admissible paths includes self-intersecting curves. Kinematic redundancies are resolved by designing controllers that solve a suitably defined constrained quadratic optimization problem. By employing partial feedback linearization, the proposed path following controllers have a clear physical meaning. The approach is experimentally verified on a four-degree-of-freedom (four-DOF) manipulator with a combination of revolute and linear actuated links and significant model uncertainty.
03 Nov 2015
TL;DR: The use of integration made it possible to determine the safe operating space of a stationary hexapod taking into consideration the security of a person in the driving simulator designed for the disabled.
Abstract: The paper presents the problems related to the integration of a CAD/CAE system with the LabVIEW software. The purpose of the integration is to determine the workspace of a hexapod model basing on a mathematical model describing it motion. In the first stage of the work concerning the integration task the 3D model to simulate movements of a hexapod was elaborated. This phase of the work was done in the "Motion Simulation" module of the CAD/CAE/CAM Siemens NX system. The first step was to define the components of the 3D model in the form of "links". Individual links were defined according to the nature of the hexapod elements action. In the model prepared for movement simulation were created links corresponding to such elements as: electric actuator, top plate, bottom plate, ball-and-socket joint, toggle joint Phillips. Then were defined the constraints of the "joint" type (e.g.: revolute joint, slider joint, spherical joint) between the created component of the "link" type, so that the computer simulation corresponds to the operation of a real hexapod. The next stage of work included implementing the mathematical model describing the functioning of a hexapod in the LabVIEW software. At this stage, particular attention was paid to determining procedures for integrating the virtual 3D hexapod model with the results of calculations performed in the LabVIEW. The results relate to specific values of the jump of electric actuators depending on the position of the car on the hexapod. The use of integration made it possible to determine the safe operating space of a stationary hexapod taking into consideration the security of a person in the driving simulator designed for the disabled.
TL;DR: In this paper, a 3-DOF translational parallel mechanism (TPM) three-CRU (C, R, and U represent the cylindrical, revolute, and universal joints, respectively) structure is proposed.
Abstract: . In this paper, a modified 3-DOF (degrees of freedom) translational parallel mechanism (TPM) three-CRU (C, R, and U represent the cylindrical, revolute, and universal joints, respectively) structure is proposed. The architecture of the TPM is comprised of a moving platform attached to a base through three CRU jointed serial linkages. The prismatic motions of the cylindrical joints are considered to be actively actuated. Kinematics and performance of the TPM are studied systematically. Firstly, the structural characteristics of the mechanism are described, and then some comparisons are made with the existing 3-CRU parallel mechanisms. Although these two 3-CRU parallel mechanisms are both composed of the same CRU limbs, the types of freedoms are completely different due to the different arrangements of limbs. The DOFs of this TPM are analyzed by means of screw theory. Secondly, both the inverse and forward displacements are derived in closed form, and then these two problems are calculated directly in explicit form. Thereafter, the Jacobian matrix of the mechanism is derived, the performances of the mechanism are evaluated based on the conditioning index, and the performance of a 3-CRU TPM changing with the actuator layout angle is investigated. Thirdly, the workspace of the mechanism is obtained based on the forward position analysis, and the reachable workspace volume is derived when the actuator layout angle is changed. Finally, some conclusions are given and the potential applications of the mechanism are pointed out.
TL;DR: In this article, a three-dimensional revolute joint model is introduced, the calculation of joint friction is discussed in detail, and the relationship between ideal constraint force and Lagrange multipliers is derived.
TL;DR: In this article, the authors present a method for path following control design applicable to framed curves generated by splines in the workspace of kinematically redundant mechanical systems, where the class of admissible paths includes self-intersecting curves.
Abstract: Path following controllers make the output of a control system approach and traverse a pre-specified path with no apriori time parametrization. In this paper we present a method for path following control design applicable to framed curves generated by splines in the workspace of kinematically redundant mechanical systems. The class of admissible paths includes self-intersecting curves. Kinematic redundancies are resolved by designing controllers that solve a suitably defined constrained quadratic optimization problem. By employing partial feedback linearization, the proposed path following controllers have a clear physical meaning. The approach is experimentally verified on a 4-degree-of-freedom (4-DOF) manipulator with a combination of revolute and linear actuated links and significant model uncertainty.
TL;DR: In this article, an optimization methodology is presented for the design of serial-chain planar robots for minimizing torque at joints, when the end-effector is allowed to move on a circular path.
Abstract: An optimization methodology is presented for design of serial-chain planar robots for minimizing torque at joints, when its endeffector is supposed to move on a prescribed path In particular, the end-effector of the robot is allowed to move on a circular path For the respective joint trajectories, the weighted sum of root mean square (RMS) of the actuating torques is minimized by the mass redistribution of the links To achieve the goal, the DeNOC (Decoupled natural orthogonal complement) based dynamics was formulated by representing the rigid links as a set of rigidly connected point-masses known as equimomental system The methodology is illustrated using a planar two-degree-of-freedom (DOF) robot with two revolute joints
TL;DR: In this paper, an analytical model was presented to describe the dynamic characteristics of a planar rotation beam with clearance joint, where the spherical contact model was introduced to calculate the collision forces for the planar revolute joint.
TL;DR: In this article, a numerical approach is proposed for the modeling and prediction of wear at a revolute clearance joint in a flexible multibody mechanical system by integrating the procedures of wear prediction with multi-body dynamics.
Abstract: This article numerically investigates the effects of flexibility at different locations on a mechanism on the wear at a clearance joint as well as the dynamic performance of a multibody mechanical system. A numerical approach is proposed for the modeling and prediction of wear at a revolute clearance joint in a flexible multibody mechanical system by integrating the procedures of wear prediction with multibody dynamics. Using this approach, a planar slider–crank mechanism including a clearance joint is used as an illustrative case. The effects of the flexibilities of a connecting rod and crankshaft on the clearance joint wear are compared. From the main results obtained, it can be concluded that the differently located flexibilities of the mechanism have different effects on the clearance joint wear and dynamic performance of the system. The flexibility of a connecting rod has a positive influence on reducing the impact and wear at the revolute clearance joint. Moreover, the higher the value of the connec...