Not available / text

Not available / text

To make a compelling case for government incentives as a stimulus for alternative fuel vehicle adoption, this thesis assesses the preliminary impacts associated with the elimination of Georgia’s income tax credits for low-emission and zero-emission vehicle purchases. The thesis identifies policy factors that appear to impact alternative fuel vehicle (AFV) adoption in the United States, with a focus on government incentives. Specific policy factors are discussed in the context of state and federal laws. For Georgia, motor vehicle registrations were collected to track AFV adoption rates before and after the change in law. Electric and hybrid vehicle registrations in Georgia have plummeted since the income tax credits were eliminated on June 30, 2015. Income tax credit data were collected to chart the significant increase in zero-emission and low-emission vehicle purchases and leases since electric vehicles started flooding the market. The primary outcome of this research is a set of distinct, measurable policy factors that influence AFV adoption in the United States. The factors identified include: 1) reward amount to income ratio, 2) ease of policy comprehension, 3) consumer awareness, 4) fuel/vehicle coverage of incentives, 5) incentive user groups, 6) forms of incentives (grants, income tax credits, etc.), 7) number of incentives available, and 8) dollar values of incentives. The conclusion presents factors for use in choice model estimation. These factors should be useful by policymakers who are trying to understand the true value of government incentives for alternative fuel vehicles.

Approved for public release; distribution is unlimited. / The Navy is considering the use of unmanned surface vehicles (USVs) to reduce risk to personnel in maritime interdiction operations, and to conduct intelligence, surveillance and reconnaissance (ISR) and force protection (FP) missions. In this thesis, alternative configurations of the prototype and operational uses of the USV are explored using agent-based simulation for three scenarios. An efficient experiment design alters settings of ten factors for the two ISR scenarios and 11 factors for the FP scenario. Some factors varied in the experiment are uncontrollable during operations, such as the total number of contacts, threat density, their maneuvering characteristics, and the sea state. The USV sensor range and endurance are also considered as well as factors set by the decision-maker for a particular mission: namely, USV speed and numbers to deploy. The results provide several operational and tactical insights with implications for patrolling and combat radius, and form the basis for a recommendation to use the USV in an active role in maritime missions. The results also support the guidance on the benefits of improving USV sensing and endurance capabilities, and find that simply increasing USV numbers is not necessary for attaining high mission performance. / Ensign, United States Navy

University of Technology, Sydney. Faculty of Engineering. / The thesis focuses on issues of vehicle modelling incorporating wheel-terrain interaction and low-level control design taking into account uncertainties and input time delay. Addressing these issues is of significant importance in achieving persistent autonomy for outdoor UGVs, especially when navigating on unprepared terrains. The test-bed vehicle used for this research is retrofitted from an all-terrain 20-hp, 0.5-tonne vehicle. Its driveline system consists of an internal combustion engine, continuous variable transmission (CVT), gearbox, differential, chains, and eight wheels. The vehicle is driven in the skid-steering mode, which is popular for many off-road land-vehicle platforms. In this thesis, a comprehensive approach is proposed for modelling the driveline. The approach considers the difference in speed between two outputs of the differential and the turning mechanism of the vehicle. It describes dynamics of all components in the vehicle driveline in an integrated manner with the vehicle motion. Given a pattern of the throttle position, left and right braking efforts as the inputs, the dynamic behaviour of the wheels and other components of the UGV can be predicted. For controlling the vehicle at the low level, PID controllers are firstly used for all actuators. As many components of the vehicle exhibit nonlinearities and time delay, the large overshoots encountered in the outputs can lead to undesirable vehicle behaviours. To alleviate the problem, a novel control approach is proposed for suppression of overshoots resulting from PID control. Sliding mode control (SMC) is employed, for this, with time delay compensated by using an output predictor. As a result, the proposed approach can improve significantly system robustness and reduce substantially step response overshoot. Notably, the design is generic in that it can be applied for many dynamic processes. Knowledge of the interaction between the UGV and the terrain plays an important role in increasing its autonomy and securing the safety for off-road locomotion. In this regard, vehicle kinematic equations are combined with the theory of terramechanics for dynamic modelling of the interaction between the vehicle wheels and a variety of terrain types. Also, a fast algorithm is developed to enable online implementation. The novel interaction model takes into account the relationship between normal stresses, shear stresses, and shear displacement of the terrain that is in contact with the wheels in deriving the three-dimensional reaction forces. Finally, all modelling and control algorithms are integrated into a unique simulator for emulating the vehicle mobility characteristics. In particular, the wheel’s slip and rolling resistance can also be derived to provide useful information for closed-loop control when the UGV is navigating in an unknown environment. The simulator, as a tool for analysing the vehicle mobility, is helpful for further research on relevant topics such as traction control, safe and effective locomotion.

Bibliography: leaves 220-229. / xxiv, 229 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates alternative reusable launch vehicle design concepts and develops a robust guidance strategy for use on the ascent and flyback phases of flight. The first concept vehicle uses air breathing engines to perform a powered return flight to the launch site; the second employs only aerodynamic forces to achieve flyback, returning unpowered. Software simulation shows that a powered return flight delivers more payload than an unpowered return flight. The guidance strategy developed is a numerical guidance system robust enough for use in real time and works by integrating the current state, along the trajectory, to the final state of the vehicle. It then compares the achieved final state to the required target state and calculates the target condition error. A parameterised non-linear optimisation technique is then used to determine the new values of the optimisation parameters required to steer the vehicle from its current position and velocity to the desired position and velocity. / Thesis (Ph.D.)--University of Adelaide, School of Mechanical Engineering, 2003

University of Technology, Sydney. Faculty of Engineering. / The thesis focuses on issues of vehicle modelling incorporating wheel-terrain interaction and low-level control design taking into account uncertainties and input time delay. Addressing these issues is of significant importance in achieving persistent autonomy for outdoor UGVs, especially when navigating on unprepared terrains. The test-bed vehicle used for this research is retrofitted from an all-terrain 20-hp, 0.5-tonne vehicle. Its driveline system consists of an internal combustion engine, continuous variable transmission (CVT), gearbox, differential, chains, and eight wheels. The vehicle is driven in the skid-steering mode, which is popular for many off-road land-vehicle platforms. In this thesis, a comprehensive approach is proposed for modelling the driveline. The approach considers the difference in speed between two outputs of the differential and the turning mechanism of the vehicle. It describes dynamics of all components in the vehicle driveline in an integrated manner with the vehicle motion. Given a pattern of the throttle position, left and right braking efforts as the inputs, the dynamic behaviour of the wheels and other components of the UGV can be predicted. For controlling the vehicle at the low level, PID controllers are firstly used for all actuators. As many components of the vehicle exhibit nonlinearities and time delay, the large overshoots encountered in the outputs can lead to undesirable vehicle behaviours. To alleviate the problem, a novel control approach is proposed for suppression of overshoots resulting from PID control. Sliding mode control (SMC) is employed, for this, with time delay compensated by using an output predictor. As a result, the proposed approach can improve significantly system robustness and reduce substantially step response overshoot. Notably, the design is generic in that it can be applied for many dynamic processes. Knowledge of the interaction between the UGV and the terrain plays an important role in increasing its autonomy and securing the safety for off-road locomotion. In this regard, vehicle kinematic equations are combined with the theory of terramechanics for dynamic modelling of the interaction between the vehicle wheels and a variety of terrain types. Also, a fast algorithm is developed to enable online implementation. The novel interaction model takes into account the relationship between normal stresses, shear stresses, and shear displacement of the terrain that is in contact with the wheels in deriving the three-dimensional reaction forces. Finally, all modelling and control algorithms are integrated into a unique simulator for emulating the vehicle mobility characteristics. In particular, the wheel’s slip and rolling resistance can also be derived to provide useful information for closed-loop control when the UGV is navigating in an unknown environment. The simulator, as a tool for analysing the vehicle mobility, is helpful for further research on relevant topics such as traction control, safe and effective locomotion.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 97-99). Also available on the World Wide Web.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 49-53).

Thesis (M.A.)--Naval Postgraduate School, Monterey, Calif., 2001. / "September 2001." Includes bibliographical references (p. 87-90). Available also online as a PDF file via the World Wide Web.