A health state assessment method combining deep residual shrinkage network (DRSN) and adversarial domain adaptation (ADA) was proposed to address the problems of vibration signal noise interference and inconsistent data distribution under different working conditions in the remaining useful life (RUL) prediction of rolling bearings, so as to improve the accuracy and generalization ability of RUL prediction.

Firstly, a health state assessment model combining deep residual shrinkage network and adversarial domain adaptation was constructed. The performance of DRSN in avoiding noise in vibration signals and adaptively extracting bearing degradation features was utilized to build the health indicator curve. Then, ADA was used to align the distribution of health indicators between the test set and the training set, so as to eliminate the difference in data distribution under different working conditions. Finally, the health indicators output by the DRSN-ADA model were input into the convolutional long short-term memory (ConvLSTM) network model, and the accurate RUL prediction of rolling bearings was realized.

In the XJTU-SY dataset and engineering tests, the health indicators constructed by DRSN-ADA are superior to the comparison methods in monotonicity, robustness and correlation, with their mean values reaching 0.61, 0.97 and 0.98 respectively. The mean values of mean squared error (MSE) and mean absolute error (MAE) of the RUL prediction results are 2.52% and 2.19% respectively, and the average score is 0.86, which is significantly better than the DRN, principal component analysis and root mean square (RMS) methods. These results verify the effectiveness of the proposed method in noise suppression and cross-working condition prediction.

To accurately and efficiently analyze the magnetic and dynamic characteristics of multishaft double ring-plate magnetic gears (MDRMGs), improve the working conditions of CPMG arm bearings, and extend their service life, a multishaft double-ring magnetic gear transmission structure was designed by combining magnetic gears with mechanical ring-plate gears.

A magnetic field unit classification method was proposed, and then a mathematical model for air-gap magnetic field and static torque was established, which was efficient and took the end leakage magnetic effect into account. Meanwhile, based on the Riccati transfer matrix method, a dynamic model of the eccentric shaft rotor system of MDRMG was constructed.

A comparison between the magnetic field unit classification method and the finite element method shows that the results of magnetic flux density and magnetic force obtained by the two methods are highly consistent, but the calculation time of the magnetic field unit classification method is shorter. The analysis also reveals that changes in the ring-plate spacing affect the classification calculation of magnetic field units and the lumped parameters in the dynamic model, the static magnetic torque of MDRMG increases with the increase of ring-plate spacing, while the critical speed of the eccentric shaft decreases as the ring-plate spacing increases. The magnetic field unit classification method can efficiently and accurately analyze the air-gap magnetic field and torque characteristics of MDRMG. In addition, the ring-plate spacing has a certain impact on the magnetic field and dynamic performance of MDRMGs.

Existing research on flexible hinges corresponds to complex expressions for flexibility and rotational accuracy calculations. To address this issue, a new type of catenary flexure hinge was designed, and a method for establishing the hinge’s compliance and rotational accuracy model by approximating arc segments with straight-line segments was proposed.

Firstly, by defining the flexure hinge as a series combination of tapered and expanded sections, the curve in the tapered segment was divided into several arc segments, and the curve segments were approximated with straight segments. Based on the Castigliano’s second theorem, a method by calculating the flexibility of the tapered section and then establishing the hinge flexibility and rotational accuracy model through matrix operations was established. Secondly, using specific examples, the derived formula, literature formulas, and the finite element method were employed for calculations. When the curve segment was finely divided, the calculation results align well, thereby verifying the formula’s correctness. Thirdly, the influence of structural parameters on the flexibility, rotation accuracy, and flexibility-accuracy ratio of catenary flexure hinges was analyzed. Finally, the bending flexibility and flexibility-accuracy ratio of the catenary, conic, and their hybrid hinges were analyzed with the same structural parameters.

The results show that a single parameter has a negative correlation with flexibility and rotation accuracy of the catenary hinge, and reducing the minimum thickness is the best way to improve flexibility. Under the same structural parameters, the flexibility and flexibility-accuracy ratio of the catenary hinge is between parabolic and circular shapes. Choosing a hybrid hinge with a section of high flexibility for the tapered section and a section of low flexibility for the expanded section allows for a balance between flexibility and motion accuracy.The greater the difference in flexibility, the better the flexibility-accuracy ratio.

To address the problem that pure rolling bevel gears are prone to angular velocity mutation, vibration, and noise excitation under the influence of mounting errors, a tooth surface design method with low sensitivity to mounting errors was proposed.

Firstly, based on the influence of installation errors on angular velocity, the transmission error curve was preset as a parabolic type. Secondly, the theoretical tooth surface of the pinion was modified using the preset transmission error curve to establish a mathematical model of the target tooth surface. Finally, a 3D solid model of the modified bevel gear was constructed, and tooth contact analysis was performed.

The results show that the derived transmission error curve is consistent with the preset curve, validating the effectiveness of the modification. The actual meshing points of the optimized tooth surface deviate from the edges, and the overall contact area centers on the tooth surface, effectively avoiding edge contact and stress concentration.

Aiming at the problems of unbalanced magnetic pull (UMP) and low structural strength of high-speed rotor in the operation of permanent magnet assisted magnetic gear, relevant research was conducted.

Firstly, the phase tuning method was used to study the influence of different transmission ratios on the UMP. Then, according to the structural characteristics for the high-speed permanent magnet rotor of the magnetic gear, the analytical solution of the rotor strength was obtained by using the equivalent mass ring method. Finally, taking reducing the maximum stress and ensuring a certain output torque as the optimization objectives, the multi-objective optimization was performed on the relevant parameters of the magnetic isolation bridge and magnetic barrier.

The analysis results indicate that a transmission ratio where the maximum common divisor of the number of magnetic blocks and the number of poles of the low-speed rotor G_{\mathrm{C}\mathrm{D}}=\mathrm{2} can effectively decrease UMP. The relative error between the analytical solution of the maximum stress obtained from the equivalent mass ring method and the result of finite element simulation is less than or equal to 1%, validating the accuracy of the analytical method. Through the optimized design, the maximum stress on the rotor is significantly reduced.

To address the core problems of traditional magnetic tile-type magnetic wheels in the application of boiler wall-climbing robots, such as unclear magnetic field distribution, redundant safety factors of empirical formulas, low magnet utilization rate, and excessive weight, a magnetic tile arrangement scheme was identified with better magnetic attraction in the N-S alternating arrangement under the same volume and mass constraints. The differences in magnetic field distribution and magnetic attraction force magnitude when the magnetic wheel pressed against three versus two boiler water-cooled wall tubes were also clarified.

Taking a water-cooled wall inspection robot for thermal power plant boilers as an example, four magnetic wheel models with the same external dimensions but different magnet arrangement modes were established. Using Maxwell software, simulation analysis of the magnetic attraction force of these four magnetic wheels with different structures was conducted at a distance of 2 mm from the water-cooled wall tubes.

The results show that the adsorption force of the magnetic wheel on the water-cooled wall tube is 5%-20% greater when adsorbed at the joint of the magnetic tiles than at the middle of the magnetic tiles. When adsorbed at the middle of the magnetic tiles, regardless of whether the magnetic wheel presses against three or two wall tubes, the magnetic wheel with the 4-magnetic-tile arrangement exhibits the maximum attraction. Additionally, the adsorption force when pressing against three water-cooled wall tubes is approximately 10%-20% greater than that when pressing against two tubes.

The risks of losing magnetism upon power-off and high energy consumption are suffered by traditional electromagnetic grippers. And the problem of lacking the active magnetic force regulation function is still faced by permanent magnegrippers. A lightweight magnetic pole rotation gripper with optimized methodology was developed.

Based on the magnetic flux continuity principle and magnetic field superposition effect, the optimal design strategy integrating theoretical analysis, numerical simulation, and test verification was established through coordinated regulation of three key parameters: magnetic pole rotation angle, geometric dimensions, and air gap distance. The global optimal solution of the magnetic pole structural parameters was finally obtained.

Both simulation and test results demonstrate that the optimized gripper achieves superior magnetic adhesion performance per unit mass compared to existing models. The proposed device exhibits distinctive advantages including compact structure, simplified control mechanism, and quasi-linear control characteristics, showing broad application potential in material handling operations.

To address the issues of crawling and poor motion stability in low-speed and heavy-duty conveyor chain transmissions, a dynamic model of the above conveyor chain transmissions was established based on multi-body dynamic theory, and the research on dynamic characteristics was carried out, aiming to provide guidance for enhancing the stability of such conveyor chain transmission systems.

By considering the structural characteristics of low-speed and heavy-duty conveyor chain transmission systems and the effects of conveying loads, the mechanical properties of the conveyor chain nodes were simulated using Hooke’s law, and a dynamic model with 107 degrees of freedom of the conveyor chain was constructed. The modal superposition method was adopted to solve the dynamic model, the dynamic characteristics of the low-speed and heavy-load conveyor chain were obtained, and the influence laws of the slack side sag and the tight side friction force of the conveyor chain on the transmission speed variation were studied.

The results show that reducing the slack side sag and decreasing the friction coefficient between the conveyor and the guide rail can effectively reduce the occurrence of the crawling phenomenon in conveyor chain transmission and improve the motion stability of the conveyor chain transmission systems.

Contact fatigue failure is the primary failure mode for gears operating under extreme conditions such as high speed, heavy duty, and high temperature. It has become a significant technical bottleneck limiting the development of aviation equipment toward higher reliability, longer life, and higher power density. Predicting contact fatigue life is now a critical focus of both engineering and academic research. The quantitative prediction research of gear contact fatigue life was carried out.

Firstly, over 400 rolling contact fatigue specimens made from 9310 aviation gear steel were prepared and subjected to more than 5 000 hours of fatigue testing. The investigation examined the effects of service conditions, such as contact stress and slip rate, as well as surface integrity states created by over ten processes including carburizing grinding, shot peening, fine particle peening, and rolling finishing, on rolling contact fatigue life. Secondly, the Lundberg-Palmgren （LP） theory was modified using multiple linear regression methods, resulting in an LP rolling contact fatigue life prediction formula based on service conditions and surface integrity parameters.

It is found that increasing the slip rate from 10% to 30% reduces the fatigue life at a contact stress of 3 000 MPa by 52.6%, from 2.28×10⁶ r to 1.08×10⁶ r. Additionally, when the contact stress is 3 000 MPa and the slip rate is 20%, dual shot peening significantly improves fatigue life, increasing it by 113.8% from 1.52×10⁶ r in the carburizing grinding state to 3.25×10⁶ r. The derived LP contact fatigue life prediction formula, considering service conditions and surface integrity, demonstrates an error margin within twice dispersion band, thus meeting engineering application requirements.

To solve the problems of fixed damping force and poor pseudo-humanity of traditional lower limb prosthetic knee joints, a magnetorheological damper was designed to meet the vibration reduction requirements of the lower limb prosthetic knee joint.

Through theoretical calculation, the maximum damping forces required for the knee joint swing phase during flat walking and flat running were obtained, which were 179.6 N and 1 377 N respectively. In order to adapt to the motion state of the lower limb prosthesis, a vibration absorber was designed to meet the damping force required by the knee joint swing phase. Through numerical simulation and test research, the influence of external disturbed magnetic field and temperature rise effect on the dynamics characteristics of magnetorheological damper were analyzed. The test of influence of external disturbance magnetic field and temperature rise effect on the dynamics characteristic of the lower limb prosthetic knee joint was conducted by using the lower limb prosthetic knee joint simulator.

The results show that the output damping force of the magnetorheological damper increases with the increasing magnetic flux density of the external disturbed magnetic field. Under the same conditions, the output damping force of the magnetorheological damper decreases with the rising temperature of the magnetorheological fluid. In the early stage of knee joint swing and the first half of its middle stage, with the increase of the magnetic flux density of external disturbed magnetic field, the hysteresis of knee joint movement increases, and the angle error increases. When the magnetic flux density of external disturbed magnetic field is 10, 20 and 30 mT respectively, the maximum bending angle of the lower limb prosthetic knee joint is 59.0°, 57.8° and 55.7° respectively, and the maximum angle error reaches 3.0°, 6.8° and 11.9° respectively. As the rise of the temperature of the magnetorheological fluid, the hysteresis of knee joint movement increases, and the angle error increases. When the temperature of the damper rises to 30, 35 and 40 ℃ respectively, the maximum bending angle of the lower limb prosthetic knee joint is 57.1°, 54.0° and 49.8° respectively, and the maximum angle error reaches 1.9°, 5.1° and 9.8° respectively. These conclusions provide a basis for the design and optimization of the lower limb prosthetic knee joint based on the magnetorheological damper.