Motion Characteristics Analysis of a Novel 2R1T 3-UPU Parallel Mechanism

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Chen Zhao ◽  
Ziming Chen ◽  
Yanwen Li ◽  
Zhen Huang
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Speed Control ◽  
Singularity Analysis ◽  
Mobile Platform ◽  
Rotational Axis ◽  
Constraint Forces ◽  
Parasitic Motion ◽  
Motion Characteristics

Abstract In this paper, a novel 3-UPU (P and U stand for prismatic and universal joints, respectively) parallel mechanism (PM) and its variant PM are proposed. Both of them have two rotational and one translational (2R1T) degrees of freedom (DOFs) without involving any parasitic motion. Mobility analysis shows that the three constraint forces provided by three limbs of the mechanism are located on the same plane and the mobile platform can translate perpendicular to this plane and rotate around any axis on it. Analysis of the mechanism’s motion characteristics demonstrates that the mobile platform outputs either pure rotation or pure translation. Moreover, the rotational axis can be fixed during the rotation process, which means no parasitic motion is involved. The causes of the motion characteristics are analyzed by the combination of an overall Jacobian matrix, a statistical method, and a geometric method. The PMs only need to translate or rotate once to move from the initial configuration to the final configuration, which allows for easy control of speeds. The relationship between mechanism parameters and singularity is analyzed. A speed control method for the PMs is proposed and a prototype is designed and made. Experiments are conducted to verify the determined motion characteristics, the speed control method, and the singularity analysis.

Influence Coefficients and Singularity Analysis of a Novel 3-UPU Parallel Mechanism

2017 ◽  
Author(s):  
Ziming Chen ◽  
Dongliang Cheng ◽  
Yang Zhang ◽  
Zhiwei Yang ◽  
Jin Zhou
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Model Simulation ◽  
Hessian Matrix ◽  
Symmetry Plane ◽  
Coefficient Matrix ◽  
Singularity Analysis ◽  
Influence Coefficient ◽  
Parasitic Motion ◽  
Moving Platform

A novel 3-UPU parallel mechanism with two rotational and one translational (2R1T) degrees of freedom (DOFs) is analyzed in this paper. The base and moving platform of this mechanism are always symmetric about a middle symmetry plane. The moving platform can rotate continuously about any axis on the middle symmetry plane, so there exists no parasitic motion during the rotation. Using the kinematic influence coefficient theory and the imaginary mechanism method, the first and second order influence coefficient matrix (namely Jacobian matrix and Hessian matrix) of this mechanism are derived. The relations between the velocity and acceleration of the moving platform and the actuated links are obtained. In order to verify the correctness of the theory, two numerical examples are enumerated and varified by the 3D model simulation. The singularities of this mechanism is discussed and the singular configurations of the mechanism, including one kind of limb singularity and two kinds of platform singularities, are obtained.

Controllable Rotation Workspace of a Metamorphic Parallel Mechanism With Reconfigurable Universal Joints

2013 ◽  
Author(s):  
Dongming Gan ◽  
Jian S. Dai ◽  
Jorge Dias ◽  
Lakmal D. Seneviratne
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Central Line ◽  
Singularity Analysis ◽  
Euler Angles ◽  
Base Plane ◽  
Constraint Forces ◽  
Joint Rotation ◽  
Universal Joints

This paper introduces a metamorphic parallel mechanism which has three topologies with pure translational, pure rotational and 3T1R degrees of freedom. Mobility change stemming from the reconfigurability of a reconfigurable Hooke (rT) joint is illustrated by change of the limb twist screw systems and the platform constraint screw system. Then the paper focuses on the pure rotational topology of the mechanism of which the rotational center can be altered along the central line perpendicular to the base plane by altering the radial rotational axes in the limbs. Singularity analysis is conducted based on the dependency of constraint forces and actuation forces in a screw based Jacobian matrix. Following these, rotation workspace variation is demonstrated in a 2D projection format using the Tilt-and-Torsion Euler angles based on the actuation limits and joint rotation ranges.

Continuous motion of a novel 3-CRC symmetrical parallel mechanism

2015 ◽  
Vol 230 (3) ◽  
pp. 392-405 ◽  
Author(s):  
Ziming Chen ◽  
Wen-ao Cao ◽  
Huafeng Ding ◽  
Zhen Huang
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Parallel Mechanisms ◽  
Numerical Examples ◽  
Parasitic Motion ◽  
Continuous Rotation ◽  
Moving Platform ◽  
Motion Characteristics ◽  
Three Degrees Of Freedom

Parallel mechanisms (PMs) with three degrees of freedom (DOFs) have been studied extensively, especially the PMs with two rotational and one translational DOFs (2R1T PMs). One major problem of the 2R1T PMs is the inherent parasitic motion. In this paper, a novel 2R1T symmetrical parallel mechanism with no parasitic motion is proposed and studied. The moving platform and the base of this mechanism are mirror symmetric with respect to a mid-plane. This moving platform can realize continuous rotation about any axis or any point on the mid-plane and can have continuous translation along the normal line of the mid-plane. The constraint and motion characteristics of this mechanism are analyzed. The kinematics solutions and the Jacobian matrix are derived. The singularities of this PM are discussed. In the end, several numerical examples are given to show the continuous rotations and continuous translations of this PM. This kind of PMs has outstanding advantages of easy path planning and controlling.

scholarly journals Optimum Seeking of Redundant Actuators for M-RCM 3-UPU Parallel Mechanism

2020 ◽  
Author(s):  
Chen Zhao ◽  
Jingke Song ◽  
Xuechan Chen ◽  
Ziming Chen ◽  
Huafeng Ding
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Universal Joint ◽  
Prismatic Joint ◽  
Transmission Index ◽  
Redundant Actuators ◽  
Force Transmissibility ◽  
Singular Configuration

Abstract This paper focuses on a 2R1T 3-UPU (U for universal joint and P for prismatic joint) parallel mechanism (PM) with two rotational and one translational (2R1T) degrees of freedom (DOFs) and the ability of multiple remote centers of motion (M-RCM). The singularity analysis based on the indexes of motion/force transmissibility and constraint shows that this PM has transmission singularity, constraint singularity, mixed singularity and limb singularity. To solve these singularproblems, the quantifiable redundancy transmission index (RTI) and the redundancy constraint index (RCI) are proposed for optimum seeking of redundant actuators for this PM. Then the appropriate redundant actuators are selected and the working scheme for redundant actuators near the corresponding singular configuration are given to help the PM go through the singularity.

Kinematics of a Pure Translational UPS/3RPaPaR Parallel Mechanism

2007 ◽  
Author(s):  
Chung-Ching Lee ◽  
Po-Chih Lee
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Translational Motion ◽  
Singularity Analysis ◽  
Inverse Kinematic ◽  
Geometric Constraints ◽  
Design Parameters ◽  
Numerical Illustration ◽  
The Matrix ◽  
Kinematic Analyses

From the viewpoint of kinematics, a type of 3 degrees of freedom (dofs) UPS/3RPaPaR overconstrained parallel mechanism (Pa means the hinged 4R parallelogram) with pure translational motion is presented for the development of automatic assembly devices or as a regional structure in the hybrid parallel platform. In the beginning, the formation & mobility are elucidated and the 4×4 transformation matrix & the D-H notation with specific geometric constraints verify the pure translational motion. The forward and inverse kinematic analyses are then established in the analytical closed-form through the matrix method. Besides, we take a numerical illustration for the confirmation of correctness of the derived equations. The determination of workspace is also attained by the intersection of volumes swept by each limb. In addition, the Jacobian matrix and its condition number indicated by Euclidean norm as a function of design parameters are further achieved. Finally, the singularity analysis of the configuration based on the direct and inverse kinematic J-matrix during the movement is identified in detail.

A REAL-TIME EMG-DRIVEN ARM WRESTLING ROBOT CONSIDERING MOTION CHARACTERISTICS OF HUMAN UPPER LIMBS

2007 ◽  
Vol 04 (04) ◽  
pp. 645-670 ◽  
Author(s):  
QUANJUN SONG ◽  
YONG YU ◽  
YUNJIAN GE ◽  
ZHEN GAO ◽  
HUANGHUAN SHEN ◽  
...  
Keyword(s):  
Neural Network ◽  
Real Time ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Wavelet Packet ◽  
Neuromuscular Control ◽  
Joint Force ◽  
Mems Accelerometers ◽  
Usb Camera ◽  
Motion Characteristics

An EMG-driven Arm Wrestling Robot (AWR) is developed for the purposes of studying neuromuscular control of human elbow movements. The AWR arm has two degrees-of-freedom, integrated with mechanical arm, elbow/wrist force sensors, servo motors, encoders, MEMS accelerometers, and a USB camera, and is used to estimate tension generated by individual muscles from recorded electromyograms (EMG). The surface electromyography signal from the upper limb is sampled from a real player in the same conditions. By using the method of wavelet packet transformation (WPT) and autoregressive model (AR), the characteristics of EMG signals can be extracted. Then, an artificial neural network is adopted to estimate the elbow joint force. The effectiveness of the control method using force control estimated via neural network using WPT and AR as inputs is confirmed by experiments. The purpose of this paper is to describe the design objectives, fundamental components, and implementation of our real-time, EMG-driven AWR arm.

Singularity Analysis of Large Workspace 3RRRS Parallel Mechanism Using Line Geometry and Linear Complex Approximation

2010 ◽  
Vol 3 (1) ◽  
Author(s):  
Alon Wolf ◽  
Daniel Glozman
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Singularity Analysis ◽  
Community Research ◽  
Parallel Mechanisms ◽  
Line Geometry ◽  
Equilibrium Equations ◽  
Six Degrees Of Freedom ◽  
Singular Configurations

During the last 15 years, parallel mechanisms (robots) have become more and more popular among the robotics and mechanism community. Research done in this field revealed the significant advantage of these mechanisms for several specific tasks, such as those that require high rigidity, low inertia of the mechanism, and/or high accuracy. Consequently, parallel mechanisms have been widely investigated in the last few years. There are tens of proposed structures for parallel mechanisms, with some capable of six degrees of freedom and some less (normally three degrees of freedom). One of the major drawbacks of parallel mechanisms is their relatively limited workspace and their behavior near or at singular configurations. In this paper, we analyze the kinematics of a new architecture for a six degrees of freedom parallel mechanism composed of three identical kinematic limbs: revolute-revolute-revolute-spherical. We solve the inverse and show the forward kinematics of the mechanism and then use the screw theory to develop the Jacobian matrix of the manipulator. We demonstrate how to use screw and line geometry tools for the singularity analysis of the mechanism. Both Jacobian matrices developed by using screw theory and static equilibrium equations are similar. Forward and inverse kinematic solutions are given and solved, and the singularity map of the mechanism was generated. We then demonstrate and analyze three representative singular configurations of the mechanism. Finally, we generate the singularity-free workspace of the mechanism.

scholarly journals Research on Kinematics and Pouring Law of a Mobile Heavy Load Pouring Robot

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Long Li ◽  
Chengjun Wang ◽  
Hongtao Wu
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Position Control ◽  
Screw Theory ◽  
Great Influence ◽  
Inverse Kinematic ◽  
The Novel ◽  
Heavy Load ◽  
Motion Characteristics ◽  
The Relationship

In order to meet the requirement of continuous pouring in many varieties and small batches in casting production, a mobile heavy load pouring robot is developed based on a new 4-UPU parallel mechanism due to its strong carrying capacity. Firstly, the instantaneous motion characteristics of the novel 4-UPU parallel mechanism with four degrees of freedom (DOF) are analyzed using screw theory. By using the geometric method, both the forward and inverse kinematic solutions of the proposed robot system are given out. Secondly, based on a common pouring ladle, the volume change of pouring liquid in pouring process and the relationship between tilting angular velocity and flow rate are analyzed, and the results show that the shape of the ladle and the design of the pouring mouth have great influence on the tilting model. It is an important basis for the division of the sectional model. Finally, a numerical example is given to verify the effectiveness of the developed tilting model. The mapping relation between the tilting model and the parallel mechanism shows that the pouring flow can be adjusted by controlling the movement of parallel manipulator. The research of this paper provides an important theoretical basis for the position control of mobile heavy load pouring robot and the research of pouring speed control.

Investigation of a novel 2R1T parallel mechanism and construction of its variants

Robotica ◽  
2021 ◽  
pp. 1-15
Author(s):  
Jingfang Liu ◽  
Xiangmeng Fan ◽  
Huafeng Ding
Keyword(s):  
Inverse Kinematics ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Rotation Axis ◽  
End Effector ◽  
Parasitic Motion ◽  
Structure Synthesis ◽  
Synthesis Strategy ◽  
Continuous Rotation ◽  
Large Rotations

Abstract A 3-RRPRR variable spherical symmetrical parallel mechanism (PM) with arc-shaped sliding pairs and no parasitic motion is presented, exhibiting two rotational and one translational (2R1T) degrees of freedom. Three limbs are symmetrically distributed between the base and end-effector; upper and lower parts of each limb are mirror symmetrical around the middle. The geometry, mobility, forward/inverse kinematics, workspace, and parasitic motion of the mechanism are analyzed, showing its ability to achieve large rotations around a continuous rotation axis. Finally, a structure synthesis strategy for variable spherical symmetrical PM is proposed, and several limb types meeting the conditions are obtained.

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