Showing papers on "Revolute joint published in 2020"
TL;DR: A generic error modeling method of serial robots and extend to parallel robots by finite and instantaneous screw (FIS) theory is presented and the results show that the calibration approach improves the robot accuracy in a robust and efficient manner.
Abstract: In current robot calibration approaches, the error propagation and identification of serial and parallel robots fail to be solved intuitively and generically, resulting in an inefficient calibration implementation and a low accuracy improvement. In this article, we present a generic error modeling method of serial robots and extend to parallel robots by finite and instantaneous screw (FIS) theory. The differential map and the explicit description of FIS on the robot motions enable a concise error modeling of the serial robot. The identifiability of errors in serial robot is discussed. The maximum independent errors are proved to be 4 r + 2 p + 6, where r and p are the numbers of revolute and prismatic joints, respectively. Based on the error mapping of serial limbs, reciprocal twist and wrench are introduced to consider the interaction among limbs and reveal the error propagation of the parallel robot. Then, the identification algorithms with high robustness and efficiency are investigated for the serial and parallel robots. Specifically, the conventional ill-conditioning problems of parallel robots are addressed. Finally, the proposed kinematic calibration framework for both types of robots are compared with the existing methods, and verified by simulations and experiments. The results show that our calibration approach improves the robot accuracy in a robust and efficient manner.
38 citations
TL;DR: A dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices is proposed, where U denotes a universal joint, R denotes a revolute joint and P denotes a prismatic pair.
Abstract: Friction stir welding (FSW) has been widely applied in many fields as an alternative to traditional fusion welding. Although serial robots can provide the orientation capability required to weld along curved surfaces, they cannot adequately support the huge axial downward forces that FSW generates. Available parallel mechanism architectures, particularly redundantly actuated architectures for FSW, are still very limited. In this paper, a redundantly actuated 2UPR-2RPU parallel robot for FSW is proposed, where U denotes a universal joint, R denotes a revolute joint and P denotes a prismatic pair. First, its semi-symmetric structure is described. Next, inverse kinematics analysis involving an analytical representation of rotational axes is implemented. Velocity analysis is also conducted, which leads to the formation of a Jacobian matrix. Sensitivity performance is evaluated utilizing level set and convex optimization methods, where the local sensitivity indices are unit consistent, coordinate free, and of definite physical significance. Furthermore, global and hierarchical sensitivity indices are proposed for the design process. Finally, dimension synthesis is conducted based on the sensitivity indices and the optimal link parameters of the parallel robot are obtained. In summary, this paper proposes a dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices.
37 citations
TL;DR: The result shows that the proposed ANN model can be used instead of the complex and time-consuming GA in the process of finding the optimal parameters of the gimbal joint.
Abstract: Industrial robots have a great impact on increasing the productivity and reducing the time of the manufacturing process. To serve this purpose, in the past decade, many researchers have concentrated to optimize robotic models utilizing artificial intelligence (AI) techniques. Gimbal joints because of their adjustable mechanical advantages have been investigated as a replacement for traditional revolute joints, especially when they are supposed to have tiny motions. In this research, the genetic algorithm (GA), a well-known evolutionary technique, has been adopted to find optimal parameters of the gimbal joints. Since adopting the GA is a time-consuming process, an artificial neural network (ANN) architecture has been proposed to model the behavior of the GA. The result shows that the proposed ANN model can be used instead of the complex and time-consuming GA in the process of finding the optimal parameters of the gimbal joint.
36 citations
TL;DR: In this article, a nonsmooth strategy for solving planar rigid multibody systems with multiple revolute clearance joints was proposed, based on the principle of Hamilton's variation, and the discrete form of the governing equations satisfies symplecticity.
35 citations
TL;DR: This paper presents a reconfigurable axis (rA) joint inspired and evolved from Rubik's Cubes, which have a unique feature of geometric and physical constraint of axes of joint.
Abstract: The current research of reconfigurable parallel mechanism mainly focuses on the construction of reconfigurable joints. Compared with the method of changing the mobility by physical locking joints, the geometric constraint has good controllability, and the constructed parallel mechanism has more configurations and wider application range. This paper presents a reconfigurable axis (rA) joint inspired and evolved from Rubik's Cubes, which have a unique feature of geometric and physical constraint of axes of joint. The effectiveness of the rA joint in the construction of the limb is analyzed, resulting in a change in mobility and topology of the parallel mechanism. The rA joint makes the angle among the three axes inside the groove changed arbitrarily. This change in mobility is completed by the case illustrated by a 3(rA)P(rA) reconfigurable parallel mechanism having variable mobility from 1 to 6 and having various special configurations including pure translations, pure rotations. The underlying principle of the metamorphosis of this rA joint is shown by investigating the dependence of the corresponding screw system comprising of line vectors, leading to evolution of the rA joint from two types of spherical joints to three types of variable Hooke joints and one revolute joint. The reconfigurable parallel mechanism alters its topology by rotating or locking the axis of rA joint to turn all limbs into different phases. The prototype of reconfigurable parallel mechanism is manufactured and all configurations are enumerated to verify the validity of the theoretical method by physical experiments.
26 citations
TL;DR: In this article, a planar Cross-Axis Flexural Pivot (CAFP) comprising an additional contact pair is investigated for applications requiring a revolute joint that behaves differently when deflecting clockwise/anti-clockwise.
26 citations
TL;DR: A recursive algorithm, which has been developed based on 3 × 3 rotation matrices to reduce the computational load, symbolically derives the motion equations of a multibody system that collides with surrounding surfaces at several points.
25 citations
TL;DR: A novel implementation of a specific multibody model to include the effect of tip relief micro-modification on spur gears is presented, offering a trade-off between the accuracy of an equivalent finite element method model and the advantage of reducing the degrees of freedom allowing for fast dynamic simulations.
20 citations
TL;DR: In this article, a hybrid model is proposed for wear prediction of a single revolute joint that may experience different lubrication conditions, such as full-film, boundary and dry contact.
19 citations
TL;DR: A Jacobian based stiffness analysis is done to understand the variations in stiffness for different poses of the mobile platform and further, it is used to decide trajectories for the end effector within the singularity free region.
Abstract: Parallel Kinematic Machines (PKMs) are being widely used for precise applications to achieve complex motions and variable poses for the end effector tool. PKMs are found in medical, assembly and manufacturing industries where accuracy is necessary. It is often desired to have a compact and simple architecture for the robotic mechanism. In this paper, the kinematic and dynamic analysis of a novel 3-PRUS (P: prismatic joint, R: revolute joint, U: universal joint, S: spherical joint) parallel manipulator with a mobile platform having 6 Degree of Freedom (DoF) is explained. The kinematic equations for the proposed spatial parallel mechanism are formulated using the Modified Denavit-Hartenberg (DH) technique considering both active and passive joints. The kinematic equations are used to derive the Jacobian matrix of the mechanism to identify the singular points within the workspace. A Jacobian based stiffness analysis is done to understand the variations in stiffness for different poses of the mobile platform and further, it is used to decide trajectories for the end effector within the singularity free region. The analytical model of the robot dynamics is presented using the Euler-Lagrangian approach with Lagrangian multipliers to include the system constraints. The gravity and inertial forces of all links are considered in the mathematical model. The analytical results of the dynamic model are compared with ADAMS simulation results for a pre-defined trajectory of the end effector.
18 citations
TL;DR: A unique experimental snake robot with one revolute and one linear joint on each module, with the ability to perform planar motion, is developed with implications for snake robot locomotion in narrow spaces such as a pipe or channel.
Abstract: This paper analyzed the locomotion of a snake robot in narrow spaces such as a pipe or channel. We developed a unique experimental snake robot with one revolute and one linear joint on each module, with the ability to perform planar motion. The designed locomotion pattern was simulated in MATLAB R2015b and subsequently verified by the experimental snake robot. The locomotion of the developed snake robot was also experimentally analyzed on dry and viscous surfaces. The paper further describes the investigation of locomotion stability by three symmetrical curves used to anchor static modules between the walls of the pipe. The stability was experimentally analyzed by digital image correlation using a Q-450 Dantec Dynamics high-speed correlation system. The paper presents some input symmetrical elements of locomotion and describes their influence on the results of locomotion. The results of simulations and experiments show possibilities of snake robot locomotion in a pipe.
TL;DR: In this article, the effects of revolute mass and axial stiffness on the dynamic characteristics of a 5-DOF hybrid machine tool were investigated, and the geometric distortion of bearings was considered in the study.
TL;DR: A novel deployable tetrahedron-based mobile robot constructed by Sarrus linkages with eight degrees of freedom (DOFs) is proposed, and two folding modes of folding as an umbrella shape and deploying in radially reciprocating motion are developed.
28 Jan 2020
TL;DR: It is demonstrated that the designed 4-bar based exoskeleton can track the human digit motion accurately and resolve its kinematic redundancy during a fine object translation motion by instantaneously optimizing manipulability measure.
Abstract: This article deals with the optimal design and redundancy resolution of a seven DOF robotic two-fingered hand exoskeleton intended for rehabilitation purposes. The exoskeleton is designed to track the human digit motion accurately. As the human digit joint cannot be modeled by single revolute joint due to instantaneously varying center of rotation, a 4-bar mechanism is employed to model each phalanx of a finger. Optimal 4-bar linkages are designed by minimizing the error between the Cartesian trajectories of the human phalanx and those of the coupler points in respective 4-bar mechanisms. It is demonstrated that the designed 4-bar based exoskeleton can track the human digit motion accurately. Performance analysis of the developed device has been carried out by resolving its kinematic redundancy during a fine object translation motion by instantaneously optimizing manipulability measure.
TL;DR: A novel design method for three translational degrees of freedom parallel mechanisms containing prismatic joints and parallelogram units ((R-R)2 linkage) is proposed by mapping relationship with augmented matrices of upper triangular matrix.
TL;DR: Simulation results demonstrate the validity of the dynamic methodology containing the modified Pinkus–Sternlicht model for the 3-PRR parallel robot with multipleubricated joints and can illustrate the better periodicity of such parallel robots considering lubricated joints.
Abstract: This paper presents a methodology to study the dynamic response of a parallel robot with multiple lubricated joints. Based on Gumbel’s boundary conditions, the hydrodynamic force of the journal bearing is calculated with the Pinkus–Sternlicht model. Considering the dynamic loads on the multiple lubricated joints, the Pinkus–Sternlicht model is modified to ensure numerical stability of the solution of the system’s equations. A comparative analysis of four joint force models is presented to show the advantages of the modified model for a 3-PRR (P and R represent prismatic and revolute pairs respectively and the underline of the P represents the actuated joint) parallel robot. The improvement in the numerical stability of the modified Pinkus–Sternlicht model is proven. Subsequently, the dynamic behavior of the 3-PRR parallel robot with multiple lubricated joints is analyzed comprehensively, compared with the 3-PRR parallel robot with multiple dry clearance joints. Simulation results demonstrate the validity of the dynamic methodology containing the modified Pinkus–Sternlicht model for the 3-PRR parallel robot with multiple lubricated joints. This dynamic methodology can illustrate the better periodicity of such parallel robots considering lubricated joints.
TL;DR: The systemic dynamic modeling and analysis of a 2PRU-UPR parallel robot with two rotations and one translation based on screw theory provides a basis for the efficient and precise control of the 2PRu-U PR parallel robot in actual machining manipulations.
Abstract: This paper proposes the systemic dynamic modeling and analysis of a 2PRU-UPR parallel robot with two rotations and one translation based on screw theory, where P, R and U denote prismatic, revolute and universal joints, respectively. Compared with existing parallel robots having two rotations and one translation, the two actuated prismatic joints of the 2PRU-UPR parallel robot are mounted on a fixed base to reduce the movable mass and improve the dynamic response. First, the inverse kinematics are presented. Next, adopting the screw-based method, the velocity and acceleration of joints and limbs of the 2PRU-UPR parallel robot are analyzed in detail. The actuated forces of the three actuators are then obtained according to the principle of virtual work. Additionally, a numerical simulation is conducted using ADAMS software to investigate the dynamic model of the 2PRU-UPR manipulator and to verify the correctness of the theoretical results. Finally, distributions of the dynamic manipulability ellipsoid index are used to evaluate the dynamic translational and rotational performances of the 2PRU-UPR parallel robot. A prototype based on the dynamic analysis has been fabricated. The dynamic modeling and evaluation provide a basis for the efficient and precise control of the 2PRU-UPR parallel robot in actual machining manipulations. The 2PRU-UPR parallel robot has great potential in machining workpieces with curved surfaces.
TL;DR: A novel smooth transition mechanics of robot motion, from stationary position to serpentine or rectilinear motion as well as transition between these two gaits, is suggested in the paper.
Abstract: This paper contributes to the fabrication of a snake-like robot in which the motion can be achieved through active wheels. The robot is constructed in such a way that its size can be increased and decreased, as well as it can undulate into a sine wave-like shape. The snake robot with wheels consists of chain of links attached to each other with the help of the passive prismatic and revolute joints. A neural oscillator-based central pattern generator (CPG) algorithm is applied to the robot so that rhythmic serpentine as well as rectilinear motions can be generated in it. In addition, a novel smooth transition mechanics of robot motion, from stationary position to serpentine or rectilinear motion as well as transition between these two gaits, is also suggested in the paper. The working of the formulated CPG motion algorithm is realized through experimental setup equipped with a motion capture system as well as through simulations.
08 Aug 2020
TL;DR: A 3D geometric model of the linear flexible object that is subject to gravity and a physical model with multiple links connected by revolute joints and identified model parameters enable task automation in manipulating linear flexible objects both in simulation and real world.
Abstract: Manipulation of deformable objects is a desired skill in making robots ubiquitous in manufacturing, service, healthcare, and security. Common deformable objects (e.g., wires, clothes, bed sheets, etc.) are significantly more difficult to model than rigid objects. In this research, we contribute to the model-based manipulation of linear flexible objects such as cables. We propose a 3D geometric model of the linear flexible object that is subject to gravity and a physical model with multiple links connected by revolute joints and identified model parameters. These models enable task automation in manipulating linear flexible objects both in simulation and real world. To bridge the gap between simulation and real world and build a close-to-reality simulation of flexible objects, we propose a new strategy called Simulation-to-Real-to-Simulation (Sim2Real2Sim). We demonstrate the feasibility of our approach by completing the Plug Task used in the 2015 DARPA Robotics Challenge Finals both in simulation and real world, which involves unplugging a power cable from one socket and plugging it into another. Numerical experiments are implemented to validate our approach.
TL;DR: A proposed fractional order proportional integral derivative (FOPID) is optimized using the bat optimization algorithm to control the path tracking of the center of the 3-RRR planar parallel robot.
Abstract: 3-RRR planar parallel robots are utilized for solving precise material-handling problems in industrial automation applications. Thus, robust and stable control is required to deliver high accuracy in comparison to the state of the art. The operation of the mechanism is achieved based on three revolute (3-RRR) joints which are geometrically designed using an open-loop spatial robotic platform. The inverse kinematic model of the system is derived and analyzed by using the geometric structure with three revolute joints. The main variables in our design are the platform base positions, the geometry of the joint angles, and links of the 3-RRR planar parallel robot. These variables are calculated based on Cayley-Menger determinants and bilateration to determine the final position of the platform when moving and placing objects. Additionally, a proposed fractional order proportional integral derivative (FOPID) is optimized using the bat optimization algorithm to control the path tracking of the center of the 3-RRR planar parallel robot. The design is compared with the state of the art and simulated using the Matlab environment to validate the effectiveness of the proposed controller. Furthermore, real-time implementation has been tested to prove that the design performance is practical.
TL;DR: In this article, a knee support device using four-bar joint mechanism and hydraulic artificial muscle (HAM) was designed, which was able to generate a maximum output of 126.55 Nm torque at 100-degree knee joint angle during loading and 70.69 Nm during unloading at 3 MPa pressure.
Abstract: One of the main challenges for the elderly is insufficient lower limb strength during sit-to-stand movement, which may be improved by supporting the joint externally. Existing lower extremity exoskeletons use perfect revolute joints as knee joints, which do not match with human joint biomechanics. They also require a complex control system to produce the required torque at the corresponding joint angle. In this study, a knee support device using four-bar joint mechanism and hydraulic artificial muscle (HAM) was designed. A previously proposed four-bar linkage joint was modified to accommodate the HAM. In addition, the Angled Bar was proposed to exploit HAM’s force-contraction relationship to generate the desired torque at the corresponding angle only by applying constant hydraulic pressure without the use of a complex control system. The device was able to generate a maximum output of 126.55 Nm torque at 100$$^{\circ }$$ knee joint angle during loading and 70.69 Nm torque at 100$$^{\circ }$$ during unloading at 3 MPa pressure. The root-mean-square error of the knee extension torque curve was 13.01 Nm. Experiment with a healthy participant showed significant reduction in muscle activity with the assist from the device. The maximum processed EMG signal with and without assist were 52.10 and 20.93 $${\upmu \mathrm{V}}$$, respectively.
01 Sep 2020
TL;DR: The main objective is to tackle the problem of controlling the UAV independently of the robot manipulator using adaptive backstepping techniques utilizing a lower dimensional simplified model of the overall system.
Abstract: This paper focuses on the modelling and control of Unmanned Aerial Vehicles (UAVs) equipped with robotic arms, known as Unmanned Aerial Manipulators (UAMs). The main objective is to tackle the problem of controlling the UAV independently of the robot manipulator using adaptive backstepping techniques utilizing a lower dimensional simplified model of the overall system. To this end, we derive the full dynamics of the UAM. The proposed adaptive controller results in an aerial robot capable of all motions, while keeping computations to a minimum. The system studied consists of a UAV capable of lifting large payloads, equipped with 3 Degree of Freedom (DoF) revolute robotic manipulator. The efficiency of the proposed methods is verfified by simulating the designed aerial worker in various target tracking scenarios, which require simultaneous movement of all its components.
TL;DR: In this article, the authors proposed an approach for cantilever piezoelectric energy harvesters (PEHs) for frequency tuning and performance improvement by embedding of revolute joint(s) into PEH structure.
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TL;DR: A globally optimal solution to the Inverse Kinematics problem for a general serial 7DOF manipulator with revolute joints and a polynomial objective function and it is shown that the kinematic constraints due to rotations can be all generated by the second-degree polynomials.
Abstract: The Inverse Kinematics (IK) problem is concerned with finding robot control parameters to bring the robot into a desired position under the kinematics and collision constraints. We present a global solution to the optimal IK problem for a general serial 7DOF manipulator with revolute joints and a quadratic polynomial objective function. We show that the kinematic constraints due to rotations can be all generated by the second-degree polynomials. This is an important result since it significantly simplifies the further step where we find the optimal solution by Lasserre relaxations of nonconvex polynomial systems. We demonstrate that the second relaxation is sufficient to solve a general 7DOF IK problem. Our approach is certifiably globally optimal. We demonstrate the method on the 7DOF KUKA LBR IIWA manipulator and show that we are in practice able to compute the optimal IK or certify infeasibility in 99.9 % tested poses. We also demonstrate that by the same approach, we are able to solve the IK problem for a random generic manipulator with seven revolute joints.
TL;DR: This article focuses on the use of low-cost micro-electromechanical systems (MEMS) magnetic, angular rate, and gravity (MARG) sensors in the field of estimating the joint angles of revolute serial manipulators with an easy-to-install joint angle estimation method, named the incremental decomposition method (IDM).
Abstract: This article focuses on the use of low-cost micro-electromechanical systems (MEMS) magnetic, angular rate, and gravity (MARG) sensors in the field of estimating the joint angles of revolute serial manipulators. In particular, an easy-to-install joint angle estimation method, named the incremental decomposition method (IDM), is proposed. It allows the MEMS MARG sensors to be mounted in any attitude on any position of the manipulator's links, with at least one attitude measurement unit on the output side of each joint. The IDM is completely independent from the encoder-based joint angle estimator. Hence, it can work as an assistant fault-detection criterion for the economical robotic arms. A robotic arm with six degrees of freedom is used as the experimental setup. The IDM can estimate the manipulator's joint angles by fusing the attitude quaternion output by the MARG sensors. To validate the performances and limitations of this method, five experiments have been accomplished in this article. The experimental results are reported in order, in comparison with the high-resolution encoders.
TL;DR: A new Bricard-like mechanism composed of three anti-parallelogram units, simplified as a spatial single-loop overconstrained 6R mechanism with variable links’ lengths and its Denavit-Hartenberg parameters are obtained by identifying the six revolute joints axes.
TL;DR: It is shown that this particular assembly consisting of a pair of Bennett linkages connected by four spherical joints can be used to construct transformable polyhedrons, which has great potential for the aerospace applications where transportability and protection of payload are critical design features.
TL;DR: This paper deals with a special architecture of Spherical Parallel Manipulators designed to be a haptic device for a medical tele-operation system and the serial approach involving the use of three sensors located on one leg of the master device is revealed as the most suitable.
TL;DR: An analytical model is developed which approximates each face as a series of rigid facets connected by hinges that can both rotate and stretch and shows that membrane stretching of the faces is required when a conical form of deformation is enforced.
Abstract: Folded structures are often idealized as a series of rigid faces connected by creases acting as revolute hinges. However, real folded structures can deform between creases. An example of particular interest is a disk decorated by multiple radial creases. Such disks are bistable, snapping between a "natural" and "inverted" shape. We investigate the mechanical behavior of these creased disks and propose a new analytical approach to describe their mechanics. Detailed experiments are performed which show that, when indented at the center, a localized dimple forms, precluding the conical shape assumed in previous studies. As the indentation depth increases this dimple expands radially until reaching the disk edge when it snaps to the inverted shape, which has a conical form. We develop an analytical model which approximates each face as a series of rigid facets connected by hinges that can both rotate and stretch. Energy expressions are derived relating hinge rotation and stretching to compatible shell deformations of the facets and equilibrium enforced by minimizing the total strain energy. By increasing the number of facets, the mechanics of the continuum shell is approached asymptotically. The analysis shows that membrane stretching of the faces is required when a conical form of deformation is enforced. However, in the limit of zero thickness, the forming and propagation of a localized dimple is inextensional. This new approach relates the kinematic analysis of rigid origami to the mechanics of thin shells, offering an efficient method to predict the behavior of folded structures.
TL;DR: The results indicate that the 3D revolute clearance joint will lead to more severe effects on the dynamic characteristics of the satellite antenna system, and the effects of axial clearance on the satellite antennas cannot be ignored in dynamics analysis and design.
Abstract: Clearances in the joints of real mechanisms are unavoidable due to assemblage, manufacturing errors, and wear. The dual-axis driving and positioning mechanism is one kind of space actuating mechanism for satellite antenna to implement precise guidance and positioning. However, in dynamics analysis and control of the satellite antenna system, it is usually assumed that the revolute joint in the satellite antenna system is perfect without clearances or imperfect with planar radial clearance. However, the axial clearance in an imperfect revolute joint is always ignored. In this work, the revolute joint is considered as a 3D spatial clearance joint with both the radial and axial clearances. A methodology for modeling the 3D revolute joint with clearances and its application in satellite antenna system is presented. The dynamics modeling and analysis of the satellite antenna system are investigated considering the 3D revolute clearance joint. Firstly, the mathematical model of the 3D revolute clearance joint is established, and the definitions of the radial and axial clearance are presented. Then, the potential contact modes, contact conditions, and contact detection of the 3D revolute clearance joint are analyzed. Further, the normal and tangential contact force models are established to describe the contact phenomenon and determine the contact forces in the 3D revolute clearance joint. Finally, a satellite antenna system considering the 3D revolute clearance joint with spatial motion is presented as the application example. Different case studies are presented to discuss the effects of the 3D revolute clearance joint. The results indicate that the 3D revolute clearance joint will lead to more severe effects on the dynamic characteristics of the satellite antenna system. Therefore, the effects of axial clearance on the satellite antenna system cannot be ignored in dynamics analysis and design of the satellite antenna system.