最新刊期
卷 54 ， 期 7 ， 2020
- 摘要：To solve the problem of the dead -one characteristics affecting the tracking accuracy of the system for rehabilitation training walker, a backstepping finite-time control method with dead -one compensation is correspondingly proposed. Taking the unknown dead -one of the system into account, the width of the dead -one is estimated with the adaptive method to obtain information in the dead -one and compensate the dead -one, thus effectively suppressing the influence of the dead -one on the tracking performance of the system and avoiding the limit cycle oscillation of the system. In addition, to prevent the large tracking error during the initial motion of the walker endangering the safety of the rehabilitee, a backstepping finite-time control method is proposed to ensure that the tracking error remains stable within a limited period. Following Lyapunov finite-time stability theory, the stability conditions and stability time of the error system are obtained. For the control method of sim关键词：omnidirectional rehabilitative training walker;dead--one compensation;backstepping finite-time control;tracking accuracy336|4|1更新时间：2025-07-09
- 摘要：To solve the test problems caused by the statically fixed connection and high pillar structure of large amphibious aircraft landing gear, based on the stiffness equivalence theory, two models of landing gear connected with fuselage and connected with test device were analy-ed by numerical simulation method. By optimi-ing the structural form, si-e and thickness of the test device, the displacement of landing gear-device connection model in the main direction of deformation was simulated according to that of the landing gear-fuselage connection model. Based on the numerical simulation of mechanical boundary condition, the displacement at the center point of the main landing gear shaft under the maximum load was calculated, and the installation position of the loading point was adjusted in advance to ensure the loading accuracy under the maximum load. The results showed that under the maximum resilience load condition(the load ratio of inner wheel to outer wheel is 6:4)for the tail subsid关键词：large amphibious aircraft;high pillar;statically indeterminate structure;landing gear;static strength test191|4|4更新时间：2025-07-09
- 摘要：To solve the problem of clutch engagement smoothness caused by uncertain factors such as non-stationary random cyclic load, a method for estimating the uncertainty of the clutch engagement process control is proposed. Taking the clutch engagement process of heavy load reverse operation of a 5 t loader under V-type working condition as the research object, the uncertainty expression of the speed difference between the driving and driven ends of the clutch engagement is obtained by reducing the order of the torsional vibration equation of the clutch engagement process and on the basis of constructing the parameter expression of non-stationary random cyclic load uncertainty and the time-varying model of clutch engagement friction torque. Transmission parameter calibration, bench test and numerical simulation are conducted, and the results show that the method can reali-e the analysis of clutch engagement smoothness and the uncertainty threshold estimation. The uncertainty estimation metho关键词：clutch;uncertainty;estimation;control188|4|2更新时间：2025-07-09
- 摘要：To weaken the impact of steering performance degradation during long-term automatic driving, a dynamic steering torque compensation method for driving robot vehicle based on multi-innovation is proposed. The vehicle dynamic model and driving robot vehicle dynamic model are constructed, then an off-line self-learning model for the steering performance of driving robot vehicle is established, which takes the path curvature and the vehicle speed as input and the steering wheel angle as output. And a controlled autoregressive on-line identification model is established, which takes the angular velocity of steering wheel, angular acceleration and wheel angle as input and the driving torque of steering manipulator as output, and the parameters are identified with the forgetting factor multi-innovation least square method, the scalar innovation is extended to vector innovation in the iterative calculation to improve the identification accuracy of steering performance parameters of driving rob166|4|2更新时间：2025-07-09
- 摘要：A robust control method for clutch engagement process is proposed for the engagement quality problem caused by the nonlinearity, external disturbance and parameter uncertainty in the clutch engagement process. Firstly, taking the clutch engagement process in the heavy-duty reverse shifting of a 5-ton loader in V-type working condition as the research object, a multi-objective functional with performance evaluation based on jerk and friction work is established. According to the Pontryagin-s maximum principle and terminal constraints, after solving the functional extremum of the parameteri-ed non-stationary random terms in the disturbance matrix, the optimal trajectory of the torque under the time-varying optimal control law and weight combination is obtained. Secondly, through the variable transformation, the time-varying torque optimal trajectory is transformed into the pressure tracking trajectory of the nonlinear clutch hydraulic actuator with parameter perturbation. Finally, the a关键词：clutch;engagement quality;optimal trajectory;ASMC;Lyapunov stability theory203|4|0更新时间：2025-07-09
- 摘要：To quantitatively expound the mechanism of using cylinder deactivation(CDA)technology to improve the partial-load fuel economy of a direct-injection spark-ignition engine, bench test was carried out to investigate the combustion and emission characteristics and fuel economy of the engine in the CDA and full-cylinder modes. Moreover, numerical simulation was used to quantitatively analy-e the energy balance and determine the effects of various factors on fuel saving of the CDA engine. The results show that, in comparison with the full-cylinder mode, the ignition delay and combustion duration are shortened, the peak values of the in-cylinder pressure and heat release rate are increased, and the cyclic variation of combustion is reduced in the CDA mode. In addition, HC and CO emissions are reduced, while NOx emissions are increased in the CDA mode. Under the test conditions, the fuel economy of the CDA engine is improved by 8.2% to 15.8%. In comparison with the full-cylinder mo176|4|1更新时间：2025-07-09
- 摘要：A contoured crater cooling hole was designed. With solutions of RANS(Reynolds-averaged Navier-Stokes)equations, the film cooling efficiency on a plain surface with cooling hole embedded in contoured crater was investigated. With the existing experimental data, the reliability of numerical methods was validated. Then, the influences of blowing ratio and crater depth on the cooling efficiency were studied. The numerical results for plain surface with cooling hole embedded in contoured crater were also compared with that of the conventional round hole configuration. The results show that, among all selected turbulence models, the Reali-able k-- turbulence model has the superior accuracy in predicting the cooling efficiency on plain surface. The cooling hole embedded in contoured crater is able to generate a pair of reverse vortices that hinder the development of kidney vortices, reducing the mixing effect of coolant and high temperature mainstream. Correspondingly, the coverage of coolin关键词：film cooling;crater;blowing ratio;kidney vortex174|5|6更新时间：2025-07-09
- 摘要：To reduce the total pressure loss of the tangential admission volute and improve the uniformity of outlet air flow, the factors affecting the aerodynamic characteristics and flow field of the tangential admission volute are investigated. The effects of transverse distance and cross section shape on the aerodynamic performance of the tangential admission volute of steam turbine are numerically evaluated with the three-dimensional RANS equations and SST turbulence model. The obtained numerical mass flow rate and outlet Mach number of the partial alignment tangential admission volute coincide well with the experimental data to verify the accuracy of the numerical approach. The flow fields and aerodynamic parameters of five kinds of tangential admission volutes coupled with stationary vanes are compared and discussed under different inlet total pressure conditions. The results show that the outlet flow angles of five kinds of tangential admission volutes with stationary vanes almost remain关键词：steam turbine;tangential admission volute;aerodynamic performance;numerical simulation148|4|0更新时间：2025-07-09
- 摘要：In order to solve the problem of insufficient liquid film bearing capacity of marine sliding bearings caused by local solid contact and rubbing under low-speed and water-lubricated conditions, the influence of surface roughness on the mixed lubrication performance of water-lubricated sliding bearings is studied. This paper assumes that the asperities on the journal and bearing surfaces follow the Gaussian distribution, and the surface roughness is characteri-ed by the comprehensive standard deviation of the heights of the asperities. The average Reynolds fluid lubrication equation and the Greenwood-Tripp(GT)solid surface contact equation are combined to compare and analy-e the thickness and pressure distribution of the liquid film under full film lubrication and mixed lubrication. The effects of surface roughness on liquid film bearing capacity and maximum pressure, asperity contact bearing capacity and maximum pressure, eccentricity, and minimum nominal liquid film thickness are studi关键词：sliding bearing;mixed lubrication;surface roughness;low-speed and water-lubricated182|5|16更新时间：2025-07-09
- 摘要：To solve the problem of shaft system inclination in the actual operation of marine tilting-pad thrust bearing, a thermo-elasto-hydro-dynamic(TEHD)model of tilting-pad thrust bearing is established, and the influence of inclination state on the static and dynamic performances of the bearing is studied. Firstly, a mathematical model is proposed to describe the inclination state with two parameters of inclined angle and axis projection angle. Then, the static and dynamic characteristics of the bearing are solved by combining the TEHD model and the axial oil film stiffness and damping coefficient solution model. Finally, the influences of inclined angle and axis projection angle on the static and dynamic characteristics of tilting-pad thrust bearing are analy-ed. The static performance parameters include load, minimum oil film thickness, maximum oil film pressure and maximum oil film temperature; and the dynamic performance parameters include axial oil film stiffness and damping coefficien关键词：tilting-pad thrust bearing;thermo-elasto-hydro-dynamic lubrication;inclination;static and dynamic characteristics188|5|8更新时间：2025-07-09
- 摘要：Aiming at the problems of noise suppression and high-speed measurement accuracy in the on-line measurement of the rotational speed of rolling bearing cage under actual working conditions, a method for measuring the rotational speed of rolling bearing cage based on the ultrasonic measurement with spectrum refinement is proposed. The influence of time-domain noise on the ultrasonic echo pulse signal is suppressed by introducing autocorrelation analysis and FFT transform. The CZT spectrum refining algorithm is used to improve the calculation accuracy of the passing frequency of the roller, so as to improve the calculation accuracy of the bearing cage-s rotational speed. Experimental results of high-speed rolling bearing at 28 000 r/min show that this method can effectively overcome the influence of noise under actual working conditions, and achieve accurate measurement of high rotational speed under speed fluctuation with a measurement error less than 0.1%.关键词：ultrasonic measurement;rolling bearing;bearing cage;spectrum refinement212|5|4更新时间：2025-07-09
- 摘要：To improve the accuracy of the end-effector of a parallel mechanism with multiple operation modes and obtain the influencing rule of each error source on the accuracy of the end-effector and its optimal value, error modeling and component tolerance optimi-ation design are carried out by taking a 2-R(SS)2-R(RR)2(RR)2 parallel mechanism with two operation modes as example. An inverse position model that can take both operation modes into account is established by the vector method. Based on the error models of R(SS)2 branch and R(RR)2(RR)2 branch, the unified error models of 2-R(SS)2-R(RR)2(RR)2 parallel mechanism considering both operation modes is established. The uncompensable errors of the parallel mechanism in different operation modes are extracted, and the mapping relationship between the uncompensable errors and each error source of the whole mechanism is established. Based on the s关键词：parallel mechanism;two operation modes;error modeling;accuracy design149|4|1更新时间：2025-07-09
- 摘要：To reduce the transient vibration induced by electromagnetic force during the soft-startup process of an asynchronous motor, a method for analy-ing the transient vibration using co-simulation on control strategy and multi-physical domain finite element method(FEM)is presented. An electromagnetic force analytical model to qualitatively analy-e the frequency and amplitude of low-order electromagnetic force in the starting process is constructed. Aiming at the coupling effect between the input and the load, a simulation model of main pump motor during soft-startup process is established to provide initial conditions for subsequent electromagnetic analysis. Based on the quasi-steady state assumption, the motor-s soft-startup process is regarded as a set of discrete quasi-steady states. Each transient magnetic field under quasi-steady state is evaluated by the 2D electromagnetic FEM, then all the electromagnetic forces are interpolated to obtain the electromagnetic force in the entire star关键词：transient vibration;induction motor;soft-startup;electromagnetic force165|5|1更新时间：2025-07-09
- 摘要：For optimi-ing electrical performance of tri-post insulator on AC 1 100 kV GIL, structural parameter optimi-ation with genetic algorithm is carried out. Electric field and stress field simulation models of tri-post insulator are established. Checking the electrical and mechanical performances of the insulator, it is found that the maximum surface electrical field intensity is 12.13 MV-m-1 at the connection between the pillar and the central cylinder, which is higher than the allowable value of 12 MV-m-1. It is thus necessary to optimi-e the electrical performance. A parametric model of tri-post insulator is constructed and used to analy-e the influence of structural parameters on electrical performance. It is found that the increase of each structure parameter can optimi-e the electrical performance, but this also leads to the increase of insulator volume. To improve the electrical performance, a genetic algorithm-based optimi-ation scheme for the structure para239|4|7更新时间：2025-07-09
- 摘要：Due to the real-time requirements of ultra-high-definition video encoding and the data throughput bottleneck in the entropy encoding system, a hardware architecture based on wavefront parallel processing(WPP)technology is proposed, which improves the parallelism of coding while retaining row-to-row dependency, and provides higher throughput and compression efficiency. This architecture allows three-threaded coding tree units to be encoded simultaneously, thus improves the parallelism by nearly three times. The synchronous update unit ensures the probability models between threads can be updated simultaneously. The probability models in a single thread support parallel updating of multiple binary symbols. Initiali-ation unit can initiali-e the coding units in multiple modes. Online mode and offline mode are both supported, which can balance the throughput between entropy encoder and other modules. This entropy encoder delivers an average of 5 b per cycle. The design is synthesi-ed in SM关键词：high-efficiency video coding;entropy encoding;wavefront parallel processing157|4|2更新时间：2025-07-09
- 摘要：Aiming at the problems of insufficient acquisition of features and low recognition accuracy of single target for multi-person scene in gait recognition from Wi-Fi signal perception, a new gait recognition model WiNet is proposed. Depending on the channel state information impact factor analysis, the amplitude data is chosen as the basic data for gait recognition, and a mechanism named frequency energy map is adopted to reconstruct the raw data effectively in WiNet. The advantage of WiNet lies in the capacity of extracting effective features generated by the gait behavior on the inter-subcarrier and intra-subcarrier signals at the same time, which greatly improves the individual recognition in gait recognition. The frequency energy map is used as the input matrix of the convolutional neural network model. After multiple groups convolution, regulari-ation and activation operations, the softmax method is used in classification, and the individual identity corresponding to the gait behavio关键词：gait recognition;channel state information;frequency energy map;convolutional neural network200|4|6更新时间：2025-07-09
- 摘要：To improve the aggregation of reinforcements in titanium matrix composites, solid solution and aging treatments were used, and the effects ofTi3SiC2 content on the microstructure and mechanical properties of the composites were studied. Scanning electron microscope and energy spectrum analy-er were adopted to observe the microstructures with differentTi3SiC2 contents. The refining mechanism of the matrix and the precipitation of the reinforcements during the heat treatment were investigated. The results show that the original grain si-e of as-treated composites decreases significantly with theTi3SiC2 content, and the grain si-e of lamella - phase also reduces.Ti5Si3 particles precipitate in the - and - phases and at the interface of - and - phases, and its content increases withTi3SiC2 content. The yield strength and compressive strength of the composites are significantly关键词：heat treatment;Ti3SiC2;(Ti5Si3+TiC)/TC4 composite;microstructure;mechanical property166|4|2更新时间：2025-07-09
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0