A speed measurement method for underwater robots using an artificial lateral line sensor

2021 ◽  
Author(s):  
Zhuoliang Zhang ◽  
Chao Zhou ◽  
Zhiqiang Cao ◽  
Min Tan ◽  
Long Cheng ◽  
...  
Keyword(s):  
Lateral Line ◽  
Swimming Speed ◽  
Filter Design ◽  
Absolute Error ◽  
Calibration Method ◽  
Underwater Robots ◽  
Speed Measurement ◽  
Cantilever Structure ◽  
Calibration Algorithm ◽  
Basic Parameters

Abstract Underwater robot technology has made considerable progress in recent years. However, due to the harsh environment and noise in the flow field near the underwater robots, it is difficult to measure some basic parameters, including swimming speed. The traditional speed measurement methods for underwater robots have the disadvantages of being limited by the environment and bulky. In order to overcome these shortcomings, an artificial lateral line sensor based on cantilever structure was developed in this paper. According to the deformation of cantilever beam under water impact, the swimming speed of underwater robots can be measured. In addition, an "end-to-end" calibration algorithm was proposed to calibrate the artificial lateral line sensor in the noisy environment, avoiding the complicated noise modeling and filter design process. To reduce the risk of overfitting, a hybrid loss function based on physical model was adopted. Compared with the classical calibration method, our method can reduce the error by 47.8%. Our sensor achieved an average absolute error of 0.07897 m/s, and can measure water speed up to 3 m/s.

Camera Calibration Method Based on Circle Plane Board

2013 ◽  
Vol 475-476 ◽  
pp. 184-187
Author(s):  
Wen Guo Li ◽  
Shao Jun Duan
Keyword(s):  
Camera Calibration ◽  
Calibration Method ◽  
Lens Distortion ◽  
Edge Extraction ◽  
Circle Plane ◽  
Circle Centre ◽  
Extraction Algorithm ◽  
Calibration Algorithm ◽  
Characteristic Points ◽  
Distortion Parameters

We present a camera calibration method based on circle plane board. The centres of circles on plane are regarded as the characteristic points, which are used to implement camera calibration. The proposed calibration is more accurate than many previous calibration algorithm because of the merit of the coordinate of circle centre being obtained from thousand of of edge pionts of ellipse, which is very reliable to image noise caused by edge extraction algorithm. Experiments shows the proposed algorithm can obtain high precise inner parameters, and lens distortion parameters.

Industrial part localization and grasping using a robotic arm guided by 2D monocular vision

2018 ◽  
Vol 45 (6) ◽  
pp. 794-804 ◽  
Author(s):  
Zhaohui Zheng ◽  
Yong Ma ◽  
Hong Zheng ◽  
Yu Gu ◽  
Mingyu Lin
Keyword(s):  
Camera Calibration ◽  
High Precision ◽  
Calibration Method ◽  
Monocular Vision ◽  
Robotic Arm ◽  
Robot Arm ◽  
Content Type ◽  
Calibration Algorithm ◽  
Target Locating ◽  
Practical Implications

Purpose The welding areas of the workpiece must be consistent with high precision to ensure the welding success during the welding of automobile parts. The purpose of this paper is to design an automatic high-precision locating and grasping system for robotic arm guided by 2D monocular vision to meet the requirements of automatic operation and high-precision welding. Design/methodology/approach A nonlinear multi-parallel surface calibration method based on adaptive k-segment master curve algorithm is proposed, which improves the efficiency of the traditional single camera calibration algorithm and accuracy of calibration. At the same time, the multi-dimension feature of target based on k-mean clustering constraint is proposed to improve the robustness and precision of registration. Findings A method of automatic locating and grasping based on 2D monocular vision is provided for robot arm, which includes camera calibration method and target locating method. Practical implications The system has been integrated into the welding robot of an automobile company in China. Originality/value A method of automatic locating and grasping based on 2D monocular vision is proposed, which makes the robot arm have automatic grasping function, and improves the efficiency and precision of automatic grasp of robot arm.

Camera Calibration Method Based on Halcon

2013 ◽  
Vol 385-386 ◽  
pp. 518-522
Author(s):  
Zhi Xian Zhang ◽  
Li Liang ◽  
Yong Deng
Keyword(s):  
Computer Vision ◽  
Camera Calibration ◽  
Ccd Camera ◽  
Calibration Method ◽  
Geometrical Model ◽  
Accuracy Analysis ◽  
Calibration Algorithm ◽  
Cross Platform ◽  
Computation Speed

Aiming at the applications of computer vision,a nonlinear image geometrical model for array CCD camera was build and the interior parameters and exterior parameters as well were analyzed.By applying Halcon calibration board with circular targets plane of matrix gridding type and functions library,a camera calibration algorithm and accuracy analysis were given.Experiments indicated that the parameters were accurate and this method is simple and it improves the calibration precision and computation speed, and has a good cross-platform portability.

Corrosion Evaluation in Dual Completions Using a Multifrequency Electromagnetic Tool

2021 ◽  
Author(s):  
Junwen Dai ◽  
Ahmed Elsayed Fouda
Keyword(s):  
Oil And Gas ◽  
Calibration Method ◽  
Inspection Time ◽  
Accurate Estimation ◽  
Well Completion ◽  
Pull Out ◽  
Calibration Algorithm ◽  
The Individual ◽  
Receiver Arrays ◽  
Production Tubing

Abstract Early detection of corrosion in well casings is of great importance to oil and gas well management. A typical well completion includes a production tubing inside a number of nested casings, which provide necessary well integrity and environmental protections. A multifrequency electromagnetic pipe inspection tool with multiple transmitter and receiver arrays was designed to accurately estimate the individual wall thicknesses of up to five nested pipes. The tool uses an axis-symmetric forward model to invert for wall thicknesses, among other pipe parameters. However, in cases where production occurs from two or more segregated zones, the well is generally equipped with more than one production tubing, which breaks the axial symmetry. In this paper, we show how the tool can further be employed to inspect the integrity of non-nested tubulars, such as dual completions. The performance of the tool is demonstrated using a full-scale yard mockup with known defects. A data-processing workflow, including multizone calibration and model-based inversion, is proposed to estimate the tubulars electrical conductivity, magnetic permeability, wall thickness, and eccentricity. An in-situ, multizone calibration method is applied to remove adjacent tubings influence, thus enabling accurate estimation of the thickness of outer casings without having to pull out the production tubing. In order to demonstrate the capabilities of the tool in wells with dual completions, a log was run in a 150 ft-long yard mockup with two strings of 2⅞ inch. tubing, two outer casing strings, and four different man-made defects on the casings. The tool is logged inside each of the tubing strings, and the two logs are inverted for the thickness and eccentricity of the tubing as well as the thickness of outer casings. Results from the yard test reveal that when the tool is logged in one tubing, it can accurately detect various kinds of defects on outer casings, even in the presence of a second tubing. The interference from the second tubing is shown to be minimal due to the employed calibration algorithm. A high degree of consistency is seen between the logs run in each tubing string. This suggests that if the goal is solely to monitor corrosion in the outer casings, it suffices to run the tool in only one of the tubing strings, further cutting nonproductive time. The techniques presented here enable pipe integrity monitoring without pulling the production tubings; tubings, therefore, minimizing inspection time and cost. The information provided by this tool can significantly improve the efficiency of well intervention operations, especially in areas with high corrosion rates.

scholarly journals Charuco Board-Based Omnidirectional Camera Calibration Method

Electronics ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 421 ◽  
Author(s):  
Gwon An ◽  
Siyeong Lee ◽  
Min-Woo Seo ◽  
Kugjin Yun ◽  
Won-Sik Cheong ◽  
...  
Keyword(s):  
Camera Calibration ◽  
Mean Absolute Error ◽  
Three Dimensional ◽  
Absolute Error ◽  
Calibration Method ◽  
Feature Points ◽  
Omnidirectional Camera ◽  
Reprojection Error ◽  
Conventional Methods ◽  
Better Than

In this paper, we propose a Charuco board-based omnidirectional camera calibration method to solve the problem of conventional methods requiring overly complicated calibration procedures. Specifically, the proposed method can easily and precisely provide two-dimensional and three-dimensional coordinates of patterned feature points by arranging the omnidirectional camera in the Charuco board-based cube structure. Then, using the coordinate information of the feature points, an intrinsic calibration of each camera constituting the omnidirectional camera can be performed by estimating the perspective projection matrix. Furthermore, without an additional calibration structure, an extrinsic calibration of each camera can be performed, even though only part of the calibration structure is included in the captured image. Compared to conventional methods, the proposed method exhibits increased reliability, because it does not require additional adjustments to the mirror angle or the positions of several pattern boards. Moreover, the proposed method calibrates independently, regardless of the number of cameras comprising the omnidirectional camera or the camera rig structure. In the experimental results, for the intrinsic parameters, the proposed method yielded an average reprojection error of 0.37 pixels, which was better than that of conventional methods. For the extrinsic parameters, the proposed method had a mean absolute error of 0.90° for rotation displacement and a mean absolute error of 1.32 mm for translation displacement.

Estimates of pressure differences across the head of a swimming clupeid fish

1993 ◽  
Vol 341 (1296) ◽  
pp. 129-140 ◽  
Keyword(s):  
Boundary Layer ◽  
Lateral Line ◽  
Swimming Speed ◽  
Pressure Difference ◽  
Preceding Paper ◽  
Feedback Signal ◽  
Effective Pressure ◽  
Active Mechanism ◽  
Angle Of Yaw ◽  
Yaw Angle

This paper is concerned to estimate, for a regularly swimming clupeid fish, the effective pressure difference that drives those motions in the subcerebral canal which can stim ulate the lateral-line neuromasts (see the preceding paper by D enton & G ray 1993). H ydrodynam ic analysis indicates that pure sideslip of the head (at observed sideslip velocities) would generate a pressure difference so great that the neuromasts would be saturated; however, sim ultaneous yaw ing can enormously reduce the effective pressure difference. For this purpose the angle of yaw would need to be kept in phase with sideslip velocity, with a m agnitude only a little less than the ratio of sideslip velocity to swimming speed, m aking the ‘crossflow’ of w ater across the yawed head small. These moreover are conditions which tend to avoid any serious distortions of the boundary layer on the fish’s surface by ‘crossflow’, such as are known from other evidence to increase significantly the resistance to the fish’s motion. It is noted that the lateral-line sensors would provide an appropriate feedback signal into a possible system for controlling yaw by oscillatory neck deflections so as to minimise the effective pressure difference and any associated crossflow effects. It is suggested that swimming clupeid fishes m ay use such an ‘active’ mechanism for reduction of hydrodynam ic resistance. The same ratio (around 0.87) of yaw angle times swimming speed to sideslip velocity is estimated: (i) to annul the signal sensed by lateral-line neuromasts; and (ii) to remove crossflow in the boundary layer over the head. The succeeding paper (Rowe et al. 1993) gives evidence, both that yaw is kept in phase with sideslip velocity, and that the above ratio (see their figure 4) remains close to 0.87, in a swimming herring.

scholarly journals A Novel Calibration Algorithm for Cable-Driven Parallel Robots with Application to Rehabilitation

2019 ◽  
Vol 9 (11) ◽  
pp. 2182 ◽  
Author(s):  
Han Yuan ◽  
Xianghui You ◽  
Yongqing Zhang ◽  
Wenjing Zhang ◽  
Wenfu Xu
Keyword(s):  
Calibration Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Human Robot Interaction ◽  
Automatic Calibration ◽  
Unknown Parameters ◽  
Robot Interaction ◽  
Geometric Calibration ◽  
Rehabilitation Robots ◽  
Calibration Algorithm

Cable-driven parallel robots are suitable candidates for rehabilitation due to their intrinsic flexibility and adaptability, especially considering the safety of human–robot interaction. However, there are still some challenges to apply cable-driven parallel robots to rehabilitation, one of which is the geometric calibration. This paper proposes a new automatic calibration method that is applicable for cable-driven parallel rehabilitation robots. The key point of this method is to establish the mapping between the unknown parameters to be calibrated and the parameters that could be measured by the inner sensors and then use least squares algorithm to find the solutions. Specifically, the unknown parameters herein are the coordinates of the attachment points, and the measured parameters are the lengths of the redundant cables. Simulations are performed on a 3-DOF parallel robot driven by four cables for validation. Results show that the proposed calibration method could precisely find the real coordinate values of the attachment points, with errors less than 10 − 12 mm. Trajectory simulations also indicate that the positioning accuracy of the cable-driven parallel robot (CDPR) could be greatly improved after calibration using the proposed method.

scholarly journals Intelligent Calibration of a Heavy-Duty Mechanical Arm in Coal Mine

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1186
Author(s):  
Yunhong Jia ◽  
Xiaodong Zhang ◽  
Zhenchong Wang ◽  
Wei Wang
Keyword(s):  
Extreme Learning Machine ◽  
Coal Mine ◽  
Absolute Error ◽  
Calibration Method ◽  
Heavy Duty ◽  
Maximum Absolute Error ◽  
Positioning Accuracy ◽  
Positioning Errors ◽  
Roof Bolter ◽  
Learning Machine

Accurate positioning of an airborne heavy-duty mechanical arm in coal mine, such as a roof bolter, is important for the efficiency and safety of coal mining. Its positioning accuracy is affected not only by geometric errors but also by nongeometric errors such as link and joint compliance. In this paper, a novel calibration method based on error limited genetic algorithm (ELGA) and regularized extreme learning machine (RELM) is proposed to improve the positioning accuracy of a roof bolter. To achieve the improvement, the ELGA is firstly implemented to identify the geometric parameters of the roof bolter’s kinematics model. Then, the residual positioning errors caused by nongeometric facts are compensated with the regularized extreme learning machine (RELM) network. Experiments were carried out to validate the proposed calibration method. The experimental results show that the root mean square error (RMSE) and the mean absolute error (MAE) between the actual mast end position and the nominal mast end position are reduced by more than 78.23%. It also shows the maximum absolute error (MAXE) between the actual mast end position and the nominal mast end position is reduced by more than 58.72% in the three directions of Cartesian coordinate system.

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