Indoor Experimental Results Research Articles

Numerical Simulation Analysis of Dock Bank Slopes’ Soil–Water Interface Recognition and Monitoring Device Models Based on Heat Transfer Principles

The erosion and sedimentation of bank slopes are important factors affecting the safety of wharf operations. The essence of bank slope monitoring is to identify the water–soil interface. This paper proposes a model for soil-and-water interface identification and monitoring equipment buried on the bank slope of the wharf, based on the difference in thermodynamic heat transfer between water and soil media, and presents the results of multi-condition numerical simulation. The comparison between numerical simulation results and indoor experimental results shows that the overall patterns are consistent, with an error of less than 11.4%, which is lower than the deviation between theoretical calculation results and indoor experiments. Based on the accuracy of the numerical calculation results, the temperature rise and propagation characteristics of linear heat sources made of iron and PVC in eight types of cohesive soils and six types of non-cohesive soils were studied. The results indicate that there are significant differences in the temperature distribution of linear heat sources made of iron and PVC in both water and soil media. The monitoring equipment model based on the difference in heat transfer between water and soil can be applied in practical engineering. This provides a foundation for the design and application of subsequent monitoring equipment.

Study on the influence of temperature on the damage evolution of hot dry rock in the development of geothermal resources

In order to more accurately understand the rock mechanics properties of hot dry rock (HDR) reservoirs under high-temperature conditions and further guide the drilling and construction of HDR wells, conducting research on rock damage evolution under high-temperature conditions plays a guiding role in the efficient development of geothermal resources. To reveal the evolution law of fracture damage of HDR under temperature influence, taking marble as an example, the thermo-mechanical damage and failure mechanism under the conditions of 30 °C, 60 °C, 90 °C, 120 °C and 150 °C were studied using a rock high-temperature rheometer and an acoustic emission (AE) testing system. The numerical simulation results were compared with the indoor experimental results by combining the particulate flow program Particle Flow Code 3D (PFC3D) to verify the effectiveness of the simulation analysis model of thermo-coupled particulate flow at the micro scale. The results show that under high temperature, the marble three-axis compression failure passes through the compaction and elastic deformation stage, plastic deformation stage, ductile failure stage and instability failure stage, and the peak strength and elastic modulus of the marble decrease with the increase of temperature, and the acoustic emission b-value of the sample can judge the damage evolution process of the marble. At the micro scale, high temperature accelerates the force chain transmission between particles, the contact force between marble particles gradually decreases during the heating process, and the number of particle bonding failures increases steadily; the bearing capacity and elastic modulus attenuation of the rock are the result of microcrack evolution, and the force chain void zone and particle displacement field inside the sample are consistent with its macroscopic failure form. The development of microcracks in marble under different test loading conditions is different, and with the increase of test temperature, the total number of cracks inside the sample increases, but the proportion of shear cracks decreases, the activity of particle displacement increases, and the “plastic extension” characteristic of marble becomes more significant. The thermal damage evolution of marble was quantitatively analyzed based on the elastic modulus method and the peak stress method, and the damage evolution law of marble under different temperatures was obtained.

Discrete element analysis of heating transfer characteristics of airport pavements by using electro thermal method for snow melting and deicing

This study presents a discrete element investigation on the internal temperature change characteristic and heat transfer efficiency in airport concrete pavement by using the carbon fiber electrothermal method for snow melting and deicing. A discrete element model for snow melting and deicing of airport concrete pavement by using the carbon fiber electrothermal method was generated. The temperature evolution on the surface of the pavement was captured and compared with the indoor experimental results. The numerical simulation results were in good agreement with the experimental results, which verified the applicability of the numerical model. On this basis, the effects of the heating temperature and heating paths on the internal heat conduction and temperature field distribution were investigated. The results showed that the temperature of the pavement surface and the temperature rise gradient are linearly related to the temperature of the carbon fiber heating wire. The initial heating time has little influence on the temperature rise path of the road surface layer after stopping heating and reheating. The temperature of the road surface layer rises slowly after the heating is stopped, and then decreases linearly at a rate of 0.4 °C/h not corresponding to the initial heating time.

Research and Development of Steel Fiber Reinforced Concrete Filling Material and Its Application in Gob-Side Entry Retaining Technology in Deep Mines

Against the background of the prevailing green development paradigm, numerous coal mines have embraced the adoption of gob-side entry retaining mining technology. The most commonly employed form of gob-side entry retaining involves building an artificial wall along the edge of the goaf behind the working face to maintain the roadway. The pivotal challenge in gob-side entry retaining lies in the roadside support. Currently, commonplace concrete serves as the predominant material for the roadside filling body. Nevertheless, traditional concrete exhibits drawbacks, including inadequate tensile strength and poor toughness, leading to wall cracks or even collapses in the retaining wall. Steel fiber, a frequently employed reinforcement and toughening agent in concrete, has found widespread application in the construction sector and other fields. However, its use as a roadside filling material in underground coal mines remains infrequent. Therefore, in this paper, the flow and mechanical properties of steel fiber concrete were tested and analyzed, and field industrial tests were conducted. Results of indoor experiments show that steel fibers reduce the slump of concrete. The addition of steel fibers shifted the pore compacting stage, linear elasticity stage, and destabilization stage forward and improved the post-peak bearing capacity. The addition of steel fibers makes the concrete compressive and tensile strength show a “first increase and then decrease” trend; both peaked at 1.5%, and the increase in tensile strength is more pronounced. Steel fibers enhance the strength of compressive strength of concrete at an early age, weaker at a late age, and tensile strength inversely. The addition of steel fiber can change the concrete matrix from tensile damage to shear damage, and the toughness index shows the trend of “first increase and then decrease”, and reaches the peak value when the dosage is 1.5%. Industrial test results show that steel fiber concrete as a roadside filling body can reduce the surrounding rock surface displacement and bolt (cable) force.

Study on fracture characteristics and mechanisms of red sandstone under high-voltage pulse discharge

To investigate the influences of geometrical size and discharge voltage of the pulse discharge equipment on the fracture characteristics and mechanisms of sandstone under high-voltage pulses, a series of experiments was conducted using a high-voltage pulse discharge device on sandstone circular disc specimens of sandstone with a thickness of 10 mm. These experiments covered a range of disc diameters ranging from 50 mm to 142 mm and discharge voltages from 15 kV to 40 kV. Through these experiments, the fracture characteristics of sandstone at both macroscopic and microscopic levels were investigated. In the experiments, a quantitative analysis of surface fracture was undertaken based on fracture density and fractal damage. Additionally, using the principle of energy equivalence, numerical simulation methods were used to study the damage evolution process in sandstone. The research results indicate that the formation and distribution of fractures in the sandstone specimens are significantly affected by geometrical size and discharge voltage. By analyzing the interaction between stress waves and fracture propagation, combined with indoor experimental results, the fracture mechanism was revealed. The high temperature and shock wave generated by the plasma channel leads to the crushing zone near the electrode, while the circumferential tensile component of the stress wave can result in radial fractures, and the reflected tensile wave leads to circumferential and radial fractures near the boundary.

Design of an axial hydrocyclone for preliminary water separation using CFD, RSM, and SUS

Preliminary water separators can effectively solve the problem of high-water-cut produced fluids in oil wells. In this study, we propose a co-design method for the serialization of an axial inlet preliminary water separator based on the combination of cyclone separation theory, computational fluid dynamics (CFD) simulations, response surface method (RSM) optimization, experimental verification, and a scale-up strategy (SUS). For an inlet water cut ≥ 70%, the water separation rate was ≥ 50% and the oil concentration of heavy phase outlet (HPO) was ≤ 1000 mg/L. The indoor experimental results indicated that the performance of the preliminary water separator could achieve better results obtained through the CFD simulation results were taken as sample points and the optimal structural size was found by machine learning method (MLM). The field pilot test results showed that the Hy similarity criterion based SUS did not affect the separation effect. For water cut in the range of 85.0–92.7%, the water separation rate was ≥ 50% and the HPO oil concentration was < 1321.6 mg/L. Our results can provide reference and guidance for the design and optimization of hydrocyclones for preliminary water separation of oilfield produced fluids.

Automatic Suppression Method for Water Surface Glints Using a Division of Focal Plane Visible Polarimeter.

To address the problem of water surface detection imaging equipment being susceptible to water surface glints, this study demonstrates a method called De-Glints for suppressing glints and obtaining clear underwater images using a division of focal plane (DoFP) polarimeter. Based on the principle of polarization imaging, the best polarization angle and the image corresponding to the minimal average gray level of each pixel are calculated. To evaluate the improvement in image quality, the index E was designed. The results of indoor and outdoor experiments show that the error of the angle calculation of this method is within 10%, and the minimum error is only 3%. The E index is positively improved and can be relatively improved by 8.00 under the interference of strong outdoor glints, and the method proposed in this paper shows a good adaptive ability to the dynamic scene.

Numerical Analysis of Perforated Symmetric Fissures on Mechanical Properties of Hole-Containing Sandstone

The symmetrical fissures located within the surrounding rock of the roadway (borehole) in tunnel engineering activities can easily induce damage and instability of the surrounding rock. Therefore, studying the impact of perforated symmetrical fissures on the mechanical properties of rock with a hole has significant practical significance. Based on indoor experimental results, conventional triaxial compression simulations were performed on symmetrical fissure-hole sandstone using PFC2D. The impact of the dip angle and length of symmetric fissures on the mechanical properties of the hole-containing sandstone was analyzed. Furthermore, the relationship between crack propagation and the macroscopic mechanical properties of the specimen was discussed. The results show that: (1) The deterioration effect of symmetric fissures on hole-containing sandstone can be controlled by increasing the fissure dip angle, suppressing the stress drop phenomenon. However, increasing the fissure length exacerbates the deterioration effect. (2) The effect of symmetrical fissure dip angle on the displacement field near the hole decreases with increasing dip angle while increasing fissure length exacerbates the effect of fissures on the displacement field. (3) As the angle between the fissure and the vertical principal stress increases, the degree of tensile failure weakens while the degree of shear failure increases. (4) During the crack development phase, the extension of the stress concentration zone drives rapid crack growth. It exhibits a stress drop in the macroscopic mechanical properties, followed by the evolution of the stress field with loading, allowing rapid expansion of the microcracks and eventually leading to rock destabilization damage.

Experimental and numerical study on the mechanical behaviors and crack propagation of sandstone containing two parallel fissures

For the rocky slope with potential sliding hazard, there are a larger number of flaws such as fractures and joints, which greatly affect the stability and safety of the slope. Thus, it is important and relevant to the behavior of fractured rock from a macroscopic and mesoscopic perspective by experiments and numerical simulation. In this paper, the mechanical properties and crack evolution behavior of grey sandstone containing two parallel fissures under the uniaxial compression tests were evaluated by experimental and bond-based Peridynamics (BB-PD) simulation. The results show that with the increase of fissure dip angle, the peak strength, elastic modulus and Poisson's ratio of pre-cracked sandstone samples under uniaxial compression condition gradually increase. At the same time, the total energy, dissipated energy and elastic peak energy of fractured sandstone also increase with the increase of fissure dip angle. In order to validate the experimental findings, a set of calibration parameters were used to model the intact samples using BB-PD. The numerical simulation reproduced the stress–strain curves, mechanical parameters and failure modes of double-fractured sandstone. Based on the results of indoor experiments and numerical simulations, it is concluded that the failure mode of double-fractured sandstone has three types under uniaxial compression: tensile failure, shear failure and conjugate shear failure. As the fissure dip angle increases, the main control factor for failure of sample gradually changes from rock bridge failure to secondary crack coalescence, and the stress distribution of fractured sandstone gradually changes from high stress concentration in the rock bridge zone to uniform stress distribution as a whole.

Effect of Wavefront Distortion on the Performance of Coherent Detection Systems: Theoretical Analysis and Experimental Research

Atmospheric turbulence causes signal beam wavefront distortion at the receiving end of a coherent detection system, which decreases the system mixing efficiency. Based on the coherent detection theory, this study establishes a mathematical model of wavefront distortion with mixing efficiency and mixing gain. It also analyzes the improvement limits of wavefront correction on mixing efficiency and mixing gain under different atmospheric turbulence intensities and experimentally measures them. Simulation results show that the mixing efficiency can be improved to 51%, 55%, and 60% after correcting for tilt, defocus, and astigmatism terms, respectively, when turbulence intensity D/r0 is 2. The mixing gain with homodyne detection is 3 dB higher than heterodyne detection. Meanwhile, the wavefront correction orders required for optimal mixing efficiency are higher than the heterodyne correction order. In the experiment, Haso4 NIR + DM 40 was used, and the turbulence intensity D/r0 was 2. After the closed-loop control algorithm corrects the tilt, defocus, and astigmatism terms, the indoor experimental results showed that the mixing efficiency is improved to 36%, 47%, and 62%, respectively. The outdoor experimental results showed that the mixing efficiency improved to 36%, 51%, and 68%, respectively.

ORB-Livox: A real-time dynamic system for fruit detection and localization

Accurate fruit localization plays an essential role in many agricultural tasks and is one of the most vital components of an autonomous harvesting robot. Although fruit localization in stationary conditions has been extensively studied, the method to perform fruit localization in dynamic conditions is rarely studied. Fruit localization under dynamic conditions is much more challenging, since movement will introduce continuously irregular ego-motion on visual sensors, which can lead to considerable accuracy degeneration or even system failure. However, fruit localization under dynamic conditions is an essential task since it can significantly improve the harvesting efficiency. In this study, a fruit localization method is proposed to perform accurate fruit localization under dynamic conditions. Firstly, an ORB-SLAM3 SLAM algorithm is utilized to estimate the camera’s pose under dynamic conditions. Secondly, YOLO-V5 is used to identify apples in RGB images. Moreover, Lidar is used to measure the depth of each apple accurately. Finally, a clustering technique based on the Gaussian distribution is proposed to mitigate the accuracy loss under dynamic conditions to optimize apple positions. Our method is extensively evaluated in indoor and outdoor experiments. The results of indoor experiments show that the average localization error is 21.1 mm, with 90% of the errors are less than 30 mm. The experimental result in an orchard environment demonstrates that our proposed method can detect and localize apples under dynamic conditions in unstructured natural environments.

Evaluation of Surface Crack Development and Soil Damage Based on UAV Images of Coal Mining Areas

Coal mining is necessary for the development of society but at the same time causes ecological damage that must also be repaired based on science. In the arid and semi-arid regions of northwest China, surface cracks are one of the major geo-environmental problems caused by coal mining, and studies are urgently needed to determine how to effectively repair them in a scientific manner. The rapid development of unmanned aerial vehicle (UAV) remote sensing technology in recent years has resulted in a good source of data for acquiring feature information on surface cracks. Existing studies mainly focus on high-precision crack extraction methods, and there are few studies on the methods for evaluating cracks. However, clarifying the degree of cracks requiring repair and what repair measures are required through scientific and reasonable evaluation methods is necessary to formulate effective crack repair and land reclamation plans. Given these considerations, in this study, the degree of both crack development and soil damage were evaluated based on the crack extraction results of UAV images. Based on the results of indoor experiments and field measurements, the grading criteria for the degree of crack development and soil damage were constructed. Crack density was used as the evaluation index for the degree of crack development (slight: &lt;0.4%, moderate: 0.4–2%, severe: &gt;2%). The distance between soil and cracks was the basis of the evaluation index for the soil damage degree (severe damage area: &lt;0.6 m; slight damage area: 0.6–1.2 m; no obvious damage area: &gt;1.2 m). Through the results from evaluating the degree of both crack development and soil damage in the study area, it was found that the degree of crack development was mainly moderate and located in the northern crack zone of the study area, with the cracks and damaged soil showing a striped pattern in the east-west direction. Combining the evaluation results of crack development and soil damage, the ecological restoration model of “natural restoration + crack filling + water supplementing + vegetation planting” is proposed. We conclude that crack repair should be applied in areas where moderate and severe cracks have developed, whereas soil repair should target the soil within 1.2 m of the cracks in the above area. This study is the first attempt to construct and evaluate the classification criteria of crack development degree and soil damage degree from the perspective of cracks and soil, and the results are of guiding significance for land reclamation in mining areas.

Near-bit apparent resistivity measurement method based on SPWM excitation

In order to improve the measurement accuracy of near-bit apparent resistivity and its measurement range, this paper excites the underground transmitting antenna by a sinusoidal pulse-width modulated (SPWM) current excitation method, which can improve the response of the receiving antenna and circuit in the resistivity measurement system under the usual square wave excitation, thus improving the measurement accuracy of near-bit apparent resistivity. In this paper, the effect of square wave, SPWM wave and sine wave excitation on resistivity measurement was studied, and the modulation algorithm and hardware control are programmed by DSP (Digital Signal Processor), and the SPWM signal is output by full-bridge inverter circuit and tuned antenna. The indoor experimental results show that the near-bit apparent resistivity measurement method based on the SPWM wave pulse excitation can achieve the measurement in the range of formation equivalent resistor value of less than 600kΩ. There is a high trend matching between near-bit apparent resistivity LWD curve and RT resistivity curve of well completion electrical logging in field tests of formation resistivity less than 2000Ω·m, which proves that the method can improve the accuracy of near-bit apparent resistivity measurement.

Investigation on Surface Crack Resistance and Curing Measures of Airport Cement Concrete Pavement during Construction in Strong Wind and High Temperature Weather

The airport cement concrete pavement is prone to surface shrinkage cracks during construction under strong wind and high temperature conditions. Based on this, in this paper, the influence effects and mechanisms of curing methods on early shrinkage and crack resistance of concrete were investigated through indoor tests to simulate strong wind environment and high temperature environment in summer, and the applicability of different curing methods in engineering practice was verified by on-site experiments. The indoor experiment results demonstrated that the concrete was more prone to cracks under strong wind than under high temperature. The indoor and on-site experimental results showed that it was difficult to ensure a crack-free concrete surface by employing traditional geotextile, simply spraying curing agent or using only water-saving moisturizing curing film, among them, utilizing composite geotextile curing film has the best anti crack effect. In addition, incorporating polymer water absorbent resin enables the concrete to be cured internally, so it can be used as a supplementary curing measure to further improve the crack resistance of concrete in strong wind and high temperature weather.

Investigation of a tunnel magnetoresistance based vector magnetometer for magnetic anomaly detection

The development of high-performance and miniaturized magnetometers is important for small-scale target magnetic anomaly detection. In this work, a miniaturized three-axis vector magnetometer based on the tunnel magnetoresistance (TMR) technique is investigated for magnetic anomaly detection. First, the miniaturized three-axis TMR vector magnetometer is constructed, and then, the limit of detection tests and the magnetic anomaly detection tests are performed. The indoor experimental results show that the proposed magnetometer can capture the magnetic anomalies higher than 3.9 nT, with the low-frequency equivalent magnetic noise of 46.89 pT/√Hz@1Hz. The outdoor experimental results show that the proposed magnetometer can effectively detect small-scale magnetic targets such as hammers at a distance of about 1.5 m. With the advantages of small size, low power consumption, and high magnetic measurement sensitivity, the TMR magnetometer has great application prospects for long-term magnetic anomaly monitoring, high-density magnetic imaging, and other fields.

Bioavailability, (im)mobilization kinetics, and spatiotemporal patterns of arsenic and cadmium in surficial sediments of a river–estuary–coast system

• High-resolution distributions of DGT-labile As, Cd, Fe, Mn and S are determined. • Fe cycling dominates As mobility, while aerobic OM oxidation controls Cd mobility. • Terrigenous input and redox condition trigger the contrasting seasonal availability of As and Cd. • Cd bioavailability evaluated by DGT clearly increases with salinity gradient. The mobility and bioavailability of toxic arsenic (As) and cadmium (Cd) in sediments are crucial to aquatic ecosystems, while their geochemical transitions and spatiotemporal patterns associated with manganese (Mn), iron (Fe), sulfur (S) and salinity in a river–estuary–coast system are yet largely unexplained. In this study, seasonal field investigation and salinity-dependent indoor experiments were combined using the diffusive gradients in thin films (DGT) technique to measure DGT-labile species from the simultaneous river-estuary-coast interface. The results revealed that As and Fe presented a strong coupling for both DGT species and solid phases, suggesting that As mobility was exclusively regulated under the redox transition of Fe. Unlike other chemicals, the relative enrichment of DGT-labile Cd in surface layers and the close affiliation between sediment Cd fractions and organic carbon indicated that Cd remobilization was largely associated with the aerobic decomposition of organic matter. In addition, the seasonal availability of As and Cd tended to be influenced by terrigenous input and redox condition. The indoor experiment results of an inconspicuous increase in DGT-labile As, and a steady increase in DGT-labile Cd with rising salinity confirm that the bioavailability of Cd evidently increased with salinity gradient, however, the effect of salinity on As remained further debatable. Nevertheless, a model simulation validated that this salinity-dependent Cd mobilization was suboptimal for sustaining a continuous Cd resupply from the sediment to porewater, particularly under limited labile Cd pools. Therefore, with expanding global marine hypoxia and sea level rising, this study highlights that As and Cd redox geochemistry in dynamic estuarine sediments should receive more attention, considering their distinctly contrasting (im)mobilization kinetics.

An anti-jamming method against interrupted sampling repeater jamming based on designing transmitted waveforms and receiving filters for simultaneous polarimetric radar

The realistic false targets caused by the interrupted sampling repeater jamming can obscure the real target echo, resulting in radar target detection failure. In this paper, based on reducing the energy of the interference signal after the pulse compression operation, a method is first proposed to suppress the interrupted sampling repeater jamming by jointly designing the transmitted waveforms and receiving filters for the simultaneous polarimetric radar. The joint design optimization problem is formulated by minimizing the energy of the sidelobes of the pulse compression output signal with the constant modulus constraint. An alternately optimized iterative algorithm is proposed to optimize the transmitted waveforms and receiving filters, respectively. Numerical and indoor experimental results are presented to show the effectiveness of the proposed method to suppress the interrupted sampling repeater jamming.

Desert label development for improved reliability and durability of photovoltaic modules in harsh desert conditions

We present strong arguments and experimental findings for the definition of a photovoltaic module accelerated ageing procedure for high irradiance and desert conditions to create a Desert Label for the particular Atacama Desert climatic conditions. A special focus on high ultraviolet solar radiation dosage in combination with either damp heat, salt mist or aggressive thermal cycling are presented. Indoor experimental results, strengthened by outdoor monitoring of sister mini-modules at the Atacama Desert, allowed selecting the appropriate ageing tests while exploring the reliability and durability of a wide range of module configurations, including various typical encapsulants, high efficiency cell technologies and module designs, for industrial applications.

Crowdsourcing-Based Indoor Localization With Knowledge-Aided Fingerprint Transfer

Precise indoor localization is a key requirement for the fifth-generation (5G) and beyond wireless communication systems with applications. To that end, many high accuracy signal fingerprint-based localization algorithms have been proposed. Most of these algorithms, however, face the problem of performance degradation in indoor environments, when the propagation environment changes with time. In order to address this issue, the crowdsourcing approach has been recently adopted, where the fingerprint database is frequently updated via user reporting. These crowdsourcing techniques still require precise indoor floor plans and fail to provide satisfactory accuracy. In this paper, we propose a low-complexity self-calibrating indoor crowdsourcing localization system that combines historical fingerprints with frequently updated fingerprints for high precision user positioning. We present a multi-kernel transfer learning approach that exploits the inner relationship between the historical and updated channel state information (CSI). Our indoor laboratory experimental results using Nexus 5 smartphones at 2.4GHz with 20MHz bandwidth have shown the feasibility of the proposed approach to achieve about one-meter level accuracy with a reasonable fingerprint update overhead.

A novel Stereo-IMU system based on accurate pose parameterization of two-wheeled inverted pendulum (TWIP) robot in localization and mapping

PurposeThis paper aims to propose a method to solve the problem of localization and mapping of a two-wheeled inverted pendulum (TWIP) robot on the ground using the Stereo–inertial measurement unit (IMU) system. This method reparametrizes the pose according to the motion characteristics of TWIP and considers the impact of uneven ground on vision and IMU, which is more adaptable to the real environment.Design/methodology/approachWhen TWIP moves, it is constrained by the ground and swings back and forth to maintain balance. Therefore, the authors parameterize the robot pose as SE(2) pose plus pitch according to the motion characteristics of TWIP. However, the authors do not omit disturbances in other directions but perform error modeling, which is integrated into the visual constraints and IMU pre-integration constraints as an error term. Finally, the authors analyze the influence of the error term on the vision and IMU constraints during the optimization process. Compared to traditional algorithms, the algorithm is simpler and better adapt to the real environment.FindingsThe results of indoor and outdoor experiments show that, for the TWIP robot, the method has better positioning accuracy and robustness compared with the state-of-the-art.Originality/valueThe algorithm in this paper is proposed for the localization and mapping of a TWIP robot. Different from the traditional positioning method on SE(3), this paper parameterizes the robot pose as SE(2) pose plus pitch according to the motion of TWIP and the motion disturbances in other directions are integrated into visual constraints and IMU pre-integration constraints as error terms, which simplifies the optimization parameters, better adapts to the real environment and improves the accuracy of positioning.