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This paper describes a multi-degree-of-freedom model of a three-wheeled car implemented in Matlab®. The purpose was to investigate the dynamics of the car (assumed to be rigid on its suspension) during cornering. While the problems associated with three-wheeled cars are well known, much of the guidance in the literature and off-the-shelf software assumes a conventional four-wheeled car. Consequently, the authors were approached with a battery-electric concept car which was thought to offer better performance than the existing variants because the use of hub motors lowered the center of gravity and, hence, reduced rollover coefficient. However, simulation of the vehicle model in cornering shows that the concept is still prone to instability. Indeed, it suffers greater roll velocities than a comparable three-wheeled car with an internal combustion engine (ICE) because the ratio of sprung to unsprung mass is significantly altered.

Transport Refrigeration Unit, or TRU, is an example of a diesel emission source that will be regulated in the future. The TRU is used to provide refrigerated space during the transport of fruits, vegetables, meat, pharmaceuticals, beverages, and any other product that needs a temperature controlled environment while being transported. TRUs are used in all modes of transport, on rail cars, on ocean going shipping containers, over the road truck trailers and even on airplane Unit Load Devices. Policy making bodies, understanding the adverse effects of diesel emissions, noise pollution, and fuel consumption have started to pass legislation in an effort to curtail transport diesel emissions. At the local level many states as well as some municipalities have instituted policy designed to eliminate these sources of pollution.

In this paper a model of Trailer Refrigeration Units, TRUs, has been developed to quantify the fuel economy and emissions benefits of alternative power systems. Trailer refrigeration units (TRUs) are refrigeration systems typically powered by a separate diesel engine, and they are used to deliver fresh and frozen food products. The products can be very sensitive to temperature variation and maintaining the proper environment is very important. The diesel engines currently used to power the refrigeration system can contribute to high amount of local emissions at the loading warehouse. A promising future alternative is the use of fuel cell auxiliary power units (APUs). In this paper we have developed a MATLAB/Simulink based modeling of TRUs, and we have used the model to quantify the benefits of alternative power systems. The simulation model consists of an unsteady thermal modeling of TRUs that is coupled to the APU.

HEVs historically have had reduced performance at elevations higher than sea level. The effects of this loss of performance can be mediated with the use of a standard turbocharger; however, approximately 80-90% of the vehicle's operation is at altitudes where full boost from the turbocharger is not needed to maintain performance characteristics comparable to conventional vehicles of the same size. If the turbocharger is used to drive an electric generator, the power produced by the turbine section that is not needed to produce boost in the compressor section of the turbocharger can be used to charge the traction battery of HEVs. The Exhaust Gas Driven Generator converts the thermal energy, normally wasted through the exhaust of the ICE, to electrical energy stored in the traction battery of the HEV.

This paper focuses on the impact of proper thermal integration between two major components of the indirect methanol fuel cell vehicle fuel processor (reformer and burner). The fuel processor uses the steam reformation of methanol to produce the hydrogen required by the fuel cell. Since the steam reformation is an endothermic process, the required thermal energy is supplied by a catalytic burner. The performance of the fuel processor is very strongly influenced by the extent of thermal integration between the reformer and burner. Both components are modeled as a set of CSTRs (Continuous Stirred Tank Reactors) using Matlab/Simulink. The current model assumes no time lag between the methanol sent into the reformer and the methanol sent into the burner to generate the necessary heat for the reformer reactions to occur.

Vehicle manufacturers claim that fuel cell vehicles are significantly more fuel-efficient and emit fewer emissions than conventional internal combustion engine vehicles /1/. A computer model can help to explore and understand the underlying reasons for this potential improvement. In previous published work, the UC Davis Vehicle Model for the case of a load-following Indirect Methanol Fuel Cell Vehicle (IMFCV) has been introduced and discussed in detail /2/. Because of possible technical barriers with load following vehicles, as well as near term cost issues, hybrid fuel cell vehicle concepts are widely discussed as another fuel cell vehicle option. For load following vehicles, the questions of fast start up and fuel processor dynamics in extreme transient situations, (e.g., during phases of hard acceleration) are not totally resolved at this time. For both of these performance issues, a hybrid design could offer at least an interim solution.

Near term (ca. 2005) Fuel Cell Vehicles (FCVs) will primarily utilize Direct-Hydrogen Fuel Cell (DHFC) systems. The primary goal of this study was to provide an analytical basis for including a realistic Compressed Hydrogen Gas (CHG) fuel supply simulation within an existing dynamic DHFC system and vehicle model. The purpose of this paper is to provide a tutorial describing the process of modeling a hydrogen storage system for a fuel cell vehicle. Three topics were investigated to address the delivery characteristics of H2: temperature change (ΔT), non-ideal gas characteristics at high pressures, and the maximum amount of hydrogen available due to the CHG storage tank effective “state-of-charge” (SOC) -- i.e. how much does the pressure drop between the tank and the fuel cell stack reduce the usable H2 in the tank. The Joule-Thomson coefficient provides an answer to the expected ΔT during expansion of the H2 from 5000 psi to 45 psi.

The University of California, Davis FutureTruck team redesigned a 2000 Chevrolet Suburban as a Hybrid Electric Vehicle to meet the following goals: reduce fuel cycle greenhouse gas emissions by 66%, increase vehicle fuel economy to double that of the stock Suburban, meet California's Super Ultra Low Emissions Vehicle standard, and qualify for substantial Partial Zero Emissions Vehicle credits in California. Sequoia meets these goals with an efficient powertrain, improved component systems, and an advanced control system. Sequoia utilizes two independent powertrains to provide Four-Wheel Drive and achieve stock towing capacity. The primary powertrain combines a 1.9L gasoline engine inline with a 75 kW brushless DC motor driving the rear wheels. This powertrain configuration is simple, compact, reliable, and allows flexibility in control strategy. The secondary powertrain employs a 75 kW brushless DC motor to drive the front differential.

At the present time there are rapid changes occurring in the fleets of transit buses that are used in cities. These changes involve improvements in conventional diesel buses, Compressed Natural Gas, CNG, and more recently hybrid electric vehicles. In order to evaluate the performance of the transit buses, driving cycles have been developed, and two of the most popular are the New York City, NYC, and the Central Business District, CBD. These cycles have proven to be very valuable for predicting both performance and emissions of the transit buses, however they do not well characterize some of the unique characteristics of certain cities, such as San Francisco with its hills and high grade. In this paper we present the results of Chassis dynamometer measurements and modeling of the performance of four different types of transit buses on the typical grades that exist in San Francisco.

Yosemite is an advanced hybrid electric vehicle built on the Ford U152 Explorer platform. The University of California, Davis, FutureTruck team designed Yosemite to meet the following objectives: 1 Maximize vehicle energy efficiency 2 Minimize petroleum consumption 3 Reduce fuel cycle greenhouse gas emissions 4 Achieve California Super Ultra Low Emission Vehicle (SULEV) target 5 Deliver class-leading performance The University of California, Davis FutureTruck team redesigned a 2002 Ford Explorer as a Hybrid Electric Vehicle to meet the following goals: reduce fuel cycle greenhouse gas emissions by 67%, double the fuel economy of a stock Explorer, meet California's Super Ultra Low Emissions Vehicle standard, and qualify for substantial Partial Zero Emissions Vehicle credits in California. Yosemite meets these goals with an efficient flexible fuel hybrid powertrain, improved component systems, and an advanced control system.

The problem of vehicle stability in emergency maneuvers has attracted a lot of research effort recently. Perhaps the most effective contributions made in this area were devoted to the control of vehicle yaw rate either by active steering or differential braking control systems. Each control technique has its own limitations that make it ineffective in some particular situations. This paper introduces a combined steering and braking control strategy using a fuzzy logic inference system. The proposed controller uses the estimated coefficient of friction (μ) to organize the combined control action. Computer simulation using a comprehensive vehicle model is used to illustrate the strengths and limitations of various control strategies.

The last few years have been an exciting time for alternative vehicle development. New concerns about the environmental impact of personal transportation and about the United States' dependence on imported oil have pushed energy efficient, ultra-low, and zero emissions vehicles to the forefront of automotive design. California's own mandate for Zero Emissions Vehicles (ZEV) takes effect in 1998, creating a tremendous push towards the difficult goal of producing a commercially viable, practical electric vehicle for sale in 1998. Beyond California, most of the world's automakers are simultaneously committing tremendous research and development resources towards the technology necessary for a viable electric vehicle. The University of California at Davis is one of seven California universities participating in the 1993 Ford Hybrid Electric Vehicle Challenge.

This paper presents experimental data and an analysis of a proton exchange membrane fuel cell system for electric vehicle applications. The dependence of the fuel cell system's performance on air stoichiometry, operating temperature, and reactant gas pressure was assessed in terms of the fuel cell's polarity and power density-efficiency graphs. All the experiments were performed by loading the fuel cell with resistive heater coils which could be controlled to provide a constant current or constant power load. System parasitic power requirements and individual cell voltage distribution were also determined as a function of the electrical load. It was found that the fuel cell's performance improved with increases in temperature, pressure and stoichiometry within the range in which the fuel cell was operational. Cell voltage imbalances increased with increases in current output.

Several lead-acid battery packs of different manufacture and voltage were evaluated on a performance and life-cycle basis. The battery packs ranged from a small 36 volt laboratory pack to a 320 volt full size U.S. Electricar S-10 truck pack. The influence of the charge algorithm, ambient temperature, and module connection methods for parallel strings on the performance and cycle-life of this laboratory pack was studied. Finally, a survey of presently employed battery management techniques, used in three “production” electric vehicles, was conducted. A standard set of testing procedures for electric vehicle batteries, based on industry accepted testing procedures, were used in the evaluations. The battery packs were evaluated by a combination of constant current capacity tests, cyclical loading to simulate typical EV driving cycles and actual EV driving experience.

The zinc bromine battery is a high energy density sealed battery that utilizes a flowing electrolyte and low cost materials (predominantly plastic) and operates at ambient temperatures. The typical full scale specific energy for this bipolar plate battery is more then twice that of lead acid batteries. The engineering research presented in this paper is the design and construction of a high-voltage, zinc bromine battery for use in an electric vehicle. Specifically, a 390 volt system is being integrated into a US Electricar S10 light-duty truck. The research goal is to show a reliable and practical electrochemical power system that is lighter and provides a longer range and shorter recharge times than lead acid batteries. Results of this study will help determine the applicability and practicality of zinc bromine technology for electric vehicles.

An optimal control design method is introduced and then applied to the optimum design of active and passive suspension systems. A basic three-dimensional 7-DOF car riding model is considered. The method allows the arbitrary choice of sensors for various state variables to be used for feedback control of each suspension unit. Fully-active, limited-active, passive, and two versions of semi-active systems are studied and compared. The results indicate that the dominant feedback gains that have the most impact on the suspension performance measures are those which are proportional to locally measured signals. Also, when no tire deflection measurements are available there may be a complete coincidence between the behaviour of active systems that use different sets of measured variables.

It is commonly accepted that the principal functions of an automobile suspension are to control low frequency rigid body motions, provide comfort to passengers, and to reduce tire normal force variation so that predictable handling is maintained. A good argument for reducing normal force variation is that in the extreme, if a tire is off the ground, it for certain cannot generate any lateral forces, and thus compromises lateral dynamics. The direct relationship between road holding and dynamic tire normal force variation is quantified sparsely in the literature. In this paper a relatively simple model is proposed which exposes how normal force variation at the front and rear directly affects the vehicle yaw rate and lateral acceleration. It is shown that normal force variation at the front has potentially the same effect on lateral dynamics as does the steering input.

The objective of this research is to create a new brake system with fewer mechanical parts, higher performance, greater flexibility for adaptation to new functions, and lower cost. A simple/series electro-hydrostatic brake system is investigated as an inexpensive, reliable, and redundant integrated brake system that can include the functions; Boost, ABS, TCS, VDC, etc. Production issues are considered. The required motor power is the most critical and is estimated by simulation based on data from experiments. To reduce this power a flow boost self-energizing mechanism with computer control is explored, and it is found that the effect is significant. Robustness of the control for pad friction fluctuation is also analyzed, and the limitation is estimated. The result of analysis shows that a competitive commercial product can be developed.

A plug-in, charge-depleting, parallel hybrid powertrain has been developed for a high performance sport utility vehicle. Based on the Ford U152 Explorer platform, implementation of the hybrid powertrain has resulted in an efficient, high performance vehicle with a 0-60 mph acceleration time of 7.5 seconds. A dual drive system allows for four-wheel drive capability while optimizing regenerative braking and minimizing electric motor cogging losses. Design of the system focused on reducing petroleum use, lowering greenhouse gas emissions, and reducing criteria tailpipe emissions. Additionally, this vehicle has been designed as a partial zero emissions vehicle (PZEV), allowing the driver to travel up to 50 miles in a zero emission all-electric mode. High-energy traction battery packs can be charged from the grid, yielding higher efficiencies and lower critical emissions, or maintained through the internal combustion engine (ICE) as with a traditional hybrid vehicle.

This paper is a comprehensive comparative analysis of methanol, compressed natural gas, and liquefied natural gas as automotive fuels. First, we examine natural gas, coal, and biomass feedstocks, and the “security” of foreign feedstocks. Next, vehicle performance and emissions are considered, followed by an analysis of vehicle refuelling and storage technology. Environmental impacts of fuel production and distribution are analyzed; followed by a review of health, flammability, transport, and end-use hazards. We perform a detailed cost analysis that combines fuel cost and vehicle cost into discounted life-cycle cost-per-mile. Finally, we discuss the feasibility and implications of transitions to methanol and natural gas from our current vehicular fuel system. We find that natural gas vehicles may offer slight economic and environmental advantages, but that a transition to natural gas fuel would be more difficult, at least in the U.S.