High-speed Stereo Vision System Research Articles

Modeling and experimental study of tire deformation characteristics under high-speed rolling condition

Tire rolling deformation consists of valuable information for vehicle control and tire development applications. To gain insight into this deformation, both model-based and tire sensor-based approaches have been investigated in previous studies. However, existing tire models oversimplified the pressure distribution in the tire-road contact due to a lack of related experiment data especially for deformations of the tire at high rolling speeds. Meanwhile, the tire sensing method requires extensive experiments and cannot be directly used within vehicle simulations. For resolving the above issues, this paper proposes a combined approach for studying tire rolling deformation. Specifically, the flexible ring tire model (FRTM) is extended with a realistic, dynamic pressure distribution to provide more accurate predictions of the rolling tire deformation under various operation conditions. Meanwhile, a three-dimensional high-speed stereo vision system has been set up together with an optimized digital image correlation (DIC) method to measure the deformation of high-speed rolling tires. The experimental results reveal that rolling tires experience an eccentric deformation and an anti-symmetric deformation in the radial and tangential directions, respectively. Additionally, it was observed that the vertical load has a more substantial influence than the tire pressure on rolling deformation. The capability of the improved ring tire model to describe these observed phenomena has been validated through comparisons between simulations and measurements.

High-speed 3D digital image correlation for measuring tire rolling resistance coefficient

A novel method is proposed to measure rolling resistance coefficient of high-speed running tire. Compared with the existing rolling resistance coefficient measurement methods, the new approach is non-contact measurement based on the calculation of relative flexible principal strain rate. A high-speed stereo vision system is utilized to capture the transient deformation of high-speed rolling tire. In order to better understand the full-field dynamic distribution characteristics of high-speed rolling tire, an improved digital image correlation is proposed to accurately measure the relative coupled displacement and the relative flexible deformation. The rolling resistance mechanism of high-speed rolling tire could be clearly observed from the relative flexible principal strain rate distribution. On this basis, the tire rolling radius and rolling offset could be acquired by analyzing the relative displacement distribution and the relative flexible principal strain rate, and then the rolling resistance coefficient of high-speed rolling tire could be calculated. The experimental results demonstrate that it is feasible to measure the resistance coefficient of high-speed rolling tire by using high-speed 3D digital image correlation.

High-speed 3D digital image correlation for rolling deformation of a tire sidewall and measuring dynamic contact patch length.

Tires play a vital role in a vehicle's operational stability, comfort, and security. However, due to the influence of test equipment and tire operating conditions, the perception of rolling tire characteristics is still in the stage of gradual improvement, especially the analysis of sidewall rolling deformation and dynamic contact peculiarities of tires/road interactions, which has restricted the analysis of rolling energy dissipation and the accurate observation of tire forces. In this paper, the high-speed stereo-vision system was created by high-speed cameras, and the relative rigid and flexible displacement, strain, and trajectory trend of marker points and the real-time global displacement field of the sidewall during the tire-rolling cycle were acquired utilizing the improved digital image correlation algorithm under different rolling velocities. Meanwhile, the periodic dissipation of the strain concentration region was observed, and the phenomenon of strain resonance appeared at the overlap of the periods. The relative flexibility strain and shear strain of the marker point were obtained on the plane element, which resulted in the relative flexibility major principle strain of the plane element, and then it achieved recognition of the leading and trailing points of the contact patch and the accurate measurement of dynamic contact patch length.

Correction of start-up time difference-induced measurement errors of a high-speed binocular stereovision system

In a high-speed stereovision system, high-speed cameras (HSCs) are used to record images and time information, and the measurement accuracy depends on the time precision of the cameras. When two HSCs are used in a binocular stereovision system, the image acquisitions of both cameras are unlikely to start simultaneously. The images that are supposed to be captured at the “same time” may record different states of the test object during an experiment, which will cause measurement errors. In this work, a theoretical model was established to correlate the start-up time difference (STD) and the STD-induced measurement errors of a binocular stereovision system. A simulation of the deflection of a cantilever beam verified the accuracy of the theoretical model. A suggestion of the experimental layout was discussed to reduce the STD-induced measurement errors in one direction, and a method was proposed to correct the STD-induced measurement errors. The effectiveness of the correction method was validated by two experiments, that is, the trajectory of a marker point and the out-of-plane deformation of a bubble. The results showed that the absolute errors of the marker point trajectory were almost negligible and the deformation contours of the bubble were more symmetric after the correction. This correction method should be useful for three-dimensional measurements of physical quantities using a binocular stereovision system.

Tracking a Golf Ball With High-Speed Stereo Vision System

Professional long drivers can hit golf balls to a speed of up to 350 km/h. Extremely short exposure time is required to capture the objects moving that fast without blur. The very high frame rate is also required to capture the sufficient sequence of object movements within the field of view in order to predict trajectory, which means a sacrifice in frame image resolution at fixed data throughput. This paper presents a high-speed stereo vision system that is able to track the golf ball motion at the speed of up to 360 km/h under normal indoor lighting conditions. Binocular camera operated at 810 frames/s with 35- $\mu \text{s}$ exposure time, requiring no additional strobe lights in order not to compromise user experiences. Ball markers were designed for spin measurement. To detect balls and identify markers from highly underexposed low resolution images, new algorithms were developed and implemented on field-programmable gate array board with an advanced RISC machines CPU. The experimental results showed high detection rate and high accuracy with overall processing time less than 300 ms.

Scaling of the deformation histories for clamped circular plates subjected to blast loading by buried charges

Dimensional analysis is performed to develop the appropriate parameters to guide the design of a set of scaled experimental configurations. Using the scaled experimental configurations, buried blast loading of scaled small structures is performed by detonation of scaled explosive charges buried in saturated sand. To assess the quality of the predictions for the response of the scaled structures, high-speed stereo-vision system is employed to quantify the transient dynamic plate response over a substantial portion of the structure. Results are reported for surface deformations during the blast loading process, including 3D surface displacements, surface strain components, surface velocity and acceleration components for the out-of-plane displacement field and surface strain rate components. Data presented in the form of scaled measurement for both plates indicates that both (a) temporal variations and (b) spatial variations are in very good agreement throughout the measurement period. Even for conditions where the buried explosive is quite small and the depth of burial is shallow, results clearly show that scaling of small specimen buried blast loading experiments can be applied to quantitatively predict the dynamic response of larger structures.

Deformation Scaling of Circular Plates Subjected to Dynamic Loading

Dimensional analysis is performed to develop the appropriate parameters to guide the design of a set of scaled experimental configurations. Using the scaled experimental configurations, blast loading of the structures is developed by detonation of scaled explosive charges buried in saturated sand. To assess the quality of the scaling predictions for the response of the scaled structures, high-speed stereo-vision system is employed to quantify the transient dynamic plate response over a substantial portion of the structure. Results are reported for the out-of-plane surface deformations, including acceleration and velocity fields, during the blast loading process. Data presented in the form of scaled measurement for both plates indicates that both (a) temporal variations and (b) spatial variations are in very good to excellent agreement throughout the measurement period.

1A1-A11 二眼駆動鏡面式視線制御による高速ステレオビジョンシステム(3次元計測/センサフュージョン(1))

1A1-A11 二眼駆動鏡面式視線制御による高速ステレオビジョンシステム(3次元計測/センサフュージョン(1))

Three-dimensional measurement of CFRP deformation during high-speed impact loading

The deformation of carbon fiber reinforced plastics (CFRPs) caused by projectile impact governs the absorption or dissipation of kinetic energy of the projectile. However, three-dimensional (3D) numerical information about the CFRP deformations caused by the projectile impact is not yet available. Therefore, a 3D measurement was conducted to evaluate the deformation process and deformation behavior of the CFRPs under high-velocity projectile impact, and to subsequently evaluate the performance of the CFRPs. CFRPs having two different stacking sequences were used as the specimens. For measuring the deformation, a high-speed stereovision system comprised of two high-speed video cameras was adopted. An SUJ-2 sphere projectile was impacted against a specimen plate using a light-gas accelerator at an impact velocity of approximately 175 m/s, and the deformation was recorded by synchronously capturing the images using this system. The captured images were converted to stereo images by a 3D correlation method. The stereo images clearly revealed numerical differences in the deformation of the CFRPs having different stacking sequences. The result accuracy of the 3D measurement was verified by comparing their results with the direct measurement results. Moreover, the stereo images corresponded to the results from a numerical simulation of the CFRP deformations, which both qualitatively and quantitatively confirms the validity of the simulation. This 3D measurement method is a powerful and useful tool for evaluating the performance of CFRPs during high-velocity projectile impact.

Development of a Low-Cost, High-Speed Stereo Vision System Using a CMOS Imager and DSP

This article presents the development of a low-cost, high-speed stereo vision system for embedded use employing a mass-produced CMOS imager and a commercially available DSP. We use the system to acquire an image of 96×96 pixels in a period of 1 ms. We embed a read region movement control and a target track function into the system and successfully track a target point within a period of 3 ms. The difference between this high-speed stereo vision system and traditional ones lies in that this system is intended to be used even in a small-scale control system using a microcomputer. We limit the capacity of the image memory in which acquired pixel data is temporarily stored and performed real time processing. As a result, we eliminate frame memory and thus simplify its corresponding circuit. This allows the system to be reduced in size, power consumption, and cost, thereby making the system appropriate for embedded devices, batterypowered robots, and the like.

Development of a Low Cost High Speed Stereo Vision System for Embeded Use Using CMOS Imagers and DSP

We developped a low cost high speed stereo vision system for embeded use using CMOS imagers on the market and TI DSP(Digital Signal Processor) board that can capture subframe images in shorter period than video rate. Because the proposed system is small, low enegy consumption and low cost, it is suitable for embeded use or small autonomous mobile robot. Some experiments demonstrate that this vision system can capture 96[pixel]×96[pixel] image in 1[ms] period and detect the target position and track the target in 3[ms] period.

Visual Measurement and Prediction of Ball Trajectory for Table Tennis Robot

A high-speed stereovision system with two smart cameras is presented to track a table tennis ball, which adopts a distributed parallel processing architecture based on a local area network. A set of novel algorithms with little computation and good robustness running in the smart cameras is also proposed to recognize and track the ball in the images. A computer receives the image coordinates of the ball from the cameras via the local area network and computes its 3-D positions in the working frame. Then, the flying trajectory of the ball is estimated and predicted according to the measured positions and the flying and rebound models. The main motion parameters of the ball such as the landing point and striking point are calculated from its predicted trajectory. Experimental results show that the developed image-processing algorithms are robust enough to distinguish the ball from a complex dynamic background. The predicted landing point and striking point of the ball have satisfactory precision.

Three-dimensional measurement of CFRP deformation during high-speed impact loading

The deformation of carbon fiber reinforced plastics (CFRPs) caused by projectile impact governs the absorption or dissipation of kinetic energy of the projectile. However, three-dimensional (3D) numerical information on CFRP deformations caused by projectile impact is not yet available. Therefore, we conducted 3D measurements to evaluate the deformation process and deformation behavior of CFRPs under high-velocity projectile impact, to subsequently evaluate the performance of CFRPs. We used CFRP specimens with two different stacking sequences. For measuring the deformation, we used a high-speed stereovision system comprising two high-speed video cameras. An SUJ-2 sphere projectile was impacted against a specimen plate using a light-gas accelerator at an impact velocity of approximately 175 m/s, and the deformation was recorded by synchronously capturing images using this system. The captured images were converted to stereo images by a 3D correlation method. The stereo images clearly revealed numerical differences in the deformations of the CFRPs with different stacking sequences. We verified the accuracy of results of the 3D measurement by comparing with results of another measurement methodology. Moreover, the stereo images corresponded to results of a numerical simulation of CFRP deformations, which confirms the validity of the simulations both qualitatively and quantitatively. This 3D measurement method is a powerful and useful tool for evaluating the performance of CFRPs during high-velocity projectile impact.

Application of 3D image correlation for full-field transient plate deformation measurements during blast loading

A high-speed stereo-vision system is employed to quantify dynamic material response during buried blast loading. Deformation measurements obtained using 3D image correlation of synchronized, patterned stereo-vision images obtained with an inter-frame time in the range 16 μs ≤ t ≤ 40 μs indicate that (a) buried blast loading initially induces highly localized material response directly under the buried blast location, with severity of the blast event a strong function of depth of explosive burial, (b) for relatively shallow (deep) depth of explosive burial, plate surface velocities and accelerations exceed 220 m s −1 (100 m s −1) and 6 × 10 6 m s −2 (1.5 × 10 6 m s −1) during the first 30 μs (80 μs) after detonation, respectively. In addition, full-field plate deformation measurements demonstrate that the specimen experienced (c) measured effective strains exceeding 8% (5%) and effective strain rates exceeding 4000 s −1 (1500 s −1) during the first 50 μs (80 μs), respectively and (d) a blast-induced, circularly symmetric, transient bending wave was induced in the plate that travels with radial velocity of Mach 2 (1.25) during blast loading. By combining the Cowper–Symonds constitutive relation with full-field strain and strain rate measurements, well-defined yield boundaries are evident on the plate surface during blast loading; the presence of spatial gradients in yield stress has the potential to affect plate failure processes during transient blast loading events.