Integrated powertrain control for twin clutch transmissions
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Abstract:
In this thesis an integrated powertrain control for gearshifts on twin clutch transmissions is developed.
First, a detailed model of an automotive powertrain featuring a twin clutch transmission is developed in Matlab/Simulink®. This model includes detailed friction models for the twin clutch that enable an investigation into the effects of different friction materials on the
performance of the gearshift controller. The transmission model also includes detailed models of the synchronisers and thus allows a simulation of synchroniser-to-synchroniser shifts. A simplified phenomenological model, derived from a more complex non-linear model, is employed to model the hydraulic actuation of clutches and synchroniser. The thesis finds that the dependency of the friction coefficient on the sliding speed has an important influence on the gearshift quality and the performance of gearshift controller, while the absolute level of the
friction coefficient is less important.
Based on this powertrain model the key problems of gearshifts on twin clutch transmissions were identified and a control that overcomes these problems was developed. The first stage was to devise a gearshift control algorithm that handles single clutch-to-clutch shifts without a oneway
(freewheeler-, overrunning-) clutch. This basic gearshift control algorithm featured a control of clutch slip for the engine torque transfer and a control of engine speed through engine torque manipulation (plus clutch pressure manipulation for downshifts). In a second stage, an
optional transmission output torque control was developed that could be integrated in the basic control. The thesis shows that these control strategies are superior, in terms of shift quality, to conventional gearshift controls as used on planetary-type transmissions and are also robust
against variations in the powertrain parameters (including friction coefficient) and sensor noise. The control strategies developed for single clutch-to-clutch shifts were extended to handle double and other multiple gearshifts that take place in the same transmission half.
The thesis also investigates the other main part of gearshifts on twin clutch transmissions, the gear pre-selection. The thesis shows that, on power-on gearshifts, the torque reactions at the transmission output due to the gear pre-selection with conventional hydraulically actuated
synchronisers can be effectively compensated for by a simple manipulation of engine torque.Keywords:
Torque converter
Powertrain
Automatic transmission
Manual transmission
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Clutch-to-clutch shift technology is a key enabler for fast and smooth gear shift process for multi gear transmissions. However, conventional hydraulic actuation systems for clutches have drawbacks of low efficiency, oil leakage and inadequate robustness. Electromechanical devices offer potential alternative actuators. In this paper, a novel motor driven wedge-based clutch actuator, featuring self-reinforcement, is proposed. The design concept and physical structure are thoroughly described. Dynamic models for the actuation system and vehicle powertrain are validated by experiments. Upshift and downshift processes at different engine throttle openings, clutch clearances and friction coefficients are discussed. The results show that, the self-reinforcement ratio is tested as 9.6; at the same time, the shift quality is comparable to that of the conventional hydraulic actuated clutch in automatic transmissions in terms of the shift duration (about 1 s) and vehicle jerk (<10 m/s 3 ). Taking advantage of fast response of the actuation DC motor, the wedge-based actuator is robust dealing with uncertain clutch clearance and friction coefficient. Therefore, the wedge-based clutch actuator has potential to provide acceptable performance for clutch-to-clutch shift.
Powertrain
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Introduction.- Overview of the Traffic-Vehicle-Transmission System.- Mediating the Power Flow.- Power Conversion: Selecting the Ratios.- Matching Engine and Transmission.- Vehicle Transmission Systems: Basic Design Principles.- Design of Gearwheel Transmisions for Vehicles.- Specification and Design of Shafts.- Gearshifting Mechanisms.- Moving-Off Elements.- Design and Configuration of Further Design Elements.- Typical Designs of Vehicle Transmissions.- Electronic Transmission Control.- Computer-Aided Transmission Development.- The Automotive Transmission Development Process.- Transmission Manufacturing Technology.- Reliability and Testing of Automotive Transmissions.- References.- Index of Companies/Transmissions.- Index of Names.- Subject Index.
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Automatic transmission
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This paper presents the detailed model of a double clutch actuator with a suitable control algorithm.Firstly, there is an introduction into the theory of a double clutch transmission and the aim of this project.The simulation model with a Dymola R and a MATLAB R /Simulink R part is discussed.The library of a vehicle model with a highly detailed hydromechanical clutch is introduced, which includes models with different levels of detail.The modeling of the hydraulic and the mechanic parts of the clutch actuator is discussed, concentrating on the problem of determining the parameters of the actuator modules e.g., the hydraulic valves.Some parts could not be used from existing Dymola R libraries, in those cases, new models are created based on Modelica code.A translational lever is pictured with its source code.Furthermore the non-linear behavior of the clutch actuator and control design is described.To verify this model and the suitable closed loop controller, the algorithm is tested with an up-shift cycle in a vehicle model with a double clutch transmission.The simulation results are presented with a global view of the driver inputs, the speed, the torque of the vehicle model and the gear status.Additionally the local view of the clutch actuator is shown with the cylinder pressure, the clutch position and the clutch capacity (torque).Finally there is a summary and an outlook on the further development of this library.
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The flow of torque in a twin clutch transmission is investigated and the different phases of torque transfer between the two clutches are studied. In order to prevent torque backlash and intense wear in dry clutch plates, a proper clamp force regulation is used. A full vehicle simulation that includes vehicle and powertrain components is set up. A Fuzzy logic control system is found suitable for clamp force and engine throttle controls. For upshift and downshift cases, the design of controllers for the gearshift process is carried out by defining proper membership functions and Fuzzy rules using Matlab/SimulinkTM software. The effectiveness of the control system is investigated by simulating two upshift and downshift cases. Results indicate that the control system is successful in regulating the clutch clamp forces and the engine throttle in such a way that a smooth torque flow in the transmission is achieved in all cases.
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Based on a detailed dynamic model of an automotive powertrain containing a twin-clutch transmission, an integrated powertrain control for gearshifts is developed. The operation of this controller is demonstrated on the basis of simulation results for upshifts, downshifts, and multiple gearshifts taking place within the same half of the transmission. The control algorithm makes use of closed-loop control of clutch slip for a smooth transfer of engine torque with the aim of reproducing the operation of a one-way clutch. Further elements are a closed-loop control of engine speed through a combination of a manipulation of engine controls and clutch pressure. In addition, it is demonstrated that the control of transmission output torque during gearshifts can add robustness to the control and provides a means to manipulate directly the gearshift character. Finally, the dynamic effects of gear preselection through conventional hydraulically actuated cone-type synchronizers on the overall shift quality are discussed.
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A novel type of Clutch and Overrunning Clutch Transmission (COT) is presented in this paper. The transmission performs traction uninterruption and high efficiency. The structure layout of one typical COT with an overrunning clutch and a Wet Friction Clutch is proposed. A 6-degree of freedom dynamic model is built for the vehicle with an engine, the transmission, the semi-axis and the wheels in it. The performance of the powertrain system during shift is discussed. Simulation based on the control strategy has been developed. Bench tests based on the COT has been carried out during both upshift and downshift. The simulation results and the test results show that the control strategy makes quick and smooth shifts.
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Automatic clutch control is critical in automated manual transmission systems because clutch actions have a significant influence on the vehicle performance, including safety, comfort, reliability, and shifting quality. However, clutch control is a challenging problem due to nonlinearity of throw-out force and uncertainty in clutch wear. For precise position control of the clutch, this study proposes a control scheme using model predictive control method with the correction of clutch wear based on the estimation of resistance torque. First, a novel and detailed clutch model is introduced, mainly including a driven plate model and a diaphragm spring model. Next, through theoretical analysis of the clutch model and the experimental data of a real clutch, the characteristics of the nonlinear throw-out force are obtained with different clutch wear situations. Then, a reliable clutch actuator is designed, whose model is also built to analyze its dynamics. At last, an automatic clutch controller is designed, and in order to apply it in clutch control unit for real-time control, it is simplified to reduce the online computing burden. The results both of simulations and bench experiments show that the proposed control scheme has a satisfying control performance.
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