Investigation of Positional Error in Two Degree of Freedom Mechanism With Joint Clearance

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
H. P. Jawale ◽  
H. T. Thorat
Keyword(s):  
Closed Loop ◽  
Robotic Manipulators ◽  
Simple Approach ◽  
Joint Clearance ◽  
Positional Error ◽  
Link Length ◽  
Positional Accuracy ◽  
Positional Analysis ◽  
Closed Chain ◽  
Two Degree Of Freedom

Closed chain mechanisms are used as robotic manipulators with special features. A planar two-DOF closed loop mechanism provides desired position of an end effecter in a confined workspace with two input motions. Position of end effecter depends on various factors including joint clearance. Positional accuracy forms important parameter for kinematic analysis of mechanism. This paper presents simple approach for quantifying error due to joint clearance in a two-DOF mechanism. Generalized scheme for positional deviation with and without clearance at joint is presented. Orientation of clearance links for maximum positional error is identified. Error at various positions is quantified in relation with clearance link length. Computer programming is used as a tool to workout positional analysis of mechanism. Results show that error is independent of magnitude of clearance, however, a function of location of end effecter in workspace.

Comparison of Open Chain and Closed Chain Planar Two Degree of Freedom Manipulator for Positional Error

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
H. P. Jawale ◽  
H. T. Thorat
Keyword(s):  
Geometric Approach ◽  
Degree Of Freedom ◽  
The Other ◽  
Dimensionless Number ◽  
Positional Error ◽  
Positional Accuracy ◽  
Open Chain ◽  
Closed Chain ◽  
Error Index ◽  
Two Degree Of Freedom

Open chain and closed chain manipulators are designed for specific objectives. Closed chain five bar manipulator is possible to be configured as a substitute to an open chain two degree of freedom (DoF) manipulator. Positional accuracy is one of the factors for performance evaluation, characterizing suitability of a configuration over the other. Present paper attempts comparative analysis of positional inaccuracy of closed chain five bar manipulator and serial chain configuration. Both manipulators are modeled for positional deviations under identical specifications considering randomness due to joint clearances and backlash in drive. The maximum positional inaccuracy is expressed in terms of dimensionless number as error index (EI) to estimate the comparative behavior of the manipulators. Positional error under influence of backlash and clearances is quantified. Comparison of two configurations is presented and conditional superiority of a configuration over the other is commented using geometric approach.

Tolerance Analysis of a Robot Manipulator Having Uncertainties in Joint Clearance and Axis Orientation

2007 ◽  
Author(s):  
Dong Hwan Choi ◽  
Se Jeong Lee ◽  
Jonathan A. Wickert ◽  
Hong Hee Yoo
Keyword(s):  
Robot Manipulator ◽  
Statistical Design ◽  
Tolerance Analysis ◽  
Joint Clearance ◽  
Design Parameters ◽  
Positional Error ◽  
Link Length ◽  
Axis Orientation ◽  
Manufacturing Tolerances ◽  
Clearance Model

The operating positional error of a robot manipulator, which develops inevitably because of manufacturing tolerances and assembly clearances, is preferentially maintained within a certain range in order to achieve an acceptable level of performance and accuracy. Because additional cost is incurred when manufacturing tolerances are tightened, an alternative design strategy maximizes the tolerances (so as to reduce the cost) while minimizing positioning error (to satisfy a performance requirement). In this paper, a new joint clearance model is developed for spatial mechanisms that incorporate revolute joints, which in turn are subjected to specified tolerance or uncertainty in the orientation of their axes. Statistical design parameters related to variations of link length and joint axis orientation are identified from the clearance model. The statistical influence of the design parameters on the robot manipulator’s response is investigated through a general multibody dynamics sensitivity formulation. The method offers substantial improvement in computational efficiency when compared to the Monte Carlo procedure. The uncertainty in orientation of a revolute joint’s axis influences the positioning accuracy of the robot manipulator’s response to a greater degree than does uncertainty in the length of a link.

Positional Accuracy Analysis in Serial Chain and Four-Bar Closed Chain Manipulator

2014 ◽  
Author(s):  
H. P. Jawale ◽  
H. T. Thorat
Keyword(s):  
Sample Path ◽  
Dimensionless Number ◽  
Positional Error ◽  
Input Constraints ◽  
Positional Accuracy ◽  
Serial Chain ◽  
Closed Chain ◽  
Serial Robot ◽  
Joint Clearances ◽  
Error Index

Serial chain robots are integral part of industrial automation. Better reach within workspace, higher Degree of Freedom (DoF), flexibility and positional accuracy are credit performance features behind its wide acceptance. The flexibility and higher DoF of this configuration is underutilized, when it is used for a repetitive task in hard automation. The present paper considers application of closed chain four-bar mechanism as substitute of a serial chain robot for repetitive task involving single trajectory generation. The manipulators are modelled for positional accuracy under the influence of joint clearances and drive backlash. The positional error in both manipulators for a coupler point on sample path is estimated. The manipulators are considered to operate with identical input constraints. The error is expressed in terms of dimensionless number-as Error Index to estimate the comparative behaviour of the manipulators. The paper presents method of analysing the performance of a closed chain manipulator over serial robot.

scholarly journals Position Accuracy Analysis on Disc Storing Mechanism for Benthic Drill

2014 ◽  
Vol 8 (1) ◽  
pp. 382-386
Author(s):  
Y. Guo ◽  
Y. P. Jin ◽  
M. Jiang ◽  
B. W. Luo
Keyword(s):  
Analytical Formula ◽  
Mathematic Model ◽  
Hydraulic Cylinder ◽  
Positional Error ◽  
Accuracy Analysis ◽  
Positional Accuracy ◽  
Positional Analysis ◽  
Cylinder Length ◽  
Dimensional Parameters ◽  
Nonlinear Iteration

The positional accuracy of disc storing mechanism for benthic drill is the guarantee of long hole coring in deep sea. Aiming the lack of positional accuracy analysis on disc storing mechanism, the mathematic model of the positional accuracy for disc storing mechanism is presented by using complex vector and matrix analyzing method. The analytical formula of crank rotation positional accuracy is acquired through rotation positional analysis of crank in disc storing mechanism driven by hydraulic cylinder. Adopting numerical nonlinear iteration solution method of Newton-Simpson, the variation rule of rotation positional error for disc storing mechanism to cylinder length is acquired, which supports an important theory, leading to tolerance design for dimensional parameters of disc storing mechanism.

Integrated Kinematic Calibration for All the Parameters of a Planar 2DOF Redundantly Actuated Parallel Manipulator

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Chunshi Feng ◽  
Shuang Cong ◽  
Weiwei Shang
Keyword(s):  
Parallel Manipulator ◽  
Closed Loop ◽  
Open Loop ◽  
Kinematic Calibration ◽  
Constraint Equations ◽  
Integrated Method ◽  
Uniqueness Of The Solution ◽  
Redundantly Actuated ◽  
Loop Constraint ◽  
Two Degree Of Freedom

In this paper, the kinematic calibration of a planar two-degree-of-freedom redundantly actuated parallel manipulator is studied without any assumption on parameters. A cost function based on closed-loop constraint equations is first formulated. Using plane geometry theory, we analyze the pose transformations that bring infinite solutions and present a kinematic calibration integrated of closed-loop and open-loop methods. In the integrated method, the closed-loop calibration solves all the solutions that fit the constraint equations, and the open-loop calibration guarantees the uniqueness of the solution. In the experiments, differential evolution is applied to compute the solution set, for its advantages in computing multi-optima. Experimental results show that all the parameters involved are calibrated with high accuracy.

Backlash Compensation on CNC Machine Tool Based on Semi-Closed Loop Control

2011 ◽  
Vol 346 ◽  
pp. 644-649 ◽  
Author(s):  
Bin Feng ◽  
Xue Song Mei ◽  
Liang Guo ◽  
Dong Sheng Zhang ◽  
You Long Cheng
Keyword(s):  
Machine Tool ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Cnc Machine Tool ◽  
Cnc Machine ◽  
Positional Accuracy ◽  
Loop Control ◽  
Open Cnc ◽  
Contouring Error ◽  
Open Cnc System

The positional accuracy and machining precision are mainly affected by backlash for semi-closed loop control CNC machine tool. And compensation for backlash is essential to improving the accuracy of machine tool. A method is developed to reduce contouring error in this paper. A simulated model of backlash and Open CNC system are used to verify compensation algorithm. Computational simulations and experimental results have shown that the contouring error due to backlash can be greatly reduced by using backlash compensation.

A Generalized Performance Sensitivity Synthesis Methodology for Four-Bar Mechanisms

1992 ◽  
Author(s):  
Ming-Yih Lee ◽  
Arthur G. Erdman ◽  
Salaheddine Faik
Keyword(s):  
Solution Space ◽  
Design Solution ◽  
Link Length ◽  
Performance Sensitivity ◽  
Closed Chain ◽  
Synthesis Methodology ◽  
Position Synthesis ◽  
The Relationship ◽  
Accuracy Performance ◽  
Sensitivity Maps

Abstract A generalized accuracy performance synthesis methodology for planar closed chain mechanisms is proposed. The relationship between the sensitivity to variations of link lengths and the location of the moving pivots of four-link mechanisms is investigated for the particular objective of three and four position synthesis. In the three design positions case, sensitivity maps with isosensitivity curves plotted in the design solution space allow the designer to synthesize a planar mechanism with desired sensitivity value or to optimize sensitivity from a set of acceptable design solutions. In the case of four design positions, segments of the Burmester design curves that exhibit specified sensitivity to link length tolerance are identified. A performance sensitivity criterion is used as a convenient and a useful way of discriminating between many possible solutions to a given synthesis problem.

scholarly journals Model-Based Reinforcement Learning for Closed-Loop Dynamic Control of Soft Robotic Manipulators

2019 ◽  
Vol 35 (1) ◽  
pp. 124-134 ◽  
Author(s):  
Thomas George Thuruthel ◽  
Egidio Falotico ◽  
Federico Renda ◽  
Cecilia Laschi
Keyword(s):  
Reinforcement Learning ◽  
Closed Loop ◽  
Dynamic Control ◽  
Robotic Manipulators ◽  
Model Based

scholarly journals Error Uncertainty Analysis in Planar Closed-Loop Structure with Joint Clearances

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1872
Author(s):  
Yushu Yu ◽  
Jinglin Li ◽  
Xin Li ◽  
Yi Yang
Keyword(s):  
Joint Distribution ◽  
Error Probability ◽  
Closed Loop ◽  
Open Loop ◽  
Distribution Functions ◽  
Positional Error ◽  
Loop Structure ◽  
Virtual Link ◽  
Joint Clearances ◽  
Probability Density Function Pdf

For planar closed-loop structures with clearances, the angular and positional error uncertainties are studied. By using the vector translation method and geometric method, the boundaries of the errors are analyzed. The joint clearance is considered as being distributed uniformly in a circle area. A virtual link projection method is proposed to deal with the clearance affected length error probability density function (PDF) for open-loop links. The error relationship between open loop and closed loop is established. The open-loop length PDF and the closed-loop angular error PDF both approach being Gaussian distribution if there are many clearances. The angular propagation error of multi-loop structures is also investigated by using convolution. The positional errors of single and multiple loops are both discussed as joint distribution functions. Monte Carlo simulations are conducted to verify the proposed methods.

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