Search

Four pairs of prefabricated reinforced concrete slabs were designed, cast, cured, assembled and test to investigate the flexural performance of prefabricated underground thin-wall box RC structure. One traditional integrated slab specimen with same size, material and reinforcement was also cast and test for comparison purpose. Four rebar constructional forms were conceived to compare the ability of transferring tension force between two slabs. Symmetric two-points monotonic static load test were performed to attain their flexural performance. The test results indicates: the prefabricated RC slab can provide better deformability and ductility, but the flexural bearing capacity is lower, comparing with cast-in-situ integrated RC slab; steel rebar form at seam have some effect on the flexural bearing capacity of prefabricated RC slab.

Flexible Pad Laser Shock Forming (FPLSF) is a new microforming process using laser-induced shock pressure and a flexible pad. This process involves high strain-rate (~105 s-1) plastic deformation of metallic foils along with the hyperelastic deformation of the flexible elastomer pad over which the foil is positioned. This paper studies the influence of flexible pad on the shockwave propagation behavior and the plastic deformation of metal foil in FPLSF using finite element analysis. The effect of flexible pad materials such as silicone rubber, polyurethane rubber and natural rubber on the deformation of copper foils has been analysed in detail. An increase in crater depth is observed with the reduction in flexible pad hardness. However, it is found that there exists an optimum hardness of the flexible pad to achieve perfect hemispherical craters on metal foils, as bending of foils at non-deformed region is observed with softer pads whereas flattening of crater surface occurs with harder pads. The effect of flexible pad thickness on the foil deformation was analyzed at six different thickness levels: 300 μm, 600 μm, 900 μm, 1200 μm, 1500 μm, and 2000 μm. Similarly, there exists an optimum flexible pad thickness to maximize the crater depth and achieve the hemispherical shapes. Analysis of flexible pad thickness indicates that the pad thickness influences the elastic recovery of the flexible-pad and hence the plastic deformation of the metallic foils.

A simulation tool for proportional relay valve of commercial vehicle pneumatic EBS (Electronically controlled Braking System) has been developed using MATLAB/Simulink environment and validated by testing on hardware-in-the-loop test bench focused on its pressure hysteresis characteristic. The simulation and test results show that the simulation model for proportional relay valve characteristics is reasonable and reliable, and it can be used for hardware and control algorithm development of pneumatic EBS for commercial vehicles.

Because of the sensitive factors, such as the larger loads, higher mass center and relatively narrow tread in comparison with the height of heavy vehicles that have the poor dynamic rollover stability. This paper set of anti-rollover LQR control algorithm based on early warning. The model-based early rollover warning algorithm utilize the TruckSim® models and early warning reference model to predict the impeding vehicle rollover time in advance and told the driver the warning signals so that drivers had enough time to take appropriate measures to prevent vehicle rollover that called time to rollover (TTR), thereby greatly improving the vehicles active safety performance of the heavy vehicles. As to the anti-rollover LQR control algorithm, the principle was to use the optimal additional yaw moment obtained from the control algorithm and then made it reasonable impose the corresponding wheels by taking the moment distribution methods based on the differential braking for the purpose of reducing the risk of rollover. The simulation results show that the algorithm was presented in this paper can effectively reduce the lateral load transfer ratio and actively void the occurrence of rollover accidents.

In accordance with ECE-R-13 braking regulations limit line, a regenerative braking control strategy is proposed to improve the braking energy recovery. Based on a Electric Vehicle, the braking distribution method makes the front and rear axle braking force arbitrarily distributed which is more effective to improve the rate of energy recovery. Simulation results show that this braking force distribution method focuses on making the braking force distribute to the drive shaft to a maximum extent and can decrease the vehicle fuel consumption.

In the steer by wire system of vehicle, a joystick can instead of the steering wheel. A control algorithm based on variable steering ratio is developed on the basis of vehicle speed and joystick steering angle. By verifying the control algorithm with the vehicle model from CarSim, it shows that this proposed algorithm can effective carry out steering intention of drivers, which enhance the steer comfort in low speed driving and steer handling in high speed driving and effectively improve the vehicle maneuverability.

Due to the vehicle performance improvements, the requirements of active safety technology have been increasing. The quality of brake system became a significant safety factor in commercial vehicles on the roads. This paper aimed at developing a highly integrated single chip controller that allowed real-time sensor data acquisition as well as brake force calculation and distribution. The controller was verified by Matlab/Simulink real-time simulation and hardware-in-loop test.

In order to solve the problem of road feel feedback of vehicle steer-by-wire (SBW) system based on joystick, a road feel control strategy was established to analyze the road feel theory of traditional steer system, which included return, assist and damp control module. By verifying the computer simulation results with the control strategy from software of CarSim and Matlab/Simulink, it shows that the proposed strategy can effective get road feel in different vehicle speed conditions and could improve the vehicle maneuverability to achieve desired steering feel by different drivers.

This paper presents a full drive-by-wire vehicle named Urban Future Electric Vehicle (UFEV) and introduces the detailed design of its vehicle control unit (VCU). The LabVIEW and PXI solution is selected for the rapid prototyping of VCU, which also acts as a real-time test, measurement and control platform for UFEV. To address its unique features, the design and transition of specific driving modes are introduced. Experiments show that omnidirectional moving can be implemented accurately and reliably by using the proposed design.

A control strategy for pneumatic ABS(Anti-lock Braking System) of commercial vehicle has been developed and validated by combining with Trucksim simulation software and by using hardware-in-the-loop test bench for hysteresis characteristics compensation. The test results show that the ABS control strategy satisfies the control requirements for system hysteresis characteristics, and improve the performance of pneumatic ABS system for commercial vehicle effectively, thus vehicle active safety is increased.

Anti-lock braking systems (ABS) is a type of mechanical electrical system in which are used to prevent wheel locking of vehicle as a result of excessive actuation of the service braking system, especially on slippery roads. According to electric control unit (ECU) research requirement of ABS system, this paper introduce a hardware-in-the-loop simulation (HILS) test bench, which can through open and close loop test methods accomplish calibration the parameters of the inside ECU, performance evaluation and fault diagnosis and tolerance test, not only can shorten the development cycle, but also save research and development costs of ECU.

Rear-end collisions of low speed vehicles on the urban road are common accident scenarios. A judgment of safety distance is a crucial part of a rear-end collision avoidance system which relies on safety distance model. In order to solve the problems of traditional safety distance models, this paper proposes a new model to avoid rear-end collisions. The new model considers the braking performance of the host vehicle and the motion state of the heading vehicle. Then a rear-end collision avoidance system including the new model is established using a combination of CarSim with Simulink software. Three typical working conditions through the co-simulation is simulated for verifying the model. Simulation results show that the new model ensures rear-end collision can be avoided, meanwhile keeping a short relative distance that improves road efficiency.

A brake pad wear control algorithm used under uncritical braking conditions is proposed to reduce the difference in brake pad wear between the front and rear axles caused by the difference in braking force and the type of brake. The algorithm regulates the distribution of braking force within the limits of certain braking regulations according to the wear conditions of the brake pads while deceleration control still functions properly. Computer co-simulations of braking with Trucksim and Matlab/Simulink was performed in which vehicle models with equal brake pad wear, greater wear on the front axle and greater wear on the rear axle were used. The results show that the difference in brake pad wear between the front and rear axles can be reduced by distributing the braking force according to the wear conditions of the brakes when braking uncritically to reduce the time and cost needed in repair and maintenance.

This study aims the development of a control strategy of steer-by-wire automotive with joystick. This control strategy makes driver able to change or maintain the steering angle of road wheels of the vehicle by joystick, provides feedback force to the driver and offers variable steering ratio, variable force feedback and proper damping. The control strategy was mathematically modeled and implemented using the simulation tool Matlab/Simulink and tested to inspect its effectiveness. The result of the test proves the control strategy is effective and the performance of a joystick steering system can be comparable to a traditional steering wheel by applying this control strategy, indicating potential possibility of joystick-steered automotive.

The power battery state of charge (SOC) in electric vehicles is not easy to measure accurately or apply a sensor but the expense is increased. However the variable of SOC is great importance to control of electric vehicles. A power battery model is built by the Partnership for a New Generation of Vehicles (PNGV) model to estimate the state of SOC. In order to make a high accurate estimate for SOC value, an information fusion algorithm based on unscented kalman filter (UKF) is introduced to design an observer. The test results show that the observer based information fusion and UKF are effective and accuracy, so it is may apply it the electric vehicle control and observation.

Electric vehicles with four in-wheel motors have its inherent advantage to recover energy because all of its four in-wheel motors can generate electricity energy when braking. For the purpose of study the property of regenerative braking of four-wheel-drive electric vehicles, three traditional distribution strategies of traditional vehicles are adjusted based on the property of in-wheel-motor. A simulation model is established by using Matlab/Simulink and CarSim software, and the simulation is made based on UDDS and 1015 driving cycles. The simulation result shows that, the parallel distribution strategy has the highest regenerative efficiency and regenerative efficiencies of fixed proportion distribution strategy and ideal distribution strategy are almost the same.

Based on the character of the penetrated cracks in the sluice piers of a overflow dam, the reasons inducing cracks are investigated. The results of the finite element (FE) nonlinear analysis on a representative cracked sluice pier indicate that the current cracks will expend, and the piers need to be strengthened. Four strengthening schemes with prestressed anchorage cables are designed, and their effects are analyzed and compared with FE method, the best strengthening scheme is found.

A non-corrosion, high strength, light weight material – carbon fiber reinforced polymer (CFRP) is introduced to replace steel as cable system in long-span suspension bridge for improving loading efficiency, reducing maintenance cost, enlarging the span of suspension bridge. Because of the transverse weakness of CFRP, traditional cable saddle is not suitable. The contact forces between main cable and cable saddle slot under final state are investigated with a simplified analytical method. According to the mechanical characteristics of CFRP and the formulas deduced, the design suggestion of cable saddle for CFRP main cable of long-span suspension bridge are proposed.

The stiction of control valve is one of main causes which make control loop instable in the process industry. Now a number of studies on the diagnosis of control valves are based on stiction. It needs developing a proper method which can detect, quantify, and compensate stiction. A non-invasive method has been used into the fault diagnosis for stiction of pneumatic control valve. Firstly, a two-parameter data-driven model about stiction has been established, and on the basis of separable least squares method, combined with the global search algorithm to deduce the model identification method. Secondly, ellipse fitting method has been adopt to confirm whether the stiction existed, thus the stiction could be quantified, and on this basis, the stiction was compensated. So it improved the performance of control system. Thirdly, the validity of the method was confirmed by simulation.

We studied the feasibility of micromachining of silicon wafer using 200 W fiber laser of 1090 nm in wavelength. Irradiated area was observed and analyzed using scanning electron microscope and surface profiler. It was found that micromachining of silicon could not be carried out efficiently. Careful analyses revealed possible causes for the poor machinability: first, very weak plasma formed during the fiber laser-material interaction, leading to low evaporation or melt ejection; second, formation of large amounts of SiO2 resulted in expansion of volume. It is further demonstrated that the surface oxidation can be made use of for the purpose of surface texturing.

Poor surface properties of magnesium alloys limit their extensive use in many applications. Laser surface engineering can be used to enhance surface-related properties of Mg alloys, and the purpose of this paper is to study the effect of laser pulse duration on surface of AZ91D Mg alloy. After millisecond-pulse laser treatment, ripples and cellular/dendrite as well as nanoscale -Mg17Al12 precipitates in the -Mg matrix were found in the surface microstructure, moreover, the melt depth was more than 150 micron. After nanosecond-pulse laser treatment, craters of 10 to 50 micron in diameter were observed on the surface due to plasma expansion and melted matter ejection during local boiling process, and the melt depth was nearly 15 micron. However, femtosecond-pulse laser treatment produced various micro- and nano-structures within a very thin layer on the surface.

High thermal conductivity, along with good electrical and mechanical properties, makes aluminum nitride a very promising material for electronic packaging and substrates. Much work has been reported on the influence of additions and sintering aids on densification and thermal conductivity. In this paper, the influence of raw materials on the sintering behavior and thermal conductivity characteristics of pressureless-sintered AlN has been investigated. The highest thermal conductivity is 248W/m.K.

We employ excimer laser annealing for ohmic contact formation to n- and p-type GaN layers grown on sapphire substrates. The laser irradiation of the n-GaN layers led to increased nitrogen vacancies at the nitride surface, which promoted tunneling currents with a less resistive n-contact. For p-GaN layer, the laser irradiation increased the effective hole concentration that resulted in a reduced contact resistivity. The lowest specific contact resistance measured using the transmission line method was about $2.4 \times 10^{-7}$ and $3.2 \times 10^{-4}$ $\Omega$ cm2for n- and p-contacts, respectively. Laser irradiation also resulted in a comparatively good surface morphology as compared to rapid thermal annealing, which in turn improved the transmittance of contacts for light extraction from active layers. It was found out that both the electrical and optical characteristics of the p-GaN contacts exhibited a good thermal stability and an improved transmittance in the blue--green spectral range. An increased forward current with a reduced ohmic contact resistance in such high thermal stable contacts enable the fabrication of GaN light emitting diodes.

Laser texturing is extensively investigated for modifying surface properties. A continuous wave (CW) fiber laser (= 1090nm) was used to pattern a silicon wafer surface in ambient and O2atmosphere respectively. The O2gas stream was delivered through a coaxial nozzle to the laser spot. Characterization of the patterned features was carried out by surface profiling, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS or EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Formation of laser-induced silicon oxide sub-micron bumps was observed, which were analyzed and shown to cause changes in surface wetability and reflectivity.