Analysis and Design of the 2PRU-1PRS Manipulator for Vibration Testing

2014 ◽  
Author(s):  
Saioa Herrero ◽  
Charles Pinto ◽  
Oscar Altuzarra ◽  
Constantino Roldan-Paraponiaris
Keyword(s):  
Graphical User Interface ◽  
Degrees Of Freedom ◽  
Good Accuracy ◽  
Parallel Manipulators ◽  
Inverse Kinematic ◽  
Serial Manipulators ◽  
Analysis And Design ◽  
Parasitic Motion ◽  
Payload Capacity ◽  
Vibration Tests

Parallel manipulators, compared to serial manipulators, have some interesting properties, such as high stiffness, low inertia, high velocity, good accuracy and large payload capacity. Thus, parallel manipulators, especially the ones with one translation and two rotations as outputs (1T2R), are being increasingly studied. The 3PRS mechanism is a very typical example of this category, but it has accuracy problems caused by the parasitic motion, and low orientation capability. To overcome these problems, new mechanisms are being studied, such as the 2PRU-1PRS manipulator. As the 3PRS manipulator, the degrees of freedom of the 2PRU-1PRS are one translation along the Z-axis and two rotations about the X- and Y-axes. The advantages are that the parasitic motion appears only in one direction instead of in three and that the orientation capability is higher. In this paper we present the design of a 2PRU-1PRS mechanism suitable for vibration tests. In order to do this, we develop a code with an intuitive GUI (graphical user interface) that, for given variable limits, solves the inverse kinematic and dynamic problem for all the variable combinations and obtains the combination that consumes less power for an harmonic trajectory. Taking the simulations results into account, we propose a design that fulfils all the requirements for vibration tests in the three axes.

Kinematics, Workspace Optimization, and Performance Evaluation of a 3-Leg 6-DOF Robot in RRRS Configuration

2020 ◽  
Author(s):  
Nathan A. Jensen ◽  
Carl A. Nelson
Keyword(s):  
Performance Evaluation ◽  
Degrees Of Freedom ◽  
Experimental Validation ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Inverse Kinematic ◽  
And Performance ◽  
Workspace Optimization ◽  
Optimization And Performance

Abstract Underactuated parallel manipulators that achieve 6 DOF via multiple controllable degrees of freedom per leg are often pursued and reported due to their large workspaces. This benefit comes at a cost to the manipulator’s performance, however. Such manipulators must then be evaluated in order to characterize their kinematics in terms of position and motion. This paper establishes a pair of inverse kinematic solutions for a previously proposed and prototyped 3-leg, 6-DOF parallel robot. These solutions are then used to define the robot’s workspace with experimental validation and to optimize the robot’s geometry for maximum workspace volume. The linear components of the Jacobian are then defined, allowing for analysis of the manipulability of the robot. The full Jacobian is also defined, and singularities are examined throughout the workspace of the robot.

Singularity robust balancing of parallel manipulators following inconsistent trajectories

Robotica ◽  
2014 ◽  
Vol 34 (9) ◽  
pp. 2027-2038 ◽  
Author(s):  
Mustafa Özdemir
Keyword(s):  
Equations Of Motion ◽  
Parallel Manipulators ◽  
Inverse Kinematic ◽  
Type I ◽  
Type Ii ◽  
Inverse Dynamic ◽  
Serial Manipulators ◽  
Dynamic Solution ◽  
Singular Configuration ◽  
Kinematic Singularities

SUMMARYWhen compared to serial manipulators, parallel manipulators have small workspaces mainly due to their closed-loop structure. As opposed to type I singularities (or inverse kinematic singularities) that are generally encountered at the workspace boundaries, type II singularities characteristically arise within the workspace, and around them, the inverse dynamic solution becomes unbounded. Hence, a desired trajectory passing through a type II singular position cannot be achieved by the manipulator, and its useful workspace becomes further and substantially reduced. It has been previously shown in the literature that if the trajectory is replanned in such a way that the dynamic equations of motion of the manipulator are consistent at a type II singularity, i.e. if the trajectory is consistent, then the manipulator passes through this singular configuration in a controllable manner, while the inverse dynamic solution remains finite. An inconsistent trajectory, on the other hand, is stated in the literature to be unrealizable. However, although seems a promising technique, trajectory replanning itself is also a deviation from the originally desired trajectory, and there might be cases in applications where, due to some task-specific reasons, the desired trajectory, although inconsistent, is not allowed to be replanned to satisfy the consistency conditions. In this paper, a method of singularity robust balancing is proposed for parallel manipulators passing through type II singular configurations while following inconsistent trajectories. By this means, an originally unrealizable inconsistent trajectory passing through a type II singularity can be followed without any deviation, while the required actuator forces remain bounded after the manipulator is balanced according to the design methodology presented in this study. The effectiveness of the introduced method is shown through numerical simulations considering a planar 3-DOF 2-PRR parallel manipulator under different balancing scenarios.

scholarly journals Inverse kinematic analysis of 3 DOF 3-PRS PM for machining on inclined prismatic surfaces

2020 ◽  
Vol 9 (2) ◽  
pp. 135
Author(s):  
Hishantkumar Rashmikantbhai Patel ◽  
Yashavant Patel
Keyword(s):  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Industrial Applications ◽  
Inverse Kinematic ◽  
Medical Surgery ◽  
Space Technology ◽  
Serial Manipulators ◽  
Part Surface ◽  
Primary Focus ◽  
Structural Architecture

<p>Parallel Manipulators (PMs) are family members of modern manipulators based on the closed loop structural architecture. 3-PRS (prismatic, revolute, spherical) manipulator with 3DOF is investigated for its machining capability on prismatic surfaces as it possesses greater structural stiffness, higher pay load caring capacity, more precision compare to serial manipulators as well as less accumulation of errors at joints within a constrained workspace. The said manipulator can be utilized in various fields of application such as precise manufacturing, medical surgery, space technology and many more. In this paper, the primary focus on usage of parallel manipulator in industrial applications such as drilling and grooving on inclined work part surface. Inverse kinematic solutions are used for drilling, square and round profiles on inclined surface using parallel manipulator.</p>

DeltaBot: A New Cable-Based Ultra High Speed Robot

2003 ◽  
Author(s):  
Saeed Behzadipour ◽  
Robert Dekker ◽  
Amir Khajepour ◽  
Edmon Chan
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Manufacturing Industry ◽  
Design Procedure ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Manufacturing Cost ◽  
End Effector ◽  
Serial Manipulators

The growing needs for high speed positioning devices in the automated manufacturing industry have been challenged by robotic science for more than two decades. Parallel manipulators have been widely used for this purpose due to their advantage of lower moving inertia over the conventional serial manipulators. Cable actuated parallel robots were introduced in 1980’s to reduce the moving inertia even further. In this work, a new cable-based parallel robot is introduced. For this robot, the cables are used not only to actuate the end-effector but also to apply the necessary kinematic constraints to provide three pure translational degrees of freedom. In order to maintain tension in the cables, a passive air cylinder is used to push the end-effector against the stationary platform. In addition to low moving inertia, the new design benefits from simplicity and low manufacturing cost by eliminating joints from the robot’s mechanism. The design procedure and the results of experiments will be discussed in the following.

Geometry and Position Analysis of a Novel Class of Hybrid Manipulators

1994 ◽  
Author(s):  
Change-de Zhang ◽  
Shin-Min Song
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Serial Manipulators ◽  
Closed Form Solutions ◽  
Position Analysis ◽  
Hybrid Manipulator ◽  
Load Carrying ◽  
Inverse Position Analysis

Abstract This paper presents a novel class of hybrid manipulators composed of two serially connected parallel mechanisms, each of which has three degrees of freedom. The lower and upper platforms respectively control the position and orientation of the end-effector. The advantages of this type of hybrid manipulator are larger workspace (as compared with parallel manipulators) and better rigidity and higher load-carrying capability (as compared with serial manipulators). The closed-form solutions of the forward and inverse position analyses are discussed. For forward position analysis, it is shown that the resultant equation for the positional mechanism is an 8-th order, a 6-th order, a 4-th order, or a 2-nd order polynomial, depending on the geometry and joint types of the passive subchain, while for the orientational mechanism, it is an 8-th order, or a 2-nd polynomial depending on the geometry. For inverse position analysis, it is demonstrated that the positional and orientational mechanisms both possess analytical closed-form solutions.

Kinematic analysis of overconstrained manipulators with partial subspaces using decomposition method

Robotica ◽  
2021 ◽  
pp. 1-16
Author(s):  
Özgün Selvi
Keyword(s):  
Kinematic Analysis ◽  
Decomposition Method ◽  
Degrees Of Freedom ◽  
Additional Data ◽  
Parallel Manipulators ◽  
Inverse Kinematic ◽  
Velocity Analysis ◽  
Workspace Analysis ◽  
Inverse Kinematic Analysis ◽  
Inverse Velocity

SUMMARY Overconstrained manipulators in lower subspaces with unique motions can be created and analyzed. However, far too little attention has been paid to creating a generic method for overconstrained manipulators kinematic analysis. This study aimed to evaluate a generic methodology for kinematic analysis of overconstrained parallel manipulators with partial subspaces (OPM-PS) using decomposition to parallel manipulators (PMs) in lower subspaces. The theoretical dimensions of the method are depicted, and the use of partial subspace for overconstrained manipulators is portrayed. The methodology for the decomposition method is described and exemplified by designing and evaluating the method to two overconstrained manipulators with 5 degrees of freedom (DoF) and 3 DoF. The inverse kinematic analysis is detailed with position analysis and Jacobian along with the inverse velocity analysis. The workspace analysis for the manipulators using the methodology is elaborated with numerical results. The results of the study show that OPM-PS can be decomposed into PMs with lower subspace numbers. As imaginary joints are being utilized in the proposed methodology, it will create additional data to consider in the design process of the manipulators. Thus, it becomes more beneficial in design scenarios that include workspace as an objective.

Redundancy Resolution of Kinematically Redundant Parallel Manipulators Via Differential Dynamic Programing

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
João Cavacanti Santos ◽  
Maíra Martins da Silva
Keyword(s):  
Parallel Manipulators ◽  
Projection Methods ◽  
Inverse Kinematic ◽  
Gradient Projection ◽  
Redundancy Resolution ◽  
Inverse Kinematic Problem ◽  
Serial Manipulators ◽  
Optimal Inputs ◽  
Dynamic Programing ◽  
Gradient Projection Methods

Kinematic redundancy may be an efficient way to improve the performance of parallel manipulators. Nevertheless, the inverse kinematic problem of this kind of manipulator presents infinite solutions. The selection of a single kinematic configuration among a set of many possible ones is denoted as redundancy resolution. While several redundancy resolution strategies have been proposed for planning the motion of redundant serial manipulators, suitable proposals for parallel manipulators are seldom. Redundancy resolution can be treated as an optimization problem that can be solved locally or globally. Gradient projection methods have been successfully employed to solve it locally. For global strategies, these methods may be computationally demanding and mathematically complex. The main objective of this work is to exploit the use of differential dynamic programing (DDP) for decreasing the computational demand and mathematical complexity of a global optimization based on the gradient projection method for redundancy resolution. The outcome of the proposed method is the optimal inputs for the active joints for a given trajectory of the end-effector considering the input limitations and different cost functions. Using the proposed method, the performance of a redundant 3PRRR manipulator is investigated numerically and experimentally. The results demonstrate the capability and versatility of the strategy.

scholarly journals Optimization of 3-DoF Manipulators’ Parasitic Motion with the Instantaneous Restriction Space-Based Analytic Coupling Relation

2021 ◽  
Vol 11 (10) ◽  
pp. 4690
Author(s):  
Hassen Nigatu ◽  
Doik Kim
Keyword(s):  
Degrees Of Freedom ◽  
Search Algorithm ◽  
Constraint Equation ◽  
Parallel Manipulators ◽  
Pattern Search ◽  
Motion Equation ◽  
Parasitic Motion ◽  
Geometric Variables ◽  
Quasi Newton ◽  
Velocity Level

This paper presents a velocity-level approach to optimizing the parasitic motion of 3-degrees of freedom (DoFs) parallel manipulators. To achieve this objective, we first systematically derive an analytical velocity-level parasitic motion equation as a primary step for the optimization. The paper utilizes an analytic structural constraint equation that describes the manipulator’s restriction space to formulate the parasitic motion equation via the task variable coupling relation. Then, the relevant geometric variables are identified from the analytic coupling equation. The Quasi-Newton method is used for the direction-specific minimization, i.e., optimizing either the x-axis or y-axis parasitic motion. The pattern-search algorithm is applied to optimize all parasitic terms from the workspace. The proposed approach equivalently describes the 3-PhRS, 3-PvRS, 3RPS manipulators. Moreover, other manipulators within a similar category can be equivalently expressed by the proposed method. Finally, the paper presents the resulting optimum configurations and numerical simulations to demonstrate the approach.

scholarly journals Kineto-Static Analysis and Design Optimization of a 3-DOF Wrist Rehabilitation Parallel Robot with Consideration of the Effect of the Human Limb

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 323
Author(s):  
Ying-Chi Liu ◽  
Kosuke Irube ◽  
Yukio Takeda
Keyword(s):  
Static Analysis ◽  
Parallel Robot ◽  
Interaction Force ◽  
Inverse Kinematic ◽  
Design Parameters ◽  
Analysis And Design ◽  
Parasitic Motion ◽  
Rehabilitation Robots ◽  
Inverse Kinematic Analysis ◽  
Human Limb

When designing rehabilitation robots, there remains the challenge of ensuring the comfort and safety of users, especially for wearable rehabilitation robots that interact with human limbs. In this paper, we present a kineto-static analysis of the 3-RPS parallel wrist rehabilitation robot, taking into account the soft characteristics of the human limb and its kinematic mobility. First, the human upper-limb model was made to estimate the interaction force and moment through inverse kinematic analysis. Second, a static analysis was conducted to obtain the force and moment acting on the human limb, which is directly related to the user’s comfort and safety. Then, the design parameters of the 3-RPS robot were obtained by generic optimization through kineto-static analysis. Finally, the influence of the parasitic motion of the 3-RPS robot and the initial offset between the wrist center and the robot moving platform were discussed. Through the analysis results, we provide effective solutions to ensure the safety and comfort of the user.

Evaluation of Force/Torque Transmission Quality for Parallel Manipulators

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Xiang Chen ◽  
Chao Chen ◽  
Xin-Jun Liu
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Analysis And Design ◽  
Torque Transmission ◽  
Transmission Index ◽  
Internal Forces ◽  
Transmission Quality ◽  
End Effectors ◽  
External Loads

Performance evaluation is one of the most important issues in the analysis and design of parallel manipulators. The internal forces and torques in parallel manipulators contribute to manipulating the end-effectors and resisting the external loads. In this work, we propose a transmission index to evaluate the force and torque transmission quality of parallel manipulators. The index is normalized and used to analyze the exactly constrained parallel manipulators, based on the transmission matrix spanned by transmission wrench screws (TWSs). Furthermore, the index is applied to parallel manipulators with different degrees of freedom (DOF) in order to illustrate and validate the proposed approach and index. Finally, a typical parallel manipulator is selected to address the comparison analysis between different indices, which demonstrates that the proposed index, possessing respective merits, could be complementary to other existing indices.

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