Robotic Systems and Applications
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The airflow behavior of light particulate materials during free fall and their impact dynamics on screening surfaces
Full text linkTo optimize the efficiency and noise performance of high-frequency vibrating screens, this study investigates the airflow behavior of lightweight materials during free fall and their impact dynamics on the screening surface. Based on the energy conservation theorem and the characteristics of tobacco screening, a computational model for the air resistance coefficient was derived. KT board specimens were employed as experimental substitutes for tobacco leaves to examine the effects of porosity and geometric dimensions on descent velocity and air resistance. The results indicated that materials with higher porosity exhibited greater descent velocities and lower air resistance, whereas larger geometric dimensions lead to increased aerodynamic drag and higher resistance coefficients. Furthermore, field operational modal analysis revealed that the sieve plate exhibited subharmonic resonances within the 9.9-10 Hz and 20-30 Hz frequency bands under nonlinear excitation. These findings could provide theoretical and data support for structural optimization aimed at noise reduction and screening efficiency enhancement
Structural optimization of bus chassis frame based on proxy model
Full text linkUnder the premise of ensuring modal and strength characteristics, achieving lightweight design of the structure simultaneously has become a key issue of concern for major automobile manufacturers and research institutions. To reduce the mass redundancy of the bus chassis frame, save production costs and energy consumption, a multi-objective optimization scheme based on surrogate model technology was proposed, which could maximize weight reduction without reducing the natural frequency or increasing the peak stress. According to the working principle, load characteristics and composition of the chassis frame, a parametric coupling model for modal and strength was constructed, and the stress, deformation, natural frequency and vibration mode characteristics of the overall structure were obtained. The dimensions of H-steel were determined as design variables, and the discrete mapping data sets of maximum stress, first-order natural frequency and mass were obtained through the Latin square design scheme. Parameters such as the coefficient of determination, adjusted coefficient of determination and root mean square error were selected as the standard evaluation indicators for the accuracy of the response surface model. The reliability of different surrogate models was compared and analyzed, and finally the Kriging model was adopted as the approximation function in the construction of the mathematical model. An optimized mathematical model was constructed to convert the modal and strength objectives into boundary conditions. The design variables meeting the optimization objectives were derived through the sequential quadratic programming algorithm. The results showed that, without reducing the requirements for strength and stiffness indicators, this optimization scheme could reduce the weight of the chassis frame by 9.94 %, which has good economic benefits and engineering value
Experimental study on dynamic load compensation of risers under ultra-low frequency vibration
Full text linkIn the event that a floating drilling platform is struck suddenly by a typhoon, preventing the complete retrieval of the riser, a compensation system is required to alleviate the considerable dynamic loads on the riser resulting from platform movement, thus keeping the riser tension within safe limits. Evaluation of the mathematical model for the conventional vibration isolation system indicated unsatisfactory performance under conditions of large displacement and ultra-low-frequency vibration. To address this, a new dynamic load compensation system for the riser has been developed, along with a dedicated experimental platform. In this setup, platform heave is simulated via the extension and retraction of a hydraulic cylinder, while the riser load is represented using multiple mass blocks. The experimental platform supports both manual and automatic control modes. Utilizing Visual Basic (VB) programming integrated with an Access database, the monitoring and control software provides capabilities for parameter configuration, data monitoring, and data archiving. Experiments performed on this platform, including heavy simulation and dynamic load compensation, demonstrated a compensation effect of 27.4 %. The successful mitigation of dynamic loads on the riser presents a novel approach for drilling platforms to cope with typhoon emergencies and suggests valuable applications for vibration isolation technology in other domains
Research on the relationship between shaft vibration and bearing vibration under complex fault conditions using full vector spectrum
Full text linkShaft vibration and bearing vibration are key indicators for measuring the dynamic characteristics of the rotor and support bearing system, which play crucial role in reflecting the operation performance of the equipment. However, collecting shaft vibration and bearing vibration signals simultaneously often encounters multiple challenges in practical applications, mainly due to limitations in measurement technology, interference from faults, and variability in operating environments. Conducting in-depth research to explore the interrelationship between shaft vibration and bearing vibration is of great significance, which not only could achieve data complementarity and enhance information integrity, but also provide more accurate references for fault analysis and status monitoring. Therefore, this study proposes a method to investigate the relationship between the two under support loose fault state based on integrating homologous information. The study first constructs a dynamic model under support loose fault condition. Then the homologous information is integrated using full vector spectrum technology, which could enhance the accuracy in reflecting the relationship between the shaft vibration and bearing vibration at different speeds. The simulation results reveal that by mastering this complementary relationship, the operating health status of equipment can be inferred based on the trend of some other key parameters even if in the absence of a certain measured signal, and corresponding maintenance and management measures can be formulated accordingly
Predictive vibration diagnostics of helicopter rotating units in field conditions
Full text linkCurrent helicopter onboard monitoring systems are not effective enough, and most helicopters do not even have them. As helicopter unit state is not clearly known, it is subject of preventive maintenance. To maintain helicopters predictively reducing repair costs and time, the techniques are required that allow diagnosing the operating units in field conditions for all helicopters. This work is aimed to practically check the Vibropassport techniques allowing the predictive maintenance on the operating helicopter. The Vibropassport using high-order models considers the spatial vibrations in a wide frequency range, applies diagnostic parameters at the normalized scale, and allows diagnostics using a single field inspection. The main finding of the work is that the Vibropassport-based system adapted to a specific helicopter type allows the detailed diagnostics of the engines, gearboxes and transmissions based on the data of a single test in field conditions. Applicability of the Vibropassport system in field conditions was demonstrated on an operating helicopter, and the vibration-based diagnostics estimates whether the unit state complies with the thresholds common for a wide range of similar units. The Vibropassport-based system makes the predictive maintenance possible, reducing costs of maintenance and repair for helicopters, including those without onboard monitoring systems
Research on the dynamics of a permanent magnet direct-drive bogie with consideration of electromechanical coupling
Full text linkA vehicle–motor coupled dynamic model for a permanent magnet direct-drive (PMDD) axlebox-built-in bogie operating at 120-200 km/h is developed in this study. The model integrates a multibody vehicle system and a PMSM traction system under an SVPWM vector-control strategy to investigate electromechanical coupling effects. The influence of current-loop and speed-loop control parameters on motor output characteristics and vibration transmission is analyzed. Simulation results show that the dominant frequencies of vehicle lateral and vertical vibrations are mainly concentrated in 3-15 Hz, and the vehicle maintains stable dynamic performance during traction. The speed-loop parameters significantly affect the coupled vibration between the motor and the bogie frame and may induce vertical resonance, while the current-loop parameters have minimal impact. Furthermore, the analysis of motor-suspension stiffness indicates that higher stiffness improves high-speed running stability. The proposed model provides guidance for PMDD traction system control optimization and bogie design for 120-200 km/h urban rail trains
Study on craniocerebral dynamic response and helmet protection performance under accompanying shock wave
Full text linkTo systematically investigate the protective effects of helmets against human head injuries under various shock wave conditions, a finite element head-helmet coupling model was developed. This model analyzed how helmets influence biomechanical response parameters, such as intracranial and cranial pressure, when subjected to a single blast wave and its accompanying shock wave. While extensive research exists on single blast scenarios, studies on the more complex and militarily relevant accompanying shock waves, which pose a greater threat due to prolonged loading and multiple reflections, remain scarce. Several impact scenarios were considered, including single frontal impact, positive continuous impacts, successive sidewall impacts, and simultaneous frontal and lateral impacts. The study examined the dynamic changes in brain tissue within a blast environment to assess the efficacy of helmets in protecting the human head. In single frontal impact scenarios, helmets effectively reduced intracranial pressures in the frontal, occipital, and parietal lobes by 32 %, 38 %, and 19 %, respectively, while significantly decreasing the stress peak at the back of the skull. During positive continuous impacts, helmets decreased intracranial pressure in the parietal and occipital lobes by 36 % and 21 %, respectively, although their effectiveness in reducing frontal lobe pressure was limited due to inadequate facial protection. For successive sidewall impacts, helmet protection delayed the blast wave, reducing intracranial pressure in the frontal lobe by 60 kPa but increasing pressure in the parietal lobe by 80 kPa. This alleviated stress on the skull’s rear while increasing stress on the opposite side. In scenarios involving simultaneous frontal and lateral impacts, lateral blasts increased parietal intracranial pressure by 20 kPa, with the right hemisphere experiencing more pressure than the left due to the mitigating effect of reflective side blasts on skull stress. The study found that, compared to single blast waves, accompanying shock waves present a greater risk of cranial injuries due to their prolonged impact. These findings address a critical gap in blast neurotrauma research and provide valuable insights into the biomechanics of head injuries under realistic multi-blast conditions, which can directly inform the design of improved helmets with enhanced protection in complex blast environments. However, because shock waves may originate from multiple directions and elevations, the protective capability of conventional helmets for the facial region remains limited
Impact of underground near surface ore body mining on the stability of overburden and dangerous rock masses
Full text linkIn order to explore the impact of near surface ore body mining on the stability of overburden and surface dangerous rock masses, a Phosphate Mine was used as the engineering background. On-site investigation method was adopted to clarify the stability conditions of the surface dangerous rock. Numerical analysis software was used to simulate the evolution laws of overburden deformation, stress, and plastic zone. The research results indicate that the development of interlayer structural planes in the surrounding rock of the roof of the mining area can easily cause the collapse of the roof slab or sheet. The strata are hard and brittle in lithology, with developed rock fractures. Dangerous rock blocks are formed under the combination of fissures and rock layers. The mining disturbance generated during the mining process is relatively small. The impact on the rock layers, adjacent mining sites, and surface stability is weak. The surface is less affected by the mining of underground ore bodies and has not reached the maximum allowable value. Under the condition of first mining the ph1# ore body and then mining the ph2# ore body, the displacement of the overburden is relatively small. There is no distribution of connectivity in the plastic zone in the mining pillars, mining areas, and overburden. The research results can provide theoretical reference for the feasibility analysis of near surface ore body mining in similar mines
Field evaluation of the geotechnical behavior of lime-ground cushions in the Republic of Tajikistan
Full text linkThe article presents the methodology for conducting field tests of lime-soil cushions to examine the technology of their construction, gain strength, their operation under rigid stamps, and the characteristics of stress-strain state development. The results of field studies showed that the lime-soil mixture can be used as a structural material in the preparation of bases on loess- loess soils in the conditions of the Republic of Tajikistan. Field tests showed that the lime-soil mixture achieved a dry density of 1.53-1.56 t/m3, while the deformation modulus increased by 5-10 times compared to natural loess soils
High-speed roller/rail dynamics and thermodynamics considering surface roughness and revolution
Full text linkConsidering rotation and not considering rotation, a calculation was conducted on the friction and wear between the sliding pair in a high-speed rotating machine using a plane of Ra6.3 and Ra3.2, indicating that Ra3.2 has advantages. In higher firing rate Gatling guns, the guide rail should be processed more finely and have a smaller roughness. The results demonstrate that the stress increases a lot when the bolt is surface rough, which is 11.5 % higher than the flat condition. The temperature of Ra6.3 is about 100° higher than the flat condition. It plays an important role in improving the service life of friction surfaces