In order to improve obstacle avoidance accuracy of intelligent wheelchair, a control algorithm of intelligent wheelchair based on fuzzy PID control was proposed. The kinematics model of intelligent wheelchair was established, and the intelligent wheelchair control system based on Fuzzy PID control was designed on the basis of traditional PID control method. Matlab was used to construct simulation tests, the fuzzy controller was designed and constructed in Simulink, and the obstacle avoidance performances of traditional and fuzzy PID control were simulated. The experimental results show that the control algorithm can optimize the obstacle avoidance error of intelligent wheelchair, and it has advantages of small overshoot, fast response, and higher accuracy compared with the traditional PID control algorithm.
Hydrogen, as a clean energy source, has been widely used in the automotive industry. However, considering the difficulties of hydrogen storage and transportation, the in-situ production process has received increasing attention. In this paper, a hydrogen production system for dimethyl ether self-heating steam reforming is proposed, using a spiral tube reactor in which the oxidation of dimethyl ether occurs in the spiral tube, and the exothermic oxidation of dimethyl ether is used to provide heat for the dimethyl ether steam reforming hydrogen production reaction. A numerical model of the hydrogen production system for dimethyl ether self-heating reforming is developed, the model is simulated and analyzed, the accuracy of the model is verified through experiments, the influence of various parameters and on the system is analyzed, and the system is optimized. The results show that the proposed system can solve the problems of high energy consumption, low hydrogen yield and difficult reaction control faced by traditional autothermal reforming hydrogen production, and the system can achieve 87.79% dimethyl ether conversion rate, 84.94% hydrogen yield and 85.94% system thermal efficiency.
To solve the problem of environmental pollution caused by the difficult degradation of antibiotics, Ce-TiO2/SiC foam was prepared, levofloxacin (Levofloxacin, LEV) was chosen as the target pollutant, and a photocatalytic ozonation coupling system (Ce-TiO2/SiC + LED + O3) was studied. The results show that the coupling system can effectively degrade LEV, the LEV removal was 99% and the chemical oxygen demand (COD) removal was as high as 85.9%. The coupling system showed a good synergistic effect, and its first-order reaction kinetic rate constant was greater than the sum of ozonation (O3) and photocatalysis (Ce-TiO2/SiC + LED). In addition, the stability experiment of Ce-TiO2/SiC foam showed that the photocatalytic ozonation activity is basically unchanged after five reuses.
The effects of different extraction methods on polysaccharide content and antioxidant activity of northern Ban-Lan-Gen were investigated. The polysaccharide of northern Ban-Lan-Gen was extracted by conventional reflux extraction method and ultrasonic assisted reflux extraction method. The total polysaccharide content was determined by phenol-sulfuric acid spectrophotometry. DPPH free radical and ABTS+ free radical scavenging assays were used to evaluate their antioxidant activity in vitro. The results show that the yield of polysaccharide extracted by ultrasonic assisted reflux extraction method was 40.07%, which was significantly higher than that by conventional reflux extraction method (13.42%). The phenol-sulfuric acid method has high precision, repeatability, stability and good recovery, which can be used to study the polysaccharide content of northern Ban-Lan-Gen prepared by different extraction methods. The polysaccharide content of ultrasonic assisted reflux extraction method was 22.3% higher than that of conventional reflux extraction method, and the scavenging effects of DPPH· and ABTS+· was significantly better than that of conventional reflux extraction method. The results provide a reference for the application of ultrasonic technology in the extraction of polysaccharide of northern Ban-Lan-Gen.
A SiC-enhanced carbon nanofiber composite (SiC@CNFs) structure was prepared by electrospinning technology combined with carbonization process. The results of TGA, XRD, XPS and SEM show that the mass fraction of SiC particles is 62%, and it is evenly distributed on the surface of CNFs. The lithium-ion battery anode material prepared by this structure not only retains the high electrical conductivity of CNFs, but also obtains the enhanced structural toughness of SiC. The electrochemical performance test results show that the capacity retention rate of the lithium-ion battery anode material is as high as 134.01% after 500 cycles, much higher than that of CNFs. Moreover, the electrochemical impedance value of the structure changes less and the conductivity of SiC@CNFs remains good. SiC@CNFs structures prepared by electrospinning technology serve as lithium-ion battery anode, with low production cost, controllable structure and stable performance, which is a beneficial supplement to the current battery cathode materials.
A series of NiO/Co3O4 catalysts within mesoporous nanosheets, synthesized by a facile hydrothermal combining wet-impregnation route, have been developed to catalyze diesel soot combustion. Results attest that, when the molar ratio of Ni/Co reached 12%, the catalyst of 12NiCo exhibited the optimal catalytic soot combustion performance, giving Tm of 347 ℃ and 100% CO2 selectivity, which can be chiefly credited to the synergetic effect of the following factors. Firstly, the unique 2D nanosheets together with high surface area enlarged the contact interface of catalyst-soot particles. Secondly, abundant mesopores within nanosheets favored the significant decrease in mass transfer resistance and then in turn promoted the adsorption and diffusion of gas reactants. Thirdly, the enhanced reducibility by introducing NiO not merely facilitated the adsorption and activation of oxygen species to form active oxygen species, but also benefited NO oxidation to produce NO2 with higher oxidative capability, thereby improving catalytic soot combustion performance remarkably. In addition, 12NiCo also presented the excellent reusability, demonstrating good potential in future practical applications.
In order to improve the accuracy of gesture recognition based on surface electromyography (sEMG), an improved deep forest combined hand motion recognition method was proposed. The extreme gradient boosting (XGBoost) tree was introduced into the deep forest model to form the cascade structure of deep forest together with the random forest and the complete random forest. The deep forest model integrates three different tree-based classifiers at each level, a total of four decision forests including a random forest, an extreme random forest and two extreme gradient boosting trees. The classification performance was improved by using the complementarity between different learning algorithms. In order to evaluate the performance of the model, the sEMG signals of 4 healthy subjects were collected for the verification experiment of hand action recognition, and compared with random forest, support vector machine, one-dimensional and two-dimensional convolutional neural networks algorithms. The result shows that the average recognition accuracy of the method for 16 commonly used hand actions is 94.14%, and the classification accuracy of sEMG signals is high.
A flux focusing magnetic gear with Z-type pole-pieces (ZP-FFMG) was presented and investigated. In this magnetic gear structure, the proposed Z-type pole-pieces can couple the magnetic flux of the end face and cylindrical face of rotors. The 3D simulation shows that there are axial and radial magnetic flux components in the ZP-FFMG, which are helpful to torque transmission. A comparative analysis of traditional flux focusing magnetic gear (FFMG) and ZP-FFMG was given. The results show that compared with the traditional FFMG, the transmission torque of the ZP-FFMG is increased by 42%, the torque density is increased by 15 kN·m/m3, and the magnetic flux density is also improved.
A two degree of freedom translational decoupling parallel micropositioning stage based on parallel flexure mechanism was proposed. A compound double parallel four-bar flexure mechanism module was adopted in the stage, and structural symmetry constraints were introduced to eliminate the coupling between shafts and parasitic displacement, and translations in X and Y directions were achieved. The stiffness matrix method was used to analyze the parallel flexure mechanism in theory. According to the observation method, the overall stiffness matrix of the micropositioning stage was established, and the differential equations of motion of the system were obtained, and the natural frequencies of each order of the system were deduced. The modal analysis of the micropositioning stage was carried out by using the finite element method, and the natural frequency and mode shape of the micropositioning stage were obtained. Through theoretical analysis, finite element calculation and experimental test, the consistency of the results shows the correctness of theoretical analysis and the effectiveness of stiffness matrix analysis.
Based on cyclic activated sludge technology (CAST) and moving-bed biofilm reactor (MBBR), mathematical modeling and simulation of CAST-MBBR process for a real wastewater treatment plant in Zhejiang Province was carried out. Based on the process mechanism, a semi-empirical biofilm model was embedded into the activated sludge model No.1 to describe the biochemical process of carbon and nitrogen removal in CAST-MBBR. It is then combined with a double exponential model describing particle sedimentation to form a complete CAST-MBBR process model, and a conversion method between inlet and outlet water quality and model components was established. The key parameters that have a significant impact on effluent indicators were screened through sensitivity analysis and adjusted. The calibrated model was verified by using the influent and effluent water data of the wastewater treatment plant throughout the year. The result shows that the simulated effluent data can agree well with the measured data, indicating that the modeling method can be effectively applied to the simulation of CAST-MBBR process.
Based on the Peltier effect, a method of real-time controlling battery temperature through thermoelectric device (TED) was proposed. It integrated the refrigeration and heating functions of TED, has a good temperature control effect, and can meet the thermal management needs of battery modules. The battery module consists of 3×5 rows of cylindrical batteries filled with foam metal composite phase change materials, and the thermoelectric device was arranged on the large face of the battery module shell. Compared with the liquid cooling experiment, thermoelectric refrigeration could significantly reduce the temperature of the battery module at 1~5 W of single cell heat generation power, and control the temperature difference of the module within 5 ℃. The temperature control experiment further shows that the TED controlled by the thermostat in real-time can effectively stabilize the module temperature and control the temperature fluctuation within 2~3 ℃. In addition, a one-dimensional thermal resistance network was established, and the thermal performance of TED was analyzed based on steady-state theory. The result shows that under the refrigeration condition, the cold junction temperature of TED is decreasing first and then increasing with increasing of its current, and the hot junction temperature is proportional to the TED current.
Electromagnetic inference (EMI) shielding materials are vital for the reduction of EM radiation pollution, in which conductive polymer-based composites have attracted wide attentions. Herein, MXene/PANI bulk composites were successfully prepared by spark plasma sintering, in which MXene was chosen as the functional 2D materials evenly dispersed in the PANI matrix through ultrasonic, mechanical agitation and freeze-drying methods. Consequently, MXene with high electrical conductivity and lamellar structure effectively improves the EMI shielding performance of PANI. When the content of MXene is 40%, the composites achieve the optimal EMI shielding characteristics of 24 dB in the range of 8.2~12.4 GHz.
An active disturbance rejection controller (ADRC) based on equivalent sliding-mode control method was proposed to solve the stability problem of quadrotor unmanned aerial vehicle (UAV) with disturbances and uncertainties. According to the transformation of the body coordinate system and ground coordinate system, combined with Newton's second law and Newton-Euler formula, the dynamic model of UAV was constructed. An extended state observer was designed to restore the state of the system and estimate all disturbances and uncertainties of the system, in order to achieve rapid error convergence and improve estimation accuracy. Based on the ADRC, the concept of an equivalent sliding-mode controller was proposed, and the control output was divided into the equivalent control term and the switching robust control term. Combined with the non-singular terminal sliding-mode control, the singular problem was avoided. Through the Lyapunov stability theory, it is proved that the designed ADRC can achieve system asymptotic stability. Finally, the active disturbance rejection performance and robustness were verified by a numerical simulation example.
The flat wire motor for Electric Vehicles have the characteristics of small size, light weight and high power density. However, with the development of high-speed motor, the AC loss of flat wire motor becomes larger, and its thermal rise performance is different from the traditional circular wire motor, so it is necessary to design a cooling method suitable for it. Firstly, a two-dimensional finite element model of a high speed flat permanent magnet synchronous motor for new energy vehicles was established, the influences of the size, layer number and parallel branches number of the flat conductor on the AC loss of the motor under the driving cycle of WLTC-3 were analyzed, and the optimal conductor size and winding connection mode were obtained. Then on the basis of loss analysis, according to the temperature field distribution of the motor, the optimal cooling method of oil cooling has been designed, which reduces the temperature rise and improves the reliability of the motor operation.
Based on the strict requirements of high maneuverability, high load and high dynamic response of unmanned vertical take-off and landing (VTOL) aircraft, a four-axis VTOL jet unmanned aerial vehicle (UAV) was researched and designed. According to the three basic equations of fluid mechanics and turbulence k−ε equation, the aerodynamic numerical simulation was carried out to determine the calculation domain of the external flow field during UAV flight. ICEM CFD software was used to divide the external flow field into hybrid unstructured grids. The flow field boundary conditions were set in the Fluent solver, and the turbulence model was taken as the basic model. The aerodynamic performance of the whole UAV were simulated and solved. The resistance coefficient, flow velocity distribution, pressure distribution and turbulent kinetic energy of each part of the UAV surface were obtained, and the aerodynamic characteristics were analyzed. The analysis shows that there are problems of large kinetic energy loss and high resistance coefficient at the top, tail, lower surface head and jet bracket of the upper surface of the UAV. According to the simulation results, the aerodynamic modeling of the above parts of the UAV was optimized. The results show that the total resistance coefficient of the UAV is reduced from the original 0.165 to 0.121, and the surface pressure, flow velocity and turbulence of the UAV are effectively improved. After optimization, the aerodynamic characteristics are better and the aerodynamic modeling is in line with the design concept.
In order to improve the path following accuracy and stability of unmanned vehicles, a parameter adaptive model predictive control (MPC) method based on particle swarm optimization (PSO) and Gaussian process regression (GPR) was proposed. By using PSO to optimize MPC parameters offline and GPR to generate optimal parametric surfaces, the path following performances of unmanned vehicles can be improved under various working conditions. The simulated results show that the improved MPC method achieves good path tracking accuracy while maintaining vehicle stability throughout the path following process. Finally, the effectiveness of the improved MPC method was verified on a real unmanned vehicle.
Based on digital twin, a real-time assembly man-hours workshop scheduling model was proposed, considering the uncertainty of assembly man-hours in the process of product customization and frequent dynamic disturbances in the assembly workshop. The overall architecture of assembly workshop scheduling based on digital twin was constructed. Radio frequency identification (RFID) technology was used to collect real-time working hours data of physical assembly workshops, and the real-time assembly working hours were processed by using the improved Rete algorithm. A mathematical model of assembly workshop scheduling based on real-time assembly man-hours was established, and an improved artificial fish swarm-taboo algorithm was used to solve the model, so as to realize the scheduling optimization of the real-time assembly man-hours workshop. The empirical result shows that the model algorithm has certain feasibility and superiority in real-time assembly man-hours workshop scheduling.
以某V形支撑连续刚构桥为工程背景,对V形支撑 0号块进行施工阶段分析和施工工况分析.计算分析得到如下结论:V形支撑 0号块在施工过程中的应力满足规范要求,其施工过程中的受力特性可供设计和施工人员参考;V形支撑 0号块对顺桥向水平位移和竖向位移较为敏感,在施工过程中应该注意结构的位移监测;施工工况分析的结果与更为真实的施工阶段分析的结果存在一定差距,在实际的工程计算中应尽可能采用施工阶段分析.
采用两步水热法合成由纳米片组装而成的三维Bi2MoO6/ZnO微花,通过调控复合物中Bi2MoO6,制备一系列不同摩尔比的Bi2MoO6/ZnO微花.研究表明,Bi2MoO6/ZnO-10%复合材料在可见光照射 20 min后,对罗丹明 B(RhB)溶液的光催化降解率达到 79.61%,相较于纯ZnO和Bi2MoO6,复合材料具有更好的光催化性能.通过紫外可见光谱(UV-Vis)和室温荧光光谱(PL)分析推测,由于复合材料的光吸收范围提高和异质结的形成抑制了光生载流子的复合,进而提升了Bi2MoO6/ZnO微花光催化性能.
永磁同步电机(Permanent Magnet Synchronous Motor,PMSM)矢量控制系统转速环采用PI控制器难以满足系统动态响应速度快、鲁棒性强等要求,采用分数阶比例积分(Fractional Order Proportional Integral,FOPI)控制器,并利用麻雀搜索算法(Sparrow Search Algorithm,SSA)优化FOPI控制器参数.通过搜索最优适应度的麻雀所在位置,得到控制器最优组合参数,选择时间乘以误差绝对值积分作为其目标适应度函数.对SSA整定FOPI、粒子群算法(Particle Swarm Optimization,PSO)整定PI参数的电机调速性能进行试验对比.结果表明,SSA优化的FOPI具有增强鲁棒性和减小超调量的优势.
