A new methodology for joint stiffness identification of heavy duty industrial robots with the counterbalancing system

2018 ◽  
Vol 53 ◽  
pp. 58-71 ◽  
Author(s):  
Kun Yang ◽  
Wenyu Yang ◽  
Guangdong Cheng ◽  
Bingrong Lu
Keyword(s):  
Joint Stiffness ◽  
Industrial Robots ◽  
Heavy Duty ◽  
Stiffness Identification

scholarly journals Joint Stiffness Identification and Deformation Compensation of Serial Robots Based on Dual Quaternion Algebra

2018 ◽  
Vol 9 (1) ◽  
pp. 65 ◽  
Author(s):  
Guozhi Li ◽  
Fuhai Zhang ◽  
Yili Fu ◽  
Shuguo Wang
Keyword(s):  
Quaternion Algebra ◽  
Industrial Robot ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Identification Algorithm ◽  
Dual Quaternion ◽  
Compensation Algorithm ◽  
Serial Robots ◽  
Stiffness Identification ◽  
Deformation Compensation

As the application of industrial robots is limited by low stiffness that causes low precision, a joint stiffness identification algorithm for serial robots is presented. In addition, a deformation compensation algorithm is proposed for the accuracy improvement. Both of these algorithms are formulated by dual quaternion algebra, which offers a compact, efficient, and singularity-free way in robot analysis. The joint stiffness identification algorithm is derived from stiffness modeling, which is the combination of the principle of virtual work and dual quaternion algebra. To validate the effectiveness of the proposed identification algorithm and deformation compensation algorithm, an experiment was conducted on a dual arm industrial robot SDA5F. The robot performed a drilling operation during the experiment, and the forces and torques that acted on the end-effector (EE) of both arms were measured in order to apply the deformation compensation algorithm. The results of the experiment show that the proposed identification algorithm is able to identify the joint stiffness parameters of serial industrial robots, and the deformation compensation algorithm can improve the accuracy of the position and orientation of the EE. Furthermore, the performance of the forces and torques that acted on the EE during the operation were improved as well.

Joint Stiffness Identification and Flexibility Compensation of Articulated Industrial Robot

2013 ◽  
Vol 336-338 ◽  
pp. 1047-1052 ◽  
Author(s):  
Ya Lei Feng ◽  
Dao Kui Qu ◽  
Fang Xu ◽  
Hong Guang Wang
Keyword(s):  
Industrial Robot ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Absolute Position ◽  
Joint Flexibility ◽  
Position Accuracy ◽  
Stiffness Identification ◽  
Articulated Robots

Articulated robots are the most common industrial robots for their large workspace and flexibility. However, the existence of joint flexibility makes those robots difficult to achieve high absolute position accuracy. This paper presents a method to identify the joint stiffness of the robot. The basic idea of that method is to get joint stiffness based on Hooks Law through stepping movement of a single joint and calculating the corresponding joint gravity torque of every step. The practicality of that method is verified by experiment and a plan is carried out to compensate the joint flexibility.

Joint stiffness identification of industrial serial robots using 3D digital image correlation techniques

2021 ◽  
pp. 095440622110028
Author(s):  
Jianping Lin ◽  
Yongji Li ◽  
Yong Xie ◽  
Jiahao Hu ◽  
Junying Min
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Efficiency ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Image Correlation ◽  
Stiffness Identification ◽  
3D Digital Image Correlation ◽  
External Forces ◽  
Improved Accuracy

Industrial robots have been widely used in manufacturing for advantages of flexibility and high efficiency, while there exists a critical problem of low stiffness. Measuring the stiffnesses of joints accurately have a positive effect on optimizing the stiffness through compensation or posture adjustment. This study proposed a new method for stiffness identification of serial industrial robots using 3D digital image correlation (3D-DIC) techniques, which exhibits high accuracies. External forces are applied to the robot end and its 6-dimensional displacements are recorded with a 3D-DIC system. The values of joint stiffness are evaluated from the data of robot configurations, displacements and forces. The proposed method is implemented on the KUKA KR600-2830 robot experimentally and the average absolute value of relative error is 5.8%, which demonstrates that the proposed method provides much improved accuracy compared to the traditional method.

scholarly journals A Non-Delay Error Compensation Method for Dual-Driving Gantry-Type Machine Tool

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 748
Author(s):  
Qi Liu ◽  
Hong Lu ◽  
Xinbao Zhang ◽  
Yu Qiao ◽  
Qian Cheng ◽  
...  
Keyword(s):  
Machine Tool ◽  
Error Compensation ◽  
Prediction Method ◽  
Compensation Method ◽  
Industrial Robots ◽  
Numerical Control ◽  
Heavy Duty ◽  
Positioning Errors ◽  
Compensation Methods ◽  
Type Machine

The drive at the center of gravity (DCG) principle has been adopted in computer numerical control (CNC) machines and industrial robots that require heavy-duty and quick feeds. Using this principle requires accurate corrections of positioning errors. Conventional error compensation methods may cause vibrations and unstable control performances due to the delay between compensation and motor motion. This paper proposes a new method to reduce the positioning errors of the dual-driving gantry-type machine tool (DDGTMT), namely, a typical DCG-principle-based machine tool. An error prediction method is proposed to characterize errors online. An algorithm is proposed to quickly and accurately compensate the errors of the DDGTMT. Experiment results verify that the non-delay error compensation method proposed in this paper can effectively improve the accuracy of the DDGTMT.

scholarly journals Rotation-joint stiffness modeling for industrial robots considering contacts

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879306 ◽  
Author(s):  
Zhifeng Liu ◽  
Jingjing Xu ◽  
Qiang Cheng ◽  
Yongsheng Zhao ◽  
Yanhu Pei
Keyword(s):  
Fractal Theory ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Torsional Stiffness ◽  
Equivalent Stiffness ◽  
Force Analysis ◽  
Joint System ◽  
End Effector ◽  
Stiffness Modeling ◽  
High Speeds

Joint flexibility has a major impact on the motion accuracy of a robotic end effector, particularly at high speeds. This work proposes a technique of precisely modeling the torsional stiffness of the rotational joints for the industrial robots. This technique considers the contacts that exist in the joint system, which can have a significant effect on the overall joint stiffness. The torsional stiffness of the connections that commonly exist in the rotational joints, such as the belt connection, the connections using key, bolts, and pins, were modeled by combining the force analysis and the fractal theory. Through modeling the equivalent stiffness for the springs in serial and in parallel, the torsional stiffness of all joints for the ER3A-C60 robot were calculated and analyzed. The results show that the estimated stiffness based on the proposed technique is closer to the actual values than that based on the previous model without considering the contacts. The analysis is useful for controlling the dynamic characteristic of the industrial robots with the rotational joints while planning the trajectory for the end effector.

scholarly journals Joint stiffness identification of six-revolute industrial serial robots

2011 ◽  
Vol 27 (4) ◽  
pp. 881-888 ◽  
Author(s):  
Claire Dumas ◽  
Stéphane Caro ◽  
Sébastien Garnier ◽  
Benoît Furet
Keyword(s):  
Joint Stiffness ◽  
Serial Robots ◽  
Stiffness Identification

scholarly journals Variable stiffness identification and configuration optimization of industrial robots for machining tasks

2020 ◽  
Author(s):  
Jiachen Jiao ◽  
Wei Tian ◽  
Lin Zhang ◽  
Bo Li ◽  
Junshan Hu ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Optimization Methods ◽  
Optimization Method ◽  
Industrial Robots ◽  
Axial Stiffness ◽  
Configuration Optimization ◽  
Positional Accuracy ◽  
Stiffness Identification ◽  
Robot Stiffness ◽  
High Flexibility

Abstract Industrial robots are increasingly used in machining tasks because of their high flexibility and intelligence. However, the low structural stiffness of the robot seriously affects the positional accuracy and machining quality of robot operation equipment. Studying robot stiffness characteristics and optimization methods is an effective way to improve robot stiffness performance. Accordingly, aiming at the poor accuracy of stiffness modeling caused by approximating stiffness of each joint as constant, a variable stiffness identification method is proposed based on space gridding. Then, a task-oriented axial stiffness evaluation index is proposed to realize quantitative assessment of the stiffness performance in the machining direction. Besides, by analyzing the redundant kinematic characteristics of the robot machining system, a configuration optimization method is further come up with to maximize the index. For a large number of points or trajectory processing tasks, a configuration smoothing strategy is proposed to achieve fast acquisition of optimized configurations. Finally, experiments on a KR500 robot are conducted to verify the feasibility and validity of proposed stiffness identification and configuration optimization methods.

scholarly journals Joint stiffness identification of industrial serial robots

Robotica ◽  
2011 ◽  
Vol 30 (4) ◽  
pp. 649-659 ◽  
Author(s):  
Claire Dumas ◽  
Stéphane Caro ◽  
Mehdi Cherif ◽  
Sébastien Garnier ◽  
Benoît Furet
Keyword(s):  
Measurement Errors ◽  
Joint Stiffness ◽  
Experimental Tests ◽  
End Effector ◽  
Identification Method ◽  
Serial Robots ◽  
Stiffness Identification ◽  
Actuated Joints

SUMMARYThis paper presents a new methodology for the joint stiffness identification of industrial serial robots and as consequence for the evaluation of both translational and rotational displacements of the robot's end-effector subject to an external wrench (force and torque). In this paper, the robot's links are supposed to be quite stiffer than the actuated joints as it is usually the case with industrial serial robots. The robustness of the identification method and the sensitivity of the results to measurement errors, and the number of experimental tests are also analyzed. The Kuka KR240-2 robot is used as an illustrative example throughout the paper.

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