Slope Roughness Research Articles

Dynamic modeling of wheeled biped robot and controller design for reducing chassis tilt angle

Abstract The wheeled-legged robot combines the advantages of wheeled and legged robots, making it easier to assist people in completing repetitive and time-consuming tasks in their daily lives. This paper presents a study on the kinematic and dynamic modeling, as well as the controller design, of a wheeled biped robot with a parallel five-bar linkage mechanism as its leg module. During the motion of the robot, the robot relies on the tilt angle of the inverted pendulum, and this angle often results in the tilting of the chassis of the robot, presenting challenges for the installation of upper-body payloads and sensor systems. The controller proposed in this paper, which is developed by decoupling the primary motions of the robot and designing a multi-objective, multilevel controller, addresses this issue. This controller employs the pendulum pitch angle of the equivalent inverted pendulum model as the control variable and compensates for the chassis tilt angle (CTA). This control method can effectively reduce the CTA of such robots and eliminate the need for additional counterweights. It also provides a more spacious structural design for accommodating upper-body devices. The effectiveness of this control framework is verified through variable height control, walking on flat ground, and carrying loads over rough terrain and slopes.

Active illumination mode with checkerboard pattern in focus variation microscopy: Analysis and application

Optical measurement methods for surface topography offer the advantages of high accuracy, rapid measurement, and non-destructiveness. Each method has its own suitable application scenarios. Among them, focus variation microscopy is extensively employed in precision manufacturing, aerospace, and medical industries due to its ability to measure rough and large slopes surfaces. However, since the measurement depends on local grayscale differences between focused and blurred images, it cannot measure surfaces with low reflectivity or insufficient texture information. In this work, we propose an active illumination mode for focus variation method that utilizes a digital micromirror device (DMD) to generate a checkerboard pattern. This method introduces additional texture information, resulting in a usable local gradient of image grayscale. Additionally, we analyze the selection criteria for the checkerboard pattern parameters, including the period and light-dark ratio. Furthermore, measurements of two standard steps with different heights demonstrate that the measurement repeatability of the proposed method can reach the nanometer level, rendering it suitable for high-precision measurements. More importantly, the measurement noise results indicate significantly superior performance of active illumination mode compared to the uniform illumination mode. Finally, we reconstruct the surface topography of the microchannels in a microfluidic chip through the encapsulation layer, demonstrating the feasibility of the proposed method.

Surface roughness and wave slope statistics from the multi-spectral polarimetric imaging of the ocean surface

The polarization of light in Ocean Color (OC) applications provides important information about atmospheric parameters, water composition, and the ocean surface. The Stokes vector components and the degree of linear polarization of light contain useful information about the air-water interface, including ocean surface roughness. We present polarimetric measurements and analysis of the ocean wave slopes at several bands. Data is acquired with a Teledyne DALSA camera, which uses a polarizer-on-chip focal plane of 1232 × 1028 super-pixels, where each pixel is made of four subpixels with 0-, 90-, 45- and 135-degrees orientation of polarization. We present a modified version of the Polarization Slope Sensing (PSS) technique [Zappa et al., 2008] for the non-contact detection of wave slopes and demonstrate a good performance of the updated algorithm in several conditions where the original technique was not applicable. Derived wave slopes are presented for various aquatic and atmospheric environments, including during VIIRS Cal/Val cruises and at a near-shore pier. The results are shown to be consistent with theoretical wave slope models.

Model Test Study on Rock Rolling Characteristics

In order to study the influence of falling rock shapes on their rolling characteristics and to determine the optimization of falling rock protection design, a series of research experiments were conducted. Model experiments were designed to explore the rolling characteristics of rockfalls with different shapes. Based on the experimental results, it was found that the slenderness ratio, center of gravity, and rotational inertia of the rockfalls can affect their rolling characteristics, leading to swaying and changing the rolling axis during the rolling process, thereby affecting their rolling speed. Building upon these findings, an analysis of the formation mechanism of rolling resistance was conducted. It was determined that the primary cause of energy loss was the rolling resistance arm formed with the rolling surface during rockfall motion. A shape parameter was proposed to quantify the rolling resistance. These parameters were incorporated into a kinematic formula that considered the influence of rockfall shape, slope, and slope roughness on the rolling speed. Combined with the offset and initial position of the rockfall, the formula could be used to calculate the rolling speed and impact energy in the rolling region at any position in the region. The calculation formula was validated using model experimental data, and the results showed that the error between the experimental and calculated values was small. The error was corrected based on the experimental data. After on-site testing and verification, it could provide reference for the management of rockfall disasters.

Effects of tillage microrelief units on splash erosion: A case study from the Loess Plateau, in China

A tillage microrelief unit is the smallest spatially discontinuous area unit of tillage microrelief. Understanding the impact of tillage microrelief units on splash erosion is essential for selecting suitable tillage measures and employing soil and water conservation practices. The objective of this study was to investigate the characteristics and mechanisms of splash erosion under different tillage microrelief units in various directions and distances using the rainfall simulation experiment in the soil landscape of the Loess Plateau region in China, characterized primarily by sloping farmland as the main land use type. Three typical microrelief units, namely, artificial digging (AD), contour tillage (CT), and straight slope conditions (SSC) were designed at 0°, 3°, 5°, 10°, 15°, and 20° slopes. Tillage microrelief units with high surface roughness produced more splash erosion than flat lands. Further, the highest surface roughness increased the total splash amount by 102% relative to flat lands. The tillage microrelief unit itself was elevated with a certain slope, which increased the downslope splash of CT, SSC, and AD by 121%, 173%, and 11%, respectively. Different surface roughness values and slopes under different microrelief units were used to determine the amount of splash erosion. The results showed that the total splash amount responded significantly (P < 0.01) to the interaction between surface roughness and slope, and the sensitivity to roughness was higher than that to slope. According to the single-factor analysis, the surface roughness of all slopes significantly influenced the amount of splash erosion. Furthermore, the sensitivity of the tillage microrelief unit to the slope decreased because of the high slope under high surface roughness. Overall, the results of this study showed that in different tillage microrelief units of slopes in the Loess Plateau, SSC and CT significantly increased the outward splash erosion in this area, while AD significantly decreased the outward splash erosion. Moreover, slope did not have a considerable influence.

Apron and macro roughness as scour countermeasures downstream of block ramps

ABSTRACT A block ramp is a grade-control structure commonly used to stabilize the river bed with a high efficiency of energy dissipation. This study investigates the effects of using macro roughness and a downstream apron as scour countermeasures on the maximum scour depth downstream of block ramps in straight rivers. All the experiments have been carried out in a horizontal channel and in clear water conditions (no sediment transport). A wide range of hydraulic conditions including densimetric Froude numbers, water drop heights, and tailwater depths for three different rough ramp slopes (1 V:3 H, 1 V:5 H, and 1 V:7 H) was tested. The results have been compared with the results from a smooth ramp (no roughness), which has been considered as a reference. Results show that both macro roughness on the ramp and downstream aprons work well as scour countermeasures while as a comparison, using macro roughness (big-size stones) on the ramp is more effective than downstream aprons to reduce the scour depth. The other finding of this study shows that increasing the downstream apron decreases the length of the scour hole, consequently decreasing the volume of eroded material.

Effect of Small-Scale Topographical Variations and Fetch from Roughness Elements on the Stable Boundary Layer Turbulence Statistics

Understanding the influence of roughness and terrain slope on stable boundary layer turbulence is challenging. This is investigated using observations collected from October to November of 2018 during the Stable Atmospheric Variability ANd Transport (SAVANT) field campaign conducted in a shallow sloping Midwestern field. We analyze the turbulence velocity scale and its variation with the mean wind speed using observations up to 10–20 m on four meteorological towers located along a shallow gully. The roughness length for momentum over this complex terrain varied with wind direction from 0.0049 m to a maximum of 0.12 m for winds coming through deciduous trees present in the field. The variation of the turbulence velocity with wind speed shows a transition from a weak wind regime to a stronger wind regime, as reported by past studies. This transition is not observed for winds coming from the tree area, where turbulence is enhanced even for weak wind speeds. For weak stratification and stronger winds, the turbulent velocity scale increased with an increase in roughness while the terrain slope is seen to have a weak influence. The sizes of the dominant turbulent eddies seen from the vertical velocity power spectra are observed to be larger for winds coming through the tree area. The turbulence enhancement by the trees is found to be strong within a fetch distance of 7 times the tree height and not observable at 16 times of the tree height.

Study on the influence of slit structure on safe and efficient directional fracture blasting effect

In order to study the influence of slit structure on the blasting effect of slit charge, the super dynamic strain test system and photographic equipment were used to study the dynamic response of slit charge blasting and the distribution of blasting cracks under different slit shapes and slit angles. The results show that changing the shape of the slit does not make the energy-gathering and damage-reducing blasting effect of the slit cartridge disappear, but it will affect its effect. Compared with the round hole slit, the peak strain in the slit direction of the strip slit cartridge blast is larger, the directional crack forming is more obvious, and the blasting effect is better. The energy accumulation and loss reduction effect of the blasting of the strip slotted cartridge increase first and then decrease with the increase of the slit angle. When the slit angle is 20°, the energy accumulation and loss reduction effect of strip slit charge blasting are the largest, the distribution of blasting cracks is the best, and the directional fracture blasting effect of slit charge is the best. Finally, based on the research results of model test, combined with the actual situation of the construction site, the slotted cartridge is applied to the pre-splitting blasting of open-pit slope. Compared with the ordinary cartridge pre-splitting blasting, the slope roughness after blasting is reduced by 46.2%, the half-hole rate of blast hole is increased by 20.5%, the blasting vibration intensity is reduced by 60.3%, and the directional fracture control blasting effect is good.

Effect of Surface Roughness and Channel Slope on Hydraulic Jump Characteristics: An Experimental Approach Towards Sustainable Environment

Effect of Surface Roughness and Channel Slope on Hydraulic Jump Characteristics: An Experimental Approach Towards Sustainable Environment

Roughness and Angularity of Fragments from Meteorite Disruption Experiments

In this study, we set out to explore the relationship between fracture roughness and sample strength. We analyze 45 fragments of Aba Panu, Allende, and Tamdakht, three meteorites that have been strength-tested to disruption, to determine whether their shape or texture is correlated with measured compressive strength. A primary goal is to understand whether these exterior properties correlate with more challenging strength-related measurements. We first scan the samples and construct high-fidelity 3D models. The gradient-based angularity index AI g and the rms slope roughness metric θ rms are applied to all nine samples, and their validity and any correlation between them are analyzed. We find that different sample subsets show significant variation in both correlation strength and direction. We also find AI g to be of questionable validity in its application to highly angular samples. Based on our methodology and results, we do not find sufficient separation between the roughness values of samples to allow distinct identification of the three meteorites based on roughness alone. Additionally, neither metric shows a strong correlation with the strength of individual fragments. We do find, however, that the spread of the fragment strength distribution within a given meteorite has some correlation with its average roughness metric. Increased fragment roughness may imply greater structural heterogeneity and therefore potentially weaker behavior at larger sizes. We only have significant data sets for two meteorites, however, which are insufficient to correlate meteorite fracture roughness to meteorite strength in any simple way.

Sensitivity analysis of erosion on the landward slope of an earthen flood defense located in southern France submitted to wave overtopping

Abstract. The study aims to provide a complete analysis framework applied to an earthen dike located in Camargue, France. This dike is regularly submitted to erosion on the landward slope that needs to be repaired. Improving the resilience of the dike calls for a reliable model of damage frequency. The developed system is a combination of copula theory, empirical wave propagation, and overtopping equations as well as a global sensitivity analysis in order to provide the return period of erosion damage on a set dike while also providing recommendations in order for the dike to be reinforced as well as the model to be self-improved. The global sensitivity analysis requires one to calculate a high number of return periods over random observations of the tested parameters. This gives a distribution of the return periods, providing a more general approach to the behavior of the dike. The results show a return period peak around the 2-year mark, close to reported observation. With the distribution being skewed, the mean value is higher and is thus less reliable as a measure of dike safety. The results of the global sensitivity analysis show that no particular category of dike features contributes significantly more to the uncertainty of the system. The highest contributing factors are the dike height, the critical velocity, and the coefficient of seaward slope roughness. These results underline the importance of good dike characterization in order to improve the predictability of return period estimations. The obtained return periods have been confirmed by current in situ observations, but the uncertainty increases for the most severe events due to the lack of long-term data.

Influence of the channel bed slope on Shannon, Tsallis, and Renyi entropy parameters

Abstract Velocity distribution plays a fundamental role in understanding the hydrodynamics of open-channel flow. Among a multitude of approaches, the entropy-based approach holds great promise in achieving a reasonable characterisation of the velocity distribution. In entropy-based methods, the distribution depends on a key parameter, known as the entropy parameter (a function of the time-averaged mean velocity and maximum velocity), that relates to channel characteristics, such as channel roughness and channel bed slopes. The entropy parameter was regarded as constant for lack of experimental evidence, which would otherwise demonstrate if it had any correlation with channel properties. A series of experiments were conducted to collect velocity data in the laboratory flume for seven different values of the channel bed slope. The experimental data analysis revealed dissimilar fluctuations in entropy parameter values with varying bed slopes, with the lowest coefficient of variation in Renyi's (∼0.5%) and the highest in Shannon's case (∼10%). Performance evaluation of the predicted results substantiated good accuracy for all three entropies with the best results of Renyi entropy and lent strong support for using a constant (overall average) value of the entropy parameter for a specific channel cross-section rather than separate values for each channel bed slope.

MODELING MACRO ROUGHNESS WITH A POROUS MEDIA, EXAMPLE OF THE ARTHA BREAKWATER

Regarding the wave climate and urbanisation in the bask country, several coastal structure in that area are submitted to extreme wave conditions that can be destructive. While wave transformation over low to mild sloping beaches have been widely studied, shoaling, breaking, reflection and dissipation over steep and very rough slopes are much less documented, Van der Meer (1992) and Dodet et al. (2018). With slightly different values some coral reef present similar slopes and roughness and have been the object of several insitu and numerical studies Buckley(2015), Sous (2020). During fall 2018 a measurement campaign was conducted close to the Artha breakwater. Offshore spectral parameters were measured at a directional wave buoy in 20 m water depth. A directional currentmeter was installed at the foot of the block armor unit at 15m deep while five pressure sensors were attached directly on the concrete blocks to obtain a complete cross-shore survey of wave transformation over the armor. In addition, high frequency impact pressure measurements are carried out on the dike wall together with punctual video recordings of wave impacts. The whole setup therefore provides a unique comprehensive in-situ dataset of wave transformation over a coastal breakwater.

Analysis of scratch visibility on polymeric surfaces using 3D roughness measurement and the bidirectional reflectance distribution function (BRDF)

The evolution of visual aspect of polymers with wear is a fundamental problem in numerous industries. In this article, we study the visibility of scratches. Fifty parallel micro-scratches are performed on three samples differing only by their values of gloss. Scratches are much more visible on glossy samples than on mat ones, in agreement with previous works. To interpret these results, a bidirectional reflectance distribution function (BRDF) model is developed to compute the way a surface scatters light based on a roughness measurement described by a distribution of microfacet orientations. In this paper, this BRDF model is applied to investigate the influence of the scratches on the light scattering properties of a surface. Roughness measurements are performed on the surfaces before and after scratching. Then, the BRDFs are computed and compared to each other. The visibility of scratches strongly depends on how much they modify the roughness slope distribution function of the surface. Depending on the initial gloss of the surface, this leads to more or less contrast. Finally, a visibility criterion is proposed based on this contrast effect.

Water-dispersible colloids distribution along an alluvial fan transect in hyper-arid Atacama Desert

As located in one of the oldest and driest deserts on Earth, soils in the Atacama Desert are greatly affected by atmospheric dust deposited on soil surface and the related fate of water-dispersible colloids (WDCs, <300 nm). We hypothesize that formation and content of these WDCs change with topography and age of natural soils. To highlight the processes involved, we investigated a mid-sized and gently (∼5°) sloping alluvial fan system of multi-phase evolution at 1480 m a.s.l. in the Paposo region of the hyper-arid Atacama Desert, which is considered typical for this part of the Coastal Cordillera. Sampling was done along a topographic transect in 11 pits, and assessed the distribution and composition of WDCs by means of asymmetric flow field-flow fractionation (AF4). The younger fan section (optically stimulated luminescence (OSL)-age of ∼13.6 ka) exhibited a pronounced surface roughness and steep slopes. Here, WDCs from the top soils (0–1 cm) free of plants contained nearly 54 ± 7% of medium-sized colloids (MCs, 210–300 nm) with a dominance of Si and Al. The elevated concentrations of fine colloids (FC, 24–210 nm) and particularly nanocolloids (NCs, 0.6–24 nm) was shown in levelled surface soils near shrubs with predominance of organic carbon (OC) and Ca. With higher collodial OC and Ca content in soils near shrubs, more WDC-P was formed concomitantly through increased OC-Ca-P associations. Larger variations in total WDC content were detected in the surface soils of the older fan section, which was dated to ∼56.4 ka. Here, the peaking NC had almost disappeared and thus MC dominated, probably reflecting re-aggregation and wind erosion over longer periods of time across a relatively smooth land surface. The WDCs and WDC-P peaked at 5–10 cm depth in the older fan section, as here a solid mineral/salt layer was present, while in the younger fan section the WDCs were more likely to be translocated from ‘permeable’ surface into deeper layers, likely reflecting leaching with occasional heavy rainfall. Overall, forms and distribution of WDCs depended on both topographic position and sediment age, thus making colloids as unique tracers of soil development processes during myriad or more years.

Transverse energy loss slope in meandering channels

Limited research has been conducted on transverse energy loss in meandering channels. Previous studies made assumptions regarding a linear vertical profile of transverse velocity and rectangular cross sections with horizontal transverse beds, neglecting the effects of nonlinear transverse velocity profiles and transverse bed slopes that contribute to topographic steering. In this study, a novel expression for the transverse energy loss slope is derived analytically. This expression incorporates a nonlinear vertical distribution for transverse velocity and considers non-rectangular cross sections, thereby improving the computation of roughness coefficients in curved channels. A topographic steering number is introduced, which indicates the presence of topographic steering when it exceeds unity. The developed equation rectifies the previous underestimation of sinuosity in natural rivers when compared to existing equations. Additionally, an expression for superelevation is derived, accounting for channel roughness and transverse bed slope, unlike previous equations. The study reveals that roughness can significantly affect the height difference between outer and inner banks. Under higher roughness conditions, the height difference can exceed predictions from existing formulas by up to 50%. This emphasizes the importance of considering roughness effects in accurately estimating superelevation. The developed equations are validated through comparisons with available field, laboratory, and numerical data.

Quantifying flow and velocity distributions in open channels with varied roughness and slopes: a modelling approach

ABSTRACT Understanding flow and velocity distributions in open channels is important for designing various hydraulic structures. This study focuses on modeling the flow and velocity distributions along with different open channel roughness (steel and concrete) and slopes from 0.0–4.7%, using an ultrasonic flowmeter and 3D scanner. Comprehensive Kriging and Linear Regression Models were developed to simulate flow behavior, considering the effects of surface roughness and channel slope. The models utilized appropriate boundary conditions by varying the roughness values. The concrete channel had an average centreline flow and velocity of 0.21 m3/s and 0.64 m/s, respectively, while the average flow and velocity for the steel channel was 0.33 m3/s and 0.97 m/s, respectively. The model’s accuracy and reliability were assessed by Pearson correlation and standard error of the estimate (SEE). According to the Pearson correlation, there is a significant relationship between the slope and flow on steel and concrete, with an average r equal to 0.75. The standard error of the estimates between observed and measured velocity and flow were 0.164 and 0.001, respectively.

Canal Controllability Identification Based on Automation Theory to Improve Water Delivery Efficiency in Irrigation Canal Systems

Canal controllability is an open and significant topic that addresses the unreliability/uncertainty in water delivery, efficiency, and modernization in the irrigation system. The study developed an analysis tool for canal controllability to estimate controllable performance and reduce the uncertainty of water delivery under steady and unsteady flow. We designed a linear quadratic control algorithm and applied it to the Nongchang test canal to verify the tool reliability and improve efficiency of water utilization. Finally, the effects of hydraulic variables on canal controllability were quantified. The numerical model of unsteady flow showed satisfactory predictions of water level (correlation coefficient, root mean square error, and mean absolute percentage error were 0.929%, 0.293%, and 12.86%, respectively). The Nongchang test canal was rather controllable (controllability indicator 0.265 to 0.279), implying that linear quadratic control algorithm was appropriate. The algorithm performed well under all conditions tested; the maximum absolute error was 3.66%–8.65%. The water level remained stable (deviation usually less than 0.05 m) and water delivery met user demands in terms of flow rate (the measure of performance relative to adequacy was 92.51%–98.94%) with relatively small gate movements. The bottom slope and roughness were the principal contributors to controllable performance, explaining approximately 46% of the variance. Specifically, controllability was highest when the bottom slope was low, and the roughness and side slope were high. We offer a reliable and flexible tool for assessment of canal controllability. Study results demonstrated that stakeholders benefit when conventional canal operation is modernized. The work will guide automation and upgrading of canal hardware as irrigation becomes optimized.

Influence of roughness and cross slope induced dynamic loads on flexible pavement responses

ABSTRACT Among all the factors influencing flexible pavement design, vehicular loads are of prime importance. Thus the present study evaluates the dynamic wheel loads on the pavement by considering the prime factors related to the vehicle and the pavement. Relationships are developed for three different trucks considering the combined effects of vehicle speed, gross vehicle weight, and pavement roughness on dynamic loads. The study further quantified the effect of pavement cross slope on vehicular loading in the outer wheel path. Furthermore, the critical responses for a flexible pavement section are determined using finite element analysis by considering the viscoelastic properties of asphalt layers and moving loads. The findings of this study reveal that, even for a smooth pavement with roughness ranging between 1 and 2 m/km, the dynamic load can be 7–13% higher than the static weight. The dynamic loads further increase rapidly as the pavement deteriorates. Compared to the conventional static analysis, incorporating dynamic loads into pavement analysis revealed an increase in the critical responses by 6–50%. Further, due to the interplay between vehicle speed, dynamic load coefficient, effective load, dynamic modulus, and loading frequency, a non-linear decrease in critical responses is observed with increased vehicle speed.

Combined effects of moss colonization and rock fragment coverage on sediment losses, flow hydraulics and surface microtopography of carbonate-derived laterite from karst mountainous lands

Moss and rock coverage play important roles in the soil erosion processes of karst mountainous lands. We conducted simulated rainfall experiments to investigate the combined effects of moss colonization and rock fragment coverage (RC) on the sediment losses, flow hydraulics and surface microtopography of karst carbonate-derived laterite. Soil slopes with moss colonization and different rock fragment coverages (0, 30 % and 60 %) were subjected to simulated rainfall with intensities of 100 mm h−1 in 50 cm × 30 cm × 15 cm flumes. Two sequential soil erosion events, E1 and E2, were induced with two rainstorm events; E2 was induced 24 h after E1. The results showed that the mean runoff rates (MR) of moss-covered slopes with 0 and 30 % RC were significantly lower than those of bare slopes (by 27.78 % and 24.06 %, respectively), and this effect gradually decreased as RC increased. Moss coverage also significantly decreased the mean flow velocity, and RC without moss coverage increased the flow velocities during rainfall. Moss-covered slopes showed significant decreases in mean sediment loss (MSL) (by 64.87 %, 78.89 % and 87.03 % for the 0, 30 % and 60 % RC in the E1 + E2 conditions, respectively) relative to bare slopes, and RC increases also decreased MSL. In addition, moss colonization significantly increased the initial slope roughness in both the horizontal (cl) and vertical (RR) directions. With moss coverage, slope roughness was less affected by slope erosion events due to protective effects. These results provide reference data for researching the mechanisms of moss and rock coverage for controlling and preventing karst slope erosion.