Energy storage is a crucial condition for both transportation purposes and for the use of electricity. Flywheels can be used as actual energy storage but also as power handling device. Their high power capacity compared to other means of storing electric energy makes them very convenient for smoothing power transients. These occur frequently in vehicles but also in the electric grid. In both these areas there is a lot to gain by reducing the power transients and irregularities. The research conducted at Uppsala university and described in this thesis is focused on an all-electric propulsion system based on an electric flywheel with double stator windings. The flywheel is inserted in between the main energy storage (assumed to be a battery) and the traction motor in an electric vehicle. This system has been evaluated by simulations in a Matlab model, comparing two otherwise identical drivelines, one with and one without a flywheel. The flywheel is shown to have several advantages for an all-electric propulsion system for a vehicle. The maximum power from the battery decreases more than ten times as the flywheel absorbs and supplies all the high power fluxes occuring at acceleration and braking. The battery delivers a low and almost constant power to the flywheel. The amount of batteries needed decreases whereas the battery lifetime and efficiency increases. Another benefit the flywheel configuration brings is a higher energy efficiency and hence less need for cooling. The model has also been used to evaluate the flywheel functionality for an electric grid application. The power from renewable intermittent energy sources such as wave, wind and current power can be smoothened by the flywheel, making these energy sources more efficient and thereby competitive with a remaining high power quality in the electric grid.

This research systematically compares various electrified vehicles based upon electrification levels and powertrain configurations. A series of novel hybrid electric powertrain systems based on the newly proposed Hybridized Automated Manual Transmission (HAMT) concept are introduced. One representative hybrid powertrain system is selected to illustrate their operation principle. The new HAMT-based hybrid powertrain system overcomes the bottleneck problem of mainstream power-split hybrid systems with relatively low torque capacity and the constraint for utility vehicle electrification, and presents advantages over other hybrid powertrain systems in efficiency and costs. In addition, the new hybrid powertrain system can deliver continuous output torque by filling torque hole during gearshift, through coordinated control of engine, motor, and transmission, improving the driveability of regular Automated Manual Transmission (AMT), whose applications have been hampered by torque hole over the past years. The proposed HAMT-based hybrid systems with improved torque capacity, efficiency, costs, and driveability come with a compact design and more flexible operation through the amount of gearwheels equivalent to a 5-speed AMT to achieve 8 variable gear ratios for the Hybrid Electric Vehicle (HEV) mode and Electric Vehicle (EV) mode operations of a Plug-in Hybrid Electric Vehicle (PHEV). Model-based optimization, dynamics analysis, and powertrain control strategies have been introduced for a PHEV with a representative 8-speed HAMT. Vehicle simulations have been made to study and verify the capability and advantages of the new electrified powertrain system. Firstly, the operation principles of various HAMTs are discussed through detailed power flows at each gear. The fundamental principles of typical HAMT variations are explained using a new power-flow triangle with three ports. Based on the concept of Torque Gap Filler (TGF), a set of HAMT system designs have been introduced and closely studied to provide continuous and stable output torque. The selected hybrid powertrain system equipped with a representative HAMT system supports both HEV mode and EV mode with eight variable gear ratios for each mode. Among the eight forward gear ratios, six are independent and two are dependent on the other gears. Combinations of dog clutches at all gears are designed to eliminate torque holes. Gear ratios and gearshift schedule of the 8-speed HAMT are designed to support the new design. Torque paths at each gear are illustrated and transient scenarios including gearshifts and mode transitions are investigated. The gear ratio of each gear is determined by considering the unique clutch combination of this HAMT, using the classical gear ratio design method - Progressive Ratio Steps. Due to the broader high efficiency operation region of electric motors, a model-based optimization method is used to determine the two gear ratios for the EV mode to achieve better fuel economy and avoid unnecessary gearshifts. Dynamic Programming (DP) is used to identify the optimal gear ratios, considering vehicle fuel economy for the EPA75 and Highway Fuel Economy Fuel Test (HWFET) driving cycles. The 4th and 6th gears among the eight gear ratios in the EV mode of PHEV are based on 2-speed gearbox design for an EV, and their gearshift schedules are determined by optimization. Combining the considerations for the hybrid and EV modes of a PHEV, key elements of the proposed HAMT system, including gearshift schedule, clutch combination, and gear ratios for highly efficient operation are determined. The more challenging driveability issues during mode transition from EV to HEV and power-on gearshift with TGF during acceleration are addressed. Both of these two operations require relatively high power/torque outputs and involve multiple powertrain components, including engine, motor, main clutch and gearbox, within a period of two seconds. A lumped-mass model (LMM) of the HAMT-based hybrid vehicle is built to analyze the driveline dynamics in two steady states and four transient states. Each of these states is analyzed independently, according to states of main clutch and gear selectors, considering different phases of the TGF operation and EV-HEV mode transition. The methods for modeling the discontinuity of clutch torque and dog clutch inside the HAMT are discussed to support the subsequent powertrain system modeling and control development. To identify the optimal control schemes for model transition and gearshift, the model-based optimization method for a post-transmission parallel PHEV is developed. The vehicle powertrain model was initially built using AUTONOMIE and MATLAB/Simulink with primary parameters from a prototype PHEV and its dSPACE ASM model developed at University of Victoria. System dynamics in EV mode and hybrid mode are described as a group of state-space equations, which are further discretized into matrix form to simplify the optimization search. A DP-based global optimization method is used to identify the optimal control inputs, including engine torque, motor torque, and main clutch torque. Four principles for desirable EV-HEV mode transitions are extracted based on the results of the optimization. To model different operation modes and complex power flows, the initial baseline powertrain system model is then replaced by a customized MATLAB/SimDriveline model. In this new physics-based powertrain model, gearshift actuators and controller are added to model the gearshift and mode transition processes. To achieve good driveability, the TGF feature of the HAMT design is split into five transient and two steady phases, each corresponding to a fundamental operating mode. Control logics of upshift and downshift, as well as EV-HEV mode transition are introduced. Four principles of mode transition derived from global optimization results are introduced for powertrain system control. Simulations of the HAMT-based hybrid powertrain operations have been carried out to verify the functionality and advantages of the proposed HAMT design in achieving excellent driveability during mode transition and gearshifts. Through controlled coordination of engine, motor and main clutch, EV-HEV mode transition can be achieved smoothly within a period of 2-3 seconds. Even slight driveline fluctuation can be eliminated by dedicated anti-shuffle control with the motors as actuators. The same simulation model also demonstrates excellent driveability during power-on gearshift. Comparing simulation results with and without TGF shows that this new hybrid powertrain system can effectively eliminate torque holes during gearshift. With the demonstrated advantages of this new system in efficiency, torque capacity, simplicity in design and manufacturing costs over its existing rivals, the research provides a promising alternative to mainstream power-split hybrid electric powertrain system design. / Graduate

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This research investigates the effects of both a Hybrid Energy Storage System and an Electrified Turbocharger in a consumer performance vehicle. This research also attempts to support the development of a prototype vehicle containing a Hybrid Energy Storage System currently being developed at McMaster University. Using a custom simulation tool developed in Matlab Simulink, Simulink models of each of the technologies were developed to predict the behavior of these subsystems across multiple physical domains. Control modeling, optimization and testing was completed for both systems. In addition, controls modeling for the Hybrid Energy Storage System was integrated with the development effort for a prototype vehicle considering the specifics of real world components. To assess the impact of these technologies on a performance vehicle platform, the simulation tool tested each technology using multiple vehicle variations. Three vehicle variants were developed, representing: a conventional performance hybrid design, a hybrid vehicle containing an electrified turbocharger, and a vehicle containing a Hybrid Energy Storage System. Electrical system peak output power was the vehicle specification held constant between each vehicle variant. Each vehicle variant was simulated against a number of traditional drive cycles representing everyday driving scenarios in an attempt to compare fuel economy while identifying each technologies individual impact on the vehicles performance. Finally, each vehicle variant was simulated using a custom performance drive cycle in a virtual race. Both technologies as assessed and in comparison to a larger battery variant, did not result in improved fuel economies during conventional vehicle driving. Both the Hybrid Energy Storage System and electrified turbocharger demonstrated improved vehicle performance in particular scenarios. / Thesis / Master of Applied Science (MASc) / Electrified vehicles have not typically been viewed as performance vehicles. A recent trend has seen a growing number of manufacturers turn to hybrid and electric powertrains to produce high performing vehicles. However, a performance vehicle's electrical power is conventionally limited by the size and power of its battery, adding weight and cost. Two technologies offer the ability to increase the power of these electrified components without the need for a large battery. First, Hybrid Energy Storage System combines ultra-capacitors and batteries to increase the power density of the system. Second, an Electrified Turbocharger improves the turbo lag of a turbocharged engine and also recovers waste heat energy from the exhaust gases which is then used to propel the vehicle. This research identifies and demonstrates the potential impact these two technologies have when included in an American Muscle Car.

As requirements related to vehicle fuel economy and emissions continue to increase, automakers are developing complex hybrid powertrain control systems to meet these requirements. With the increase in powertrain complexity and performance requirements of a hybrid vehicle, embedded control systems have become an integral part of these vehicles. A hybrid’s ability to recapture energy normally lost as heat during braking situations can account for an increase in efficiency of up to 28%. This study explores the use of a grade adaptive regeneration strategy for improving a hybrid vehicle’s energy recapture capability. The concept of the grade adaptive regeneration strategy was developed using a computer aided simulation model and then implemented on the Mississippi State University Challenge X hybrid vehicle. The real-time performance of the system was evaluated through chassis dynamometer and on-road tests. Substantial improvements over the native hybrid control strategy, including fuel-economy and energy recapture, have been achieved.

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This thesis outlines the design and implementation process of an electrified powertrain for use in an American muscle car. Designed as McMaster University's entrant to the EcoCAR 3 Advanced Vehicle Technology Competition (AVTC), an electrified powertrain was developed to provide a Chevrolet Camaro with the performance expected by the American muscle car market while maintaining ever increasing fuel economy regulations. A background of current trends in vehicle electrification, including the prominent market segments experiencing these trends, will be explored along with the history of the classic and modern American muscle car's technical specifications. Following an investigation into existing vehicle electrification trends, the selected hybrid architecture will be discussed. The process of converting a conventional combustion powertrain into a series-parallel hybrid electric powertrain will be explored from the component-level through to full system design. Following a review of the design process for the powertrain, a high-level testing plan will be proposed using a number of test cells available within the facility. This plan will begin at the component-level exploring specific areas of potential complication and move up to complete system-level testing of powertrain functionality. / Thesis / Master of Applied Science (MASc) / Until recently, hybrid electric vehicles have tended to be available in a fairly limited market segment with few offerings for performance-oriented vehicle customers. The introduction of high performance hybrid vehicles suggests that this trend is likely to change. Increasingly more stringent fuel economy and emissions standards means that performance vehicle segments such as American muscle cars must adopt new technologies to retain their performance characteristics. Hybrid powertrains are one solution to providing and improving on the iconic performance of American muscle while meeting future regulatory changes. The addition of a number of electrified components to a gasoline powertrain can assist in achieving desired performance while reducing fuel economy. This thesis investigates the detailed design process adopted to make these modifications while maintaining the functionality expected by muscle car owners. After the design and assembly of the hybrid muscle car powertrain, a specific testing plan was laid out to ensure that the system is capable of sustaining the expected power output. This design and testing process can help introduce new hybrid vehicles to the market which are capable of meeting both the upcoming fuel economy regulations as well as the ongoing performance expectations of the muscle car market.

An energy management strategy for a prototype P4 parallel hybrid Chevrolet Blazer is developed for the EcoCAR Mobility Challenge. The objective of the energy management strategy is to reduce energy consumption while maintaining the drive quality targets of a conventional vehicle. A comprehensive model of the hybrid powertrain and vehicle physics is constructed to aid in the development of the control strategy. To improve fuel efficiency, a Willans line model is developed for the conventional powertrain and used to develop a rule-based torque split strategy. The strategy maximizes high efficiency engine operation while reducing round trip losses. Calibratable parameters for the torque split operating regions allow for battery state of charge management. Torque request and filtering algorithms are also developed to ensure the hybrid powertrain can smoothly and reliably meet driver demand. Vehicle testing validates that the hybrid powertrain meets acceleration response targets while delivering an enjoyable driving experience. Simulation testing shows that the energy management strategy improved fuel economy in most drive cycles with improvements of 8.8% for US06, 9.8% for HWFET, and 0.1% for the EcoCAR Mobility Challenge Cycle. Battery state of charge management behavior is robust across a variety of drive cycles using inputs from both simulated and test drivers. The resulting energy management strategy delivers an efficient, responsive, and reliable hybrid electric vehicle. / Master of Science / A control strategy for a hybrid vehicle is developed to improve fuel efficiency without sacrificing vehicle responsiveness. Efficiency improvements are achieved by the strategy intelligently selecting to use the engine, motor, or a combination of the two to minimize fuel consumption. The strategy also handles the important tasks of maintaining the battery pack charge and smoothly transitioning between the engine and motor power. All together, this results in a hybrid vehicle with both improved fuel economy and an enjoyable driving experience.

Increasing pressure from environmental, political and economic sources are driving the development of an electric vehicle powertrain. The advent of hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs) bring significant technological and design challenges. The success of electric vehicle powertrains depends heavily on the robustness and longevity of the on-board energy storage system or battery. Currently, lithium-ion batteries are the most suitable technology for use in electrified vehicles. The majority of literature and commercially available battery performance data assumes a working environment that is at room temperature. However, an electrified vehicle battery will need to perform under a wide range of temperatures, including the extreme cold and hot environments. Battery performance changes significantly with temperature, so the effects of extreme temperature operation must be understood and accounted for in electrified vehicle design. In order to meet the aggressive development schedules of the automotive industry, electrified powertrain models are often employed. The development of a temperature-dependent battery model with an accompanying vehicle model would greatly enable model based design and rapid prototyping efforts. This paper empirically determines the performance characteristics of an A123 lithium iron-phosphate battery, re-parameterizes the battery model of a vehicle powertrain model, and estimates the electric range of the modeled vehicle at various temperatures. The battery and vehicle models will allow future development of cold-weather operational strategies. As expected the vehicle range is found to be far lower with a cold battery back. This effect is seen to be much more pronounced in the aggressive US06 drive cycle where the all-electric range was found to be 44% lower at -20°C than at 25°C. Also it was found that there was minimal impact of temperature on range above 25°C

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