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 solve the problem of no direct mechanical or hydraulic connection between the brake actuator and the brake pedal in an electronic mechanical braking system, leading to no feedback of road feel, a brake pedal feeling simulator was proposed based on magnetorheological dampers.

Ansys/Maxwell and Matlab/Simulink were used as the platform. The structural design of the sinking brake pedal feeling simulator, the structural design of magnetorheological damper, magnetic circuit analysis and electromagnetic simulation were carried out respectively, and the simulation analysis of traditional proportional-integral-derivative (PID) and fuzzy adaptive PID control under different working conditions of the whole system was compared.

The simulation results show that the brake pedal feeling simulator can track the characteristic curve of the traditional pedal well under different working conditions and has wide applicability. Compared with the traditional PID control effect, the fuzzy adaptive PID control has higher control precision and smaller control error, and has good application prospects.

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 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.

A novel two-stage compound amplification mechanism design scheme was proposed to address the friction and clearance issues inherent in traditional revolute pairs within the large stroke design of micro-displacement platforms. The aim was to achieve high-precision and significant stroke displacement amplification through structural innovation.

Utilizing the theory of material mechanics, a static model was established. A two-stage compound amplification structure that integrated a flexible hinge lever amplification mechanism with a bridge amplification mechanism was employed. Piezoelectric ceramics served as the driving source, and a parameter optimization model was developed using Matlab software. The impact of key structural parameters on both the amplification ratio and input stiffness was systematically analyzed to identify the optimal parameter combination. The optimized structure underwent validation through multi-physical field simulation via finite element analysis.

Following optimization, the mechanism attains an impressive displacement amplification ratio of 13.1 times, with its natural frequency reaching 92.2 Hz. The maximum discrepancies between theoretical calculations and simulation results of the amplification ratio and natural frequency are recorded at 2.4% and 3.5%, respectively, thereby demonstrating the feasibility of this structural design.

In order to improve the torque to volume ratio of magnetorheological （MR） brakes, a MR brake with internal and external fluid flow channels was developed.

Firstly, the structure and working principle of the MR brake with internal and external fluid flow channels were introduced, and the mathematical model of the braking torque was established based on Bingham constitutive model. Secondly, in order to obtain the optimal structure size of the MR brake, structural optimization design was carried out based on the non-dominated sorting genetic algorithm (NSGA-Ⅱ). Finally, the prototype of MR brake was fabricated, the torque performance test system was built, and the braking performance test was conducted for the MR brake.

There are both internal and external fluid flow channels in the MR brake. Six effective damping gaps are obtained by reasonable setting of magnetic conductive and magnetic isolating materials in the MR brake, so that it can produce excellent torque performance under the premise of the same size. The theoretical calculation results show that the braking torque and the adjustable range after optimization are increased by 30.23% and 16.58% respectively compared with those before optimization. Test results show that at the applied current of 2.0 A, the maximum braking torque is 44.28 N·m, and the dynamic adjustable range is 17.8. The relative errors of the braking torque and the dynamic adjustable range between the test values and the theoretical calculation values are 6.5% and 16.1% respectively, which verifies the rationality of the design.

Alternating magnetic fields induce vibrations in mechanical components, thereby generating noise. Fluctuations in electromagnetic excitation forces and electromagnetic torque are the primary causes of electromagnetic vibration noise. To analyze the generation mechanisms and functional patterns of these fluctuations, an electromagnetic vibration noise analysis was conducted on a slotted disk-type asynchronous magnetic coupler with 9 pole pairs and 16 slots.

Firstly, theoretical formulas for air-gap magnetic flux density and electromagnetic excitation force were derived using the magnetic scalar potential permeance method and Maxwell stress tensor method. Combined with finite element simulation, the harmonic order amplitudes of the Fourier decomposition of air-gap magnetic flux density and electromagnetic excitation force were obtained. Secondly, based on the energy method, an expression for cogging torque was derived. Finite element simulation was employed to determine the cogging torque and electromagnetic torque fluctuations generated during the operation of the magnetic coupler. Thirdly, an electromagnetics-structural-acoustic multi-physics coupling model was established. Using the modal superposition method, vibration acceleration and displacement produced during stable operation of the magnetic coupler were obtained, and the characteristics of its electromagnetic noise were analyzed. Finally, a test platform for the magnetic coupler was constructed to measure electromagnetic noise during stable operation. Test results were compared with simulation outcomes to validate the theoretical analysis.

The results indicate that low-order electromagnetic excitation forces are the main causes of vibrations in the magnetic coupler, and significant vibrations occur when the frequency of the electromagnetic excitation force approaches the natural frequency of the magnetic coupler. Comparison with simulation results shows that the test data obtained from the magnetic coupler test platform confirm the accuracy of the theoretical analysis.

The wave generator, as the driving component, has its profile curve directly affecting the deformation and stress distribution of the flexible wheel. To reduce the stress on the flexible wheel and improve its fatigue performance, a design method for a three-term cosine cam wave generator was proposed.

The profile curve of the three-term cosine wave generator was composed of a constant term, represented by the base circle radius, and three cosine terms superimposed. By using the curvature variation coefficient at the major axis, the correction factor at the minor axis, and the clearance of the flexible bearing as variable parameters, the influence of these parameters on the performance of the wave generator was analyzed, and the optimization of a specific harmonic reducer model was validated. Finite element analysis was performed on the flexible wheel structure after incorporating the new cam structure under expansion, no-load, and loading conditions, and comparisons were made with the pre-optimized structure to analyze the stress distribution on the flexible wheel.

The finite element results indicate that, compared to the traditional cosine wave generator, the flexible wheel under the three-term cosine wave generator exhibits superior stress performance under various working conditions and achieves longer fatigue life.

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.

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.