In recent years, the bidirectional bio-machine interface with the ability of neural control and sensory feedback has become the development trends of intelligent upper limb prosthesis. Most of the research focuses on the mechanism, sensor design and neural control of upper limb prosthesis, while less research on sensory feedback. The lack of reliable sensory feedback reduces the operational performance and limits the practical application of prosthetics. Firstly, the development status of bidirectional bio-machine interface of intelligent prosthesis is briefly summarized. Sensory feedback methods based on transcutaneous electrical nerve stimulation, vibration stimulation and pressure stimulation are introduced in detail. Sensory feedback strategies including sensory substitution, modality matched feedback and somatotopic matched feedback are also discussed. Based on the analysis, the naturalness of upper limb prosthetic sensory feedback and the multimodality of interactive information are prospected.

Wall climbing robot is an electromechanical system that can move on the surface of objects and complete operations with multiple degrees of freedom. It is especially suitable for performing special tasks, so it has a good application prospect and broad market demand. According to different adhesion mechanisms, wall climbing robots can be divided into negative pressure adsorption, electrostatic adhesion, gecko-like dry adhesion, bionic wet adhesion and so on. The research status of wall climbing robots at home and abroad is summarized from three aspects: adhesion mechanism, application scope and adhesion characteristics. In order to analyze and compare the load performance of different types of wall climbing robots, an analysis method of robot overall adhesion performance based on specific adhesion energy density is proposed, and a new material and structure design idea is proposed to solve the contradiction between large load and small volume. The application prospect of micro wall climbing robot in aero-engine fault detection is analyzed, and its development trends in the fields of intelligent materials, new driving, miniaturization and collaboration of adhesion mechanism are summarized.

As a promising autonomous observation platform for ocean phenomenon, underwater glider can achieve space motion by adjusting its net buoyancy and attitude. Because of the driving mode with relatively low energy consumption, underwater glider is suitable for long-term ocean exploration missions. For the multi-point exploration missions of underwater glider, this paper proposes a path planning method to minimize the glider energy consumption. First, the dynamic model of underwater glider is established, and the energy consumption model of the glider motion in a single profile is further deduced. Based on the simulation results, the polynomial fitting method is used for determining the approximate functional expressions among the glider energy consumption, voyage range, control parameter values and targeted diving depth. Under the specific motion path, the relationship between the glider energy consumption and the motion profile number is studied. Further, the path planning of multi-point exploration missions is regarded as a traveling salesman problem (TSP), and a genetic algorithm-based method is proposed to solve the above path planning problem. The numerical example illustrates that the proposed path planning method can effectively reduce the energy consumption of underwater glider when carrying out the multi-point exploration mission.

The lithium-ion battery(LIB) is prone to the expected over-heating and quick degradation during the fast charging.Therefore, it is of great significance to constrain the key intermediate physical states of LIB actively within a reasonable range, while pursuing the speed of charging. Motivated by this, a multiple physics-constrained fast charging strategy is proposed for the LIB. A comprehensive electro-thermal-aging model is established and validated under typical charging scenarios. On this basis, a model-based observer is designed to estimate the state of charge and internal temperature of LIB in real time. Accounting for multiple conflicting objectives, i.e., the charging speed, temperature rise and degradation rate, a model predictive control-based strategy is proposed to optimize the charging process of LIB. Experimental results suggest that the proposed charging strategy can actively constrain the internal temperature of battery below the predetermined threshold. With a comparable charging speed, the proposed charging strategy leads to a slower degradation than the widely-used constant-current-constant-voltage charging strategy. The capacity decays within 200 charge-discharge cycles are 2.12% and 4.88%, respectively, for the two strategies. Based on the model predictive control, the proposed fast charging strategy constrains the battery internal states effectively, while a comprehensive promotion in terms of rapidity, safety and life extension is realized.

Improving the accuracy and speed of the inverse kinematics of multi axis robots is the basis of improving the performance of trajectory planning and real-time control of robots, and it is also a difficult problem in the robot field. A high-precision and efficient method for solving the inverse kinematics of 3 to 6 degrees of freedom serial robot is presented in the paper. Firstly, the rotation transformation matrix and unit quaternion used to describe the position and attitude of the robot are expressed in the form of the tangent of half angles, and the position equation is established without redundancy of joint angles. Secondly, the Dixon resultant method for solving multivariate high-order polynomials is analyzed and applied to solve the inverse kinematics of 3R robots and general 6R robots. Using the characteristics of polynomial ring to process the matrix can effectively avoid the occurrence of computational singularity. By analyzing the Dixon matrix expressed in vector, some invalid terms in the matrix are eliminated, the size of the matrix is reduced, and the occurrence of order combination explosion problem is reduced. The simulation example shows that the inverse kinematic solution of 6R robot can generally reach 8 groups, and this performance improves the dexterity of robots. The single calculation time is not more than 4 ms, and the position and attitude errors (relative) are less than 10^‒15. The efficiency and precision of the proposed inverse kinematics method are verified. The work of this paper provides a theoretical basis for the kinematics research of precision manipulator.

As the foundation and core of various heavy aircraft transmission systems, the reliability level of large-scale aviation planetary mechanism restricts the economic affordability and service safety for the aircraft to a great extent. A model of heavy helicopter planetary mechanism as the object of study, and aims to improve the fatigue reliability level of the system. The fatigue load history of the gear teeth under the coupling of global elastic behavior of the system is calculated using a hierarchical finite element method, and the probabilistic fatigue strength of gear teeth is fitted based on the gear low circumference fatigue test with the minimum order statistics transformation method to provide cost-effective load and strength input variables for the system reliability prediction model. Based on this, a mapping path from the key structural elements of large-scale aviation planetary mechanism to the system reliability indexes is established, and then a new method of reliability-driven multi-objective optimization design for planetary mechanism structural dimensions is proposed. Finally, the influence law of ring gear rim thickness and planet carrier baseplate thickness on the fatigue reliability of the planetary gear train is analyzed, and the results of the best stiffness matching between the rim and baseplate dimensions for the specified type of large aviation planetary mechanism can be obtained. The stiffness potential of the core structural elements is maximized as a way to balance the contradiction between reliability and lightweight requirements of large aviation planetary equipment.

State of health estimation of power batteries is one of the key algorithms of the battery management systems, which is of great significance for improving power battery energy utilization efficiency, reducing thermal runaway risk, as well as power battery maintenance and residual value evaluation. Comparative analysis has been done on experimental-based, model-based and data-driven methods, and data-driven methods are elaborated from three aspects:dataset construction, health indicators extraction, model establishment. The big data collection methods and data preprocessing methods are summarized. The health indicators extraction methods are compared by their pros and cons and applicable scenarios. The basic principles of different health state estimation models are discussed. The conclusion that model fusion is the direction of future technology development is proposed. Finally, facing the future application scenarios of big data in electric vehicles, the current issue and prospective are depicted.

Micrometer indentation technology has been able to achieve quasi-nondestructive testing of the mechanical properties of ductile metal materials. Compared with the traditional mechanical properties testing methods, this technology can not only realize the quasi-nondestructive evaluation of mechanical properties of micro-scale complex structures such as welded joints and additive repair interfaces, but also be used for monitoring the mechanical properties of in-service equipment important components, which provides a basis of their safety warning and life prediction. The current research status of uniaxial tensile properties and fracture toughness evaluation technology based on micron indentation technology is summarized systematically. First of all, the basic principles and technical lines of various evaluation models are presented completely, and the advantages and limitations of different evaluation models are analysed systematically. Secondly, the standards and guidelines for micrometer indentation technology are summarized.After that the problems and challenges of micrometer indentation technology are discussed from the perspectives of both theoretical studies and engineering applications, respectively. Finally, the development and application trends of micron indentation mechanical properties testing technology are prospected.

The design requirements for leg design of biped robots with high dynamic performance is investigated, the design criteria, design schemes and implementation of the robot leg are obtained. A novel series-parallel configuration of the robot legs is proposed, the actuator of knee joint moves up to the hip joint, the actuator of ankle joint moves up to the knee joint, the motion of knee joint actuator transmit to the knee through a simplified five-link mechanism, and the motion of ankle joint actuator through parallel four linkage mechanism transmit to the ankles. The kinematics forward and inverse solution of the ankle joint and the entire leg joint are carried out, and a simulation model of the new configuration robot is established. Considering the motion control algorithm, the robot dynamics simulation is completed. The performance of the quasi-direct drive actuator is tested, the experimental verification of the series-parallel configuration of the leg prototype is completed. The robot achieves a walking speed of 0.4 m/s. The results indicate that the proposed new series-parallel configuration of the robot leg has better motion performance than the traditional series configuration one, the performance of the new configuration of the robot is verified n the real machine experiment. The new serial-parallel configuration scheme has broad application prospects in the field of biped robots and other service robots.

To meet the increasing demands of the high capacity cryocoolers used in space applications, a high-capacity pulse tube cryocooler has been successfully developed by the Technical Institute of Physics and Chemistry(TIPC). This cryocooler is driven by a linear compressor which consists of two dual-opposed pistons. The effects of inertance tube assembly, working pressure and input electrical power on the cooling performance of pulse tube cryocooler were studied by experiments. When the operating frequency is 50 Hz and the mean working pressure is 3.5 MPa for helium gas, the high efficiency pulse tube cryocooler achieves a no-load temperature of about 34 K. When the input power is 350 W and the reject temperature is 300 K, the cooling performance of the pulse tube cryocooler is 20.5 W at 80 K, and the relative Carnot efficiency of the whole cryocooler reaches 16.1%.

Continuum robots are gradually being widely used in minimally invasive interventional surgery. The precise navigation and control of continuum robots has become a research hotspot and difficulty in the field of medical imaging and surgical robots. Fiber-optic navigation is regarded as one of the most promising navigation technologies for continuum robots. After more than 40 years of development, great progress has been made in related theories and methods, technology and systems, and clinical trials at home and abroad, which has promoted the clinical application of this technology. However, there are still several problems that limit the application and development of this technology, and it is urgent to explore solutions. To this end, the research and development history of optical fiber navigation technology is sorted out. The main technical types, technical advantages and disadvantages and key core algorithms of fiber-optic navigation are analyzed. The key issues that need to be studied and resolved are pointed out. The future development is discussed considering the high-precision positioning, force tactile feedback, multi-modal image fusion recognition, intelligence and productization etc.

Silicon carbide ceramic matrix composites (SiC-CMC) have many advantages, such as high hardness, high strength, high temperature resistance, corrosion resistance etc, showing great application potential in aerospace, nuclear industry, braking system. However, the characteristics of anisotropy, heterogeneity and hard brittleness of SiC-CMC make it very difficult to process. The traditional machining method has some problems such as difficult to control the surface quality, serious tool wear and low machining efficiency. In order to solve the above problems, special processing technology was tried to adopt machining SiC-CMC. However, there are many kinds of special processing technology, which involves more knowledge than traditional processing technology, wide and miscellany. In this paper, laser machining, abrasive water jet machining and electric discharge machining, which are of higher engineering practical value and stronger foundation, are selected to carry out a review. Firstly, the problems of three kinds of special processing technology are introduced and then the methods to solve the problems are summarized. Finally, the advantages and disadvantages of the three are compared and the conclusions are drawn:special processioning technology has its own advantages, laser machining is suitable for machining micro-pores, micro-grooves and other micro-textures; Abrasive water jet machining has higher processing efficiency and can process large complex components. EDM equipment investment is cheap, good at processing thin-plate components and deep cavity groove. Special processioning techniques are neither exclusive nor substitutes for each other, but should complement each other and give play to their advantages to produce complex components with high efficiency and precision.

In the existing research on the remaining useful life prediction of stochastic degradation equipment with imperfect maintenance, only the single influence of maintenance activities on the degradation state or degradation rate is usually considered,while the research that considers both two influences ignores the unit-to-unit variability of degradation equipment. In view of this, an adaptive remaining useful life prognostic approach based on a multi-stage diffusion process is proposed, which takes into account the influence of imperfect maintenance activities on the degradation state and degradation rate, and describes the update process of degradation rate with observation data by using a random walk model to characterize the unit-to-unit variability of equipment. Based on the historical degradation data, the initial values of degradation model parameters are obtained by the maximum likelihood estimation method. Based on the state observation data, the Kalman filtering and expectation-maximization algorithm are used to adaptively update the model parameters. The probability density function of the remaining useful life in the sense of the first hitting time is derived by the convolution operator and the Monte Carlo method. Finally, the effectiveness and superiority of the proposed approach are verified by the simulation example and the case study of gyroscopes.

For the difficult manufacture of the core components and the unknown dynamic slip-limiting mechanism of the variable transmission ratio differential, a new type of variable transmission ratio differential based on non-circular face gear is presented, with the configuration principle and dynamic antiskid slip mechanism of the differential studied. The transmission principle of cylindrical gear and non-circular face gear is given to illustrating the the configuration principle of the new differential. For the condition that the vehicle is in trouble due to the skidding of the single-side drive wheel, the kinematics expression of the non-circular gear differential is obtained according to the mechanism rotation method. Based on the theory of advanced dynamics, the mechanics equilibrium equation of each component of non-circular face gear differential is constructed, with the vehicle traction force formula deduced. Then a dynamic model of horizontal movement of the vehicle driven by a non-circular face gear differential is established. The torque distribution of the differential on the two driving wheels, the change of dynamic traction force and the vehicle's escape behavior are studied by the method of test and simulation. The results show that the non-circular gear differential makes the slip wheel produce periodic inertia torque, which is beneficial to improve the maximum traction force of the vehicle and is the fundamental reason for the dynamic antiskid slip of the variable transmission ratio differential. Increasing the input speed of the differential not only could effectively improve the average speed of the vehicle out of distress but also increase the amplitude of the flexible impact on the vehicle. The research results provide a certain theoretical basis for the design of variable transmission ratio differential.

Combined with differential gear train and lever principle, a variable stiffness actuator with stiffness adjustment range from 0 to +∞ is designed, and its structure optimization design and energy consumption optimization design are completed. The variable stiffness actuator has the advantages of large range of variable stiffness, low energy consumption demand for stiffness adjustment, small space occupation, easy control, fast response speed, strong reliability, high feasibility of technical implementation, and has certain practical application significance. On this basis, an underactuated flexible claw with variable stiffness is designed. The variable stiffness actuator is taken as the driving unit of the claw joint, and the stiffness of the claw is changed by adjusting the stiffness of the variable stiffness actuator. Finally, the hardware platform of variable stiffness flexible claw was built, and the stiffness of the variable stiffness actuator was measured, which verified the feasibility of the variable stiffness actuator designed for stiffness regulation. The force control experiment of flexible hand claw with variable stiffness is carried out, and the grasping of soft object is realized successfully. The performance of the single finger of the variable stiffness flexible claw is analyzed, and the positive correlation between the finger stiffness and the stiffness of the variable stiffness actuator is verified, and the performance experimental verification of the variable stiffness flexible claw is completed.

Planetary lava tubes which are shortcuts into the extraterrestrial ground are of particular interest to scientific and mineral exploration. This research presents a new tethered planetary lava tube exploration rover and researches its parametric design method. With consideration of steering and tether-assisted release and retrieve on the cliff of the lava tube, the configuration of the planetary rover is designed. Based on terramechanics, the parametric optimization design of the tethered three-wheeled mobile mechanism is completed with consideration of mobility on deformable terrains around the entrance of the lava tube and in the accumulation area at the bottom of the lava tube, as well as the load distribution, placidity and anti-tipping on the non-deformable terrain the of lava tube. Simulation and experimental results demonstrate that the planetary rover designed by using the proposed method satisfies the technical requirements; compared with those without optimization, the rover has stronger mobility, which supports the parametric design of multi-wheel (4-wheel, 6-wheel, etc.) planetary rovers.

To solve all the inverse kinematics solutions of the redundant manipulators, a new self-motion manifolds calculation method is proposed to calculate the self-motion manifolds including all inverse kinematics solutions. This method is based on the artificial bee colony algorithm to complete the initial value search of each branch of self-motion manifolds, which solves the problem that the initial value of the branch is difficult to determine. Furthermore, a branch search strategy is proposed to realize the search of complete manifolds branches. On this basis, to improve the calculation efficiency of self-motion manifolds, the congruence and gradient of self-motion manifolds are defined, and the manifolds library is established. By indexing the self-motion manifolds in the manifolds library, the self-motion manifolds at any position in the workspace can be quickly calculated. The manifolds library is used to analyze the global performance of the manipulators, and the local optimal configurations on each branch are obtained. The local optimal configurations of each branch are used as the initial configuration for joint trajectory planning, and the global optimal joint trajectory planning for a given end trajectory is realized. The 4R manipulator and 7R manipulator verify the method's effectiveness. This method can also be used to calculate the self-motion manifolds of hyper-redundant manipulators, and it has good universality.

Higher strength of high-strength steel can be obtained by controlling microstructure, but the microscopic uneven deformation and micro-induced plasticity mechanism of different grades of high-strength steel are different, which makes the unloading and reverse loading behavior of high-strength steel more complicated and increases the difference between grades. For this reason, a systematic strategy of model adaptive matching and parameter decoupling matching to achieve accurate prediction of high-strength steel springback is given. Firstly, a hybrid hardening model of power function and exponential function is proposed.Based on the hybrid hardening model, the bending moment balance equation for free bending load and curvature constraint equation are raised. In view of the variable modulus model, the integral equation of the section elastic bending moment is established. A sub-optimization model is established to reversely identify the unloading parameters basing on the loading and unloading analytical models. The matching strategy including variable modulus linear and nonlinear kinematic hardening models and variable modulus kinematic hardening models with boundary surface is determined. Based on the experimental data of tension and compression, free bending and uniaxial tension, the optimization sequence of the corresponding constitutive sub-optimization model parameters is determined, and a systematic strategy of constitutive matching and its parameter decoupling calibration is formed finally, and calibration library is developed on the basis of the Fortran language. A prediction model for U-shaped bending parts and arc-shaped bending parts is established, and the recognition results and springback prediction results of DP980 and DH980 high-strength steels at different strain levels are compared and analyzed. The decoupling calibration strategy is verified. Not only the correlation of data of different grades of high-strength steel but also the accuracy and stability of the model under the same grade is greatly increased. It lays the foundation for the research on the unified self-identification method of material properties in view of data.

The existing heavy-duty industrial robots are short of force control functionality, which makes them difficult to perform contact-operations such as deburring, chamfering, and polishing. A 3-DOF translational force-controlled end-effector featured with 3-P(UU)₂ parallel mechanism and gas springs inside is introduced, and the robust adaptive force tracking admittance control method is proposed to regulate the contact force in the operational space. It can be applied to the robotic grinding and polishing process of the lateral surfaces, holes and narrow structures of workpieces. Based on the modeling of the forward and inverse kinematics of the parallel mechanism, and the dynamics of the pneumoelectric actuator, the robust adaptive force tracking admittance controller is designed. Experimental results show that the 3-DOF translational force-controlled end-effector based on robust adaptive admittance control tracks force fast and precisely, with the steady-state force error ‒4.5×10^‒4 N and the rise time 19.27 ms. The settling time 116.0 ms and overshoot 57.5% demonstrates good impact resistance and vibration absorption characteristics. Furthermore, the standard deviation and average peak of the contact force during the movement in a plane and cylindrical surface are 0.143 N and 0.694 N, respectively, indicating the adaptability to the environmental displacement error and stiffness variation under grinding tools made of different materials. The add-on force-controlled end-effector presented can improve the quality of the advanced robotic contact operations and expand the applications of the industrial robots.

At present, obvious difference in maneuverability exists between the micro biomimetic flying aerocraft and its biomimetic prototype in the landing/take-off process, which reduces the safety of its operation process and the universality of its application scope. Accurate characterization of contact force of biomimetic prototype in the landing/take-off process without interference is a necessary prerequisite to solve this problem. A micro-Newton scale contact force measurement system for small flying insects during landing/take-off was designed. The carbon fiber spring T300 was selected as the sensing device of contact force and calibrated to obtain the mathematical equation involved contact force-deflection-contact point position (goodness of fit R²=0.979). A high frame camera was selected to record the image information of small flying insects during landing on and take-off from the carbon fiber spring. Taking the fly (Musca domestica) as the small flying insect, the operation debugging of the contact force measurement system was conducted. The image analysis and processing program based on the Matlab software was used to accurately obtain the deflection of carbon fiber spring and the position of landing/take-off contact point. According to the mathematical equation, the contact force was calculated and corrected to eliminate the influence of carbon fiber spring’s gravity. Result shows that the contact force of flies during landing/take-off process ranges from 0.121 mN to 0.772 mN, which is about 0.71 to 4.53 times of their body weight (17.38 mg). Four the designed contact force measurement system, its resolution is 0.001 mN and its accuracy is improved by four aspects: simulation/actual calibration, accurate acquisition of deflection, contact force correction and no interference in landing/take-off process. Our result provides a reference technology/method for the quantitative and accurate characterization of the biomimetic prototype’s movement behavior for developing micro flying aerocraft.

Axial ultrasonic assisted face grinding is widely used in difficult-to-machine material machining and the surface topography and roughness, which have significant influence on friction and fatigue properties. Ultrasonic vibration amplitude has a considerable influence on axial ultrasonic assisted facing grinding surface topography and roughness. In present surface topography and roughness prediction models, the influence of load on vibration amplitude has not been considered, so an axial ultrasonic assisted face grinding metal surface topography and roughness prediction model considering the variation of amplitude is proposed. A model of grinding wheel end face is built according to the wheel size and granularity. Three dimensional grinding trajectory is described mathematically. The three dimensional surface topography data and roughness of machined surface are calculated. On this basis, variation of surface roughness with ultrasonic vibration amplitude is investigated. Consequently, a concept of amplitude attenuation topography mapping coefficient is processed, and its calibration method is also given. Further, the amplitude with loaded could be calculated via the amplitude attenuation topography mapping coefficient. With the amplitude with loaded, the surface topography and roughness are gained with the axial ultrasonic assisted face grinding metal surface topography and roughness prediction model. Finally, accuracy of the prediction model is verified via axial ultrasonic assisted face grinding experiments.

Compliant mechanisms have a great application potential in ultra-precision MEMS(Micro-Electro Mechanical System) of aerospace, biomedical, bionic robot and other high-tech fields. At present, topology optimization is one of the main methods in configuration design of compliant mechanisms. In order to solve the problem of de facto hinges in the traditional topology optimization of compliant mechanisms, firstly, the rotation angle is introduced into the configuration design of the compliant mechanism. Then, the causes of the emergence of de facto hinges in the optimum results obtained by topology optimization are analyzed by taking the rotation angle as the observation. Secondly, the topology optimization model of hinge-free compliant mechanisms is established by limiting the average of squared rotation within the design domain to the allowable value, and the corresponding sensitivity analysis formulas are derived by the adjoint method. Finally, the feasibility and effectiveness of the proposed optimization model are verified by topology optimization of two classical examples, namely reverse displacement mechanism and flexible clamp. The results show that hinge-free compliant mechanisms with truss-like configuration obtained by the rotation constraint strategy exhibit a certain degree of reduction in the input displacement and output displacement, but the problems of excessive local strain and stress concentration are avoided.

Due to the geometric and non-geometric errors of the robot body structure, the actual trajectory of the robot has a big deviation from its nominal trajectory, which seriously limits the application of the robot in machining. Note that the positioning accuracy of the robot will be significantly deteriorated with the degradation of the working performance of the robot during the service time, in addition to the differential distribution of the positioning error levels in the workingspace of the robot. To cope with this problem, an adaptive online compensation method based on fixed-length memory window incremental learning is proposed to compensate the positioning errors of the industrial robot during long-term service. Firstly, the correlation between positioning errors and robot poses is quantitatively studied, and the workspace is divided into several pose blocks and a calibration sample library is created, thus an adaptive optimization mechanism of mapping model is established to address the problem of differential distribution of error levels in workingspace. Secondly, the incremental learning algorithm with fixed-length memory window is designed to overcome the catastrophic forgetting of neural network model and balance the accuracy and efficiency of establishing the mapping relationship between new and old robot pose data in online mode, solving the problem that robot performance degradation aggravates positioning errors and affects the applicability of pose mapping model. Finally, the proposed method is applied to long-term compensation case of Stäubli robot and UR robot, and experimental result shows the proposed method reduces the positioning error of the Stäubli robot from 0.85 mm to 0.13 mm and UR robot from 2.11 mm to 0.17 mm, respectively, outperforming similar methods.

Compressive spherical beamforming(CSB) based on solid spherical microphone array enjoys the advantages of panoramic sound imaging, suitable for medium and long distance measurement and easy to arrange, so it has broad application prospects in the field of noise source identification such as automobiles and airplanes. The recently proposed CSB based on Maximum type-II likelihood estimation(MLE-II) under sparse Bayesian learning(SBL) framework can achieve good low-frequency sound source identification performance, but it needs to estimate the sound source sparsity, and the anti-noise interference ability and computational efficiency also need to be improved. To solve the above problems, MAP-EM-based CSB(MAP-EM-CSB) without sound source sparsity estimation is proposed, which transforms the mathematical model solving problem of CSB into the maximum a posteriori(MAP) estimation problem of the source intensity distribution under SBL framework, and then uses the expectation maximization(EM) algorithm to solve it. Further, the sound pressure complex matrix input of MAP-EM-CSB is converted into the average sound pressure cross-spectrum matrix input of multiple snapshots, and then the enhanced MAP-EM-CSB(EMAP-EM-CSB) is established based on the diagonal reconstruction and noise reduction of the cross-spectrum matrix. Both simulations and experiment show that the proposed MAP-EM-CSB and EMAP-EM-CSB have high spatial resolution and computational efficiency. Due to its strong anti-noise interference capability, EMAP-EM-CSB has better sound source identification performance, especially in low frequency and low signal-to-noise ratio environments. Finally, the effects of the number of iterations and snapshots on the performance of MAP-EM-CSB and EMAP-EM-CSB are analyzed, and the recommended values are obtained.

Currently, there is a lack of research on wearable devices that focus on assisting lower limbs to improve physical fitness training. The synergistic research of exoskeleton and virtual reality is an emerging direction in recent years. The exoskeleton system with multimodal information fusion can optimize the training effect and experience. Therefore, a multimodal interaction system of the lower limb exoskeleton for athletic training is developed. Which not only provides a wide variety of standardized training but also realizes a multisensory immersion experience. Firstly, a multi-degree-of-freedom step-by-step action planning method is designed to reproduce training actions based on lower limb movement action points. Second, a multimodal interaction system for the lower limb exoskeleton is proposed to realize the presentation and indication of normative movements in information space through a virtual reality athletic training simulator. The action data set and the lower limb exoskeleton robot are constructed to realize the assistance and correction of basic training in physical space. The system is based on a multimodal interaction execution strategy to give trainers visual, auditory, and tactile multisensory feedback in real-time to achieve an immersive experience that meets safety norms. Finally, the system is evaluated through two experiments on system functionality and user experience. The functional experiment proves that the system can improve the action accuracy rate by 27.62% on average compared with the original traditional training, and has certain generality. The experimental results of user experience show that the system’s function meets the design expectations, and the comfort compared to other indicators needs to be improved.

As the basic unit of laser material interaction, the molten pool experiences transient and localized heat and mass transfer, which have a great influence on the formation of microstructure and macro-defects. Understanding the flow behavior mechanisms of the molten pool and adopting certain control strategies are the keys to obtain high-quality laser material processing parts. With the continuous development of test equipment and technology, experimental study of flow behaviors is moving in the direction of depth and refinement, and up to now, certain achievements have been made. The development and applications of experimental research methods are introduced, and the research progresses of molten pool flow behaviors during laser welding and laser additive manufacturing are summarized. Firstly, the driving forces in the molten pool and their main influencing factors are presented. After that, progresses of visual experimental research on molten pool flow using direct and indirect methods are reviewed and discussed, and the current main control strategies of molten pool flow are summarized. Finally, the further research on the flow behavior mechanism of the molten pool and more efficient strategies of molten pool flow control are prospected.

To meet the demand for ultra-precision manufacturing of the cleavage cavity surface of GaAs based semiconductor lasers, the molecular dynamics simulation and experimental investigation of mechanical cleavage of GaAs are carried out. First, molecular dynamics simulations of scratching on GaAs are conducted to investigate the influence of crystal anisotropy on the surface and subsurface deformation mechanism. Then, a series of verification experiments are carried out. The cleavage plane morphologies are also analyzed. Compared with the [100] direction, the maximum damage width, scratching width and subsurface depth of [110] direction is decreased 5.23 %, 3.98 %, 2.61 % respectively. as the scratching depth increased. A better scratching quality of the GaAs surface can be obtained in the scratches along the [110] direction. In addition, the maximum damage width, scratching width and subsurface depth is increased as the scratching depth increased. The surface and subsurface morphology of GaAs is not significantly affected by scratching speed. The experimental results are in good agreement with the simulation results. For GaAs, the [110] direction is the best cleavage direction.

As one of the important links in the research and development of electromechanical products, cable layout design has always attracted people's eager attention. Based on the in-depth study of cable layout design, the existing cable layout design technology is analyzed according to its development history. Firstly, the traditional cable layout design technology is introduced, but it is gradually eliminated due to defects such as production lag. Then the man-machine interactive cable layout design technology is introduced from two aspects of desktop computer-aided design system and immersive virtual reality technology. Finally, the current research hotspot, that is, cable automatic layout design technology is introduced in detail. On the one hand, it starts with the overall automatic layout design system of cables, and analyzes the independent development system and secondary development system of automatic cable layout. On the other hand, it focuses on four types of automatic path planning algorithms for cables, including blind search algorithms, heuristic search algorithms, intelligent optimization algorithms, and sampling-based path planning algorithms. At the end of the article, the future research direction of cable layout design technology is prospected, which provides reference and support for the study of cable digital layout.

Distributed manufacturing(DM) becomes one of the mainstream manufacturing models, which widely exists in real-world production, including aviation, electronics industries and etc. In DM, there are differences in the number of machines, machine processes, and raw material transportation conditions in every factory, that is, heterogeneity. However, there is no research considering the heterogeneity of factories in the known distributed scheduling literature. Based on this, a multi-objective distributed heterogeneous no-wait flowshop scheduling problem with sequence-dependent setup time(MDHNWFSP-SDST) has been studied. A multi-objective optimization model is established with the objectives of makespan and total tardiness. Based on the MDHNWFSP-SDST feature, a multi-objective discrete artificial bee colony(MODABC) based on pareto optimality is proposed. In MODABC, an improved PWQ heuristic(IPWQ) is designed to initialize the population. IPWQ solves the problems of an order of magnitude and duplicate solutions in PWQ. In the employed bee phase, four neighborhood structures are applied to generate feasible solutions to improve the quality of population. In the onlooker phase, an improved position-based crossover is designed. The superior characteristics of the parents can be retained and the population diversity can be maintained. In the scout phase, a multi-objective local search is embedded to ensure sufficient search of the solution space. Finally, by comparing with other effective multi-objective optimization algorithms, the effectiveness and superiority of the proposed MODABC have been verified.

According to the working principle of the metamorphic industrial robot, its working trajectory model is established. And based on this model, a time optimization trajectory planning method of the metamorphic industrial robot is proposed. This method focuses on the transformation process of robot configuration and transforms the trajectory planning problem into an internal and external nested optimization problem for analysis. The design variables, objective function and constraints of the optimization problem are presented respectively, and the mathematical model of the time optimization trajectory planning problem of the metamorphic industrial robot is obtained. The proposed method is used to study the trajectory planning of the metamorphic palletizing robot developed by our research group. According to its working trajectory model, the mathematical model of the optimization design problem is established. After presenting the calculation method for coefficients of the joint angle interpolation functions, the optimization problem is solved by nested PSO algorithm, and the optimized joint angle functions and theoretical working trajectory are calculated. Compared with the actual working track gained by the experiment, the feasibility of the proposed method is verified. This work provides a reference for the research of motion planning of metamorphic robots.

The uniformity of the stress distribution is an important indicator of the assembly accuracy and assembly performance stability of precision electromechanical products, and uniform stress distribution is one of the goals pursued in the current assembly process of precision electromechanical products. Shape design is an important way to improve the contact stress distribution at the assembly interface. In view of the problems that the initial parameters are difficult to determine in the current stress distribution-based active design method of the interface shape, and that the relevant parameters have a large impact on the calculation efficiency and numerical stability of the optimization process, an adaptive parameter calculation method is proposed to adjust the optimization parameters based on the information of the uniformity of contact stress distribution during the optimization process. Then, a typical single bolted joint structure is used as the design object to carry out the interface shape design, and the results of the adaptive parameter design method and the fixed parameter design method are compared and analyzed after the active design of the assembly interface shape respectively. Results show that the problem of determining the initial parameters in the stress distribution-based active design method of interface shape can be well solved, and the improvement of the optimization effect, the calculation efficiency and the numerical calculation stability of the optimization process can be achieved simultaneously.

The gradual increase in the level of automatic driving means that the power of driving execution is gradually transferred from the driver to the vehicle system, and the responsibilities of the driver also change accordingly. A large number of studies have shown that the attention span of the driver of an autonomous vehicle is closely related to driving safety, and there are differences in the driver state thresholds required for different levels of autonomous driving. This research proposes an long short term memory(LSTM) network driver state prediction model(LSTM-DSDM) that integrates the driver state discrimination mechanism to realize the prediction of the driver's load state and the recognition of the state transition stage, and based on the task requirements of drivers under different levels of automatic driving, a driver's load status monitoring strategy of low-level recognition, high-level prediction is proposed. The experimental results show that the driver's load status monitoring strategy proposed in this study can effectively respond to the driver's load status monitoring needs of different autonomous driving levels. The driver's load state prediction model built in this study has a high recognition rate under the condition of low autopilot level, which can reach more than 90%; under the condition of high autopilot level, the prediction rate of the model can achieve the prediction effect to a certain extent, and it can also be used to study the transition phase of the driver's load state.

A locust-inspired eight-bar jumping robot design method is proposed in order to mimic the straight-line trajectory of the tarsus end of locusts’ hindleg during take-off and jumping stability. The dimensional parameters are optimized based on beetle antennae search algorithm (BAS) and established kinematic model. The trajectory of the equal tarsus end of the optimized eight-bar jumping mechanism is very similar to the one of locusts, close to a straight line. The dynamic model of eight-bar jumping mechanism is established using lagrange equation, and the influence of the centroid location of equivalent body bar on the take-off performance is analyzed. It is found that increasing the mass of the equivalent tarsus bar is helpful to obtain better dynamic stability during take-off. Based on the results of kinematic and dynamic analysis result, a locust-inspired eight-bar jumping robot is designed and fabricated, and the high-speed camera is used to build an experimental platform to record its take-off process. It is verified that the mass of the equivalent tarsus bar has an effective adjustment effect on the dynamic stability of the take-off.

Speed-increasing gears are key parts of many gear transmission systems, for instance, wind turbine gearboxes. Due to the friction force between contacting gear tooth surfaces, the meshing characteristics between speed-increasing and -reducing gear pairs are different, therefore, the knowledge and experience of the former cannot be directly applied to the latter. Based on the most widely used involute spur gears, employing the bending strength calculation standards and Abaqus software, the tooth bending stress under speed-increasing and -reducing cases are analyzed and compared. The comparison shows that, with the same transmission power, the maximum speed-increasing bending stress of the gear will decrease for the dedendum area, and increase for the addendum area by 27.8%, compared with the speed-reducing case. On the contrary, the bending stress of pinion will increase for the dedendum and decrease for the addendum. This work will help to develop a new approach for the design and modification of speed-increasing gears.

The miniature swimmer made of magnetic elastic material can achieve continuous deformation through the external uniform magnetic field to complete the swimming action. Despite visual feedback improving path tracking accuracy, visual closed-loop robot control is prone to recognition errors and tracking failures under complex backgrounds. Aiming at the above problems, firstly, the obstacle information in complex environments is obtained, and the improved RRT* algorithm (IIC-RRT*) is proposed for path planning. In addition, YOLOv5 based on circular smooth label (CSL-YOLOv5) recognition and tracking algorithm is used to update the central position and rotation angle of miniature swimmers in real time under complex conditions. Using this method, the miniature swimmer is controlled via dual closed loop servos with position and angle against a complex obstacle background. According to the experimental results, the proposed path planning algorithm improves the efficiency and smoothness of the path generation process, while the recognition and tracking algorithm improves the recognition stability and accuracy of the miniature swimmer. This work may provide an innovative idea for the precision control of the magnetic miniature swimmer under complex backgrounds.

In order to reduce the vibration excitation caused by the fluctuation of loaded transmission error, an optimization design of linear triangular end relief of double helical gears based on form grinding is proposed. According to the ISO definition of triangular end relief, the helix angle of starting line of modification at the tooth top and tooth root on the rotating projection plane is calculated, the modification curve is designed as linear, and the tooth surface equation of triangular end relief is determined by giving the maximum modification amount. Based on tooth contact analysis(TCA) and loaded tooth contact analysis(LTCA), the loaded transmission error of double helical gears under working load is calculated. The optimization objective was to minimize the fluctuation of the loaded transmission error, and triangular end relief parameters are optimized by genetic algorithm. The objective function is established to minimize the sum of squares of normal deviation of the modified target tooth surface. The helix angle, modulus and pressure angle are taken as design variables, and the tooth top and tooth root modification regions are approximated by genetic algorithm respectively, so as to realize the form grinding of triangular end relief. The results show that the fluctuation of loaded transmission error can be reduced to 36.65% by linear triangular end relief of double helical gears. The theoretical error of form grinding with three-section grinding wheel is controlled within 1 μm, and high accuracy is obtained. The test results of pinion for the double helical gears are controlled within grade 4 accuracy, and the contact patterns rolling test of gear pair is also performed, which verify the effectiveness of the proposed method.

Mechatronic inerter is a new type of inerter device that utilizes circuit networks to achieve high-order mechanical impedances with performance and space advantages. Due to the limited nacelle space of offshore wind turbines, the influence of mechatronic inerter located in a floating platform on the mechanical loads of barge-type offshore wind turbines is studied. According to the characteristics of the DC motor, the torque output of the motor shaft has a linear relationship with the current in the motor circuit. Therefore, for the established mechatronic inerter, focuses on the effects of all circuit networks consisting of a single resistor, capacitor, and inductor on the vibration reduction performance of floating wind turbines. In order to reduce the complexity of the optimization process, a three-degree-of-freedom (3DOF) barge-type offshore wind turbine model is first established, and then the H₂ norm of the input and output transfer functions including the circuit network model is optimized to obtain the optimal parameters of the circuit network. Finally, the optimization results are simulated based on the USA National Renewable Energy Laboratory 5 MW baseline wind turbine model. The simulation results show that the established mechatronic inerter tuned mass damper(MITMD) system can effectively reduce the structural load of the wind turbine system if the working stroke of the device is not considered. Compared with the case where the vibration device in the nacelle, the MITMD system in the platform established can reduce the load on the tower base and the tower top at the same time. The control effect of MITMD comes at the expense of motion displacement, therefore, in practical applications, it is necessary to compromise between the vibration reduction effect and the working stroke of the device.

According to the uncertainty of manufacturing system and the integration optimization problem of workshop layout and scheduling, the integrated optimization of workshop layout and scheduling under uncertain environment is studied, which realized the efficient and orderly operation of manufacturing system by coupling the uncertain factors in shop floor scheduling. The uncertain factors including the workpiece requirements, processing time and equipment failures are selected, which affecting the integrated optimization of layout and scheduling. An uncertainty-oriented workshop layout scheduling integration optimization model is constructed, which taking the minimum total cost, total completion time and maximum robust indexes in the manufacturing process as the optimization objectives. An algorithm called NSGA-III with improved selection operator (NSGA-III-ISO) is designed, which could enhance the global search capability and stability of the algorithm. At the same time, PBI distance is introduced and the method of determining a minimum is improved. The effectiveness of NSGA-III-ISO is verified by DTLZ series test functions and numerical examples. Finally, the integrated model and the improved algorithm are applied to a workshop layout scheduling engineering example, and the results further verified the validity and feasibility of the model and algorithm.

Different from the base translational motion, the base swing motion not only generates additional load in a rotor system, but also changes its damping and stiffness, thereby affecting its stability. Taking the flexible rotor system supported by active magnetic bearings as an example, the stability of the rotor system under the base swing motion was studied. The dynamic model was firstly established by the finite element method. Then the stability of the rotor system under constant swing base motion was derived with Routh-Hurwitz and analyzed using the root locus. After that, based on Floquet theory, the influence of sinusoidal swing base motion on the system stability was studied, and the stability boundary was obtained, which was verified by the response of the rotor system. Finally, the effect of the PID controller parameters on the system stability under the base swing motion was studied. For the sinusoidal swing motion condition, the phase compensator was proposed to compensate the system stability. The results show that the system stability is related to the motion amplitude under the constant swing base motion, and related to both the amplitude and frequency under the sinusoidal swing motion. Reasonable selecting the parameters of the PID controller will improve the system stability. The phase compensator has a good effect on the system stability under the sinusoidal base swing motion.

Since the laser additive manufacturing equipment has multi-dimensional information, multi-process, multi-function,multi-objects and other human-computer interaction characteristics, which leads to low interaction efficiency, poor comfort and safety,and directly affects the stability of the forming quality of the parts. Based on this, a human-machine interface layout optimization method of laser additive manufacturing equipment based on reachable region is proposed. According to the comfort of both hands vertical reachable domain, the reachable domain level of human-computer interface is divided, and the human-computer interface layout optimization model of laser additive manufacturing equipment based on reachable domain is constructed. Aiming at the problem of solving the multi-decision variable interface layout model based on domain model, a hybrid intelligent solution algorithm based on wolf pack-particle swarm optimization algorithm is proposed. The running siege behavior mechanism of wolf pack algorithm is introduced into particle swarm optimization algorithm to solve the problem that the calculation results of particle swarm optimization algorithm are easy to fall into local optimal solution due to low population diversity. Finally, taking LDM4030 laser additive manufacturing equipment as an example, the human-machine interface layout is optimized, and the ergonomic simulation and eye movement experiment are carried out. The results show that the optimized human-machine interface layout is superior to the original equipment design in terms of comfort, safety and interface rationality, which validates the effectiveness and feasibility of the model.