Browse Topic: Dual clutch transmissions
Dual Clutch Automatic Transmission (DCT) has the characteristics of light weight, fast shift speed and high transmission efficiency. Electric vehicles equipped with dual clutch transmission can effectively improve vehicle power performance and economy. Electro-hydraulic control system, as a key component of transmission, determines the quality of shift. In this paper, an electro - hydraulic control system is designed based on two - speed dry dual clutch transmission of electric vehicle. Firstly, the hydraulic components of the system were selected and calculated based on the vehicle parameters. Secondly, the electro-hydraulic control system of the dual clutch transmission was established according to the transmission control strategy and the matching hydraulic valve body assembly was designed. Then, the key components of the system were simulated to analyze their dynamic shift characteristics and response characteristics. Finally, through various tests, it is verified that the designed
Shift fork is a key shifting element in manual and dual clutch transmission for smooth operations of gear shifting. One of the main criteria for robust design of shift fork is stiffness symmetry. Stiffness symmetry ensures straight movement of sleeve onto hub and thus helps in achieving good shift quality. Stiffness symmetry also ensures equal load distribution across two or three pads of shift fork while in operation. In this paper, we intend to demonstrate finite element simulation driven design process to improve stiffness symmetry of shift fork. Various parameters affecting stiffness symmetry are analyzed through design of experiment and selected best range for optimum design of shift fork. Output of this study will be useful for improving any design of shift fork to meet different targets of stiffness symmetry for all automobile suppliers and manufactures
Synchronizers are shifting elements in transmissions with power interruption, such as manual transmissions (MT) and automated manual transmissions (AMT). Synchronizers are also used in dual clutch transmissions (DCT) for shifting the preselected idler gear in the load-free branch of the transmission. Electric drive units (EDU) mainly consist of a two-stage transmission combined with a high-speed electric motor. Synchronizers realize the power flow from an idler gear to a gear shaft of the transmission. Automotive transmissions are usually operated with lubricating oils in order to minimize friction and wear of the mechanical components. Lubricating oil has a major influence on torque losses and on vibration behavior of transmission components. Torsional vibrations of mechanical components in transmissions lead to natural vibrations with high impact forces and thus to high radiated airborne sound levels. This occurs in particular when hard surfaces impact and the components have a high
Demand for electrified vehicles is increasing due to increased environmental pollution regulations and interest in highly efficient vehicles. According to these demands, research on electrified vehicles equipped with Dual Clutch Transmission (DCT) has been actively conducted for the purpose of improving energy efficiency of electrified powertrain, maximizing acceleration performance, and increasing maximum speed. However, since DCT requires clutch to clutch shifting, it is difficult to control drive torque and slip speed using two clutch actuators and a power source input. In order to solve this, a study on a multivariable shift controller has been conducted. However, this study chose a heuristic planning method to control the two outputs. However, since the slip speed and drive torque are coupled, it is necessary to tune the reference for every shift scenario, as well as create unnecessary control inputs or degrade shift control performance. Therefore, this study proposes a reference
To address the difficulties in modeling the starting process of dual-clutch transmission (DCT) vehicles and poor adaptability of vehicles in complex driving conditions, this article proposes a new modeling and control strategy for the DCT starting system based on data-driven autoregressive moving average exogenous (ARMAX) modeling. Firstly, the DCT starting process is considered equivalent to the time series-related ARMAX model, and a data-driven ARMAX model could be obtained using input-output data relating to the starting process; also, the effectiveness of the data-driven ARMAX modeling technique is verified using the starting test of a real vehicle. Secondly, a data-driven adaptive model predictive control (A-MPC) strategy, which synthetically considers driving intention and clutch engagement status, is proposed. Finally, in order to verify the proposed control strategy, simulation analysis is conducted in different intentions; the results show that the proposed control strategy
The dual clutch transmission is one of the possible choices for electric vehicle drivelines. The basic principle and control mode of shifting of wet dual clutch transmission are introduced, and the dynamic process of shifting of wet double clutch transmission is studied. Combined with the dynamic model of the wet clutch engagement process, the difference between the dynamic characteristics of the dual clutch transmission modeling using the Coulomb friction model and the dual-clutch transmission model using the average flow model and the micro-convex contact theory is analyzed. The shift control strategy of the dual clutch transmission proposes a correction method to improve the shifting smoothness. Studies have shown that the torque response of the wet clutch has significant hysteresis, and the improved control algorithm can significantly improve the shifting smoothness of the wet dual clutch transmission. Based on the dynamic model of the wet clutch, the torque interruption of the
Today, the contribution of the transportation sector on greenhouse gases is evident. The fast consumption of fossil fuels and its impact on the environment have given a strong impetus to the development of vehicles with better fuel economy. Hybrid electric vehicles fit into this context with different targets, starting from the reduction of emissions and fuel consumption, but also for performance and comfort enhancement. Lamborghini has recently invested in the development of a hybrid super sport car, due to performance and comfort reasons. Aventador series gearbox is an Independent Shift Rod gearbox with a single clutch and during gear shifts, as all the single clutch gearbox do, it generates a torque gap. To avoid the additional weight of a Dual Clutch Transmission, a 48V Electric Motor has been connected to the wheels, in a P3 configuration, to fill the torque gap, and to habilitate regenerative braking and electric boost functions. This paper discusses the usage of a control
The following schematic diagrams reflect various methods of illustrating automotive transmission arrangements. These have been developed to facilitate a clear understanding of the functional interrelations of the gearing, clutches, hydrodynamic drive unit, and other transmission components. Two variations of transmission diagrams are used: in neutral (clutches not applied), and in gear. For illustrative purposes, some typical transmissions are shown
A novel magnetorheological fluid dual clutch (MRFDC) for electric vehicle transmission is proposed in this article. The structure was based on the MR fluid clutch and traditional dual clutch equipped on internal combustion engine vehicle. Therefore the MRFDC combines the advantages of MR fluid clutch and dual clutch transmission (DCT) to achieve high control accuracy and fast response. The structure of MRFDC was designed by Unigraphics (UG) three-dimensional (3D) modeling software. Then, finite element analysis (FEA) for magnetic field was conducted by ANSYS under different applied currents from 0.1A to 1A with 0.1A space to obtain the relation between the applied current and magnetic field. In this article, Herschel-Bulkley model is used to predict the MR fluid behavior because of the high shear rate of MR fluid. Finally, output torque of MRFDC can be estimated by calculus with geometric dimensions of MRFDC structure and rheological properties of MR fluid dependent on the magnetic
This paper examines the effect of pulse-and-glide (PnG) driving strategies on the fuel efficiency when applied on parallel HEVs. Several PnG strategies are proposed, and these include the electrical, mechanical, and combined PnG strategies. The electrical PnG strategy denotes the hybrid powertrain control tactics in which the battery is charged or discharged according to the power demanded while maintaining the constant vehicle speed. On the other hand, the mechanical PnG strategy denotes the powertrain control tactics in which the vehicle accelerates or decelerates according to the power load while minimizing the battery usage. The combined PnG strategy involves both electrical and mechanical strategies to find a balanced point in between them. Here, a tradeoff relationship between the fuel efficiency and the vehicle drivability related to the tracking performance of the desired target speed is revealed. In the assessment of the feasibility of applying each of the formerly mentioned
An online and real-time Condition Prediction system, so-called lifetime monitoring system, was developed at the Institute for Mechatronic Systems in Mechanical Engineering (IMS) of the TU Darmstadt, which is intended for implementation in standard control units of series production cars. Without additional hardware and only based on sensors and signals already available in a standard car, the lifetime monitoring system aims at recording the load/usage profiles of transmission components in aggregated form and at estimating continuously their remaining useful life. For this purpose, the dynamic transmission input and output torques are acquired realistically through sensor fusion. In a further step, the lifetime monitoring system is used as an input-module for the introduction of innovative procedures to more load appropriate dimensioning, cost-efficient lightweight design, failure-free operation and predictive maintenance of transmissions. This is based on damage-oriented operating
The reduction of CO2 emissions at vehicle level through the improvement of transmission efficiency represents the essential goal of transmission development engineers. New requirements, such as the recovery of the kinetic energy of the vehicle while coasting, the hybridization of drivetrains and autonomous driving, are challenges that can best be overcome with automatic transmissions. Dual clutch transmissions (DCT) with power-on-demand actuation systems offer a particularly efficient method of meeting the new requirements. However, many markets show vehicle applications with production volumes of less than 100.000 units per year. FEV’s new DCT family is conceived especially for customers in these markets. The re-use of proven subsystems which are already in series production results in a "business case" for applications with lower volumes also. This article introduces this transmission family
An MIT student-inventor's clutchless hybrid transmission concept aims to provide high-performance vehicles an energy-saving attitude without compromise. The concept mechanism uses an electric motor to fill the acceleration lag that occurs when a driver releases the throttle and engages the clutch. A second electric motor is used for quickly speed-matching the gears during the shift since there is no mechanical means to speed up the next gear before engaging it
Regenerative braking has been widely accepted as a feasible option to extend the mileage of electric vehicles (EVs) by recapturing the vehicle’s kinetic energy instead of dissipating it as heat during braking. The regenerative braking force provided by a generator is applied to the wheels in an entirely different manner compared to the traditional hydraulic-friction brake system. Drag torque and efficiency loss may be generated by transmitting the braking force from the motor, axles, differential and, specifically in this paper, a two-speed dual clutch transmission (DCT) to wheels. Additionally, motors in most battery EVs (BEVs) and hybrid electric vehicle (HEVs) are only connected to front or rear axle. Consequently, conventional hydraulic brake system is still necessary, but dynamic and supplement to motor brake, to meet particular brake requirement and keep vehicle stable and steerable during braking. Therefore, a complicated effect on the safety and performance of braking, mainly
This paper presents a methodology for the assessment of the NVH (noise vibration and harshness) performance of Dual Clutch Transmissions (DCTs) depending on some transmission design parameters, e.g. torsional backlash in the synchronizers or clutch disc moment of inertia, during low speed maneuvers. A 21-DOFs nonlinear dynamic model of a C-segment passenger car equipped with a DCT is used to simulate the torsional behavior of the driveline and to estimate the forces at the bearings. The impacts between the teeth of two engaging components, e.g. gears and synchronizers, generate impulses in the forces, thus loading the bearings with force time-history characterized by rich frequency content. A broadband excitation is therefore applied to the gearbox case, generating noise and vibration issues. The metric used to assess the severity of a specific test and to compare, at least qualitatively, the NVH performance related to different design parameters sets, is based on the RMS (root
As the number of fixed gear ratios in automatic transmissions continues to increase in the pursuit of powertrain system efficiency, particular consideration must continue to be focused on optimizing the design for shifting performance. This investigation focuses on the effect of shift time on the performance attributes of shift quality, durability, on schedule fuel consumption and enablers to further reduce shift time. A review of fundamental design features that enable reduced shift times in both planetary and dual clutch transmissions is presented along with key operating features of both the transmission and engine/prime mover. A lumped parameter metric is proposed to assess and compare the upshift controllability of new transmission architectures and powerflows using simple analysis. The durability of fast shift times during performance maneuvers are quantified through calculation of shifting clutch energy and power from analysis and form measurements on a powertrain dynamometer
A direct trajectory optimization approach is developed to assess the capability of a GTDI-DCT Powertrain, with a Gasoline Turbocharged Direct Injection (GTDI) engine and Dual Clutch Transmission (DCT), to satisfy stringent drivability requirements during launch. The optimization is performed directly on a high fidelity black box powertrain model for which a single simulation of a launch event takes about 8 minutes. To address this challenging problem, an efficient parameterization of the control trajectory using Gaussian kernel functions and a Mesh Adaptive Direct Search optimizer are exploited. The results and observations are reported for the case of clutch torque optimization for launch at normal conditions, at high altitude conditions and at non-zero grade conditions. The results and observations are also presented for the case of simultaneous optimization of multiple actuator trajectories at normal conditions
During the last years mechatronic systems developed into one of the biggest drivers of innovation in the automotive industry. The start of production of systems like dual clutch transmission, lane departure warning systems and active suspensions proves this statement. These systems have an influence on the longitudinal, steering and vertical dynamics of the vehicle. That is why the interaction on vehicle level is crucial for an optimal result in the fields of efficiency, comfort, safety and dynamics. To optimize the interaction of mechatronic systems, in this paper a new test rig concept for a complete vehicle is presented. The so-called Car-in-the-Loop-concept is capable of realistically reproducing the loads, which act on the powertrain, the steering and the suspension during a test drive. The resulting advantages are the possibility to exactly reproduce test procedures, the independence from weather conditions and a minimization of the risk of human injuries during testing of safety
Dry dual clutch transmission (DCT) has played an important role in the high performance applications as well as low-cost market sectors in Asia, with a potential as the future mainstream transmission technology due to its high mechanical efficiency and driving comfort. Control system simplification and cost reduction has been critical in making dry DCT more competitive against other transmission technologies. Specifically, DCT clutch actuation system is a key component with a great potential for cost-saving as well as performance improvement. In this paper, a new motor driven clutch actuator with a force-aid lever has been proposed. A spring is added to assist clutch apply that can effectively reduce the motor size and energy consumption. The goal of this paper is to investigate the feasibility of this new clutch actuator, and the force-aid lever actuator's principle, physical structure design, and validation results are discussed in details. A prototyping of the proposed system is
In this paper, a new algorithm for the off-line estimation of wet clutch friction parameters is proposed for automotive transmissions, motivated by the usefulness of such an algorithm for diagnosing the condition of the clutch and transmission fluid in service. We assume that clutch pressure is measured, which is the case in dual clutch transmissions (DCT). The estimation algorithm uses measured rotational speeds and estimated accelerations at the input and output sides of a clutch, measured clutch pressures, and a simplified dynamic model of clutch friction to estimate the viscous and contact components of clutch friction torque. Coefficient of friction data is generated using the contact friction torque. A Stribeck friction model is fit to the data, and parameters in the model are then calculated by applying linear least squares estimation. The proposed estimation algorithm is tested using the simulation of a powertrain utilizing a DCT, where the clutch friction model incorporates a
Dual Clutch Transmissions (DCT) for passenger cars are being developed by OEMs and suppliers. The driving force is the improvement in fuel economy available from manual transmissions together with the comfort of automatic transmissions. A dry clutch system (dDCT) is currently the subject of research, development, and production implementation. One of the key issues in the development of a dDCT is clutch durability. In dry clutches with current linings, above a critical temperature, the friction system starts to suffer permanent damage. In addition, the clutch friction characteristics are a function of the clutch interface temperature. Because a reliable, low-cost temperature sensor is not available for this application, the clutch control engineers rely on a good thermal model to estimate the temperature of the clutches. A thermal model was developed for dry dual clutch transmissions to predict operating temperature of both pressure and center plates during all maneuvers. The model is
The contribution presents a new structurally optimized 7-speed hybrid DCT for transverse applications. Advantageously the seven forward speeds can be provided with only two shafts. The space of the usually third shaft can be used for the electric motor or the mechanical reverse speed. This modular integration can be realized by using mostly identical parts for the components of the gear set and the transmission housing. The direct connection of the electric motor to the differential helps to avoid additional gear set loads and efficiency losses. Such modular transmissions will help in future to reduce development and production costs
The fuel economy benefits of Continuously Variable Transmission (CVT) technology have led to a steady growth in their adoption since the 1990's that is likely to continue despite the competition from Dual Clutch Transmission (DCT) & Automated Manual Transmission (AMT) technology. Even though CVTs provide a smoother driving experience due to their “shift-free” operation, general market feedback indicates some level of consumer dissatisfaction in the area of acceleration sound quality. This is particularly evident in the sub-compact and compact vehicle segments that feature small four cylinder engines with cost/weight limited sound packaging. The dissatisfaction with the acceleration sound quality is primarily linked to the non-linear relationship between engine RPM and vehicle speed that is inherent to CVTs and is often referred to as “rubber-band” feel. For this paper, a NVH driving simulator was employed to create several acceleration sounds with varying engine RPM versus vehicle
To meet the requirements of low fuel consumption, good driving performance, vehicle packaging constraint, and manufacturing feasibility, a new wet dual clutch transmission family has been developed by SAIC Motor. This paper will provide a design overview of the transmission architecture, main characteristics, key subsystems and control strategies. The paper will also provide an overview of the development process, and the fuel economy benefit to the vehicle. The transmission family adopts compact layout of gears and shafts, wet dual clutch, hydraulic system for actuation of clutch and forks, integrated parking system, integrated fork and synchronizer system, etc. To achieve compact package target, a coaxial dual clutch with integrated damper system, two countershafts system, and optimized layout of gear system are adopted. The technical features for low fuel consumption include waved clutch plates, targeted cooling of wet clutch, optimized gear ratios, optimized control strategies. The
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