scholarly journals Physician-Friendly Tool Center Point Calibration Method for Robot-Assisted Puncture Surgery

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 366
Author(s):  
Leifeng Zhang ◽  
Changle Li ◽  
Yilun Fan ◽  
Xuehe Zhang ◽  
Jie Zhao
Keyword(s):  
Vision System ◽  
Calibration Method ◽  
Robot Assisted ◽  
Precise Control ◽  
Time Consumption ◽  
Center Point ◽  
Calibration Methods ◽  
Key Factor ◽  
Tool Replacement ◽  
Robot Configuration

After each robot end tool replacement, tool center point (TCP) calibration must be performed to achieve precise control of the end tool. This process is also essential for robot-assisted puncture surgery. The purpose of this article is to solve the problems of poor accuracy stability and strong operational dependence in traditional TCP calibration methods and to propose a TCP calibration method that is more suitable for a physician. This paper designs a special binocular vision system and proposes a vision-based TCP calibration algorithm that simultaneously identifies tool center point position (TCPP) and tool center point frame (TCPF). An accuracy test experiment proves that the designed special binocular system has a positioning accuracy of ±0.05 mm. Experimental research shows that the magnitude of the robot configuration set is a key factor affecting the accuracy of TCPP. Accuracy of TCPF is not sensitive to the robot configuration set. Comparison experiments show that the proposed TCP calibration method reduces the time consumption by 82%, improves the accuracy of TCPP by 65% and improves the accuracy of TCPF by 52% compared to the traditional method. Therefore, the method proposed in this article has higher accuracy, better stability, less time consumption and less dependence on the operations than traditional methods, which has a positive effect on the clinical application of high-precision robot-assisted puncture surgery.

The Calibration Method of a stereo-Vision-Based Coordinates Measurement System via a Two-Axis Turntable--The Combination of Stereo Vision and Turntable

2021 ◽  
Vol 14 ◽  
Author(s):  
Zimiao Zhang ◽  
Zhiwu Wang ◽  
Shihai Zhang ◽  
Anqi Fu
Keyword(s):  
Stereo Vision ◽  
Measurement System ◽  
Vision System ◽  
Three Dimensional ◽  
Calibration Method ◽  
Measurement Range ◽  
Measurement Technology ◽  
Rotation Axes ◽  
Internal Parameters ◽  
Calibration Methods

Background: Stereo-vision-based three-dimensional coordinates measurement technology has been widely applied in the military or civil fields. There are two problems that need to be solved. The first problem is that each camera internal parameters and the two cameras external parameters need to be calibrated. To increase the measurement range, usually the turntable is used with the stereo vision system together. The second problem is the calibration of the turntable. Objective: The aim of the study is to construct and calibrate a stereo-vision-based coordinates measurement system via a two-axis turntable. Methods: Considering that the internal parameters of each camera do not change during the measurement process and the complicated optimization process of one-step self-calibration, a two-step stereo vision calibration method is proposed. In the first step, we calibrate the internal parameters of each camera through a specially designed planar target with circular points. In the second step, on the basis of the calibrated results of the internal parameters, the two cameras external parameters are calibrated through a simple target which could be distributed in the measurement volume. For the calibration of the two-axis turntable, we calibrated the rotation axes of the turntable and the coordinates of points in the 3D space could be measured considering the non-orthogonality of the axes. Results: Some experiments are provided to examine the calibration methods we proposed. They are the plane target measurement experiments, the standard ball center coordinates measurement experiments and target pose measurement experiments. Experiment results demonstrate the superiority of the calibration method we proposed. Conclusion: We studied the calibration methods of the stereo-vision-based coordinates measurement system via a two-axis turntable. The experimental results show the measurement accuracy of our system is less than 0.1mm.

Mesoscale Robotic Assembly With Orthogonal Optical Alignment for UV-LIGA Parts

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Xin Ye ◽  
Xiaofeng Zhang ◽  
Bile Wan ◽  
Zhijing Zhang ◽  
Pan Liu
Keyword(s):  
Vision System ◽  
Calibration Method ◽  
Robotic Assembly ◽  
Inertia Force ◽  
Success Rates ◽  
Time Consumption ◽  
Assembly Accuracy ◽  
Object Part ◽  
Optical Alignment ◽  
Causes Of Failure

This paper proposes an assembly system for ultraviolet-lithographie galvanik abformung (UV-LIGA) parts with a robotic manipulator. Both images of base part and object part could be obtained simultaneously from an in-house orthogonal optical alignment vision system. Two microgrippers were introduced to realize the reliable clamping. An initial calibration method was presented to ensure assembly accuracy. Assembly experiments were conducted with success rates of 80% and the time consumption of 20 min for all four parts assembly. Suspected causes of failure are motion mechanisms' uncertainty, part dislocation resulted from inertia force when microgripper is moving, and the error which is produced in the detection process because of random factors.

scholarly journals Research on Calibration Method of Binocular Vision System Based on Neural Network

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Hao Zhu ◽  
Mulan Wang ◽  
Weiye Xu
Keyword(s):  
Neural Network ◽  
Binocular Vision ◽  
Vision System ◽  
Calibration Method ◽  
Correction Method ◽  
Distortion Correction ◽  
Inspection System ◽  
Lens Distortion ◽  
Calibration Methods ◽  
Binocular Vision System

In binocular vision inspection system, the calibration of detection equipment is the basis to ensure the subsequent detection accuracy. The current calibration methods have the disadvantages of complex calculation, low precision, and poor operability. In order to solve the above problems, the calibration method of binocular camera, the correction method of lens distortion, and the calibration method of projector in the binocular vision system based on surface structured light are studied in this paper. For lens distortion correction, on the basis of analyzing the traditional correction methods, a distortion correction method based on radial basis function neural network is proposed. Using the excellent nonlinear mapping ability of RBF neural network, the distortion correction models of different lenses can be obtained quickly. It overcomes the defect that the traditional correction model cannot adjust adaptively with the type of lens. The experimental results show that the accuracy of the method can meet the requirements of system calibration.

scholarly journals A Multi Camera and Multi Laser Calibration Method for 3D Reconstruction of Revolution Parts

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 765
Author(s):  
Hugo Álvarez ◽  
Marcos Alonso ◽  
Jairo R. Sánchez ◽  
Alberto Izaguirre
Keyword(s):  
3D Reconstruction ◽  
Calibration Method ◽  
Laser Plane ◽  
Calibration Methods ◽  
Laser Calibration ◽  
Calibration Object ◽  
Focus Plane ◽  
Chessboard Pattern ◽  
Line Patterns

This paper describes a method for calibrating multi camera and multi laser 3D triangulation systems, particularly for those using Scheimpflug adapters. Under this configuration, the focus plane of the camera is located at the laser plane, making it difficult to use traditional calibration methods, such as chessboard pattern-based strategies. Our method uses a conical calibration object whose intersections with the laser planes generate stepped line patterns that can be used to calculate the camera-laser homographies. The calibration object has been designed to calibrate scanners for revolving surfaces, but it can be easily extended to linear setups. The experiments carried out show that the proposed system has a precision of 0.1 mm.

Stable Calibrations of Six-DOF Serial Robots by Using Identification Models with Equalized Singular Values

Robotica ◽  
2021 ◽  
pp. 1-22
Author(s):  
Zhouxiang Jiang ◽  
Min Huang
Keyword(s):  
Industrial Robot ◽  
Singular Values ◽  
Calibration Method ◽  
Identification Accuracy ◽  
Condition Numbers ◽  
Measurement Instruments ◽  
Unknown Parameters ◽  
Calibration Methods ◽  
Six Dof ◽  
The Stability

SUMMARY In typical calibration methods (kinematic or non-kinematic) for serial industrial robot, though measurement instruments with high resolutions are adopted, measurement configurations are optimized, and redundant parameters are eliminated from identification model, calibration accuracy is still limited under measurement noise. This might be because huge gaps still exist among the singular values of typical identification Jacobians, thereby causing the identification models ill conditioned. This paper addresses such problem by using new identification models established in two steps. First, the typical models are divided into the submodels with truncated singular values. In this way, the unknown parameters corresponding to the abnormal singular values are removed, thereby reducing the condition numbers of the new submodels. However, these models might still be ill conditioned. Therefore, the second step is to further centralize the singular values of each submodel by using a matrix balance method. Afterward, all submodels are well conditioned and obtain much higher observability indices compared with those of typical models. Simulation results indicate that significant improvements in the stability of identification results and the identifiability of unknown parameters are acquired by using the new identification submodels. Experimental results indicate that the proposed calibration method increases the identification accuracy without incurring additional hardware setup costs to the typical calibration method.

scholarly journals Vicarious Radiometric Calibration of Ocean Color Bands for FY-3D/MERSI-II at Lake Qinghai, China

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 139
Author(s):  
Shengli Chen ◽  
Xiaobing Zheng ◽  
Xin Li ◽  
Wei Wei ◽  
Shenda Du ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Large Deviation ◽  
Ocean Color ◽  
Calibration Method ◽  
Surface Measurement ◽  
Radiometric Calibration ◽  
Lake Qinghai ◽  
Vicarious Calibration ◽  
Calibration Methods ◽  
Spectral Imager

To calibrate the low signal response of the ocean color (OC) bands and test the stability of the Fengyun-3D (FY-3D)/Medium Resolution Spectral Imager II (MERSI-II), an absolute radiometric calibration field test of FY-3D/MERSI-II at the Lake Qinghai Radiometric Calibration Site (RCS) was carried out in August 2018. The lake surface and atmospheric parameters were mainly measured by advanced observation instruments, and the MODerate spectral resolution atmospheric TRANsmittance algorithm and computer model (MODTRAN4.0) was used to simulate the multiple scattering radiance value at the altitude of the sensor. The results showed that the relative deviations between bands 9 and 12 are within 5.0%, while the relative deviations of bands 8, and 13 are 17.1%, and 12.0%, respectively. The precision of the calibration method was verified by calibrating the Aqua/Moderate-resolution Imaging Spectroradiometer (MODIS) and National Polar-orbiting Partnership (NPP)/Visible Infrared Imaging Radiometer (VIIRS), and the deviation of the calibration results was evaluated with the results of the Dunhuang RCS calibration and lunar calibration. The results showed that the relative deviations of NPP/VIIRS were within 7.0%, and the relative deviations of Aqua/MODIS were within 4.1% from 400 nm to 600 nm. The comparisons of three on-orbit calibration methods indicated that band 8 exhibited a large attenuation after launch and the calibration results had good consistency at the other bands except for band 13. The uncertainty value of the whole calibration system was approximately 6.3%, and the uncertainty brought by the field surface measurement reached 5.4%, which might be the main reason for the relatively large deviation of band 13. This study verifies the feasibility of the vicarious calibration method at the Lake Qinghai RCS and provides the basis and reference for the subsequent on-orbit calibration of FY-3D/MERSI-II.

scholarly journals Cobot User Frame Calibration: Evaluation and Comparison between Positioning Repeatability Performances Achieved by Traditional and Vision-Based Methods

Robotics ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 45
Author(s):  
Roberto Pagani ◽  
Cristina Nuzzi ◽  
Marco Ghidelli ◽  
Alberto Borboni ◽  
Matteo Lancini ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Production Line ◽  
Calibration Method ◽  
Fiducial Marker ◽  
Positioning System ◽  
Local Calibration ◽  
Calibration Methods ◽  
Robot Positioning ◽  
Good Repeatability ◽  
Calibration Time

Since cobots are designed to be flexible, they are frequently repositioned to change the production line according to the needs; hence, their working area (user frame) needs to be often calibrated. Therefore, it is important to adopt a fast and intuitive user frame calibration method that allows even non-expert users to perform the procedure effectively, reducing the possible mistakes that may arise in such contexts. The aim of this work was to quantitatively assess the performance of different user frame calibration procedures in terms of accuracy, complexity, and calibration time, to allow a reliable choice of which calibration method to adopt and the number of calibration points to use, given the requirements of the specific application. This has been done by first analyzing the performances of a Rethink Robotics Sawyer robot built-in user frame calibration method (Robot Positioning System, RPS) based on the analysis of a fiducial marker distortion obtained from the image acquired by the wrist camera. This resulted in a quantitative analysis of the limitations of this approach that only computes local calibration planes, highlighting the reduction of performances observed. Hence, the analysis focused on the comparison between two traditional calibration methods involving rigid markers to determine the best number of calibration points to adopt to achieve good repeatability performances. The analysis shows that, among the three methods, the RPS one resulted in very poor repeatability performances (1.42 mm), while the three and five points calibration methods achieve lower values (0.33 mm and 0.12 mm, respectively) which are closer to the reference repeatability (0.08 mm). Moreover, comparing the overall calibration times achieved by the three methods, it is shown that, incrementing the number of calibration points to more than five, it is not suggested since it could lead to a plateau in the performances, while increasing the overall calibration time.

Easy calibration method of vision system for in-situ measurement of strain of thin films

2009 ◽  
Vol 19 ◽  
pp. s243-s249 ◽  
Author(s):  
Jun-Hyub PARK ◽  
Dong-Joong KANG ◽  
Myung-Soo SHIN ◽  
Sung-Jo LIM ◽  
Son-Cheol YU ◽  
...  
Keyword(s):  
Thin Films ◽  
Vision System ◽  
Calibration Method ◽  
In Situ Measurement

scholarly journals Extrinsic Parameters Calibration Method of Cameras with Non-Overlapping Fields of View in Airborne Remote Sensing

2018 ◽  
Vol 10 (8) ◽  
pp. 1298 ◽  
Author(s):  
Lei Yin ◽  
Xiangjun Wang ◽  
Yubo Ni ◽  
Kai Zhou ◽  
Jilong Zhang
Keyword(s):  
Remote Sensing ◽  
Camera Calibration ◽  
Calibration Method ◽  
Optimization Method ◽  
Airborne Remote Sensing ◽  
Camera System ◽  
Translation Error ◽  
Camera Systems ◽  
Calibration Methods ◽  
Extrinsic Parameters

Multi-camera systems are widely used in the fields of airborne remote sensing and unmanned aerial vehicle imaging. The measurement precision of these systems depends on the accuracy of the extrinsic parameters. Therefore, it is important to accurately calibrate the extrinsic parameters between the onboard cameras. Unlike conventional multi-camera calibration methods with a common field of view (FOV), multi-camera calibration without overlapping FOVs has certain difficulties. In this paper, we propose a calibration method for a multi-camera system without common FOVs, which is used on aero photogrammetry. First, the extrinsic parameters of any two cameras in a multi-camera system is calibrated, and the extrinsic matrix is optimized by the re-projection error. Then, the extrinsic parameters of each camera are unified to the system reference coordinate system by using the global optimization method. A simulation experiment and a physical verification experiment are designed for the theoretical arithmetic. The experimental results show that this method is operable. The rotation error angle of the camera’s extrinsic parameters is less than 0.001rad and the translation error is less than 0.08 mm.

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