scholarly journals Improved Uncalibrated Visual Servo Strategy for Hyper-Redundant Manipulators in On-Orbit Automatic Assembly

2020 ◽  
Vol 10 (19) ◽  
pp. 6968
Author(s):  
Jinlin Gu ◽  
Mingchao Zhu ◽  
Lihua Cao ◽  
Ang Li ◽  
Wenrui Wang ◽  
...  
Keyword(s):  
Real Time ◽  
Variable Structure ◽  
Joint Space ◽  
Space Environment ◽  
Redundant Manipulators ◽  
Automatic Assembly ◽  
Visual Servo ◽  
Time Performance ◽  
Smooth Variable Structure Filter ◽  
First Time

Aiming at on-orbit automatic assembly, an improved uncalibrated visual servo strategy for hyper-redundant manipulators based on projective homography is proposed. This strategy uses an improved homography-based task function with lower dimensions while maintaining its robustness to image defects and noise. This not only improves the real-time performance but also makes the joint space of hyper-redundant manipulator redundant to the homography-based task function. Considering that the kinematic parameters of the manipulator are easily changed in a space environment, the total Jacobian between the task function and manipulator joints is estimated online and used to construct a controller to directly control the manipulator joints without a kinematics model. When designing the controller, the above-mentioned redundancy is exploited to solve the problem of the over-limiting of the joint angles of the manipulator. The KF-SVSF method, which combines the optimality of the Kalman filter (KF) and the robustness of the smooth variable structure filter (SVSF), is introduced to the field of uncalibrated visual servos for the first time to perform the online estimation of the total Jacobian. In addition, the singular value filtering (SVF) method is adopted for the first time to avoid the interference caused by the unstable condition number of the estimated total Jacobian. Finally, simulations and experiments verify the superiority of this strategy in terms of its real-time performance and precision.

The Application of Machine Vision in Automatic Assembly of Locks

2013 ◽  
Vol 646 ◽  
pp. 158-163
Author(s):  
Qing Min Liu ◽  
Cheng Zhang Gu ◽  
Zhi Kui Liu ◽  
Ling Zhao
Keyword(s):  
Machine Vision ◽  
Real Time ◽  
Production Efficiency ◽  
Assembly System ◽  
Automatic Assembly ◽  
Time Performance ◽  
System Requirements ◽  
The Difference ◽  
Assembly Precision

In the automatic assembly of locks system the pins’ selection depends on depth of key’s groove. Although the kinds of groove’s depth are fixed, the arrangements are random and they can’t be unpredictable. The difference in depth of key’s groove is very small, so it can’t be judged by eyes accurately. To solve the problem that the pins assembly is tried frequently, the depth of keys’ groove can be measured accurately by the machine vision. So the problem of the serious influence production efficiency is solved successfully. This kind lock is widely used and machine’s cost is very low by allocation. The experiments show that this method fully met the locks automatic assembly system requirements from the assembly precision, real time performance and robustness and other aspects, solving the problems encountered in the lock assembly.

The Design of Pneumatic Visual Servo Positioning System

2015 ◽  
Vol 752-753 ◽  
pp. 1000-1005
Author(s):  
Li Kai Zhu ◽  
Dean Zhao ◽  
Wei Ji ◽  
Yu Chen
Keyword(s):  
Real Time ◽  
Tracking Control ◽  
Vision System ◽  
Monocular Vision ◽  
Positioning System ◽  
Visual Servo ◽  
Time Performance ◽  
The Past ◽  
Center Position ◽  
Image Acquisition System

In view of the slowing expansion problem for the past harvesting robot’s electric push rod joint.This paper will adopt pneumatic draw stem instead of the original electric putter to improve the rapidity of servo system. Using VFW(Video for Windows) image acquisition system to access to the video buffer without generating the intermediate files,which can ensure high real-time performance. By monocular vision system to realize cylinder tracking control experiments for the fruit center position. Experiments verified the quickness and accuracy of the pneumatic servo positioning system.

scholarly journals Collision-Free Motion Planning of a Six-Link Manipulator Used in a Citrus Picking Robot

2021 ◽  
Vol 11 (23) ◽  
pp. 11336
Author(s):  
Zuoliang Tang ◽  
Lijia Xu ◽  
Yuchao Wang ◽  
Zhiliang Kang ◽  
Hong Xie
Keyword(s):  
Motion Planning ◽  
Real Time ◽  
Jacobian Matrix ◽  
Joint Space ◽  
Artificial Potential Field ◽  
The Novel ◽  
Native Defects ◽  
The Real ◽  
Time Performance ◽  
Planning Algorithm

This paper presents the results of a motion planning algorithm that has been used in an intelligent citrus-picking robot consisting of a six-link manipulator. The real-time performance of a motion planning algorithm is urgently required by the picking robot. Within the artificial potential field (APF) method, the motion planning of the picking manipulator was basically solved. However, the real-time requirement of the picking robot had not been totally satisfied by APF because of some native defects, such as the large number of calculations used to map forces into torques by the Jacobian matrix, local minimum trap, and target not reachable problem, which greatly reduce motion planning efficiency and real-time performance of citrus-picking robots. To circumvent those problems, this paper proposed some novel methods that improved the mathematical models of APF and directly calculates the attractive torques in the joint space. By using the latter approach, the calculation time and the total joint error were separately reduced by 54.89% and 45.41% compared with APF. Finally, the novel algorithm is presented and demonstrated with some illustrative examples of the citrus picking robot, both offline during the design phase as well as online during a realistic picking test.

scholarly journals Impact of High Coupling Factor in Absolute Distance Measurement with Self-Mixing Interferometry

Proceedings ◽  
2017 ◽  
Vol 1 (4) ◽  
pp. 373 ◽  
Author(s):  
Mengkoung Veng ◽  
Julien Perchoux ◽  
Francis Bony
Keyword(s):  
Real Time ◽  
Laser Frequency ◽  
Coupling Factor ◽  
Distance Measurement ◽  
Injection Current ◽  
Measurement Reliability ◽  
Absolute Distance ◽  
Time Performance ◽  
Coupling Factors ◽  
First Time

Absolute distance measurement by means of a self-mixing interferometer (SMI) can be obtained by modulating the laser frequency. This modulation is typically achieved through the modulation of the laser injection current with a triangle waveform. Various strategies have been proposed to increase the performances and recent researches have shown real-time performance of SMI with resolution reaching 100 μm for distances up to 2 m. In the present paper, we demonstrate for the first time, both experimentally and by modeling, that with high coupling factors between the laser and the target, disappearance of interferometric fringes occurs that can strongly affect the measurement reliability.

Probing the Dynamic Self-Assembly Behaviour of Photoswitchable Wormlike Micelles in Real Time

2018 ◽  
Author(s):  
Elaine A. Kelly ◽  
Judith E. Houston ◽  
Rachel Evans
Keyword(s):  
Real Time ◽  
Absorption Spectroscopy ◽  
Self Assembly ◽  
Uv Light ◽  
Wormlike Micelles ◽  
Tetraethylene Glycol ◽  
Light Illumination ◽  
First Time ◽  
Dependent Processes

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such as<i></i>drug delivery and micellar catalysis. Currently, their behaviour in the equilibrium <i>cis-</i>and <i>trans</i>-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, <a>tetraethylene glycol mono(4′,4-octyloxy,octyl-azobenzene) </a>(C<sub>8</sub>AzoOC<sub>8</sub>E<sub>4</sub>) using small-angle neutron scattering (SANS). We show that the incorporation of <i>in-situ</i>UV-Vis absorption spectroscopy with SANS allows the scattering profile, and hence micelle shape, to be correlated with the extent of photoisomerisation in real-time. It was observed that C<sub>8</sub>AzoOC<sub>8</sub>E<sub>4</sub>could switch between wormlike micelles (<i>trans</i>native state) and fractal aggregates (under UV light), with changes in the self-assembled structure arising concurrently with changes in the absorption spectrum. Wormlike micelles could be recovered within 60 seconds of blue light illumination. To the best of our knowledge, this is the first time the degree of AzoPS photoisomerisation has been tracked <i>in</i><i>-situ</i>through combined UV-Vis absorption spectroscopy-SANS measurements. This technique could be widely used to gain mechanistic and kinetic insights into light-dependent processes that are reliant on self-assembly.

Real-time Performance Monitoring of MPC Based on Covariance Index Prediction

2014 ◽  
Vol 39 (5) ◽  
pp. 658-663 ◽  
Author(s):  
Xue-Min TIAN ◽  
Ya-Jie SHI ◽  
Yu-Ping CAO
Keyword(s):  
Real Time ◽  
Performance Monitoring ◽  
Time Performance

Single Depth View Based Real-Time Reconstruction of Hand-Object Interactions

2021 ◽  
Vol 40 (3) ◽  
pp. 1-12
Author(s):  
Hao Zhang ◽  
Yuxiao Zhou ◽  
Yifei Tian ◽  
Jun-Hai Yong ◽  
Feng Xu
Keyword(s):  
Real Time ◽  
Synthetic Data ◽  
Real Data ◽  
Depth Image ◽  
Real Time System ◽  
The Real ◽  
Time Performance ◽  
Contact Constraint ◽  
Object Shapes ◽  
Object Interactions

Reconstructing hand-object interactions is a challenging task due to strong occlusions and complex motions. This article proposes a real-time system that uses a single depth stream to simultaneously reconstruct hand poses, object shape, and rigid/non-rigid motions. To achieve this, we first train a joint learning network to segment the hand and object in a depth image, and to predict the 3D keypoints of the hand. With most layers shared by the two tasks, computation cost is saved for the real-time performance. A hybrid dataset is constructed here to train the network with real data (to learn real-world distributions) and synthetic data (to cover variations of objects, motions, and viewpoints). Next, the depth of the two targets and the keypoints are used in a uniform optimization to reconstruct the interacting motions. Benefitting from a novel tangential contact constraint, the system not only solves the remaining ambiguities but also keeps the real-time performance. Experiments show that our system handles different hand and object shapes, various interactive motions, and moving cameras.

Sign in / Sign up

Export Citation Format

Share Document