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The hydraulic retarder is an important auxiliary braking device. With merits such as its high braking torque, smooth braking, low noise, long service life and small size, it is widely used on modern commercial vehicles. Transmission fluid of traditional hydraulic retarder is cooled by engine cooling system, which exhausts the heat directly and need additional energy consumption for the thermal management component. On account of the working characteristics of hydraulic retarder, this study designs a set of waste heat recovery system based on the Organic Rankine Cycle (ORC). Under the premise of ensuring stable performance of hydraulic retarder, waste heat energy in transmission fluid is recycled to supplement energy requirements for cooling system. First of all, a principle model, which is scaled down according to D300 retarder`s thermal power generation ration of 1:100, is established. Then through theoretical calculations, components' structural parameters of the ORC are determined.

The ever-growing number of interacting electronic vehicle control systems requires new control algorithms to manage the increasing system complexity. As a result, torque-based control architecture has been popular for its easy extension as the torque demand variable is the only interface between the engine control algorithms and other vehicle control systems. Under the torque-based control architecture, the engine and AT coordinated control for upshift process is investigated. Based on the dynamics analysis, quantitative relationship between the turbine torque of HTC and output shaft torque of AT has been obtained. Then the coordinated control strategy has been developed to smooth the torque trajectory of AT output shaft. The designed control strategy is tested on a powertrain simulation model in MATLAB/Simulink and a test bench. Through simulation, the shift time range in which the engine coordinated control strategy is effective is acquired.

Selective Catalytic Reduction (SCR) has become a mainstream approach to reduce diesel engine NOx emissions. Urea Water Solution (UWS) injection and interactions with mixers and exhaust gases affect the homogeneity of ammonia distribution at catalyst inlet and solid deposits formation on walls / mixer surfaces, therefore influencing SCR performance and durability. Computational Fluid Dynamics (CFD) is used to simulate an EU V compliant SCR system with a dual baffle mixer for heavy duty diesel engines. The modeling procedure is carried out by a multi-dimensional CFD code CONVERGE that includes transient urea transport processes in an exhaust flow configuration, detailed spray break-up, evaporation, wall-film, turbulence, and Conjugate Heat Transfer (CHT) models as well as an automated mesh generation approach. Locations of urea deposits and system pressure drop are predicted and validated against measurements, providing uniformity index (UI) predictions at the catalyst inlet.

Currently the downsizing of IC Engine has become the mainstream to meet fuel economy and emission regulations. It is required that higher power output while with lighter weight that is actually a daunting challenge for a common four-stroke IC engine, because it needs lots of new technologies and high manufacturing cost. For recent years the two-stroke opposed piston engine has drawn much attention in many developed countries for fundamental advantages itself. Double firing frequency means the increased power density brings about smaller engine size and lighter weight. However, the low scavenge efficiency has been assumed the main disadvantage for a two-stroke engine for a long period, and adverse to combustion efficiency. The uniflow scavenging process was investigated by the transient CFD simulation for multiple Cases. The influence of port timing and exhaust back pressure on scavenging was analyzed for two different intake port layouts.

Path planning system, which is one of driver assistance systems, can calculate the driving paths and estimate the driving time through the road information provided by information source. Traditional path planning systems calculate the driving paths through Dijsktra's algorithm or A* algorithm but only consider the road information from electronic maps. It is not safe enough for operating vehicles because of the insufficient information of vehicle performance as well as the driver's willingness. This study is based on the Dijsktra's algorithm, which comprehensively considered vehicular active safety constraints such as road information, vehicle performance and the driver's willingness to optimize the Dijsktra's algorithm. Then the path planning system can calculate the optimal driving paths that would satisfy the safety requirement of the vehicle. This study used LabVIEW as a visual host computer and MATLAB to calculate dynamic property of the vehicle.

The intake and exhaust valve spring of a 12.7L heavy duty diesel engine was instrumented with torque/shear rosette type strain gages to measure torsional stresses applied on the springs under different engine operating conditions. The engine was tested with no load, partial load and full load conditions and the effect of engine brake switch loading operation on the springs is investigated. Additional measurement of the valve lift motion and the peak fire pressure values from exactly the same cylinder were conducted to better understand the exact timing of the forces applied on the spring. This study gave an insight to the design engineer to determine the dynamic safety margin of the spring under permissible torsional stress values and optimize the material type of the spring accordingly. Another achievement is to measure any possible unpredictable torsional stress values occurred during engine operation when the engine brake is turned on/off and correlate the CAE model.

The paper proposes a method to analyze a trade-off between IC engine and electric battery sizes which is the essential issue of plugin hybrid and range extended electric vehicle design. This method implies a set of maps to be elaborated from batch simulations of hybrid vehicle running a driving cycle. Said maps establish relationships between ICE power, fuel consumption, electric energy consumption, and driving range of a vehicle. From these, one can choose a combination of ICE power and battery energy content meeting specific requirements for fuel economy and driving range. Mathematical model of the vehicle and the hybrid powertrain adopted for driving cycle simulations is described. Besides vehicle dynamics and drivetrain’s powerflows, it addresses battery’s current and voltage restrictions, which define performance of an electric drivetrain and have to be taken into account when selecting ICE power.

In a typical mechanical product such as an automobile or construction machinery, it is important to identify deformation modes, for which experiments and analyses can result in significant improvements. It is also important to consider how to improve the structure with high rigidity by using a technique such as the strain energy method in conventional design and development. However, the abovementioned method often generates conflicting results with regard to weight saving and cost reduction of development requirements. Transfer path analysis (TPA) using the finite element method (FEM) is an effective way to reduce noise and vibration in the automobile with respect to these issues. TPA can reveal the transfer path from the input to the response of the output point and the contribution of the path, and to efficiently consider improved responses.

Recent years, electric vehicles (EVs) have been widely used as urban transit buses in China, but high costs and a dwindling driving distance caused mainly by relatively frequent usage rate have put the electric bus in a difficult position. Range-extended electric bus (REEbus) is taken as an ideal transitional powertrain configuration, but its efficiency is not so high. Besides, with less batteries to endure more frequently charging and discharging, the lifecycle of battery pack can also be shorten. Aiming at it, range-extended electric powertrains with diverse energy storage systems (ESSs) and proper auxiliary power unit (APU) control strategies are matched and compared to find most proper ESS configuration for REEbus through simulation, which is based on a 12 meter-long urban bus.

A new method for driving the hydraulic free piston engine is proposed. This method achieves the compression stroke automatically rather than special recovery system. Principle of hydraulic differential drive free-piston engine is analyzed and the control strategy of this novel hydraulic driving engine is also introduced. Then energy balance method is used to design the main parameters of the novel engine. High pressure and secondary high pressure of the hydraulic system are constrained by the combustion parameters and therefore parameters are analyzed. In order to verify the effectiveness of energy balance method, the mathematical model is established based on the piston force analysis and engine working principle. The transient results of dynamics are obtained through simulation. In addition, the effectiveness of the simulation is proofed by dimensionless analysis. It indicates that energy balance method realizes the basic performance of hydraulic free piston engine.

Based on BP neural network theory, a BP-PID control algorithm with strong self-learning and self-adapting ability is designed for the diesel engine speed governor. Nonlinear continuous functions can be approached with high precision by using this algorithm. The parameters of speed loop controller can be calibrated in real time through the BPPID algorithm. In order to verify the advantages of BP-PID control algorithm in reducing overshoot, increasing diesel engine dynamic characteristics and resisting disturbance, simulation model is built and experiments are carried out under initial condition, steady condition and condition with sudden load change. We compare the simulation results and the experiment results, and find they match each other. The results indicate that the transient speed regulation of the diesel engine can meet the requirements of stage power station by using BP-PID control algorithm.

The output power of a turbocharged diesel engine will decrease and the maximum torque point in the full load torque map will move backwards when the engine is operating at plateau.

Mobile Earth Moving Machinery like Skid-steer loaders have tight turning radius in limited spaces due to a short wheelbase which prevents the use of suspensions in these vehicles. The absence of a suspension system exposes the vehicle to ground vibrations of high magnitude and low frequency. Vibrations reduce operator comfort, productivity and life of components. Along with vibrations, the machine productivity is also hampered by material spillage which is caused by the tilting of the bucket due to the extension of the boom. The first part of the paper focuses on vibration damping. The chassis’ vibrations are reduced by the use of an active suspension element which is the hydraulic boom cylinder which is equivalent to a spring-damper. With this objective, a linear model for the skid steer loader is developed and a state feedback control law is implemented.

Construction equipment machines today benefits from hydraulic system due to high power density. And, the development of an excavator using “open-center system with spool valves”, in general, requires iterative hardware design tuning activities for optimized performance and fuel economy while matching operator’s commands. Instead of traditional hydraulic and multi-body dynamic simulation with an operator simulation model, this paper focuses on the methodology development of real-time simulation model for an excavator, including the hydraulic system of an excavator’s boom, arm, bucket, and travel as well as multi-body dynamic system. The real-time capability is realized by reducing unnecessary compressible units and achieving numerical stability at sudden pressure changes when valves open and close. The real-time simulation model has been verified later with an actual Volvo CE excavator machine, and the correlation was quite satisfactory.

In order to overcome hysteresis and dead zone problems caused by friction for the proportional solenoid valve, and improve rapidity and stability of the pneumatic system on hydraulic retarder, a closed-loop control strategy based on valve coil current was proposed. The high-frequency low-amplitude dither signal was introduced into the proportional solenoid valve. With the proper dither signal, the stick-slip motion of the valve core was transformed into a steady one, and its dynamic performance was improved. Consequently, response time of retarder was reduced during gear changing. The proportional valve coil current was measured as a feedback for a closed-loop control strategy. Combining with the closed-loop strategy, the PI control algorithm was adopted to make sure that valve current was in accordance with the target value. Pulse Width Modulation (PWM) signal was used for the driving of proportional solenoid valve.

The cooling system with two fans is generally driven by electrical motors in the small cars. Compared with the traditional cars, heavy duty trucks have the larger heat dissipation power of cooling system. The motors power consumption of dual fans will be larger and the two electrical motors will occupy a large space in the engine cabin. Hydrostatic drive refers to the cooling fan is driven by hydraulic motor, but it has the low transmission efficiency. According to the engine water temperature value and the actual working status of the hydraulic system, the actual speed of cooling fan can be controlled by the computer, which guarantees the normal working water temperature of the engine. Hydrostatic drive is generally applied to heavy vehicles, engineering machinery and excavators as driving source of cooling fan which contains the advantages of large output power, overload protection, continuous speed regulation and flexible space arrangements.

With the need for improvement in the fuel economy along with reduction in emissions due to stringent regulations, powertrain hybridization has become the focal point of research for the automotive sector. Hydraulic hybrids have progressively gained acceptance due to their high power density and low component costs relative to their electric counterpart and many different architectures have been proposed and implemented on both on and off-highway applications. The most commonly used architecture is the series hybrid which offers great flexibility for implementation of power management strategies. But the direct connection of the high pressure accumulator to the system often results in operation of the hydraulic units in high pressure and low displacement mode. However, in this operating mode the hydraulic units are highly inefficient. Also, the accumulator renders the system highly compliant and makes the response of the transmission sluggish.

Stationary (parking) brake is a very important and safety critical function in many classes of machines. The new transmissions and the “by wire” systems increase the criticality of the role of stationary brake, as it is also an emergency (secondary) brake, and it’s often used to hold the vehicle when the transmission is not locking the wheels. As an example, dual clutch and power-shift transmission gear systems, as well as hydrostatic transmissions under certain circumstances, are often unable to hold the vehicle stopped and this function is provided by the stationary brake. Due to the main need of having the brake actuated when vehicle is stopped, without any hydraulic and electric power, the brake configuration is normally a “negative” configuration, usually called “spring applied” because of the actuator configuration, but this configuration causes the brake actuation when de-energized, even in case of system failure.

In order to improve efficiency and increase the operation of electric vehicles, assistive energy regeneration systems can be used. A hydraulic energy recovery system is modeled to be used as a regenerative system for supplementing energy storage for a pure electric articulated passenger bus. In this study a pump/motor machine is modeled to transform kinetic energy into hydraulic energy during braking, to move the hydraulic fluid from the low pressure reservoir to the hydraulic accumulator. The simulation of the proposed system was used to estimate battery savings. It was found that on average, approximately 39% of the battery charge can be saved when using a real bus driving cycle.

To improve traditional heavy commercial vehicles performance, this paper introduces a novel hydraulic hub-motor auxiliary system, which could achieve auxiliary driving and auxiliary braking function. Firstly, the system configuration and operation modes are described. In order to achieve coordinating control and distribution of the engine power between mechanical and hydraulic paths, the paper proposes an optimal algorithm based on enhance of vehicle slip efficiency and the results show that displacement of hydraulic variable pump relates with the transmission gear ratio. And then the hydraulic pump displacement controller is designed, in which the feedforward and feedback strategy is adopted. Considering the characteristics of hydraulic hub-motor auxiliary system, a layered auxiliary drive control strategy is proposed in the paper, which includes signal layers, core control layers and executive layers.