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Although autonomous driving technology has become an emerging research focus, safety is still the most crucial concern when autonomous vehicles leave research laboratory and enter public traffic. Direct yaw moment control (DYC), which differentially brakes the wheels to produce a yaw moment, is an important system to ensure the driving stability of vehicle under extreme conditions. Traditional DYC system must need to take into account driver’s intention and vehicle dynamics. However, for autonomous vehicle, no human is involved in driving process, and enforcing traditional DYC system may conflict with the demands of the desired path. Therefore, in this paper, a novel DYC system for autonomous vehicle is proposed to simultaneously suppress lateral path tracking deviation while maintaining autonomous vehicle stability at or close to the driving limits. In the hardware aspect, an integrated-electro-hydraulic brake (IEHB) actuator scheme is adopted.

The current global chassis control (GCC) frequently makes use of decoupled control methods which depend on driving condition partition and simple rule-based vertical force distribution, and are insufficient to obtain optimal vehicle dynamics performance. Therefore, a novel hierarchical global chassis control system for a distributed electric vehicle (DEV), which is equipped with four wheel driving/steering and active suspension systems, is developed in this paper. The control system consists of three layers: in the upper layer, the desired forces/moments based on vehicular driving demands are determined; in the middle layer, a coordinated control method of longitudinal/lateral/vertical tire forces are proposed; in the lower layer, the driving/steering/suspension control is conducted to realize each distributed tire force.

The high temperature tribology issue for uncooled Low Heat Rejection (LHR) diesel engines where the cylinder liner piston ring interface exceeds temperatures of 225°C to 250°C has existed for decades. It is a problem that has persistently prohibited advances in non-watercooled LHR engine development. Though the problem is not specific to non-watercooled LHR diesel engines, it is the topic of this research study for the past two and one half years. In the late 1970s and throughout the 1980s, a tremendous amount of research had been placed upon the development of the LHR diesel engine. LHR engine finite element design and cycle simulation models had been generated. Many of these projected the cylinder liner piston ring top ring reversal (TRR) temperature to exceed 540°C[1]. In order for the LHR diesel to succeed, a tribological solution for these high TRR temperatures had to be developed.

Particle Number (PN) have already been a big issue for developing high efficiency internal combustion engines (ICEs). In this study, controlled spark-assisted stratified compression ignition (SSCI) with moderate end-gas auto-ignition was used for reducing PN in a high compression ratio gasoline direct injection (GDI) engine. Under wide open throttle (WOT) and Maximum Brake Torque timing (MBT) condition, high external cooled exhaust gas recirculation (EGR) was filled in the cylinder, while two-stage direct injection was used to form desired stoichiometric but stratified mixture. SSCI combustion mode exhibits two-stage heat release, where the first stage is associated with flame propagation induced by spark ignition and the second stage is the result of moderate end-gas auto-ignition without pressure oscillation at the middle or late stage of the combustion process.

The hybrid simulation method is adopted to develop engine dynamic test bed based on eddy-current dynamometer. The hybrid simulation scheme of engine dynamic test bed is designed. The principle is discussed. Finally, the CAD method is used to design main parameters of engine dynamic test bed based on simulation ECE15 and US LA4-CH Driving Schedules by Shanghai Santana 2000 car. The results are compared to the actual test results on the chassis dynamometer. The hybrid simulation method is proved to be an efficient way by simulation and comparison.

This paper studies a control algorithm for fuel cell/battery city buses. The output power of the fuel cell is controlled by a D.C. converter, and the output ports of the converter and the battery are connected in parallel to supply power for the electric motor. One way to prolong service life is to have the fuel cell system to deliver a steady-state power. However, because of fluctuations in the bus voltage and uncertainness in the D.C. converter, the output power of the fuel cell system changes drastically. A closed-loop control algorithm is necessary to eliminate the errors between the output and target power of the fuel cell system. The algorithm is composed of two parts, the feed forward one and the feedback one. Influences of the bus voltage and D.C. efficiency are compensated automatically in the feedback algorithm by using a PI algorithm. The stability and robustness of the algorithm is analyzed.

The four-wheel-independent Electro-hydraulic Braking system (4WI EHB) is a wet type Brake-by-Wire system for passenger vehicle and is suitable for electric vehicle (EV) and hybrid electric vehicle (HEV) to cooperate with regenerative braking. This paper gives a review on the design concepts of the 4WI EHB from the following three aspects. 1. Hydraulic architectures. 2. Design concepts of the brake actuator. 3. Installation of the components on the vehicle. Simulations and experiments are carried out to further explore the performance of hydraulic backup and implicit hardware redundancy (IHR). A method to integrate the IHR with hydraulic backup without increasing the total amount of valves is proposed, making the IHR cost and weight competitive. By reviewing various design concepts and analyzing their advantages and drawbacks, a cost and weight competitive design concept of the 4WI EHB with good fail-safe and fault-tolerant performance is proposed.

The paper presents a new electromechanical brake system for vehicles using magnetorheological fluid. The brake system designed for the electric vehicle has some advantages over the conventional brake system. The brake system is made up of a brake disk, shells, magnetorheological fluid (MRF) and the electromagnets. The brake disk is immersed in the MRF whose yield stress changes as the applied magnetic field. The braking torque of this system can be linearly adjusted by the current in just a few milliseconds without the conventional vacuum booster. This system has a quick response and precise control performance with a low hysteresis. Besides, the system has adopted the original complicated structure to save space and cost. In this paper, the configuration of MRF brake types is described. The braking torques of the MRF brakes is derived based on the MRF theoretical model which is firstly raised. Some braking simulation based on the theoretical model is also shown.

With the advantages of free from engine vacuum, wheel cylinder pressure decoupled from the brake pedal and can be regulated individually and precisely, the brake-by-wire system has a huge application potential in vehicles, especially in electric vehicles (EV) and hybrid electric vehicles (HEV). Electro-hydraulic Brake system is the first approach towards brake-by-wire technology. This paper proposed a new compact EHB, aiming at decreasing the size, volume and cost without compromise of performance. The main components of the proposed EHB are pedal simulator, motor pump, accumulator and eight solenoid valves. An authentic model of the EHB and other key components of the brake system were established based on the test data from the test bench. A control algorithm using Round-Robin scheduling was presented to regulate the fluid pressure. Some parameters of the components were discussed to research their effects on system performance.

The effective matching of the exhaust mufflers and engines is an important measure to reduce the noise emission of running vehicles. Currently, the matching is based mainly on the steady state performance of engine. The muffler's influence on a vehicle's noise emission and sound quality under different running conditions is not generally considered. A comprehensive performance evaluation method is proposed to describe the muffler's influence on a commercial vehicle's noise emission, sound quality and exhaust back pressure under multiple working conditions. The weighted insertion loss and linearity coefficient were defined based on the test data of the exhaust noise under different engine loads and speeds. A comprehensive performance evaluation method was defined from the test data analysis of engine exhaust noise with different mufflers. Finally, the simulation results of the exhaust noise of a vehicle with different mufflers were compared with test data.

A life-cycle assessment (LCA) has been developed to help compare the economic, environmental and energy (EEE) impacts of converting coal to automotive fuels in China. This model was used to evaluate the total economic cost to the customer, the effect on the local and global environments, and the energy efficiencies for each fuel option. It provides a total accounting for each step in the life cycle process including the mining and transportation of coal, the conversion of coal to fuel, fuel distribution, all materials and manufacturing processes used to produce a vehicle, and vehicle operation over the life of the vehicle. The seven fuel scenarios evaluated in this study include methanol from coal, byproduct methanol from coal, methanol from methane, methanol from coke oven gas, gasoline from coal, electricity from coal, and petroleum to gasoline and diesel. The LCA results for all fuels were compared to gasoline as a baseline case.

The paper is focused on the research of the automotive magneto-rheological brake system whose braking force comes from the shear stress of magneto-rheological fluid under the condition of magnetic field. The MRF brake is designed for an electric passenger car to replace a conventional hydraulic disc-type brake. The braking torque of this system can be linearly adjusted by the current in just a few milliseconds with proper materials. Therefore this system has a quick response and precise control performance with a low hysteresis. Nowadays, most of the related research of MRF is about the construction of the prototype and the realization of the brake force. Main limitation of MRF brake lies in the braking torque cannot meet the actual needs and the power consumption may be too much if it is not well designed. The prototype introduced in the SAE Brake Colloquium-31nd Annual has been manufactured and assembled critically.

Electrical vertical takeoff and landing (eVTOL) vehicles for urban air mobility (UAM) are garnering increased attention from both the automotive and aerospace industries, with use cases ranging from individual transportation, public service, cargo delivery, and more. Distributed electric propulsion systems are their main technical feature; they determine vehicle size and propulsion efficiency and provide distributed thrust to achieve attitude control. Considering the intended role of eVTOL vehicles, ducted-fan systems are ideal choice for the propulsor, as the duct provides a physical barrier between the rotating blades and the human, especially during the take-off and landing phases. Key Technology Challenges of Electric Ducted Fan Propulsion Systems for eVTOL introduces the main bottlenecks and key enablers of ducted-fan propulsion systems for eVTOL applications.

Brake squeal is a complex dynamics instability issue for automobile industry. Closed-loop coupling model deals with brake squeal from a perspective of structural instability. Friction characteristics between pads and disc rotor play important roles. In this paper, a closed-loop coupling model which incorporates negative friction-velocity slope is presented. Different from other existing models where the interface nodes are coupled through assumed springs, they are connected directly in the presented model. Negative friction slope is taken into account. Relationship between nodes’ frictional forces, relative speeds and brake pressure under equilibrant sliding and vibrating states is analysed. Then repeated nodal coordinate elimination and substructures’ modal coordinate space transformation of system dynamic equation are performed. It shows that the negative friction slope leads to negative damping items in dynamic equation of system.

The reference path played a very important role in the parking schemes. In this paper, an arc tangent liked polynomial trajectory model is proposed, and an optimal trajectory is obtained for automatic parallel parking based on genetic algorithm, which ensures that the vehicle does not collide with obstacles or other vehicles during parking. The proposed algorithm has strong robustness because of that all the parameters of the vehicle and the parallel parking spaces are parameterized. Using the trajectory model with the vehicle and parking space parameters, a cost function with multi-constraints, were established for path planning. The start and end points of the planning trajectory are the actual starting point and the desired final parking point of the vehicle by choosing three parameters of the trajectory model appropriately. Simulation results illustrate the effectiveness of the proposed algorithm.

Prototype of a brake-by-wire (BBW) system named Distributed Electro-hydraulic Braking System (DEHB) has been developed. As a BBW system, DEHB is suitable to be used in electric vehicles (EV) and hybrid electric vehicles (HEV). Comparing to the ‘dry’ type distributed BBW systems such as Electro-mechanical Braking System (EMB) or Electric Wedge Brake (EWB), the ‘wet’ feature of DEHB brings benefits to system cost, installation, performance and reliability. In this paper, prototype of the DEHB was described. Based on its ‘wet’ feature, a new fail-safe control for DEHB was proposed. Two types of DEHB architectures that can perform the proposed fail-safe control were described. Superiority of the proposed fail-safe control and architectures for DEHB were examined and verified through simulations and HIL experiments, which helps DEHB to reach a high level of safety and reliability with reduced cost on electro/electronic redundancy.

Compared with conventional vehicles, electric vehicles (EVs) offer the benefits of replacing petroleum consumption and reducing air pollutions. However, there have been controversies over greenhouse gas (GHG) emissions of EVs from the life-cycle perspective in China’s coal-dominated power generation context. Besides, it is in doubt whether the cost-effectiveness of EVs in China exceeds other fuel-efficient vehicles considering the high prices. In this study, we compared the life-cycle GHG emissions of existing vehicle models in the market. Afterwards, a cost model is established to compare the total costs of vehicles. Finally, the cost-effectiveness of different vehicle types are compared. It is concluded that the GHG emission intensity of EVs is lower than reference and hybrid vehicles currently and is expected to decrease with the improvement of the power grid.

Brake squeal noise is studied in this paper by feed-in energy analysis. Based on the closed-loop coupling brake model, the computation method of feed-in energy is derived for the system squeal mode. The amount of feed-in energy can indicate the degree of squeal tendency of the brake system. Feed-in energy analysis can clearly reveal the influence of some structural parameters on brake noise, such as coefficient of friction, the geometric shape and stiffness of pads, and key substructure modal shape. It also can help to analyze the structure modification to eliminate brake squeal.

The dynamic properties of disc rotor play important role in the NVH performance of a disc brake system. Disc rotor in general is a centrosymmetric structure. It has many repeated-root modes within the interested frequency range and they may have significant influence on squeal occurrence. A pair of repeated-root modes is in nature one vibration mode. However, in current complex eigenvalue analysis model and relevant analysis methods, repeated-root modes are processed separately. This may lead to contradictory result. This paper presents methods to deal with repeated-root modes in substructure modal composition (SMC) analysis to avoid the contradiction. Through curve-fitting technique, the modal shape coefficients of repeated-root modes are expressed in an identical formula. This formula is used in SMC analysis to obtain an integrated SMC value to represent the total influence of two repeated-root modes.

Closed-loop coupling model, based on complex eigenvalue analysis, is one of the most popular and effective methods for brake squeal analysis. In the model, imaginary coupling springs are used to represent the normal contacting force between coupled nodes. Unfortunately, the physical meaning of these coupling springs was seldom discussed and there’s no systematic method to determine the value of spring stiffness. Realizing this problem, this paper, based on finite element model and modal synthesis technique, develops a new closed-loop coupling disc brake squeal model without introducing imaginary coupling springs. Different from the traditional model where two nodes at coupling interface are connected through a spring, these node-pairs in the new model are assumed to remain in tight contact during vibration. Details of the model, including force analysis, coordinate reduction and transformation and complex eigenvalue decomposition are given in this paper.