scholarly journals Dynamic performance improvement of direct image-based visual servoing in contour following

2018 ◽  
Vol 15 (1) ◽  
pp. 172988141775385 ◽  
Author(s):  
Che-Liang Li ◽  
Ming-Yang Cheng ◽  
Wei-Che Chang
Keyword(s):  
Visual Servoing ◽  
Sliding Mode ◽  
Industrial Robots ◽  
Image Feature ◽  
Interaction Matrix ◽  
Feedback Signal ◽  
Depth Information ◽  
Parametric Curve ◽  
Contour Following ◽  
Velocity Command

Image-based visual servoing (IBVS) has increasingly gained popularity and has been adopted in applications such as industrial robots, quadrotors, and unmanned aerial vehicles. When exploiting IBVS, the image feature velocity command obtained from the visual loop controller is converted to the velocity command of the workspace through the interaction matrix so as to converge image feature error. However, issues such as the noise/disturbance arising from image processing and the smoothness of image feature command are often overlooked in the design of the visual loop controller, especially in a contour following task. In particular, noise in the image feature will contaminate the image feedback signal so that the visual loop performance can be substantially affected. To cope with the aforementioned problem, this article employs the sliding mode controller to suppress the adverse effects caused by image feature noise. Moreover, by exploiting the idea of motion planning, a parametric curve interpolator is developed to generate smooth image feature commands. In addition, a depth observer is also designed to provide the depth information essential in the implementation of the interaction matrix. In order to assess the feasibility of the proposed approach, a two-degrees-of-freedom planar robot that employs an IBVS structure and an eye-to-hand camera configuration is used to conduct a contour following task. Contour following results verify the effectiveness of the proposed approach.

scholarly journals Adaptive Visual Servoing Control for Hoisting Positioning Under Disturbance Condition

2020 ◽  
Vol 10 (7) ◽  
pp. 2562
Author(s):  
Shenghao Tong ◽  
Ke Zhang ◽  
Huaitao Shi ◽  
Jinbao Zhao ◽  
Jie Sun
Keyword(s):  
Control Algorithm ◽  
Visual Servoing ◽  
Sliding Mode ◽  
External Disturbance ◽  
Great Influence ◽  
Superior Performance ◽  
Adaptive Sliding Mode Control ◽  
Feedback Signal ◽  
Visual Servo ◽  
Visual Error

This paper proposes a visual servo scheme for hoisting positioning under disturbance conditions. In actual hoisting work, disturbances such as equipment and load vibration are inevitable, which brings challenges to the development of a visual servo for hoisting positioning. The main problems are as follows: (1) the correlation between visual error and disturbance is not considered or well resolved; (2) the disturbance has a great influence on the control stability, but it is difficult to model. At present, there is no detailed research on the above problems. In this paper, the visual error is defined by the image error of the feedback signal based on dynamic equations containing disturbances. An adaptive sliding mode control algorithm is employed to decrease the influence of external disturbance, and the coefficient of the slide surface is established based on the adaptive gain. In view of the belief that it is difficult to model disturbance terms, a nonlinear disturbance observer is introduced to obtain equivalent disturbance. On this basis, an adaptive control algorithm with disturbance compensation is proposed to improve the robustness of the visual servo system. We use Lyapunov’s method to analyze the stability conditions of the system. Compared with the other state-of-the-art methods, the simulation results show that our method has superior performance in convergence, accuracy, and restraining disturbance. Finally, the proposed algorithm is applied to the hoisting platform for experimental research, which proves the effectiveness of the controller.

Direct Interpretation of Dynamic Images and Camera Motion for Visual Servoing Without Image Feature Correspondence

1997 ◽  
Vol 9 (2) ◽  
pp. 104-110 ◽  
Author(s):  
Koichiro Deguchi ◽  
Keyword(s):  
Visual Servoing ◽  
General Scheme ◽  
Principal Component ◽  
Tangent Plane ◽  
Image Feature ◽  
Interaction Matrix ◽  
Normal Vector ◽  
Camera Motion ◽  
Robot Arm ◽  
Feature Correspondence

A general scheme to represent the relation between dynamic images and camera motion is presented. Then its application to visual servoing is proposed. For a specific object, every possible combination of the camera pose and the obtained image should be constrained on a lower dimensional hyper surface in the product space of the whole combination of image data and camera position. Visual servoing, for example, is interpreted as finding a path on this surface leading to a given image. Our approach is to analyze the properties of this surface, and use its differential or tangential property for visual servoing. The coefficient matrix of the tangent plane of this surface is related to the so-called Interaction Matrix. For this approach, the reduction of the dimension of the image information becomes a key problem. We propose to use the principal component analysis and to represent images with a composition of small number of ""eigenimages"" by using Karhune Loève (K-L) expansion. A normal vector We confirm the feasibility of our basic idea for visual servoing with some experiments using a real robot arm.

scholarly journals 2D Legendre Moments-Based Visual Control

2012 ◽  
Vol 162 ◽  
pp. 487-496 ◽  
Author(s):  
Aurelien Yeremou Tamtsia ◽  
Youcef Mezouar ◽  
Philippe Martinet ◽  
Haman Djalo ◽  
Emmanuel Tonye
Keyword(s):  
Visual Servoing ◽  
Dynamic Range ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Interaction Matrix ◽  
Geometric Moments ◽  
Control Scheme ◽  
Control Schemes ◽  
Legendre Moments ◽  
Set Of Points

Among region-based descriptors, geometric moments have been widely exploited to design visual servoing schemes. However, they present several disadvantages such as high sensitivity to noise measurement, high dynamic range and information redundancy (since they are not computed onto orthogonal basis). In this paper, we propose to use a class of orthogonal moments (namely Legendre moments) instead of geometric moments to improve the behavior of moment-based control schemes. The descriptive form of the interaction matrix related to the Legendre moments computed from a set of points is rst derived. Six visual features are then selected to design a partially-decoupled control scheme. Finally simulated and experimental results are presented to illustrate the validity of our proposal.

Synergistic real-time compensation of tracking and contouring errors for precise parametric curved contour following systems

2017 ◽  
Vol 232 (19) ◽  
pp. 3367-3383 ◽  
Author(s):  
De-Ning Song ◽  
Jian-Wei Ma ◽  
Zhen-Yuan Jia ◽  
Feng-Ze Qin ◽  
Xiao-Xuan Zhao
Keyword(s):  
Real Time ◽  
High Precision ◽  
Tracking Error ◽  
Estimation Algorithm ◽  
Computer Numerical Control ◽  
Numerical Control ◽  
System Structure ◽  
Parametric Curve ◽  
Contouring Error ◽  
Contour Following

The tracking and contouring errors are inevitable in real computer numerical control contour following because of the reasons such as servo delay and dynamics mismatch. In order to improve the motion accuracy, this paper proposes a synergistic real-time compensation method of tracking and contouring errors for precise parametric curve following of the computer numerical control systems. The tracking error for each individual axis is first compensated, by using the feed-drive models with the consideration of model uncertainties, to enhance the tracking performances of all axes. Further, the contouring error is estimated and compensated to improve the contour accuracy directly, where a high-precision contouring-error estimation algorithm, based on spatial circular approximation of the desired contour neighboring the actual motion position, is presented. Considering that the system structure is coupled after compensation, the stability of the coupled system is analyzed for design of the synergistic compensator. Innovative contributions of this study are that not only the contouring-error can be estimated with a high precision in real time, but also the tracking and contouring performances can be simultaneously improved although there exist modeling errors and disturbances. Simulation and experimental tests demonstrate the effectiveness and advantages of the proposed method.

scholarly journals Vision-Based Target Detection and Tracking for a Miniature Pan-Tilt Inertially Stabilized Platform

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2243
Author(s):  
Jianchuan Guo ◽  
Chenhu Yuan ◽  
Xu Zhang ◽  
Fan Chen
Keyword(s):  
Target Detection ◽  
Feedback Linearization ◽  
Visual Servoing ◽  
Control Method ◽  
Sliding Mode ◽  
Optical Axis ◽  
Detection And Tracking ◽  
The Stability ◽  
Stabilized Platform ◽  
The Mathematical Model

This paper presents a novel visual servoing sheme for a miniature pan-tilt intertially stabilized platform (ISP). A fully customized ISP can be mounted on a miniature quadcopter to achieve stationary or moving target detection and tracking. The airborne pan-tilt ISP can effectively isolate a disturbing rotational motion of the carrier, ensuring the stabilization of the optical axis of the camera in order to obtain a clear video image. Meanwhile, the ISP guarantees that the target is always on the optical axis of the camera, so as to achieve the target detection and tracking. The vision-based tracking control design adopts a cascaded control structure based on the mathematical model, which can accurately reflect the dynamic characteristics of the ISP. The inner loop of the proposed controller employs a proportional lag compensator to improve the stability of the optical axis, and the outer loop adopts the feedback linearization-based sliding mode control method to achieve the target tracking. Numerical simulations and laboratory experiments demonstrate that the proposed controller can achieve satisfactory tracking performance.

Second Order Sliding Mode Neural Network-Based Visual Servoing of Robot Hands With Fast Manipulation, Including Transition

2005 ◽  
Author(s):  
Rodolfo Garci´a-Rodri´guez ◽  
V. Parra-Vega ◽  
Francisco Rui´z-Sa´nchez
Keyword(s):  
Neural Network ◽  
Visual Servoing ◽  
Sliding Mode ◽  
Second Order ◽  
Constrained Motion ◽  
Unilateral Constraints ◽  
Robot Hands ◽  
Commuting Time ◽  
Algebraic Constraints ◽  
The Impact

Strictly speaking, transition tasks such as those executed by robot hands involve free, impact, and constrained motion regimes, with changing dynamics. Impulsive, unilateral constraints arises in the impact regime, which makes very difficult to design a control system. Moreover, algebraic constraints arise in the constrained regime. The trivial approach would be to avoid impact, and to commute consistently ODE- and DAE-based controller, or to impose virtual constraints to model as a DAE system all regimes. In any case, it is required to know exactly the commuting time. In this paper, a very simple control scheme is proposed based on avoiding impact regime, through zero transition velocity from free to constrained motion, therefore impulsive dynamics does not appear. This is possible because we guarantee exactly the time to commute with a novel well-posed finite time convergence scheme, to produce convergence toward any desired trajectory at any given arbitrarily time and for any initial condition. In this way, ODE and DAE dynamics/controllers commute stably. Inertial and gravitational forces are compensated by a recurrent neural network driven by image-based position and force tracking errors, with a decentralized structure for each robot. The network is tuned on line with a second order force-position sliding modes to finally guarantee exponential tracking.

Sign in / Sign up

Export Citation Format

Share Document