Robotic Systems and Applications
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Dual-stator ultrasonic motor achieving 2-DOF linear and rotary motion with single-phase excitation
Full text linkThis study proposes a novel dual-stator linear-rotary ultrasonic motor. The piezoelectric ceramic excites both out-of-plane and in-plane vibration modes within the stator. These distinct vibration modes independently drive the slider (rotor), generating reciprocating linear and rotational motions, respectively. Finite element analysis and laser vibrometer-based vibration testing validated the motor's operational principle. The close agreement between simulated and measured resonant frequencies for both vibration modes, with mere discrepancies of 3 % and 4 %, respectively, underscores the accuracy of the stator’s vibrational characteristics. Subsequently, two stators are fabricated and assembled to the ultrasonic motor prototype. Experimental results demonstrate the motor’s impressive performance, achieving a maximum linear velocity of 265 mm/s and a peak rotational speed of 1600 rpm. Furthermore, the motor delivers a maximum thrust force of 0.18 N and a stalling torque of 1.8 mN·m
Application of unsupervised identification of dissolved gases in transformer oil based on spin coating film making process
Full text linkAddressing the issues of low efficiency and uneven collection of dissolved gases in transformer oil leading to overfitting and poor performance of identification models, we propose a novel film-making process that integrates Gaussian process and unsupervised pre-classification to enhance the recognition efficiency of dissolved gases in transformer oil. This method not only forms a thinner and more uniform separation layer, significantly improving degassing performance and collection efficiency, but also addresses the problems of insufficient data labeling and sample imbalance by introducing the K-means++ clustering algorithm and pseudo-random integration technology, thereby enhancing model robustness and generalization ability. Moreover, the designed Gaussian Process Multi-Classification (GPMC) method employs probabilistic interpretation for result presentation, which increases the accuracy of fault identification. Experimental results show that under consistent starting conditions, the RCC and ARI indicators of our pre-classification method are close to 0.8, with the test set’s recognition rate exceeding 80 %, while the GPMC method misclassified only 2.4 % of the cases in the 1800-case dataset. These improvements make our method particularly effective for handling uncertainties and imbalances in dissolved gas cases in transformer oil, showcasing its potential for practical applications
Feature extraction of rolling bearing based on adaptive variational multi-harmonic mode extraction
Full text linkVariable multi-harmonic mode extraction (VMHME) not only has the advantages of high computational efficiency and extraction accuracy similar to variational mode extraction (VME), but also could extract the multi-harmonic components of periodic narrowband impulse signals in frequency band as wide as possible, making it very suitable for feature extraction in the event of rolling bearing failure. VMHME needs to accurately estimate the fault characteristic frequency of rolling bearing as its prior parameter, and small errors in estimating the fault characteristic frequency will cause significant deviations in the target extraction components. At present, the theoretical fault characteristic frequency of rolling bearings is commonly used as the estimated fault characteristic frequency. However, due to the installation deformation of rolling bearings and the random sliding between the rolling elements and the raceway during operation, it can cause a deviation between the actual fault characteristic frequency and the theoretical fault characteristic frequency. The most scientific and effective method is to enable VMHME to adaptively obtain the fault characteristic frequency based on the characteristics of the analyzed signal itself. Therefore, this paper introduces the envelope harmonic product spectrum (EHPS) theory into VMHME and proposes an adaptive VMHME (AVMHME) method to effectively extract the multi harmonic components of the periodic narrowband impulse signal when rolling bearings fail. Feasibility of the proposed method is verified through simulation and rolling bearing’ early weak fault experiment, and its superiority is also verified through comparative analysis
Vibration velocity control of compound wedge-shaped excavation blasting in tunnels under complex environments
Full text linkThis paper explores the optimization of cutout schemes in tunnel excavation and blasting by introducing an improved segmented wedge-shaped blasting method, validated through both numerical simulations and field tests. The numerical simulations use the ANSYS/LS-DYNA fluid-solid coupling algorithm to analyze the damage effects, effective stress distribution, and vibration characteristics of surrounding rock for both the Conventional wedge cut and the segmented wedge cut methods. The results show that segmented wedge cutting significantly enhances the utilization rate of blast holes, reduces the formation of large gravel fragments, and effectively mitigates surrounding rock vibration velocities. In comparison to the Conventional method, the optimized undercut scheme not only increases blasting efficiency but also greatly enhances the rock fragmentation in the undercut area, thereby ensuring tunnel construction safety. The field test results validate the accuracy of the numerical simulations and show that the enhanced scheme holds significant potential for practical application in real-world projects
Dynamic behaviors and double-frequency synchronization analysis of a dynamic vibration absorption system driven by three co-rotating exciters
Full text linkThe recovery efficiency of drilling fluid is directly affected by working performance of the vibration screen. Therefore, a newly dynamic vibration absorption system driven by different excitation frequencies is designed through double-frequency synchronization theory to improve the mechanical performance of screening equipment. Firstly, the differential equations of motion of vibration system are deduced by Lagrange method. Then, the theoretical conditions of the system implementing double-frequency synchronization are obtained based on asymptotic method, and stability criterion of the synchronization is revealed according to Routh-Hurwitz criterion. Subsequently, the effects of structure parameters on vibration isolation ability, synchronous state, and stability of synchronization are numerically discussed. Finally, the feasibility of the theoretical method and the obtained results is further verified by simulation and experiment. It is found that the vibration isolation and synchronization performance of the system is influenced by the motor parameters and system structure. The system has the best vibration isolation ability when ωm0= 157 rad/s, which is considered as the best operating frequency of the present vibration system. Meanwhile, when the mass ratio κ between the high-frequency co-rotating rotor and the low-frequency co-rotating rotor is smaller, the absolute value of the stability coefficient Si is larger, and the stability phase difference is smaller, and the system is more stable. The present work can provide theoretical direction for the design of new screening equipment
Study on the effect of suspension system friction of heavy-haul freight vehicles on the operation performance
Full text linkDuring the operational life of heavy-haul freight vehicles, the long-term wear between components can affect the suspension parameters. Suspension system wear has a significant effect on the dynamic performance and wheel wear. Experimental tests are performed to measure the changes in suspension system parameters after wear. A dynamic model and wheel wear model of the heavy-haul freight vehicles were established to analyze their dynamics and wheel wear performance. The results showed that with the wear of the suspension system, the stiffness parameters further increase. The dynamic performance of the vehicle system deteriorates after suspension system wear, with a decrease in the critical speed and an increase in safety and ride indexes. The analysis also reveals that the wheel wear increases as the stiffness parameters increase after the suspension system wear. This paper provides a basis for maintaining heavy-haul freight vehicle suspension systems
Design peculiarities and kinematic analysis of a shaking conveyor with multiple transporting and screening trays
Full text linkThe paper focuses on the design peculiarities and kinematic analysis of a novel shaking conveyor equipped with three interconnected transporting and screening trays. The goal is to develop a comprehensive mathematical model to describe the system’s motion and analyze the interplay between the trays, providing a basis for improved design and optimization. The scientific novelty lies in the detailed kinematic study of this specific multi-tray configuration, particularly the interaction of the dual beam systems actuating the intermediate tray, leading to complex coupled motion profiles. The practical value of the research is substantial for designing and optimizing such multi-functional vibratory equipment, as the kinematic data (displacements, velocities, accelerations) provide critical insights into material-tray interaction, aiding in predicting and enhancing material processing efficiency, estimating inertial loads for robust structural design, and informing vibration isolation strategies. The methods employed include the development of a kinematic diagram and corresponding motion equations for the multi-loop linkage mechanism, followed by numerical modeling of the system’s motion using Wolfram Mathematica software. The main results characterize the complex motion profiles for a steady-state operational frequency of 10 Hz, revealing distinct amplitudes and near-linear inclined trajectories for key hinges representing each tray. Notably, the upper tray exhibited the most significant displacements and accelerations, with horizontal accelerations reaching approximately 3 g and vertical accelerations around 1.3 g, indicating a motion profile conducive to effective material lifting, “throwing”, and bed stratification. Scopes of further research include a complete dynamic analysis incorporating mass properties and driving forces, experimental validation of the models, optimization of geometric and operational parameters, integration with Discrete Element Method (DEM) simulations for detailed material flow analysis, and investigations into wear, fatigue life, and advanced control strategies
Mathematical modeling of the rotating drum granular fill flow oscillatory stability
Full text linkDrum-type machines have become widely used in many industries for processing various granular materials. An innovative direction for significantly increasing the energy efficiency of such equipment is the use of self-oscillating working processes. Self-excitation of auto-oscillations allows you to bring into pulsating flow and activate the passive part of the intra-chamber filling and significantly enhance the interaction of granular particles with each other and with the surrounding environment. The purpose of the study is to build a mathematical model of the conditions and factors of oscillatory instability of the flow of polydisperse granular filling in the chamber of a rotating drum. The research methodology includes analytical modeling of wave processes and experimental modeling of manifestations of instability of the filling flow. The inertial mode of flow of the active part of the filling in a shear flow state is analyzed, the behavior of which is described using averaged values. Based on the results obtained, an increase in instability with an increase in the dilatancy of the medium during deformation is established and the destabilizing effect of the damping action of the fine fraction on the interaction of particles of the coarse fraction is revealed. The main scientific novelty of this study is the identification of the regularities of the unsteady motion of the oscillatory system of a filled drum. The study confirms the possibility of generating, under certain conditions, self-excitation of auto-oscillations of the intra-chamber filling, which is a decisive factor in the predicted intensification of the technological process. The results obtained are valuable for researchers and engineers involved in the study and design of innovative energy-efficient working processes of drum machines
Analysis on the influence of blade pitch angle on dynamic characteristics of the rotor system
Full text linkAt present, few studies focus on variable-pitch fans for small-to-medium turbofan engines, with most relying on hydraulic actuation that fails to meet strict environmental and efficiency demands. This paper analyzes an electrically actuated lead-screw servo-motor-driven variable-pitch fan rotor: at 1×10⁷ N/m support stiffness, the first critical speed exceeds the operational range and pitch angle’s influence is negligible, peak unbalance response is 1.22×10⁻⁶ m linearly decreasing with pitch angle, and vibration analysis avoids resonance. Results confirm the electric pitch-change concept’s feasibility
The effect of the quantity and length of fibers on the mechanical properties of fiber-reinforced concrete based on polypropylene fibers
Full text linkIn these studies, the effect of polypropylene fibers on the mechanical properties of concrete was studied, and special attention was paid to determining their optimal amount and acceptable length. The fibers were added to the concrete composition in amounts of 0.1-0.5 % and lengths of 10, 20, 30, 40, 50 mm and tested. According to the results of the study, the highest results were recorded at a fiber content of 0.2-0.3 % and lengths of 20-30 mm, and the compressive strength of concrete increased by up to 15.9 % compared to ordinary concrete. When adding fibers in excess (≥ 0.4 %) or with a length of 50 mm, a decrease in strength was observed. The results obtained showed that it is possible to increase the quality and improve the strength of concrete by selecting the optimal parameters of polypropylene fibers