Dual-clutch Transmission Vehicle Research Articles

Online adaptive identification of clutch torque transmissibility for the drivability consistency of high-performance production vehicles

Drivability in vehicles with a wet-type dual-clutch transmission (DCT) relies heavily on the precise torque transfer control of the clutch to efficiently distribute the engine torque to the wheels. However, the large variation in the clutch torque transmissibility caused by temperature and wear and the lack of torque sensors for the driveline in production vehicles are the two significant challenges that hinder accurate clutch control in wet DCT vehicles. Therefore, knowledge regarding clutch torque transmissibility is crucial for realizing the demanded clutch torque because it can help determine the required clutch pressure. Thus, in this study, an online adaptive identification algorithm for clutch torque characteristics is developed for high-performance vehicles with wet-type DCTs. The proposed algorithm estimates each clutch torque characteristic using the extended Kalman filter (EKF) based on a parameterizable model for the torque transmissibility curve, making it applicable to production vehicles. Further, the algorithm incorporates an adaptation law based on the Lyapunov stability theorem to compensate for uncertainties in the engine torque, thereby ensuring a robust identification performance regardless of the installed engine type. The estimation performance and effectiveness of the adaptive identification algorithm are experimentally validated using test vehicles with wet DCT.

Fault Detection Strategy for Fork Displacement Sensor in Dual Clutch Transmission via Deep Long Short-Term Memory Network

Detecting the fork displacement sensor fault is critical for ensuring the reliability and safety of a dual clutch transmission (DCT). In this paper, a deep learning method is proposed to monitor the state of the fork displacement sensor. Firstly, the fork displacement prediction algorithm is developed based on the deep long short-term memory (LSTM) network using the driving data of a DCT vehicle. Secondly, the synchronizer control system model is constructed to imitate the fork displacement sensor fault as the experimental vehicle works in normal condition and the collected data lacks of faulty sensor signal. Finally, the residual is obtained by comparing the predicted fork displacement and the measured sensor information. The sensor fault is detected as the residual exceeds the predetermined threshold. Results show the fork displacement prediction algorithm can accurately estimate the synchronizer position. And the fault detection method can detect the fork displacement sensor fault timely and accurately.

Analysis of the Influence of a Powertrain Mounting System on a Dual-Clutch Transmission Vehicle under Typical Working Conditions

The unsuitably designed powertrain mount may cause jittering and shrugging during the starting and shifting processes of the vehicle, which seriously affects the comfort of using the vehicle. However, the influence of mounts on vehicles has been neglected in previous studies. In view of the above problems, this study establishes a DCT vehicle coupling dynamic model, considering six degrees of freedom of the powertrain mount and the engine dynamic torque, nonlinear characteristics of a dual-mass flywheel, time-varying stiffness of gear systems, and other factors. Furthermore, the effect of mounts on the longitudinal dynamic characteristics of the vehicle is studied during the starting, shifting, and tip-in/tip-out process. The results show that under typical working conditions, the mount and its stiffness and damping affect the fluctuation frequency and amplitude of the jerk. When the torque of the vehicle transmission system changes greatly, such as under starting and tip-in/tip-out conditions, the mount has a great impact on the dynamic performance of the vehicle. Simultaneously, the engine torque fluctuation can act on the vehicle through the mount, which has an impact on the jerk of the vehicle. A comparison with vehicle test results reveals that the DCT coupling dynamic model can reflect the law of the effect of the mount on the vehicle performance and verify the rationality of the model. Under typical working conditions, when the influence of the mount is not considered in the vehicle dynamic’s modeling, there is a large error of the jerk between the simulation results and the actual situation. The results provide a reference for optimizing the parameters of the mount and improving the dynamic characteristics of DCT vehicles.

Adaptive model predictive control of dual clutch transmission shift based on dynamic friction coefficient estimation

The dynamic friction coefficient of a wet clutch affects the vehicle shift quality and changes with factors such as the friction plate abrasion and oil and friction plate temperatures. Herein, an adaptive control strategy for dual clutch transmission (DCT) shifting is proposed. Based on the experimentally obtained dynamic friction coefficient of a wet clutch with a definite service mileage, the dynamic friction coefficient of a wet clutch is estimated online, considering the current service mileage and the oil and friction plate temperatures, using the recursive least squares method. By establishing a linear time-varying model of the DCT powertrain and using linear time-varying model predictive control to design the upper controller, the optimal shift reference curves of the clutch pressure and engine torque are obtained. Thereafter, the clutches and engine track the optimal reference curves through lower-layer proportional–integral–derivative controllers. The co-simulation results obtained using Simulink and AMESim show that the proposed control strategy can achieve good shift quality. It can also adapt to changes in the dynamic friction coefficient caused by clutch abrasion and oil and friction plate temperatures and ensure the shift quality of DCT vehicle.

Modeling and Control Approach for Dual Clutch Transmission Vehicles Starting Process Based on State-Dependent Autoregressive With Exogenous Model

To solve the difficulties of modeling the starting system of dual clutch transmission (DCT) vehicles, a state-dependent autoregressive with exogenous variables (SD-ARX) model whose functional coefficients are approximated by sets of radial basis function (RBF) networks is proposed to describe the dynamic characteristics of DCT vehicles starting process in this study. The validity of this modelling approach is verified via a real vehicle test. On this basis, a nonlinear predictive controller based on SD-ARX model is designed. In addition, the physical constraints of this system, including control variables (change rate of engine torque and clutch torque) and state variables (engine speed and clutch speed), are also taken into account during the controller design process via limiting the relevant parameters in particle swarm optimization or setting saturation demand in control program. To verify the validity and merits of the proposed control approach, many sets of simulation analysis in different driving intentions are conducted. Simulation results shown that: the proposed control approach can well control the starting process of DCT vehicles and effectively reflect the demand of driver's intention; compared with the conventional control method, SD-ARX-MPC can improve the starting performance; the proposed approach is robust to a certain extent according to simulation results under changed starting conditions.

Fault-tolerant control of clutch actuator motor in the upshift of 6-speed dry dual clutch transmission

As the working hours of dual clutch transmission (DCT) increase, the probability of a fault occurring in the clutch actuator motor increases. If no fault-tolerant control is adopted after an actuator motor fault occurs, it will lead to shifting failure and even damage the actuator motor. This study devises corresponding fault-tolerant control strategies for 6-speed DCT vehicle when the actuator motor of one of the clutches malfunctions in the upshift process. In those strategies, once the actuator motor fails, the vehicle is designed to disengage the fault clutch and engage the no-fault clutch, after which the vehicle can be driven either in the current gear or in higher/lower gear by jumping upshift with single clutch depending upon the driver demand. This ensures that the vehicle maintains better power performance and fuel economy even after a fault occurs in one clutch actuator motor. Lastly, the strategies were verified in the DCT hardware-in-the-loop test bench.

Simulation, Experimental Testing and Optimization of Starting and Shifting Control Strategies of DCT Wet Dual Clutches with Respect to Sliding Friction

For starting and shifting processes of dual-clutch transmission vehicle, the combined starting control strategy for dual clutches is proposed to reduce temperature rise of clutch and the dynamics simulation model of starting and shifting is built. For the two different downshift modes during inertia phase, the work and power of sliding friction are comparatively analysed. The results can provide boundary conditions of heat source for thermal equilibrium analysis under two typical starting conditions. During the benchmark test, the extreme starting condition under full load and large gradient and the three typical shifting conditions are set. Then, the sliding friction test is executed. The transmitted torque of wet dual clutches and the speed of driving and driven plates of dual clutches are measured to calculate work and power of sliding friction, and the corresponding temperature rise of wet dual clutches is obtained. Furthermore, the heat generation and heat dissipation conditions under different sliding friction modes are analysed. The corresponding influences on clutch control and temperature rise of cooling oil are also discussed. Based on the simulation and test results, the thermal equilibrium of clutches is analysed. The evaluation indexes of sliding friction work are calculated, and then the starting and shift control strategies are optimized.

Research on DCT shifting torque control and a benchmark test

In this study, the working principles of Dual clutch transmission (DCT) are analyzed, the power switching rule for dual clutches during upshift and downshift are formulated, and the model of DCT shift dynamics is established. Subsequently, upshift/downshift control strategies and sliding friction power are simulated and analyzed. A benchmark shift control test is conducted on real DCT vehicles, and test results show that the effect of clutch torque control strategy coincides with actual vehicle control during the upshift process. However, this effect varies during the downshift process. Two different downshift methods are proposed on the basis of the study findings. Moreover, the influence of downshift control method on engine control is analyzed, and the DCT torque control strategy employed during downshift is optimized.

Data-Driven Predictive Gearshift Control for Dual-Clutch Transmissions and FPGA Implementation

During the gearshift management process, the shift time and the shift shock affect the shift quality (smoothness and efficiency) greatly. In this paper, a gearshift controller is designed using a data-driven predictive control technique to improve the shift quality of vehicles with a dual-clutch transmission (DCT). It is directly obtained from the input-output data of a DCT model constructed by the commercial software AMESim. In order to obtain an offset-free control for the reference input, a predictor equation is gained with the incremental input and outputs. The conflicting control requirements of a short shift time and a small shift shock are taken into account in the optimal objective function by smoothly tracking a selected proper reference trajectory and limiting the change rate of the actuator. Moreover, due to physical characteristics, the constraints of the actuator are explicitly considered in the problem formulation. Finally, the effectiveness of the proposed data-driven predictive controller is tested in the AMESim simulation model of a DCT vehicle. Aiming to pursue a real-time improvement of the hardware computing speed for the data-driven predictive controller, a novel scheme for implementing the designed controller based on a field-programmable gate array (FPGA) is proposed. Moreover, a rapid prototyping platform based on an FPGA and dSPACE is introduced for testing and verifying the computational performance of the proposed controller. The experimental results show that the designed gearshift control algorithm for gearshift has better performance in real time, and the control performance can be guaranteed in a real-time environment.

A New Hardware-in-the-Loop Test System for Electronic Control Unit of Dual-Clutch Transmission Vehicle

Hardware-in-the-loop simulation (HILS) is a scheme that incorporates some hardware components of primary concern in the numerical simulation environment. This paper discusses the implementation and benefits of using the HIL testing system for electronic control unit of dual-clutch transmission (DCT) vehicle.

Shifting Quality Evaluation System for Dual Clutch Transmission Vehicle

At present,subjective evaluation is mostly adopted for shifting quality evaluation,so it is easily influenced by the testing personnel,and the effects of the shifting process on other performances are hardly considered.Based on the vehicle of dual clutch transmission(DCT),with the comprehensive consideration of multiple factors including dynamic performance,economy,durability of transmission system and comfort,combining with shifting time,acceleration,jerk,energy density,etc,the shifting quality evaluation indexes are put forward.The relationship between subjective and objective evaluations of comfort is established through radial basis function(RBF) neural network,and the influences of different parameters on the network performance are examined,then the trend between training error and number of neurons and the difference between original data and training data are presented.Based on this,the shifting quality evaluation system is developed by using programming interface.The shifting process is simulated by combining with a driver's intention.The results show that the system developed can effectively eliminate the influence of subjective factor and increase the objectivity of shifting quality evaluation.

Modelling and simulation of a dual-clutch transmission vehicle to analyse the effect of pump selection on fuel economy

Positive displacement pumps are used in automotive transmissions to provide pressurised fluid to various hydraulic components in the transmission and also lubricate the mechanical components. The output flow of these pumps increases with pump/transmission speed, almost linearly, but the transmission flow requirements often saturate at higher speeds, resulting in excess flow capacity that must be wasted by allowing it to drain back to the sump. This represents a parasitic loss in the transmission leading to a loss in fuel economy. To overcome this issue, variable displacement pumps have been used in the transmission, where the output flow can be reduced by controlling the displacement of the pump. The use of these pumps in automatic transmissions has resulted in better fuel economy as compared with some types of fixed displacement pumps. However, the literature does not fully explore the benefits of variable displacement pumps to a specific type of transmission namely, dual-clutch transmission (DCT), which has different pressure and flow requirements from an epicyclic gear train. This paper presents an analysis of the effect of pump selection on fuel economy in a five-speed DCT of a commercial vehicle. Models of the engine, transmission, and vehicle are developed along with the models of two different types of pumps: a fixed displacement gerotor pump and a variable displacement vane pump. The models are then parameterised using experimental data, and the fuel economy of the vehicle is simulated on a standard driving cycle. The results suggest that the fuel economy benefit obtained by the use of the variable displacement pump in DCTs is comparable to the benefit previously shown for these pumps in automatic transmissions.

Design of the Intelligent Compensating Shifting Schedule and Its Application in Dual Clutch Transmission Vehicle

The double parameter shifting schedule (DPSS) of dual clutch automatic transmission (DCT) controled by vehicle speed and engine throttle opening,based on enine torque model,engine fuel model and gear ratios of DCT,is designed.In the hardware-in-loop simulation test,some unreasonable shifting phenoemnons such as frequent shifting in EUDC drive cycle and needless shifting in urgent braking condition are found.The reason of the unreasonable shifting phenoemnon is analyzed,then,the conclusion that the unreasonable shifting is mainly caused by the incorrect operation of the driver is presented,and the unreasonable shifting is hard to be avoided if the DPSS is used.To eliminate the improper shifting under certain driving conditions,an intelligent compensating shift schedule (ICSS) is devised on the basis ofsugenofuzzy logic.The ICSS is composed of the input parameters including throttle opening and its changing rate,output parameters including upshift and downshift compensating ratio,membership function and fuzzy control principle.The downshifting speed at a given throttle opening is obtained from multiplying the corresponding speed inferned from DPSS by the downshift compensating ration inferred from ICSS,but the upshifting speed is obtained from dividing the corresponding speed inferred from DPSS by the upshift compensating ratio inferred from ICSS.The final test results prove the ICSS can eliminate the improper shifting in drive cycle and braking condition,and the fuel economy is also improved.

Shift dynamics and control of dual-clutch transmissions

Shifts in a dual-clutch transmission (DCT) are realized by torque transfer from one clutch to another without traction interruption due to the controlled slippage of the clutches. The timing of engagement and disengagement of the two clutches is critical for achieving a smooth shift without engine flare and clutch tie-up. This paper presents an analytical model for the simulation, analysis and control of shift dynamics for DCT vehicles. A dynamic model and the control logic for the integrated vehicle have been developed using Matlab/Simulink as the simulation platform. The model has been used to study the variation in output torque in response to different clutch pressure profiles during shifts. Optimized clutch pressure profiles have been created for the best possible shift quality based on model simulation. As a numerical example, the model is used for a DCT vehicle to simulate the wide-open throttle performance. Vehicle launch and shift process are both simulated to assess transmission shift quality and validate the effectiveness of the shift control.