Systems modelling and simulation in the product development process for automotive powertrains : executive summary

This submission is a summary of the ten submissions that form the Engineering Doctorate Portfolio. The aim of the portfolio is to demonstrate the benefit of applying systems modelling and simulation in a modified powertrain product development process. A description is given of the competitive pressures that are faced by motor manufacturers in the global automotive business environment. Competitive pressures include a requirement for reduced time to market, exacting product quality standards, manufacturing over-capacity that increases fixed costs and compromises profit margins, and legislation that is increasingly difficult to meet. High-level strategic responses that are being made by manufacturers to these pressures are presented. Each strategic response requires organisational changes and improved approaches to the way in which day-to-day business is conducted. Computer Aided Engineering (CAE) is presented as an approach that can help to improve the competitiveness of motor manufacturers by reducing product development time and the level of hardware prototyping that is required. An investigation in five engineering companies yielded a number of observations about the use of CAE and its integration into product development. Best practice in the implementation of CAE in the product development process is defined. The use of CAE by a leading motor manufacturer in powertrain development is compared with the best practice model, and it is identified that there is a lack of coherence in the application of CAE. It is used to tackle specific problems but the use of CAE is not integrated into the product development process. More importantly, it was found that there is limited application of systems modelling and simulation, which is a critical technique for the effective integration of vehicle systems and the development of on-board vehicle control systems. Before systems modelling and simulation can be applied III powertrain development, an appropriate set of tools and associated modelling architecture must be determined. An appraisal of a range of different tools is undertaken, each tool being appraised against a set of criteria. A combination of DymolaIModelica and MATLAB/Simulink tools is recommended as the optimum solution. DymolaIModelica models of the vehicle plant should be embedded into Simulink models that also contain controller and driver models. MATLAB should be used as the numerical engine and for the creation of user environments. Transmission calibration is selected as a suitable pilot example for applying systems modelling and simulation in powertrain development. Best practice in CAE implementation and the systems modelling and simulation architecture are validated using this example. Simulation models of vehicles equipped with CVT and discrete ratio automatic transmissions are presented. A full description of the operation of the transmission system, of the simulation model itself, and of the validation of the model is presented in each case. The potential benefit of the CVT model in transmission calibration is demonstrated. A Transmission Calibration Simulation Tool (TCST) is described within which the discrete ratio simulation model is encapsulated. The TCST includes a user environment in which the simulation model can be parameterised, a variety of simulation runs can be specified, and simulation results are processed. Development of the TCST requires an objective measure of driveability effects that are influenced by the transmission shift schedule. A method for objective assessment of driveability is developed, correlated, and implemented as an integral part of the TCST. This element of the TCST allows trade-off exercises to be conducted between fuel economy and driveability. The development of a transmission calibration based on experimental testing is compared with a similar exercise based on simulation testing. This study shows that, if the TCST is properly integrated into the transmission calibration process, the vehicle test time taken to optimise the calibration for fuel economy could be reduced by six weeks, and a week of calibrator time could be saved. Thus, the aim of the submission is fulfilled, since the benefit of applying systems modelling and simulation in the powertrain development process has been demonstrated. It is concluded that a consistent approach is required for effectively integrating systems modelling and simulation into the product development process. A model is proposed that clarifies how this can be achieved at a local level. It is proposed that in the future, the model is applied whenever systems modelling and simulation is introduced into a powertrain department

Comprehensive Modeling and Analysis of Rotorcraft Variable Speed Propulsion System With Coupled Engine/Transmission/Rotor Dynamics

This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean-line compressor and turbine approximations is developed. Finally an analysis of high frequency gear dynamics including the effect of tooth mesh stiffness variation under variable speed operation is conducted including experimental validation. Through exploring the interactions between the various subsystems, this investigation provides important insights into the continuing development of variable-speed rotorcraft propulsion systems

Component control for the Zero Inertia powertrain

X+206hlm.;24c

Compendium in Vehicle Motion Engineering

This compendium is written for the course “MMF062 Vehicle Motion Engineering” at Chalmers University of Technology. The compendium covers more than included in that course; both in terms of subsystem designs and in terms of some teasers for more advanced studies of vehicle dynamics. Therefore, it is also useful for the more advanced courses, such as “TME102 Vehicle Modelling and Control”.The overall objective of the compendium is to educate engineers that understand and can contribute to development of good motion and energy functionality of vehicles. The compendium focuses on road vehicles, primarily passenger cars and commercial vehicles. Smaller road vehicles, such as bicycles and single-person cars, are only very briefly addressed. It can be mentioned that there exist a lot of ground-vehicle types not covered at all, such as: off-road/construction vehicles, tracked vehicles, horse wagons, hovercrafts, and railway vehicles.Functions are needed for requirement setting, design and verification. The overall order within the compendium is that models/methods/tools needed to understand each function are placed before the functions. Chapters 3-5 describes (complete vehicle) “functions”, organised after vehicle motion directions:\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 3:\ua0Longitudinal\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 4:\ua0Lateral\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 5:\ua0Vertical\ua0dynamicsChapter 1 introduces automotive industry and the overall way of working there and defines required pre-knowledge from “product-generic” engineering, e.g. modelling of dynamic systems.Chapter 2 also describes the subsystems relevant for vehicle dynamics:• Wheels and Tyre\ua0• Suspension\ua0• Propulsion\ua0• Braking System\ua0• Steering System\ua0• Environment Sensing SystemThe compendium is released in a new version each year, around October, which is the version your read now. A "latest draft" is more frequently updated and often includes some more, sometimes unfinished, material: https://chalmersuniversity.box.com/s/6igaen1ugcjzuhjziuon08axxiy817f

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

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

Compendium in Vehicle Motion Engineering

This compendium is written for the course “MMF062 Vehicle Motion Engineering” at Chalmers University of Technology. The compendium covers more than included in that course; both in terms of subsystem designs and in terms of some teasers for more advanced studies of vehicle dynamics. Therefore, it is also useful for the more advanced course “TME102 Vehicle Modelling and Control”.The overall objective of the compendium is to educate vehicle dynamists, i.e., engineers that understand and can contribute to development of good motion and energy functionality of vehicles. The compendium focuses on road vehicles, primarily passenger cars and commercial vehicles. Smaller road vehicles, such as bicycles and single-person cars, are only very briefly addressed. It should be mentioned that there exist a lot of ground-vehicle types not covered at all, such as: off-road/construction vehicles, tracked vehicles, horse wagons, hovercrafts, or railway vehicles.Functions are needed for requirement setting, design and verification. The overall order within the compendium is that models/methods/tools needed to understand each function are placed before the functions. Chapters 3-5 describes (complete vehicle) “functions”, organised after vehicle motion directions:\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 3:\ua0Longitudinal\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 4:\ua0Lateral\ua0dynamics\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 Chapter 5:\ua0Vertical\ua0dynamicsChapter 1 introduces automotive industry and the overall way of working there and defines required pre-knowledge from “product-generic” engineering, e.g. modelling of dynamic systems.Chapter 2 also describes the subsystems relevant for vehicle dynamics:• Wheels and Tyre\ua0• Suspension\ua0• Propulsion\ua0• Braking System\ua0• Steering System\ua0• Environment Sensing Syste

Simulation and Optimization of Wet Double Clutch Transmission (DCT)

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)

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

CHARACTERIZATION OF HYDRAULIC INTERACTIONS BETWEEN TORQUE CONVERTER AND TRANSMISSION DURING TRANSIENT EVENTS

A torque converter was instrumented with 29 pressure transducers to measure the torus, clutch plate, and torque converter cavities using telemetry to transfer the data. The torque converter was placed in a six-speed front wheel drive transmission and a test cell was built to drive and load the transmission to mimic in-vehicle performance. Steady state tests were completed to establish a baseline for pressure performance of the torque converter. The transient events tested include back drive and gear shifting. Back drive showed how the pressure fluctuates across the speed ratios above 1 as well as identifying the stator speed. Gear shifting presented how large the pressure change can be between each gear state. Low speed downshifting, where hydraulic demand can possibly exceed pump capacity, resulted in showing the control over the torque converter clutch was still possible and reliable. These results can be used to improve future calibrations and designs