Search Results

The utilization of the SLAM (Simultaneous Localization and Mapping) technique was extended from the robotics to the autonomous vehicles for achieving the positioning. However, SLAM cannot obtain the global position of the vehicle but a relative one to the start. For sake of this, a fast and accurate system was proposed to obtain both the local position and the global position of vehicles based on mono-SLAM which realized the SLAM by using monocular camera with a lower cost and power consumption. Firstly, the rough latitude and longitude of current position was obtained by using common GPS without differential signal. Then, the Mono-SLAM operated on the consecutive video frames to generate the localization and local trajectory and its accuracy was further improved by utilizing the IMU information. After that, a piece of Map centered in the rough position obtained by common GPS was downloaded from the Open Street Map.

In this paper, a new method for determining the forming limit diagram (FLD) of thin sheet metals, called DIC-Grid method, is proposed based on digital image correlation (DIC) technique. It's assumed that there exists one virtual grid with an initial diameter of 2.5mm, which is usually the same dimension as the grid in traditional circular grid analysis, close to the crack of specimen, and the limit strain point on FLD is determined by the deformation of this virtual grid. The DIC-Grid method has been compared with traditional circular grid analysis and the standard ISO/FDIS 12004-2 in Nakajima tests. The results show that the forming limit strains obtained by the newly proposed method are more stable and precise. Furthermore, DIC-Grid method can avoid the measurement error which exists in the circular grid analysis. Meanwhile, it overcomes the shortcomings of time-consuming data processing and non-applicable for unrealistic strain distribution in the method of ISO standard.

Vehicle and pedestrian detection technology is the most important part of advanced driving assistance system (ADAS) and automatic driving. The fusion of millimeter wave radar and camera is an important trend to enhance the environmental perception performance. In this paper, we propose a method of vehicle and pedestrian detection based on millimeter wave radar and camera. Moreover, the proposed method complete the detection of vehicle and pedestrian based on dynamic region generated by the radar data and sliding window. First, the radar target information is mapped to the image by means of coordinate transformation. Then by analyzing the scene, we obtain the sliding windows. Next, the sliding windows are detected by HOG features and SVM classifier in a rough detect. Then using the match function to confirm the target. Finally detecting the windows in a precision detection and merging the detecting windows. The target detection process is carried out in the following three steps.

In order to reduce high-frequency harmonic noise produced by the blower in the auxiliary system of a fuel cell vehicle (FCV), a narrowband active noise control (ANC) method instead of conventional passive mufflers is adopted since the blower demands clean air condition and expects good acoustic performance. However, in ANC practical applications, the frequency difference between reference signal and actual primary signal, i.e., frequency mismatch (FM), can significantly degrade the high-frequency performance of narrowband ANC system. In this paper, a new narrowband ANC system is proposed to compensate for the performance degeneration due to the existence of FM and improve noise reduction at high frequencies. The proposed system consists of two parts: the Filtered Error Least Mean Square (FELMS) algorithm filtering the primary signals at wide frequency range other than those at the targeted frequencies, and the FM removal algorithm proposed by Yegui Xiao.

In this paper, by analyzing multiple electro-hydraulic brake system schemes in detail, the idea of dual-motor electro-hydraulic brake system is proposed. As a new solution, the dual-motor electro-hydraulic brake system can actively simulate pedal feel, make the most of pedal power (from the driver), and reduce the maximum power output of each active power source remarkably, which is a distinctive innovation compared to most current electro-hydraulic brake systems. Following the proposed concept, a general research thought and method is conceived, and then a dual-motor electro-hydraulic brake system is designed. Finally, the simulation model is set up in AMESim software and its feasibility is simulated and verified.

Ti-alloy sheet is a high-modulus elastic-plastic material, about which the resilience in the cold-forming process is quite difficult to control. As a matter of fact, the procedure of cold-forming is composed of many cases such as tensile case and bending case. An expression of ultimate radius for bending-curvature is obtained based on tri-parameters elastic-plastic constitutive model. By classifying the cold-forming process, some typical cases of cold-forming are presented in this paper, and analytical solutions with a high precision of resilience for high-modulus elastic-plastic material such as Ti-alloy sheet under the different typical cases are obtained in this paper. The accurate analytical solutions of resilience for high-modulus elastic-plastic material presented in this paper will contribute to cold-forming process both in the mould-designing and optimizing of cold-forming procedure.

Target detection is essential to the advanced driving assistance system (ADAS) and automatic driving. And the data fusion of millimeter wave radar and camera could provide more accurate and complete information of targets and enhance the environmental perception performance. In this paper, a method of vehicle and pedestrian detection based on the data fusion of millimeter wave radar and camera is proposed to improve the target distance estimation accuracy. The first step is the targets data acquisition. A deep learning model called Single Shot MultiBox Detector (SSD) is utilized for targets detection in consecutive video frames captured by camera and further optimized for high real-time performance and accuracy. Secondly, the coordinate system of camera and radar are unified by coordinate transformation matrix. Then, the parallel Kalman filter is used to track the targets detected by radar and camera respectively.

A novel compound power-split hybrid transmission based on a modified Ravigneaux gear set is presented. The equivalent lever diagrams are used to investigate the electric operating modes for the hybrid powertrain, and then its dynamic and kinematic characteristics as well as efficiency characteristics are described in equations. A brake clutch mounted on the carrier shaft is proposed to enhance the electric driving efficiency for the hybrid transmission. Three types of electric operating mode are analyzed by the simplified combined lever diagrams and the system efficiency and torque characteristics for these electric operating modes are compared. A major influence on output torque of the hybrid transmission derived from the torque capability of motors and brake clutch is depicted.

In the hybrid brake system of electric vehicle, due to the limitation of the motor braking force when the motor is at high speed and the failure of the regenerative braking force when the motor is at low speed, there are three transitional conditions in hybrid braking: the hydraulic brake system intervenes the braking, the hydraulic brake system withdraws the braking and the regenerative braking force withdraws the braking. Due to the response speed of the hydraulic system is slower than that of the motor, there is a large braking impact (the derivative of braking deceleration) in the transitional conditions of hybrid braking, which deteriorates the smoothness and comfort in braking. Aiming at the impact caused by the poor cooperation between the hydraulic braking force and the motor braking force, a coordinated strategy of double closed-loop feedback and motor force correction is proposed in this paper.

In order to establish the correlation between objective and subjective evaluation of brake pedal feel for passenger cars, road tests of brake pedal feel were carried out and an evaluation method was proposed. In the road tests, subjective scores and objective measurements were obtained under the conditions of uniform and emergency braking. The objective measurements include pedal preload, low deceleration pedal force and travel, moderate deceleration pedal force and travel, brake response time and brake linearity. Using the theory of analytic hierarchy process (AHP), the design process of the evaluation method was established. Key setups including the hierarchical structure model, the judgement matrix and the score calculation method of objective measurements were described in detail. Then, the correlation between subjective and objective scores was analyzed. It can be concluded that the evaluation method is effective and it can be applied to brake pedal feel assessment and adjustment.

Ion current sensing, which usually employs a spark plug as its sensor to obtain feedback signal from different types of combustion in SI engines, may be applied to HCCI combustion sensing instead of a prohibitively expensive piezoelectric pressure transducer. However, studies showed that the ion current detected by a spark plug sensor is a localized signal within the vicinity of the sensor's electrode gap, being affected by conditions around it. To find out better and feasible ion probe positions, a 3D-CFD model with a detailed surrogate mechanism containing 1423 species and 6106 reactions was employed to study the effect of stratification on ion distribution in HCCI combustion. The simulation results indicate that the monitor probe 1, 8 and 9 are more stable and reliable than the others. IONmax and dIONmax are more accurate to estimate CA50 and dQmax respectively.

Similar laser welded blanks with same material and same gauge have been extensive applied in automobile body for improving the material utilization and extending maximum coil size. It is known that, for TWBs with dissimilar material and thicknesses, the difference of material properties and/or thickness of the welded blanks, change of the material properties in the weld seam and heat-affected zones (HAZ) as well as location and orientation of the weld seam are reasons for reduced formability. However, the plastic deformation capacity of TWBs is reduced even when the material and thickness are the same. The aim of this paper is to evaluate the deformation behaviors of similar laser welded joints. Uniaxial tensile of five laser welded joints, with 90°,60°,45°,30°and 0°weld orientations, were tested by using optical measurement-DIC (Digital Image Correlation). Strain /strain ratio distribution and evolution of each joint was analyzed and compared with base material.

An experimental study is presented on the evaporation of diluted droplet-laden two-phase jet flows within a heated air channel co-flow. In this study, n-heptane is pre-atomized by an ultrasonic nozzle to produce droplet cluster with a median diameter of about15μm, and a continuous cold air flow is applied to carry the fuel droplet cluster to emerge from a nozzle tube, producing a free turbulent jet of droplet stream. The droplet stream is then introduced as a central jet into a square-shaped channel with heated air co-flow for evaporation investigations. With flexibilities of the initial properties of droplet stream and surrounding conditions of channel flow, the axial evolution of droplet size is determined to characterize the evaporation behavior of n-heptane droplet stream under various boundary conditions. The equivalence ratios of droplet streams are varied by changing both the carrier-air flow rate and the fuel flow rate.

The weight of an exhaust system on a modern vehicle is increasing because of all kinds of reasons, like engine power's increasing, more catalysts for emission control and more NVH (Noise, Vibration and Harshness) performance requirements. After the engine starting, the exhaust system was not only bearing a cyclical load from the engine, which mainly causing the vibration of the exhaust system, but also the loads from the road, which was transferred through the wheels, the suspension system and the body. Because the exhaust system always worked in these bad conditions, its structural strength, durability and life-time were analyzed in the paper, by numerical simulation and physical correlation. By discretizing the exhaust system's CAD model, a finite element model was built. After restrict the finite element model as it in a real load condition, complete the structure stress analysis and Fatigue analysis of exhaust system's hanger with FEA analysis tools.

The control in transient conditions when hydraulic brake and regenerative brake switch mutually is the key technical issue about electric vehicle hybrid brake system, which has a direct influence on the braking feel of driver and vehicle braking comfort. A coordination control system has been proposed, including brake force distribution correction module and motor force compensation module. Brake force distribution correction module has fixed the distribution results in hydraulic brake force intervention condition, hydraulic brake force evacuation condition and regenerative brake force low speed evacuation condition. Motor compensation module has compensated hydraulic system with motor system, which has fast and accurate response, thus the response of whole hybrid system has been improved.

Accurate control of both the timing and quantity of injection events is critical for engine performance and emissions. The most serious problem which reduces the accuracy of the control operation in such systems is a time delay of the responsiveness for the opening and closing operation of the electromagnetic valve. Modern electronic control systems should be capable of driving high speed solenoid injectors at a very fast switch frequency with high efficiency and acceptable power requirements. In this paper, the dynamic characteristic of a high speed servo-hydraulic solenoid injector for diesel engine, with different driving circuits and control methods, is investigated. A pre-energizing control strategy based on a dual power supply is applied to speed up the opening response time of the injectors.

Disc brake squeal has always been a great challenge to the automotive industry. Based on the pin-on-disc system, a series of frictional squeal bench tests are carried out, which show significant time-varying characteristics on occurrence, sound pressure and frequency of frictional squeal. To investigate the generation mechanism of time-varying characteristics of frictional squeal, a four-degree-of-freedom (4DOF) lumped parameter model considering the time-varying tangential contact stiffness, the normal contact stiffness and the friction coefficient is established in this paper. Through both the system stability analysis and the transient response analysis, the time-varying frictional squeal is predicted successfully, and the generation mechanism and the key impact factors are also investigated in depth.

An adaptive sideslip angle observer based on discrete extended Kalman filter (DEKF) is proposed in this paper and tire-road friction adaptation is also considered. The single track vehicle model with nonlinear tire characteristics is adopted. The tire parameters can be easily obtained through road test data without using special test rig. Afterwards, this model is discretized and the maximum value of tire-road friction is modeled as the third state variable. Through the measurement of vehicle lateral acceleration and yaw rate, the tire-road adhesion coefficient can be timely updated. Simulations with experimental data from road test and driving simulator have confirmed that DEKF has very high accuracy. The convergent speed of DEKF relies on the magnitude of lateral excitation.

The vehicle system is actually a strongly nonlinear system with stochastic parameters. In this paper, the nonlinearities of suspension, tire and seat are analyzed, and the nonlinear dynamics model of driver-vehicle system with 8 degrees of freedom (DOFs) is built. The bifurcation and chaotic motion of the deterministic system under Sinusoid excitations considering the time delay between the front and rear tires are studied. Then, the stochastic feature of the equivalent stiffness and damping coefficients of suspension, tire and seat are assumed to be the normal distribution, and the nonlinear model with random parameters is obtained. The nonlinear dynamics of stochastic nonlinear driver-vehicle system is analyzed and compared through numerical simulation.

In the process of ABS control, the Anti-lock braking system (ABS) of the vehicle adjusts the wheel cylinder brake pressure through the hydraulic actuator so as to control the movement of the wheel. The high-speed on-off valve (HSV) is the key components of the Anti-lock braking system. HSV affects the performance of the hydraulic actuator and the valve response characteristics affects the Anti-lock braking system pressure response as well as braking effect. In this paper, the electromagnetic field theory and flow field theory of HSV are analyzed, and simulation analysis of electromagnetic field characteristics of HSV is done by ANSYS. Combined with the ANSYS analysis results, a precise physical model of HSV is constructed in AMESim. Meanwhile, the valve response characteristics are analyzed. Moreover, the influence of different wheel cylinder diameter and PWM carrier frequency on hydraulic braking force characteristics are analyzed.