Depth Control Research Articles

Specific features of applying machine welding with drop transfer in repair of operating pipelines

Introduction. Repair of pipelines under pressure of pumped media by means of welding is relevant to reduce the complexity of work. However, it may reduce the safety of work. To solve this issue, the authors consider applying the technological processes of machine welding with controlled drop transfer.Aim. To determine the main parameters of technological processes of machine welding with controlled drop transfer, affecting the safety of welding.Materials and methods. The authors developed a theoretical model for calculating the working thickness of a pipeline wall under pressure which they used for calculating the strength during welding. The dependence of the pipeline wall thickness at the edge of the penetrated hole on the internal pressure was also used in the calculations.Results. It was found that machine welding with controlled transfer of metal drops allows the wall penetration depth to be regulated by changing the welding variables. This significantly increases the safety of welding on pipelines under pressure of pumped media, compared to other types of welding. The developed welding processes ensure the safety of welding operations by means of a smooth and accurate control of the wall penetration depth. This is achieved by the correct selection of the background and peak current, control of the drop transfer process by arc voltage, control of the amount of weld metal and the heating temperature of welded structures.Conclusion. Recently, a number of repair technologies have been developed to improve the quality of welds in the construction and repair of trunk pipelines. The highly significant results of research on the development of machine welding technology with controlled drop transfer allow this technology to be recommended as an effective way to improve the safety of welding operations on pipelines under pressure of pumped media.

A Practical Guide to Hair Graft Placement Using the Sharp Implanter Method.

Hair transplantation using the sharp implanter method is increasing in popularity. However, there has been little discussion pertaining to surgical know-how or specific techniques that increase efficiency and precision. We describe surgical techniques that enable dense packing in a swift and efficient fashion with the sharp implanter method using photos and videos. Grafts were placed using the sharp implanter method while adhering to several important principles. Eleven principles regarding the following aspects of hair transplant surgery were explained: gripping the implanter, graft placing technique that minimizes graft popping and tissue trauma when using the implanter, efficient team surgery system with assistant staff, direction and sequence of graft insertion, effective regimen for using epinephrine to control bleeding, selection of appropriately sized implanter tip, selection and usage of wide and narrow channel implanter tips, importance and methods of depth control, and staff training. High graft survival and dense and natural hair density can be obtained with the sharp implanter method when performed in compliance with the principles described here. Appropriate use of the sharp implanter technique allows efficient and rapid graft insertion and achieves natural outcomes.

Barrier-Based Adaptive Line-of-Sight 3-D Path-Following System for a Multijoint Robotic Fish With Sideslip Compensation.

This article proposes a novel barrier-based adaptive line-of-sight (ALOS) three-dimensional (3-D) path-following system for an underactuated multijoint robotic fish. The framework of the developed path-following system is established based on a detailed dynamic model, including a barrier-based ALOS guidance strategy, three integrated inner-loop controllers, and a nonlinear disturbance observer (NDOB)-based sideslip angle compensation, which is employed to preserve a reliable tracking under a frequently varying sideslip angle of the robotic fish. First, a barrier-based convergence strategy is proposed to deal with probable along-track error disruption and suppress the error within a manageable range. Meanwhile, an improved adaptive guidance scheme is adopted with an appropriate look-ahead distance. Afterward, a novel NDOB-based sideslip angle compensation is put forward to identify the varying sideslip angle independent of speed estimation. Subsequently, inner-loop controllers are intended for regulation about the controlled references, including a super-twisting sliding-mode control (STSMC)-based speed controller, a global fast terminal sliding-mode control (GFTSMC)-based heading controller, and a GFTSMC-based depth controller. Finally, simulations and experiments with quantitative comparison in 3-D linear and helical path following are presented to verify the effectiveness and robustness of the proposed system. This path-following system provides a solid foundation for future marine autonomous cruising of the underwater multijoint robot.

A novel convex acoustic lens-attached ultrasound drug delivery system and its testing in a murine melanoma subcutaneous model

Target-specific drug release is indispensable to improve chemotherapeutic efficacy as it enhances drug uptake and penetration into tumors. Sono-responsive drug-loaded nano-/micro-particles are a promising solution for achieving target specificity by exposing them to ultrasound near tumors. However, the complicated synthetic processes and limited ultrasound (US) exposure conditions, such as limited control of ultrasound focal depth and acoustic power, prevent the practical application of this approach in clinical practice. Here, we propose a convex acoustic lens-attached US (CALUS) as a simple, economic, and efficient alternative of focused US for drug delivery system (DDS) application. The CALUS was characterized both numerically and experimentally using a hydrophone. In vitro, microbubbles (MBs) inside microfluidic channels were destroyed using the CALUS with various acoustic parameters (acoustic pressure [P], pulse repetition frequency [PRF], and duty cycle) and flow velocity. In vivo, tumor inhibition was evaluated using melanoma-bearing mice by characterizing tumor growth rate, animal weight, and intratumoral drug concentration with/without CALUS DDS. US beams were measured to be efficiently converged by CALUS, which was consistent with our simulation results. The acoustic parameters were optimized through the CALUS-induced MB destruction test (P = 2.34 MPa, PRF = 100 kHz, and duty cycle = 9%); this optimal parameter combination successfully induced MB destruction inside the microfluidic channel with an average flow velocity of up to 9.6 cm/s. The CALUS also enhanced the therapeutic effects of an antitumor drug (doxorubicin) in vivo in a murine melanoma model. The combination of the doxorubicin and the CALUS inhibited tumor growth by ∼ 55% more than doxorubicin alone, clearly indicating synergistic antitumor efficacy. Our tumor growth inhibition performance was better than other methods based on drug carriers, even without a time-consuming and complicated chemical synthesis process. This result suggests that our novel, simple, economic, and efficient target-specific DDS may offer a transition from preclinical research to clinical trials and a potential treatment approach for patient-centered healthcare.

Real-time melt pool depth estimation and control during metal-directed energy deposition for porosity reduction

Real-time melt pool depth estimation and control during metal-directed energy deposition for porosity reduction

Estimation and Control of a Towed Underwater Vehicle with Active Stationary and Low-Speed Maneuvering Capabilities

A variety of mission equipment is mounted and utilized on UUVs (unmanned underwater vehicles) for the development of marine resources and underwater searching for military purposes. For exploration of a wide area, it is advantageous to use a towed underwater platform, and for precision exploration to a specific location, to use an active mobile ROV (remotely operated vehicles). Since the TUV (towed underwater vehicle) moves according to the speed of the towing vessel, it cannot be operated if the vessel is stationary or the speed is low. Therefore, TUVs do not have equipment that is useful at low speeds, such as optical cameras or forward looking sonars. If a TUV capable of active movement such as stationary or low-speed operation is developed, it can search a wide area and then accurately search for a specific location, with one platform mounting various mission equipment. In this paper, we propose a method for estimating the control model for a prototype of this novel TUV, and propose a depth and posture control algorithm to which the model is applied. The proposed TUV and control algorithm were verified by experiments under the flow rate environment in the circulating water channel.

Dynamic Optimization of Variable Load Process for Combined Heat and Power Unit Based on Sequential Quadratic Programming and Interior Point Method Alternating Solution Method

Aiming at the problem that the modeling and solving method of combined heat and power (CHP) unit variable load control process is challenging to meet the demand for efficient analysis of complex systems, this paper proposes a method based on sequential quadratic programming and interior point method (SQP-IPM) alternating solution for dynamic optimization of the CHP unit variable load process. Firstly, by constructing the CHP unit mechanism model, multi-variable coordination control constraints, and output variable process constraints, the dynamic optimization proposition of the CHP unit variable load control process is formed. Then, the large-scale nonlinear programming (NLP) problem formed by using the orthogonal configuration method to discrete the state and control variables is optimally solved using the IPM-SQP alternating solution method. Further, from the perspective of balancing the accuracy of the solution and computational efficiency, the flexible convergence depth control (CDC) strategy is introduced into the alternative solution method to improve the real-time performance of the algorithm. Finally, the variable load control process of 300MW extraction CHP unit is simulated to verify that the proposed method reduces the calculation time for 12 consecutive variable load scenarios by about 70%, effectively improving the real-time performance of scenario applications.

Current Situation and Future Development Direction of Soil Covering and Compacting Technology under Precision Seeding Conditions in China

Precision seeding is an effective technical way to improve quality and reduce material costs. However, certain factors limit the development and promotion of precision seeding technology, among which the main factor is that the agronomic requirements of sowing vary significantly in different areas, and there is a lack of suitable implements; at the same time, each link among the parts interact, which brings specific difficulties to improving the operational effect. This paper summarizes the precision seeding technology from the perspective of precision seeding realization and the consistency of seed spacing and use of consistent sowing depth control technology. A detailed description is included of the precision seed-discharge technology, the smooth seed-dropping technology, and the seed falling into the seed bed with precision. The need for regulation technology for consistent sowing depth is explained from a developmental perspective. The research status of compatible sowing depth control technology is described, as used in soil covering and compacting. This paper presents the problems and future development directions of soil-covering and compacting technology under precision-seeding conditions, including developing adaptable regional soil-covering and compacting devices, improving the processing and equipment technology of enterprises, strengthening the structural optimization design of soil-covering and compacting devices, conducting research into soil-covering and compacting control methods, and promoting the intellectual development of agricultural equipment.

On the ability of OMIP models to simulate the ocean mixed layer depth and its seasonal cycle in the Arctic Ocean

We evaluate the skills of ocean–sea ice general circulation models involved in the Ocean Modeling Intercomparison Project in simulating the ocean mixed layer depth and its seasonal cycle in the Arctic region. During summer months, all models consistently underestimate the mixed layer depth compared to observational data from the Monthly Isopycnal Mixed layer Ocean Climatology and the Ice Tethered Profilers. In fall and winter, the models exhibit great variability compared to observational data, and inter-model comparison reveals differences up to several tens of meters. We analyze the origin of the fall and winter model biases in ice-covered regions, where the seasonal cycle of the surface salinity and mixed layer depth is strongly influenced by brine rejection resulting from ocean–sea ice interactions.Focusing first on the central Arctic Ocean, defined here as the region north of 80° N, we show that all models simulate more or less the same vertical sea ice mass balance and thus similar salt fluxes into the ocean during sea ice freezing. Furthermore, the model ensemble features a strong relationship between the stratification profile in September and the mixed layer depth at the end of winter. The models whose stratification compares the best to observational data also display the most realistic values of the mixed layer depth at the end of winter. We argue that the discrepancies between models are therefore not so much linked to the surface salt balance but rather to the accuracy with which those models reproduce the vertical salinity profile. In short, a weakly stratified ocean tends to create a deep mixed layer, while strong stratification leads to a shallow mixed layer. To substantiate this conclusion, we apply a simple conceptual model, which simulates the month-to-month evolution of the mixed layer depth using as input the vertical salinity gradients and the surface salt fluxes from general circulation models. Quite surprisingly, this simplified dynamics captures very well the behavior of the general circulation models, emphasizing the role of the different vertical stratification in the control of the mixed layer depth. Furthermore, this interplay may also significantly account for the large mixed layer biases observed in other ice-covered regions of the pan-Arctic seas, even though sea–ice ocean interaction is not the only driver of mixed layer variability in fall and winter there.

Neural network-based depth and horizontal control for autonomous underwater vehicles with prescribed performance

This paper presents a study of horizontal and depth controller design for autonomous underwater vehicles (AUVs) regarding model uncertainties, input constraints, and ocean currents. Firstly, the depth-plane and horizontal-plane models of AUV are established comprehensively with ocean currents. Besides, the AUV's characteristics and physical limitations are also described. Secondly, extended perturbation observers (EPOs) are innovatively constructed to estimate ocean currents, which guarantee the accuracy in the case of time-varying ocean currents. To achieve the position errors with prescribed performance guarantees, a finite-time prescribed performance function is proposed such that the convergence time, maximum overshoot, and steady error bounds can be preset directly. Neural network-based adaptive control is adopted to deal with model uncertainties and environmental disturbances. Auxiliary systems with a smooth switching function are introduced to alleviate the effect of input saturation. Furthermore, rigorous theoretical analyses are also carried out to demonstrate the robust stability of the proposed controllers. Finally, extensive numerical simulation studies confirm the strong and conclusive evidence for the proposed method's effectiveness, robustness, anti-jamming ability, and feasibility.

Patterned Laser Ablation of Microgrooves with Controllable Cross‐Sections

AbstractFabricating precision microgrooves with controllable cross‐sections on difficult‐to‐machine materials is significantly valuable but still challenging. Herein, a patterned laser‐induced microjet‐assisted ablation method for cross‐sectional profiles controllable laser micromachining is proposed. During the liquid‐assisted laser ablation process, debris and bubbles that may disturb the laser energy deposition can be instantaneously expelled by a directional laser‐induced microjet. The Gaussian laser spot is spatially modulated into specific geometric shapes, such as triangles, to tune locally deposited laser energy to carve microgrooves with designed cross‐sections. To achieve customized microgrooves efficiently, a reliable geometrical model based on the ablation threshold theory is developed to guide the processing parameter selection, including the laser spot shape, polarization, pulse energy, and scanning strategies. The simulation and experimental results confirm that this method achieves the decoupled control of the groove depth and width in a single‐path laser ablation process. Using this method, the design and manufacturing of microgrooves with controllable cross‐sections on single crystalline silicon carbide are demonstrated. The patterned laser‐induced microjet‐assisted ablation method provides a new route for fabricating precision microgrooves with controllable cross‐sections on difficult‐to‐machine materials.

Lightweight aerial image object detection algorithm based on improved YOLOv5s

YOLOv5 is one of the most popular object detection algorithms, which is divided into multiple series according to the control of network depth and width. To realize the deployment of mobile devices or embedded devices, the paper proposes a lightweight aerial image object detection algorithm (LAI-YOLOv5s) based on the improvement of YOLOv5s with a relatively small amount of calculation and parameter and relatively fast reasoning speed. Firstly, to better detect small objects, the paper replaces the minimum detection head with the maximum detection head and proposes a new feature fusion method, DFM-CPFN(Deep Feature Map Cross Path Fusion Network), to enrich the semantic information of deep features. Secondly, the paper designs a new module based on VoVNet to improve the feature extraction ability of the backbone network. Finally, based on the idea of ShuffleNetV2, the paper makes the network more lightweight without affecting detection accuracy. Based on the VisDrone2019 dataset, the detection accuracy of LAI-YOLOv5s on the mAP@0.5 index is 8.3% higher than that of the original algorithm. Compared with other series of YOLOv5 and YOLOv3 algorithms, LAI-YOLOv5s has the advantages of low computational cost and high detection accuracy.

Single-neuron adaptive pitch-depth control for a lift principle AUV with experimental verification

This paper addresses the problem of pitch and depth control for a novel deep-sea, high-speed, and heavy-load autonomous underwater vehicle based on the lift principle (LP-AUV). One of the characteristics of an LP-AUV is the use of downward lift to overcome varying residual buoyancy and achieve rapid diving. The pitch angle determines the action direction of the lift force, thus affecting the safety and stability of diving and navigation. Specifically, the main requirement for the controller is accuracy and no overshoot in either the depth or pitch outputs of the system. To offer accurate and reliable control ability, with various speeds and residual buoyancies, unmatched disturbances and the action of lift taken into consideration, a single-neuron controller with self-learning and self-adaptive capabilities is proposed. Based on the Hebb learning rule, a supervised learning rule that can learn not only from the principles of neural networks but also from tuning experience is designed. Hence, the weights of the single-neuron controller can be constantly adjusted online to improve the control performance of the system more rapidly. Simulation results show the robustness and effectiveness of the proposed controller toward external disturbances. Finally, a series of lake tests using the LP-AUV are conducted to validate the proposed method.

Design and Test of Sowing Depth Measurement and Control System for No-Till Corn Seeder Based on Integrated Electro-Hydraulic Drive

An electro-hydraulic profiling mechanism has been gradually applied to provide suitable downforce for a no-till row unit and to ensure the consistency of the seed sowing depth. In order to improve the control effect of the sowing depth system and solve the problems of a complex structure, scattered valve sets and equipment suitability of an existing electro-hydraulic row unit, this paper takes the 2BJ-470B no-till row unit as the carrier and innovatively designs an integrated pressure-reducing cylinder (IPRC) based on electro-hydraulic technology by analyzing the sowing depth control process of an electro-hydraulic seeder. In addition, we develop the integrated electro-hydraulic-driven sowing depth measurement and control system. Combined with the feedforward compensation PID control algorithm, the dynamic regulation of the downforce is realized with the IPRC. The field test shows that under the setting of a sowing depth of 50 mm and a vehicle speed of 9~10 km·h−1, the qualified rate of the sowing depth under the three adjustment methods of self-weight adjustment, spring adjustment and electro-hydraulic adjustment is 89.2%, 96.7% and 98.6%, respectively, and the corresponding maximum coefficient of variation of the sowing depth is 16.7%, 12.9% and 6.4%, respectively. The seed groove environmental qualification rate (SFEQ) is further analyzed in combination with the soil compaction, and the mean values of the qualification rates of the three control methods at different vehicle speeds are 88.3%, 91.6% and 98.6%, respectively. The integrated electro-hydraulic-driven row unit has significant advantages over mechanical and self-weight regulation, and its whole machine integration degree and high adaptability realize the comprehensive control of the sowing depth and soil compaction strength.

Model Identification and Control of a Buoyancy Change Device

There are several compelling reasons for exploring the ocean, for instance, the potential for accessing valuable resources, such as energy and minerals; establishing sovereignty; and addressing environmental issues. As a result, the scientific community has increasingly focused on the use of autonomous underwater vehicles (AUVs) for ocean exploration. Recent research has demonstrated that buoyancy change modules can greatly enhance the energy efficiency of these vehicles. However, the literature is scarce regarding the dynamic models of the vertical motion of buoyancy change modules. It is therefore difficult to develop adequate depth controllers, as this is a very complex task to perform in situ. The focus of this paper is to develop simplified linear models for a buoyancy change module that was previously designed by the authors. These models are experimentally identified and used to fine-tune depth controllers. Experimental results demonstrate that the controllers perform well, achieving a virtual zero steady-state error with satisfactory dynamic characteristics.

Ultrahigh-density 3D holographic projection by scattering-assisted dynamic holography

Computer-generated holography offers a promising route to three-dimensional (3D) video displays. To realize a realistic-looking 3D display, the critical challenge is to create a 3D hologram that enables high-density multi-plane projection with full depth control. However, two long-existing issues in current digital holographic techniques, low axial resolution and high inter-plane crosstalk, prevent fine depth control and therefore limit the ultimate quality. Here, we report 3D scattering-assisted dynamic holography (3D-SDH) that further breaks the depth-control limit of the state-of-the-art method. Our approach achieves orders of magnitude improvement in axial resolution and greatly suppresses crosstalk, enabling ultrahigh-density 3D holographic projection. Moreover, 3D-SDH enables dynamic 3D vectorial projections via phase-only holograms. The concept is validated through both simulations and experiments, where dynamic projections of 3D point-cloud objects onto high-density successive planes are demonstrated. Our work opens perspectives for 3D holographic technology with ultra-fine depth control, dynamic projection, and polarization multiplexing functionalities.

FACTORS MILITATING AGAINST AGRICULTURAL PRODUCTIVITY OF CROP FARMERS IN NIGER STATE, NIGERIA

Niger State has the largest landmass in Nigeria. With 8.6 million hectares of land which represents about 9.3% of the total landmass of Nigeria, the state experiences distinct dry and wet seasons with annual rainfall varying from 1,100 mm (120 days) in the northern part to 1,600 mm (150 days) in the southern part. The vegetation, soil and weather patterns are favourable to produce a wide spectrum of food and cash crops of various types. The major crops grown in the State include rice, maize, millet, sorghum, yam, potato, soybean, groundnut, cashew, benniseed and cassava. The primary aim of this study was to investigate the factors militating against agricultural productivity of farmers in production of crops in the state. Both primary and secondary data were used for the study purposes. Descriptive statistics was used on sample of 360 crop farmers. Findings from the study indicates that fertiliser, herbicides, labour, late onset rains and high interest rates are the factors militating against the production of food crops in Niger State. The study thus concluded that, the application of inappropriate agronomic practices such as untimely planting, incorrect plant spacing, wrong method of planting, poor sowing depth, delayed weeding, ineffective pest and disease control, inappropriate use of fertilizers, untimely harvesting, use of low yielding varieties and inconsistent rainfall patterns, will always significantly reduce crop yields.

A constant plunge depth control strategy for robotic FSW based on online trajectory generation

Robotic friction stir welding (RFSW) usually comes with a huge upsetting force, and the stiffness of the welding system distributes unevenly over the position, which leads to a large deviation of the plunge depth of the tool at the end of the robot. The conventional constant distance tracking control suffers from the problem of unsmooth compensation leading to the vibration of the robot and thus degrading the weld quality. For this problem, a constant plunge depth control based on online trajectory generation for RFSW is studied, which can generate an accurate welding trajectory according to the rough initial reference path and smoothly compensate for the plunge deviation. Initially, three laser-ranging sensors are utilized to measure the pose deviation of the tool in real-time and generate the ideal welding trajectory according to the projection vector method. Then, a deformation compensation model is established to realize the real-time prediction of the correct value. To ensure the smoothness and rapidity of the dynamic tracking process of displacement deviation, we adopt an online trajectory generator as the core of optimization control to meet the process constraints such as speed, acceleration, and jerk during the compensation process. Finally, simulation and experiment are carried out. The results show that the proposed method can effectively reduce the vibration caused by compensation during the welding process and reduce flash, which can improve the welding quality.

High-efficiency abrasive water jet milling of aspheric RB-SiC surface based on BP neural network depth control models

High-efficiency abrasive water jet milling of aspheric RB-SiC surface based on BP neural network depth control models

Selection of the Depth Controller for the Biomimetic Underwater Vehicle

The aim of this paper is to select a depth controller for innovative biomimetic underwater vehicle drives. In the process of optimizing depth controller settings, two classical controllers were used, i.e., the proportional–integral–derivative (PID) and the sliding mode controllers (SM). The parameters of the regulators’ settings were obtained as a result of optimization by three methods of the selected quality indicators in terms of the properties of the control signal. The starting point for the analysis was simulations conducted in the MATLAB environment for the three optimization methods on three types of indicators for three different desired depth values. The article describes the methods and quality indicators in detail. The paper presents the results of the fitness function obtained during the optimization. Moreover, the time courses of the vehicle position relative to the desired depth, the side fin deflection angles, the calculated parameters of the control signals, and the observations and conclusions formulated in the research were presented.