265 research outputs found

    Efficiency optimization of the push-belt CVT by variator slip control

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    Continuously Variable Transmissions (CVT) are becoming increasingly popular in automotive applications. What makes them attractive is the ability to vary the transmission ratio in a stepless manner without interrupting the torque transfer. This increases comfort by eliminating the discrete shifting events and increases performance by choosing the most suitable transmission ratio for every driving situation. Using a CVT could potentially save more than 15% of fuel consumption compared to manually shifted vehicles. This figure however is never met, because of the internal losses in the CVTs in production today. If the losses in a CVT can be lowered, then the overall fuel economy of a CVT equipped vehicle will be improved with the same amount. With current CVTs ranging around 80% efficiency, an improvement of around 10% is possible compared to currently available CVTs if an optimal actuation and control system is used. This thesis is about the optimization of the control system of the CVT by using slip as the control variable. This is part of a larger project focussing on the entire actuation and control system. Also a CVT with Electro-Mechanically Pulley Actuation (EMPAct) is developed aiming to reduce the power consumption of the CVT actuation system. Combined, these two projects aim to improve the fuel economy of the CK2 transmission from Jatco with 10%. Models for the clamping forces and traction in the variator are compared. The continuous belt model is compared with a pushbelt model. A parameter study shows the influence of the model parameters on the outcome of the models. The output of the models are also compared to measured values. A nonlinear dynamic model for slip in the variator is derived. This model can be linearized in certain operating points. This model can be used for the design of a control system, simulation of slip in the variator or for analysis. Measurement of slip directly is not possible, therefore a good estimation method is needed. Several estimations of slip in the variator are compared. The position measurement of the pulley is used in the measurements shown in this thesis. Measurements on a beltbox testrig are given that clearly show a relation between slip and efficiency and slip and traction. This relation changes as a function of other parameters like speed, ratio, clamping force etc. Estimation of the efficiency potential of the pushbelt variator shows that a potential of between 5% for high torques and 20% for low torques exists. A slip control system is developed to show the possible efficiency improvement. First, a beltbox setup is used to test a simplified slip controlled variator. Ratio changing is not taken into account in this setup. After successful tests with this setup another setup is used that incorporates a Jatco CK2 transmission and an internal combustion engine. This test setup is more realistic, but therefore also more complicated to control. A gain scheduled approach is used to compensate for the slower actuation system. This system is then also applied to a testing vehicle

    Simulation and Optimization of Wet Double Clutch Transmission (DCT)

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    This work focused on the longitudinal 7-speed wet DCT that is used by some high performance sport cars due to its capability to handle high rpm and torque output engine. This capability is coming from the use of wet friction clutch which able to dissipate more heat generated by high torque engine in slipping clutch during engagement process. One of inefficiency comes from the use of clutch fluid which tends to stick the clutch pairs, causing the drag torque when the fluid sheared by the clutch pair that rotates with different speed after the gear preselects action. The other drawback is occurred in the manual shift mode when the next gear that automatically preselected by the TCU before the gear shift is unmatched to the next gear as wished by the driver. The research was done to overcome the explained wet DCT drawback by improving the gear preselect action strategy so-called the seamless gear preselect strategy. This new strategy is achieved by improving the software of control algorithm rather than the DCT hardware for cost efficiency through software in the loop (SiL) method. This new strategy was achieved by simultaneously activate the gear preselect action during the fast filling phase of the ongoing clutch hydraulic system. The new gear preselect strategy make the reduction of unnecessary drag torque that normally occurs in wet DCT after gear preselect action in steady condition. The state of the art focusing on the subject of DCT construction, empiric system modeling, objectification and optimization method that were presented using a simulation environment to prepare the virtual gear shift optimization. After the model is fully confirmed, the optimization of wet DCT gear shift using genetic algorithm method was explained to meet the optimization objectives including the shift qualities, the uninterrupted torque during gear shifting and the limited heat generated as losses energy. The new gear preselect strategy is superior particularly for manual gear shift mode. The proposed strategy was carefully prepared in regards to the capability of the particular wet DCT construction particularly the hydraulic valve and gear shift actuator structure, while this optimization was done on the software basis alone without any further modification on the hardware. The optimization result confirmed the new gear preselect strategy is possible to be adapted in the particular seven speed wet DCT.Die Arbeit hatte ihren Schwerpunkt auf dem 7-Gang-nassen-DKG, welches von einigen Hochleistungssportwagen genutzt wird aufgrund dessen Fähigkeit, hochdrehenden und drehmomentstarken Motoren standhalten zu können. Diese Fähigkeit liegt begründet in der Verwendung einer nass Doppelkupplung, die mehr Hitze abführen kann, welche in einem drehmomentstarken Motor durch Rutschkupplung beim Einkuppeln entsteht. Eine der Ineffizienzen beruht auf der Nutzung von Kupplungsflüssigkeit. Diese neigt dazu, die Kupplungspaare zusammenzukleben, welches ein Schleppmoment verursacht, weil das gescherte Öl des Kupplungspaares nach der Gangvorwahl mit einer veränderten Geschwindigkeit rotiert. Der weitere Nachteil liegt im manuellen Schalten, wenn der Gang, welcher automatisch von der TCU vorgewählt wurde, nicht dem vom Fahrer gewünschten Gang entspricht. Die Forschung wurde durchgeführt, um den geschilderten Nachteil der Nass-DKG zu eliminieren durch den Gangvorwahl Strategie verbessert die nahtlose-Gangvorwahl Strategie sogenannte. Diese neue Strategie wird dadurch erreicht, indem lediglich der Kontrollalgorithmus verbessert werden musste, und nicht etwa die DKG-Hardware, zum kosteneffizienten Zweck durch die Software in the Loop Methode. Diese neue Strategie wurde durch gleichzeitig erreicht das Gangvorwahl während der schnellen Füllphase der laufenden Kupplung Hydrauliksystem aktivieren. Darüber hinaus macht die neue Gangvorwahl Strategie, um die Reduzierung unnötiger Schleppmoment, das in nassen DKG erfolgt in der Regel nach der Gangvorwahl Aktion im stationären Zustand. Der Stand der Technik in Bezug auf Fokussierung auf die Themen DKG-Konstruktion, empirisches Modellierungssystem, Versachlichung und Optimierung wurde während einer Simulation vorgestellt, um die virtuelle Gang-Auswahl vorzubereiten. Weiterhin wurde die Fahrzeugbeschleunigung während der Gangwechsel als Simulationsergebnis bewertet, um die Spontanitäts- und Schaltkomfortwerte durch eine Objektivierungsmethode zu erhalten. Das neue Gangvorwahl-Strategie überlegen ist besonders für den manuellen Gangschaltmodus. Die vorgeschlagene Strategie wurde im Hinblick auf die Fähigkeit der DKG-Konstruktion, insbesondere des Hydraulikventils und der Gangschaltungsaktuator-Struktur, gewählt, während die Optimierung allein auf Softwarebasis ohne jegliche weitere Änderung an der Hardware durchgeführt wurde. Das Optimierungsergebnis hat bestätigt, dass die neue Gangvorwahl-Strategie geeignet ist zur Anwendung in der DKG

    Simulation and Optimization of Wet Double Clutch Transmission (DCT)

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    This work focused on the longitudinal 7-speed wet DCT that is used by some high performance sport cars due to its capability to handle high rpm and torque output engine. This capability is coming from the use of wet friction clutch which able to dissipate more heat generated by high torque engine in slipping clutch during engagement process. One of inefficiency comes from the use of clutch fluid which tends to stick the clutch pairs, causing the drag torque when the fluid sheared by the clutch pair that rotates with different speed after the gear preselects action. The other drawback is occurred in the manual shift mode when the next gear that automatically preselected by the TCU before the gear shift is unmatched to the next gear as wished by the driver. The research was done to overcome the explained wet DCT drawback by improving the gear preselect action strategy so-called the seamless gear preselect strategy. This new strategy is achieved by improving the software of control algorithm rather than the DCT hardware for cost efficiency through software in the loop (SiL) method. This new strategy was achieved by simultaneously activate the gear preselect action during the fast filling phase of the ongoing clutch hydraulic system. The new gear preselect strategy make the reduction of unnecessary drag torque that normally occurs in wet DCT after gear preselect action in steady condition. The state of the art focusing on the subject of DCT construction, empiric system modeling, objectification and optimization method that were presented using a simulation environment to prepare the virtual gear shift optimization. After the model is fully confirmed, the optimization of wet DCT gear shift using genetic algorithm method was explained to meet the optimization objectives including the shift qualities, the uninterrupted torque during gear shifting and the limited heat generated as losses energy. The new gear preselect strategy is superior particularly for manual gear shift mode. The proposed strategy was carefully prepared in regards to the capability of the particular wet DCT construction particularly the hydraulic valve and gear shift actuator structure, while this optimization was done on the software basis alone without any further modification on the hardware. The optimization result confirmed the new gear preselect strategy is possible to be adapted in the particular seven speed wet DCT.Die Arbeit hatte ihren Schwerpunkt auf dem 7-Gang-nassen-DKG, welches von einigen Hochleistungssportwagen genutzt wird aufgrund dessen Fähigkeit, hochdrehenden und drehmomentstarken Motoren standhalten zu können. Diese Fähigkeit liegt begründet in der Verwendung einer nass Doppelkupplung, die mehr Hitze abführen kann, welche in einem drehmomentstarken Motor durch Rutschkupplung beim Einkuppeln entsteht. Eine der Ineffizienzen beruht auf der Nutzung von Kupplungsflüssigkeit. Diese neigt dazu, die Kupplungspaare zusammenzukleben, welches ein Schleppmoment verursacht, weil das gescherte Öl des Kupplungspaares nach der Gangvorwahl mit einer veränderten Geschwindigkeit rotiert. Der weitere Nachteil liegt im manuellen Schalten, wenn der Gang, welcher automatisch von der TCU vorgewählt wurde, nicht dem vom Fahrer gewünschten Gang entspricht. Die Forschung wurde durchgeführt, um den geschilderten Nachteil der Nass-DKG zu eliminieren durch den Gangvorwahl Strategie verbessert die nahtlose-Gangvorwahl Strategie sogenannte. Diese neue Strategie wird dadurch erreicht, indem lediglich der Kontrollalgorithmus verbessert werden musste, und nicht etwa die DKG-Hardware, zum kosteneffizienten Zweck durch die Software in the Loop Methode. Diese neue Strategie wurde durch gleichzeitig erreicht das Gangvorwahl während der schnellen Füllphase der laufenden Kupplung Hydrauliksystem aktivieren. Darüber hinaus macht die neue Gangvorwahl Strategie, um die Reduzierung unnötiger Schleppmoment, das in nassen DKG erfolgt in der Regel nach der Gangvorwahl Aktion im stationären Zustand. Der Stand der Technik in Bezug auf Fokussierung auf die Themen DKG-Konstruktion, empirisches Modellierungssystem, Versachlichung und Optimierung wurde während einer Simulation vorgestellt, um die virtuelle Gang-Auswahl vorzubereiten. Weiterhin wurde die Fahrzeugbeschleunigung während der Gangwechsel als Simulationsergebnis bewertet, um die Spontanitäts- und Schaltkomfortwerte durch eine Objektivierungsmethode zu erhalten. Das neue Gangvorwahl-Strategie überlegen ist besonders für den manuellen Gangschaltmodus. Die vorgeschlagene Strategie wurde im Hinblick auf die Fähigkeit der DKG-Konstruktion, insbesondere des Hydraulikventils und der Gangschaltungsaktuator-Struktur, gewählt, während die Optimierung allein auf Softwarebasis ohne jegliche weitere Änderung an der Hardware durchgeführt wurde. Das Optimierungsergebnis hat bestätigt, dass die neue Gangvorwahl-Strategie geeignet ist zur Anwendung in der DKG

    High-performance control of continuously variable transmissions

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    Nowadays, developments with respect to the pushbelt continuously variable transmission (CVT) are mainly directed towards a reduction of the fuel consumption of a vehicle. The fuel consumption of a vehicle is affected by the variator of the CVT, which transfers the torque and varies the transmission ratio. The variator consists of a metal V-belt, i.e., a pushbelt, which is clamped between two pulleys. Each pulley is connected to a hydraulic cylinder, which is pressurized by the hydraulic actuation system. The pressure in the hydraulic cylinder determines the clamping force on the pulley. The level of the clamping forces sets the torque capacity, whereas the ratio of the clamping forces determines the transmission ratio. When the level of the clamping forces is increased above the threshold for a given operating condition, the variator efficiency is decreased, whereas the torque capacity is increased. When the level of the clamping forces is decreased below the threshold for a given operating condition, the torque capacity is inadequate, which deteriorates the variator efficiency and damages the pulleys and the pushbelt. Since this threshold is not known, the level of the clamping forces is often raised for robustness, which reduces the variator efficiency. The challenge for the control system is to reduce the clamping forces towards the level for which the variator efficiency is maximized, although the variator efficiency is not measured. Furthermore, avoiding a failure of the variator in view of torque disturbances and tracking a transmission ratio reference are necessarily required. Two state-of-the-art control strategies are presently used, i.e., safety control and slip control. These control strategies involve limitations that follow from the model knowledge and/or the sensor use that underlies the control design. For this reason, the objectives of the research in this thesis are oriented towards improvements with respect to the model knowledge of both the hydraulic actuation system and the variator, which is subsequently exploited in the control design of both components, to improve the performance. The resources of the control designs are restricted to measurements from sensors that are standard. A cascade control configuration is proposed, where the inner loop controls the hydraulic actuation system and the outer loop controls the combination of the inner loop and the variator. The elements of the cascade control configuration are the subject of the research in this thesis. For the hydraulic actuation system, modeling via first principles and modeling via system identification are pursued. Modeling via first principles provides a nonlinear model, which is specifically suited for closed-loop simulation and optimization of design parameters. A modular approach is proposed, which reduces the model complexity, improves the model transparency, and facilitates the analysis of changes with respect to the configuration. The nonlinear model is validated by means of measurements from a commercial CVT. Modeling via system identification provides a model set, which is subsequently used for the hydraulic actuation system control design. A model set of high-quality is constructed, which is achieved by the design of the identification experiments that deals with the limited signal-to-noise ratio (SNR) that arises from actuators and sensors of low-quality. The hydraulic actuation system control design is multivariable, which is caused by the interaction between the hydraulic cylinders that is inherently introduced by the variator. Stability and performance are guaranteed for the range of operating conditions that is normally encountered, which is demonstrated with the experimental CVT. A variator control design is proposed that deals with both the transmission ratio and the variator efficiency in terms of performance variables, where the transmission ratio is measured, while the variator efficiency is not measured. The variator control design uses the standard measurement of the angular velocities, from which the transmission ratio is constructed, as well as the standard measurement of the pressure. Essentially, the variator control design exploits the observation that the maximum of the transmission ratio and the maximum of the variator efficiency are achieved for pressure values that nearly coincide. This observation is derived from both simulations with a nonlinear model and experiments with the experimental CVT. This motivates the use of the pressure-transmission ratio map, although the location of the maximum is not known. For this reason, the maximum of the input-output map is found by a so-called extremum seeking control (ESC) design, which aims to adapt the input in order to maximize the output. A robustness analysis shows that an input side disturbance that resembles a depression of the accelerator pedal and an output side disturbance that resembles the passage of a step bump are effectively handled. Finally, the ESC design is extended with a so-called tracking control (TC) design, which enables that optimizing the variator efficiency and tracking a transmission ratio reference are simultaneously achieved. The variator control design that is composed of the ESC design and the TC design is evaluated with the experimental CVT. Simulation of a driving cycle shows that the final variator control design outperforms the conventional variator control design in terms of the variator efficiency

    Component control for the Zero Inertia powertrain

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    Combined numerical and experimental investigation of transmission idle gear rattle

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    Gear rattle is caused by engine torsional vibration (engine order response) imparted to the transmission components, further causing the gears to oscillate within their functional backlashes. These oscillations lead to the repetitive impact of gear teeth, which lead to noisy responses, referred to as gear rattle. The lack of in-depth research into the effect of lubricant on gear rattle has been identified as a deficiency in the previous research in rattle. The aim ofthe current work is to address this shortcoming. The thesis outlines a new approach in investigating the problem of idle gear rattle. The approach is based on the assumption that under idling condition the teeth-pair impact loads are sufficiently low and the gear speeds are sufficiently high to permit the formation of a hydrodynamic lubricant film between the mating gear teeth. This film acts as a non-linear spring-damper that couples the driver and the driven gears. A torsional single-degree of freedom model is used in the development of the theory. The model is then expanded into a seven-degree of freedom torsional model and finally into an Il-degree of freedom model that also includes the lateral vibrations of the supporting shafts. The Il-degree of freedom model is based on a real life transmission that is also used in experimental studies to validate the model. It is found that lubricant viscosity and bearing clearance (lubricant resistance in squeeze) play important roles in determining the dynamics of the system and its propensity to rattle. At low temperatures, the lateral vibrations of the shafts, carrying the gears interfere with the gear teeth impact action. The severity of rattle is determined by the relationship between the entraining and squeeze film actions of the hydrodynamic film. When the latter dominates, the system can rattle more severely. The numerical results are found to correlate well with the experimental findings obtained from vehicle tests in a semi-anechoic chamber and also with those from a transmission test rig in the powertrain laboratory

    Magneto-Rheological Actuators for Human-Safe Robots: Modeling, Control, and Implementation

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    In recent years, research on physical human-robot interaction has received considerable attention. Research on this subject has led to the study of new control and actuation mechanisms for robots in order to achieve intrinsic safety. Naturally, intrinsic safety is only achievable in kinematic structures that exhibit low output impedance. Existing solutions for reducing impedance are commonly obtained at the expense of reduced performance, or significant increase in mechanical complexity. Achieving high performance while guaranteeing safety seems to be a challenging goal that necessitates new actuation technologies in future generations of human-safe robots. In this study, a novel two degrees-of-freedom safe manipulator is presented. The manipulator uses magneto-rheological fluid-based actuators. Magneto-rheological actuators offer low inertia-to-torque and mass-to-torque ratios which support their applications in human-friendly actuation. As a key element in the design of the manipulator, bi-directional actuation is attained by antagonistically coupling MR actuators at the joints. Antagonistically coupled MR actuators at the joints allow using a single motor to drive multiple joints. The motor is located at the base of the manipulator in order to further reduce the overall weight of the robot. Due to the unique characteristic of MR actuators, intrinsically safe actuation is achieved without compromising high quality actuation. Despite these advantages, modeling and control of MR actuators present some challenges. The antagonistic configuration of MR actuators may result in limit cycles in some cases when the actuator operates in the position control loop. To study the possibility of limit cycles, describing function method is employed to obtain the conditions under which limit cycles may occur in the operation of the system. Moreover, a connection between the amplitude and the frequency of the potential limit cycles and the system parameters is established to provide an insight into the design of the actuator as well as the controller. MR actuators require magnetic fields to control their output torques. The application of magnetic field however introduces hysteresis in the behaviors of MR actuators. To this effect, an adaptive model is developed to estimate the hysteretic behavior of the actuator. The effectiveness of the model is evaluated by comparing its results with those obtained using the Preisach model. These results are then extended to an adaptive control scheme in order to compensate for the effect of hysteresis. In both modeling and control, stability of proposed schemes are evaluated using Lyapunov method, and the effectiveness of the proposed methods are validated with experimental results

    Actuators for Intelligent Electric Vehicles

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    This book details the advanced actuators for IEVs and the control algorithm design. In the actuator design, the configuration four-wheel independent drive/steering electric vehicles is reviewed. An in-wheel two-speed AMT with selectable one-way clutch is designed for IEV. Considering uncertainties, the optimization design for the planetary gear train of IEV is conducted. An electric power steering system is designed for IEV. In addition, advanced control algorithms are proposed in favour of active safety improvement. A supervision mechanism is applied to the segment drift control of autonomous driving. Double super-resolution network is used to design the intelligent driving algorithm. Torque distribution control technology and four-wheel steering technology are utilized for path tracking and adaptive cruise control. To advance the control accuracy, advanced estimation algorithms are studied in this book. The tyre-road peak friction coefficient under full slip rate range is identified based on the normalized tyre model. The pressure of the electro-hydraulic brake system is estimated based on signal fusion. Besides, a multi-semantic driver behaviour recognition model of autonomous vehicles is designed using confidence fusion mechanism. Moreover, a mono-vision based lateral localization system of low-cost autonomous vehicles is proposed with deep learning curb detection. To sum up, the discussed advanced actuators, control and estimation algorithms are beneficial to the active safety improvement of IEVs
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