Lost motion was used to characterize the transmission quality of the reducers. Testing methods can be divided into static and dynamic tests. The relationship between the two methods and whether the test results can be unified is a long-standing problem in the field of gear engineering. It was found that the loading rate dependence of the reducer hysteresis, which has often been overlooked, is an important factor affecting the unification of the two methods. In this paper, we will study the conditions for unifying two testing methods. In this study, an analysis has been done of the principles of static and dynamic tests by investigating the loading rate dependence of the reducer hysteresis. The results of this study demonstrate that the unification condition of dynamic and static tests of reducers is a loading rate of 0. However, this condition is an ideal state. Experiments have been carried out using small and large reducers as examples. The results verified the influence of loading rate dependence on the static test of the reducer, and the conclusion drawn is that the results of the two methods can only be verified against each other, but not unified. Finally, it has been pointed out that the results of the dynamic test methods have more accuracy and are valuable in theoretical and engineering applications.

To enhance the impact resistance and design flexibility of mechanical metamaterials, this study constructed two secondary structures, CTDC-1 and CTDC-2, by combining chiral three-dimensional double-arrow unit cells (CTDC). Subsequently, four compression-torsion structures (CTDC-11, CTDC-12, CTDC-21, and CTDC-22) were derived through different combinations of these secondary structures. The energy absorption performance of the design under different impact velocities was analyzed through experimental and simulation methods. Its impact resistance was highlighted by comparisons with non-torsional and traditional metamaterials. The analysis results showed that the proposed structure could precisely regulate deformation modes and stress-strain responses through the combination of secondary structures, which significantly expanded the design flexibility of the structure in terms of energy absorption performance. The optimal combination could be flexibly adjusted for different impact velocities, and the performance was superior to traditional structures over a wide range of velocities. By incorporating the compression-torsion effect, the structure designed in this study significantly reduced the initial peak stress while maintaining impact resistance no lower than that of non-torsional structures, with a maximum reduction of up to 61.4%. This is due to the increase in structural densification strain caused by compression-torsion effect and the smaller elastic modulus. This study provides a new solution for impactresistant design over a wide range of velocities.

In modern industrial applications, gears serve as pivotal transmission components, whose transmission performance is critical to operational stability of mechanical systems. For electric vehicles subject to stringent noise control specifications, the suppression and control of gear transmission noise carry heightened importance. To tackle gear noise at its root cause, this paper regards gear deviations as the primary excitation source of vibration and noise and systematically analyses six typical gear deviation shapes as well as the corresponding tooth-pair change-over characteristics in meshing. In addition, the mechanism of formation of the corner contact phenomenon and its influential effect on gear transmission errors are being investigated in depth. On this basis, in this paper a novel least-squares sine wave fitting method is proposed. The results demonstrate that the proposed method can effectively achieve the separation and quantitative characterisation of diverse gear deviations. Meanwhile, this paper conducts an in-depth analysis of transmission errors in noise-causing gears, verifying that eccentricity error, pitch deviation and tooth surface texture of gears are the key influencing factors dominating transmission errors and subsequent noise excitation. This research provides a refined analytical paradigm and reliable technical support for the precision quality evaluation and noise fault diagnosis of gears.

As demands for surface integrity and service performance of bearing steel in high-end manufacturing sectors increase, traditional grinding faces challenges in lubrication and thermal damage control. This paper proposes a multi-stage composite processing method combining laser texturing with form grinding. A biomimetic spider-web-like laser microchannel structure is constructed on the surface of GCr15 bearing steel. Three treatment schemes: UTG (unlasered), TG (single-stage laser followed by grinding), and DTG (dual-stage laser composite grinding), are designed to investigate their effects on surface properties. Results demonstrate that the biomimetic structure enhances chip evacuation, reduces heat accumulation, and improves lubrication and heat transfer conditions. Compared to UTG, the TG process reduces surface roughness by 33.05

Central and local governments in China have issued various plans and policies to promote the development of the humanoid robot industry. Humanoid robot technology has rapidly developed recently, but some technical difficulties still exist. The quasi-direct drive actuator has the advantages of fast response speed, low cost, and high safety. It was tried to be applied to humanoid robots, but the theoretical research of its transmission transparency was not enough, which affected its large-scale industrialization. The research status of transmission transparency of quasi-direct drive actuators for humanoid robots at home and abroad was analyzed, and the definition of transmission transparency was proposed. The model of transmission transparency of a quasi-direct drive actuator was established, and its influencing factors were explored. The evaluation index of transmission transparency of the quasi-direct drive actuator was proposed, and the experiment scheme and method were designed. This investigation was significant for promoting the technological progress and industrial landing of quasi-direct drive actuators.

In laser-tracing measurement systems, maintaining the high positional accuracy of the mechanical assembly is crucial for obtaining precise measurements. To evaluate the assembly accuracy of such systems, this study proposes a torsor-based Jacobian method tailored to the gimbal-style 2-degree-of-freedom rotary mechanical structure. We derive an assembly-error transmission model using a Jacobian matrix and small-displacement torsor (SDT) representation that encompasses planar features, cylindrical features, and their parallel combinations; this leads to the development of a comprehensive model for analyzing the axis-assembly accuracy of the laser-tracing measurement systems. We conducted Monte Carlo simulations on the computed results to simulate realistic assembly errors. Simulation and experimental results demonstrate that the coaxiality accuracy of the rotary axis is 8 mu m, while that of the pitch axis is 9 mu m, The experimental results show a micrometer-level error when compared to the theoretical analytical predictions. These findings effectively confirm that the proposed method offers a viable qualitative approach for evaluating the assembly accuracy of laser-tracing measurement systems.

This investigation evaluates the performance enhancement of wind turbine gearbox lubrication systems through graphene oxide (GO) nanoparticle additives, a crucial advancement for sustainable energy infrastructure. By integrating computational fluid dynamics (CFD) modeling with empirical testing, the impact of GO particle concentration on lubrication dynamics, self-healing properties, and wear reduction is comprehensively investigated. A specialized nanofluid lubrication test rig was developed to quantify gear wear patterns across varying GO concentrations. The rotating fluid-particle dynamics were precisely simulated using a sliding mesh technique coupled with a VOF-DPM hybrid multiphase approach. Lubricant distribution patterns were characterized at rotational velocities spanning 600-1800 rpm, revealing three distinct nanoparticle behaviors: surface adhesion, centrifugal ejection, and splash dispersion. The nanoparticle-gear interaction mechanism demonstrates intricate dynamics governed by interfacial adhesion, rotational forces, and surface contact effects. For 4 wt% GO concentration, particles exhibit ordered trajectories, contrasting with chaotic movements of 1 wt%. Higher concentrations lead to increased internal collision behavior and coupling force. Furthermore, the experiment demonstrates that nanoparticles potentially diffuse into the metal matrix during friction, improving the selfhealing capabilities. The maximum root wear depth is significantly reduced by 43 %, and the wear volume decreases by 140 % at a 4 wt% GO concentration compared to 2 wt%. These findings highlight the potential of GO-infused nanofluids to improve wear resistance, reduce maintenance costs, and extend the lifespan of wind turbine gearboxes, contributing to the reliability and sustainability of wind energy generation.

Plastic gears have many unique advantages,and have been widely used in smart household,automobile and various fields,domestic and foreign researchers have carried out many studies on the structural design,material characteristics and performances of plastic gears,and formed some standards.A brief overview of the history of plastic gears was given,and the most recent advancements in plastic gear research were presented.These included the pros and cons of plastic gears,creative profile and structure designs,material modifications and applications,injection molding process optimization,new measurement techniques,performance testing and evaluation,and the creation of plastic gear standardization.It's concluded that plastic gear is at an important stage of development,comprehensive performance improvement by new structure design and material applications well as carrying out more deep experimental researches to accurately grasp their behavior and performance are the directions of future plastic gear researches.

Efficient coolant transport is critical for thermal control and surface integrity in high-speed precision grinding, where aerodynamic effects near the wheel surface hinder fluid penetration into the grinding zone. Research indicates that the surface structure of grinding wheels significantly influences the delivery of coolant and lubrication performance. Grooves and directional flow channels on the grinding wheel surface can effectively weaken the air barrier at the grinding wheel-workpiece interface, enhancing coolant infiltration. However, existing studies have primarily focused on single-scale groove structures, leaving a lack of systematic understanding regarding the fluid evolution behavior and guiding mechanisms in hierarchically coupled multi-scale channels. To address this issue, a multi-level vein-structured grinding wheel (MLVSGW) inspired by natural leaf venation was developed and fabricated via picosecond laser processing. Airflow and gas-liquid two-phase flow behaviors were analyzed using CFD based on the RNG k-epsilon turbulence model, and validated through grinding experiments on SiC ceramics. Results show that the hierarchical vein architecture reduces the local pressure peak in the wedge region by 18-25% and increases the effective coolant flow rate by approximately 49%. Grinding temperature and force decrease by 17.6% and 12.4%, respectively, with improved surface integrity. This work provides insight into multi-scale flow regulation and offers a strategy for enhancing cooling performance in highspeed grinding.

The surfaces of glass-ceramic that have been initially machined often exhibit surface irregularities and flaws. These inconsistencies in the surface microstructure of the machined workpiece lead to a series of issues during the polishing process. To address these issues, a polishing method based on liquid gallium infiltrate the glass-ceramics is developed to restrain crack growth and micro-fracture behavior in glass-ceramic materials. The process involves penetrating liquid gallium metal into the surface defects of the glass ceramic and then lowering the ambient temperature to the melting point of gallium. As the gallium solidifies, it effectively occupies the empty spaces created by the defects, reducing the formation and extension depth of cracks during the polishing process. Furthermore, this paper demonstrates the accuracy of the proposed idea through finite element simulation analysis of crack generation in glass-ceramics at different cutting depths and single grit grinding test of glass-ceramic. The results confirm that the liquid gallium metal infiltration additive treatment improves the machining performance of glass-ceramic and reduces the width and depth of scratches during the cutting process, providing an innovative and easy method for ultra-precision machining of highly brittle materials.

The planetary roller screw mechanism (PRSM) is a high-precision actuator, widely used in aerospace, humanoid robots, and automotive systems. However, inherent structural and loading characteristics lead to uneven load distribution among thread teeth, causing contact stress concentration and accelerated wear, which limit transmission performance. Thread profile modification has emerged as an effective solution to optimize load distribution and reduce stress concentration. This study reviews the origin, classification, load-bearing characteristics, and kinematics of PRSM. It discusses local modification methods (half-thread thickness, pitch diameter, crest, and root) and global strategies (concave-convex arc reconstruction, multi-parameter optimization, etc.), highlighting their mechanisms, advantages, and limitations. Discrete modification can reduce average contact stress by approximately 35.55% and improve load uniformity. Additionally, the study addresses measurement techniques, potential negative effects of modification, and proposes a macro-meso-micro modification framework. Finally, current challenges and future research directions are summarized, providing a theoretical foundation for PRSM engineering applications.

Backdrivability is a key characteristic of robotic reducers; however, a long-standing lack of theoretical research has constrained its engineering application. Hysteresis, as an inherent characteristic of reducers, can effectively reflect the dynamic behavior during rotational motion. This paper systematically studies the backdrivability of reducers based on hysteresis characteristics. Combining the practical needs of robotic applications, the definition of back drive is clarified, emphasizing that its core lies in the rotation angle and energy absorption capacity. By establishing a correlation model between hysteresis characteristics and backdrivability, generalized polynomial and analytical expressions are proposed: lost motion is introduced as a key indicator, utilizing numerical changes in the hysteresis curve to evaluate the rotation angle; the area enclosed by the hysteresis curve is used to characterize the energy absorption capacity of the reducer during back drive, and statistical analysis methods along with torque-energy curves are employed to evaluate overall and instantaneous energy consumption performance, respectively. Experiments compared the backdrivability of two reducers made of different materials. The results indicate that geometric errors, elastic deformation, and material properties all significantly influence back-driving behavior.

Position-independent geometric errors (PIGEs) of rotary axes are critical factors limiting the machining accuracy of five-axis machine tools. Aiming at the accurate identification of rotary-axis PIGEs for dual rotary table five-axis machine tools, this study proposes an improved double ball bar (BB) measurement scheme. This scheme features excellent decoupling performance, convenient operation and high efficiency: complete error decoupling is realized via independent single-axis rotary measurement; a standard fixed-length ball bar is adopted without any auxiliary fixtures to effectively reduce setup-induced errors; a non-iterative analytical algorithm based on circular eccentricity fitting is developed to accurately identify all geometric errors of rotary axes. Based on homogeneous coordinate transformation theory and the fundamental BB measurement principle, mathematical models that correlate rotary-axis PIGEs with BB length deviations are established for four designed measurement modes. By constraining only one single rotary axis to move while fully locking all other axes during each test, the proposed method enables BB measurement data to exclusively reflect the geometric errors of the tested rotary axis, thereby fundamentally eliminating geometric error coupling induced by multiple axes. Subsequently, the correlation between PIGEs and BB length variations is quantitatively analyzed via numerical simulation. On this basis, an analytical PIGE identification strategy is developed using circular eccentricity fitting of measured BB trajectory data. Taking a typical BC-type dual rotary table five-axis machine tool as the experimental platform, all eight rotary-axis PIGEs are successfully identified and compensated. Experimental results demonstrate that the maximum positional error is reduced from 144.53 μm to 7.72 μm, achieving an overall accuracy improvement rate of 79.48%. The proposed method enables high-precision PIGE decoupling and identification, effectively improves the machining precision of five-axis machine tools, and exhibits good applicability for dual rotary table machine tools, providing a reliable alternative for geometric error identification in five-axis machining systems.

This paper investigates the loading-rate dependence of hysteresis in miniature reducers. A hysteresis model considering loading-rate dependence is established and validated. By decomposing hysteresis curves, the influence of loading-rate dependence on hysteretic behavior is quantified. The dynamic nature of lost motion is re-examined, and loading-rate dependence is identified as a key dynamic characteristic that biases hysteresis tests. Two novel testing strategies-equal-position gradient loading and constant-speed loading-are proposed to mitigate rate effects while meeting the constraints of miniature reducers. These methods improve measurement accuracy and repeatability. Finally, the practical application of rate dependence in optimizing reducer design, testing, and evaluation is discussed.

Reducers used in robotic joints often provide only a limited range of transmission ratios, while remaining bulky and imposing relatively high sliding velocities on the meshing tooth pairs. This work presents the mechanism design and dynamic analysis of a novel Double Differential Reducer intended for compact high-ratio transmission. The reducer employs a special internal planetary arrangement that substantially reduces the input speed, and the desired transmission ratio can be obtained by finely adjusting the tooth numbers. A symmetric transmission layout further enhances power density while preserving a compact overall envelope. To investigate the dynamic behaviour of the transmission system, a nonlinear dynamic model is developed that incorporates backlash, time-varying mesh stiffness, meshing damping and static transmission error. The resulting equations of motion are numerically integrated using a classical fourth-order Runge-Kutta scheme, and the dynamic response under different rotational speed excitations is examined to clarify the global vibration characteristics of the reducer. A dedicated test bench is constructed and prototype tests are carried out to validate the model. The comparison between numerical and experimental results shows that the proposed dynamic model predicts the vibration characteristics of the Double Differential Reducer with good accuracy and provides a useful basis for the design of stable and reliable operation. The results also indicate that the transmission system exhibits stable periodic vibration under high-speed excitation, which supports the use of the proposed reducer in high-speed transmission applications.

Contact measurement plays a pivotal role in manufacturing and application of micro-gears. Nevertheless, conventional contact measurement techniques may result in data gaps at the tooth roots and induce measurement errors stemming from microscopic interactions. In this paper, the mechanism of the effects of the WC probe on the dynamic measurement of Fe-based micro-gears was investigated. The three-dimensional (3D) morphological changes were analyzed by using LAMMPS simulation software. Wear count and displacement, friction change rule, and mechanism of the Fe-based micro-gear surface during dynamic measurement under different loads and measurement speeds were studied. The local dislocation during the dynamic measurement was predicted. The results show that the height of the worn atom accumulation and the count of worn atoms on both edges of the wear scar decrease with the increase in the measurement speed under the same load. However, the height of the atom accumulation ahead of the probe increases, resulting in increased friction and the decrease in the count of worn atoms ahead of the probe. At a fixed measurement speed, both the overall stacking height of worn atoms and their total count increase with increasing load, thereby increasing the coefficient of friction.

With the increasing performance demands on gears for new energy vehicles, it has become essential to extract and decouple the gear error information contained in transmission error (TE) and radial composite deviation (RCD). However, a quantitative relationship between TE and RCD has not yet been clearly established. To address this issue, a numerical model of double-flank meshing is developed to reveal their intrinsic relationship. Based on this model, the effects of crowning and pressure-angle deviation on the relationship between TE and RCD are further analyzed.

The 3D scanning probe is the “eye” of precision measuring instruments, coupling errors among its axes remain an urgent problem; accurate decoupling is essential for improving probe data accuracy. This paper presents an improved algorithm that integrates Particle Swarm Optimization (PSO)、Latin Hypercube Sampling (LHS), and an Opposition-Based Learning (OBL) strategy. The inertia weight w is dynamically adjusted using a cycloidal schedule, ensuring both rapid initial convergence and refined exploration in later stages. Additionally, the cognitive and social coefficients c 1 and c 2 are linearly decreased to minimize the risk of the swarm becoming trapped in local optima. Compared with the standard PSO algorithm, the improved algorithm can obtain the global optimal solution, while the standard algorithm only achieves the local optimal solution and thus cannot be applied to probe decoupling. Compared with the LSM algorithm, the coupling matrices obtained by the two methods are basically consistent under the condition of outlier-free data. Nevertheless, when outliers exist in the dataset, the LO-PSO algorithm achieves superior robustness and decoupling accuracy relative to LSM. Tests were conducted on the original dataset, and the results show that decoupling improves the measurement accuracy of test data in the X, Y and Z directions. Compared with the pre-decoupling results, the four X-group datasets showed a maximum type-I error of 0.747%, corresponding to an average gain of 8.02%; the Y-group datasets showed a maximum type-I error of −0.956%, corresponding to an average gain of 10.82%; and the Z-group datasets showed a maximum type-I error of 1.658%, corresponding to an average gain of 8.86%. The results show that the improved algorithm significantly enhances the data accuracy of the 3D scanning probe. Under laboratory calibration test conditions, the LO-PSO algorithm achieves superior decoupling accuracy and outlier resistance robustness compared with the least squares method, and it has the engineering potential to be integrated into precision measurement software for on-site decoupling.

In the domain of large-scale precision measurement, laser tracer multistation measurement systems are extensively utilized due to their superior accuracy and efficiency. Within multistation measurement, system layout is a pivotal factor influencing measurement accuracy, making its optimal design essential for enhancing the performance of multistation technologies. This research introduces a multistation layout optimization method based on a genetic algorithm combined with sequence quadratic programming. This approach formulates an objective function centered on the positional accuracy attenuation factor and develops a hybrid optimization model by integrating genetic algorithms with sequence quadratic programming. The model incorporates constraints such as the maximum measurement length and angle of the tracer as well as the measurement space range. Initially, it identifies the potential area through a global scope analysis, followed by utilizing the sequence quadratic programming method to ascertain the precise optimal station configuration within the designated area. Multistation measurement and comparative validation experiments were conducted by designing measurement points within a (200 × 200 × 150 mm3) workspace, employing a coordinate measuring machine as the experimental subject. The results indicate that the optimization reduced three-axis positioning errors by 60.8%, 38.1%, and 25.7%, respectively. The present findings confirm the effectiveness of the proposed method and highlight its extensive engineering application potential.

This study investigates the impact of graphene oxide (GO) particles concentration on gear churn lubrication patterns and tooth surface self-healing properties through a combination of computational fluid dynamics (CFD) simulation and experimental exploration. A novel nanofluid lubrication experiment setup is established. To accurately simulate the motion characteristics of rotating fluid and GO particles, the sliding grid method and VOF-DPM multiphase flow model are employed. The distribution states of lubrication oil are analyzed at various gear rotational speeds ranging from 600 to 1800 r/min. Particle trajectories align with experimental observations, including adherent, ejection, and splash flow. The interaction between nanoparticles and gears involves complex dynamics influenced by fluid adhesion, centrifugal force, and the interplay with the gear surfaces.