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Technical Paper

Study on Comprehensive Evaluation Index of Front Collision Hazard of Intelligent Vehicle

Collision avoidance technology is one of the key areas in the longitudinal safety research of intelligent vehicles. For the research of collision avoidance system, the existing methods usually use the evaluation index based on time interval or braking process to carry out risk assessment. In order to overcome the shortcomings of the formulas for describing the longitudinal hazard degree established in most studies, such as great differences, inconsistent standards and weak normalization, a comprehensive evaluation method for the longitudinal hazard in front-impact scenarios is established. This method takes into account both the analysis of time interval and braking process, and considers the non-linear variation of the longitudinal hazard degree with the real-time distance and speed of two vehicles. It can describe the longitudinal hazard degree of vehicles in dangerous traffic scenarios.
Technical Paper

Steering Control Based on the Yaw Rate and Projected Steering Wheel Angle in Evasion Maneuvers

When automobiles are at the threat of collisions, steering usually needs shorter longitudinal distance than braking for collision avoidance, especially under the condition of high speed or low adhesion. Thus, more collision accidents can be avoided in the same situation. The steering assistance is in need since the operation is hard for drivers. And considering the dynamic characteristics of vehicles in those maneuvers, the real-time and the accuracy of the assisted algorithms is essential. In view of the above problems, this paper first takes lateral acceleration of the vehicle as the constraint, aiming at the collision avoidance situation of the straight lane and the stable driving inside the curve, and trajectory of the collision avoidance is derived by a quintic polynomial.
Technical Paper

Solution of the Failure of the Bearings in a Planetary Gear Train

The fracture of the retainer leads to the failure of the needle rolling bearings in a planetary gear train of a planetary gearbox. In order to solve this engineering problem, the kinematics and kinetics of the failed needle rolling bearings is analyzed with the analytical model and the numerical model. A simple mathematical model is pointed out to analyze the dynamic load of a needle rolling element in the failed bearings. The assembling position of the small sun gear is also found to influence the performance of the needle rolling bearings significantly and therefore a best scheme for modifying the structure of the planetary gearbox is pointed out based on the multi-object optimization theory to reduce the bearing load heavily. Based on the calculated work, a systematic method of choosing the proper bearings for planetary gearbox can be concluded.
Journal Article

Numerical Simulation on the Ventilation Cooling Performance of the Engine Nacelle under Hover and Forward Flight Conditions

The main objective of this work is to investigate, by means of numerical simulations, the performance of the engine nacelle ventilation cooling system of a helicopter under hover and forward flight conditions, and to propose a simplified method of evaluating the performance based on rotor downwash flow by taking the synthetical effect of engine nacelle, exhaust ejector and external flow of a helicopter into account. For the engine nacelle of a helicopter, an integrated model of the nacelle and exhaust ejector was set up including the domain of external flow. The unstructured grid and finite volume method were applied for domains and control equations discreteness, and the standard k-ε model was applied for solving turbulent control equations. Using the business CFD software, the flow field and the temperature field in the nacelle were calculated for single inlet scheme and double inlets scheme, total up to 9 schemes. The performance of the exhaust ejector was computed.
Technical Paper

Liquid Stream in the Rotary Valve of the Hydraulic Power Steering Gear

Generally, noise will occur during steering with the hydraulic power steering system (hereinafter HPS). The noise producing in the rotary valve takes up a big proportion of the total one. To study the noise in the control valve, 2-D meshes of the flow field between the sleeve and the rotor were set up and a general CFD code-Fluent was used to analyze the flow inside the valve. The areas where the noise may be occurred were shown and some suggestions to silence the noise were given.
Technical Paper

High Speed Optimal Yaw Stability of Tractor-Semitrailers with Active Trailer Steering

Most tractor-semitrailers are fitted with multi-axle trailers which cannot be actively steered, and such vehicles with an articulated configuration are inclined to exhibit instability such as trailer swing, jack-knifing, and rollover at high speed. Proposed in this paper is an optimal control of the yaw stability of tractor-semitrailers at high speed by applying an active trailer's steering angle. An optimal control algorithm is designed by employing a 3-DOF vehicle model in the yaw plane. The optimal linear quadratic regulator (LQR) approach is used with a cost function including sideslip angles, yaw rates of both tractor and trailer, and trailer's steering angle. The yaw stability at the high speed is also quantified by the dynamic performance measurements of lateral path deviation, hitch angle and rearward amplification (RA). The algorithm is evaluated by co-simulations using TruckSim and Matlab/Simulink softwares.
Technical Paper

Heat Transfer Enhancement in Stagnation Region of Aero-Engine Inlet Vanes due to Ejection Slot and Anisotropic Heat Conduction

Ice protection is important for aero-engine induction system, such as the inlet vanes. For the ice protection of such parts manufactured with low thermal conductivity polymer-based composite material, the combined heating method using interior jet impingement and exterior ejection film has certain advantages. The simulation model coupling CFD with solid heat conduction was developed and solved with the anisotropic thermal conductivities model to investigate the heat transfer enhancement in the stagnation region of aero-engine inlet vanes due to ejection slot and anisotropic heat conduction, which is related to the curved geometry, ejection slots and anisotropic heat conduction. The temperature distribution and heat flux ratio between the stagnation region on outside surface and the impingement region inside were calculated and analyzed for the configuration with different ejection angle and different materials.
Technical Paper

Hardware-in-the-loop Simulation for an Integrated Braking System

Comparing with traditional braking systems of automobiles, the brake-by-wire (BBW) system has a faster dynamic response and is more suitable for applications that facilitate regenerative braking. As the two main categories of BBW systems, the well-known electro-hydraulic braking system and electro- mechanical braking system are not compact enough and their fail-safe function has always been a worrying aspect. A new BBW system called integrated braking system (IBS) by employing the hydraulic multiplex method was proposed in recent years. The IBS implements power-assisted braking and active braking by means of just an integrated unit. It can certainly be used for ABS, ASR and ESC systems for building up and reducing brake pressure. Presented in the paper is a new structure of IBS, which is mainly composed of a motor, ball screw, master cylinder and four 2/2-way valves.
Technical Paper

Automatic Drive Train Management System for 4WD Vehicle Based on Road Situation Identification

The slip ratio of vehicle driving wheels is easily beyond a reasonable range in the complex and changeable driving conditions. In order to achieve the adaptive acceleration slip regulation of four-wheel driving (4WD) vehicle, a fuzzy control strategy of Automatic Drive Train Management (ADM) system based on road situation identification was proposed in this paper. Firstly, the influence on the control strategy of ADM system was analyzed from two aspects, which included the different road adhesion coefficients and the vehicle’s ramp driving state. In the meantime several quantitative expressions of relevant control parameters were derived. Secondly, the fuzzy logic control algorithm was adopted to design a road situation identification subsystem and a ramp driving state identification subsystem respectively. The former was based on the μ-S curve model, and the latter was based on the vehicle driving equilibrium equation.
Technical Paper

Aero-Engine Inlet Vane Structure Optimization for Anti-Icing with Hot Air Film Using Neural Network and Genetic Algorithm

An improved anti-icing design with film heating ejection slot and cover for the inlet part of aero-engine was brought out, which combines the interior jet impingement with the exterior hot air film heating and shows promising application for those parts manufactured with composite materials. A hybrid method based on the combination of the Back Propagation Neural Network (BPNN) and Genetic Algorithm (GA) is developed to optimize the anti-icing design for a typical aero-engine inlet vane in two dimensions. The optimization aims to maximize the heating performance of the hot air film, which is assessed by the heating effectiveness. The film-heating ejection angle and the cover opening angle are the two geometric variables to be optimized. Numerical model was established and validated to generate training and testing samples for BPNN, which was used to predict the objective function and find the optimal design variables in conjunction with the GA.
Technical Paper

A Nonlinear Slip Ratio Observer Based on ISS Method for Electric Vehicles

Knowledge of the tire slip ratio can greatly improve vehicle longitudinal stability and its dynamic performance. Most conventional slip ratio observers were mainly designed based on input of non-driven wheel speed and estimated vehicle speed. However, they are not applicable for electric vehicles (EVs) with four in-wheel motors. Also conventional methods on speed estimation via integration of accelerometer signals can often lead to large offset by long-time integral calculation. Further, model uncertainties, including steady state error and unmodeled dynamics, are considered as additive disturbances, and may affect the stability of the system with estimated state error. This paper proposes a novel slip ratio observer based on input-to-state stability (ISS) method for electric vehicles with four-wheel independent driving motors.