Photometric Calibration for Stereo Camera with Gamma-like Response Function in Direct Visual Odometry

Direct visual odometry algorithms assume that every frame from the camera has the same photometric characteristics. However, the cameras with auto exposure are widely used outdoors as the environment often changes. The vignetting also affects the pixel’s brightness on different frames, even if the exposure time is fixed. We propose an online vignetting correction and exposure time estimation method for stereo direct visual odometry algorithms. Our method works on a camera that has a gamma-like response function. The inverse vignetting function and exposure time ratio between neighboring frames are estimated. Stereo matching is used to select correspondences between the left image and right image in the same frame at the initialization step. Feature points are used to pick the correspondences between different frames. Our method provides static correction results during the experiments on datasets and a stereo camera.

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An Improved Travel Time Estimation Method without Signal Timing Data Based on an Individual Probe Car

CICTP 2016 ◽

10.1061/9780784479896.020 ◽

2016 ◽

Author(s):

Huibing Li ◽

Zhijie Bao ◽

Geng Yang ◽

Chao Peng ◽

Lihua Luo

Keyword(s):

Travel Time ◽

Estimation Method ◽

Time Estimation ◽

Signal Timing ◽

Travel Time Estimation ◽

Individual Probe ◽

Timing Data ◽

Probe Car

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Road Roughness Estimation Based on the Vehicle Frequency Response Function

Actuators ◽

10.3390/act10050089 ◽

2021 ◽

Vol 10 (5) ◽

pp. 89

Author(s):

Qingxia Zhang ◽

Jilin Hou ◽

Zhongdong Duan ◽

Łukasz Jankowski ◽

Xiaoyang Hu

Keyword(s):

Frequency Response ◽

Response Function ◽

Frequency Response Function ◽

Gaussian White Noise ◽

Estimation Method ◽

Time Shift ◽

Ride Quality ◽

The Road ◽

Road Roughness ◽

Measured Response

Road roughness is an important factor in road network maintenance and ride quality. This paper proposes a road-roughness estimation method using the frequency response function (FRF) of a vehicle. First, based on the motion equation of the vehicle and the time shift property of the Fourier transform, the vehicle FRF with respect to the displacements of vehicle–road contact points, which describes the relationship between the measured response and road roughness, is deduced and simplified. The key to road roughness estimation is the vehicle FRF, which can be estimated directly using the measured response and the designed shape of the road based on the least-squares method. To eliminate the singular data in the estimated FRF, the shape function method was employed to improve the local curve of the FRF. Moreover, the road roughness can be estimated online by combining the estimated roughness in the overlapping time periods. Finally, a half-car model was used to numerically validate the proposed methods of road roughness estimation. Driving tests of a vehicle passing over a known-sized hump were designed to estimate the vehicle FRF, and the simulated vehicle accelerations were taken as the measured responses considering a 5% Gaussian white noise. Based on the directly estimated vehicle FRF and updated FRF, the road roughness estimation, which considers the influence of the sensors and quantity of measured data at different vehicle speeds, is discussed and compared. The results show that road roughness can be estimated using the proposed method with acceptable accuracy and robustness.

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Reasoning: Source of Variability in the Boothroyd and Dewhurst Assembly Time Estimation Method

Volume 5: 6th International Conference on Micro- and Nanosystems; 17th Design for Manufacturing and the Life Cycle Conference ◽

10.1115/detc2012-71075 ◽

2012 ◽

Cited By ~ 4

Author(s):

Essam Namouz ◽

Joshua D. Summers ◽

Gregory M. Mocko

Keyword(s):

Engineering Students ◽

Large Range ◽

Estimation Method ◽

Time Estimation ◽

Handling Time ◽

Time Estimate ◽

Time Analysis ◽

Assembly Time ◽

Time Estimates ◽

Initial Results

This paper evaluates the effect of making a subjective decision in a design for assembly time analysis. An example is found in the first set of questions for estimating handling time of a part the user chose “parts are easy to grasp and manipulate” as opposed to “parts present handling difficulties”. The subjectivity is explored through a study of assembly time estimates generated by a class of mechanical engineering students in the time analysis of a clicker pen based on the Boothroyd and Dewhurst estimation method. The assembly times calculated by the class ranged from a minimum of 23.64 seconds to a maximum of 44.89 seconds (range of 21.25 seconds). This large range in results serves as motivation in determining the effect that answering a subjective decision has on the resulting assembly time estimate. Initial results indicate that not answering the first level of subjective questions will result in assembly time estimate within 15% of the time had the subjective question been answered. The probability density plots of the time estimates also indicates that 63% of the time, the estimated assembly time without making the subjective decision will fall within the normal distribution had the subjective decision been made. This provides evidence that there is an opportunity to reduce the amount of subjective questions that a user must answer to estimate the assembly time of a product.

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Time Estimation Methods—Do They Influence Prospective Duration Estimates?

Perception ◽

10.1068/p220091 ◽

1993 ◽

Vol 22 (1) ◽

pp. 91-101 ◽

Cited By ~ 100

Author(s):

Dan Zakay

Keyword(s):

Information Processing ◽

Positive Relationship ◽

Negative Relationship ◽

Estimation Method ◽

Time Estimation ◽

Estimation Methods ◽

Clock Time ◽

Processing Load ◽

Attentional Model ◽

Time Length

The validity of an attentional model of prospective time estimation was tested in three experiments. In the first experiment two variables were manipulated: (1) nontemporal information processing load during the estimated interval, and (2) time estimation method, ie production of time simultaneously with the performance of a second task, or reproduction of time immediately upon termination of a task whose duration has to be measured. As predicted, a positive relationship between produced time length and information processing load demanded by a simultaneous task, and a negative relationship between reproduced time length and information processing load during the estimated interval, were found. The results were replicated in a second experiment in which verbal estimates of time were also measured and the objective duration of the estimated interval was varied. The pattern of results obtained for verbal estimates was similar to that obtained for reproduced ones. The results of a third experiment indicated that produced and reproduced times were positively correlated with clock time. The results are interpreted as supporting an attentional model of prospective time estimation.

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Robust surface matching by integrating edge segments

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsannals-ii-5-203-2014 ◽

2014 ◽

Vol II-5 ◽

pp. 203-210

Author(s):

N. Kochi ◽

T. Sasaki ◽

K. Kitamura ◽

S. Kaneko

Keyword(s):

High Precision ◽

High Speed ◽

Stereo Matching ◽

Direct Consequence ◽

Surface Matching ◽

Matching Process ◽

Edge Matching ◽

Edge Surface ◽

Image Area ◽

Left Image

This paper describes a novel area-based stereo-matching method which aims at reconstructing the shape of objects robustly, correctly, with high precision and with high density. Our goal is to reconstruct correctly the shape of the object by comprising also edges as part of the resulting surface. For this purpose, we need to overcome the problem of how to reconstruct and describe shapes with steep and sharp edges. Area-based matching methods set an image area as a template and search the corresponding match. As a direct consequence of this approach, it becomes not possible to correctly reconstruct the shape around steep edges. Moreover, in the same regions, discontinuities and discrepancies of the shape between the left and right stereo-images increase the difficulties for the matching process. In order to overcome these problems, we propose in this paper the approach of reconstructing the shape of objects by embedding reliable edge line segments into the area-based matching process with parallax estimation. We propose a robust stereo-matching (the extended Edge TIN-LSM) method which integrates edges and which is able to cope with differences in right and left image shape, brightness changes and occlusions. The method consists of the following three steps: (1) parallax estimation, (2) edge-matching, (3) edge-surface matching. In this paper, we describe and explain in detail the process of parallax estimation and the area-based surface-matching with integrated edges; the performance of the proposed method is also validated. The main advantage of this new method is its ability to reconstruct with high precision a 3D model of an object from only two images (for ex. measurement of a tire with 0.14 mm accuracy), thus without the need of a large number of images. For this reason, this approach is intrinsically simple and high-speed.

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