scholarly journals Calibrating Range Measurements of Lidars Using Fixed Landmarks in Unknown Positions

2020 ◽  
Author(s):  
Anas Alhashimi ◽  
Martin Magnusson ◽  
Steffi Knorn ◽  
Damiano Varagnolo
Keyword(s):  
Fixed Points ◽  
Field Tests ◽  
Calibration Procedure ◽  
Light Detection And Ranging ◽  
Sensor Calibration ◽  
Inertial Reference Frame ◽  
Noise Levels ◽  
Calibration Problem ◽  
Distance Sensor ◽  
Additional Hardware

We consider the problem of calibrating distance measurement of Light Detection and Ranging (lidar) sensor without using additional hardware, but rather exploiting assumptions on the environment surrounding the sensor during the calibration procedure. More specifically we consider the assumption of calibrating the sensor by placing it in an environment so that its measurements lie in a 2D plane that is parallel to the ground, and so that its measurements come from fixed objects that develop orthogonally w.r.t. the ground, so that they may be considered as fixed points in an inertial reference frame. We moreover consider the intuition that moving the distance sensor within this environment implies that its measurements should be such that the relative distances and angles among the fixed points above remain the same. We thus exploit this intuition to cast the sensor calibration problem as making its measurements comply with this assumption that “fixed features shall have fixed relative distances and angles”. The resulting calibration procedure does thus not need to use additional (typically expensive) equipment, nor deploying special hardware. As for the proposed estimation strategies, from a mathematical perspective we consider models that lead to analytically solvable equations, so to enable deployment in embedded systems. Besides proposing the estimators we moreover analyse their statistical performance both in simulation and with field tests, reporting thus the dependency of the MSE performance of the calibration procedure as a function of the sensor noise levels, and observing that in field tests the approach can lead to a ten-fold improvement in the accuracy of the raw measurements.

scholarly journals Calibrating Range Measurements of Lidars Using Fixed Landmarks in Unknown Positions

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 155
Author(s):  
Anas Alhashimi ◽  
Martin Magnusson ◽  
Steffi Knorn ◽  
Damiano Varagnolo
Keyword(s):  
Fixed Points ◽  
Field Tests ◽  
Calibration Procedure ◽  
Light Detection And Ranging ◽  
Sensor Calibration ◽  
Noise Levels ◽  
Range Measurements ◽  
Calibration Problem ◽  
Dependent Measurement ◽  
Distance Sensor

We consider the problem of calibrating range measurements of a Light Detection and Ranging (lidar) sensor that is dealing with the sensor nonlinearity and heteroskedastic, range-dependent, measurement error. We solved the calibration problem without using additional hardware, but rather exploiting assumptions on the environment surrounding the sensor during the calibration procedure. More specifically we consider the assumption of calibrating the sensor by placing it in an environment so that its measurements lie in a 2D plane that is parallel to the ground. Then, its measurements come from fixed objects that develop orthogonally w.r.t. the ground, so that they may be considered as fixed points in an inertial reference frame. Moreover, we consider the intuition that moving the distance sensor within this environment implies that its measurements should be such that the relative distances and angles among the fixed points above remain the same. We thus exploit this intuition to cast the sensor calibration problem as making its measurements comply with this assumption that “fixed features shall have fixed relative distances and angles”. The resulting calibration procedure does thus not need to use additional (typically expensive) equipment, nor deploy special hardware. As for the proposed estimation strategies, from a mathematical perspective we consider models that lead to analytically solvable equations, so to enable deployment in embedded systems. Besides proposing the estimators we moreover analyze their statistical performance both in simulation and with field tests. We report the dependency of the MSE performance of the calibration procedure as a function of the sensor noise levels, and observe that in field tests the approach can lead to a tenfold improvement in the accuracy of the raw measurements.

Uncertainty Evaluation on Multi-Hole Aerodynamic Pressure Probes

2020 ◽  
Author(s):  
Andrea Notaristefano ◽  
Paolo Gaetani ◽  
Vincenzo Dossena ◽  
Alberto Fusetti
Keyword(s):  
Uncertainty Analysis ◽  
Evaluation Method ◽  
Experimental Testing ◽  
Uncertainty Propagation ◽  
Calibration Procedure ◽  
Fast Response ◽  
Uncertainty Evaluation ◽  
Sensor Calibration ◽  
Pressure Probe ◽  
Aerodynamic Pressure

Abstract In the frame of a continuous improvement of the performance and accuracy in the experimental testing of turbomachines, the uncertainty analysis on measurements instrumentation and techniques is of paramount importance. For this reason, since the beginning of the experimental activities at the Laboratory of Fluid Machines (LFM) located at Politecnico di Milano (Italy), this issue has been addressed and different methodologies have been applied. This paper proposes a comparison of the results collected applying two methods for the measurement uncertainty quantification to two different aerodynamic pressure probes: sensor calibration, aerodynamic calibration and probe application are considered. The first uncertainty evaluation method is the so called “Uncertainty Propagation” method (UPM); the second is based on the “Monte Carlo” method (MCM). Two miniaturized pressure probes have been selected for this investigation: a pneumatic 5-hole probe and a spherical fast response aerodynamic pressure probe (sFRAPP), the latter applied as a virtual 4-hole probe. Since the sFRAPP is equipped with two miniaturized pressure transducers installed inside the probe head, a specific calibration procedure and a dedicated uncertainty analysis are required.

scholarly journals The Shape From Motion Approach to Rapid and Precise Force/Torque Sensor Calibration

1997 ◽  
Vol 119 (2) ◽  
pp. 229-235 ◽  
Author(s):  
R. M. Voyles ◽  
J. D. Morrow ◽  
P. K. Khosla
Keyword(s):  
Least Squares ◽  
Explicit Knowledge ◽  
Calibration Procedure ◽  
Sensor Calibration ◽  
Torque Sensor ◽  
Data Set ◽  
Redundant Data ◽  
Sensor Signals ◽  
A New Technique ◽  
Value Decomposition

We present a new technique for multi-axis force/torque sensor calibration called shape from motion. The novel aspect of this technique is that it does not require explicit knowledge of the redundant applied load vectors, yet it retains the noise rejection of a highly redundant data set and the rigor of least squares. The result is a much faster, slightly more accurate calibration procedure. A constant-magnitude force (produced by a mass in a gravity field) is randomly moved through the sensing space while raw data is continuously gathered. Using only the raw sensor signals, the motion of the force vector (the “motion”) and the calibration matrix (the “shape”) are simultaneously extracted by singular value decomposition. We have applied this technique to several types of force/torque sensors and present experimental results for a 2-DOF fingertip and a 6-DOF wrist sensor with comparisons to the standard least squares approach.

scholarly journals TWO-STEP CAMERA CALIBRATION METHOD DEVELOPED FOR MICRO UAV'S

2016 ◽  
Vol XLI-B1 ◽  
pp. 829-833 ◽  
Author(s):  
M. Gašparović ◽  
D. Gajski
Keyword(s):  
Camera Calibration ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Unmanned Aircraft ◽  
Sensor Calibration ◽  
Step Process ◽  
Complex Process ◽  
One Step ◽  
Accurate Procedure ◽  
Wide Angle Camera

The development of unmanned aerial vehicles (UAVs) and continuous price reduction of unmanned systems attracted us to this research. Professional measuring systems are dozens of times more expensive and often heavier than "amateur", non-metric UAVs. For this reason, we tested the DJI Phantom 2 Vision Plus UAV. Phantom’s smaller mass and velocity can develop less kinetic energy in relation to the professional measurement platforms, which makes it potentially less dangerous for use in populated areas. In this research, we wanted to investigate the ability of such non-metric UAV and find the procedures under which this kind of UAV may be used for the photogrammetric survey. It is important to emphasize that UAV is equipped with an ultra wide-angle camera with 14MP sensor. Calibration of such cameras is a complex process. In the research, a new two-step process is presented and developed, and the results are compared with standard one-step camera calibration procedure. Two-step process involves initially removed distortion on all images, and then uses these images in the phototriangulation with self-calibration. The paper presents statistical indicators which proved that the proposed two-step process is better and more accurate procedure for calibrating those types of cameras than standard one-step calibration. Also, we suggest two-step calibration process as the standard for ultra-wideangle cameras for unmanned aircraft.

Remote Robot-Sensor Calibration Service

2019 ◽  
Vol 10 (1) ◽  
pp. 15-36
Author(s):  
Tapio Heikkilä ◽  
Tuomas Seppälä ◽  
Timo Kuula ◽  
Hannu Karvonen
Keyword(s):  
User Interface ◽  
Asset Management ◽  
Interface Design ◽  
User Interface Design ◽  
Calibration Procedure ◽  
Sensor Calibration ◽  
Physical Processes ◽  
Physical Systems ◽  
Robot Systems ◽  
Technology Specialists

Cyber physical systems (CPSs) are integrating computation, networking, and physical processes. CPSs facilitate improvements especially for asset management. The authors have contributed to robot automation with CPS technologies by a pilot system to support setup and maintenance of sensor-based robot systems with remote calibration services. This paper has focused to support remotely-located technology specialists as well as local field personnel by appropriate user interface design. A design example is given for a remote robot-sensor calibration procedure. In the user interface design, the authors follow loosely the Ecological Interface Design (EID) approach.

Embedded Self-Sensing Piezoelectric Active Sensors for On-Line Structural Identification

2001 ◽  
Vol 124 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Structural Identification ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Ultrasonic Frequency ◽  
Active Sensors ◽  
Turbine Engine ◽  
On Line

The benefits and limitations of using embedded piezoelectric active sensors for structural identification at ultrasonic frequency are highlighted. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electro-mechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimension structures and accounts for both axial and flexural vibrations. Experiments were conducted on simple specimens in support of the theoretical investigation, and on realistic turbine blade specimen to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the latter’s noninvasive characteristics. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a nonintrusive sensor array adequate for on-line automatic structural identification and health monitoring. The sensor calibration procedure is outlined. Numerical estimation of the noninvasive properties of the proposed active sensors in comparison with conventional sensors is presented. Self-diagnostics capabilities of the proposed sensors were also investigated and methods for automatic self-test implementation are discussed. The paper underlines that the use of piezoelectric wafer active sensors is not only advantageous, but, in certain situations, may be the sole investigative option, as in the case of precision machinery, small but critical turbine-engine parts, and computer industry components.

scholarly journals Characterization of Piezoelectric Wafer Active Sensors

2000 ◽  
Vol 11 (12) ◽  
pp. 959-976 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Active Sensors ◽  
One Dimensional ◽  
Active Sensor ◽  
Aluminum Plates ◽  
In The Beginning

In the beginning, the classical one-dimensional analysis of piezoelectric active sensors is reviewed. The complete derivation for a free-free sensor is then extended to cover the cases of clamped and elastically constrained sensors. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimensional structures and accounts for both axial and flexural vibrations. The numerical analysis was performed and supported by experimental results. Experiments were conducted on simple beam specimens to support the theoretical investigation, and on thin gauge aluminum plates to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the sensor’s non-invasive characteristics. The sensor calibration procedure is outlined and statistical analysis was presented. It was found that PZT active sensors have stable and repeatable characteristics not only in as-received condition, but also while mounted on 1-D or 2-D host structure. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a non-intrusive sensor array adequate for on-line automatic structural identification and health monitoring.

scholarly journals An Innovative Calibration Method for the Inversion of Satellite Observations

2010 ◽  
Vol 49 (12) ◽  
pp. 2458-2473 ◽  
Author(s):  
Filipe Aires ◽  
Frédéric Bernardo ◽  
Héléne Brogniez ◽  
Catherine Prigent
Keyword(s):  
Water Vapor ◽  
Single Channel ◽  
Weather Prediction ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Satellite Observations ◽  
Radiative Transfer Model ◽  
Sensor Calibration ◽  
Transfer Model ◽  
Nwp Model

Abstract Retrieval schemes often use two important components: 1) a radiative transfer model (RTM) inside the retrieval procedure or to construct the learning dataset for the training of the statistical retrieval algorithms and 2) a numerical weather prediction (NWP) model to provide a first guess or, again, to construct a learning dataset. This is particularly true in operational centers. As a consequence, any physical retrieval or similar method is limited by inaccuracies in the RTM and NWP models on which it is based. In this paper, a method for partially compensating for these errors as part of the sensor calibration is presented and evaluated. In general, RTM/NWP errors are minimized as best as possible prior to the training of the retrieval method, and then tolerated. The proposed method reduces these unknown and generally nonlinear residual errors by training a separate preprocessing neural network (NN) to produce calibrated radiances from real satellite data that approximate those radiances produced by the “flawed” NWP and RTM models. The final “compensated/flawed” retrieval assures better internal consistency of the retrieval procedure and then produces more accurate results. To the authors’ knowledge, this type of NN model has not been used yet for this purpose. The calibration approach is illustrated here on one particular application: the retrieval of atmospheric water vapor from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) and the Humidity Sounder for Brazil (HSB) measurements for nonprecipitating scenes, over land and ocean. Before being inverted, the real observations are “projected” into the space of the RTM simulation space from which the retrieval is designed. Validation of results is performed with radiosonde measurements and NWP analysis departures. This study shows that the NN calibration of the AMSR-E/HSB observations improves water vapor inversion, over ocean and land, for both clear and cloudy situations. The NN calibration is efficient and very general, being applicable to a large variety of problems. The nonlinearity of the NN allows for the calibration procedure to be state dependent and adaptable to specific cases (e.g., the same correction will not be applied to medium-range measurement and to extreme conditions). Its multivariate nature allows for a full exploitation of the complex correlation structure among the instrument channels, making the calibration of each single channel more robust. The procedure would make it possible to project the satellite observations in a reference observational space defined by radiosonde measurements, RTM simulations, or other instrument observational space.

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