A Novel Automatic Calibration Method for Displacement Sensors Based on the Spatial Transformation Theory*

High precision position control is essential in the process of parts manufacturing and assembling, where eddy current displacement sensors (ECDSs) are widely used owing to the advantages of non-contact sensing, compact volume, and resistance to harsh conditions. To solve the nonlinear characteristics of the sensors, a high-accuracy calibration method based on linearity adjustment is proposed for ECDSs in this paper, which markedly improves the calibration accuracy and then the measurement accuracy. After matching the displacement value and the output voltage of the sensors, firstly, the sensitivity is adjusted according to the specified output range. Then, the weighted support vector adjustment models with the optimal weight of the zero-scale, mid-scale and full-scale are established respectively to cyclically adjust the linearity of the output characteristic curve. Finally, the final linearity adjustment model is obtained, and both the calibration accuracy and precision are verified by the established calibration system. Experimental results show that the linearity of the output characteristic curve of ECDS adjusted by the calibration method reaches over 99.9%, increasing by 1.9–5.0% more than the one of the original. In addition, the measurement accuracy improves from 11–25 μ m to 1–10 μ m in the range of 6mm, which provides a reliable guarantee for high accuracy displacement measurement.

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A Normal Sensor Calibration Method Based on an Extended Kalman Filter for Robotic Drilling

Sensors ◽

10.3390/s18103485 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3485 ◽

Cited By ~ 4

Author(s):

Dongdong Chen ◽

Peijiang Yuan ◽

Tianmiao Wang ◽

Ying Cai ◽

Haiyang Tang

Keyword(s):

Kalman Filter ◽

Laser Beam ◽

Extended Kalman Filter ◽

Zero Point ◽

Calibration Method ◽

Sensor Calibration ◽

Beam Direction ◽

Displacement Sensors ◽

Robotic Drilling ◽

Drilling System

To enhance the perpendicularity accuracy in the robotic drilling system, a normal sensor calibration method is proposed to identify the errors of the zero point and laser beam direction of laser displacement sensors simultaneously. The procedure of normal adjustment of the robotic drilling system is introduced firstly. Next the measurement model of the zero point and laser beam direction on a datum plane is constructed based on the principle of the distance measurement for laser displacement sensors. An extended Kalman filter algorithm is used to identify the sensor errors. Then the surface normal measurement and attitude adjustments are presented to ensure that the axis of the drill bit coincides with the normal at drilling point. Finally, simulations are conducted to study the performance of the proposed calibration method and experiments are carried out on a robotic drilling system. The simulation and experimental results show that the perpendicularity of the hole is within 0.2°. They also demonstrate that the proposed calibration method has high accuracy of parameter identification and lays a basis for high-precision perpendicularity accuracy of drilling in the robotic drilling system.

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Consistent Calibration of VIRR Reflective Solar Channels Onboard FY-3A, FY-3B, and FY-3C Using a Multisite Calibration Method

Remote Sensing ◽

10.3390/rs10091336 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1336 ◽

Cited By ~ 4

Author(s):

Ling Wang ◽

Xiuqing Hu ◽

Lin Chen ◽

Lingli He

Keyword(s):

Radiative Transfer ◽

Calibration Method ◽

Daily Basis ◽

Current Approach ◽

Automatic Calibration ◽

Vicarious Calibration ◽

Radiative Transfer Modeling ◽

Reflectance Data ◽

Calibration Coefficients

The FengYun-3 (FY-3) Visible Infrared Radiometer (VIRR), along with its predecessor, the Multispectral Visible Infrared Scanning Radiometer (MVISR), onboard the FY-1C and FY-1D, has collected continuous daily global observations for 18 years. Achieving accurate and consistent calibration for VIRR reflective solar bands (RSBs) has been challenging, as there is no onboard calibrator and the frequency of in situ vicarious calibration is limited. In this study, a new set of reflectance calibration coefficients were derived for RSBs of the FY-3A, FY-3B, and FY-3C VIRRs using a multisite (MST) calibration method. This method is an extension of a previous MST calibration method, which relies on radiative transfer modeling over the multiple stable earth sites, and no synchronous in situ measurements are needed; hence, it can be used to update the VIRR calibration on a daily basis. The on-orbit radiometric changes of the VIRR onboard the FY-3 series were assessed based on analyses of new sets of calibration slopes. Then, all recalibrated VIRR reflectance data over Libya 4, the most frequently used stable Earth site, were compared with those provided from the Level 1B (L1B) product. Additional validation was performed by comparing the recalibrated VIRR data with those derived from radiative transfer simulations using measurements from automatic calibration instruments in Dunhuang. The results indicate that the radiometric response changes of the VIRRs onboard FY-3A and FY-3B were larger than those of FY-3C VIRR and were wavelength dependent. The current approach can provide consistent VIRR reflectances across different FY-3 satellite platforms. After recalibration, differences in top-of-atmosphere (TOA) reflectance data across different VIRRs during the whole lifetime decreased from 5–10% to less than 3%. The comparison with the automatic calibration method indicates that MST calibration shows good accuracy and lower temporal oscillations.

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The Design of HTG Automatic Calibration System Based on Fuzzy Theory

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.468-471.1490 ◽

2012 ◽

Vol 468-471 ◽

pp. 1490-1494

Author(s):

Qi Ren ◽

Tian Fei Ren

Keyword(s):

Control Theory ◽

System Design ◽

Fuzzy Theory ◽

Calibration Method ◽

Automatic Calibration ◽

Matlab Simulation ◽

Calibration System ◽

Oil Tank ◽

Fuel Level

ABSTRACT：It introduces a kind of an Automatic Calibration System, especially for long-term drift of oil tank gauging system. long-term drift serious influence on measuring the accuracy and reliability of the system. With theory of Hydrostatic Tank Gauging[1]（HTG），as soon as the long-term drift occurring, the detection drift of oil pressure valueΔp will drift，and soon other the parameters of tank Gauging will be occurred. Because the value of Δp is difficult to directly determine, This paper puts forward a kind of automatic calibration method to obtain Δp according to the fuel level drift Δh) indirectly,By means of the HTG double level switches and fuzzy control theory. At last, by MATLAB simulation verify the correctness of the system design.

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

Applied Sciences ◽

10.3390/app9112182 ◽

2019 ◽

Vol 9 (11) ◽

pp. 2182 ◽

Cited By ~ 3

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.

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