scholarly journals Decoupling of a Disk Resonator From Linear Acceleration Via Mass Matrix Perturbation

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
David Schwartz ◽  
Robert T. M’Closkey
Keyword(s):  
Mass Matrix ◽  
Angular Rate ◽  
Center Of Mass ◽  
Nodal Point ◽  
Linear Acceleration ◽  
Small Mass ◽  
Scale Model ◽  
Matrix Perturbation ◽  
Coupled Modes ◽  
Disk Resonator

Axisymmetric microelectromechanical (MEM) vibratory rate gyroscopes are designed so the central post which attaches the resonator to the sensor case is a nodal point of the two Coriolis-coupled modes that are exploited for angular rate sensing. This configuration eliminates any coupling of linear acceleration to these modes. When the gyro resonators are fabricated, however, small mass and stiffness asymmetries cause coupling of these modes to linear acceleration of the sensor case. In a resonator postfabrication step, this coupling can be reduced by altering the mass distribution on the resonator so that its center of mass is stationary while the operational modes vibrate. In this paper, a scale model of the disk resonator gyroscope (DRG) is used to develop and test methods that significantly reduce linear acceleration coupling.

Laboratory and field evaluation of a small form factor head impact sensor in un-helmeted play

2017 ◽  
Vol 232 (3) ◽  
pp. 242-254 ◽  
Author(s):  
Derek Nevins ◽  
Kasee Hildenbrand ◽  
Jeff Kensrud ◽  
Anita Vasavada ◽  
Lloyd Smith
Keyword(s):  
Form Factor ◽  
Center Of Mass ◽  
False Negative ◽  
Angular Acceleration ◽  
Linear Acceleration ◽  
Field Evaluation ◽  
Head Impact ◽  
Sensor Data ◽  
Small Form ◽  
Small Form Factor

Head impact sensors are increasingly used to quantify the frequency and magnitude of head impacts in sports. A dearth of information exists regarding head impact in un-helmeted sport, despite the substantial number of concussions experienced in these sports. This study evaluated the performance of one small form factor head impact sensor in both laboratory and field environments. In laboratory tests, sensor performance was assessed using a Hybrid III headform and neck. The headform assembly was mounted on a low-friction sled and impacted with three sports balls over a range of velocities (10–31 m/s) at two locations and from three directions. Measures of linear and angular acceleration obtained from the small form factor wireless sensor were compared to measures of linear and angular acceleration obtained by wired sensors mounted at the headform center of mass. Accuracy of the sensor varied inversely with impact magnitude, with relative differences across test conditions ranging from 0.1% to 266.0% for peak linear acceleration and 4.7% to 94.6% for peak angular acceleration when compared to a wired reference system. In the field evaluation, eight male high school soccer players were instrumented with the head impact sensor in seven games. Video of the games was synchronized with sensor data and reviewed to determine the number of false positive and false negative head acceleration event classifications. Of the 98 events classified as valid by the sensor, 20.5% (20 impacts) did not result from contact with the ball, another player, the ground or player motion and were therefore considered false positives. Video review of events classified as invalid or spurious by the sensor found 77.8% (14 of 18 impacts) to be due to contact with the ball, another player or player motion and were considered false negatives.

scholarly journals Mapping and determining the center of mass of a rotating object using a moving observer

2018 ◽  
Vol 37 (1) ◽  
pp. 83-103 ◽  
Author(s):  
Timothy P Setterfield ◽  
David W Miller ◽  
John J Leonard ◽  
Alvar Saenz-Otero
Keyword(s):  
Angular Rate ◽  
Center Of Mass ◽  
Computational Cost ◽  
Target Object ◽  
Factor Graph ◽  
Visual Sensor ◽  
Fixed Frame ◽  
Computational Performance ◽  
Kinematic Factor ◽  
Graph Mapping

For certain applications, such as on-orbit inspection of orbital debris, defunct satellites, and natural objects, it is necessary to obtain a map of a rotating object from a moving observer, as well to estimate the object’s center of mass. This paper addresses these tasks using an observer that measures its own orientation, angular rate, and acceleration, and is equipped with a dense 3D visual sensor, such as a stereo camera or a light detection and ranging (LiDAR) sensor. The observer’s trajectory is estimated independently of the target object’s rotational motion. Pose-graph mapping is performed using visual odometry to estimate the observer’s trajectory in an arbitrary target-fixed frame. In addition to applying pose constraint factors between successive frames, loop closure is performed between temporally non-adjacent frames. A kinematic constraint on the target-fixed frame, resulting from the rigidity of the target object, is exploited to create a novel rotation kinematic factor. This factor connects a trajectory estimation factor graph with the mapping pose graph, and facilitates estimation of the target’s center of mass. Map creation is performed by transforming detected feature points into the target-fixed frame, centered at the estimated center of mass. Analysis of the algorithm’s computational performance reveals that its computational cost is negligible compared with that of the requisite image processing.

Modeling of Jaw-Head-Neck Dynamics during Whiplash

1989 ◽  
Vol 68 (9) ◽  
pp. 1360-1365 ◽  
Author(s):  
K. Schneider ◽  
R.F. Zernicke ◽  
G. Clark
Keyword(s):  
Computer Simulations ◽  
Time Course ◽  
Center Of Mass ◽  
Linear Acceleration ◽  
Signs And Symptoms ◽  
Impulsive Loading ◽  
Opening Angle ◽  
Jaw Opening ◽  
Jaw Model ◽  
Head Neck

Clinicians report signs and symptoms of temporomandibular joint (TMJ) disorders in many patients who have experienced automobile rear-end collisions involving neck hyperextension (whiplash). In order for relationships between TMJ disorders and rear-end collisions to be explored, the dynamic response of the jaw to hyperextension of the neck associated with automobile rear-end collisions needs to be quantified. To achieve this goal, we extended an existing head-neck model by adding a movable jaw, and performed preliminary computer simulations of the jaw movements during rear-end collisions at 6. 71 ms-1 (75 mph) and 13.41 ms -1 (30 mph). The initial computer simulations produced promising kinematic and dynamic results, such as: relative angle between the head and jaw (jaw-opening angle), predicted TMJ torques, and displacement and linear acceleration of the jaw's center of mass. However, the absolute values and time course of our results must be viewed with caution, since the jaw model has not yet been validated with experimental data. Nevertheless, the modeling approach, detailed in this study, shows good promise for eventually providing quantitative dynamic information about the jaw-head-neck system during impulsive loading.

scholarly journals Frequency Tuning of a Disk Resonator Gyro Via Mass Matrix Perturbation

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
David Schwartz ◽  
Dong Joon Kim ◽  
Robert T. M’Closkey
Keyword(s):  
High Performance ◽  
Frequency Tuning ◽  
Perturbation Technique ◽  
Mass Matrix ◽  
Resonant Mode ◽  
Matrix Perturbation ◽  
Operating Environment ◽  
Vibratory Gyroscopes ◽  
Resonant Modes ◽  
The Stability

Electrostatic tuning of the resonant modes in microelectromechanical vibratory gyroscopes is often suggested as a means for compensating manufacturing aberrations that produce detuned resonances. In high performance sensors, however, this approach places very stringent requirements on the stability of the bias voltages used for tuning. Furthermore, the bias voltage stability must be maintained over the operating environment, especially with regard to temperature variations. An alternative solution to this problem is to use mass perturbations of the sensor’s resonant structure for resonant mode tuning. This paper presents a new mass perturbation technique that only relies on the sensor’s integrated actuators and pick-offs to guide the mass perturbation process. The algorithm is amenable to automation and eliminates the requirement that the modal nodes of the resonator be identified by direct measurement.

Three-dimensional cracked discs under anti-plane loading and effects of the boundary conditions

2015 ◽  
Vol 6 (4) ◽  
pp. 541-564 ◽  
Author(s):  
Filippo Berto ◽  
Alberto Campagnolo
Keyword(s):  
Boundary Conditions ◽  
Control Volume ◽  
Three Dimensional ◽  
Scale Model ◽  
Mode Iii ◽  
Coupled Modes ◽  
Present Contribution ◽  
Content Type ◽  
Dimensional Effects ◽  
Notch Tip

Purpose – Accordingly to the recent multi-scale model proposed by Sih and Tang, different orders of stress singularities are related to different material dependent boundary conditions associated with the interaction between the V-notch tip and the material under the remotely applied loading conditions. This induces complex three-dimensional stress and displacement fields in the proximity of the notch tip, which are worthy of investigation. The paper aims to discuss these issues. Design/methodology/approach – Starting from Sih and Tang’s model, in the present contribution the authors propose some analytical expressions for the calculation of the strain energy density (SED) averaged over a control volume embracing the V-notch tip. The expressions vary as a function of the different boundary conditions. Dealing with the specific crack case, the results from the analytical frame are compared with those determined numerically under linear-elastic hypotheses, by applying different constraints to the through-the-thickness crack edges in three-dimensional discs subjected to Mode III loading. Free-free and free-clamped cases are considered. Findings – Due to three-dimensional effects, the application of a nominal Mode III loading condition automatically provokes coupled Modes (I and II). Not only the intensity of the induced modes but also their degree of singularity depend on the applied conditions on the crack flanks. The variability of local SED through the thickness of the disc is analysed by numerical analyses and compared with the theoretical trend. Originality/value – The capability of the SED to capture the combined three-dimensional effects is discussed in detail showing that this parameter is particularly useful when the definition of the stress intensity factors (SIFs) is ambiguous or the direct comparison between SIFs with odd dimensionalities is not possible.

scholarly journals LARGE MIXING FROM SMALL: PSEUDO-DIRAC NEUTRINOS AND THE SINGULAR SEE-SAW

2005 ◽  
Vol 20 (28) ◽  
pp. 6373-6390 ◽  
Author(s):  
G. J. STEPHENSON ◽  
T. GOLDMAN ◽  
B. H. J. MCKELLAR ◽  
M. GARBUTT
Keyword(s):  
Neutrino Mass ◽  
Sterile Neutrino ◽  
Mass Matrix ◽  
Small Mass ◽  
Neutrino Mass Matrix ◽  
Numerical Examples ◽  
Mixing Parameters ◽  
Experimental Resolution ◽  
Active Mixing

If the sterile neutrino mass matrix in an otherwise conventional see-saw model has a rank less than the number of flavors, it is possible to produce pseudo-Dirac neutrinos. In a two-flavor, sterile rank 1 case, we demonstrate analytic conditions for large active mixing induced by the existence of (and coupling to) the sterile neutrino components. For the three-flavor, rank 1 case, "3+2" scenarios with large mixing also devolve naturally as we show by numerical examples. We observe that, in this approach, small mass differences can develop naturally without any requirement that masses themselves are small. Additionally, we point out that significant three-channel mixing and limited experimental resolution can combine to produce extracted two-channel mixing parameters at variance with the actual values.

scholarly journals Geometry Investigation and Performance Optimization of a Single-Mass Piezoelectric 6-DOF IMU

2020 ◽  
Vol 10 (5) ◽  
pp. 6282-6289
Author(s):  
H. Almabrouk ◽  
B. Mezghani ◽  
G. Agnus ◽  
S. Kaziz ◽  
Y. Bernard ◽  
...  
Keyword(s):  
Finite Element ◽  
Performance Optimization ◽  
Angular Rate ◽  
Linear Acceleration ◽  
Longitudinal Axis ◽  
Element Model ◽  
Measurement Unit ◽  
Optimized Design ◽  
Element Analysis ◽  
Single Mass

This paper explores the fundamental steps towards the development of a 6-axis piezoelectric Inertial Measurement Unit (IMU). The main specification of the reported device is its ability to concurrently detect 3-axis acceleration and angular velocity using a single mass-based design. This work represents a detailed numerical analysis based on a finite element model. Experimental reported data are exploited to validate the FEM model in terms of acceleration detection which is ensured through the direct piezoelectric effect. The angular rate is detected thanks to the Coriolis effect by ensuring drive and sense modes. Using a Finite Element Analysis (FEA), light was shed on the different basic parameters that influence the sensor performance in order to present an optimized design. A detailed geometrical investigation of factors such as anchor position, optimized locations for sensing electrodes, proof-mass dimensions, PZT thickness, and operating frequency is illustrated. The 6-DOF sensor outputs are extracted in terms of the original and the optimized design. The amelioration rate of sensitivity is found to be up to 165% for linear acceleration, while for angular rate sensing, the lateral sensitivity is ameliorated by about 330% and is multiplied by around ten times in the normal axis. The optimized design exhibits a good acceleration sensitivity of 260mV/g in the lateral axis and 60.7mV/g in the z-axis. For angular rate sensing, the new design is more sensitive along the longitudinal axis than the lateral one. Sensitivity values are found to be 2.65µV/rad/s for both x-and y-axis, and 1.24V/rad/s for the z-axis.

scholarly journals Analysis and control of a Stewart platform as base motion compensators - Part I: Kinematics using moving frames

2021 ◽  
Author(s):  
Takeyuki Ono ◽  
Ryosuke Eto ◽  
Junya Yamakawa ◽  
Hidenori Murakami
Keyword(s):  
Lie Group ◽  
Inverse Kinematics ◽  
Center Of Mass ◽  
Base Plate ◽  
Stewart Platform ◽  
The Body ◽  
Scale Model ◽  
Moving Frames ◽  
Coordinate Frames ◽  
Control Application

AbstractKinematics and its control application are presented for a Stewart platform whose base plate is installed on a floor in a moving ship or a vehicle. With a manipulator or a sensitive equipment mounted on the top plate, a Stewart platform is utilized to mitigate the undesirable motion of its base plate by controlling actuated translational joints on six legs. To reveal closed loops, a directed graph is utilized to express the joint connections. Then, kinematics begins by attaching an orthonormal coordinate system to each body at its center of mass and to each joint to define moving coordinate frames. Using the moving frames, each body in the configuration space is represented by an inertial position vector of its center of mass in the three-dimensional vector space ℝ3, and a rotation matrix of the body-attached coordinate axes. The set of differentiable rotation matrices forms a Lie group: the special orthogonal group, SO(3). The connections of body-attached moving frames are mathematically expressed by using frame connection matrices, which belong to another Lie group: the special Euclidean group, SE(3). The employment of SO(3) and SE(3) facilitates effective matrix computations of velocities of body-attached coordinate frames. Loop closure constrains are expressed in matrix form and solved analytically for inverse kinematics. Finally, experimental results of an inverse kinematics control are presented for a scale model of a base-moving Stewart platform. Dynamics and a control application of inverse dynamics are presented in the part II-paper.

Research on vehicle attitude and heading reference system based on multi-sensor information fusion

2020 ◽  
Vol 234 (13) ◽  
pp. 3056-3067
Author(s):  
Jiacheng Fan ◽  
Zengcai Wang ◽  
Mingxing Lin ◽  
Susu Fang ◽  
Xiangpeng Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Cost ◽  
Angular Rate ◽  
Estimation Method ◽  
Linear Acceleration ◽  
Operating Conditions ◽  
Frequency Noise ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Gravity Sensor

To improve the accuracy of attitude and heading reference systems for moving vehicles, an effective orientation estimation method is proposed. The method uses an odometer, a low-cost magnetic, angular rate, and gravity sensor. This study addresses the problems of non-orthogonal error, carrier magnetic field interference and calibration to obtain accurate, long-term, stable magnetic field strength. A neural network fusion 12-parameter ellipse fitting method is proposed to eliminate the soft magnetic field and hard magnetic field interference. The interference to the accelerometer from linear acceleration is eliminated by using an odometer and a gyroscope, and the high-frequency noise from the accelerometer is eliminated by using a low-pass filter. An improved method to evaluate vehicle attitude is proposed and utilized to compensate for filtered accelerometer measurement when the vehicle is moving at a uniform, accelerate and steering state. The proposed method uses an effective adaptive Kalman filter based on the error state model to reduce dynamic perturbations. Filter gain is adaptively tuned under different moving modes by adjusting the noise matrix. The effectiveness of the algorithm is verified by experiments and simulations in multiple operating conditions.

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