scholarly journals Kinematic Modeling of Six-Axis Industrial Robot and its Parameter Identification: A Tutorial

2021 ◽  
Vol 15 (5) ◽  
pp. 599-610
Author(s):  
Md. Moktadir Alam ◽  
◽  
Soichi Ibaraki ◽  
Koki Fukuda
Keyword(s):  
Present Model ◽  
Industrial Robot ◽  
Local Coordinate System ◽  
Kinematic Model ◽  
Kinematic Modeling ◽  
Positioning Accuracy ◽  
Rotary Axis ◽  
Model Based ◽  
Absolute Positioning ◽  
The Absolute

In advanced industrial applications, like machining, the absolute positioning accuracy of a six-axis robot is indispensable. To improve the absolute positioning accuracy of an industrial robot, numerical compensation based on positioning error prediction by the Denavit and Hartenberg (D-H) model has been investigated extensively. The main objective of this study is to review the kinematic modeling theory for a six-axis industrial robot. In the form of a tutorial, this paper defines a local coordinate system based on the position and orientation of the rotary axis average lines, as well as the derivation of the kinematic model based on the coordinate transformation theory. Although the present model is equivalent to the classical D-H model, this study shows that a different kinematic model can be derived using a different definition of the local coordinate systems. Subsequently, an algorithm is presented to identify the error sources included in the kinematic model based on a set of measured end-effector positions. The identification of the classical D-H parameters indicates a practical engineering application of the kinematic model for improving a robot’s positioning accuracy. Furthermore, this paper presents an extension of the present model, including the angular positioning deviation of each rotary axis. The angular positioning deviation of each rotary axis is formed as a function of the axis’ command angles and the direction of its rotation to model the effect of the rotary axis backlash. The identification of the angular positioning deviation of each rotary axis and its numerical compensation are presented, along with their experimental demonstration. This paper provides an essential theoretical basis for the error source diagnosis and error compensation of a six-axis robot.

Calibration and Compensation of Rotary Axis Angular Positioning Deviations on a SCARA-Type Industrial Robot Using a Laser Tracker

2020 ◽  
Author(s):  
Nan Zhao ◽  
Soichi Ibaraki
Keyword(s):  
Rotation Axis ◽  
Industrial Robot ◽  
Kinematic Model ◽  
Industrial Robots ◽  
Laser Tracker ◽  
Link Length ◽  
Positional Accuracy ◽  
Positioning Accuracy ◽  
Rotary Axis ◽  
The Absolute

Abstract In general, the “absolute” positioning accuracy of industrial robots is significantly lower than its repeatability. In the past research, in order to improve a robot’s positioning accuracy over the entire workspace, the compensation for the link length errors and the rotation axis angle offsets are often employed. However, the positioning error of the compensated industrial robot is still much higher than that of a typical machine tool. The purpose of this study is to propose a new kinematic model and its calibration scheme to further improve the absolute positional accuracy of an industrial robot over the entire workspace. In order to simplify the problem, this study only targets the 2D positioning accuracy of a SCARA-type robot. The proposed model includes not only link length errors and rotary axis angular offsets but also the “error map” of the angular positioning deviation of each rotary axis. The angular error deviation of each rotary axis is identified by measuring the robot’s end-effector position by a laser tracker at many positions. To verify the validity of the identified model, the effectiveness of the compensation based on it is also investigated.

scholarly journals Absolute Positioning Accuracy Improvement in an Industrial Robot

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4354 ◽  
Author(s):  
Yizhou Jiang ◽  
Liandong Yu ◽  
Huakun Jia ◽  
Huining Zhao ◽  
Haojie Xia
Keyword(s):  
Differential Evolution ◽  
Industrial Robot ◽  
Differential Evolution Algorithm ◽  
Substantial Improvement ◽  
Positioning Accuracy ◽  
Absolute Positioning ◽  
Calibration Methods ◽  
The Absolute ◽  
Six Degree Of Freedom ◽  
Kinematic Errors

The absolute positioning accuracy of a robot is an important specification that determines its performance, but it is affected by several error sources. Typical calibration methods only consider kinematic errors and neglect complex non-kinematic errors, thus limiting the absolute positioning accuracy. To further improve the absolute positioning accuracy, we propose an artificial neural network optimized by the differential evolution algorithm. Specifically, the structure and parameters of the network are iteratively updated by differential evolution to improve both accuracy and efficiency. Then, the absolute positioning deviation caused by kinematic and non-kinematic errors is compensated using the trained network. To verify the performance of the proposed network, the simulations and experiments are conducted using a six-degree-of-freedom robot and a laser tracker. The robot average positioning accuracy improved from 0.8497 mm before calibration to 0.0490 mm. The results demonstrate the substantial improvement in the absolute positioning accuracy achieved by the proposed network on an industrial robot.

scholarly journals Improvement and Assessment of the Absolute Positioning Accuracy of Chinese High-Resolution SAR Satellites

2019 ◽  
Vol 11 (12) ◽  
pp. 1465
Author(s):  
Deng ◽  
Zhang ◽  
Cai ◽  
Xu ◽  
Zhao ◽  
...  
Keyword(s):  
High Resolution ◽  
Propagation Delay ◽  
Reference Points ◽  
Calibration Model ◽  
Land Resource ◽  
Positioning Accuracy ◽  
Geometric Calibration ◽  
Atmospheric Propagation ◽  
Absolute Positioning ◽  
The Absolute

In recent years, China has launched YaoGan-13 and GaoFen-3, high-resolution synthetic aperture radar (SAR) satellites that can acquire global high-resolution images. The absolute positioning accuracy of such satellites is important for mapping areas without ground reference points and for automated processing. However, satellites without geometric calibration have poor absolute positioning accuracy, greatly restricting their application (e.g., land resource surveys). Therefore, they cannot meet national demands for high-resolution SAR images with good geometric accuracy. Here, we propose a series of methods to improve the absolute positioning accuracy of YaoGan-13 and GaoFen-3, such as the multiple-image combined calibration strategy and geometric calibration model for a real continuously moving configuration, including consideration of atmospheric propagation delay. Using high-accuracy ground control data collected from different areas, the 2-D and 3-D absolute positioning accuracies of YaoGan-13 and GaoFen-3 were assessed after implementation of the improvement measures. Experimental results showed that, after calibration, the 2-D absolute positioning accuracy of YaoGan-13 and GaoFen-3 are improved from 43.86 m to 2.57 m and from 30.34 m to 4.29 m, respectively. In addition, the 3-D absolute positioning accuracies of YaoGan-13 in plane and elevation are 3.21 m and 2.22 m, respectively. Improving the absolute positioning accuracy of these satellites could broaden the scope of their potential applications in the future.

scholarly journals Compensation for absolute positioning error of industrial robot considering the optimized measurement space

2020 ◽  
Vol 17 (2) ◽  
pp. 172988142092164
Author(s):  
Junde Qi ◽  
Bing Chen ◽  
Dinghua Zhang
Keyword(s):  
Industrial Robot ◽  
Measurement Data ◽  
Joint Space ◽  
Industrial Robots ◽  
Positioning Error ◽  
Positioning Accuracy ◽  
Decoupling Method ◽  
Absolute Positioning ◽  
Motion Characteristics ◽  
High Flexibility

Industrial robots are getting widely applied due to their low use-cost and high flexibility. However, the low absolute positioning accuracy limits their expansion in the area of high-precision manufacturing. Aiming to improve the positioning accuracy, a compensation method for the positioning error is put forward in terms of the optimization of the experimental measurement space and accurate modelling of the positioning error. Firstly, the influence of robot kinematic performance on the measurement accuracy is analysed, and a quantitative index describing the performance is adopted. On this basis and combined with the joints motion characteristics, the optimized measurement space in joint space as well as Cartesian space is obtained respectively, which can provide accurate measurement data to the error model. Then the overall model of the positioning error is constructed based on modified Denavit–Hartenberg method, in which the geometric errors and compliance errors are considered comprehensively, and an error decoupling method between them is carried out based on the error-feature analyses. Experiments on the KUKA KR210 robot are carried out finally. The mean absolute positioning accuracy of the robot increases from 1.179 mm to 0.093 mm, which verifies the effectiveness of the compensation methodology in this article.

scholarly journals A calibration method of robot kinematic parameters by drawstring displacement sensor

2019 ◽  
Vol 16 (5) ◽  
pp. 172988141988307 ◽  
Author(s):  
Yahui Gan ◽  
Jinjun Duan ◽  
Xianzhong Dai
Keyword(s):  
Calibration Method ◽  
Industrial Robots ◽  
Displacement Sensor ◽  
Kinematic Parameters ◽  
Position Measurement ◽  
Positioning Accuracy ◽  
End Effector ◽  
Displacement Sensors ◽  
Absolute Positioning ◽  
The Absolute

Calibration of robot kinematic parameters can effectively improve the absolute positioning accuracy of the end-effector for industrial robots. This article proposes a calibration method for robot kinematic parameters based on the drawstring displacement sensor. Firstly, the kinematic error model for articulated robot is established. Based on such a model, the position measurement system consisting of four drawstring displacement sensors is used to measure the actual position of the robot end-effector. Then, the deviation of the kinematic parameters of the robot is identified by the least-squares method according to robot end-effector deviations. The Cartesian space compensation method is adopted to improve the absolute positioning accuracy of the robot end-effecter. By experiments on the EFORT ER3A robot, the absolute positioning accuracy of the robot is significantly improved after calibration, which shows the effectiveness of the proposed method.

A distance error based industrial robot kinematic calibration method

2014 ◽  
Vol 41 (5) ◽  
pp. 439-446 ◽  
Author(s):  
Wang Zhenhua ◽  
Xu Hui ◽  
Chen Guodong ◽  
Sun Rongchuan ◽  
Lining Sun
Keyword(s):  
Industrial Robot ◽  
Calibration Method ◽  
Calibration Model ◽  
Kinematic Calibration ◽  
Absolute Position ◽  
Positioning Accuracy ◽  
Content Type ◽  
Distance Error ◽  
Position Accuracy ◽  
The Absolute

Purpose – The purpose of this paper is to present a distance accuracy-based industrial robot kinematic calibration model. Nowadays, the repeatability of the industrial robot is high, while the absolute positioning accuracy and distance accuracy are low. Many factors affect the absolute positioning accuracy and distance accuracy, and the calibration method of the industrial robot is an important factor. When the traditional calibration methods are applied on the industrial robot, the accumulative error will be involved according to the transformation between the measurement coordinate and the robot base coordinate. Design/methodology/approach – In this manuscript, a distance accuracy-based industrial robot kinematic calibration model is proposed. First, a simplified kinematic model of the robot by using the modified Denavit–Hartenberg (MDH) method is introduced, then the proposed distance error-based calibration model is presented; the experiment is set up in the next section. Findings – The experimental results show that the proposed calibration model based on MDH and distance error can improve the distance accuracy and absolute position accuracy dramatically. Originality/value – The proposed calibration model based on MDH and distance error can improve the distance accuracy and absolute position accuracy dramatically.

Kinematic Modeling for a 6-DOF Industrial Robot

2012 ◽  
Vol 590 ◽  
pp. 471-474 ◽  
Author(s):  
Guan Bin Gao ◽  
Jian Lu ◽  
Jian Jun Zhou
Keyword(s):  
Motion Control ◽  
Structural Characteristics ◽  
Industrial Robot ◽  
Structural Parameters ◽  
Kinematic Model ◽  
Great Influence ◽  
Robot Motion ◽  
Coordinate Systems ◽  
Kinematic Modeling ◽  
Position And Orientation

The kinematic model of robots is to describe the nonlinear relationship between the displacement of joints and the position and orientation of the end-effector, which is an important part of robotics. Kinematic model has great influence on the robot’s accuracy and motion control. In this paper, we studied the robot’s kinematic modeling methods and analyzed the characteristics and singularity of traditional DH method. By analyzing and comparing the structural characteristics of a 6-DOF industrial robot a MDH method was chosen to establish kinematic model. From the kinematic model the joint coordinate systems, structural parameters and homogeneous transformation matrixes of the robot are obtained. The kinematic model provides a theoretical basis for the robot motion control, calibration and error compensation.

Research on Absolute Positioning Error of Robot Based on Mapping Theory

2014 ◽  
Vol 494-495 ◽  
pp. 1156-1160
Author(s):  
Guan Hua Dong ◽  
Ying Yin ◽  
Xiao Bing Hu
Keyword(s):  
Industrial Robots ◽  
Positioning Error ◽  
Positioning Accuracy ◽  
Compensation Algorithm ◽  
Absolute Positioning ◽  
The Absolute ◽  
Mapping Theory

Joint-typical Industrial robots tend to have higher repetitive positioning accuracy and lower absolute positioning accuracy. In order to improve the absolute positioning accuracy of robots, this paper puts forward a compensation algorithm based on the mapping theory combining with the kinematics equation, which establish the connection between the space of off-line programming and teaching-programming, so as to approximate the repeat positioning accuracy. A experiment is implemented to confirm its correctness, and the result shows that the supposed method can improve the absolute positioning accuracy heavily, which the absolute positioning error reduces from 8.32mm to 1.08mm.

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