One of the core contents of the civil aircraft structure maintenance outline is determining the maintenance interval of structure. The utilization ratio has a great influence on the rationality of the maintenance interval. Based on the structure of civil aircraft under environmental damage，a matching model of maintenance interval and aircraft utilization ratio civil aircraft structure was established by analyzing the sensitivity of indicators that affect the environmental damage of metal structures under different utilization ratios. In this model, the combined-weighting method combined the rank-correlation analysis with the attribute-importance was applied to evaluate the combined weight of the indicators affecting the environmental damage of metal structures under different utilization ratios, and the total level of environmental damage of metal structures was determined. The maintenance interval of civil aircraft structure under different utilization ratios was determined based on the damage grade-maintenance interval regression equation. Finally, the grey correlation analysis method was used to verify the correlation between the evaluated value and ideal value of each factor under different utilization ratios. Taking the maintenance interval determination of the upper wall inner surface of the central box section in a certain aircraft as an example, the proposed model was verified and analyzed. The maintenance interval obtained by the model was inferior to the maintenance review board report (MRBR) regulations. In view of the minimum engineering requirements specified in this document, it was determined that the maintenance interval met the requirements, which proved the validity of the model. The research results indicate that the matching model of maintenance interval and utilization ratio of civil aircraft structure has strong applicability, and it can effectively remedy the problem of inadequate utilization ratio consideration in the maintenance interval of domestic aircraft structural maintenance outline, and has high engineering application value.

With the continuous development of oil and gas exploitation to deep hard formation, the conventional PDC bit has some problems such as slow rock breaking speed, easy damage and low efficiency, and it is difficult to meet the requirements of drilling faster and more effective. PDC cutting tooth structure is a key factor to improve the rock breaking efficiency of PDC bit. Hence, it is of great significance to design cutting teeth with different structures for different rock formations. A new type of PDC tooth with non-planar structure was designed for deep hard formation drilling. The new PDC tooth had a ridged cutting structure and could break the rocks in layers. In order to study the rock breaking mechanism and various performances of this new PDC tooth, a method combining finite element simulation and experiment was carried out to study the rock breaking process of new PDC tooth and conventional PDC teeth. The results showed that the new PDC tooth had smaller average and fluctuating cutting forces in the horizontal, lateral and longitudinal directions, so the new PDC tooth had more stable cutting ability. The new PDC tooth was less likely to suffer severe wear and impact breakage, and had longer service life and higher rock breaking efficiency. The research results can provide a theoretical basis for the development and promotion of the new PDC tooth, and provide support for the PDC bit to achieve high speed and efficiency in the hard formation drilling process.

In order to effectively control low-frequency broadband noise, the sound lining is widely used due to its simple structure. However, the traditional sound lining can only eliminate the noise of a fixed frequency, that is, when the frequency of the environmental noise changes, the muffling performance is significantly reduced. To this end, this paper proposed an adaptive muffler system, which used the principle of piezoelectric sound lining to transmit and control data programs through LabVIEW serial communication technology, and drove the piezoelectric sound lining to adaptively control according to the variation of different noise frequencies. The signal, by adjusting the output voltage of the power supply, changed the volume of the piezoelectric sound lining resonant cavity, thereby timely and effectively adjusting muffling frequency of the piezoelectric sound lining, and broadening the noise anechoic band of the sound lining. The research showed that when the volume of the piezoelectric sound lining resonant cavity was reduced, the muffling frequency band was shifted to the low frequency direction, and vice versa. The output voltage was -100-200 V, and the system could always achieve the best muffling effect in the environment where the main noise frequency was 1364-1420 Hz, and achieved adaptive noise elimination. Therefore, applying a direct-current power supply to the sound lining could adjust the muffling frequency, so that the muffling frequency band of the sound lining shifted with the change of the noise frequency, widening the muffling frequency range of the sound lining. The designed muffler system can realize the adaptive control of noise, and provide a reference for the active control and optimization of sound liner.

The oil film thickness is an important parameter that reflects the operating status of thrust bearings. The real-time online monitoring of the oil film thickness is helpful to achieve stable operation of thrust bearings. Taking the thrust bearing of a large hydraulic generating unit as an example, combining the Reynolds equation and the oil film thickness equation of its lubricating fluid, the finite difference method was used to analyze the change law of the oil film thickness and pressure distribution of the thrust bearing under different loads and different rotational speeds, and a real-time online monitoring method of oil film thickness was designed. The theoretical analysis results showed that when the rotational speed was constant, the oil film thickness of the thrust bearing first increased with the increase of the load, and after reaching the peak value, the oil film thickness decreased with the increase of the load. When the load was constant, the oil film thickness increased with the increase of the rotational speed. The theoretical analysis conclusion was in complete agreement with the online monitoring data of oil film thickness for the large hydraulic generating unit. The reliability of the proposed online monitoring method of oil film thickness is verified, which provides a scientific basis for diagnosing the operating state of the thrust bearing.

The vibrator is the key device for the excitation of the seismic signal of vibroseis. Long-term wide and high-frequency seismic wave excitation causes cracks or even fatigue failure in the welded part of the vibrator baseplate, which will not only greatly reduce the working life of the baseplate, but also seriously affect the source signal quality. Therefore, the micromorphology of the baseplate cracking fracture was analyzed. The damage characteristics and crack propagation law of the fatigue damage area of the baseplate were grasped, which revealed the damage mechanism of the baseplate cracking fracture. According to the fatigue damage mode and characteristics of the baseplate, the "three-point bending" fatigue test of the baseplate was carried out, and the S-N curve of the baseplate was fitted. The fatigue life of the baseplate was predicted, and compared with the fatigue life calculated by the fracture mechanics method. The results showed that the S-N curve method modified by fatigue test parameters was more accurate than the fracture mechanics method, and it could accurately predict the working life of the seismic vibrator baseplate. The research results provide scientific theoretical support for prolonging the fatigue life of seismic vibrator baseplate and enhancing its reliability, which will significantly enhance the research and development level and international competitiveness of China's oil and gas exploration technology as well as the related engineering equipment.

In view of the problems that the traditional manufacturing and processing equipment is not closely related to the data information during the production and the equipment maintenance greatly depends on the human experience, a new intelligent method for the equipment is proposed. Firstly, the digital twin that can reflect the true state of manufacturing and processing equipment was established in the information layer. Secondly, based on the past big data of processing，the behaviour of the process was modelled and the deep learning and training was performed by the digital twin. The state of manufacturing and processing equipment at the next moment was predicted by the trained artificial neural network based on the collected real-time data，so that the manufacturing and processing equipment could realize the deep integration of data in the physical layer and the information layer, and had the ability of self-awareness and self-prediction to realize the intelligence. Finally, taking the intelligent implementation process of extrusion structure system of slurry microfluidic extrusion forming equipment as an example to verify the feasibility of the proposed method. The example results showed that the intelligent method of the equipment could effectively monitor and predict the operating state of the extrusion structure system, which provides effective data information for the subsequent improvement of the extrusion molding accuracy. Research shows that the digital twin and deep learning technology can enhance the intelligence of manufacturing and processing equipment, and can provide theoretical support for the development of intelligent manufacturing in the future.

Aiming at the problem that the control performance of the manipulator is easily affected in the complex underwater working environment, but the traditional control method is not effective, an intelligent controller based on the fuzzy RBF (radial basis function) neural network method is proposed to control the underwater manipulator precisely and stably. In the water disturbance environment, the manipulator was usually affected by the additional mass, water resistance and buoyancy. The Lagrange method and Morison equation were used to establish a dynamics model of the two-bar manipulator, which included those hydrodynamic terms mentioned above. By using the fuzzy RBF neural network, the hydrodynamics uncertainties in the dynamics equation of the underwater manipulator were identified overall and fitted. With the advantages of heuristic search of fuzzy system and high reasoning speed of RBF neural network, the control performance of underwater manipulator system had better precision and strong adaptability. Considering the hydrodynamic terms, the stability of the underwater manipulator system was proved by using Lyapunov stability theory. Finally, the simulation experiment of trajectory tracking control for a two-bar manipulator was carried out by using MATLAB, and the control effect of fuzzy RBF neural network, conventional RBF neural network identification method and traditional fuzzy control method was compared. The simulation results showed that compared with the conventional RBF neural network identification method, under the control of fuzzy RBF neural network, the response time and relative error of joint 1 of the two-bar manipulator was reduced by 91% and 88%, the response time and relative error of joint 2 was reduced by 92% and 77%; compared with the traditional fuzzy control method, the relative error of joint 1 and joint 2 was reduced by 65% and 10%. The research results show that the control effect of fuzzy RBF neural network is better than that of conventional RBF neural network identification method and traditional fuzzy control, which can provides a high precision and effective control method for the underwater manipulator control.

In order to improve the safety and stability of bearing parts of radiation well horizontal drilling rig, the design of experiment (DOE) and finite element simulation technology were used to optimize the bearing parts. Orthogonal test method and ANSYS Workbench finite element statics simulation were used to optimize the layout of reinforcing ribs of the bearing system consisting of rotary platform, vertical bracket and transverse bracket. In this way, the optimal layout of reinforcing ribs for the bearing system was obtained. On this basis, the response surface optimization method based on the DOE was used to optimize the platform thickness, rib height and rib thickness of rotary platform, which further reduced the maximum equivalent stress, maximum deformation and mass of the rotary platform, and improved the safety and stability of the bearing system. The results showed that the optimal layout of reinforing ribs for the bearing system was as follow: the rotary platform used a vertical and horizontal rib, the vertical support used an X-shaped rib, and the horizontal support used a V-shaped rib. The optimal parameter combination of the rotary platform was that: the platform thickness was 11.2 mm, the height rib was 31.9 mm, and the rib thickness was 12.3 mm. Through the integration of DOE and finite element simulation technology, the optimization design of bearing parts of horizontal drilling rig is carried out, which provides a reference for the design of the solid prototype of horizontal drilling rig.

In order to discuss the influence of displacement boundary conditions on the topology optimization for reinforced concrete deep beams, and provide more effective mechanical theoretical basis for the design of deep beams, four reinforced concrete deep beams with openings in both side and different bearing constraints, four reinforced concrete deep beams with pin supports at both ends and different opening conditions and three continuous deep beams with different bearing constraints and opening conditions were separately topological optimized and the different topological solutions were compared, which was based on the secondary development of parametric design languages in the finite elements analysis software of ANSYS and the evolutionary topology optimization algorithm with intuitive and effective ability of topological evolution. The results indicated that the topological solutions of deep beams applied concentrated force were approximate to truss structures. The raising in degree of bearing constraint might increase the load-transfer path and make the load-transfer more direct. When the deep beam had to be set up openings for engineering reasons or function requirements, the farther the location of the opening from the original force transmission path, the more favorable the internal force transmission of the structure. The key distinction of topological solutions of continuous deep beams and single-span ones was embodied by the tie-bar in the top of the beam at the middle support, since the tie-bar could improve the integral stiffness of structures. Therefore, in the engineering design, for the reinforced concrete deep beams with different displacement boundaries, different design schemes can be adopted according to the differences of their topological solutions and the corresponding mechanisms that cause these differences, including support constraints, opening conditions and reinforcement methods. Research results can provide mechanical theoretical basis for the design of complex stressed members such as deep beams..

In the metal cutting process, the generation and dissipation of energy always exists, which directly affects the deformation of processed material and processing quality. The cemented carbide turning tool was researched through the combination of theoretical calculation, cutting test and simulation. The generation, transmission and dissipation of cutting energy of the improved cemented carbide micro-groove turning tool and the original turning tool in the process of cutting high-strength alloy steel were mainly studied, and the cooling mechanism of the micro-groove turning tool was revealed from the view of energy. It was found that the energy consumption of the cemented carbide micro-groove turning tool was lower than that of the original turning tool. The reduction of the unit total input energy, unit friction energy and unit shear energy was 5.1%, 10.4% and 3.4%, respectively. From the view of energy dissipation, the average temperature of the cutting area of the cemented carbide micro-groove turning tool was lower than that of the original turning tool, and the theoretical and experimental results were in good agreement with the simulation results. The conclusion provides theoretical support for the later research of the cemented carbide micro-groove turning tool, and also provides an effective reference for the comparative study of cutting energy in other similar metal cutting processes.

To verify the adaptability and stability of the 7-DOF (7 degree-of-free) dual-arm cooperative robot operation in the complex environment, and to improve the working efficiency and coordination performance, a numerical analysis method combining MATLAB and ADAMS was proposed to analyze and calculate the space operation mode of 7-DOF dual-arm cooperative robot. Firstly, the three-dimensional model of 7-DOF dual-arm cooperative robot was established in Solidworks. Secondly, the kinematics inverse solution of 7-DOF manipulator was calculated by using the numerical analysis method combining MATLAB and ADAMS. Finally, the control method based on virtual dynamics model was used to simulate the 7-DOF dual-arm cooperative robot clamping and moving operation in complex environment, the kinematics inverse solution was verified, and the adaptability and stability of the 7-DOF dual-arm cooperative robot were analyzed. The simulation results showed that the X-direction error, Y-direction error, and Z-direction error of the dual-arm reaching the target position were 0.6, 0.5 and 0.9 mm, respectively. In addition, the average error of the dual-arm reaching the goal position was 0.5 mm, and the success rate of dual-arm co-grasping target was 99.1%. It is suggested that the kinematics inverse solution of 7-DOF manipulator can satisfy the expectation, and the adaptability and stability of the 7-DOF dual-arm cooperative robot operation in the complex environment have increased.

The brake works unsteadily and causes vibration and noise, because of the complex and changeable working environment, and the temperature change of drum brake has a great influence on the brake instability. It is of practical engineering significance to study the influence factors and time-varying characteristics of braking instability. Based on the four-degree-of-freedom contact model of drum brake, the model of brake drum and brake shoe assembly of drum brake and the contact model of friction brake were established respectively in Hypermesh and ABAQUS and tested and verified. The influence of brake drum temperature on brake stress was studied through the dynamic analysis of thermal-mechanical coupling. The effects of elastic modulus and thermal expansion coefficient on the time-varying characteristics of braking instability of drum brake were analyzed. The results showed that the braking instability was caused by friction coupling. During the braking process, the temperature and stress of the brake drum interacted with each other and rose rapidly first and then fell slowly. The time-varying characteristics of braking instability of drum brake were mainly reflected in the number of unstable modes and the change of tendency of instability (TOI) value. The braking temperature change led to the change of elastic modulus, which caused a slight change in the number of unstable modes and the TOI value. The elastic modulus had little influence on the time-varying characteristics of braking instability of drum brake. The braking temperature change led to the change of the thermal expansion coefficient, which caused the number of unstable modes and TOI value to decrease at first and then slightly increase, and the thermal expansion coefficient had a great influence on the time-varying characteristics of braking instability of drum brake. The results of this study have some guiding significance for improving the braking sound quality of automobile.

The conventional cutterhead rotational speed control strategy of TBM (tunnel boring machine) designed for the single driving source of variable frequency motor causes serious bias load in the hybrid cutterhead mechanical transmission system, which decreases the component’s lifespan and TBM availability. Considering the constraints in the rotational speed and the parameter drift in the excavation process, an adaptive control strategy was used to design a rotational speed control system based on driving source torque control for the the electro-hydraulic hybrid cutterhead driving system (EHDS). The model of the gear-ring transmission system was established. The parametric uncertainty in the system was considered. The MATLAB/AMESim co-simulations results showed that the proposed adaptive control system could compensate the parameter drift, realized the load torque distribution between different types of driving sources while realizing the precise control of the cutterhead rotational speed. The bias load phenomena had been eliminated by the proposed adaptive control system. EHDS can effectively improve its geological adaptability and play an important role in improving the driving speed by complementing the driving characteristics of hydraulic motor and variable frequency motor.

The rapid upgrade of marine equipment makes the sea hoisting widely used, but the hoisting equipment is susceptible to wind and waves, which reduces the control accuracy of system. To improve the control accuracy of marine hoisting system，an adaptive backstepping compensation strategy for wave heave based on disturbance observer is proposed. Taking the wave heave compensation system as the research object, the tracks of ship heave motion and the nonlinear model of the electro-hydraulic lifting system in the third-level sea condition were deduced. Ship heave motion was simulated on wave simulation platform, and the nonlinear error of the electro-hydraulic lifting system was suppressed by an adaptive backstepping compensation strategy based on the disturbance observer. The stability of the adaptive backstepping compensation strategy was proved by Lyapunov theory, and the controller performance was verified by simulation and test. Test results showed that the adaptive backstepping compensation strategy based on the disturbance observer had higher control accuracy than the traditional PID (proportion integration differentiation) controller. Aiming at the control system of marine hoisting equipment, the influence of external disturbance and system nonlinear disturbance on the controller can be effectively restrained by the adaptive backstepping compensation strategy based on the disturbance observer, so that the position compensation accuracy of heave motion of marine hoisting equipment can be increased.

In order to better assist stroke patients in early rehabilitation, a rotational orthosis for walking with arm swing is developed based on the theory of interlimb neural coupling. Firstly, according to the theory of rehabilitation medicine, the structures of upper and lower limb rehabilitation devices were designed, and the mechanical structures of the ankle joint rehabilitation device and the lower limb length adjusting device were introduced in detail. Then, the position closed-loop control system was established by the pole-placement approach to realize the passive linkage motion of the rotational orthosis for walking with arm swing. Finally, four able-bodied participants were recruited to test the orthosis. The experimental results showed that the rotational orthosis for walking with arm swing achieved synchronous passive motion of joints of upper and lower limbs, and every joint tracked the target trajectory well with the error not exceed 1.50°. The orthosis achieved linkage motion of the bilateral shoulder, hip, knee and ankle joints, which was believed to be efficient for the early gait rehabilitation for stroke patients.

Variable preload spindle can meet the requirements of both thermal and dynamic characteristics of high-speed spindle in the whole cutting speed range, and has become an important development direction of the intelligent spindle. In order to make up for the deficiencies in the design and selection of variable preload spindle based on piezoelectric actuator (PEA), a variable preload spindle structure based on PEA with the advantages of high resolution, quick response， little influence on cutting stiffness and compact structure was presented. The stiffness models of angular contact ball bearing under static and running conditions were established. On this basis, the equivalent mechanical model of the variable preload spindle based on PEA was established and the change regulation of preload mechanism load stiffness with preload displacement was obtained. Furthermore, the actual input-output model of the preload mechanism was established by analyzing the output characteristics of PEA, and the influence of initial preload and the stiffness of PEA on the control range for preload was analyzed, and then, the design and selection principles of preload mechanism was proposed. Finally，a variable preload spindle test rig based on PEA was designed by applying the proposed spindle structure and the design and selection principles. Test results showed that the preload control resolution was 1.5 N and the step response time was 300 ms，and the accuracy of the actual input-output model of the preload mechanism was verified. The temperature control test results showed that the spindle test rig had great temperature control ability. The study results can provide guidance for the design of variable preload spindle based on PEA in engineering.