The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high deg...The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high degree of bending, and significant change of curvature. Aimed at optimizing the machining error, this paper presents a framework that integrates toolpath planning and process parameter regulation. Firstly, an Iterative Subdivision Algorithm(ISA) for clamped Bspline curve is proposed, based on which toolpath planning method towards the LE is developed.Secondly, the removal effect of Cutter Contact(CC) point on the sampling points is investigated in the calculation of grinding dwell time by traversing in u-v space. A global material removal model is constructed for the solution. Thirdly, the previous two steps are interconnected based on the Improved Whale Optimization Algorithm(IWOA), and the optimal parameter combination is searched using the Root Mean Square Error(RMSE) of the machining error as the objective function. Based on this, the off-line programming and robotic grinding experiments are carried out. The experimental results show that the proposed method with error optimization can achieve 0.0143 mm mean value and 0.0160 mm standard deviations of LE surface error, which is an improvement of32.5% and 33.9%, respectively, compared with previous method.展开更多
Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditi...Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditional approaches rely heavily on sophisticated algorithms and electronic sensor feedback systems to ensure landing stability,which increases the implementation complexity.Inspired by the process by which humans complete jumps and achieve stable landings in complex environments,this study proposes a novel landing control method for jumping robots.By designing a mechanically coupled perception-control structure based on mechanical logic computing,the robot simulates the real-time transmission of neural signals triggered by the ground reaction force(GRF)in human reflex loops,thereby simplifying traditional control approaches.Through the collaboration of a flexible mechanical spine and a bistable foot module,the robot achieves an average height of 16.8 cm and a distance of 25.36 cm in consecutive stable jumps.It also demonstrates reliable landing performance on challenging terrain including slopes and cobblestone surfaces.This paper proposes a novel landing control method for jumping robots that simplifies traditional control approaches.The method enables stable landings on complex terrain through a mechanically coupled perception-control structure.This approach has potential applications in tasks requiring mobility over uneven terrain,such as search and rescue.展开更多
This study presents a novel analytical algorithm for solving the forward position problem of a triangular platform Stewart-type parallel robot(STPR).By introducing a virtual chain and leveraging tetrahedral geometric ...This study presents a novel analytical algorithm for solving the forward position problem of a triangular platform Stewart-type parallel robot(STPR).By introducing a virtual chain and leveraging tetrahedral geometric principles,the proposed method derives analytical solutions for the position and orientation of the moving platform.The algorithm systematically addresses the nonlinearity inherent in the kinematic equations of parallel mechanisms,providing explicit expressions for the coordinates of key moving attachment points.Furthermore,the methodology is extended to general triangular platform STPRs with non-coplanar fixed attachments.Numerical validation through virtual experiments confirms the accuracy of the solutions,demonstrating that the mechanism admits eight distinct configurations for a given set of limb lengths.The results align with established kinematic principles and offer a computationally efficient alternative to iterative analytical approaches,contributing to the advancement of precision control in parallel robotic systems.展开更多
Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg all...Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg alloys are susceptible to issues like pitting or stress corrosion when utilized as key structural components in humid environments,resulting in corrosion fatigue,stress corrosion cracking,or even complete corrosion failure,which impedes their broader applications.To address these disadvantages of Mg alloys,surface selfnanocrystallization(SSNC),involving refining the grain size to create a nanosurface layer,has been proposed to delay or mitigate the initiation and propagation of cracks,thereby significantly enhancing corrosion resistance.The purpose of this paper is to review the effects of various surface self-nanocrystallization techniques,including surface mechanical attrition treatment,high-energy shot peening,ultrasonic surface rolling processing,laser shock peening,and supersonic particle bombardment,on the microstructure and properties of Mg alloys.Additionally,the mechanisms underlying the surface nanocrystallization-induced microstructural evolution in Mg alloys and the factors influencing their corrosion resistance are systematically summarized.Finally,the current challenges and prospects are discussed as well.展开更多
Ni-Cr-Co-W superalloy(GH4099)can be used to manufacture high-temperature structural components of aero-engine combustion chambers for long-term service below 900℃.This study provides a comprehensive evaluation of the...Ni-Cr-Co-W superalloy(GH4099)can be used to manufacture high-temperature structural components of aero-engine combustion chambers for long-term service below 900℃.This study provides a comprehensive evaluation of the GH4099 superalloy fabricated using the laser powder bed fusion(LPBF)technique,focusing on the opti-mization of processing parameters and a systematic investigation of the microstructural evolution and mechanical properties of the as-deposited and heat-treated samples.An optimal parameter combination was established using the response surface method(RSM)design and the variance method.The as-deposited GH4099 alloy is primarily composed of columnar crystals grown epitaxially and M_(23)C_(6)carbides without the generation of theγ′-phase.After solution treatment,recrystallization and grain growth occurred,with the alloy remaining as large,irregu-larly shaped polygonal columnar crystals.The aging process precipitated substantial′-phase,which internally existed as a mixture of equiaxed and columnar crystals.LPBF-GH4099 superalloy exhibited a maximum room-temperature tensile strength of 1137.80 MPa and a high-temperature tensile strength of 780 MPa at 800◦C.Various strengthening mechanisms were observed in the as-deposited and heat-treated samples.The most sig-nificant grain boundary strengthening effect was observed in the deposit state,while solution strengthening was primarily due to the segregation of elements,such as Mo,W,and Cr,in thematrix.Precipitation strengthening,predominantly due to the′-phase,emerged as the main strengthening mechanism for the GH4099 superalloy post-aging treatment.This study presents significant insights into the LPBF-GH4099 alloy and provides a solid foundation for future studies and practical applications in this field.展开更多
To improve the application and service of C_(f)/SiC composites as advanced hightemperature structural materials,it is critical to achieve their high-efficiency and low-damage machining.In this study,the laser-ablating...To improve the application and service of C_(f)/SiC composites as advanced hightemperature structural materials,it is critical to achieve their high-efficiency and low-damage machining.In this study,the laser-ablating assisted grinding(LAAG)method was presented,and the connection of damage behavior and removal mechanism with laser and grinding processes was revealed.The results demonstrated that the surface of C_(f)/SiC composites after laser ablation was covered with a substantial number of loose oxides primarily composed of SiO2.Laser ablating process,grinding parameter and abrasive belt selection have a significant impact on the machining results.By fabricating an ablative layer with small laser scanning spacing,and selecting small abrasive grains and feed rate during grinding,the machinability was improved and a relatively lowerdamage grinding surface could be obtained.Under the optimal combination of process parameters,the grinding force and temperature of LAAG could be reduced by up to 85%and 35%,respectively.In this case,the subsurface damage of C_(f)/SiC composites occurred only in the form of microcracks rather large-scale fracture,and the formation of interface debonding and matrix cracking was significantly reduced.Furthermore,the grinding chips were mostly shown as micron-sized powders,indicating that the removal mechanism of C_(f)/SiC composites was primarily the microfractured and attrition wear of laser-ablated layer.展开更多
Machinery condition monitoring is beneficial to equipment maintenance and has been receiving much attention from academia and industry.Machine learning,especially deep learning,has become popular for machinery conditi...Machinery condition monitoring is beneficial to equipment maintenance and has been receiving much attention from academia and industry.Machine learning,especially deep learning,has become popular for machinery condition monitoring because that can fully use available data and computational power.Since significant accidents might be caused if wrong fault alarms are given for machine condition monitoring,interpretable machine learning models,integrate signal processing knowledge to enhance trustworthiness of models,are gradually becoming a research hotspot.A previous spectrum-based and interpretable optimized weights method has been proposed to indicate faulty and fundamental frequencies when the analyzed data only contains a healthy type and a fault type.Considering that multiclass fault types are naturally met in practice,this work aims to explore the interpretable optimized weights method for multiclass fault type scenarios.Therefore,a new multiclass optimized weights spectrum(OWS)is proposed and further studied theoretically and numerically.It is found that the multiclass OWS is capable of capturing the characteristic components associated with different conditions and clearly indicating specific fault characteristic frequencies(FCFs)corresponding to each fault condition.This work can provide new insights into spectrum-based fault classification models,and the new multiclass OWS also shows great potential for practical applications.展开更多
Nonlinear characteristics have demonstrated significant advantages in mitigating vibrations across various engineering applications,particularly in effectively suppressing vibrations over a wide frequency range.This p...Nonlinear characteristics have demonstrated significant advantages in mitigating vibrations across various engineering applications,particularly in effectively suppressing vibrations over a wide frequency range.This paper introduces a novel nonlinear energy sink with a magnetic inerter(MINES).The MINES features a magnetic lead screw that incorporates a pair of helical permanent magnets.When the inner part undergoes linear motion,it is transformed into the rotation of the outer part at a predetermined conversion ratio.Subsequently,the MINES is incorporated into a system with a single degree of freedom,and the corresponding differential equations of motion are derived.The approximate analytical method and the numerical method are used to validate each other.This process clarifies the effectiveness of the MINES in reducing vibrations when subjected to harmonic excitation.The influence of the parameters of the MINES is analyzed.The findings demonstrate that the MINES offers significant benefits in terms of vibration suppression efficiency when the depths of the three barriers are equal.Furthermore,with the increase in excitation amplitude,the MINES enters the nonlinear range,leading to a reduction in system damping.This can effectively prevent the phenomenon of traditional damping stiffening under conditions of high amplitude excitation.Finally,the vibration reduction capability of this nonlinear energy sink was experimentally demonstrated,enhancing its applicability in vibration mitigation.展开更多
This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less spee...This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less speed regulation characteristics in a fan drive system.However,most of the existing models ignore the distribution differences of groove area along the radial direction,which may lead to significant deviations in calculating the mechanical property of friction pairs related to operating conditions and the engagement process.To fill this gap,a new calculation model for bearing capacity and frictional torque of friction pairs with different oil grooves is proposed,in which the traditional fixed contact area ratio coefficient for oil groove measurement is replaced by a more precise discrete micro-ring area ratio(DMAR)integration method.Then,a 32-degree-of-freedoms dynamic model of HVC at a fan drive system is established for the prediction of dynamic responses during speed regulation.Results show that friction pairs with different oil grooves have a direct influence on frictional torque and bearing capacity through the change of DMAR along the radial direction.The friction pairs with different groove structures have oscillation phenomena at the engagement steady-state boundary.Furthermore,a step-less speed regulation experimental setup is established to verify the correctness of the proposed model.It is demonstrated that the axial engagement force and the speed regulation curve predicted by the proposed method are in good agreement with the experimental data.The results could effectively predict the engagement dynamic characteristics.The numerical relationship among the structure parameters,the mechanical properties of friction pairs,and the speed regulation characteristics of the system are established through the proposed model,which lays a theoretical foundation for the structure design of friction plates and optimization of step-less speed regulation performance.展开更多
The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with...The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with outstanding mechanical performances.However,its creep mechanism has not been revealed yet.The present study systematically investigates and evaluates the high-temperature creep mechanism of LPBFed WE43 alloy under varying temperatures and applied stress conditions.In addition,it thoroughly elucidates the interactions and evolution mechanisms between precipitates and disloca-tions during the creep process.Subject to residual stresses and thermal cycling,theβphase is formed in the form of“precipitation chains”(PCs)within the grains.The metastable phasesβ″,β′,andβ_(1) in-situ precipitate between the PCs.The creep resistance of the(LPBFed)WE43 alloy is governed by the evolution of precipitates and their interactions with dislocations during the creep.Under creep condi-tions at 200℃,a large number of<c+a>anddislocations undergo climb and cross-slip behaviors within the grains.During the climb and cross-slip of dislocations,the Orowan strengthening effect ofβ″,the cutting mechanisms ofβ′andβ_(1) phases relative to dislocations,and the dislocation barriers formed by theβphase arrays collectively impart excellent creep resistance to the WE43 alloy.As creep time progresses,dislocations accumulate within the grains,and theβandβ_(1) phases promote the forma-tion of subgrain boundaries,further triggering discontinuous dynamic recrystallization behaviors during the creep process.Furthermore,influenced by the directional diffusion of elements,precipitates dynami-cally form around the grain boundaries of recrystallized grains,thereby enhancing the resistance to grain boundary sliding.When the creep temperature increases to 250℃ or 300℃,a large number of<c+a>dislocations,accompanied by the dissolution of metastable phases and elemental re-diffusion,transform during the creep process into stacking faults(SFs).SFs not only exhibit high thermal stability but also act as effective dislocation barriers at high temperatures through lattice mismatch mechanisms.However,under high-temperature conditions,thermal activation leads to the dissolution of unstable metastable phases,promoting rapid coarsening and transformation of precipitates into various morphologies ofβphases,thereby causing a catastrophic decline in creep performance.At the same time,high tempera-tures further exacerbate elemental diffusion,resulting in precipitate-free zones near grain boundaries,thereby inducing crack initiation.Therefore,the creep resistance of as-deposited alloys decreases signif-icantly at higher temperatures.Building on this,the future development trends of LPBFed WE43 alloys are envisioned,where homogenizing heterostructures or introducing high aspect ratio precipitates and high-density SFs prior to creep can be regarded as a promising approach for enhancing creep resistance in LPBFed WE43 alloys.展开更多
A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is...A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is expected to suppress the thermal deformation of shafts.A laser-assisted in-situ consolidation(LAC)process,together with its equipment,was developed to manufacture the hybrid shaft.Firstly,the optimal process parameters,including the laser-heated temperature and placement speed,were investigated.A maximum short-beam shear strength of 80.7 MPa was achieved when the laser-heated temperature was 500°C and the placement speed was 100 mm/s.In addition,the failure modes and the effect of environmental temperature on the CF/PEEK samples were analyzed.Both interlayer cracks and inelastic deformation failure modes were observed.The formation and propagation of cracks were further investigated through digital image correlation(DIC).Furthermore,internal defects of the CF/PEEK sample were detected using X-ray tomography scans,and a minimum porosity of 0.23%was achieved with the optimal process parameters.Finally,two steel–CF/PEEK hybrid shafts,with different fibre orientations,were manufactured based on the optimal process parameters.The surface temperature distributions and thermal deformations were investigated using a self-established deformation/temperature measurement platform.The hybrid shaft showed an 85.7%reduction in radial displacement with hoop fibre orientation and an 11.5%reduction in axial displacement with cross fibre orientation compared with the steel shaft.The results indicate that the proposed method has great potential to improve the thermal stability of hybrid shafts and the accuracy of machine tools.展开更多
Electrorheological(ER)and magnetorheological(MR)dampers,which are active damping devices,stand out for their exceptional performance in mitigating vibrations in mechanical systems and construction engineering.Their pr...Electrorheological(ER)and magnetorheological(MR)dampers,which are active damping devices,stand out for their exceptional performance in mitigating vibrations in mechanical systems and construction engineering.Their prowess lies in the inherent ability of ER/MR fluids to change their mechanical properties,particularly viscosity and shear stress,in response to the influence of electric or magnetic fields.In this study,a damper filled with Giant-ER(GER)fluid,a modified product of ER fluid,is employed in the rotor system for vibration suppression.This damper operates in a Cut submode derived from the conventional working modes.This mode results in an effective enhancement of the damping performance by integrating the advantages of these modes,thereby achieving a damping force density of 1.2×10^(4) N/m^(2) and a modulation coefficient of 15 within a multilayered cylindrical damper.Whereafter,the dynamics of the rotor system are modeled and analyzed based on the Jeffcott rotor model,which incorporates a parallelogram-structured motion decoupling mechanism equipped with the proposed Cut submode dampers that are introduced to reduce the vibration of the transmission shaft in the rotor system.Furthermore,to evaluate the damping effect,a vibration-damping performance validation testbed is constructed.The results are noteworthy,demonstrating that by leveraging the superior properties of the GER fluid,the Cut submode damper effectively suppresses the vibrations of the transmission shaft,particularly at the resonant frequencies,achieving an impressive 88.9%reduction when subjected to an electric field of 3 kV/mm compared to the action of 0 kV/mm.This performance highlights the exceptional effectiveness of the proposed Cut submode,underscoring its vast potential for various engineering applications.展开更多
Piezoelectric stages use piezoelectric actuators and flexure hinges as driving and amplifying mechanisms,respectively.These systems have high positioning accuracy and high-frequency responses,and they are widely used ...Piezoelectric stages use piezoelectric actuators and flexure hinges as driving and amplifying mechanisms,respectively.These systems have high positioning accuracy and high-frequency responses,and they are widely used in various precision/ultra-precision positioning fields.However,the main challenge with these devices is the inherent hysteresis nonlinearity of piezoelectric actuators,which seriously affects the tracking accuracy of a piezoelectric stage.Inspired by this challenge,in this work,we developed a Hammerstein model to describe the hysteresis nonlinearity of a piezoelectric stage.In particular,in our proposed scheme,a feedback-linearization algorithm is used to eliminate the static hysteresis nonlinearity.In addition,a composite controller based on equivalent-disturbance compensation was designed to counteract model uncertainties and external disturbances.An analysis of the stability of a closed-loop system based on this feedback-linearization algorithm and composite controller was performed,and this was followed by extensive comparative experiments using a piezoelectric stage developed in the laboratory.The experimental results confirmed that the feedback-linearization algorithm and the composite controller offer improved linearization and trajectory-tracking performance.展开更多
Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like l...Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like large temperature differentials,deformation and maintenance difficulties,which will severely impact transmission accuracy and service life.To meet the growing demands for high-performance gear transmissions with high transmission efficiency and error adaptability in the aerospace field,this paper proposes a novel curve-surface conjugate internal gear drive consisting of an involute internal gear and a curve-surface gear.The fundamental theory of curve-surface conjugation is introduced,and the construction method for curve-surface gear based on a selected contact path and meshing tube is presented.The analysis models including induced curvature,sliding ratio and tooth contact analysis with errors(ETCA)are simulated to evaluate the meshing characteristics.Additionally,prototypes are manufactured and experimental setups are established to validate the transmission performance.These results indicate that as the rotational speed increases,the transmission efficiency of the curve-surface conjugate internal gear drive improves,which is contrary to the trend observed in involute gear drives.And the transmission efficiency of the curve-surface conjugate internal gear drive surpasses that of the involute gear drive at higher rotational speeds.Moreover,this novel gear drive exhibits excellent error adaptability,maintaining intact contact paths and high transmission efficiency even in the presence of assembly errors.This study provides new ideas for the design and manufacture of high-performance gear transmissions from the perspective of spatial geometric elements.展开更多
How to substitute the human operator with a robot in various assembly tasks has to be taken into full con-sideration in intelligent manufacturing.Autonomous robotic assembly not only brings with high working effi-cien...How to substitute the human operator with a robot in various assembly tasks has to be taken into full con-sideration in intelligent manufacturing.Autonomous robotic assembly not only brings with high working effi-ciency,better product quality and low labor cost,but also helps relieve the increasingly severe problem of population aging.However,numerous existing challenges still prevent its wide applications when a robot is assigned to finish general tasks in unstructured environment.In order to provide a fundamental understanding of the various problems involved in robotic assembly,this paper carries out a review on its recent progress and challenges with 5 key technologies focused on:perception,end-effectors,control methods,learning methods and performance evaluation.Main works in these fields are reviewed and their characteristics are analyzed while typical assembly scenarios are covered.The challenges and future directions in robotic assembly are also dis-cussed on precise perception,robotic hand,error recovery and collaborative robot.In addition to providing a systematic summarization of the required key technologies,this work is aimed at motivating more potential researches in the community of robotics,artificial intelligence,and automation engineering.展开更多
Real-time monitoring of physiological signals on human skin surfaces represents a core functionality of wearable medical devices.Although microfluidic technology has garnered considerable attention in biochemical sens...Real-time monitoring of physiological signals on human skin surfaces represents a core functionality of wearable medical devices.Although microfluidic technology has garnered considerable attention in biochemical sensing(e.g.,sweat,glucose),its potential for physiological mechanosensing remains largely untapped,hindering multi-parameter integration in one platform.Herein,we introduce a dualmode flexible physiological force sensor based on microfluidic deformation.This sensor integrates capacitive and triboelectric mechanisms,overcoming single-mode sensing limitations.The liquid droplet serves a dual role:it acts as a deformable electrode,forming a capacitive structure with the bottom electrode for static force detection,while functioning as a triboelectric component interacting with the PDMS tribo-layer to capture dynamic force signals.Through parameter optimization,the sensor achieves synergistic optimization between sensitivity(4.078 kPa^(-1))and detection range,with dynamic response of 21 ms.Experimental validation demonstrated 168-hours stable underwater pulse monitoring,confirming its biomedical potential for mechanical-biochemical signal fusion and holistic physiaological analysis.展开更多
The design of specific mechanical metamaterials can be realized by introducing carefully designed structures into the material.In this study,the design of NiTi alloys with critical phase change stress was realized by ...The design of specific mechanical metamaterials can be realized by introducing carefully designed structures into the material.In this study,the design of NiTi alloys with critical phase change stress was realized by controlling the microporosity and Ni content of laser powder bed-fused NiTi alloys.This study shows that the mechanical properties of these metamaterials,including martensitic phase transition onset stress and superelasticity,can be modulated by tuning their microporosity and nickel content.The key to achieving this is to synergistically modulate the negative effects of micropores and the positive effects of Ni content.This study provides valuable insights for expanding the design of microstructured metamaterials in NiTi alloys.展开更多
The mutation operations and related control parameters play important roles in the performance of the differential evolution algorithm.Learning optimal policies for these strategies and parameters through reinforcemen...The mutation operations and related control parameters play important roles in the performance of the differential evolution algorithm.Learning optimal policies for these strategies and parameters through reinforcement learning is a hot topic.However,most of the current studies focus on either mutation strategy selection or the control parameters alone while the others keep fixed or self-adaptive,resulting in deteriorated performances.To address this gap,this paper proposes a framework for the joint adaptation of mutation strategies and related control parameters based on deep reinforcement learning.In this method,the distributed proximal policy optimization algorithm is employed to train the agents to dynamically select the optimal combination of mutation strategies and control parameters.To enhance the agent’s learning of the optimal policy,information derived from fitness landscape analysis is incorporated into the state representations.The training is conducted on the black-box optimization benchmark test problems,which are capable of generating large-scale test instances.Numerical results on the new problems from CEC2013 and CEC2017 test suites,and the real-world application of rover trajectory planning demonstrate that the proposed approach achieves competitive performance compared to state-of-the-art methods.The adaptation behavior and the contribution of learning are also thoroughly analyzed.展开更多
Under sustained strong stochastic impact loads,floating-supported friction plates are susceptible to the formation of fatigue cracks that propagate along the rim.The nonlinearity and randomness introduced by the crack...Under sustained strong stochastic impact loads,floating-supported friction plates are susceptible to the formation of fatigue cracks that propagate along the rim.The nonlinearity and randomness introduced by the cracked teeth participating in the impacts significantly influence the service life and reliability of the transmission system.In this paper,an improved stiffness excitation modeling method is developed for friction plate teeth with rim cracks.It overcomes the limitations of traditional approaches that fail to accurately assess the narrow-band,large-diameter friction plate teeth with rim cracks due to constraints imposed by boundary conditions.Then,an original dynamic impact model for the floating-supported friction plate and inner hub system is proposed,incorporating the effects of bending-torsional-axial-tilting coupled motions on tooth mesh excitations and dynamic responses.This model addresses the limitations of conventional models that only consider bending-torsion coupling,thereby providing a more comprehensive representation of the system's multi-dimensional dynamic behavior.The effects of the crack propagation depth and the number of cracked teeth on the stochastic impact characteristics and vibration responses of the system are investigated.Furthermore,finite element simulations and experimental tests are conducted to validate the cracked tooth stiffness excitations and dynamic impact responses,respectively.The proposed model is anticipated to provide both a theoretical foundation and practical guidance for fault diagnosis and reliability assessment of clutch friction plates.展开更多
In this paper,a hierarchical reinforcement learning(HRL)based real-time formation control approach is proposed for heterogeneous aerial-ground agents(HAGAs).Initially,to address the issue of imprecise modeling of HAGA...In this paper,a hierarchical reinforcement learning(HRL)based real-time formation control approach is proposed for heterogeneous aerial-ground agents(HAGAs).Initially,to address the issue of imprecise modeling of HAGAs,a unified heterogeneous chained system model is constructed using the hand-position method.Subsequently,a hierarchical framework is designed:(1)To decouple multi-agent collaborative interactions and individual dynamic rules through hierarchical resolution,which enables controller design to be independent of direct reliance on neighborhood collaborative errors.(2)By adopting a dual-layer framework that separates collaborative topology management from individual control strategies,seamless switching between multiple task scenarios can be achieved simply by reconstructing the collaborative topology of the first layer.Moreover,to overcome the issue of non-asymptotic stability of tracking errors caused by the discount factor in traditional optimal control,a cost function based on the derivative of the tracking error is introduced.This not only addresses the error issue caused by the discount factor but also effectively resolves the problem of the unboundedness of the quadratic cost function.Finally,the efficacy of the proposed algorithm is substantiated through simulation experiments.展开更多
基金supported by the National Natural Science Foundation of China (No. 52075059)Graduate Scientific Research and Innovation Foundation of Chongqing (No. CYB23021)the Innovation Fund of Aero Engine Corporation of China (No. ZZCX-2022-019)。
文摘The machining precision of blades is critical to the service performance of aero engines.The Leading Edge(LE) of high-pressure compressor blades poses a challenge for precision machining due to its thin size, high degree of bending, and significant change of curvature. Aimed at optimizing the machining error, this paper presents a framework that integrates toolpath planning and process parameter regulation. Firstly, an Iterative Subdivision Algorithm(ISA) for clamped Bspline curve is proposed, based on which toolpath planning method towards the LE is developed.Secondly, the removal effect of Cutter Contact(CC) point on the sampling points is investigated in the calculation of grinding dwell time by traversing in u-v space. A global material removal model is constructed for the solution. Thirdly, the previous two steps are interconnected based on the Improved Whale Optimization Algorithm(IWOA), and the optimal parameter combination is searched using the Root Mean Square Error(RMSE) of the machining error as the objective function. Based on this, the off-line programming and robotic grinding experiments are carried out. The experimental results show that the proposed method with error optimization can achieve 0.0143 mm mean value and 0.0160 mm standard deviations of LE surface error, which is an improvement of32.5% and 33.9%, respectively, compared with previous method.
基金Supported by New Chongqing Innovative Young Talent Project(Grant No.2024NSCQ-qncxX0468)Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX1283)Dreams Foundation of Jianghuai Advanced Technology Center(Grant No.2023-ZM01Z007).
文摘Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditional approaches rely heavily on sophisticated algorithms and electronic sensor feedback systems to ensure landing stability,which increases the implementation complexity.Inspired by the process by which humans complete jumps and achieve stable landings in complex environments,this study proposes a novel landing control method for jumping robots.By designing a mechanically coupled perception-control structure based on mechanical logic computing,the robot simulates the real-time transmission of neural signals triggered by the ground reaction force(GRF)in human reflex loops,thereby simplifying traditional control approaches.Through the collaboration of a flexible mechanical spine and a bistable foot module,the robot achieves an average height of 16.8 cm and a distance of 25.36 cm in consecutive stable jumps.It also demonstrates reliable landing performance on challenging terrain including slopes and cobblestone surfaces.This paper proposes a novel landing control method for jumping robots that simplifies traditional control approaches.The method enables stable landings on complex terrain through a mechanically coupled perception-control structure.This approach has potential applications in tasks requiring mobility over uneven terrain,such as search and rescue.
基金supported by the Opening Project of State Key Laboratory of Mechanical Transmission for Advanced Equipment(No.SKLMT-MSKFKT202330)the National Natural Science Foundation of China(No.52575022)the Jiangsu Province Postgraduate Research&Practice Innovation Program(No.KYCX25_1403)。
文摘This study presents a novel analytical algorithm for solving the forward position problem of a triangular platform Stewart-type parallel robot(STPR).By introducing a virtual chain and leveraging tetrahedral geometric principles,the proposed method derives analytical solutions for the position and orientation of the moving platform.The algorithm systematically addresses the nonlinearity inherent in the kinematic equations of parallel mechanisms,providing explicit expressions for the coordinates of key moving attachment points.Furthermore,the methodology is extended to general triangular platform STPRs with non-coplanar fixed attachments.Numerical validation through virtual experiments confirms the accuracy of the solutions,demonstrating that the mechanism admits eight distinct configurations for a given set of limb lengths.The results align with established kinematic principles and offer a computationally efficient alternative to iterative analytical approaches,contributing to the advancement of precision control in parallel robotic systems.
基金funded by the National Key R&D Program of China(No.2024YFB3713703,2023YFB3712700,2021YFB3702101)the Fundamental Research Funds for the Central Universities(2024IAIS-ZD004)+1 种基金State Key Laboratory of Mechanical Transmission for Advanced Equipment Open Fund(SKLMT-ZZKT-2024Z04)the support by the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(311021013).
文摘Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg alloys are susceptible to issues like pitting or stress corrosion when utilized as key structural components in humid environments,resulting in corrosion fatigue,stress corrosion cracking,or even complete corrosion failure,which impedes their broader applications.To address these disadvantages of Mg alloys,surface selfnanocrystallization(SSNC),involving refining the grain size to create a nanosurface layer,has been proposed to delay or mitigate the initiation and propagation of cracks,thereby significantly enhancing corrosion resistance.The purpose of this paper is to review the effects of various surface self-nanocrystallization techniques,including surface mechanical attrition treatment,high-energy shot peening,ultrasonic surface rolling processing,laser shock peening,and supersonic particle bombardment,on the microstructure and properties of Mg alloys.Additionally,the mechanisms underlying the surface nanocrystallization-induced microstructural evolution in Mg alloys and the factors influencing their corrosion resistance are systematically summarized.Finally,the current challenges and prospects are discussed as well.
基金supported by National Natural Science Foundation of China(Grant Nos.51975073,52335006,52201105)Natural Science Foundation of Chongqing China(Grant No.CSTB2022NSCQ-MSX0992)+2 种基金Innovation Support Program for Overseas Returnees in Chongqing China(Grant No.cx2023061)State Key Laboratory of Mechanical Trans-mission for Advanced Equipment of China(Grant No.SKLMT-MSKFKT-202104)The authors gratefully acknowledge all the researchers and laboratories for providing the experimental facilities.
文摘Ni-Cr-Co-W superalloy(GH4099)can be used to manufacture high-temperature structural components of aero-engine combustion chambers for long-term service below 900℃.This study provides a comprehensive evaluation of the GH4099 superalloy fabricated using the laser powder bed fusion(LPBF)technique,focusing on the opti-mization of processing parameters and a systematic investigation of the microstructural evolution and mechanical properties of the as-deposited and heat-treated samples.An optimal parameter combination was established using the response surface method(RSM)design and the variance method.The as-deposited GH4099 alloy is primarily composed of columnar crystals grown epitaxially and M_(23)C_(6)carbides without the generation of theγ′-phase.After solution treatment,recrystallization and grain growth occurred,with the alloy remaining as large,irregu-larly shaped polygonal columnar crystals.The aging process precipitated substantial′-phase,which internally existed as a mixture of equiaxed and columnar crystals.LPBF-GH4099 superalloy exhibited a maximum room-temperature tensile strength of 1137.80 MPa and a high-temperature tensile strength of 780 MPa at 800◦C.Various strengthening mechanisms were observed in the as-deposited and heat-treated samples.The most sig-nificant grain boundary strengthening effect was observed in the deposit state,while solution strengthening was primarily due to the segregation of elements,such as Mo,W,and Cr,in thematrix.Precipitation strengthening,predominantly due to the′-phase,emerged as the main strengthening mechanism for the GH4099 superalloy post-aging treatment.This study presents significant insights into the LPBF-GH4099 alloy and provides a solid foundation for future studies and practical applications in this field.
基金co-supported by the National Natural Science Foundation of China(No.52205444)the Natural Science Foundation of Chongqing(No.CSTB2022NSCQMSX1128)。
文摘To improve the application and service of C_(f)/SiC composites as advanced hightemperature structural materials,it is critical to achieve their high-efficiency and low-damage machining.In this study,the laser-ablating assisted grinding(LAAG)method was presented,and the connection of damage behavior and removal mechanism with laser and grinding processes was revealed.The results demonstrated that the surface of C_(f)/SiC composites after laser ablation was covered with a substantial number of loose oxides primarily composed of SiO2.Laser ablating process,grinding parameter and abrasive belt selection have a significant impact on the machining results.By fabricating an ablative layer with small laser scanning spacing,and selecting small abrasive grains and feed rate during grinding,the machinability was improved and a relatively lowerdamage grinding surface could be obtained.Under the optimal combination of process parameters,the grinding force and temperature of LAAG could be reduced by up to 85%and 35%,respectively.In this case,the subsurface damage of C_(f)/SiC composites occurred only in the form of microcracks rather large-scale fracture,and the formation of interface debonding and matrix cracking was significantly reduced.Furthermore,the grinding chips were mostly shown as micron-sized powders,indicating that the removal mechanism of C_(f)/SiC composites was primarily the microfractured and attrition wear of laser-ablated layer.
基金supported by the National Natural Science Foundation of China under Grant Nos.523B2043 and 52475112.
文摘Machinery condition monitoring is beneficial to equipment maintenance and has been receiving much attention from academia and industry.Machine learning,especially deep learning,has become popular for machinery condition monitoring because that can fully use available data and computational power.Since significant accidents might be caused if wrong fault alarms are given for machine condition monitoring,interpretable machine learning models,integrate signal processing knowledge to enhance trustworthiness of models,are gradually becoming a research hotspot.A previous spectrum-based and interpretable optimized weights method has been proposed to indicate faulty and fundamental frequencies when the analyzed data only contains a healthy type and a fault type.Considering that multiclass fault types are naturally met in practice,this work aims to explore the interpretable optimized weights method for multiclass fault type scenarios.Therefore,a new multiclass optimized weights spectrum(OWS)is proposed and further studied theoretically and numerically.It is found that the multiclass OWS is capable of capturing the characteristic components associated with different conditions and clearly indicating specific fault characteristic frequencies(FCFs)corresponding to each fault condition.This work can provide new insights into spectrum-based fault classification models,and the new multiclass OWS also shows great potential for practical applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.62203076,62103065,61922053,62325302,and U2013202)China Postdoctoral Science Foundation(Grant Nos.2021M700584 and 2022M710514)+2 种基金Program of Shanghai Academic/Technology Research Leader(Grant No.21XD1421400)Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyjzdxmX0014)the“Shuguang Program”(18SG36)supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission.
文摘Nonlinear characteristics have demonstrated significant advantages in mitigating vibrations across various engineering applications,particularly in effectively suppressing vibrations over a wide frequency range.This paper introduces a novel nonlinear energy sink with a magnetic inerter(MINES).The MINES features a magnetic lead screw that incorporates a pair of helical permanent magnets.When the inner part undergoes linear motion,it is transformed into the rotation of the outer part at a predetermined conversion ratio.Subsequently,the MINES is incorporated into a system with a single degree of freedom,and the corresponding differential equations of motion are derived.The approximate analytical method and the numerical method are used to validate each other.This process clarifies the effectiveness of the MINES in reducing vibrations when subjected to harmonic excitation.The influence of the parameters of the MINES is analyzed.The findings demonstrate that the MINES offers significant benefits in terms of vibration suppression efficiency when the depths of the three barriers are equal.Furthermore,with the increase in excitation amplitude,the MINES enters the nonlinear range,leading to a reduction in system damping.This can effectively prevent the phenomenon of traditional damping stiffening under conditions of high amplitude excitation.Finally,the vibration reduction capability of this nonlinear energy sink was experimentally demonstrated,enhancing its applicability in vibration mitigation.
基金Supported by the National Natural Science Foundation of China(Grant Nos.52475089,52035002)National Key Research and Development Program of China(Grant No.2021YFB2011400)the Chongqing Natural Science Foundation(Grant No.CSTB2022NSCQ-MSX1243).
文摘This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less speed regulation characteristics in a fan drive system.However,most of the existing models ignore the distribution differences of groove area along the radial direction,which may lead to significant deviations in calculating the mechanical property of friction pairs related to operating conditions and the engagement process.To fill this gap,a new calculation model for bearing capacity and frictional torque of friction pairs with different oil grooves is proposed,in which the traditional fixed contact area ratio coefficient for oil groove measurement is replaced by a more precise discrete micro-ring area ratio(DMAR)integration method.Then,a 32-degree-of-freedoms dynamic model of HVC at a fan drive system is established for the prediction of dynamic responses during speed regulation.Results show that friction pairs with different oil grooves have a direct influence on frictional torque and bearing capacity through the change of DMAR along the radial direction.The friction pairs with different groove structures have oscillation phenomena at the engagement steady-state boundary.Furthermore,a step-less speed regulation experimental setup is established to verify the correctness of the proposed model.It is demonstrated that the axial engagement force and the speed regulation curve predicted by the proposed method are in good agreement with the experimental data.The results could effectively predict the engagement dynamic characteristics.The numerical relationship among the structure parameters,the mechanical properties of friction pairs,and the speed regulation characteristics of the system are established through the proposed model,which lays a theoretical foundation for the structure design of friction plates and optimization of step-less speed regulation performance.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.52201105 and 52475324)the National Key Research and Development Program of China(Nos.2023YFB3408003 and 2023YFB3308001)+4 种基金the Graduate Sci-entific Research and Innovation Foundation of Chongqing(No.CYB23018)the Innovation Support Program for Overseas Re-turnees in Chongqing(No.cx2023061)the Research Project from Chongqing Key Laboratory of High-performance Structural Additive Manufacturing(No.02090011044158)the Chengdu Key Research and Development Support Program(No.2023-YF11-00077-HZ)the Fundamental Research Foundation for the Central Universities in China(Nos.2024IAIS-QN012 and 2023CDJKYJH049)。
文摘The complex non-equilibrium solidification effects of the laser powder bed fusion(LPBF)combined with the high solubility of rare-earth(RE)elements,provide a new advanced powder metallurgy process for Mg RE alloys with outstanding mechanical performances.However,its creep mechanism has not been revealed yet.The present study systematically investigates and evaluates the high-temperature creep mechanism of LPBFed WE43 alloy under varying temperatures and applied stress conditions.In addition,it thoroughly elucidates the interactions and evolution mechanisms between precipitates and disloca-tions during the creep process.Subject to residual stresses and thermal cycling,theβphase is formed in the form of“precipitation chains”(PCs)within the grains.The metastable phasesβ″,β′,andβ_(1) in-situ precipitate between the PCs.The creep resistance of the(LPBFed)WE43 alloy is governed by the evolution of precipitates and their interactions with dislocations during the creep.Under creep condi-tions at 200℃,a large number of<c+a>anddislocations undergo climb and cross-slip behaviors within the grains.During the climb and cross-slip of dislocations,the Orowan strengthening effect ofβ″,the cutting mechanisms ofβ′andβ_(1) phases relative to dislocations,and the dislocation barriers formed by theβphase arrays collectively impart excellent creep resistance to the WE43 alloy.As creep time progresses,dislocations accumulate within the grains,and theβandβ_(1) phases promote the forma-tion of subgrain boundaries,further triggering discontinuous dynamic recrystallization behaviors during the creep process.Furthermore,influenced by the directional diffusion of elements,precipitates dynami-cally form around the grain boundaries of recrystallized grains,thereby enhancing the resistance to grain boundary sliding.When the creep temperature increases to 250℃ or 300℃,a large number of<c+a>dislocations,accompanied by the dissolution of metastable phases and elemental re-diffusion,transform during the creep process into stacking faults(SFs).SFs not only exhibit high thermal stability but also act as effective dislocation barriers at high temperatures through lattice mismatch mechanisms.However,under high-temperature conditions,thermal activation leads to the dissolution of unstable metastable phases,promoting rapid coarsening and transformation of precipitates into various morphologies ofβphases,thereby causing a catastrophic decline in creep performance.At the same time,high tempera-tures further exacerbate elemental diffusion,resulting in precipitate-free zones near grain boundaries,thereby inducing crack initiation.Therefore,the creep resistance of as-deposited alloys decreases signif-icantly at higher temperatures.Building on this,the future development trends of LPBFed WE43 alloys are envisioned,where homogenizing heterostructures or introducing high aspect ratio precipitates and high-density SFs prior to creep can be regarded as a promising approach for enhancing creep resistance in LPBFed WE43 alloys.
基金supported by the National Nature Science Foundation of China(No.52175440)the Aeronautics Science Foundation of China(No.2023Z049076001)+3 种基金the Science and Technology Innovation Fund of Shanghai Aerospace(No.SAST2022-058)the Open Fund of State Key Laboratory of Mechanical Transmissions(No.SKLMT-MSKFKT-202202)the Key R&D Program of Zhejiang Province(No.2023C01058)the Experimental Technique Project of Zhejiang University(No.SYBJS202302),China.
文摘A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is expected to suppress the thermal deformation of shafts.A laser-assisted in-situ consolidation(LAC)process,together with its equipment,was developed to manufacture the hybrid shaft.Firstly,the optimal process parameters,including the laser-heated temperature and placement speed,were investigated.A maximum short-beam shear strength of 80.7 MPa was achieved when the laser-heated temperature was 500°C and the placement speed was 100 mm/s.In addition,the failure modes and the effect of environmental temperature on the CF/PEEK samples were analyzed.Both interlayer cracks and inelastic deformation failure modes were observed.The formation and propagation of cracks were further investigated through digital image correlation(DIC).Furthermore,internal defects of the CF/PEEK sample were detected using X-ray tomography scans,and a minimum porosity of 0.23%was achieved with the optimal process parameters.Finally,two steel–CF/PEEK hybrid shafts,with different fibre orientations,were manufactured based on the optimal process parameters.The surface temperature distributions and thermal deformations were investigated using a self-established deformation/temperature measurement platform.The hybrid shaft showed an 85.7%reduction in radial displacement with hoop fibre orientation and an 11.5%reduction in axial displacement with cross fibre orientation compared with the steel shaft.The results indicate that the proposed method has great potential to improve the thermal stability of hybrid shafts and the accuracy of machine tools.
基金supported by the National Natural Science Foundation of China(Grant Nos.62325302,U2013202,62203076)the Natural Science Foundation of Chongqing,China(Grant No.CSTB2024NSCQ-MSX0472)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.2024CDJCGJ-006,2024CDJGF-043,2024CDJZDQT-001,2023CDJXY-014)the Sichuan Provincial Science and Technology Program(Grant No.2023JDRC0069).
文摘Electrorheological(ER)and magnetorheological(MR)dampers,which are active damping devices,stand out for their exceptional performance in mitigating vibrations in mechanical systems and construction engineering.Their prowess lies in the inherent ability of ER/MR fluids to change their mechanical properties,particularly viscosity and shear stress,in response to the influence of electric or magnetic fields.In this study,a damper filled with Giant-ER(GER)fluid,a modified product of ER fluid,is employed in the rotor system for vibration suppression.This damper operates in a Cut submode derived from the conventional working modes.This mode results in an effective enhancement of the damping performance by integrating the advantages of these modes,thereby achieving a damping force density of 1.2×10^(4) N/m^(2) and a modulation coefficient of 15 within a multilayered cylindrical damper.Whereafter,the dynamics of the rotor system are modeled and analyzed based on the Jeffcott rotor model,which incorporates a parallelogram-structured motion decoupling mechanism equipped with the proposed Cut submode dampers that are introduced to reduce the vibration of the transmission shaft in the rotor system.Furthermore,to evaluate the damping effect,a vibration-damping performance validation testbed is constructed.The results are noteworthy,demonstrating that by leveraging the superior properties of the GER fluid,the Cut submode damper effectively suppresses the vibrations of the transmission shaft,particularly at the resonant frequencies,achieving an impressive 88.9%reduction when subjected to an electric field of 3 kV/mm compared to the action of 0 kV/mm.This performance highlights the exceptional effectiveness of the proposed Cut submode,underscoring its vast potential for various engineering applications.
基金supported by the National Key R&D Program of China (Grant No.2022YFB3206700)the Independent Research Project of the State Key Laboratory of Mechanical Transmission (Grant No.SKLMT-ZZKT-2022M06)the Innovation Group Science Fund of Chongqing Natural Science Foundation (Grant No.cstc2019jcyj-cxttX0003).
文摘Piezoelectric stages use piezoelectric actuators and flexure hinges as driving and amplifying mechanisms,respectively.These systems have high positioning accuracy and high-frequency responses,and they are widely used in various precision/ultra-precision positioning fields.However,the main challenge with these devices is the inherent hysteresis nonlinearity of piezoelectric actuators,which seriously affects the tracking accuracy of a piezoelectric stage.Inspired by this challenge,in this work,we developed a Hammerstein model to describe the hysteresis nonlinearity of a piezoelectric stage.In particular,in our proposed scheme,a feedback-linearization algorithm is used to eliminate the static hysteresis nonlinearity.In addition,a composite controller based on equivalent-disturbance compensation was designed to counteract model uncertainties and external disturbances.An analysis of the stability of a closed-loop system based on this feedback-linearization algorithm and composite controller was performed,and this was followed by extensive comparative experiments using a piezoelectric stage developed in the laboratory.The experimental results confirmed that the feedback-linearization algorithm and the composite controller offer improved linearization and trajectory-tracking performance.
基金Supported by Major Projects in Aviation Engines and Gas Turbines(Grant No.J2019-IV-0001-0068).
文摘Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like large temperature differentials,deformation and maintenance difficulties,which will severely impact transmission accuracy and service life.To meet the growing demands for high-performance gear transmissions with high transmission efficiency and error adaptability in the aerospace field,this paper proposes a novel curve-surface conjugate internal gear drive consisting of an involute internal gear and a curve-surface gear.The fundamental theory of curve-surface conjugation is introduced,and the construction method for curve-surface gear based on a selected contact path and meshing tube is presented.The analysis models including induced curvature,sliding ratio and tooth contact analysis with errors(ETCA)are simulated to evaluate the meshing characteristics.Additionally,prototypes are manufactured and experimental setups are established to validate the transmission performance.These results indicate that as the rotational speed increases,the transmission efficiency of the curve-surface conjugate internal gear drive improves,which is contrary to the trend observed in involute gear drives.And the transmission efficiency of the curve-surface conjugate internal gear drive surpasses that of the involute gear drive at higher rotational speeds.Moreover,this novel gear drive exhibits excellent error adaptability,maintaining intact contact paths and high transmission efficiency even in the presence of assembly errors.This study provides new ideas for the design and manufacture of high-performance gear transmissions from the perspective of spatial geometric elements.
基金Supported by National Natural Science Foundation of China(Grant No.52205009)Open Foundation of State Key Laboratory of Mechanical Transmission for Advanced Equipment of Chongqing University of China(Grant No.SKLMT-MSKFKT-202307)Taihu Lake Innovation Fund for the School of Future Technology of Southeast University of China.
文摘How to substitute the human operator with a robot in various assembly tasks has to be taken into full con-sideration in intelligent manufacturing.Autonomous robotic assembly not only brings with high working effi-ciency,better product quality and low labor cost,but also helps relieve the increasingly severe problem of population aging.However,numerous existing challenges still prevent its wide applications when a robot is assigned to finish general tasks in unstructured environment.In order to provide a fundamental understanding of the various problems involved in robotic assembly,this paper carries out a review on its recent progress and challenges with 5 key technologies focused on:perception,end-effectors,control methods,learning methods and performance evaluation.Main works in these fields are reviewed and their characteristics are analyzed while typical assembly scenarios are covered.The challenges and future directions in robotic assembly are also dis-cussed on precise perception,robotic hand,error recovery and collaborative robot.In addition to providing a systematic summarization of the required key technologies,this work is aimed at motivating more potential researches in the community of robotics,artificial intelligence,and automation engineering.
基金supported by the National Key Research and Development Program(2021YFA1201602),the NSFC(T2422003,52302219)the Fundamental Research Funds for the Central Universities(Grant No.2024CDTZCQ-012,2024CDJGF-031)。
文摘Real-time monitoring of physiological signals on human skin surfaces represents a core functionality of wearable medical devices.Although microfluidic technology has garnered considerable attention in biochemical sensing(e.g.,sweat,glucose),its potential for physiological mechanosensing remains largely untapped,hindering multi-parameter integration in one platform.Herein,we introduce a dualmode flexible physiological force sensor based on microfluidic deformation.This sensor integrates capacitive and triboelectric mechanisms,overcoming single-mode sensing limitations.The liquid droplet serves a dual role:it acts as a deformable electrode,forming a capacitive structure with the bottom electrode for static force detection,while functioning as a triboelectric component interacting with the PDMS tribo-layer to capture dynamic force signals.Through parameter optimization,the sensor achieves synergistic optimization between sensitivity(4.078 kPa^(-1))and detection range,with dynamic response of 21 ms.Experimental validation demonstrated 168-hours stable underwater pulse monitoring,confirming its biomedical potential for mechanical-biochemical signal fusion and holistic physiaological analysis.
基金supported by National Natural Science Foundation of China(Grant Nos.52201105,52475324)National Key Research and Development Program of China(Grant Nos.2023YFB3408003,2023YFB3308001)+7 种基金Graduate Scientific Research and Innovation Foundation of Chongqing(Grant No.CYB23018)New Chongqing Youth Innovative Talents Project(Grant No.2024NSCQ-QNCXX0342)Chongqing Technology Innovation and Application Development Special Major Project(Grant No.CSTB2024TIAD-STX0016)National Foreign Expert Project(Grant No.H20240161)Innovation Support Program for Overseas Returnees in Chongqing(Grant No.cx2023061)Research Project from Chongqing Key Laboratory of High-performance Structural Additive Manufacturing(Grant No.02090011044158)Chengdu Key Research and Development Support Program(Grant No.2023-YF11–00077-HZ)Fundamental Research Foundation for the Central Universities in China(Grant Nos.2024IAIS-QN012,2023CDJKYJH049).
文摘The design of specific mechanical metamaterials can be realized by introducing carefully designed structures into the material.In this study,the design of NiTi alloys with critical phase change stress was realized by controlling the microporosity and Ni content of laser powder bed-fused NiTi alloys.This study shows that the mechanical properties of these metamaterials,including martensitic phase transition onset stress and superelasticity,can be modulated by tuning their microporosity and nickel content.The key to achieving this is to synergistically modulate the negative effects of micropores and the positive effects of Ni content.This study provides valuable insights for expanding the design of microstructured metamaterials in NiTi alloys.
基金supported by the National Natural Science Foundation of China(No.52105244)the Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(No.GZKF-202425)+1 种基金the Entrepreneurship and Innovation Support Plan of Chongqing for Returned Overseas Scholars(No.cx2023085)the Independent Research Project-Key Program from the State Key Laboratory of Mechanical Transmission for Advanced Equipment(No.SKLMT-ZZKT-2024Z09).
文摘The mutation operations and related control parameters play important roles in the performance of the differential evolution algorithm.Learning optimal policies for these strategies and parameters through reinforcement learning is a hot topic.However,most of the current studies focus on either mutation strategy selection or the control parameters alone while the others keep fixed or self-adaptive,resulting in deteriorated performances.To address this gap,this paper proposes a framework for the joint adaptation of mutation strategies and related control parameters based on deep reinforcement learning.In this method,the distributed proximal policy optimization algorithm is employed to train the agents to dynamically select the optimal combination of mutation strategies and control parameters.To enhance the agent’s learning of the optimal policy,information derived from fitness landscape analysis is incorporated into the state representations.The training is conducted on the black-box optimization benchmark test problems,which are capable of generating large-scale test instances.Numerical results on the new problems from CEC2013 and CEC2017 test suites,and the real-world application of rover trajectory planning demonstrate that the proposed approach achieves competitive performance compared to state-of-the-art methods.The adaptation behavior and the contribution of learning are also thoroughly analyzed.
基金supported by the National Natural Science Foundation of China(Grant Nos.52505101,52475087,52475089,52365010)the Early-Career Young Scientists and Technologists Project of Jiangxi Province(Grant No.20252BEJ730175)。
文摘Under sustained strong stochastic impact loads,floating-supported friction plates are susceptible to the formation of fatigue cracks that propagate along the rim.The nonlinearity and randomness introduced by the cracked teeth participating in the impacts significantly influence the service life and reliability of the transmission system.In this paper,an improved stiffness excitation modeling method is developed for friction plate teeth with rim cracks.It overcomes the limitations of traditional approaches that fail to accurately assess the narrow-band,large-diameter friction plate teeth with rim cracks due to constraints imposed by boundary conditions.Then,an original dynamic impact model for the floating-supported friction plate and inner hub system is proposed,incorporating the effects of bending-torsional-axial-tilting coupled motions on tooth mesh excitations and dynamic responses.This model addresses the limitations of conventional models that only consider bending-torsion coupling,thereby providing a more comprehensive representation of the system's multi-dimensional dynamic behavior.The effects of the crack propagation depth and the number of cracked teeth on the stochastic impact characteristics and vibration responses of the system are investigated.Furthermore,finite element simulations and experimental tests are conducted to validate the cracked tooth stiffness excitations and dynamic impact responses,respectively.The proposed model is anticipated to provide both a theoretical foundation and practical guidance for fault diagnosis and reliability assessment of clutch friction plates.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2421001,61922053,62403298)the Natural Science Foundation of Shanghai(Grant No.25ZR1401119)+1 种基金the China Postdoctoral Science Foundation(Grant No.2024M751933)the Shanghai Post-doctoral Excellence Program(Grant No.2023316)。
文摘In this paper,a hierarchical reinforcement learning(HRL)based real-time formation control approach is proposed for heterogeneous aerial-ground agents(HAGAs).Initially,to address the issue of imprecise modeling of HAGAs,a unified heterogeneous chained system model is constructed using the hand-position method.Subsequently,a hierarchical framework is designed:(1)To decouple multi-agent collaborative interactions and individual dynamic rules through hierarchical resolution,which enables controller design to be independent of direct reliance on neighborhood collaborative errors.(2)By adopting a dual-layer framework that separates collaborative topology management from individual control strategies,seamless switching between multiple task scenarios can be achieved simply by reconstructing the collaborative topology of the first layer.Moreover,to overcome the issue of non-asymptotic stability of tracking errors caused by the discount factor in traditional optimal control,a cost function based on the derivative of the tracking error is introduced.This not only addresses the error issue caused by the discount factor but also effectively resolves the problem of the unboundedness of the quadratic cost function.Finally,the efficacy of the proposed algorithm is substantiated through simulation experiments.
