DYNAMIC PERFORMANCE EVALUATION OF A THREE TRANSLATIONAL DEGREES OF FREEDOM PARALLEL ROBOT

2012 ◽  
Vol 27 (1) ◽  
Author(s):  
Yongjie Zhao
Keyword(s):  
Performance Evaluation ◽  
Degrees Of Freedom ◽  
Dynamic Performance ◽  
Parallel Robot

scholarly journals Parallel Robot Translational Performance Evaluation through Direction-Selective Index (DSI)

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
G. Boschetti ◽  
R. Rosa ◽  
A. Trevisani
Keyword(s):  
Performance Evaluation ◽  
Performance Index ◽  
General Framework ◽  
Dynamic Performance ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Performance Indexes ◽  
Definition Of ◽  
Performance Variations

Performance indexes usually provide global evaluations of robot performances mixing their translational and/or rotational capabilities. This paper proposes a definition of performance index, called direction-selective index (DSI), which has been specifically developed for parallel manipulators and can provide uncoupled evaluations of robot translational capabilities along relevant directions. The DSI formulation is first presented within a general framework, highlighting its relationship with traditional manipulability definitions, and then applied to a family of parallel manipulators (4-RUU) of industrial interest. The investigation is both numerical and experimental and allows highlighting the two chief advantages of the proposed DSIs over more conventional manipulability indexes: not only are DSIs more accurate in predicting the workspace regions where manipulators can best perform translational movements along specific directions, but also they allow foreseeing satisfactorily the dynamic performance variations within the workspace, though being purely kinematic indexes. The experiments have been carried out on an instrumented 4-RUU commercial robot.

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, isotropy, and velocity transmission evaluation of a three translational degrees-of-freedom parallel robot

Robotica ◽  
2012 ◽  
Vol 31 (2) ◽  
pp. 193-202 ◽  
Author(s):  
Yongjie Zhao
Keyword(s):  
Performance Evaluation ◽  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Parallel Robot ◽  
End Effector ◽  
Transmission Index ◽  
Delta Robot ◽  
Singular Configuration ◽  
Velocity Transmission

SUMMARYPerformance evaluation of a parallel robot is a multicriteria problem. By taking Delta robot as an object of study, this paper presents the kinematic performance evaluation of a three translational degrees-of-freedom parallel robot from the viewpoint of singularity, isotropy, and velocity transmission. It is shown that the determinant of a Jacobian matrix cannot measure the distance from the singular configuration due to the existing inverse kinematic singularity of a Delta robot. The determinants of inverse and direct kinematic Jacobian matrices are adopted for the measurement of distance from the singular configuration based on the theory of numerical linear dependence. The denominator of the Jacobian matrix will be lost in the computation of the condition number when the end-effector is on the centerline of the workspace, so the Delta robot may also be nearly at a singular configuration when the condition number of the Jacobian matrix is equal to 1. The velocity transmission index whose physical meaning is the maximum input angular velocity when the end-effector translates in the unit velocity is presented. The evaluation of singularity, isotropy, and velocity transmission of a Delta robot is investigated by simulation. The velocity transmission index can also be used for the velocity transmission evaluation of a parallel robot with pure rotational degrees-of-freedom based on the principle of similarity. The physical meaning is modified to be the maximum input velocity when the end-effector rotates in the unit angular velocity.

Investigation on the impact of nongeometric uncertainty in dynamic performance of serial and parallel robot manipulators

2018 ◽  
Vol 233 (10) ◽  
pp. 3487-3511 ◽  
Author(s):  
Ying-Kuan Tsai ◽  
Kuei-Yuan Chan
Keyword(s):  
Degrees Of Freedom ◽  
Robot Manipulators ◽  
Dynamic Performance ◽  
Uncertainty Modeling ◽  
Parallel Robot ◽  
Positional Error ◽  
Robot Manipulation ◽  
Practical Applications ◽  
Uncertainty Parameters ◽  
The Impact

Uncertainty in robot manipulations is a fundamental source of inaccuracy. Most nongeometric uncertainties is caused by the mechanical components of robot manipulators such as gear transmission systems and joints. This study integrates existing uncertainty models for practical applications of both three-degrees-of-freedom serial robot and parallel robot (closed-loop 5R mechanism). We first review the literature on uncertainty and existing methods for improving the precision of robot manipulation. For existing methods for uncertainty modeling: (1) the mathematical model of a harmonic drive considering kinematic error and compliance is derived; (2) joint clearance analysis that includes models of contact force and friction force is presented; (3) Archard’s wear model is used to estimate the effect of joint wear, based on which the geometry of joints is updated. Computer simulation is then used to demonstrate the application of the proposed method for serial and parallel robot manipulators. Simulations are used to examine the behavior of robot manipulators operating under uncertainty, with performance-evaluated positional error and trajectory error. The proposed method can provide some insight into nongeometric uncertainty in robot manipulations. The proposed methodology can be further used to improve the accuracy of robot manipulation under uncertainty by identifying uncertainty parameters.

Motion/Force Transmissibility Based Performance Evaluation of a 6-DOF Parallel Robot With 2-DOF Active Joints

2018 ◽  
Author(s):  
Bin Mei ◽  
Fugui Xie ◽  
Xin-Jun Liu ◽  
Xuan Luo
Keyword(s):  
Performance Evaluation ◽  
Degrees Of Freedom ◽  
Evaluation Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Six Degrees Of Freedom ◽  
Transmission Index ◽  
Force Transmissibility ◽  
Local Transmission ◽  
Active Joints

3-PP(Pa)S robot is a six degrees of freedom (DOFs) parallel mechanism with 2-DOF active planar joint. For the design and application of the 3-PP(Pa)S robot, it is essential to investigate the motion/force transmissibility of the robot. But previous studies of the motion/force transmissibility have mainly focused on the parallel robots with 1-DOF active joints and thus cannot be directly applied to the 3-PP(Pa)S robot. In this paper, input twist subspace, transmission wrench subspace and output twist subspace are investigated to build mathematical models of the twists and wrenches corresponding to the 2-DOF active planar joint. Afterwards, based on the previous established frame of the local transmission index, some extended performance evaluation indices are defined to describe the motion/force transmissibility of the 3-PP(Pa)S robot. On this basis, the singularity and motion/force transmissibility of this mechanism are investigated. The motion/force transmissibility evaluation method is meaningful and applicable for the 3-PP(Pa)S parallel robot with 2-DOF active joints and can be further applied to other mechanisms with multi-DOF active joints.

Analysis and Optimization of a New Differentially Driven Cable Parallel Robot

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Hamed Khakpour ◽  
Lionel Birglen ◽  
Souheil-Antoine Tahan
Keyword(s):  
Kinematic Analysis ◽  
Design Methodology ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Cable Robot ◽  
Proper Design ◽  
Two Indices ◽  
Three Degrees Of Freedom ◽  
Cable Robots

In this paper, a new three degrees of freedom (DOF) differentially actuated cable parallel robot is proposed. This mechanism is driven by a prismatic actuator and three cable differentials. Through this design, the idea of using differentials in the structure of a spatial cable robot is investigated. Considering their particular properties, the kinematic analysis of the robot is presented. Then, two indices are defined to evaluate the workspaces of the robot. Using these indices, the robot is subsequently optimized. Finally, the performance of the optimized differentially driven robot is compared with fully actuated mechanisms. The results show that through a proper design methodology, the robot can have a larger workspace and better performance using differentials than the fully driven cable robots using the same number of actuators.

Experimental and Analytical Investigations of a Low Pressure Model Turbine During Forced Response Excitation

2010 ◽  
Author(s):  
Christoph Heinz ◽  
Markus Schatz ◽  
Michael V. Casey ◽  
Heinrich Stu¨er
Keyword(s):  
Degrees Of Freedom ◽  
Timing Analysis ◽  
Dynamic Performance ◽  
Amplitude Distribution ◽  
Low Pressure ◽  
Forced Response ◽  
Operating Conditions ◽  
Linear Regression Method ◽  
Rotor Shaft ◽  
Aerodynamic Damping

To guarantee a faultless operation of a turbine it is necessary to know the dynamic performance of the machine especially during start-up and shut-down. In this paper the vibration behaviour of a low pressure model steam turbine which has been intentionally mistuned is investigated at the resonance point of an eigenfrequency crossing an engine order. Strain gauge measurements as well as tip timing analysis have been used, whereby a very good agreement is found between the methods. To enhance the interpretation of the data measured, an analytical mass-spring-model, which incorporates degrees of freedom for the blades as well as for the rotor shaft, is presented. The vibration amplitude varies strongly from blade to blade. This is caused by the mistuning parameters and the coupling through the rotor shaft. This circumferential blade amplitude distribution is investigated at different operating conditions. The results show an increasing aerodynamic coupling with increasing fluid density, which becomes visible in a changing circumferential blade amplitude distribution. Furthermore the blade amplitudes rise non-linearly with increasing flow velocity, while the amplitude distribution is almost independent. Additionally, the mechanical and aerodynamic damping parameters are calculated by means of a non-linear regression method. Based on measurements at different density conditions, it is possible to extrapolate the damping parameters down to vacuum conditions, where aerodynamic damping is absent. Hence the material damping parameter can be determined.

Optimal Design of a 4-DOF SCARA Type Parallel Robot Using Dynamic Performance Indices and Angular Constraints

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Songtao Liu ◽  
Tian Huang ◽  
Jiangping Mei ◽  
Xueman Zhao ◽  
Panfeng Wang ◽  
...  
Keyword(s):  
Optimal Design ◽  
Dynamic Performance ◽  
Parallel Robot ◽  
Singularity Analysis ◽  
Rigid Body Dynamics ◽  
Performance Indices ◽  
Global Dynamic ◽  
Transmission Angle ◽  
Body Dynamics ◽  
Rigid Design

This paper deals with the optimal design of a 4-DOF SCARA type (three translations and one rotation) parallel robot using dynamic performance indices and angular constraints within and amongst limbs. The architecture of the robot is briefly addressed with emphasis on the mechanical realization of the articulated traveling plate for achieving a lightweight yet rigid design. On the basis of the kinematic singularity analysis, two types of transmission angle constraints are considered to ensure the kinematic performance. A simplified model of rigid body dynamics is then formulated, with which two global dynamic performance indices are proposed for minimization by taking into account both inertial and centrifugal/Coriolis effects. In addition, the servomotor specifications are estimated using the Extended Adept Cycle. The proposed approach has successfully been employed to develop a prototype machine.

Sign in / Sign up

Export Citation Format

Share Document