Abstract:To achieve the invasion, precision, intelligentization and remote manipulation of the surgery, the minimally invasive surgical robot developed by combining robotics with minimally invasive surgery (MIS) improves the environment and tools for MIS, and enhances the performance of the surgery, which has comprehensive application and development prospects. Based on the review of the research status of minimally invasive surgical robot, a variety of key technologies such as design of slave robotic arms, control structures and methods, haptic master hands, surgical instruments and force perceptive devices are discussed and analyzed, and then the augmented reality, semi-automatic surgery, surgical training system and the trend of minimally invasive surgical robotic technologies are presented.

Abstract:To explore an efficient polishing method for ultra-hard brittle silicon carbide materials, an ultrasonic-electrochemical mechanical polishing experiment was performed on the SiC specimens by controlling variable method. The SiC specimens were polished by cast iron polishing plate, polyurethane polishing plate and semi-fixed abrasive polishing plate in three kinds of polishing liquids, i.e. tap water, KOH solution and Fenton reaction solution respectively, and the optimized polishing process parameters based on the material removal rate and surface quality of SiC specimen were obtained. The results show that the material removal rate is high when using cast iron polishing plate, but the surface quality is poor. The surface quality is best when using semi-fixed abrasive polishing plate, but the material removal rate is low. The Fenton solution has the best effect on improving the material removal rate. When the voltage between specimen and polishing plate is +10 V, the material removal rate is the highest, which is raised by 55.1% than that without voltage. When the ultrasonic vibration of the specimen retaining ring was applied, the material removal rate was increased by 91.7% compared with that of non-ultrasound. The ultrasonic vibration plays a major role in the polishing of SiC specimen.

Abstract:For using online data to diagnose the degradation status of commercial aero-engine components, an aggregated method including engine steady state modeling and unscented Kalman filter (UKF) was proposed. First, the method represents the general characteristic curves of components with nonlinear multivariate functions with respect to their working conditions, and uses machine learning methods to confirm function coefficients that fit the observed data best, subsequently acquires the steady working model of aero-engines. Then, by analysis of individual degradation properties and effects on entire engine performance of components, the key degradation factors of components were defined. Moreover, the standard UKF process was modified, by adding moving window sampling strategy to overcome low-observability problem, and replacing standard observation equation with combined model of engine steady state model and engine working conditions. At last, the acquired filter was used to process observed engine data to track the trends of component degradation factors. As indicated by the test on commercial engine dataset, the proposed method can conveniently diagnose the health status of engine components once the observed report returns to on-ground data centers, and the acquired results coincided well with the internal damage information of engines collected by visual inspection. The proposed method performed well in overcoming modeling nonlinearity, low-observability, and high data noise problems in aero-engine performance diagnosis and showed to be applicable to industrial conditions.

Abstract:Aiming at the psychological impact on human and personalized matching problem, which are caused by the long-term coexistence between human and humanoid robot in the future, a more universal artificial emotion calculation model in the PAD (Pleasure, Arousal, Dominance) emotional space is proposed. The overall framework of the artificial emotion model consists of 3 sections: external event detection and processing, generation and correction of emotional response vectors and emotional discretization. Firstly, an effective external stimulus 3D annotation method is put forward, after that, according to the external stimuli, a computational model of emotion which can generate emotional response is proposed, and the personality and mood model are introduced to realize the personalized emotional response. Then, an emotional response vector discretization method is carried out, and the emotional intensity computational formula is proposed on basis of specific emotion types. Finally, the expression synthesis and voice response model is proposed according to the emotion generated by the emotion model. The speech dialogue and expression state migration experiment on the H&F robot-III humanoid head robot platform is carried out, and the results show that the artificial emotion model can generate personalized emotional response to external stimuli and simulate the process of human emotion changes effectively.

Abstract:To improve target recognition accuracy and pose estimation precision in unstructured environment, a novel method for automatic recognition and 3D pose estimation of different kinds of targets is presented based on the object CAD model and Kinect V2 RGB-D sensor. The depth image of object CAD model is obtained by a virtual camera, and it is converted into one point cloud. A voxel grid filter is utilized to reduce the number of points for the point cloud of the scene, and the point pair feature(PPF) is used as the global descriptor of CAD model. The similar PPFs are classified as the same group and put into one hash table to recognize and locate the targets. The hash tables of all targets compose the 3D model database. A voting scheme is adopted for different kinds of objects recognition and 3D pose estimation. Pose cluster and ICP registration are employed to refine 3D pose. The accuracy of 3D pose estimation is improved by filtering the mismatching poses. The recognition rate and the pose estimation error of three kinds of pipe joints are analyzed in the environment of virtual robot experimentation platform (V-REP). The simulation results show that the average recognition rate of three kinds of pipe joints is 96%. The position error is less than 4 mm and the orientation error is no more than 2°, which meet the requirement of manipulator grasping. The experiments of comparison with other mainstream methods are performed. The experimental results show that the recognition rate and the F1 score of the proposed method are superior to those of two other methods.

Abstract:To understand combustion characteristics of Lvliang bituminous coal slime from Shanxi Province and to study the effects of changing particle diameter and oxygen volume fraction, O₂/CO₂ combustion experiments of coal slime pellets were carried out, in which the thermocouple was used to online measure the inner temperature during the combustion process, and simultaneously the whole combustion process was monitored by a high-resolution camera. The results indicate that the dry coal slime pellets show different ignition modes at 800 ℃ under different conditions of 10%～50% O₂ concentrations. The maximum inner temperature of the coal slime pellets increases with the increasing of volume fraction, but irrelated with its diameter. The enrichment of oxygen facilitates burnout of the coal slime pellets with same particle sizes. The ignition delay time decreases as the volume fraction increases.

Abstract:In order to realize the waste biogas recycled as reburning fuel in industrial boilers aims to reduce nitrogen oxides （NO_x） high efficiency, which can achieve resource recovery and NOx emission reduction. Characteristics of industrial boiler bed and furnace were simulated by combining FLIC and FLUENT software, and the effects of CH₄/NO molar ratio, biogas dilution and biogas nozzles arrangement on in-furnace NO_x emission were investigated. The results showed that the CH₄/NO molar ratio and the degree of mixing between the two were the main factors affecting the reduction of NO_x, and NO_x reduction efficiency increased with CH₄/NO molar ratio and biogas dilution ratio increasing in general. When the CH₄/NO molar ratio was small, the dominant factor influencing NO_x reduction efficiency was the mixture degree of them. When biogas was diluted to a certain degree, which could guarantee possessing sufficient momentum to mix well with the main flow, the dominant factor influencing NO_x reduction efficiency was CH₄/NO molar ratio. At the same time, increasing of biogas dilution ratio was beneficial to reduce the loss of gas incomplete combustion. To realize of NOx high efficiency reduction, the biomass nozzles should be arranged at the front wall, and the position should not be too low. This paper could provide some reference of biogas for industrial boilers combustion and NO_x reduction.

Abstract:Microwave sensitization including microwave and activated carbon can significantly improve Fenton oxidation ability. To study the generation mechanism of product and the relationship between microwave, AC and H₂O₂, materials of different sizes and different Fe content were made, several control experiment were carried out to prove the possible generation ways of O₂, CO₂ NO₂₃ and the effect of microwave and AC, the mechanism of NO catalytic oxidation by Fenton reagent combined with microwave sensitization were obtained at last. The results indicate that the microwave sensitization can increase the NO removal efficiency from 33.1% to 46.3%, increase O₂ content from 6.9% to 18.6%, and produce 68×10^-6 CO. O₂ generates through AC's absorption and catalysis of Fe²⁺. C and NO can only be oxidized into CO and NO₂ by the OH, HO₂ produced by Fenton reaction. Microwave can intensify all possible reactions in the reagent, the developed pore structure is prerequisite of microwave sensitization of AC, and part of the Fe included in AC joins in the Fenton reagent.

Abstract:To draw the track of roller compacting in the compaction process and to realize the real-time monitoring of the rolling track, by means of the analysis of real time data of GPS receiver, the geodetic coordinates of the roller in the WGS-84 world geodetic coordinate system are obtained. Using the Gauss projection positive algorithm, the geodetic coordinates are converted into plane coordinates in the 54 plane coordinate system of Beijing, then the plane four parameter conversion method is used to get the construction coordinates required by the roller and the construction plane coordinate system of the roller is set up, the real time positioning of the roller in the compaction process is realized. Finally, according to theoretical analysis and experiment, the longitudinal and lateral positioning method of roller compacting track is verified . The results show that the roller compaction trajectory plotted by the plane location algorithm is fast, reliable and practical, which can realize real-time monitoring of roller compaction trajectory during compacting process.

Abstract:To analyze the yaw and rollover stability of an off-road vehicle with mechanical elastic wheel (MEW), based on the brush tire model, a corrected steady-state combined longitudinal-slip and cornering brush models of MEW is set up. The flat-bed test rig of tire mechanical properties is used to conduct the steady-state longitudinal-slip and cornering characteristics experiment of the MEW and pneumatic tire, respectively, and the mechanical properties of MEW are analyzed based on the experiment results. Then, a nonlinear off-road vehicle simulation model with MEW is established to evaluate the yaw and rollover stability based on Carsim, which utilizes yaw rate and predictive load transfer ratio (PLTR) as the yaw and rollover index respectively. The cornering properties of MEW to yaw and rollover stability are analyzed based on phase-plane. Compared analysis of the cornering characteristics of pneumatic tire and MEW are done and the results show that the changed trend of cornering characteristic curve and the peak value of lateral force are almost the same, but the cornering stiffness of MEW is bigger and the vehicle with MEW has a good stability of rollover but yaw, furthermore, as peak value of lateral force increases and lateral stiffness decreases properly, the vehicle can achieve a better stability of yaw and rollover. The above simulations will be useful for the improvement and optimization of cornering performance and structure parameters of MEW.

Abstract:To study the effect of different courses of ditching on wavy water, a sliding dynamic grid method based on rigid dynamic grid and sliding grid is developed. While ensuring that the free surface is in the grid encryption area, it is possible to simulate any attitude of the airplane under complicated sea conditions. By simulating three-dimensional rectangular flat plate oblique impact into water, the vertical movement history and the pressure distribution are compared with experimental data to verify the effectiveness of numerical method, and the grid parameter setting experience is also got. The simulation results of airplane ditching on calm water using sliding dynamic grid method are compared with experimental data to verify the effectiveness of sliding dynamic grid method. On the basis of application of wave making method, numerical simulation of three different ditching courses on wavy water, such as heading waves, following waves and parallel to waves are made. By comparing and analyzing the movement history and the force of different parts, it is concluded that the optimal course of ditching on wavy water is parallel to waves, the vertical impact peak is 12% larger than that on calm water, and the effects of roll and yaw motion is small. The most dangerous situation is heading waves, which will produce larger pitch angle, the vertical impact peak is 149% larger than that of calm water ditching, and will suffer many wave impacts.

Abstract:To capture the high-quality wind energy in built environment, combined with height advantage of skyscraper and canyon wind effect of building diffuser, the vertical axis wind turbines were mounted between the building diffusers. By the means of numerical simulation, the aerodynamic characteristics of building augmented vertical axis wind turbine with different solidity and different airfoil configuration had been investigated. The results show that the building diffusers can sharply increase the power coefficient of wind turbine. The optimal power coefficient of building augmented wind turbine is 4.47 times higher than the clean one and the optimal tip-speed ratio shifts to the right. But it has intense load fluctuation and it is sensitive to building configuration. The circular configuration can decrease the influence of shedding vortex of buildings. With increasing solidity, the power coefficient of building augmented vertical axis wind turbine increases first and then decreases due to the interference between blades, and the load fluctuation and self-starting have been improved obviously. The FXLV152 airfoil contributes to decrease the fatigue cumulative damage and the NACA0021 airfoil contributes to increase efficiency of wind turbine. However, the S809 airfoil is not appreciated for building augmented vertical axis wind turbines. The numerical results provide a reference for practical application of building augmented vertical axis wind turbines.

Abstract:To investigate the effect of lean/bowed vane configurations on the aerodynamic performance and unsteadiness in transonic high-pressure turbine, the full three dimensional viscous unsteady numerical simulation were performed by solving N-S equations based on SAS SST method．The influence of bowed /lean vanes on turbine efficiency and efficiency fluctuation were investigated, and the action of vane modeling to the aerodynamic total perturbation level and the amplitude of each vane passing frequency were analyzed. The linking of the pressure fluctuation on blade surface with flow distortions was accomplished by comparing instantaneous pressure fluctuation contours of blade with space-time maps, which can reveal the mechanism of the influence of the vane modeling. The results indicate that the turbine efficiency is promoted with positive lean and bowed vane modeling, and the fluctuation of stage turbine is repressed, which is beneficial to the smooth running of the turbine stage. The aerodynamic disturbance on the rotor blade is dominated by the moving of vane trailing edge shock system, and the vane modeling can reduce the perturbation level on the rotor blade. For the positive lean vane, the unsteadiness at the root and tip region is reduced by the reduction of the amplitude of the first harmonic, but it is reduced by the reduction of the amplitude of second and higher harmonic at the middle region. For the positive bowed vane, unsteadiness is repressed by reducing the amplitude of third harmonic at the root region, and the first harmonic at the tip region and the amplitude of each harmonic is reduced at the middle region.

Abstract:In view of the difference between the torque distribution principle in the hybrid gearshift schedule calculation and the actual operation condition, on the basis of a parallel pulg-in hybrid electric vehicle (PHEV), the torque distribution principle was formulated with the velocity, throttle opening and battery SOC as control parameters. Considering the influence of dual power source synergy and battery SOC, the calculation principles and methods of dynamic and economic improved two-parameter gearshift schedules were defined, and the dynamic gearshift schedule was gained with maximizing traction as optimization objective, as the economic gearshift schedule was gained with maximizing systematic efficiency as optimization objective. The simulation of the proposed improved two-parameter dynamic and economic gearshift schedules were compared to the initial gearshift schedule on the platform of AVL Cruise and Matlab/Simulink. The acceleration time of 0~100 km·h^-1 is shortened by 5.9%, and the consumption of SOC balanced is reduced by 10.4% and 7.5% respectively under the NEDC and WLTC.

Abstract:To further understand single-piston free piston expander linear generator (FPE-LG), a novel FPE-LG prototype had been established for small scale organic Rankine cycle(ORC) waste heat recovery system. The single-piston FPE-LG can operate continuously and stably based on the compressed air test bench, which indicates that the working principle of single-piston FPE-LG is feasible. The effects of intake pressure, piston stroke length, external load resistance and intake duration on the motion characteristics of the single-piston FPE-LG are investigated, and the results show that the variation trend of piston displacement and velocity exhibits a regular sinusoidal fluctuation. Relative high velocity is near the dead centers and peak acceleration is usually obtained when the piston arrives at left dead center(LDC) or right dead center(RDC). By using the variable length of piston stroke to improve output power is feasible. But the change of piston stroke has little effect on the peak piston velocity and the peak pressure of cylinder. The peak piston velocity and piston stroke utilization ratio (η) increase with the external load resistance. When the external load resistance increases from 20 Ω to 80 Ω, the peak piston velocity and η increase from 0.56 m/s and 58.26% to 0.84 m/s and 78.42%, respectively. Increasing intake duration is beneficial to obtaining higher piston velocity, piston stroke utilization ratio and output power. The peak output power increases from 13.87 W to 37.40 W when the intake duration changes from 20 ms to 40 ms.

Abstract:A smoothing method for single crystal silicon carbide (SiC) especially with the combination of mechanical lapping and photocatalysis-assisted chemical mechanical polishing (PCMP) is proposed to solve the problems of traditional polishing methods, such as low efficiency, serious pollution, great damage, etc, by which the atomic smoothing of SiC wafer is removed by the powerful oxidability of UV photo-excited hydroxyl radical on nano TiO₂ particles. A orthogonal experiment (L₉(3³)) was first designed to develop efficient slurries for PCMP, and subsequently the optimized processing technology was obtained by method of detecting the surface roughness of silicon carbide wafer in the polishing process. The results show that the catalyst has greatest effect on the oxidability of slurry, and then is the electronic capture agent and the dispersing agent. The preferable slurry formula is TiO₂(0.5 g.L^-1), H₂O₂(1.5 mol.L^-1) and (Na₂PO₃)₆(0.1 g.L^-1). The proper polishing technique is the lapping SiC for 30 min with 5 μm and 2 μm diamond powders first, the material removal rate (R_MRR) is 8.72 μm/h and 4.56 μm/h, respectively. And then is the removing the damage caused by mechanical lapping with PCMP, 0.5 μm alumina powder was used for rough polishing for 50 min, and 0.05 μm alumina powder for fine polishing for 60 min in the polishing process, of which the R_MRR is 1.81 μm/h and 1.03 μm/h, respectively. The best surface roughness R_a with the proper progress can be reduced to about 0.47 nm, which may satisfy the requirements of high efficiency, ultra smooth and low damage for polishing single crystal silicon carbide.

Abstract:To study the effects of different grinding parameters, different mass fraction and sizes of Cr₃C₂ on ground surface quality of the laser cladding Cr₃C₂/Ni based composite coating, as well as to explore the grinding characteristics and the generation mechanism of the ground surface defects, the grinding experiment was conducted by using CBN grinding wheel, and the results show that the defects on the ground surface of laser cladding Cr₃C₂/Ni based composite coating mainly include two categories: one is generated in the Ni based alloy which includes debris adherence, grinding traces, micro-crack and cracks; the other is the broken Cr₃C₂ particles and voids generated by the pullout of the broken Cr₃C₂. The debris adherence in the Ni based alloy is easier to form under the condition of smaller depth of cut and lower Cr₃C2 mass fraction in the coating. As the cutting depth increases, deeper grinding marks and micro-crack appear. The cracks form in the Ni based alloy when the mass fraction of Cr₃C₂ in the coating is higher than 20%. More voids are found on the ground surface when the mass fraction of Cr₃C₂ is 30%. Under the same grinding parameters, the Ra value of ground coating increases with the increase of the size of Cr₃C₂ particles and decreases with the increase of mass fraction of Cr₃C₂. However, the Ra value increases slightly when the mass fraction of Cr₃C₂ exceeds 20%. The experimental results reveal that there are fewer defects on the ground surface when the size of Cr₃C₂ is smaller and the wheel speed is higher.

Abstract:To extract efficient feature from mechanical vibration signal for fault diagnosis, a feature extraction method of double-scale fractal dimension based on variational mode decomposition (VMD) for vibration signal was proposed. Variational mode decomposition decomposed multi-component vibration signal into several intrinsic mode functions (IMFs) in different time scale by solving variational model iteratively. In a multidimensional measure space, the space occupied by a multivariate time series within a certain period can be measured by a multidimensional super body volume. Due to IMFs produced by VMD were regarded as multivariate time series, the multidimensional super-body volume was defined and calculated utilizing IMFs in multidimensional measure space. Then the log-log curve with time scale and super-body volume for vibration signal was acquired. According to fractal theory and the abrupt point in log-log curve, the log-log curve was segmentally fitted by least-squares linear fitting. Then, the double-scale fractal dimension feature for vibration signal was defined and acquired. The simulated signal results showed that the average relative error of fractal dimension estimation using VMD method was 4.71%, which improved the accuracy of fractal dimension estimation. The experimental results of planetary gearbox vibration signal indicated that the double-scale fractal dimension feature based on VMD could describe the fractal feature of mechanical vibration signal efficiently, and the accuracy of planetary gearbox fault diagnosis had reached 100%.

Abstract:To study the geometrical, kinematic characteristic and dynamic characteristic of Bennett unit array deployable mechanism, the decomposition method is used to disassemble a unit mechanism of the deployable mechanism into 4 spatial serial open-chain mechanisms, and according to its characteristic, the kinematic analysis model of Bennett unit array deployable mechanism is set up by the transformation of coordinates method combining with screw theory. And then, all spatial serial open-chain mechanisms are assembled by the virtual principle to build the dynamics analysis model by which the kinematic and dynamic of a 4×4 Bennett unit array deployable mechanism are studied, and simulations and experiments are carried out to testify the validity of this model. Results show that the deployable mechanism in the example can move smoothly and steady in their motion range. The farther the units on diagonal is away from the driving unit, the greater the variation range of angular velocity and acceleration of its driving angular will be. Since the generalized driving force moment changes gradually, it won’t cause a greater impact in the motion range. The simulation results, the experimental results and the model calculation results tend to be identical, and this proves that these kinematic and dynamic analysis models are accurate.

Abstract:Since the existing multi-label learning algorithms pay less attention to the problem of correlation and imbalance between label sets, this paper proposes a multi-label learning model based on label correlation and imbalance (MLCI). By coupling other label categories to consider the correlation among labels and reducing the imbalance ratio between labels of instances, the learning model is for each label category, and it is an ensemble classifier that combines the current class of binary imbalance classifier with multiple imbalanced classifiers coupled to other labels. In this paper, seven commonly used multi-label algorithms are used as comparison algorithms to classify the four open datasets of yeast, scene, emotions and CAL500. The experimental results show that the MLCI has obvious advantages in accuracy precision, ranking-Loss, macro-averaging AUC and micro-averaging AUC.

Abstract:Planetary hybrid electric buses usually have a great jerk while the drive mode switched. PID-based controller could not effectively ensure vehicle ride comfort during the mode switching process. Model predictive control(MPC) ,which can obtain optimal control sequences by online rolling optimization, is used to solve this issue, and a dynamic coordination control method based on MPC is proposed to start the engine. Based on the vehicle dynamic equations and vehicle historical data, the data-driven engine model and the closed-loop simulation model are set up in the Matlab/Simulink. Taking the start-up process of the engine as a constrained multi-objective optimization problem, the model predictive controller is designed according to the system state space equation and optimization problem. In the process of switching from the pure electric mode to the hybrid mode, the model predictive controller is compared with the traditional PID-based control method and without control. The simulation results demonstrate that under the premise of ensuring the dynamic performance of the vehicle, compared with the PID control and without control, during the mode switching process, the dynamic coordinated control method based on MPC can not only achieve the normal start of the engine, but also greatly reduce the peak jerk and also make the vehicle follow the target speed well.

Abstract:In order to study how to evaluate the dispersion of PVA fiber bundles uniformly, a variety of agitation and dispersion parameters were tested, and based on the theory of gray coexistence matrix, the dispersion evaluation method of PVA fiber was established. The dispersion effect of PVA fiber under different mixing factors, different stirring speed and different stirring blades was analyzed and the angular second moment of PVA fiber bundle and the entropy value of the line graph was plotted. The result shows that the dispersion of PVA fiber bundles can be evaluated by the method well, which provides a theoretical basis for the study of the dispersion uniformity of PVA fiber bundles.

Abstract:In this paper, the steady condition of conical spindle distribution and its dynamic response under the changing load is investigated. The lubrication model in spherical coordinate system is developed based on the particular structure, and from force analysis, the dynamic model of conical spindle distribution in axial and radial freedoms is also constructed. The static and dynamic lubricating performance including the shaft eccentricity and distribution gap height is obtained by solving the model with a numerical method. The result shows that the shaft eccentricity and distribution gap height oscillates intensely under the impact loading and gets back to a balance position in a short time. Such a self-adaptive feature of the lubrication performance of conical spindle distribution without requiring external adjustment is significant to ensure the reliability as the ball piston pumps are working.

Abstract:A three-stage improved point cloud registration ICP algorithm is proposed to deal with the problem of the low reconstruction accuracy, position trajectory loss caused by matching error in the process of inter-frame registration in visual simultaneous location and mapping (V-SLAM) of mobile robots. Firstly, the RANSAC algorithm is used to eliminate the mis-matching of RGB images in preprocessing phrase. Then, rough registration is accomplished by a double distance threshold method based on rigid body transformation consistency. Under a good initial pose, a dynamic iterative angle factor is used to complete the accurate registration of ICP. On the back end, a key frame screening mechanism combining the sliding window method and the random sampling method is introduced. And the robot pose is optimized by combining the general algorithm optimization (g2o) algorithm to construct a globally consistent map V-SLAM system. The standard point cloud model is used to verify that the proposed algorithm has a significant improvement in the accuracy of the registration compared experiment. The effectiveness of the proposed algorithm is validated by the map reconstruction experiment in real environment on the mobile robot. Finally, based on the experiment on TUM dataset, the experimental result shows that this algorithm can estimate the robot′s trajectory effectively.

Abstract:The problem, that the angle control of the mobile robot's visual target following system based on the traditional linear control law cannot satisfy the need of high efficiency and fastness so that the target is easy missed, is focused in this paper. A visual following method based on dynamic T-S fuzzy control is proposed. The HOG algorithm is used to detect the target and the target position vector is obtained by the camera model. Based on the T-S fuzzy control, dynamic processing is performed to further improve the response speed of angular error convergence. The simulation by MATLAB shows that the convergence time of the angle error is less than 0.4 second. Therefore, the improved fuzzy control method can effectively improve the response speed of the angle error, shorten the time of the angle error convergence, and make the follow-up system have better rapidity and adaptability. By experiment on the mobile robot platform, the convergence time of the angle error is less than 0.5 second.

Abstract:Parked car ventilation reduces the cooling time of the front windshield, improves the efficiency of the dehumidification in the cabin and effectively improves the defrosting performance of the windshield. Based on the CFD method and the Realizable k–ε turbulence model, this paper studies the cooling of the front windshield and the dehumidification performance in the cabin. First, the simplified model test is used to verify the accuracy of the simulation method and to testify that the parking ventilation can prevent frost from building up on the inside of a window. Second, the parking ventilation process is simulated to obtain the relationship between ventilation parameters, cooling and dehumidification effects, and flow field structures. The results show that the rate of flow of defrosting airflow is the key factor in terms of the cooling effect of the front windshield compared with all the other ventilation parameters. In addition to the high rate of flow of defrosting airflow, deflecting upward the airflow from the dashboard vent which are fully opened benefits the mixing and discharging of airflow.

Abstract:To obtain the optimal water spray velocities of on-line quenching system, a finite element model for simulating the on-line quenching process of large section π-shaped aluminum profiles was established based on Fluent and Workbench software platform. To determine the thermal boundary conditions in the simulation, methods in spray quenching experiments combined with inverse heat conduction were used to get the heat transfer coefficients under different spray water fluxes. The velocity, temperature, stress fields and residual deformation of extruded profiles during on-line quenching process under three schemes with different nozzles velocities were analyzed systematically. The results show that the heat transfer coefficient increases with the increase of spray water flux, and the time to reach the peak value is later. The simulated temperatures of feature points present corresponding changes with the measured ones and the relative error range is -0.7~7.8%, which verifies the accuracy of finite element model. For the initial quenching process scheme, a large thermal stress is formed at the joint position due to the non-uniform cooling of profile section, which leads to concave defect at the upper surface of profile. A relatively uniform temperature field can be obtained on the surface and middle section of profile by adopting the scheme 3, and the minimum residual stress and deformation can be achieved. The research methods and results are helpful to the design of nozzles velocities in the on-line quenching system for hollow aluminum profiles extrusion.