Anti Jerk Control Of Hybrid Electric Vehicle Engineering Essay

Anti Jerk harbour Of Hybrid Electric Vehicle Engineering hearThe report details the polish up do in the argona of anti-jerk check come forth of fomites. It explains the phenomenon of snubline rounds excited out-of-pocket to torsion of wedgeline at high locomotive engine tortuositys causing undesirable longitudinal oscillations in vehicle body.Report starts with a broad introduction to the discipline and lays down the aims and objectives of the research compute.The aims and objectives of the project argon to rule an lively feedback command for an galvanic caralal drive of a hybrid electric vehicle to damp these undesirable oscillations.A summary critical review of previous research twist do in this area is certifyed which defines the starting point of the project. assorted techniques utilize for anti-jerk checker in formal vehicle are discussed. Basic approach to ideal run aground control design is presented in the report. An introduction to hybrid electric vehicle driveline and description of its components different from conventional vehicle is shown.The report in any case lays down the mathematical function of the work to be followed for the research project with a project plan.INTRODUCTIONThe increasing pressure of protecting the natural environment and to decrease the dependence on non-renewable sources of energy has encouraged vehicle manufacturers to develop more clean and competent power systems. As a result Hybrid vehicles are hot topic for research among vehicle manufacturers. Efforts are being do to make the vehicles more fuel efficient with high performance and minimum CO2 emissions. Diesel hybrids are considered as next big thing among ecological designs since diesel engines are 20 % 30% more fuel efficient than their gas pedal counter split.Nowadays noise, thrill and harshness (NVH) issues seduce become more important for a customer such that there are precise stringent requirements for noise or shakin g in a vehicle. Driveability of a vehicle is majorly impacted by NVH problems and is strongly felt as vehicles performance during various manoeuvres such as acceleration, braking, gear flip-flop etc. Thus vehicle manufacturers and OEMs have realized the importance of NVH issues and target to identify the root cause of shaking and compound the correcting measures at early stages of manufacturing with a main goal to refine the ride and driveability of a vehicle.These days efforts are being made to increase the performance of vehicles and to make them more fuel efficient by using different techniques and one of the techniques is electrification of various systems in a vehicle. Electronic power assist steering system, electric prompt roll control, electronic differential, brake by wire are some of the examples of electrification of vehicle systems. This kind of methodology becomes more evident in case of hybrid electric vehicles where electric power components including power elect ronics are integral part of the powertrain. It has been observed that using these electrification techniques not further helps in increasing the performance of the vehicle but alike makes them more fuel efficient. Thus the electrification in a diesel hybrid powertrain to improve the driveability of vehicle forms the main platform for this research project.Problem Statement unity of the major NVH issues in automobiles is torsional vibrations of driveline. The torsion of drivetrain at high engine torques causes oscillations in driveline. These oscillations are generally excited by various sources such as press forwardy or sudden load/torque change, gear change and unevenness of road surface. These oscillations cause longitudinal acceleration in vehicle structure and passenger compartment of the vehicle, which reduces the comfort and driveability of the vehicle and are experienced as unwanted jerk by the driver and passengers. These font of driveline oscillations are termed as Je rking, which is the main focus of this research.The high engine torques at low engine speeds makes this phenomenon more common in modern diesel engines. A sudden/abrupt pressing or purgative of accelerator pedal by the driver causing a rapid increase or decrease in engine torque called as tip-in and tip-out respectively, which gives scratch to oscillations between frequency frame of 2 10 HZ. To reduce these oscillations and to increase the comfort and improve the driveability of vehicle some kind of anti-jerk control is required. In conventional diesel engine vehicles, active control of engine fuelling and drivers torque demands and passive utilization of mechanical isolators such as dual concourse fly pedal (DMF) are utilize to permit feed forward active and passive damping of these oscillations.Aims and ObjectivesThe aims of the research project are to investigate the phenomenon of anserine in a diesel hybrid electric vehicle and to electrify the anti-jerk control using the electric motor of hybrid vehicle to damp these oscillations. The aims of the project would be realized through following objectivesA feed forward approach in poseing the vehicle driveline to investigate driveline goosey using SIMULATION-X. The response of vehicle during tip-in, tip-out, idle and coast conditions would be studied.To design an active feedback control for electric motor of the hybrid vehicle to permit active damping of the investigated driveline oscillations.To analyse its opinions on fuel consumption, comfort and sportiness of the vehicle and semblance with conventional anti-jerk control methods.To study the impact of passive damping of these oscillations using DMF in the driveline.Due to the diverse nature of the project the work has been divided between cardinal students. It was decided that deterrent exampleling of the driveline result be done by Pavan Mukkamala and Kamal Shamnani forget take care of control design part of the project.Report OverviewAs it great deal be seen before, the report begins with the introduction to the current scenario of hybrid vehicles, driveability and electrification of vehicle systems. Then problem statement was defined followed by aims and objectives.The next chapter would summarize the undertaken review to understand the research work beginning with analyses of jerking. The literature review also serves as the basis to provide the expected response characteristics. It also explains the different control methods use on a conventional diesel engine vehicle.Chapter 3 lays down the outline of the procedure to be followed for the research project along with project plan. Conclusions establish the literature review have been made in chapter 4.LITERATURE REVIEWDriveline OscillationsDifferent type of powertrain configurations (front hustle drive or rear roll up drive), engine type and energising response, engine torque at different engine speeds and vehicle mass excites different kind of oscillations in v ehicle driveline. These oscillations have been summarized below 1Torsion of shaft causes jerking and pitching type oscillations in the driveline. Jerking then causes longitudinal acceleration of car body in a frequency range of 2 5 Hz. The pitch motion frequency is about 1 2.5 Hz.Engine movement and engine mount characteristic excites oscillations in a frequency range of 15 200 Hz. Gear box housing cause oscillations in the frequency range between 50 and 80 Hz.Combustion process, movement of pistons inside the cylinder and engine speed causes oscillations depending upon type of engine, number of cylinders and engine speed. Inline-four cylinder engine types engine exhibit rangy cyclical fluctuations of torque at idle speed.Driveline Jerking in a Diesel Engine VehicleThe fast response and high torque of modern at once injection diesel engines results in sharp and large changes in driveline torque. Moreover smaller and more powerful modern diesel engines with reduced flywheel ina ctivenesss and reduced mass of powertrain components reduce the initial response to transient throttle demands by the driver. But on the other hand double-quick response and large changes in driveline torque make them more susceptible towards generation of driveline oscillations. These types of oscillations are commonly referred as driveline jerking, surging, driveline shuffle, driveline judder, jerk oscillations or bonanza effect. 2, 3 and 4.These oscillations are generally excited due to the torsional vibrations of driveline when accompanied with sudden torque change. The sudden driveline torque change rear end be described as tip-in and tip-out manoeuvres. The tip-in and tip-out behaviour are described in figure-1 as a step input and after some seconds a step back to zero 2. The tip-in and tip-out behaviour causes oscillations to engine speed. The difference between engine speed and wheel speed is generally utilise to describe the torsional oscillations of driveline shown as torsional speed in figure-2-1. These oscillations are transmitted to the vehicle body from wheel and tire and cause oscillations in vehicle longitudinal acceleration. The oscillations in longitudinal acceleration of vehicle body are shown in figure-2-2. The acceleration of vehicle body oscillates between the frequency range of 2 and 5 Hz. The observed frequency of oscillation is dominated by drivelines first natural frequency. This frequency lies between the resonance frequencies of various sensitive world body parts such as shoulders (4 6 Hz), stomach (4- 8 Hz) and trunk (3 6 Hz) 5. So, these different body parts may resonate due to this jerking and hence very unpleasant for drivers and passengers. work 2 Effect of Tip-in and Tip-out on Engine and wheel speed 2Figure 2 Body acceleration during Tip-in and Tip-out 2.The phenomenon of jerking is more common where the manual clutch is not present, as a human driver uses manual clutch to reduce these vibrations. Whereas in robotli ke clutch units the design philosophy is to reduce the clutch engagement and disengagement snip to prevail smooth torque transfer which gives rise to driveline oscillations.These oscillations differ at different gear ratios. It has been shown that oscillation frequency increases shifting from first gear to higher gears due to change in damping co-efficient associated with each gear and reflected engine inertia 6. Generally driveline shuffle is also associated with phenomenon of clonk or gear rattle. Clonk is basically a noise which is a by-product of backlash present in gears. Backlash is allowed to integrate operating clearances and manufacturing tolerances. The clonk rouse be reduced by increasing the driveline compliance but side effect of increasing compliance is the increased driveline oscillations hence jerking.Anti-Jerk figure of Conventional VehiclesThe main parameters which govern the severity of jerking response of vehicle jackpot be termed as engine torque rise rate and driveline compliance. Anti-jerk control acts as the balance between comfort and sportiness of the vehicle. The reduction in driveline oscillations is possible by controlling the engine torque rise rate, which after part be done by smoothening of drivers torque demands. In a conventional diesel engine vehicle it is done by electronic fuelling control and in a petrol engine vehicle it is done by using spark advance and electronic throttle control. Various manufacturers use the filtering of drivers torque request but this becomes of no use when oscillations are excited by ground roughness.In practice, anti-jerk restraint parameters are experimentally optimized to combine comfort and sportiness of the vehicle 2. The parameters are tuned and accessed, to include non-linearities present in the system, by using various test-runs to find optimal control parameters. All these parameters are stored in form of different maps and relationship between different engine parameters which are then used to obtain a feed-forward controller for the vehicle.The reductions in driveline oscillations in conventional drivetrain are possible by various active and passive methods. These includeOptimizing driveline parameters such as compliance of clutch, driveshaft and transmission, gear ratios and inertia of driveline components.Passive reduction of oscillations by adding damping to the system.Active control of engine torque.Model ground Anti-Jerk ControlIn past these parameters were obtained by using trial and error methods which may not be fully optimized and this strategy takes a lot of age depending upon the knowledge of automotive engineer 2. These days as explained above that optimal anti-jerk control parameters are obtained experimentally by systematic and standardized computer back up test runs. This procedure still relies on time-consuming test runs. Whereas use of simulation can help in analytical assessment of a large number of performance, driveability and comfort parameters with reduced costs and less risk of testing. air can determine highly optimized and true system parameters out of which only few parameters are required to be checked by real tests which save a lot of testing time. Due to this a lot of emphasis is assumption on use of simulation to obtain the optimal controller parameters and also if possible integration of model based controller in the vehicle is also being considered. A review of model based controller design approach is shown below.Modelling techniquesDriveline of a conventional diesel engine vehicle is made up of an internal combustion engine which is connected to a gearbox through clutch whose rig is connected to driveshafts which transmits torque to the wheels. In model based controller design gray-box approach is used to model the drivetrain. According to which driveline can be modelled as lumped parameter model which is made up of rotating bodies with lumped inertias, compliances, damping losses, input torque and load torque through environmental forces 6. Even a complete linear state space model based upon this comparatively simple chemise of driveline is of 14th order which is very complex and requires very extensive computational resources to run on a real time engine ECU and is therefore very expensive and cannot be implemented for mass production 4. Structure of a complex rear wheel drivetrain is shown in figure -3 4.Figure 2 A rear wheel drive vehicle driveline structure 4Thus it is required to define a reliable and low order linear representation of boilers suit driveline kinetics. Since the purpose of anti-jerk controller is to damp the oscillations at drivelines first resonance mode, some approximations can be made to reduce the model complexity. To simplify the model it can be assumed that driveline oscillations at first resonance mode are caused due to torsion of drive shafts which can be explained as they are subjected to relatively highest torque since the torque from en gine is amplified by the transmission and terminal drive 1, 7. Clutch due to its higher stiffness can be considered as not contributing to first resonance mode. All these assumptions can be justified by measurements 1, 7. This reduces the driveline model to a 2nd, 5th or 7th order depending upon the type of drive configuration and flywheel.For a reliable and accurate design of a model-based controller identification of model parameters is done on basis of measurement data. To incorporate the non-linearities present in driveline the set of parameters depending upon engine speed can be stored in form of look-up tables resulting in time-variant model which is more accurate and reliable 1, 7. Different techniques such as least square optimization and extended kalman-filter can be used to optimize the non-linearities present in the system to reduce the error. The model can be validated by comparing the simulation results with real behaviour of the car.Controller DesignIn a model based anti-jerk controller design the controller is used in a feedback path. Here also different methodologies have been used to design the control strategy. One of them is to use the model to obtain the controller parameters. Thus in this case model based controller design approach is used to assist the engineer and to save time on testing 2. This type of control topology is shown in figure 2-4 2.Figure 2 Model based designed controller structure 2In this type of control architecture a two step procedure is used to damp the driveline oscillations first the requested driveline torque Tin is filtered to prevent jerking generation and then the feed-back controller minimizes the jerking further. State of the vehicle can be the feedback to the controller which can be engine speed, wheel speed, and vehicle speed etc, based on which variable controller parameters will be chosen from predefined maps. Advantage of this type of control structure is that it can be used to plant for the disturbanc es from the ground roughness. The other advantage of this type of control strategy is that it requires only controller variable parameters to be stored in the ECU of the engine which will be extracted by two performance criteria i.e. sportiness of vehicle demanded by the driver and level of comfort required through no longitudinal oscillations 2. The disadvantage of this type of controller is that it take to store different parameter values for different gears and operating points which require the experience and knowledge of automotive engineer to adjust parameter maps. Also it may require some feedback of vehicle states from the vehicle which may be difficult to measure in a vehicle. Also the adjusted parameters values for comfort and sportiness will depend upon the subjective preferences of the engineer. A field of research in this case is the invention of tuneable factor between sportiness and comfort which enables customers to tune their car to their requirement 2.another(pren ominal) approach in model based controller design is the predictive approach i.e. a reduced model of vehicle drivetrain will be include in vehicle ECU which will reproduce the occurrence of jerking before its actual occurrence and output of which is used as controller input which will then avoid jerking before its occurrence 1 , 7 and 4.Figure 2 Model based predictive control structure 1The dead time or the time delay due to engine combustion events is separated from dynamics of process and modelled separately at the end of model which makes the response of the model faster than actual vehicle 1, 7 hence enables the accurate reproduction of oscillations before their occurrence. Structure of a predictive model based controller is shown in figure 2-5 1. These types of controllers are generally equipped with an observer which incorporates the external disturbances such as ground surface roughness and compensates the model inaccuracies by including a feedback between model output and ac tual process output 1 and 7. The response of observer is faster than that of the process to make the steady state error zero after a short period of time due to this its design is done separately and values for different engine speeds and demanded torques are stored in form of look up tables. beginning locus method is used for designing these kind of controllers. An advantage of using this type of controller is that less dependence on automotive engineer to adjust parameter maps. However an appropriate compromise between comfort and sportiness needs to be defined. One of the ways to increase sportiness is to deliberately delay the activation of controller until initial vehicle acceleration. This type of method can give the user an option of different modes for example, sporty, everyday and comfort by changing the controller values 4. It can also predict system states which are difficult to measure on a real vehicle hence a more accurate system response can be obtained. At the same time this type of controller can be very expensive as it requires probatory computational resources added on to vehicle driveline ECU.Hybrid Vehicle DrivelineA hybrid vehicle is a vehicle in which powertrain has more than one source of power, a hybrid electric vehicle (HEV) has an internal combustion engine and an electric machine/motor. HEVs powertrain can be classified as serial publication or latitude hybrid systems. A series hybrid system is one in which electric motor provides all the torque required for vehicle propulsion whereas a parallel hybrid system allows torque input from either internal combustion engine or electric motor or from both. Hybrid electric vehicles are the most important topic of research for the past few years.A series hybrid vehicle driveline does not have a bet mechanical link between the engine and driveline. It is connected to a generator which in turn provides electric supply to power electronics. The electric machine/motor is connected generally through a single speed gearbox, final drive and drive shafts to wheels. Thus driveline oscillations in a series hybrid vehicle will be present, similar to a conventional vehicle. The main difference will be because of propulsion mechanism which is an electric motor. Regarding the anti-jerk control for a series hybrid vehicle, it can be done by active control of electric motor torque. It has been explained in a publication by Borodani and Ambrosio 3 in which an active robust control algorithm based on the H control technique was designed for a Fiat Bravo 1600 cc for electric only mode.In a parallel hybrid vehicle driveline both engine and motor are mechanically connected to the wheels through clutch, an automatic gearbox and drive shafts. The vibration modes of parallel hybrid driveline are similar to a conventional vehicle. A similar strategy can be used to minimize the jerking as used for conventional vehicles in engine only mode. Whereas an active control of electric motor torque can also be used to prevent jerking. As there is not enough evidence of work done regarding the investigation of jerking and development of anti-jerk control for hybrid vehicles, this will be a topic of this research.Figure 2 Block diagram of hybrid drivetrain to be usedElectric motor in a hybrid vehicle driveline gives an opportunity to electrify the anti-jerk control which then can be compared with conventional methods of anti-jerk control for fuel consumption, degree of comfort and sportiness of the vehicle. A parallel four wheel driven diesel hybrid electric driveline with dual mass flywheel (DMF) of a sport utility vehicle will be used to investigate the driveline oscillation and then to design an active feedback control for electric motor to damp these oscillations. Vehicle drive configuration can be changed to front wheel drive by unlocking the central coupler. The effect electric real axle drive (ERAD) will not be considered for anti-jerk control design. The driveline is sho wn in figure 2-6. Some important components of driveline and their effect are explained belowIntegrated Starter Generator (ISG)As name suggests ISG replaces both conventional starter and alternator/generator to a single electronically controlled device. An ISG can convert electric energy to mechanical energy to start an engine and also mechanical energy to electrical energy to power all electrical systems in a vehicle such as lights, air conditioning etc and to charge battery. An ISG serves three important functions start-stop, electricity generation and power assistance 8. It allows engine start-stop functionality to save fuel instead of idling when vehicle is not in motion. ISG generates electricity from spinning crankshaft of vehicle to charge the battery. In a hybrid vehicle an ISG can provide power assist to the engine during the boost-mode. Although it cannot propel a vehicle on its own but it can assist the engine and can be used to store energy while regenerative braking. T he ISG is generally used in mild hybrids. An ISG can provide retarding force on crankshaft to generate electricity during braking this feature of ISG can be used for anti-jerk control. duple Mass FlywheelA dual mass flywheel DMF consists of two rotating flywheels primary and secondary connected by long travel arc-springs 7. Figure -7 shows the structure of a basic DMF 4. A DMF can be used to mechanically isolate the driveline oscillations arising from high speed engine oscillations by decoupling the transmission from engine. It filters out the engine irregularities completely. Due to the smooth operation of secondary flywheel and transmission input shaft gear rattle is significantly reduced. DMF can provide good vibration isolation at low engine speeds which in turn reduces the fuel consumption of a vehicle. Due to its excellent vibration isolation and damping attributes, DMF today is found in many vehicle drivelines including low budget cars 4. But despite of its advantaged DMF inc reases the system complexity. DMF is basically a spring damper unit having highly non-linear characteristics. It can temporarily store energy due to which it applies a reaction torque on internal combustion engine and alters the engine speed signal which is used by ECU. It increases the probability of undesirable side effects such as jerking.Figure 2 Dual Mass flywheel structure 4PROCEDUREProcedure of workDriveline vibration is mainly a problem of engine torque profile and compliances of components in the driveline. To study the effect of jerking in hybrid vehicles a model of driveline with all system complexities will be developed using a SIMULATION-X. The simulation-X model will be a complex model replicating the complete dynamic behaviour of the vehicle. As the frequency range of interest is 2-5 Hz, drivelines first natural frequency the model will be reduced according to a final model to be implemented for the design on controller which can accurately predict the oscillations in the desired frequency range.An active feed-back control for electric motor torque and for engine fuelling control will be designed by implementing the reduced model in MATLAB/SIMULINK. Then both controllers will be implemented in the actual complex model in SIMULATION-X to observe the system performance in terms of fuel consumption, level of comfort and sportiness.Simulation toolSimulation-XSimulation-X has been chosen to investigate the phenomenon of jerking for the project due to its very user friendly graphical user interface. This interface provides a very original and efficient lumped parameter modelling approach for modelling dynamic systems. It can model various physical systems (i.e. Electronics, Mechanics, Hydraulics, Pneumatics, Thermal etc) with much ease. It also allows for the signal and equating based modelling ideal for control systems. Another important feature of Simulation-X is the ease of parameterization i.e. it is very easy to define the system complexities an d parameters depending upon the requirement. It has numerous possibilities for visualization, analysis and transcription a large number of results associated with each element of a model. It is very beneficial for modal analysis as it can easily extract the dynamics of system by showing the modes of vibrations and the cause of these resonance modes. This feature is very handy and useful for this research project as it can be used to differentiate between the causes of oscillations in the driveline and thereby helping to reduce the model for the desired frequency range.Project PlanCONCLUSIONSOn the basis of literature review it can be stated that the high change in engine or load torque excites oscillations in vehicle driveline, known as jerking causing horizontal acceleration in vehicle body. The frequency of jerking lies in resonance frequency range of various sensitive body parts as a result it is entirely undesirable by the drivers. Comfort and driveability issues raise the need for anti-jerk control.There has not been enough work done on anti-jerk control for hybrid electric vehicles since not many hybrid electric vehicles are available in market. Other than the conventional methods, electrification of anti-jerk control can be done in a hybrid electric vehicle which will be the main aim of the research project.A model based controller design approach can be regarded as efficient and reliable. It can assist an automotive engineer in deciding control parameters for the controller, also it can be implemented directly to vehicle for anti-jerk control by reducing the order of driveline model.Driveline oscillations can also be damped using passive damping methods such as using DMF which will be studied as a part of research project.REFERENCES1 Kiencke, U. and Nielsen, L. (2005), Automotive Control Systems for Engine, Driveline and Vehicle, Springer, Berlin, Germany.2 Grotjahn, M., Quernheim, L. and Zemke, S. (2006), Modeling Identification of car driveline dy namics for anti jerk controller design, ICM 2006 IEEE 3rd International Conference on Mechatronics , 1-4244-9713-4/06.3 Borodani, P. and Ambrosio, C. (2002), Robust control of active damping of a hybrid vehicle driveline shuffle, MED2002 Conference.4 Walter, A. Kiencke, U., Jones, S. and Winkler, T. (2008), Anti-Jerk Idle Speed Control with Integrated Sub-Harmonic Vibration Compensation for vehicles with Dual Mass Flywheels, SAE International Powertrains, Fuels and Lubricants Congress Shanghai, China, 2008-01-1737.5 McDevitt, I. (2005), Torsional Vibrations of Vehicle Driveline, atomic number 62 Thesis, Automotive Product Engineering, Cranfield University.6 Lee, H.C. (2006), Driveline vibration control of electric vehicle, MSc Thesis, Automotive Product Engineering, Cranfield University.7 Baumann, J., Torkzadeh, D., Ramstein, A., Kiencke, U. and Schlegl, T. (2005), Model-based Predictive Anti-Jerk Control, Control Engineering Practice 14 (2006) 259-266.8 Viorel, I., Szabo, L., Lowenstein, L. and Stet, C (2004), Integrated Starter-Generators for Automotive Applications, Acta Electrotehnica, Volume 45 Number 3 2004.9 Reik, W., Seebacher, R. and Kooy, A. (1998), Dual Mass Fly-wheel.