Relative Velocity Research Articles

Dynamic object detection using sparse LiDAR data for autonomous machine driving and road safety applications

Light Detection And Ranging (LiDAR) sensor offers solutions to extract real-time information of vehicle’s surroundings and can provide a new opportunity to improve the road safety related issues in mixed traffic conditions. This paper explores fundamental principles and combination of algorithms, to accurately detect, classify and track surrounding vehicles on expressways using a vehicle mounted cost-effective LiDAR sensor in dynamic conditions. The proposed approach employs algorithms such as Density-Based Spatial Clustering of Applications with Noise, Random sample consensus, and Kalman filter on 3D LiDAR data for ground and non-ground points segmentation, object clustering, road boundary identification, vehicle classification and tracking. Trajectory data of the tracked vehicles is used to estimate their relative positions and speeds. The surrounding vehicles were classified into three categories: two-wheelers, four-wheelers and heavy-vehicles. The proposed method achieves an accuracy, precision, recall, and F1-score above 94 %, demonstrating its robustness. The resilience and versatility of the proposed algorithm were validated through comprehensive evaluations on a significant dataset spanning over 8000 km (around 3.6 million frames) of driving data collected under varied environmental scenarios on expressway. Further, various applications of proposed methodology in road safety studies are discussed. The approach can extract real-time micro-level trajectory data for surrounding vehicles on expressways in any lighting condition, which is useful for researchers and can be used in connected and autonomous vehicles. It also provides valuable information for assessing surrogate safety measures and identifying road safety issues and suggesting countermeasures, including advanced and cost-effective driver assistance system applications.

Neutron emission from a source moving in a gravitational field

This work is devoted to the problem of neutron field formation near elliptical orbits of space objects equipped with nuclear power plants. The high-energy part of the fission spectrum is not affected by the gravitational field. Radiation safety is ensured by the triad fair for a point source: activity-distance-time. The connection between space object orbit parameters and neutron flux density occurs for the thermal (near-thermal) part of the spectrum. The possibility of formation of a stable neutron trace in the volume of a «torus» around the orbit of a space object is considered. The paper presents theoretical and numerical evidence of the validity of the hypothesis put forward. The introduction considers the separation effect of Galileo's relativity principle in the case of rectilinear uniform motion of a point isotropic neutron source on a plane. The occurrence of angular asymmetry of the neutron distribution in a stationary coordinate system when their relative velocity is close to the transport velocity of the source is illustrated. Under these conditions, a significant velocity dispersion of initially monochromatic neutrons is also recorded. This expected fundamental kinematic effect determines the characteristic distribution of neutrons in the gravitational field when the source moves along the Kepler orbit. The solution of the problem is carried out in the velocity space. It is argued that if the distribution of neutrons in the velocity space is such that their velocities are collinear to the orbital velocity of the source, this indicates the existence of a neutron flux near the orbit. The problem is analysed on the example of one revolution of a hypothetical space station by simulation modelling. For this purpose, thermal neutron packets with isotropic angular distribution were generated at eight points of an elliptical orbit. The neutron and source velocity fluxes at the selected points of the orbit were compared in a coordinate system related to the earth. The obtained data made it possible to calculate the densities of neutron velocity fluxes to the front and rear hemispheres relative to the source orbital motion as a function of the polar angle, while the value of the determinant of the correlation matrix – an indicator of collinearity of neutron velocity vectors in the flux - was fixed. The results of the studies confirm the hypothesis put forward about the possibility of formation of a «trace» in the orbit of a thermal neutron source, which determines the need to take it into account as a significant component of radiation risk.

Numerical Modelling of the Hydrodynamic Performance of Biodegradable Drifting Fish Aggregating Devices in Currents

Fish Aggregating Devices (FADs) are essential supplementary structures used in tropical tuna purse-seine fishing. They are strategically placed to attract tuna species and enhance fishing productivity. The hydrodynamic performance of FADs has a direct effect on their structural and environmental safety in the harsh marine environment. Conventional FADs are composed of materials that do not break down naturally, leading to the accumulation of waste in the ocean and potential negative effects on marine ecosystems. Therefore, this work aimed to examine the hydrodynamic performance of biodegradable drifting FADs (Bio-DFADs) in oceanic currents by numerical modelling. The Reynolds-averaged Navier–Stokes equation was used to solve the flow field and discretized based on the realizable k-ε turbulence model, employing the finite volume method. A set of Bio-DFADs was developed to assess the hydrodynamic performance under varying current velocities and attack angles, as well as different balsa wood diameters and sinker weights. The results indicated that the relative current velocity significantly affected the relative velocity of Bio-DFADs. The relative length of the raft significantly affected both the relative velocity and the relative wetted area in a pure stream. Finally, the diameter of the balsa wood affected the drift velocity, and the sinker’s relative weight affected the hydrodynamic performance of the Bio-DFADs.

A Flexible Topology Control Strategy for Mega-Constellations via Inter-Satellite Links Based on Dynamic Link Optimization

In large-scale satellite constellations, the efficiency of inter-satellite communication is paramount. Traditional topology control strategies, such as the Manhattan configuration, provide stable links but can result in indirect communication paths, affecting the efficiency of information transfer. This paper addresses this issue by proposing an innovative “3 + 1” dynamic topology control scheme. The scheme retains three static links determined by the relative angular velocity and acceleration while introducing a dynamic link based on distance and angular velocity constraints to optimize the link duration and overall network communication efficiency. To address the complexity of matching dynamic links, this paper introduces an elite strategy-based maximum weighted matching algorithm for general graphs. Compared to traditional greedy algorithms, our proposed algorithm significantly improves the link duration and topological stability. Through simulation experiments comparing communication delays between Xiamen and Los Angeles, our results show that the proposed dynamic link scheme substantially reduces the average delay, enhancing the efficiency and flexibility of inter-satellite communication. This research not only extends the duration of inter-satellite links but also provides new perspectives and methodologies for further studies on inter-satellite topology control strategies.

Study on Aerodynamic Performance and Wake Characteristics of a Floating Offshore Wind Turbine in Wind–Wave Coupling Field

Floating offshore wind turbines (FOWTs) exhibit complex motion with multiple degrees of freedom due to the interaction of wind and waves. The aerodynamic performance and wake characteristics of these turbines are highly intricate and challenging to accurately capture. In this study, dynamic fluid body interaction (DFBI) and overset grid technology are employed to investigate the dynamic motion of a 5 MW FOWT. We use the volume of fluid (VOF) method and improved delayed detached eddy simulation (IDDES) model to investigate the aerodynamic performance and wake evolution mechanism for various wave periods and heights. According to the findings, the magnitude of the pitch motion increases with the period and height of the waves, leading to a decrease in both the power output and thrust; the maximum power was reduced by nearly 6.8% compared to a wind turbine without motion. The value of power and thrust reduction varies for different wave periods and heights, and is influenced by the relative speed and pitch angle, which play a crucial role. Wind–wave coupling has a significant impact on the evolution of both wake and vortex structures for FOWT. The wake shape downstream is also dynamically influenced by the waves. In the presence of wind and wave coupling, the interaction between the wind turbine and the wake is heightened, leading to the merger of two unstable vortex rings into a single, larger vortex ring. The research unveils a comprehensive picture of the offshore wind energy dynamics and wake field, which holds immense significance for the design of floating wind turbines and the optimization of wind farm layout.

Filtering Function to Mitigate the Impact of Cyber Attacks in Cooperative Adaptive Cruise Control

Among automated driving technologies, adaptive cruise control (ACC), which controls the distance between vehicles and their relative speed, is becoming popular. Cooperative ACC (CACC) uses vehicle-to-vehicle communication and sensors to control the distance between vehicles. Recently, cyber attacks against automated driving systems have been a focus, in which information on pedestrians or preceding vehicles obtained from LiDAR and sensors is disguised. Such cyber attacks enable attackers to obtain accurate information on preceding vehicles and pedestrians. This can result in accidents. The purpose of this study is to develop a filtering function to reduce the impact of cyber attacks using available information. The contribution lies in proposing a filtering function for situations in which sensor offsets and communication delays arise owing to cyber attacks.

Automatic lane change based on dynamic occupancy of an adaptive gird zone

This paper presents adaptive and occupancy grid map algorithms for automatic lane change technology, a core technology in autonomous vehicles. The objectives are to improve driver safety and convenience with technology that automatically changes lanes at the request of the driver. The algorithms construct nine grids on the basis of ego vehicles and generate adaptive and occupancy grid maps by using the relative speeds of ego and target vehicles. When a driver requests a lane change, the adaptive grid map reduces the number of cases where the target vehicles may exist around the ego vehicle from 256 to 32, thus decreasing the calculation amount. Therefore, the algorithms are suitable for use in autonomous vehicles that require real-time calculations. An occupancy grid map is formed in accordance with the location of the target vehicles, and whether lane changes are possible is determined. The algorithms generate a virtual simulation environment with the CarMaker and are simulated using Matlab/Simulink. An experiment is conducted in a real driving environment with real vehicles to prove the validity of the algorithms.© 2017 Elsevier Inc. All rights reserved.

Identifying waves of COVID-19 mortality using skew normal curves

We propose a model for multiple waves of an epidemic that decomposes the health outcome of interest into the sum of scaled skew normal curves. When applied to daily COVID-19 mortality in six regions (Japan, Italy, Belgium, Ontario, Texas, and Peru), this model provides three notable results. First, when fit to data from early 2020 to May 31, 2022, the estimated skew normal curves substantially overlap with the dates of COVID-19 waves in Ontario and Belgium, as determined by their respective health authorities. Second, the asymmetry of the skew normal curves changes over time – they progress from increasing more quickly to decreasing more quickly, indicating changes in the relative speed that daily COVID-19 mortality rises and falls over time. Third, most regions have day-of-the-week effects, which suggests that day-of-the-week effects should be included when modeling daily COVID-19 mortality. We conclude by discussing limitations and possible extensions of this model and its results, including commenting on its applicability to potential future COVID-19 waves.

Geometrical Interpretation of Space Contraction in Two-dimensional Lorentz Transformation

This paper points out that the transformation equations for the spatial and temporal coordinates between two frames of reference in the existing generally accepted version of the Lorentz transformation are deficient, since transformation equations are based on one dimensional motion between inertial frames. Therefore, all possible space-time coordinate transformation equations between moving and stationary frames by prolonging Lorentz transformation in a two-dimensional plane are thoroughly proposed in this article. If denotes the relative velocity between stationary frame (x, y) and moving frame (x', y'), then the transformation equations along X and Y-axis under two-dimensional Lorentz are given, respectively, by the formulas (see full text) . In this work we conclude that length and breadth of a rectangle appears to be shortened to the observer when there is the relative velocity between the rectangle and observer along both X and Y-axis. In particular, we present a concise and carefully reasoned account of a new aspect of Lorentz transformation which decently allows for the determination of space-time coordinates transformation equations in two dimensions of space.

Compliant control of biomimetic parallel torso based on musculoskeletal control

Compliant movement and stress buffering of the torso are particularly important for state transition during high-speed locomotion in quadrupedal mammals. Currently, passive compliant control is commonly used in bionic torsos of quadruped robots, while active compliant control remains rare and immature. In previous research, we developed an active six-Degree-of-Freedom (DoF) bionic parallel torso. In this paper, we establish a muscle model that includes four biomechanical elements representing muscle characteristics (muscle force-fiber length and muscle velocity relationships) from the perspective of biology and physiology. We propose a musculoskeletal model that simulates the biological motion control system to control the compliant movement of each joint of the parallel mechanism. This model includes: 1) a neural equilibrium point controller that represents the transmission of motion commands, 2) activation dynamics that describe the activation of stimulated muscles, 3) contraction dynamics that emphasize the biomechanical characteristics of muscle tendons, 4) skeletal dynamics that describe bone movement. The effects of flexor and extensor stimulation on muscle activation, force, length, and velocity were analyzed. The results showed that both the flexor and extensor muscles will contract after corresponding stimulation. Furthermore, adjusting muscle stimulation through the musculoskeletal model can drive the parallel mechanism to reach the desired position. The musculoskeletal control method based on external force feedback can establish new torque balance in joints and drive the parallel torso to achieve compliant movements. Simulation and experiments have demonstrated the feasibility of the musculoskeletal control method. This method enhances the compliance and environmental adaptability of the parallel torso in practical applications.

Performance Evaluation and Degradation Analysis of Suspended Dense Broken Stone Road Foundation Stabilized by Cement under Conditions of Freezing and Thawing

A suspended dense graded broken stone road foundation stabilized by cement is a commonly employed material in roadworks, which is vulnerable to harm caused by freezing and thawing processes. This investigation intends to evaluate the laboratory behavior and the characteristics of freezing and thawing process-induced deterioration in a broken stone road foundation stabilized by cement with suspended dense grading, employing mechanical examinations and acoustical methods. The rate of mass loss in the broken stone road foundation stabilized by cement progressively rises, and the rate of decline in the compressive strength could potentially intensify as freezing and thawing processes augment. The modulus of resilience diminishes as freezing and thawing processes progress, and ultrasonic wave velocity also decreases. The patterns of mass loss, compressive strength decline, resilience modulus reduction, and ultrasonic wave velocity alteration adhere to a parabolic fitting relationship with freeze–thaw cycles, with an R2 above 0.95. The curves depicting the relationship of mass, compressive strength, resilience modulus, and ultrasonic wave velocity exhibit a steeper trend significantly after 10–15 cycles, which can be ascribed to the emergence of microcracks and the progression of flaws within the material. The evolution of damage in the broken stone road foundation stabilized by cement is monitored to progress through three distinct stages based on acoustic emission: initial, stationary, and failure. As freezing and thawing processes accumulate to 20 cycles, the length of initial phase correspondingly rises to three times, the length of failure stage diminishes to about one fifth.

Investigating the impact of a large river and its surrounding contextual conditions on pedestrians’ summer thermal perceptions in a Cfa-climate city

Thermal comfort studies are usually employed to find subjective thermal responses [indicated by neutral temperature (NT), i.e. the temperature with no thermal stress] of residents from a region towards thermal environments. According to the recently published works in the literature, NTs are affected by many factors, such as geographical location and microenvironments. To elucidate the origins of these effects, the impact of microenvironment elements around a water surface on pedestrians’ thermal perceptions was systematically investigated in this work. The Fujiang River (FJR) in Mianyang City was taken as the sample site. The municipal meteorology station is located next to the site by around 2.5 km. By performing meteorology measurements combining questionnaires, it was found that the riverside NT (indicated by physiologically equivalent temperature, PET) of Mianyang in the summer of 2023 was 21.4 °C. The relationship between the distance from the water (DFW) and NT was quadratic linear. The same phenomenon took place by using either PET or Universal Thermal Climate Index (UTCI) indexes. Meanwhile, the meteorological contexts also affected NTs, including relative humidity (RH) and air velocity (Va). Regarding RH, the NPET increased from 15.2 °C (RH = 50%) to 26.9 °C (RH = 90%). In contrast, the NPET dropped from 23.0 to − 50.6 °C when the Va increased from 0.2 to 2.5 m/s, respectively. From our analysis, it was demonstrated that human thermal responses are significantly affected by both the microenvironmental and meteorological backgrounds around the water surface. Our work provides valuable insights for the proper use of water surfaces in urban design for adjusting thermal comfort.

Plasma lensing interpretation of FRB 20201124A bursts at the end of September 2021

ABSTRACT When radio photons propagate through a non-uniform electron density volume, the plasma lensing effect can induce an extreme magnification to the observed flux at certain frequencies. Because the plasma lens acts as a diverging lens, it can extremely suppress the observed flux when aligned with the source. These two properties can theoretically cause a highly magnified fast radio burst (FRB) to become faint or even disappear for a period of time. In this paper, we interpret that the significant increase in burst counts followed by a sudden quenching in FRB 20201124A in September 2021 can be attributed to plasma lensing. Based on the one-dimensional Gaussian lens model, we search for double main-peak structures in the spectra just before its extinction on 2021 September 29. After the de-dispersion and de-scintillation procedures, we find eight bursts with double main-peaks at stable positions. There are three parameters in our modelling, the height N0, width a of the lens and its distance DLS to the source. We reformulate them as a combined parameter ${P}_0 \propto \left(\frac{a}{\mathrm{au}}\right)\sqrt{\frac{\mathrm{kpc}}{D_{\mathrm{LS}}} \frac{\mathrm{pc}\mathrm{cm}^{-3}}{N_0} }$. The frequency spectra can give an accurate estimation of P0 corresponding to $\left(\frac{a}{\mathrm{au}}\right)\sqrt{\frac{\mathrm{kpc}}{D_{\mathrm{LS}}} \frac{\mathrm{pc}\mathrm{cm}^{-3}}{N_0} } \approx 28.118$, while the time of arrival only give a relatively loose constraint on a2/DLS. Comparing with the observation dynamic spectra, we suggest that for a plasma lens in host galaxy, e.g. DLS ≈ 1 kpc, the width of lens can not be larger than 40 au. At last, we estimate the relative transverse motion velocity between the lens and source, $v\approx 98\left(\frac{a}{\mathrm{au}}\right)\mathrm{km\,s^{-1}}$.

Memory effect of gravitational wave pulses in PP-wave spacetimes

In this paper, we study the gravitational memory effect in pp-wave spacetimes due to the passage of a pulse having the form of a ramp profile through this spacetime. We have analyzed the effect of this pulse on the evolution of nearby geodesics, and have determined analytical solutions of the geodesic equations in the Brinkmann coordinates. We have also examined the changes in the separation between a pair of geodesics and their velocity profiles. The separation (along x or y-direction) increases monotonically from an initial constant value. In contrast, the relative velocity grows from zero and settles to a final non-zero constant value. These resulting changes are retained as memory after the pulse dies out. The nature of this memory is similar to that determined by earlier workers using Gaussian, square, and other pulse profiles, thereby validating the universality of gravitational wave memory.

Gas assisted binary black hole formation in AGN discs

ABSTRACT We investigate close encounters by stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs) as a potential formation channel of binary black holes (BBHs). We perform a series of 2D isothermal viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code Athena++. We co-evolve the embedded BHs with the gas keeping track of the energetic dissipation and torquing of the BBH by gas gravitation and inertial forces. To probe the dependence of capture on the initial conditions, we discuss a suite of 345 simulations spanning BBH impact parameter (b) and local AGN disc density (ρ0). We identify a clear region in b − ρ0 space where gas assisted BBH capture is efficient. We find that the presence of gas leads to strong energetic dissipation during close encounters between unbound BHs, forming stably bound eccentric BBHs. We find that the gas dissipation during close encounters increases for systems with increased disc density and deeper periapsis passages rp, fitting a power law such that $\Delta E \propto \rho _0^{\alpha }r_{\mathrm{p}}^{\beta }$, where {α, β} = {1.01 ± 0.04, −0.43 ± 0.03}. Alternatively, the gas dissipation is approximately ΔE = 4.3MdvHvp, where Md is the mass of a single BH minidisc just prior to the encounter when the binary separation is 2rH (two binary Hill radii), vH and vp are the relative BH velocities at 2rH and at the first closest approach, respectively. We derive a prescription for capture which can be used in semi-analytical models of AGN. We do not find the dissipative dynamics observed in these systems to be in agreement with the simple gas dynamical friction models often used in the literature.

Near‐Storm Environmental Relationships With Tropical Oceanic Convective Structure Observed During NASA CPEX and CPEX‐AW

AbstractDeep tropical oceanic convection (TOC) is a prevailing component of the tropical atmosphere and plays a significant role in modulating global weather and climate. Despite its importance, prediction challenges remain, partly attributed to a lack of understanding of how TOC relates to its near‐storm environments. Prior studies suggest location‐dependent relationships between TOC structure and associated environments, necessitating targeted regional studies. The NASA 2017 Convective Processes Experiment (CPEX) and 2021 CPEX—Aerosols & Winds (CPEX‐AW) field campaigns collected high‐resolution measurements of convective storms and their environments in the Gulf of Mexico, Caribbean, and western Atlantic basins, providing a rare opportunity to investigate near‐storm environmental relationships with 3‐D TOC structure where in situ non‐tropical cyclone‐related deep TOC research is comparatively lacking. Collocated CPEX and CPEX‐AW airborne observations from the multi‐wavelength Airborne Precipitation Radar, Doppler Aerosol Wind Lidar, and dropsondes revealed large near‐storm environmental variability across TOC of similar convective type (i.e., isolated, organized) and within individual convective systems. However, trends still emerged amongst the large environmental variability. Horizontal TOC structure was most consistently linked to planetary boundary layer and mid‐tropospheric near‐storm environments, with organized TOC being associated with generally greater relative humidity (RH) and vertical speed shear than isolated TOC. TOC intensity was linked to upper tropospheric (i.e., above melting level) near‐storm environments, with isolated TOC intensity most consistently associated with upper tropospheric CAPE and organized TOC intensity associated with upper tropospheric RH. Mesoscale low‐level convergence was also linked to greater organized TOC intensity, motivating further research using these unique data sets.

Scour at the rear side of rubble mound revetments due to random wave overtopping: Laboratory experiments

This study presents the physical model experiments on the wave overtopping induced bed level changes at an unprotected rear side of a rubble mound revetment with a crown wall. In the experiments, the wave conditions, the backfill material size, and the backfill depth (vertical distance from the crest level to the rear side bed level) are varied. Two mobility parameters, namely the densimetric overtopping discharge and the relative fall velocity, are introduced to represent the initiation of motion and suspension of the backfill material, respectively. The temporal evolution of scour depth at the rear side is related to the mobility parameter, the number of waves and the backfill depth utilizing regression analyses. The effect of the backfill depth on the scour is found very limited for the available data set. However, the time scale of the scour is found to be related with the backfill depth only. For the present data set, it varied within a range of 1500–16000 number of waves approximately, with an average of 5600 waves. An equilibrium scour profile is reached 3 to 4 times the time scale. The geometry of the scour profile is expressed in terms of the scour depth, based on the equilibrium scour profile data.

One-dimensional analysis of pressure variations induced by trains passing each other in a tunnel

In this study, the asymptotic solutions of the pressure variations induced by two trains passing each other in a tunnel are theoretically investigated. The one-dimensional inviscid compressible airflow is analysed, and two methods to obtain numerically exact solutions and $M_{H}$ expansion formulas for approximate equations are presented, where $M_{H}$ is the Mach number of the high-speed train. The pressure coefficient, corresponding to the maximum value of the magnitude of the pressure, is expressed as $|c_{p}|_{max}=|c_{p,min}|=[({R}/({1-R}))$ $(1+\alpha )^{2}+({R(1-R)}/{(1-2R)^{2}})(1-\alpha )^{2}]+O[M_{H}]$ , where $c_{p,min}<0$ , $\alpha =U_{L}/U_{H}$ and $U_{L}$ and $U_{H}$ denote the speeds of the low- and high-speed trains, respectively, and $R$ is the cross-sectional area ratio of the train to the tunnel. The theoretical results indicate the dependence of the speeds of the two trains on the pressure distribution and that the maximum magnitude of the asymptotic pressure for a fixed value of $M_{H}$ is obtained for $\alpha =1$ and $\alpha =0$ when $R< R_{c}$ and $R>R_{c}$ , respectively, where $R_{c}$ denotes the critical blockage ratio. Because the airflow along the side of the low-speed train, induced by the low-speed train, is along the running direction of the high-speed train and reduces the relative velocity of the high-speed train as the two trains pass each other, $|c_{p}|_{max}$ for $\alpha =0$ is larger than $|c_{p}|_{max}$ for $\alpha =1$ when $R>R_{c}$ . It is theoretically demonstrated that, as conventional high-speed railway systems satisfy $R< R_{c}$ , a conservative pressure estimation can be established assuming $\alpha =1$ .

Quantitative evaluation of bolt pre-load using coda wave interferometry and nonlinear coda wave interferometry: a comparative study

AbstractThe quantitative evaluation of bolt pre-load is crucial for the maintenance and prevention of accidents in bolt-connected structures. This study introduces the coda wave interferometry (CWI) method and the nonlinear coda wave interferometry (NCWI) method for quantitative evaluation of bolt pre-load. Experimental tests across three different scales of bolt pre-load changes were conducted on a bolt to compare the performances of CWI and NCWI in the quantitative evaluation of bolt pre-load. The results demonstrate that both CWI and NCWI can effectively characterize changes in bolt pre-load. For CWI, the relative velocity change (∆v/v) exhibits a linear relationship with the bolt pre-load. Meanwhile, for NCWI, the effective nonlinear level, denoted as $${\alpha }_{\Delta v/v}$$ α Δ v / v , demonstrates a quadratic dependence on the bolt pre-load. In CWI, the calculation of ∆v/v is dependent on the correlation coefficient between the coda waves of signals before and after bolt pre-load changes. It is prone to failure when there are significant changes in bolt pre-load. Conversely, NCWI demonstrates enhanced robustness in evaluating bolt pre-load changes across a range of magnitudes.

Implementation of a first-mill cane-feeding control strategy based on a cane-harvest system

The analysis of the extraction performance of three Colombian sugarcane factories revealed large variations in milling operations. Because more than 70% of the extraction occurs in the first mill, the chute level behavior was evaluated, and the coefficient of variation (CV) values were greater than 55%. This was mainly caused by the control strategy not being capable of mitigating the effect of processing different densities of sugarcane. This variability resulted from the frequent change between manual and mechanically harvested sugarcane. An in-line indicator was designed to determine the type of sugarcane; this was based on the electric current drawn by the cane leveller. In collaboration with factory A, a control strategy was designed that changes the velocity relationship of the conveyor belts depending on the sugarcane harvest type. The control strategy was also applied in the second factory (B), with only a 1.5 m high first-mill chute, which affects feeding stability, but dynamic current protection was added. This was based on PID controllers that manipulate conveyor velocity proportionally, reducing the chance that it would come to a halt, protecting the cane knives and shredder from electrical overload, and providing a more constant mill feed. The evaluation of the new control strategy was compared with the old control loops, increasing the overall extraction of 0.40 and 0.68% for factories A and B, respectively. Better stability was achieved in the first mill chute with a CV of approximately 30%, which was also reflected in the chute levels of the following mills. The new control strategy used the instruments and actuators already installed without any additional investments and can greatly improve the milling performance and, as a result, profitability.