Search Results

Transmission gear whine noise is one of the main noise problems in powertrain NVH, which is caused by dynamic meshing force of gear pairs, it acts as transmission error. Due to the coupling effects of transmission gears, shaft, bearings and housing, it needs comprehensive management from many aspects to solve the problem of gear whine noise. Aiming at gear whine noise of a 4-speed AMT used in electric bus, the main noise sources is identified by using the order tracking analysis approach firstly. Secondly, gear misalignment and contributions of system deformation to the misalignment is analyzed by means of simulation tools, and the factor is taken into account in the subsequent gear modification design. At last, based on the improved Smith slice method, the calculation model of transmission error of helical gears is established.

With advantages of high efficiency and low cost, AMT (Automated Manual Transmission) has a very potential for auto-transmission, especially for heavy commercial vehicle, which has special requirements on low cost and easier operating. Recent years, some developments on multi-speed and electronic control, give us more confidence to consider AMT for heavy commercial vehicles, which offers a convenient and low cost way to multi-speed, and existed abundant gas resource for providing driven power. On the other hand, some technique issues challenge AMT in the application widely. For example, It is difficult to realize servo control for compressibility of gas. It therefore needs to find a way to realize the accurate control on auto-clutch operation system based on high quality system response. Accordingly, this work presents a system to realize hydraulic control powered with pneumatic power resource.

With the continuous improvement of the road condition, commercial vehicles get to be faster and more overloaded than before, which puts higher pressure on the vehicle braking system. Conventional friction braking has been difficult to meet the needs of high-power commercial vehicle. The auxiliary braking equipment will become the future trend for commercial vehicle. Hydraulic retarder is superior to secondary braking equipment. Previously hydraulic retarder research mainly focus on flow field analysis, the braking torque calculation, cascade system optimization and control methods for hydraulic retarder. The gas-liquid two-phase flow in working chamber is less researched. Based on this, this article discusses on the hydraulic retarder from two aspects. Firstly, this paper presents a block modeling method for hydraulic retarder system.

A good starting quality for AMT (Automated Manual Transmission) vehicles means that the vehicle is started quickly and smoothly on the premise of protecting powertrain system. The starting quality is closely related to the vehicle ride comfort and the service life of powertrain system. In order to improve the starting quality, a good idea is evaluating the starting process firstly and then optimizing the control strategy. However this method has two problems to be solved. The first one is how to define a series of objective criterions to judge the starting quality, and the other is how to select a suitable algorithm to optimize the starting control. This paper focuses on the starting quality assessment and optimization of AMT vehicles. First, the assessment criterions for starting quality are defined in detail from the control point of view and a corresponding assessment system is created.

According to the low efficiency of vehicle equipped with automotive transmission (AT) at launching conditions, the TCCs slip and lock up control technology was proposed and a TCC simulation model was established. The vehicle dynamics, torque fluctuation and efficiency were analyzed. Simulation results were obtained when taking the constant engine speed as the control target. The three-dimensional transient heat conduction finite element model using CFX was built. The slipping power was calculated and was converted to heat flux on the surface of TCCs friction plate model. The temperature of TCCs friction plate was obtained at different ATF oil temperature. Simulation results show that the TCCs slip and lock-up control technology at launching conditions can effectively solve the vehicles low efficiency problems caused by torque converter (TC). The maximum temperature rise of TCCs friction plate was 20°C.

Drag torque in multi-plate wet clutch consumes engine energy, but also has significant affect on synchronization process during shifting. The mathematical models of drag torque and shift synchronization process were established, and the results carried out by Matlab/Simulink simulation were compared with experiment results as well. It is demonstrated that the models are correct and accurate. The influences of friction pair gap in multi-plate wet clutch, cooling oil flow and properties of cooling oil under different temperature etc. on drag torque, shift synchronization time and energy were analyzed. The conclusions have certain guiding significance to the multi-plate wet clutch theoretical study and structural design as well as transmission system matching.

The general way to generate shifting schedule for a new developed vehicle is taking manual calibration way and doing test on the real vehicle that means a time-costing duty. Shift schedule auto-generation has been taken by more and more manufactures for its high efficiency. For auto-generation way, two groups of data set are important. The first is engine steady test data; and the other is drivability constraints defined by customers. Some useful results have been achieved in the field of passenger cars. But for off-road vehicle, there are some special requirements needed to consider, such as vehicle mass, 4WD function and etc. Four-wheel drive vehicles ask for more attraction for improving their performance considering their working in various driving environment. Automatic Transmission has been widely equipped in demanding off-road vehicles responding to the complex driving requirements for its advantage of easy operating.

The shift quality is one of the most important factors that affect the vehicle performances of comfort, ride and drivability for vehicles equipped with dual clutch transmission (DCT). Assessing the shift quality first and then optimizing shift control strategy and algorithm by the guidance of assessment results to improve the vehicle performance is a useful idea for the development of DCT and other types of automatic transmissions. This paper defines the shift quality assessment criteria in detail for DCT from the control point of view. A shift quality assessment system and a DCT vehicle model used for validation of assessment system are built with MATLAB/Simulink tools. Through the co-simulation of DCT vehicle model and assessment system, the shift quality control objectives, namely the expected control range of each assessment criterion, are determined, which provide reference and guidance for the optimization of DCT shift control.

After the analysis of shift quality evaluation methods of stepped automatic transmission, the evaluation indexes of shift quality have been established based on power-on up-shift of DCT (dual clutch transmission). Shift quality objective evaluation method of DCT based on TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) model is proposed. Taking the ideal shift process as reference, the shift quality evaluation model based on absolute ideal solution is developed. A comparison with the subjective evaluations shows that the proposed method is in good agreement with the traditional subjective evaluation method. The TOPSIS model provides a new shift quality evaluation approach and thinking for stepped automatic transmission.

To reach the goal of optimal performance match between engine and transmission, the dynamic characteristics of engine should be taken into consideration. In the paper, the dynamic torque and fuel consumption models of engine, described by a multi-layers feed forward neural network, were established. Based on that, the methods used to calculate the optimal dynamic and economical shift schedules with dynamic 3-parameters were put forward. The shift schedule with dynamic 3-parameters based on neural network model is proven to be superior to the shift schedule with only 2-parameters in both dynamic performance and fuel economy by the test.

In a traditional shift control strategy, the gear range is selected based on the throttle opening and the vehicle speed. The disadvantage of two-parameter based system is that the shift map is lack of adaptability in certain special conditions. The driving environment and the true intentions of the drivers are not fully taken into account by the shift control system. Therefore, improving the feasibility of the shift control strategy for the true intentions of the driver and driving environment is of great significance. Under braking conditions, Automatic transmission shift map with two parameters is unable to use engine braking effectively, which affects the drivability and safety of vehicles greatly. This paper presents a newly developed shift control strategy under braking conditions. First of all, the necessity of engine braking was analyzed.

Selection of gearshift point plays an important role in the field of automatic transmission technology, which directly affects the vehicle dynamic and economic performance, etc. In order to designing optimal gearshift strategies for conventional passenger vehicles equipped with stepped automatic transmission, in this paper, the vehicle power demand was defined under different environment, different driving intention and different vehicle operating conditions. Dynamic programming (DP) method is used to solve the optimal static gearshift decision sequence based on the simplified model of powertrain system. The drivability is respected by imposing an inequality constraint on the power reserve limit and the fuel economy is the objective function. Considering the change of vehicle additional load and road slope, the gearshift strategy based on power reserve is proposed.

With more and more countries proposing timetables for stopping selling of fuel vehicles, China has also issued a “dual-slope” policy. As electric vehicles are the most promising new energy vehicle, which is worth researching. The integration and control of the motor and gearbox have gradually become a hot research topic due to low cost with better performance. This paper takes an electric vehicle equipped with permanent magnet synchronous motor and two-gear automatic transmission without synchronizer and clutch as the research object.

Hydraulic retarders are extensively used in heavy-duty vehicles because of their advantages, such as their large braking torque and long continuous operating hours. They can reduce the vehicle velocity by converting the kinetic energy of a traveling vehicle to the thermal energy of the working fluid. The water medium retarder is a new type of hydraulic retarder with the characteristics of high power density and simple structure. It uses the engine's coolant as the working medium, and the heat is directly taken away by the vehicle cooling system. Therefore, the heavy-duty vehicle can achieve long-term continuous braking during the downhill process. One of the main functions of water medium retarder is driving downhill at a constant speed which determines whether the vehicle drives stably and safely. Therefore, studying the constant-speed control strategy during downhill driving is particularly important.

The thermal management system of the water medium retarder using engine coolant (water and ethylene glycol) as transmission medium, omits oil-water heat exchanger in the structure. When the hydraulic retarder is operated, the valve is connected with the retarder and water pump, and then the engine coolant enters the working chamber. The kinetic energy of the vehicle is converted into internal energy of the coolant, and the heat is discharged to the external environment through the engine thermal management system. The braking torque of the water medium hydraulic retarder is determined by the water medium flow rate in the working chamber. The smaller the valve opening degree, the greater the braking torque and the faster the heating transmission fluid. Small valve opening is not conducive to the loss of heat. It will affect the normal working of the engine and hydraulic retarder.

This investigation presents a methodology to develop and optimize shift process control strategy to improve shift quality as perceived by drivers during power-on upshift events for Dual Cultch Transmission (DCT) vehicles. As part of the first study, the main factors affecting shift quality during shifting process under typical working conditions are analyzed. And taking the power-on upshift as example, dynamic model of DCT shifting process is build. An Integrated control strategy is proposed for power-on upshift, which during torque phase slipping revolving speed controller is adapted to harmonically control two clutches power switching process, and during Inertial phase engine torque is regulated to synchronize with the value of target gear while holding the oncoming clutch pressure. Oncoming clutch oil pressure gradient in torque phase and engine torque reducing target decrement in inertial phase are chosen as controlled quantity.

Improvement of shift quality evaluation has become more prevalent over the past few years in the development of automatic transmission electronic control system. For the problems of the subjective shift quality evaluation that subjectivity is too strong, the standard cannot be unified and the definition of the objective evaluation index is not clear at present, this paper studies on the methods of objective evaluation of shift quality based on the multi-hierarchical grey relational analysis. Firstly, objective evaluation index system is constructed based on physical quantities, such as the engine speed, the longitudinal acceleration of the vehicle and so on, which broadens the scope of the traditional objective evaluation index further.

The shifting process always activates some changes of noise quality for its transient characteristics, especially for non-powered-shift transmissions, with which the power from engine is intermitted during the shifting period, such as Manual Transmission (MT) and Automated Manual Transmission (AMT). This type of noise change should have a very close relationship with the status of engine directly. But the essential reasons and how to estimate the noise have not been explored before. Therefore there is no clear understanding upon it and no formal methods yet described in the literature. The present study focuses on the phenomenon and makes effort to build reasonable research methods based on vehicles equipped with AMT. Furthermore, the metrics for assessing the noise has been developed with several different experiments and Support Vector Machines (SVMs) technique.

Gear-shift process of automatic transmission (AT) can be achieved with hydraulic control system which operates clutches or brakes' engagement or disengagement. According to the state of engagement elements, gear-shift process can be divided into torque phase and inertia phase. This article analyses gear-shift process of automatic transmission with the lever analogy and got the variation of the transmission's output torque. Then, the control principle of clutch to clutch shift is studied. This article takes power on up shift as study example and minimum of transmission output torque fluctuations during shifting as control target. Then this article analysis two control principles including inertia phase engine & transmission integrated control principle and entire shift process engine & transmission integrated control principle.

With the work medium of automatic transmission fluid (ATF), torque converter (TC) functions perfect performances such as smooth start, torque amplification, and the peak load restraint, and these properties makes the TC most suitable for off-road vehicles. An idea on the integration of TC and synchromesh gear box with their respective advantages is explored and introduced in this paper; here the system is named as Hydrodynamic Synchromesh Automated Transmission (HSAT). An automated control system makes the gear box as an automated manual transmission (AMT). HSAT takes TC as the starting device and accomplish shift process through AMT. The flow field optimized TC structure and the match calculation among the three parts of engine, TC and synchromesh gearbox; made this powertrain system has a good performance and the ability to reduce the fuel consumption.