scholarly journals Identifiability of Tyre Force Contact Prediction from Deformation Measurements

2021 ◽  
Vol 347 ◽  
pp. 00027
Author(s):  
R.G. Gast ◽  
P.S. Els ◽  
S. Kok ◽  
D.N. Wilke ◽  
T.R. Botha
Keyword(s):  
Initial Guess ◽  
Measurement Noise ◽  
Virtual Experiment ◽  
Loss Of Life ◽  
Inverse Simulation ◽  
Inner Surface ◽  
Force Contact ◽  
External Forces ◽  
Safety Systems ◽  
Deformation Measurements

The possibility of accurately inferring the external forces applied to a vehicle can directly contribute to better safety systems and thus lowers the chance of injury or loss of life. These external forces are applied to a vehicle through the tyres and are challenging to measure directly. Still, it is possible to measure acceleration, deformation, or strain on the inner surface of a tyre. These measurements are theorized to be strongly linked to the forces produced by the tyre. However, it is still unknown whether or not one can always identify external forces from internal measurements in this way. Research has mainly focused on obtaining estimates of tyre forces rather than establishing to what extent these tyre forces are identifiable. This paper investigates this by conducting a virtual experiment that simulates known external forces applied to the tyre and computes the strains and displacements inside the tyre. A virtual inverse simulation then recovers the external forces from either the deformation or strain computed on the inside of the tyre. The identifiability of the forces recovered by the virtual inverse simulation is investigated by adding artificial measurement noise and initial guess perturbations to quantify the variance in the identified forces.

A New Measurement Device for Kinematic Calibration of Parallel Manipulators

2004 ◽  
Author(s):  
Abdul Rauf ◽  
Sung-Gaun Kim ◽  
Jeha Ryu
Keyword(s):  
Parallel Manipulators ◽  
Measurement Procedure ◽  
Initial Guess ◽  
Measurement Noise ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
End Effector ◽  
Experimental Procedure ◽  
New Device ◽  
Rotation Component

Kinematic calibration is a process that estimates the actual values of geometric parameters to minimize the error in absolute positioning. Measuring all the components of Cartesian posture assure identification of all parameters. However, measuring all components, particularly the orientation, can be difficult and expensive. On the other hand, with partial pose measurements, experimental procedure is simpler. However, all parameters may not be identifiable. This paper proposes a new device that can be used to identify all kinematic parameters with partial pose measurements. Study is performed for a 6 DOF (degree-of-freedom) fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector’s motion to 5 DOF and measures two position components and one rotation component of the end-effector. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise. Intrinsic inaccuracies of the device can significantly deteriorate the calibration results. A measurement procedure is proposed and cost functions are discussed to prevent propagation of the inaccuracies to the calibration results.

scholarly journals A framework for non-ICP lidar-based pose estimation using an optimally constrained 3D target

2021 ◽  
Author(s):  
Pierre Saint-Cyr
Keyword(s):  
Pose Estimation ◽  
Full Range ◽  
Point Clouds ◽  
Initial Guess ◽  
Measurement Noise ◽  
Lidar Data ◽  
Lidar Measurement ◽  
Camera System ◽  
Icp Algorithm ◽  
Scan Data

This thesis describes a non-ICP-based framework fohr [sic] the computation of a pose estimate of a special target shape from raw LIDAR scan data. In previous work, an ideal unambiguously-shaped 3D target (the Reduced Ambiguity Cuboctahedron, or RAC) was designed for use in LIDAR-based pose estimation. The RAC was designed to be used in an ICP algorithm, without an initial guess at the pose. This property is, however, not robust to LIDAR measurement noise and data artefacts. The pose estimation technique described in the present work is based upon the geometric non-ambiguity criteria used originally to design the target, and is robust to the aforementioned LIDAR data characteristics. This technique has been tested using simulated point clouds representing a full range of views of the RAC. The technique has been validated using real LIDAR scans of the RAC, generated at Neptec's Ottawa facility with their Laser Camera System (LCS). Experimental results using LCS data show that pose estimates can be generated with mean errors (relative to ICP) of 1.03 [deg] and 1.08 [mm], having standard deviations of 0.56 [deg] and 0.67 [mm] respectively.

scholarly journals A framework for non-ICP lidar-based pose estimation using an optimally constrained 3D target

2021 ◽  
Author(s):  
Pierre Saint-Cyr
Keyword(s):  
Pose Estimation ◽  
Full Range ◽  
Point Clouds ◽  
Initial Guess ◽  
Measurement Noise ◽  
Lidar Data ◽  
Lidar Measurement ◽  
Camera System ◽  
Icp Algorithm ◽  
Scan Data

This thesis describes a non-ICP-based framework fohr [sic] the computation of a pose estimate of a special target shape from raw LIDAR scan data. In previous work, an ideal unambiguously-shaped 3D target (the Reduced Ambiguity Cuboctahedron, or RAC) was designed for use in LIDAR-based pose estimation. The RAC was designed to be used in an ICP algorithm, without an initial guess at the pose. This property is, however, not robust to LIDAR measurement noise and data artefacts. The pose estimation technique described in the present work is based upon the geometric non-ambiguity criteria used originally to design the target, and is robust to the aforementioned LIDAR data characteristics. This technique has been tested using simulated point clouds representing a full range of views of the RAC. The technique has been validated using real LIDAR scans of the RAC, generated at Neptec's Ottawa facility with their Laser Camera System (LCS). Experimental results using LCS data show that pose estimates can be generated with mean errors (relative to ICP) of 1.03 [deg] and 1.08 [mm], having standard deviations of 0.56 [deg] and 0.67 [mm] respectively.

A regularized approach to linear regression of fatigue life measurements

2016 ◽  
Vol 7 (1) ◽  
pp. 95-105 ◽  
Author(s):  
S. Ali Faghidian
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Linear Regression ◽  
Tikhonov Regularization ◽  
Regularization Method ◽  
Initial Guess ◽  
Measurement Noise ◽  
Attractive Alternative ◽  
Life Distribution ◽  
Content Type

Purpose – The linear regression technique is widely used to determine empirical parameters of fatigue life profile while the results may not continuously depend on experimental data. Thus Tikhonov-Morozov method is utilized here to regularize the linear regression results and consequently reduces the influence of measurement noise without notably distorting the fatigue life distribution. The paper aims to discuss these issues. Design/methodology/approach – Tikhonov-Morozov regularization method would be shown to effectively reduce the influences of measurement noise without distorting the fatigue life distribution. Moreover since iterative regularization methods are known to be an attractive alternative to Tikhonov regularization, four gradient iterative methods called as simple iteration, minimum error, steepest descent and conjugate gradient methods are examined with an appropriate initial guess of regularized coefficients. Findings – It has been shown that in case of sparse fatigue life measurements, linear regression results may not have continuous dependence on experimental data and measurement error could lead to misinterpretations of the solution. Therefore from engineering safety point of view, utilizing regularization method could successfully reduce the influence of measurement noise without significantly distorting the fatigue life distribution. Originality/value – An excellent initial guess for mixed iterative-direct algorithm is introduced and it has been shown that the combination of Newton iterative approach and Morozov discrepancy principle is one of the interesting strategies for determination of regularization parameter having an excellent rate of convergence. Moreover since iterative methods are known to be an attractive alternative to Tikhonov regularization, four gradient descend methods are examined here for regularization of the linear regression problem. It has been found that all of gradient decent methods with an appropriate initial guess of regularized coefficients have an excellent convergence to Tikhonov-Morozov regularization results.

scholarly journals Trajectory Sensitivity Method and Master-Slave Synchronization to Estimate Parameters of Nonlinear Systems

2009 ◽  
Vol 2009 ◽  
pp. 1-14 ◽  
Author(s):  
Elmer P. T. Cari ◽  
Edson A. R. Theodoro ◽  
Ana P. Mijolaro ◽  
Newton G. Bretas ◽  
Luis F. C. Alberto
Keyword(s):  
Parameter Estimation ◽  
Nonlinear Systems ◽  
Estimation Algorithm ◽  
Initial Guess ◽  
Measurement Noise ◽  
Conditional Test ◽  
Trajectory Sensitivity ◽  
Parameter Estimation Algorithm ◽  
Sensitivity Method ◽  
True Values

A combination of trajectory sensitivity method and master-slave synchronization was proposed to parameter estimation of nonlinear systems. It was shown that master-slave coupling increases the robustness of the trajectory sensitivity algorithm with respect to the initial guess of parameters. Since synchronization is not a guarantee that the estimation process converges to the correct parameters, a conditional test that guarantees that the new combined methodology estimates the true values of parameters was proposed. This conditional test was successfully applied to Lorenz's and Chua's systems, and the proposed parameter estimation algorithm has shown to be very robust with respect to parameter initial guesses and measurement noise for these examples.

Longitudinal Control of Automotive Vehicles in Close-Formation Platoons

1991 ◽  
Vol 113 (2) ◽  
pp. 231-241 ◽  
Author(s):  
S. E. Shladover
Keyword(s):  
Control System ◽  
Simulation Model ◽  
Control Systems ◽  
System Performance ◽  
Measurement Noise ◽  
Longitudinal Control ◽  
Nonlinear Simulation ◽  
Quantitative Results ◽  
External Forces ◽  
Technical Considerations

The capacity and safety of freeways can potentially be increased substantially if the vehicles are operated in platoons, using automatic longitudinal control systems to maintain very small spacings (of the order of 1 meter) between vehicles. This paper explains many of the technical considerations in the design of such control systems, employing a general nonlinear simulation model to develop quantitative results. The effects on control system performance of external forces, process and measurement noise, and sampling and quantization of measurements are shown. The importance of acceleration and jerk limits is demonstrated, and examples are used to illustrate how the control system must be designed to accommodate variations in the severity of the maneuvers it is expected to execute, as well as variations in propulsion system dynamics.

scholarly journals Efficient Load Sampling for Worst-Case Structural Analysis Under Force Location Uncertainty

2018 ◽  
Author(s):  
Yining Wang ◽  
Erva Ulu ◽  
Aarti Singh ◽  
Levent Burak Kara
Keyword(s):  
Structural Analysis ◽  
Design Method ◽  
Critical Force ◽  
Element Analysis ◽  
Worst Case ◽  
Normal Forces ◽  
Location Uncertainty ◽  
Simple Regression Model ◽  
Force Contact ◽  
External Forces

An important task in structural design is to quantify the structural performance of an object under the external forces it may experience during its use. The problem proves to be computationally very challenging as the external forces’ contact locations and magnitudes may exhibit significant variations. We present an efficient analysis approach to determine the most critical force contact location in such problems with force location uncertainty. Given an input 3D model and regions on its boundary where arbitrary normal forces may make contact, our algorithm predicts the worst-case force configuration responsible for creating the highest stress within the object. Our approach uses a computationally tractable experimental design method to select number of sample force locations based on geometry only, without inspecting the stress response that requires computationally expensive finite-element analysis. Then, we construct a simple regression model on these samples and corresponding maximum stresses. Combined with a simple ranking based post-processing step, our method provides a practical solution to worst-case structural analysis problem. The results indicate that our approach achieves significant improvements over the existing work and brute force approaches. We demonstrate that further speedup can be obtained when small amount of an error tolerance in maximum stress is allowed.

A SEM and Light Microscope Study of the Epidermal Leaf Structures of the Carnivorous Plant, Sarracenia purpurea, L.

1971 ◽  
Vol 29 ◽  
pp. 358-359
Author(s):  
B. J. Panessa ◽  
J. F. Gennaro
Keyword(s):  
Methylene Blue ◽  
Toluidine Blue ◽  
Outer Surface ◽  
Microscope Study ◽  
Light Microscope ◽  
Carnivorous Plant ◽  
Sarracenia Purpurea ◽  
Inner Surface

Tissue from the hood and sarcophagus regions were fixed in 6% glutaraldehyde in 1 M.cacodylate buffer and washed in buffer. Tissue for SEM was partially dried, attached to aluminium targets with silver conducting paint, carbon-gold coated(100-500Å), and examined in a Kent Cambridge Stereoscan S4. Tissue for the light microscope was post fixed in 1% aqueous OsO4, dehydrated in acetone (4°C), embedded in Epon 812 and sectioned at ½u on a Sorvall MT 2 ultramicrotome. Cross and longitudinal sections were cut and stained with PAS, 0.5% toluidine blue and 1% azure II-methylene blue. Measurements were made from both SEM and Light micrographs.The tissue had two structurally distinct surfaces, an outer surface with small (225-500 µ) pubescent hairs (12/mm2), numerous stoma (77/mm2), and nectar glands(8/mm2); and an inner surface with large (784-1000 µ)stiff hairs(4/mm2), fewer stoma (46/mm2) and larger, more complex glands(16/mm2), presumably of a digestive nature.

Gastric Ulcers Produced by Cisplatin

1981 ◽  
Vol 39 ◽  
pp. 582-583
Author(s):  
S.K. Aggarwal ◽  
J. San Antonio
Keyword(s):  
Electron Microscopy ◽  
Single Dose ◽  
Side Effects ◽  
Antitumor Agent ◽  
Gastric Ulcers ◽  
Enzyme Cytochemistry ◽  
Intestinal Toxicity ◽  
Ovarian Cancers ◽  
Inner Surface

Cisplatin (cis-dichlorodiammineplatinum(II)) a potent antitumor agent is now available for the treatment of testicular and ovarian cancers. It is however, not free from its serious side effects including nephrotoxicity, gastro intestinal toxicity, myelosuppression, and ototoxicity. Here we now report that the drug produces peculiar bloating of the stomach in rats and induces acute ulceration.Wistar-derived rats weighing 200-250 g were administered cisplatin(9 mg/kg) ip as a single dose in 0.15 M NaCl. After 3 days the animals were sacrificed by decapitation. The stomachs were removed, the contents analyzed for pepsin and acidity. The inner surface was examined with a dissecting microscope after a moderate stretching for ulcers. Affected areas were fixed and processed for routine electron microscopy and enzyme cytochemistry.The drug treated animals kept on food and water consistently showed bloating and lesions (Fig. 1) with a frequency of 6-70 ulcers in the rumen section of the stomachs.

Quantitative analysis by reconstruction of HREM focal series

1994 ◽  
Vol 52 ◽  
pp. 740-741
Author(s):  
W. Coene ◽  
A. Thust ◽  
M. Op de Beeck ◽  
D. Van Dyck
Keyword(s):  
Phase Retrieval ◽  
Image Plane ◽  
Initial Guess ◽  
Recursive Least Squares ◽  
Objective Lens ◽  
Electron Wave ◽  
Electron Sources ◽  
Original Algorithm ◽  
Coherent Field ◽  
Direct Interpretation

Compared to conventional electron sources, the use of a highly coherent field-emission gun (FEG) in TEM improves the information resolution considerably. A direct interpretation of this extra information, however, is hampered since amplitude and phase of the electron wave are scrambled in a complicated way upon transfer from the specimen exit plane through the objective lens towards the image plane. In order to make the additional high-resolution information interpretable, a phase retrieval procedure is applied, which yields the aberration-corrected electron wave from a focal series of HRTEM images (Coene et al, 1992).Kirkland (1984) tackled non-linear image reconstruction using a recursive least-squares formalism in which the electron wave is modified stepwise towards the solution which optimally matches the contrast features in the experimental through-focus series. The original algorithm suffers from two major drawbacks : first, the result depends strongly on the quality of the initial guess of the first step, second, the processing time is impractically high.

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