Automatic Calibration of the 3D Vector Magnetometer

2012 ◽  
Vol 591-593 ◽  
pp. 1256-1259
Author(s):  
Long Li ◽  
Zhang He
Keyword(s):  
Linear Time ◽  
Three Dimensional ◽  
Calibration Method ◽  
Model Parameters ◽  
Linear Time Invariant ◽  
Vector Magnetometer ◽  
Calibration Algorithm ◽  
Mobile Consumer ◽  
The Difference ◽  
Consumer Devices

Embedded sensors are an emerging trend in mobile consumer devices. In this work a new algorithm is derived for the onboard calibration of three-axis magnetometers. The proposed calibration method is written in the sensor frame, and compensates for the combined effect of all linear time-invariant distortions, namely soft iron, hard iron, three-dimensional sensor non-orthogonally, scale factors, null-shift, arbitrary bias, among others. The new algorithm can be separated into two steps: In the first step, obtain the ellipsoid fitting parameters from comparing the difference between the measured value and the actual vector. In a second step, a calibration algorithm is adopted to compensate for magnetometers distortions. According to the model parameters the measured data is corrected to improve the precision of magnetometer. Simulation and experimental results with sensors data are presented and discussed, supporting the application of the algorithm to commercial and military platforms.

Stochastic Estimation of Human Ankle Mechanical Impedance in Lateral/Medial Rotation

2014 ◽  
Author(s):  
Evandro M. Ficanha ◽  
Mohammad Rastgaar
Keyword(s):  
Degrees Of Freedom ◽  
Muscle Activation ◽  
Transfer Functions ◽  
Linear Time ◽  
Mechanical Impedance ◽  
Linear Time Invariant ◽  
Ankle Impedance ◽  
Human Ankle ◽  
Medial Rotation ◽  
The Difference

This article compares stochastic estimates of human ankle mechanical impedance when ankle muscles were fully relaxed and co-contracting antagonistically. We employed Anklebot, a rehabilitation robot for the ankle to provide torque perturbations. Surface electromyography (EMG) was used to monitor muscle activation levels and these EMG signals were displayed to subjects who attempted to maintain them constant. Time histories of ankle torques and angles in the lateral/medial (LM) directions were recorded. The results also compared with the ankle impedance in inversion-eversion (IE) and dorsiflexion-plantarflexion (DP). Linear time-invariant transfer functions between the measured torques and angles were estimated for the Anklebot alone and when a human subject wore it; the difference between these functions provided an estimate of ankle mechanical impedance. High coherence was observed over a frequency range up to 30 Hz. The main effect of muscle activation was to increase the magnitude of ankle mechanical impedance in all degrees of freedom of ankle.

scholarly journals Identification of LTI Time-Delay Systems with Missing Output Data Using GEM Algorithm

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Xianqiang Yang ◽  
Hamid Reza Karimi
Keyword(s):  
Time Delay ◽  
Linear Time ◽  
Irregular Sampling ◽  
Delay Systems ◽  
Model Parameters ◽  
Delay Model ◽  
Sensor Failure ◽  
Linear Time Invariant ◽  
Failure Data ◽  
Time Invariant

This paper considers the parameter estimation for linear time-invariant (LTI) systems in an input-output setting with output error (OE) time-delay model structure. The problem of missing data is commonly experienced in industry due to irregular sampling, sensor failure, data deletion in data preprocessing, network transmission fault, and so forth; to deal with the identification of LTI systems with time-delay in incomplete-data problem, the generalized expectation-maximization (GEM) algorithm is adopted to estimate the model parameters and the time-delay simultaneously. Numerical examples are provided to demonstrate the effectiveness of the proposed method.

scholarly journals Laboratory Calibration of D-dot Sensor Based on System Identification Method

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3255 ◽  
Author(s):  
Ke Wang ◽  
Yantao Duan ◽  
Lihua Shi ◽  
Shi Qiu
Keyword(s):  
System Identification ◽  
Transfer Function ◽  
Electric Fields ◽  
Linear Time ◽  
Low Frequency ◽  
Calibration Method ◽  
Sensitivity Coefficient ◽  
Corner Frequency ◽  
Linear Time Invariant ◽  
The Time Domain

D-dot sensors can realize the non-contact measurement of transient electric fields, which is widely applied to electromagnetic pulse (EMP) measurements with characteristics of the wide frequency band, high linearity, and good stability. In order to achieve accurate calibration of D-dot sensors in the laboratory environment, this paper proposed a new calibration method based on system identification. Firstly, the D-dot sensor can be considered as a linear time-invariant (LTI) system under corner frequency, thus its frequency response can be characterized by the transfer function of a discrete output error (OE) model. Secondly, based on the partial linear regression of the transfer function curve, the sensitivity coefficient of the D-dot sensor is obtained. By increasing the influence weight of low-frequency components, this proposed method has better calibration performance when the waveform is distorted in the time domain, and can artificially adapt to the operating frequency range of the sensor at the same time.

The Projector Calibration Based on ZHANG’s Self-Calibration Method

2014 ◽  
Vol 981 ◽  
pp. 364-367
Author(s):  
Guang Yu ◽  
Bo Yang Yu ◽  
Shu Cai Yang ◽  
Li Wen ◽  
Wen Fei Dong ◽  
...  
Keyword(s):  
Camera Calibration ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Calibration Method ◽  
Linear Calibration ◽  
Self Calibration ◽  
Operation Process ◽  
Projector Calibration ◽  
Calibration Algorithm ◽  
Relationship Of

Projector calibration can be seen as a special case of the camera calibration. It can establish the relationship of the three dimensional space coordinates for points and projector image coordinates for points DMD by using a projector to project coding pattern. In camera calibration, ZHANG’s self-calibration was conducted in the maximum likelihood linear refinement. Operation process takes the lens distortion factors into account finding out the camera internal and external parameters finally. Using this algorithm to the projector calibration can solve the traditional linear calibration algorithm which is complex and poor robustness. Otherwise, it can improve the practicability of calibration method. This method can both calibrate the internal and external parameters of projector, which can solve the problem of independently inside or outside calibration.

scholarly journals On Modeling Centrifugal Compressors for Robust Control Design

1992 ◽  
Author(s):  
K. M. Murphy ◽  
D. Marchio ◽  
P. Kalata ◽  
R. Fischl
Keyword(s):  
Robust Control ◽  
Linear Model ◽  
Mass Flow ◽  
Linear Time ◽  
Control Design ◽  
Model Parameters ◽  
Inlet Valve ◽  
Linear Time Invariant ◽  
Non Linear ◽  
Robust Control Design

This paper considers the development of a Linear, Time Invariant (LTI) model for centrifugal compressor systems for robust control design. The objective is to obtain a LTI model of the compressor system so that robust controllers can be designed to control the outlet pressure and mass flow. The control variables are the motor armature voltage and the inlet valve position. The approach taken in this paper is to (1) obtain the non-linear, input-output dynamic reactions of the various components (inlet valve, ducts, compressor, nozzle and DC-motor), (2) identify the model parameters and variables (pressure, mass flow, etc.), (3) obtain a linear model of the system, (4) design a controller based on the LTI model and (5) test the designed controller on the non-linear model of the compressor system.

Estimating the forcing function in a mechanical system by an inverse calibration method

2021 ◽  
pp. 107754632110310
Author(s):  
Chapel Rice ◽  
Jay I Frankel
Keyword(s):  
Experimental Data ◽  
Transfer Function ◽  
Linear Time ◽  
Regularization Parameter ◽  
Calibration Method ◽  
Phase Plane Analysis ◽  
Constant Property ◽  
Vehicle Suspensions ◽  
Linear Time Invariant ◽  
Forcing Function

This article proposes and demonstrates a calibration-based integral formulation for resolving the forcing function in a mass–spring–damper system, given either displacement or acceleration data. The proposed method is novel in the context of vibrations, being thoroughly studied in the field of heat transfer. The approach can be expanded and generalized further to multi-variable systems associated with machine parts, vehicle suspensions, translational and rotational systems, gear systems, etc. when mathematically described by a system of constant property, linear, time-invariant ordinary differential equations. The analytic approach and subsequent numerical reconstruction of the forcing function is based on resolving a parameter-free inverse formulation for the equation(s) of motion. The calibration approach is formulated in the frequency domain and takes advantage of several observations produced by the dimensionality reduction leading to an algebratized system involving an input–output relationship and a transfer function possessing all the system parameters. The transfer function is eliminated in lieu of experimental data, from a calibration effort, thus leading to a reduction of systematic errors. These parameter-free, reduced systematic error aspects are the distinct and novel advantages of the proposed method. A first-kind Volterra integral equation is formed containing only the unknown forcing function and experimental data. As with all ill-posed problems, regularization must be introduced for system stabilization. A future-time technique is instituted for forming a family of predictions based on the chosen regularization parameter. The optimal regularization parameter is estimated using a combination of phase–plane analysis and cross-correlation principles. Finally, a numerical simulation is performed verifying the proposed approach.

scholarly journals Stochastic Estimation of Multi-Variable Human Ankle Mechanical Impedance

2009 ◽  
Author(s):  
Mohammad A. Rastgaar ◽  
Patrick Ho ◽  
Hyunglae Lee ◽  
Hermano Igo Krebs ◽  
Neville Hogan
Keyword(s):  
Transfer Functions ◽  
Linear Time ◽  
Plantar Flexion ◽  
Mechanical Impedance ◽  
Linear Time Invariant ◽  
Human Ankle ◽  
Time Histories ◽  
The Difference ◽  
Time Invariant ◽  
Impedance Functions

This article presents preliminary stochastic estimates of the multi-variable human ankle mechanical impedance. We employed Anklebot, a rehabilitation robot for the ankle, to provide torque perturbations. Time histories of the torques in Dorsi-Plantar flexion (DP) and Inversion-Eversion (IE) directions and the associated angles of the ankle were recorded. Linear time-invariant transfer functions between the measured torques and angles were estimated for the Anklebot and when the Anklebot was worn by a human subject. The difference between these impedance functions provided an estimate of the mechanical impedance of the ankle. High coherence was observed over a frequency range up to 30 Hz, indicating that this procedure yielded an accurate measure of ankle mechanical impedance in DP and IE directions.

Planetary Gear Train Dynamics

1994 ◽  
Vol 116 (3) ◽  
pp. 713-720 ◽  
Author(s):  
A. Kahraman
Keyword(s):  
Dynamic Behavior ◽  
Linear Time ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Planetary Gear ◽  
Gear Train ◽  
Planetary Gear Train ◽  
Gear Teeth ◽  
Linear Time Invariant ◽  
Mesh Phasing

A model to simulate the dynamic behavior of a single-stage planetary gear train with helical gears is developed. The three-dimensional dynamic model includes all six rigid body motions of the gears and the carrier. The generic nature of the formulation allows the analysis of a planetary gear set with any number of planets. Planets can be arbitrarily spaced (equally or unequally) around the sun gear. The model is also capable of handling different planet meshing conditions which are functions of number of gear teeth and planet positions. The linear time-invariant equations of motion are solved to obtain the natural modes and the forced vibration response due to static transmission errors. The proposed model is employed to describe the effects of the planet mesh phasing conditions on the dynamic behavior of a four-planet system.

MOTION SYNTHESIS FROM THE SEMANTIC SIGNALS

2008 ◽  
Vol 08 (04) ◽  
pp. 535-550
Author(s):  
DENGMING ZHU ◽  
ZHAOQI WANG ◽  
YINGPING ZHANG
Keyword(s):  
Linear Time ◽  
Model Parameters ◽  
Linear Time Invariant ◽  
Novel Technology ◽  
Human Joints ◽  
Low Dimensional ◽  
Linear Time Invariant System ◽  
Time Invariant ◽  
Human Motions ◽  
The Relationship

It is still an open problem to reuse the motion capture data in an intuitive way. In this paper, we present a novel technology to synthesize animations from the low-dimensional semantic signals. The semantic signals are defined as the meanings which are visible to the animators, such as the angles of joints rotation around axis, the trajectories of joints, or other intuitive motion signals. A linear time-invariant system is used to model the relationship between the input semantic signals and the output human motions. Once the model parameters are estimated, the outputs of system can be effectively controlled by the inputs. Because the semantic signals can be intuitively sketched or modified by animators according to the general knowledge in everyday life, this may provide an intuitive tool for animators to create new animations from the existing data. Furthermore, a novel algorithm is also proposed to edit the semantic signals for creating the full body motions while considering the correlations among joints. This is different from the traditional methods which consider human joints as independent from each other.

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