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Abstract McKibben pneumatic actuators (MPAs) are soft actuators that exert tension by applying compressed air to expand a rubber tube. Although electro-pneumatic regulators can control air pressure, most are large and expensive. This study utilizes a dynamic quantizer to control the MPA with a small solenoid valve that can only open and close the valve instead of an electro-pneumatic regulator. A dynamic quantizer is one of the quantizers that converts continuous signals to discrete signals. Our previous study confirmed that tension control of MPA under isometric conditions could be realized using a dynamic quantizer. However, it is often necessary to control the length of the MPA as well as the tension of the MPA. This study implements a dynamic quantizer to control the length of the MPA with a small solenoid valve. Numerical simulations and experimental tests verify the effectiveness of the proposed method. The results of the numerical simulations and experimental tests confirmed that the length of the MPA can be controlled using the dynamic quantizer.

The problem of estimating the gripping force of surgical instruments has been the focus of research on minimally invasive surgical robotic surgical instruments. During the minimally invasive surgery, excessive gripping force can cause tissue damage, and too small gripping force can make suture needles fall off and cause danger. Therefore, it is necessary to study how to estimate the gripping force of surgical instruments. According to the structural characteristics of surgical instruments, a method for estimating gripping force based on dynamic model is proposed. The dynamic model of the surgical instrument, the force and displacement transmission characteristics of the cable driven system and the direct-current motor characteristics are considered in the established model, and the relation between the surgical instrument motor current and the gripping force is obtained. The gripping force model is validated by using Matlab simulation, and the gripping force variation curve of the surgical instrument end-effector with the change of the motor current are obtained. The simulation results show that the gripping force estimation model of the surgical instrument based on the dynamic model is consistent with the actual situation, which provides a theoretical basis for the subsequent research on the gripping force security of the surgical instrument.

In order to deeply study the influence of parallel misalignment failure on fatigue life of pin couplings with elastic sleeves, on the basis of transient dynamic analysis, the influence of different degrees of parallel misalignment on fatigue life is obtained. Based on transient dynamic fatigue analysis data, combined with the differential autoregressive integrated moving average (ARIMA) model, the fatigue life prediction of pin couplings with elastic sleeves is realized. The results show that the minimum fatigue life of pin couplings with elastic sleeves decreases with the increase of the degree of parallel misalignment, and when the degree of parallel misalignment is less than 2.63%, the decrease of minimum fatigue life increases gradually. The predicted fatigue life of 4.74% parallel misalignment is 1.214 0×106, and the relative error between the predicted value and the simulation value is 0.22%, indicating the reliability of the ARIMA model in predicting fatigue life. The research results can provide guidance for the anti-fatigue optimization design of pin couplings with elastic sleeves.

Torsional vibration of the automobile transmission system may cause roar or abnormal noise in the car. Torsional vibration excitation generally comes from the main order of the engine and is transmitted to the gearbox through torsional vibration damper. Therefore, the torsional amplitude of the gearbox input shaft is the first factor to control the torsional vibration of the whole transmission system. A passenger car is equipped with a 6-speed wet double clutch transmission (WDCT). The maximum torsional amplitude of the input shaft of the gearbox from 2nd gear to 6th gear has reached 494.38 rad/s2, which does not meet the design requirement of 400 rad/s2. In order to solve the problem that the torsional amplitude of the gearbox input shaft is too large, this study uses AMESim software to build a torsional vibration analysis model with dual mass flywheel torsional vibration damper under full throttle driving condition, taking the engine speed fluctuation signal collected by a real vehicle as the excitation source. Through simulation analysis, the influences of the primary mass moment of inertia, secondary mass moment of inertia, torsional stiffness, basic damping torque and free rotation angle of the dual mass flywheel on the torsional amplitude of the gearbox input shaft are determined, and the optimization scheme of the transmission system is obtained through orthogonal experimental design, and the effectiveness of the optimization scheme is verified by a real vehicle. The research methods and ideas of this study provide a solution for the torsional vibration optimization of the automobile transmission system with dual mass flywheel torsional vibration damper.

A 3-RPS parallel leveling mechanism based on the proportional integral (PI) robust sliding mode system is designed to solve the problem of data acquisition inaccuracy caused by vehicle tilting during the robot walking. Firstly, the configuration synthesis is carried out according to the spiral and inverse spiral theory. Then, the dynamic analysis and calculation of the 3-RPS leveling mechanism are carried out to construct its dynamic model. On this basis, the adaptive robust sliding mode algorithm is introduced to optimize and improve the PI controller to improve the stability and adaptive correction ability. The stability of the nonlinear control system is verified by Lyapunov function. Finally, the control error curve is obtained by Matlab/Simulink comparative simulation experiment. The simulation results show that the adaptive correction effect of the PI control system optimized by the robust sliding mode algorithm is remarkable, and the steady-state error of the control is greatly reduced. The research provides a basis for the development of physical prototype of 3-RPS parallel leveling mechanism.

Aiming at the demand of electric cinch and release priority function of high-end vehicle door latches, a cam swing linkage and spring linkage combined mechanism is proposed, and a combined mechanism of double cam single swing linkage and spring four bar mechanism is constructed. Combined with the characteristics of limiting blocks, contact states, cam intermittent movement, profile abrupt change and other components, it can realize three motion modes of flexible and adaptive rolling, rigid pushing, avoiding and releasing, and switch among them. Embedded into the ratchet and pawl locking mechanism, the combined mechanism is transformed into electric cinch and release branches, corresponding to the three working conditions of the vehicle door latch: electric cinch, manual or power release and reset, and cinch branch reset. Based on the corresponding driving modes and motion boundary conditions, the compatible function of the cinch motion and the existing branches in the latch, the release priority function, and the half-lock release function in the case of the cinch pinch are studied and analyzed. The mechanism and the drive are embedded in the door latch for simulation, and the contact force between the release cam and the swing linkage, the swing linkage and the ratchet, and the ratchet and the paw are studied in all working conditions. The time of the mechanism to realize each function matches the design requirements of the vehicle door latch, the time of the electric cinch process is 420.97 ms, the reset time is 29.03 ms, and the manual release time is 622 ms.

A 3-DOF parallel manipulator with X, Y movement and Z rotation for the end-effector is studied in order to meet the requirements of copying and polishing of louver blades. In order to verify the kinematic performance of the manipulator, firstly, the mechanism characteristics are described, and the degree of freedom of the mechanism is analyzed based on the spiral theory. Secondly, the kinematics equations of the mechanism are constructed based on the closed-loop vector method, the forward and inverse position solutions are analyzed, and the analysis results are preliminarily verified by concrete examples. Finally, the numerical simulation model and virtual prototype model of the mechanism are constructed, and the inverse kinematics simulation analysis of the position and velocity is carried out. The simulation results show that the analysis results of the two models are consistent, and the result of inverse solution is reliable. The arm chain can coordinate the movement, the movement process is smooth, and the displacement and velocity curves are smooth and without mutation, and can provide a basis for the size optimization and motion control of the manipulator.

When a gearbox transmission system fails, the multi-scale mean permutation entropy （MMPE） of different vibration signals corresponds to the fault state to a certain extent. However, the effect of multi-scale mean permutation entropy extraction fault features depends on the selection of parameters. Therefore, this study proposes a gearbox fault identification method based on the improved multi-scale mean permutation entropy and the parameter optimization support vector machine（SVM）. Firstly, the particle swarm optimization （PSO） is referenced to optimize parameters of multi-scale mean permutation entropy. Secondly, the multi-scale mean permutation entropy of the collected gear vibration signals is calculated.Finally, the particle swarm optimization is used to optimize the support vector machine to identify the fault state of the gear. Experimental analysis results are conducted to validate the effectiveness of this proposed method.

Gear skiving has been paid more and more attention for high efficiency and wide application in gear manufacturing. In gear skiving, prediction of cutting temperature and optimization of process parameters have an important influence on increasing tool life, improving machining quality and decreasing residual stress. In this study, firstly, according to the kinematic theory of gear skiving, the entity models of the skiving tool and the workpiece are established, and then the cutting temperature nephograms on the rake face of single tooth during the cutting process are obtained based on Deform software. Secondly, aiming at the influences of the cutting velocity, feed rate and shaft angle on the maximum cutting temperature on the rake face, the prediction model of the cutting temperature under multiple parameters is established by response surface methodology. Finally, a method of process parameter optimization is proposed to maximize the machining efficiency with the constraint of cutting temperature. Combined with three groups of optimization examples, the validity of the cutting temperature prediction model is verified by comparing the error between the predicted values and simulation results under the optimized parameters. The results show that the shaft angle has the greatest effect on the cutting temperature under single parameter, the cutting velocity-shaft angle has the greatest effect on the cutting temperature under multiple parameters, and the optimized predicted values are within a reasonable error range from the simulation results. The results of this study provide methodological support for improving the machining quality and tool life in gear skiving.

Aiming at the balance between the accuracy, stability and exoskeleton volume of the existing upper limb exoskeleton, an 8-degree-of-freedom （DOF） hybrid upper limb rehabilitation exoskeleton robot is proposed. A new 2-degree-of-freedom elbow rehabilitation device is designed to replace the traditional single-degree-of-freedom elbow exoskeleton in order to better achieve elbow training for patients with upper limb movement disorders. A 3RRR/S mechanism with coaxial spherical surface is designed for hand rehabilitation, which can make the rehabilitation training of hand more enveloping. The coordinate system is established according to the hybrid exoskeleton mechanism, the kinematic model of the rigid body part of the mechanism is established by using the vector loop method, and the working space nephogram of the mechanism is drawn by Monte Carlo method to verify that it meets the space requirements for rehabilitation training. Finally, the trajectory planning of a typical motion is carried out by Matlab, and the smooth trajectory of the terminal centroid motion is obtained by Adams to verify the rationality of its kinematic analysis and structural design. The maximum load attitude is simulated by constrains the excess degrees of freedom, and the load characteristic curve is drawn, which lays the foundation for the selection of the drive and the construction of the prototype.

A wearable walking aid for lower limbs is designed, which is mainly used to assist patients with lower limb movement disorders such as stroke hemiplegia to carry out daily walking activities. First of all, based on the analysis of the lower limb motion mechanism, joint structure and the composition of degrees of freedom, the three-dimensional structure model of the lower limb wearable walker is established. The 3D infrared motion capture system is used to collect the gait data of normal people and fit the corresponding joint angle curve. The simplified D-H model of the walker is established, and the kinematics modeling analysis of the walker is carried out. Taking the gait data collected from the motion capture experiment as the simulation driving force, the kinematics simulation verification of the walker is carried out. The results show that the joint angle change curve is basically consistent with the angle curve collected from the experiment, and the angular velocity change curve and the ankle joint centroid position change curve are consistent with the normal human walking law, which verify the rationality of the structure design of the lower limb wearable walker.

Three kinds of circular spline materials are studied for harmonic reducers, stainless steel 2Cr13, medium carbon alloy steel 40Cr, carbon 45 steel. Through the analysis of microstructure, hardness, three-dimensional and two-dimensional morphology in microwear and friction coefficient, the differences in wear resistance of different materials are attained. The results show that the microstructures of 2Cr13 and 40Cr are tempered sorbite, and the microstructure of 45 steel is ferrite and pearlite. The hardness of the 2Cr13 and 40Cr is similar and much larger than that of the 45 steel. The morphology of 2Cr13 is adhesion and spalling, and the wear mechanism is adhesion wear. The morphology of 40Cr and 45 steel is furrow and spalling, furrow and adhesion, and the wear mechanisms are abrasive wear. The friction coefficients' differences of the three materials are negligible, and the area of wear of 2Cr13, 40Cr and 45 steel are 5 008 μm2, 1 645 μm2 and 6 535 μm2. 40Cr exhibits better wear resistance than 2Cr13 with similar hardness. The hardness difference between 45 steel and the friction pair material is the largest, and the wear resistance of the 45 steel is the worst.

Gear surface damage is an important factor affecting gear transmission. It is extremely important to improve the efficiency and accuracy of gear surface damage identification. ResNet recognition model of gear surface damage is established based on Pytorch architecture, dataset is expanded by means of data enhancement, model training is optimized by means of transfer learning, and four ResNet structures are compared. The results show that the dataset composed of 640 images after the enhancement of 64 original image is not enough to meet the needs of model training for a large amount of data; using transfer learning can improve the speed and accuracy of model training, and meet the requirements of gear surface damage identification; the ResNet-101 model is the optimal structure in this framework. This research has important scientific significance and engineering value for the recognition of gear surface damage.

Aiming at the problem of subjectivity and uncertainty in the configuration and selection of spherical robot design schemes in multi-demand unstructured environments, a scheme evaluation method coupled with fuzzy rough number and complex proportional assessment (COPRAS） is proposed. Considering the importance relation between different demand characteristic indexes in scheme design, the quantitative analysis of demand characteristic indexes is realized based on the fuzzy rough number. The COPRAS method is used to comprehensively evaluate all alternative design schemes, the priority ranking of all alternative design schemes is obtained according to the utility index to determine the optimal configuration scheme， and the selection of deformed spherical robots is taken as an example for evaluation and verification. The research results show that the method has good reliability and practicability, which provides effective reference for the configuration and selection of the robot design scheme in the future.

In the rehabilitation training process of lower limb rehabilitation robots, the existence of uncertain factors such as model parameters and environmental interference will affect the accuracy of trajectory tracking of the robot. To solve this problem, an adaptive compensation control based on the radial basis function (RBF) neural network is proposed. This control method can improve the accuracy of mechanical system trajectory tracking. Firstly, a closed chain horizontal lower limb rehabilitation robot structure with four working modes and stable movement is designed. Secondly, the Lagrange method is used to solve the kinetic nominal model, the uncertainty factors such as model parameters and external interference of the rehabilitation device are separated, and the adaptive compensation algorithm based on the RBF neural network is designed for the approximate control. Finally, the Matlab/Simulink environment is used to verify the effectiveness of the control strategy. The results show that, compared with the traditional fuzzy proportional integral derivative (PID) control method, the adaptive compensation algorithm based on the RBF neural network has a faster response speed and better tracking effect in human gait curve trajectory tracking. Moreover, the peak angle errors of the hip joint and the knee joint trajectory tracking are 0.08° and 0.13° respectively, which are much less than the rotation angle of patients' lower limbs in rehabilitation exercise. A single-leg prototype experiment is designed to show that the RBF compensation adaptive controller used in the study can achieve high precision tracking results and meet the safety requirements of patients in rehabilitation training.

In order to correctly understand the output characteristics of gear-motors with different types of backlash sizes/offset unloading slots, a unified simplified formula for output characteristics such as speed/torque is constructed based on the different meshing line intervals of meshing tooth profiles/output characteristics, using the type value that measures the backlash size and the offset value between the symmetrical line of the double unloading slots and the centerline of the gear pair as variables. The results show that through the interval of the output characteristic meshing-line, the output speed and torque curve can be directly obtained from the speed and torque curve of meshing tooth-profile; under the symmetrical relief-groove type, the average output speed is the smallest, the average torque is the biggest, and the ripple coefficients of the output speed and torque are the smallest; the offset range of the relief-groove and the range of the output speed and torque regulating are larger under small backlash type than large backlash type; with small backlash and symmetrical relief-groove type, the average output speed is smaller, the average output torque is larger, and the ripple coefficient of the output speed and torque is smaller; the torque-ripple coefficient of the gear-motor is completely consistent with the flow-ripple coefficient of the gear-pump; the torque-ripple coefficient is slightly less than the speed-ripple coefficient, and can be approximately equal under the condition of large tooth-number; when high-speed is pursued, the type combination of large backlash and relief groove limit-offset shall be selected; with the pursuit of large torque or high output ripple-quality, the type combination of small backlash and symmetrical relief-groove shall be selected, etc. It is concluded that the obtaining method of output characteristics is simpler, the principle is clearer, the form is more concise, and the results are more reliable.

Based on the thread tooth load distribution of the inverted planetary roller screw mechanism（IPRSM）, the influence of roller modification and screw modification on the load distribution is analyzed. The results show that the uneven load on the screw-roller interface is more serious than that on the long nut-roller interface, and the maximum contact stress and the maximum load on the threaded teeth are effectively reduced by the roller modification. Besides, the long nut-roller interface is more sensitive to the modification amount than that of the screw-roller interface. Similarly, the maximum load can also be effectively reduced by the screw modification. This study has some reference significance for optimizing the load distribution of the IPRSM.

Based on the analysis of the overall structure of the existing hub motor used for electric bicycles, aiming at the problems of instability and large noise when the inner rotor of the hub motor adopts the left and right half shaft structure, a hub motor structure of the through shaft inner rotor and reduction device is improved and designed. Based on the optimization design theory, the minimum total volume of the reduction device is taken as the objective function to optimize. Creo software is used to draw the optimized 3D model of the reducer, and finite element analysis is carried out by Ansys Workbench software to check the strength and stiffness of the structure. The results show that the new design overcomes the defects of the left and right half shaft in the electric bicycle hub motor, the volume of the reducer is reduced by 8.6% after optimization, and the structural design strength and stiffness meet the requirements, which verifies the rationality of the structure, and provides a new idea and theoretical basis for the electric bicycle hub motor structure design and optimization.

The stiffness and damping characteristics of the diaphragm coupling are the basis for analyzing the vibration characteristics of the shafting system with the diaphragm coupling. Based on Ansys finite element simulation software, considering contact nonlinearity and large deformation effects, this study simulates and analyzes the torsional, axial, angular and radial static stiffness characteristics and torsional and axial dynamic characteristics of the diaphragm coupling, and analyzes the influence of the diaphragm structure parameters such as the diameter of the bolt hole distribution circle, the diameter of the bolt hole, the minimum width of the diaphragm and the thickness of the diaphragm on the static stiffness. Finally, static, dynamic torsion and axial tension tests are carried out to verify the correctness of the simulation results. The results show that the diameter of the bolt hole distribution circle and the thickness of the diaphragm have a greater influence on the anisotropic stiffness of the diaphragm. The dynamic model of the diaphragm coupling can be better established through the quasi elliptic function. The nonlinear stiffness and the equivalent damping coefficient changes in a period of the diaphragm vibration can be obtained.

Aiming at the problem that it is difficult to explore the contact state law of racks and pinions under the condition of rack-rail train wheel tread wear, a calculation model of rack and pinion tooth surface contact stress considering wheel tread wear is proposed based on the Hertz contact theory. Firstly, the contact relationship of racks and pinions under wheel tread wear is analyzed, the change law of key parameters of contact stress calculation with wheel wear is obtained, and the contact stress calculation model of racks and pinions considering wheel wear is constructed in combination with the Hertz contact theory. Then, the rack and pinion parameters of an engineering are selected for calculation, the tooth surface contact stress distribution in the wear cycle is obtained, and the contact stress data of the pinions and racks and of different wear quantities and different contact positions are obtained through 27 sets of finite element simulation tests, which are compared with the above calculation model results. Finally, the above calculation model is used to further analyze the internal mechanism and key factors of wheel wear affecting the contact stress law. The results show that the maximum relative error between the model results and the simulation calculation results is 7.71%, which verifies the accuracy of the calculation model. The greater the wear of the wheel tread is, the greater the contact stress near the meshing entry point of the rack and pinion will be; and the influence mechanism is that the radius of curvature of the drive gear near the meshing entry point is sharply reduced by wheel wear. Increasing the initial center distance and the rack tooth top fillet influence coefficient can reduce the influence of the wheel tread wear. The height adjustment period can also be appropriately reduced to optimize the contact state situation.

A study on the load characteristics of the modified gear planetary gear systems is conducted to address the issue of uneven loads between planetary gears due to manufacturing and installation errors, which result in deviations between the radial and circumferential installation positions of planetary gears and non-offset values. Based on the theory of rotor dynamics, the time-varying stiffness and the radial and circumferential offsets of the planetary gears are considered, and the five-degree-of-freedom dynamic model of the planetary gear transmission system with addendum modification is established. The response and frequency spectrum of the system are solved by the Runge-Kutta method. The load distribution characteristics of the planet gears under different radial offsets, circumferential offsets, and comprehensive offsets are analyzed. The influence of the radial and circumferential offset of the planetary gear on the load distribution of the planetary gear transmission system is discussed, and the variation law of the load vibration amplitude of the planetary gear transmission system with addendum modification under the time and frequency is obtained. The simulation results show that the load characteristics of the planetary gear train considering the error are quite different from those in theory. Its vibration amplitude of the planetary gear transmission system is greatly affected by the radial offset, and the large radial offset has the greatest impact on the load of the planetary gear. Small deflections of the planetary gear during installation can lead to large changes in the load characteristics. The planetary gear transmission system load test platform is built, the frequency-doubling vibration response signal of the planetary reducer housing is tested, and the relation between the planetary gear transmission system load force and vibration response is obtained. The amplitude variation trend in the experimental results is similar to that in the simulation analysis, and the correctness of the established model and solution method is verified.

Based on the 3-UU parallel mechanism, a prototype robot for wrist joint rehabilitation is developed to assist stroke patients in wrist joint rehabilitation training. Based on the constraint relation and geometric characteristics of the 3-UU mechanism, the inverse kinematics of 3-UU mechanism is analyzed by spherical coordinate method and roll-pitch-yaw (RPY) method， and the relation between the platform and the driver is obtained. Compared with the classic 3-RRR wrist joint rehabilitation mechanism, the developed prototype has no advantages such as multi-solution and singular value. The motion performance of the prototype and the electromyographic signals of the two major muscle groups in the forearm are measured. The experimental results show that the maximum roll angle is -90° to 90°, the pitch angle is -90° to 90°， and the virtual yaw angle is -180° to 180°. The maximum electromyogram (EMG) signal can be generated at 950 mV. The results show that the developed model can meet the requirements of the wrist motion and train the forearm muscle group.

With the development of the gear transmission system towards complexity, multiple transmission types and high reliability, it becomes more and more important to assign the reliability of the gear transmission system quickly and accurately. In this study, aiming at the problems of incomplete consideration factors, inconsistent range of changes in different allocation methods for the same parameter, and inconvenient digital software development in existing reliability allocation methods, an improved advisory group on reliability of electronic equipment (AGREE) allocation method is proposed, the scoring allocation method is extended, and the digital characteristics of reliability allocation method are discussed. The basic reliability model and task reliability model of the complex gear transmission system are established, and the traversal algorithm of the automatic reliability model generation is studied. A digital platform for rapid reliability allocation of fixed axle gear train, planetary gear train and hybrid gear train is developed. Four independent modules, namely input module, calculation module, result display module and output module, are designed. The accuracy of the calculation results of the software is verified by comparing with the results of examples. The parametric modeling and the automatic generation of the example report for the reliability allocation of the gear transmission system are realized, and the accuracy and efficiency of the reliability allocation model are raised.

In order to better meet the work requirements of the marking production line to remove the unqualified workpieces, this study designs a double cam clamping mechanism which can realize the clamping and lifting of the workpieces with only one power source. The motion sequence of two cams is designed based on the action sequence of clamping and removing the unqualified workpieces. The contour curve of the cams is calculated by Matlab software, and the 3D model is built on SolidWorks platform. Adams software is used to complete the parametric modeling and motion simulation of the double-cam clamping mechanism. The results show that the output motion law of the mechanism is consistent with the designed motion law. Through the optimization design of the key coordinate position, the appropriate position parameters of the key coordinate are obtained. The double-cam clamping mechanism can effectively save cost and improve work efficiency, and has certain theoretical value and high application value for practical production line.

Abstract The accurate estimation of parameters is the premise for establishing a high-fidelity simulation model of a valve-controlled cylinder system. Bench test data are easily obtained, but it is challenging to emulate actual loads in the research on parameter estimation of valve-controlled cylinder system. Despite the actual load information contained in the operating data of the control valve, its acquisition remains challenging. This paper proposes a method that fuses bench test and operating data for parameter estimation to address the aforementioned problems. The proposed method is based on Bayesian theory, and its core is a pool fusion of prior information from bench test and operating data. Firstly, a system model is established, and the parameters in the model are analysed. Secondly, the bench and operating data of the system are collected. Then, the model parameters and weight coefficients are estimated using the data fusion method. Finally, the estimated effects of the data fusion method, Bayesian method, and particle swarm optimisation (PSO) algorithm on system model parameters are compared. The research shows that the weight coefficient represents the contribution of different prior information to the parameter estimation result. The effect of parameter estimation based on the data fusion method is better than that of the Bayesian method and the PSO algorithm. Increasing load complexity leads to a decrease in model accuracy, highlighting the crucial role of the data fusion method in parameter estimation studies.

The vertical drop is one of the most widely used hydraulic structures for dissipating the destructive energy of water. The purpose of this research is to investigate the effect of the two difference height, and five vertex angles of a triangular plan form vertical drop on energy dissipation and average velocity using the volume of fluid (VOF) method. The findings revealed that by decreasing vertex angle of the triangular plan form vertical drop, energy dissipation increases. The lowest relative depth of the pool occurs with this drop. In contrast, as the vertex angle of the triangular plan form vertical drop decreases, the average velocity at the foot of the drop increases and the maximum average velocity in the triangular plan form vertical drop with an angle of 60 degrees and a height of 0.2 m is higher than other models. The average downstream velocity also decreases by decreasing the angle and this decrease is more intense in the center of the channel than on the sides.

In order to determine the most suitable turbulence model for studying the aerodynamic performance of bus, the effects of different turbulence models on the aerodynamic characteristics of bus were investigated. A comparative analysis was conducted on five turbulence models (IDDES, DDES, DES, LES, URANS). The pressure distribution on the cross section at x=0 and y=0 is also analyzed for each model. The results reveal that IDDES accurately captures the negative pressure at the rear of the bus and predicts the pressure gradients more effectively than other models. IDDES also captures more vortices at the head of the bus and predicts the wake flow more widely than other models. DDES has obvious shedding phenomenon in the wake flow, while IDDES provides a relatively smooth airflow trajectory, but its prediction of airflow trajectory at a distance is less clear. Through quantitative and qualitative analyses of the aerodynamic characteristics of bus under different turbulence models, it can be concluded that IDDES is the most suitable turbulence model to study the aerodynamic characteristics of bus.

Stall, a complex flow phenomenon in centrifugal pump, plays a crucial role in pump safety and stability under part-load conditions. In this paper, a verified numerical simulation method is employed to analyze the three-dimensional flow field under the stall inception conditions. The results reveal the initial stall vortex occurs near the Q=0.7Qd condition in the prototype impeller. Based on stall formation mechanism, the high-velocity fluid near the blade pressure side is sucked into suction side of next impeller channel by setting a groove near the blade leading edge. This jet flow can prevent the narrow vortices near the impeller shroud from moving towards the blade suction side, thereby suppressing the formation of stall vortex. By comparing the effects of different groove locations, directions, and sizes on stall vortex control, the optimal groove width is determined to be approximately 1mm. Compared with the prototype impeller, the grooved impeller can completely eliminate the stall vortex and significantly reduce pressure pulsation under part-load conditions. Moreover, the head of grooved impeller is increased by nearly 15% under Q=0.6Qd condition, and the potential suppression mechanism is also explained. Based on the stall formation mechanism, this paper puts forward an effective stall control method, which delays the stall inception significantly.

Noise is one of the key indicators to evaluate axial flow fans, and in many cases, it is also the only indicator for determining their suitability for use. In this study, a new method to reduce axial fan’s noise was proposed for changing the section chord length to transform the blades of two axial fans with the same design parameters but distinct chord lengths to wavy blades. The aerodynamic calculations and noise reduction mechanism of the wavy configuration of the two fans were studied by combining CFD of large eddy simulation with the Lighthill acoustic analogy method. The results showed that the main mechanism contributing to noise reduction through wavy configuration was the promotion of transformation of the blade surface's layered vortex structure into an uncorrelated comb vortex structure. For fan blades with smaller chord lengths, the comb structure with low spanwise correlation was still maintained after the trailing edge, while for fan blades with larger chord lengths, the comb structure of the shedding vortex rapidly dissipated downstream of the trailing edge. Under the rated design conditions, the implementation of wavy leading edge blades resulted in noise reductions of 1.9 dB and 1.5 dB for the two fans, respectively, while wavy trailing edge blades yielded reductions of 2.6 dB and 2.1 dB, respectively. Furthermore, the adoption of wavy configuration induced a phenomenon of pressure increase and efficiency decrease in both axial fans at medium and low flow rates, with minimal impact at high flow rates. These outcomes underscored the superior noise reduction efficacy of the wavy trailing edge blades, offering a promising way for the noise reduction design of axial flow fans.

The boundary layer's separation loss in compressor cascades constitutes a significant portion of profile loss, critically influencing aerodynamic performance optimization and control. This study employs Large Eddy Simulation (LES) to examine separation losses at varying attack angles, focusing on a rectangular compressor cascade. Specifically, it explores the long separation bubble at a 45% blade height cross-section under designed incidence. Analysis of the separation bubble's transition process revealed a notable surge in total pressure loss rate prior to transition, which stabilized following reattachment. The study thoroughly investigates the evolution of long bubbles, employing quadrant analysis of Reynolds stress, critical point theory, and an in-depth examination of individual vortex dynamics. The findings indicate that the peak of cross-flow within the separation bubble acts as the primary mechanism initiating the transition. This insight is corroborated by DNS calculations of natural transitions on flat plates. Building upon these findings, the study discusses the effects of varying attack angles on transition processes. Notably, increased incidence prompted the upstream migration of the long separation bubble, transforming it into a short bubble at the leading edge. This shift led to a fivefold increase in separation loss and doubled the frequency of transverse flow fluctuations.

The article presents a methodology for determining the hydraulic resistance multiplier, used for a rapid estimation of linear losses in pipes with non-circular cross-sections. The numerical approach was applied using the Finite Volume Method and the ANSYS Fluent software. The research was conducted under turbulent flow conditions, covering two Reynolds number ranges: 10,000 to 100,000 (10 cases) and 100,000 to 1,000,000 (5 cases). The first section of the article presents calculations of losses for a circular pipe, accompanied by a mesh test and error estimation. The second section includes calculations conducted for a series of pipes with various selected cross-sectional shapes: half-circle, quarter-circle, square, rectangles with aspect ratios of 2:1 and 3:1, isosceles triangle, and equilateral triangle. The last section of the article discusses the calculation of linear losses and the hydraulic resistance multiplier for each tested shape. It was found that this coefficient ranged from 1.33 to 2.2, depending on the shape, with the influence of the Reynolds number being relatively insignificant.

In this work, to comprehensively analyze the flow field characteristics of a normal slot plasma synthetic jet actuator, three-dimensional simulation models are established for both normal slot and normal orifice actuators. A detailed comparative analysis of the three-dimensional flow field characteristics of these two actuators is performed. The results indicate that the motion shockwaves and jets generated by the normal slot actuator cover a larger and more uniform region, showing planar characteristics and excellent flow control uniformity. The total pressure ratio for the normal slot actuator is 3.59, significantly higher than the value of 3.50 for the normal orifice actuator, indicating lower pressure loss in the former. Additionally, the normal slot has a larger average exit Mach number (Ma), indicating a stronger flow control capability. It also achieves the peak Ma in a shorter time, indicating a faster momentum output response. Therefore, compared with the normal orifice actuator, the normal slot actuator has better potential for flow control.

Today, due to advances in computing power, Reynolds Averaged Navier-Stokes (RANS) solvers are widely preferred for quasi-three-dimensional (Q3D) blade-to-blade analysis. This study investigates the performance of different flux calculation methods and turbulence models with a density-based RANS solver (Numeca®) in blade-to-blade analysis. A block-structured mesh topology is used to create a solution grid around the airfoil. Spatial discretization is performed in the pitchwise direction to represent the quasi three-dimensional flow, while only one computational cell is used in the radial direction to simulate the flow through the Q3D cascade. The computational grid around the airfoil is created with the Autogrid® tool using the block mesh topology. For the convective flow calculations, both the central and upwind methods available in Numeca® are applied separately. The Baldwin Lomax (BL), Spalart Allmaras (SA), Shear Stress Transport (SST), Explicit Algebraic Reynolds Stress Model (EARSM) and k-ε (KEPS) turbulence models are used for the turbulent shear stress calculations. In order to evaluate the aerodynamic performance of the spatial discretization methods and turbulence models, the isentropic Mach distribution on the airfoil surface, the total pressure loss and the exit flow angle behind the blade are compared with the experimental data of six test cases. In the compressor cases, the Spalart-Allmaras turbulence model with the Central scheme gives the best results in terms of average loss prediction, while no turbulence model is superior to the other in terms of exit angle prediction. On the turbine side, EARSM and KEPS give better performance in terms of loss prediction for the low Reynolds case compared to others, while the Spalart-Allmaras turbulence model is better for the high Reynolds cases.

Accurate predictions of aerodynamic performance and near wake expansion around Horizontal Axis Wind Turbine (HAWT) rotors is pivotal for studying wind turbine wake interactions and optimizing wind farm layouts. This study introduces a novel engineering model centered on stall delay correction to enhance the precision of the Actuator Disk Method (ADM) predictions in both aerodynamic performance and near wake expansion around HAWT rotors. The model is developed based on a comprehensive study of the 3D lift coefficient evolution over the rotor blade, incorporating a shift parameter that considers both stall angle detection and radial decrement. The proposed approach demonstrates remarkable agreements, showcasing discrepancies as low as 7% for both loads and axial wake predictions. These quantifiable results underscore the effectiveness of the model in capturing intricate aerodynamic phenomena. Looking forward, the success of this approach opens avenues for broader applications, guiding future research in wind energy towards improved simulation accuracy and optimized wind farm designs.

The pantograph is a critical instrument that significantly affects the aerodynamics of high-speed trains, posing a considerable challenge to the energy conservation and environmental protection of trains. This study explores the feasibility and efficiency of a jet-flow control technique in optimising the aerodynamic characteristics of the pantograph. A numerical method was adopted to investigate the effects of various jet-flow parameters, such as the jet positions, velocities and jet-slot widths, on the flow changes around the pantograph and subsequent reduction in aerodynamic drag of the pantograph. The results show that the impact of the jet position is negligible when the jet velocity is lower than the train speed. The aerodynamic drag reduction rate decreased with increasing distance from the pantograph as the jet velocity increased. When the distance between the jet slot and pantograph is less than 0.6 times the height of the pantograph, the aerodynamic drag reduction rate continuously increased with the jet velocity. As the jet slot moved away from the pantograph, the aerodynamic drag reduction rate initially increased rapidly with the jet velocity and then gradually decreased when the velocity surpassed 1.2 times the train speed. In addition, the aerodynamic drag of the pantograph decreased as the width of the jet slot decreased. However, the energy of the whole train can be only saved when the jet velocity is below 0.6 times the train speed. Findings in this study verified the effectiveness of the jet-flow method in reducing the aerodynamic drag of pantographs and provide important engineering guidance for the energy-saving of high-speed trains.

This paper presents a comprehensive investigation of flow-induced noise characteristics in ethylene cracking furnace tubes, covering both pre- and post-coking conditions. Large-eddy simulation (LES) was employed in conjunction with a generalized Lighthill’s acoustic analogy model. The results indicate that noise sources can be classified as dipole acoustic sources, with energy primarily concentrated ranged from 300 to 1500 Hz, in comparison to standard conditions. The primary location of the acoustic source was identified in the region commonly referred to as the “necking” of the furnace tube, demonstrating a strong correlation with turbulence intensity near the tube wall. As the coke layer thickness in the furnace tube increased from 5 mm to 15 mm, both the sound power level and turbulence intensity exhibited significant growth. Specifically, the sound power level increased by 60.5% while the turbulence intensity increased by 58.5%. Variations in the overall sound pressure level (OASPL) curve measured within the tube could be utilized to assess coking levels. Significant peaks in the OASPL curve were observed as the furnace tube underwent substantial coking, with coke layer thicknesses of 10 mm and 15 mm. The corresponding OASPL values recorded were 79.25 dB and 119.08 dB, respectively. The findings of this work offer significant insights that may contribute to enhanced safety measures in the operation of ethylene cracking furnace tubes.

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow.

The interior noise caused by the pantograph area is greater than that caused by other areas, and the impact of this pantograph area becomes more significant as the speed of high-speed trains increases, especially above 350 km/h. This study proposes an active jet method for pantograph cavities to control noise at the source. First, a predictive model for the interior noise of pantograph carriages was established by jointly adopting large eddy simulation–statistical energy analysis methods. Then, numerical simulations were conducted to determine the external noise sources and interior sound pressure level at different speeds (300, 350, 400, and 450 km/h). Finally, active jets at different speeds (97.2, 111.1, 125, and 140 m/s) were used to analyze the reduction in interior noise. Results showed that the active jet method decreased the average overall sound pressure level of the acoustic cavity in the horizontal plane. When the train speed reached 450 km/h, the optimal reduction in interior noise was approximately 7.5 dB in the horizontal plane for both the standing and sitting postures. The proposed method can efficiently reduce interior noise in the pantograph area.

This study investigates pressure gradient dynamics within a porous medium in the context of two-phase fluid flow, specifically water and sand particle interactions. Using experimental data, we refine pressure correction coefficients within a numerical solution framework, employing the Semi-Implicit Method for the Pressure-linked Equations algorithm. Our findings highlight the relative nature of pressure gradient phenomena, with particle size and volume fraction emerging as crucial determinants. Graphical representations reveal a clear trend: an increase in volume fraction, up to 40%, across varying Reynolds Numbers, leads to a transition towards non-Newtonian behavior in the two-phase fluid system. Unlike the linear pressure gradient seen in single-phase fluid flow, the interplay between liquid and solid phases, along with drag forces, imparts a distinctly nonlinear trajectory to the pressure gradient in two-phase fluid flow scenarios. As the two-phase flow enters a porous medium, numerous factors come into play, resulting in a pressure drop. These factors include changes in cross-sectional geometry, alterations in boundary layer dynamics, and ensuing momentum fluctuations. Interestingly, an increase in porosity percentage inversely correlates with pressure gradient, resulting in reduced pressure gradient with higher porosity levels.

This study presents an efficient surrogate-based optimization (SBO) method of the aerodynamic performance of a contra-rotating open rotor (CROR). The objective was to maximize propulsion efficiency while reaching the target thrust coefficient at the cruise condition. To reduce the sample size and improve the optimization convergence speed, an infilling criterion was proposed based on the features of the interaction between the CROR front and rear rotors. The efficient front and rear rotors of the initial samples were selected and then combined to form the infilled samples. The results show that the infilled samples were closer to the Pareto front than the initial samples. For the six optimization parameters, 20 initial sample points were used, 11 samples were infilled, and the surrogate-based optimization was completed in five iterations. In total 43 samples were calculated during the optimization. The number of overall samples is approximately seven times the number of optimization parameters. The optimization results in parameter changes compared to the baseline and improved propulsion efficiency while meeting the thrust target. The optimization process increases the torque share of the rear rotor and changes the flow state at different radial positions, leading to a more uniform total pressure distribution at the outlet position, both circumferentially and radially.

Abstract Battery remaining charging time (RCT) prediction can facilitate charging management and alleviate mileage anxiety for electric vehicles (EVs). Also, it is of great significance to improve EV users' experience. However, the RCT for a lithium-ion battery pack in EVs changes with temperature and other battery parameters. This study proposes an electrothermal model-based method to accurately predict battery RCT. Firstly, a characteristic battery cell is adopted to represent the battery pack, thus an equivalent circuit model (ECM) of the characteristic battery cell is established to describe the electrical behaviors of a battery pack. Secondly, an equivalent thermal model (ETM) of the battery pack is developed by considering the influence of ambient temperature, thermal management, and battery connectors in the battery pack to calculate the temperature which is then fed back to the ECM to realize electrothermal coupling. Finally, the RCT prediction method is proposed based on the electrothermal model and validated in the wide temperature range from − 20 ℃ to 45 ℃. The experimental results show that the prediction error of the RCT in the whole temperature range is less than 1.5%.

Abstract The lower limb exoskeletons are used to assist wearers in various scenarios such as medical and industrial settings. Complex modeling errors of the exoskeleton in different application scenarios pose challenges to the robustness and stability of its control algorithm. The Radial Basis Function (RBF) neural network is used widely to compensate for modeling errors. In order to solve the problem that the current RBF neural network controllers cannot guarantee the asymptotic stability, a neural network robust control algorithm based on computed torque method is proposed in this paper, focusing on trajectory tracking. It innovatively incorporates the robust adaptive term while introducing the RBF neural network term, improving the compensation ability for modeling errors. The stability of the algorithm is proved by Lyapunov method, and the effectiveness of the robust adaptive term is verified by the simulation. Experiments wearing the exoskeleton under different walking speeds and scenarios were carried out, and the results show that the absolute value of tracking errors of the hip and knee joints of the exoskeleton are consistently less than 1.5°and 2.5°, respectively. The proposed control algorithm effectively compensates for modeling errors and exhibits high robustness.

Abstract A built-in capacitive proximity sensing method for a charge-induction electrostatic film actuator is proposed. This actuator consists of two thin sheets that function as a stator and a slider. A stator is an insulating sheet with many strips of electrodes in it, whereas a slider is a dielectric sheet that has slight conductivity on its surface. By applying actuation voltage on stator electrodes, the slider that is placed on the stator is driven by electrostatic force. This research realized the simultaneous actuation and proximity sensing using the same electrodes by integrating a resonance-based capacitance measurement circuit into a driving circuit. The study investigated the impact of having a slider on sensing performance, confirming the feasibility of simultaneous sensing and driving. The implemented system achieved an interactive actuation that changed driving velocity according to the proximity distance of the human hand.

Abstract In the railway system, fasteners have the functions of damping, maintaining the track distance, and adjusting the track level. Therefore, routine maintenance and inspection of fasteners are important to ensure the safe operation of track lines. Currently, assessment methods for fastener tightness include manual observation, acoustic wave detection, and image detection. There are limitations such as low accuracy and efficiency, easy interference and misjudgment, and a lack of accurate, stable, and fast detection methods. Aiming at the small deformation characteristics and large elastic change of fasteners from full loosening to full tightening, this study proposes high-precision surface-structured light technology for fastener detection and fastener deformation feature extraction based on the center-line projection distance and a fastener tightness regression method based on neural networks. First, the method uses a 3D camera to obtain a fastener point cloud and then segments the elastic rod area based on the iterative closest point algorithm registration. Principal component analysis is used to calculate the normal vector of the segmented elastic rod surface and extract the point on the centerline of the elastic rod. The point is projected onto the upper surface of the bolt to calculate the projection distance. Subsequently, the mapping relationship between the projection distance sequence and fastener tightness is established, and the influence of each parameter on the fastener tightness prediction is analyzed. Finally, by setting up a fastener detection scene in the track experimental base, collecting data, and completing the algorithm verification, the results showed that the deviation between the fastener tightness regression value obtained after the algorithm processing and the actual measured value RMSE was 0.2196 mm, which significantly improved the effect compared with other tightness detection methods, and realized an effective fastener tightness regression.

Abstract This paper describes the development and the verification of flight test results of a differential pressure-based, two-dimensional low-airspeed sensor designed for the navigation or disturbance detection in small helicopters. The compact and lightweight sensor is integrated with the main rotor of a small helicopter and comprises two probes at both arm ends, a differential pressure sensor, rotary encoder with one magnet and two sensors, microcomputer, a wireless data link, and battery. It measures the differential pressure between the total pressures captured by two total-pressure probes at each rotor angle, instead of using static pressure probes. Thus, the airspeed of the fuselage can be evaluated from the low speed. Flight tests were conducted employing a reference ultrasonic two-dimensional airspeed sensor for comparison. The results demonstrated that the magnitude error of the airspeed is less than 2 m/s for low-airspeed flights ( $$

Abstract The Chinese express delivery industry processes nearly 110 billion items in 2022, averaging an annual growth rate of 200%. Among the various types of sorting systems used for handling express items, cross-belt sorting systems stand out as the most crucial. However, despite their high degree of automation, the workload for operators has intensified owing to the surging volume of express items. In the era of Industry 5.0, it is imperative to adopt new technologies that not only enhance worker welfare but also improve the efficiency of cross-belt systems. Striking a balance between efficiency in handling express items and operator well-being is challenging. Digital twin technology offers a promising solution in this respect. A realization method of a human–machine integrated digital twin is proposed in this study, enabling the interaction of biological human bodies, virtual human bodies, virtual equipment, and logistics equipment in a closed loop, thus setting an operating framework. Key technologies in the proposed framework include a collection of heterogeneous data from multiple sources, construction of the relationship between operator fatigue and operation efficiency based on physiological measurements, virtual model construction, and an online optimization module based on real-time simulation. The feasibility of the proposed method was verified in an express distribution center.

Abstract Inconel 718 (IN718) alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance. However, the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality (SQ) of the workpiece. In this work, grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel. The relationship between grinding speed, SQ and subsurface damage (SSD) was well studied. With increasing grinding speed, surface roughness decreased, and SQ was greatly improved. Meanwhile, the microhardness of the grinding surface declined as the grinding speed increased. The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s, then it decreased with higher grinding speeds. It was attributed to the mechanical-thermal synergistic effect in the grinding process. The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy. The conclusion in the work may also provide insight into processing other hard-to-machining materials.

Abstract Detecting contact when fingers are approaching an object and estimating the magnitude of the force the fingers are exerting on the object after contact are important tasks for a multi-fingered robotic hand to stably grasp objects. However, for a linkage-based under-actuated robotic hand with a self-locking mechanism to realize stable grasping without using external sensors, such tasks are difficult to perform when only analyzing the robot model or only applying data-driven methods. Therefore, in this paper, a hybrid of previous approaches is used to find a solution for realizing stable grasping with an under-actuated hand. First, data from the internal sensors of a robotic hand are collected during its operation. Subsequently, using the robot model to analyze the collected data, the differences between the model and real data are explained. From the analysis, novel data-driven-based algorithms, which can overcome noted challenges to detect contact between a fingertip and the object and estimate the fingertip forces in real-time, are introduced. The proposed methods are finally used in a stable grasp controller to control a triple-fingered under-actuated robotic hand to perform stable grasping. The results of the experiments are analyzed to show that the proposed algorithms work well for this task and can be further developed to be used for other future dexterous manipulation tasks.

Abstract Plastoelastohydrodynamic lubrication of rough surfaces (R-PEHL) is a cutting-edge area of research in interface fluid-structure coupling analysis. The existing R-PEHL model calculates the elastic-plastic deformation of rough surface by the Love equation in a semi-infinite space smooth surface, which deviates from the actual surface. Therefore, it is an innovative work to study the exact solution of elastic-plastic deformation of rough surface and its influence on the solution results of R-PEHL model. In this paper, a new contact calculation model of plastoelastohydrodynamic lubrication (PEHL) with three-dimensional (3D) rough surface is proposed by integrating numerical method of EHL and finite element method. The new model eliminates an original error introduced by the assumption of semi-infinite space in contact calculation, providing wide applicability and high accuracy. Under the given rough surfaces and working conditions, the study reveals that: (1) the oil film pressure calculated by the new model is lower than that of the smooth surface in semi-infinite space by 200–800 MPa; (2) the Mises stress of the new model is 2.5%–26.6% higher than that of the smooth surface in semi-infinite space; (3) compared with the semi-infinite space assumption, the rough surface plastic deformation of the new model is increased by 71%–173%, and the local plastic deformation singularity may appear under the semi-infinite space assumption; (4) the plastic deformation caused by the first contact cycle on the rough surface of the new model accounts for 66.7%–92.9% of the total plastic deformation, and the plastic deformation of the semi-infinite space accounts for 50%–83.3%. This study resolves the contradiction between the smooth surface assumption and the rough surface in the existing R-PEHL model, establishing a solid logic foundation for the accurate solution of R-PEHL model.

Abstract The tribological properties of self-lubricating composites are influenced by many variables and complex mechanisms. Data-driven methods, including machine learning (ML) algorithms, can yield a better comprehensive understanding of complex problems under the influence of multiple parameters, typically for how tribological performances and material properties correlate. Correlation of friction coefficients and wear rates of copper/aluminum-graphite (Cu/Al-graphite) self-lubricating composites with their inherent material properties (composition, lubricant content, particle size, processing process, and interfacial bonding strength) and the variables related to the testing method (normal load, sliding speed, and sliding distance) were analyzed using traditional approaches, followed by modeling and prediction of tribological properties through five different ML algorithms, namely support vector machine (SVM), K-Nearest neighbor (KNN), random forest (RF), eXtreme gradient boosting (XGBoost), and least-squares boosting (LSBoost), based on the tribology experimental data. Results demonstrated that ML models could satisfactorily predict friction coefficient and wear rate from the material properties and testing method variables data. Herein, the LSBoost model based on the integrated learning algorithm presented the best prediction performance for friction coefficients and wear rates, with R 2 of 0.9219 and 0.9243, respectively. Feature importance analysis also revealed that the content of graphite and the hardness of the matrix have the greatest influence on the friction coefficients, and the normal load, the content of graphite, and the hardness of the matrix influence the wear rates the most.