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Technical Paper

Extended Range Electric Vehicle Powertrain Simulation, and Comparison with Consideration of Fuel Cell and Metal-Air Battery

The automobile industry has been undergoing a transition from fossil fuels to a low emission platform due to stricter environmental policies and energy security considerations. Electric vehicles, powered by lithium-ion batteries, have started to attain a noticeable market share recently due to their stable performance and maturity as a technology. However, electric vehicles continue to suffer from two disadvantages that have limited widespread adoption: charging time and energy density. To mitigate these challenges, vehicle Original Equipment Manufacturers (OEMs) have developed different vehicle architectures to extend the vehicle range. This work seeks to compare various powertrains, including: combined power battery electric vehicles (BEV) (zinc-air and lithium-ion battery), zero emission fuel cell vehicles (FCV)), conventional gasoline powered vehicles (baseline internal combustion vehicle), and ICE engine extended range hybrid electric vehicle.
Technical Paper

Design Optimization of the Transmission System for Electric Vehicles Considering the Dynamic Efficiency of the Regenerative Brake

In this paper, gear ratios of a two-speed transmission system are optimized for an electric passenger car. Quasi static system models, including the vehicle model, the motor, the battery, the transmission system, and drive cycles are established in MATLAB/Simulink at first. Specifically, since the regenerative braking capability of the motor is affected by the SoC of battery and motors torque limitation in real time, the dynamical variation of the regenerative brake efficiency is considered in this study. To obtain the optimal gear ratios, iterations are carried out through Nelder-Mead algorithm under constraints in MATLAB/Simulink. During the optimization process, the motor efficiency is observed along with the drive cycle, and the gear shift strategy is determined based on the vehicle velocity and acceleration demand. Simulation results show that the electric motor works in a relative high efficiency range during the whole drive cycle.
Technical Paper

Recognizing Driver Braking Intention with Vehicle Data Using Unsupervised Learning Methods

Recently, the development of braking assistance system has largely benefit the safety of both driver and pedestrians. A robust prediction and detection of driver braking intention will enable driving assistance system response to traffic situation correctly and improve the driving experience of intelligent vehicles. In this paper, two types unsupervised clustering methods are used to build a driver braking intention predictor. Unsupervised machine learning algorithms has been widely used in clustering and pattern mining in previous researches. The proposed unsupervised learning algorithms can accurately recognize the braking maneuver based on vehicle data captured with CAN bus. The braking maneuver along with other driving maneuvers such as normal driving will be clustered and the results from different algorithms which are K-means and Gaussian mixture model (GMM) will be compared.
Technical Paper

Fuel Cell Hybrid Powertrain Design Approach for a 2005 Chevrolet Equinox

A fuel cell-battery hybrid powertrain SUV vehicle is designed using an optimized model-based design process. Powertrain and fuel storage components selected include a 65 kW Polymer Electrolyte Membrane Fuel Cell (PEMFC) power module, two 67 kW electric traction motors, a 35 MPa compressed hydrogen storage tank, a 70 kW nickel metal hydride battery pack, and a University of Waterloo in-house DC/DC converter design. Hardware control uses two controllers, a main supervisory controller and a subsystem controller in addition to any embedded component control modules. Two key innovations of this work include the hybrid control strategy and the DC/DC converter. The final powertrain characteristics are expected to meet a set of Vehicle Technical Specifications (VTS).
Technical Paper

The Application of Model-Based Design Techniques in Academic Design Projects

The objective of this paper is to help students optimize project component selection or design by detailing, through two specific examples, the University of Waterloo's Alternative Fuels Team's (UWAFT's) successful design process. UWAFT successfully designed a fuel cell powered vehicle for the ChallengeX student engineering competition. The use of a formal, structured design process enabled this team to achieve great confidence in both the feasibility of their design and their ability to manifest the design. This design process is model-based whereby a parameterized software model is created. This paper hopefully assists students to overcome a common reluctance to implementing a model-based design process. After a component is constructed and tested, students can update their software model, which can help them assess the strength of their design.
Technical Paper

Development of a High-Fidelity Series-Hybrid Electric Vehicle Model using a Mathematics-Based Approach

The recent increase in oil prices and environmental concerns have attracted various research efforts on hybrid electric vehicles (HEVs) which provide promising alternatives to conventional engine-powered vehicles with better fuel economy and fewer emissions. To speed up the design and prototyping processes of new HEVs, a method that automatically generates mathematics equations governing the vehicle system response in an optimized symbolic form is desirable. To achieve this goal, we employed MapleSimTM, a new physical modeling tool developed by Maplesoft Inc., to develop the multi-domain model of a series-HEV, utilizing the symbolic computing algorithms of Maple software package to generate an optimized set of governing equations. The HEV model consists of a mean-value internal combustion engine (ICE), a chemistry-based Ni-MH battery pack, and a multibody vehicle model. Simulations are then used to demonstrate the performance of the developed HEV system.
Journal Article

Integrated Stability Control System for Electric Vehicles with In-wheel Motors using Soft Computing Techniques

An electric vehicle model has been developed with four direct-drive in-wheel motors. A high-level vehicle stability controller is proposed, which uses the principles of fuzzy logic to determine the corrective yaw moment required to minimize the vehicle sideslip and yaw rate errors. A genetic algorithm has been used to optimize the parameters of the fuzzy controller. The performance of the controller is evaluated as the vehicle is driven through a double-lane-change maneuver. Preliminary results indicate that the proposed control system has the ability to improve the performance of the vehicle considerably.
Journal Article

Design of an Advanced Traction Controller for an Electric Vehicle Equipped with Four Direct Driven In-Wheel Motors

The vision for the future automotive chassis is to interconnect the lateral, longitudinal, and vertical dynamics by separately controlling driving, braking, steering, and damping of each individual wheel. A major advantage of all wheel drive electric vehicles with four in-wheel motors is the possibility to control the torque and speed at each wheel independently. This paper proposes a traction controller for such a vehicle. It estimates the road's adhesion potential at each wheel and adjusts each motor voltage, such that the longitudinal slip is kept in an optimal range. For development and validation, a full vehicle model is designed in ADAMS/View software, in co-simulation with motor and control elements, modeled in MATLAB/Simulink.
Technical Paper

An Active Control Device Based on Differential Braking for Articulated Steer Vehicles

In this study, application of differential braking strategy to remove the oscillatory instability or snaking behavior of an articulated steer vehicle is presented. First, a linearized model of the vehicle is described that is used to represent the equations of motion in the state-space form. Then, this model is utilized for designing a sliding mode controller to adjust the differential braking on the rear axle to stabilize the vehicle during the snaking. The performance of the resulting active control system is evaluated in different driving conditions by using the linearized model. Finally, the control system is incorporated into a virtual prototype of the vehicle in ADAMS, and its operation is examined. The results from the linear model analysis and simulations in ADAMS are reasonably consistent.
Technical Paper

Fuel Cell Hybrid Control Strategy Development

Supervisory control strategies for a hybrid fuel cell powertrain are developed and simulated using Simulink models and the Powertrain Systems Analysis Toolkit (PSAT). The control strategy selects the power splitting ratio between a 65kW Hydrogenics fuel cell power module and a 70kW Cobasys Nickel Metal Hydride (NiMH) battery pack. Simple control algorithms targeting a battery pack State of Charge (SOC), or maximizing the instantaneous powertrain efficiency are initially considered and analyzed. A comprehensive control strategy optimizing powertrain efficiency, vehicle performance, emissions, and long-term reliability is then developed and simulated. The simulated vehicle using the comprehensive control strategy with reliability considerations exhibits a 21% mileage improvement as compared to a simple rule-based control algorithm.
Technical Paper

A New Air Hybrid Engine Using Throttle Control

In this work, a new air hybrid engine is introduced in which two throttles are used to manage the engine load in three modes of operation i.e. braking, air motor, and conventional mode. The concept includes an air tank to store pressurized air during braking and rather than a fully variable valve timing (VVT) system, two throttles are utilized. Use of throttles can significantly reduce the complexity of air hybrid engines. The valves need three fixed timing schedules for the three modes of operation. To study this concept, for each mode, the results of engine simulations using GT-Power software are used to generate the operating maps. These maps show the maximum braking torque as well as maximum air motor torque in terms of air tank pressure and engine speed. Moreover, the resulting maps indicate the operating conditions under which each mode is more effective. Based on these maps, a power management strategy is developed to achieve improved fuel economy.
Technical Paper

An Evaluation of the Fatigue Performance of Automotive Steels

A rapid inexpensive evaluation and comparison of the cyclic properties of three steels used in the automotive industry is presented. This evaluation ranges from the endurance limit through the transition life and low cycle regions to the monotonic results. Smooth and notched specimens, tested in strain control and load control, respectively, provide data that are used to indicate notch sensitivity and size effects, cyclic strength and ductility, and cyclic deformation response. The effect of overloads on fatigue damage is given and prestrained smooth specimens demonstrate the possible effect of a few large plastic strain cycles on fatigue resistance. Overloaded notched specimens indicate reductions in life due to both large plastic strain cycles and the induced tensile residual stress. These data are suitable for direct insertion into the design process and also provide a broad base for continuing studies of cyclic behavior.
Technical Paper

Volumetric Tire Models for Longitudinal Vehicle Dynamics Simulations

Dynamic modelling of the contact between the tires of automobiles and the road surface is crucial for accurate and effective vehicle dynamic simulation and the development of various driving controllers. Furthermore, an accurate prediction of the rolling resistance is needed for powertrain controllers and controllers designed to reduce fuel consumption and engine emissions. Existing models of tires include physics-based analytical models, finite element based models, black box models, and data driven empirical models. The main issue with these approaches is that none of these models offer the balance between accuracy of simulation and computational cost that is required for the model-based development cycle. To address this issue, we present a volumetric approach to model the forces/moments between the tire and the road for vehicle dynamic simulations.
Technical Paper

Advance Noise Path Analysis, A Robust Engine Mount Optimization Tool

Many design problems are discovered often late in the development process, when design flexibility is limited. It is the art of the refinement engineers to find a solution to any unpredicted issues at this stage. The refinement process contains many hours of testing and requires many prototypes. Having an accurate experimental model of the system in this phase could reduce refinement time significantly. One of the areas that usually require refinement and tuning late in the design process is engine and body mounting systems. In this paper, we introduce a technique to optimize the mounting system of a vehicle for a given objective function using experimental/numerical analysis. To obtain an accurate model of the vehicle, we introduce an experimental procedure based upon the substructuring method. The method eliminates the need for any accurate finite element method of the vehicle. Experimental results of the implementation of this approach to a real vehicle are presented.
Technical Paper

A Review Study of Methods for Lithium-ion Battery Health Monitoring and Remaining Life Estimation in Hybrid Electric Vehicles

Due to the high power and energy density and also relative safety, lithium ion batteries are receiving increasing acceptability in industrial applications especially in transportation systems with electric traction such as electric vehicles and hybrid electric vehicles. In this regard, to ensure performance reliability, accurate modeling of calendar life of such batteries is a necessity. In fact, potential failure of Li-ion battery packs remains a barrier to commercialization. Battery pack life is a critical feature to warranty and maintenance planning for hybrid vehicles, and will require adaptive control systems to account for the loss in vehicle range, and loss in battery charge and discharge efficiency. Failure not only results in large replacement costs, but also potential safety concerns such as overheating or short circuiting which may lead to fires.
Technical Paper

Modeling and Evaluation of Li-Ion Battery Performance Based on the Electric Vehicle Field Tests

In this paper, initial results of Li-ion battery performance characterization through field tests are presented. A fully electrified Ford Escape that is equipped by three Li-ion battery packs (LiFeMnPO4) including an overall 20 modules in series is employed. The vehicle is in daily operation and data of driving including the powertrain and drive cycles as well as the charging data are being transferred through CAN bus to a data logger installed in the vehicle. A model of the vehicle is developed in the Powertrain System Analysis Toolkit (PSAT) software based on the available technical specification of the vehicle components. In this model, a simple resistive element in series with a voltage source represents the battery. Battery open circuit voltage (OCV) and internal resistance in charge and discharge mode are estimated as a function of the state of charge (SOC) from the collected test data.
Technical Paper

Comparison of Optimization Techniques for Lithium-Ion Battery Model Parameter Estimation

Due to rising fuel prices and environmental concerns, Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) have been gaining market share as fuel-efficient, environmentally friendly alternatives. Lithium-ion batteries are commonly used in EV and HEV applications because of their high power and energy densities. During controls development of HEVs and EVs, hardware-in-the-loop simulations involving real-time battery models are commonly used to simulate a battery response in place of a real battery. One physics-based model which solves in real-time is the reduced-order battery model developed by Dao et al. [1], which is based on the isothermal model by Newman [2] incorporating concentrated solution theory and porous electrode theory [3]. The battery models must be accurate for effective control; however, if the battery parameters are unknown or change due to degradation, a method for estimating the battery parameters to update the model is required.
Technical Paper

Evaluation of Air Conditioning Impact on the Electric Vehicle Range and Li-Ion Battery Life

Despite significant progress toward application of Li-ion batteries in electric vehicles, there are still major concerns about the range of electric vehicles and battery life. Depending on the climate of the region where the vehicle is in use, auxiliary loads could also play a significant role on the battery performance and durability. In this paper, the effect of air conditioning (AC) load on the electric range and Li-ion battery life is evaluated. For this purpose, a thermodynamic model for the vehicle cabin is developed and integrated to a battery model. The thermodynamic model takes the ambient conditions, solar load, and the vehicle drive cycle as inputs and calculates the instantaneous cabin temperature and humidity. The battery model, which represents a Li-on battery pack installed on a fully electrified Ford Escape 2009, consists of a voltage source in series with a lump resistance, a thermal sub-model, and a degradation sub-model to predict the battery capacity fade.
Technical Paper

Thermal Behavior of Two Commercial Li-Ion Batteries for Plug-in Hybrid Electric Vehicles

In electrified vehicle applications, the heat generated of lithium-ion (Li-ion) cells may significantly affect the vehicle range and state of health (SOH) of the pack. Therefore, a major design task is creation of a battery thermal management system with suitable control and cooling strategies. To this end, the thermal behavior of Li-ion cells at various temperatures and operating conditions should be quantified. In this paper, two different commercial pouch cells for plug-in hybrid electric vehicles (PHEVs) are studied through comprehensive thermal performance tests. This study employs a fractional factorial design of experiments to reduce the number of tests required to characterize the behavior of fresh cells while minimizing the effects of ageing. At each test point, the effects of ambient temperature and charge/discharge rate on several types of cell efficiencies and surface heat generation are evaluated.
Technical Paper

The University of Waterloo Alternative Fuels Team's Approach to EcoCAR 2

A series plug-in hybrid electric powertrain with all-wheel drive is designed using real-world drive cycles as part of the EcoCAR 2 competition. A stock 2013 Chevrolet Malibu Eco is being re-engineered to reduce fuel consumption and emissions while improving consumer acceptability. Waterloo utilizes a 18.9 kWh A123 energy storage system (ESS), which powers two 105 kW TM4 traction motors. A 2.4 L LE9 General Motors coupled to a 105 kW TM4 motor provides range extending performance. Each step of the design process is discussed, including a novel approach to powertrain selection and controls requirement selection that uses real-world drive cycles. The mechanical integration and unique ESS design is also discussed.