This study focuses on developing an assessment tool for the performance prediction of lightweight autonomous vehicles
with varying locomotion platforms on coastal terrain involves three segments. A table based on the House of Quality
shows the relationships - high, low, or adverse - between mission profile requirements and general performance
measures and geometries of vehicles under consideration for use. This table, when combined with known values for
vehicle metrics, provides information for an index formula used to quantitatively compare the mobility of a user-chosen
set of vehicles, regardless of their methods of locomotion. To study novel forms of locomotion, and to compare their
mobility and performance with more traditional wheeled and tracked vehicles, several new autonomous vehicles -
bipedal, self-excited dynamic tripedal, active spoke-wheel - are currently under development. While the terramechanics
properties of wheeled and tracked vehicles, such as the contact patch pressure distribution, have been understood and
models have been developed for heavy vehicles, the feasibility of extrapolating them to the analysis of light vehicles is
still under analysis. wheeled all-terrain vehicle and a lightweight autonomous tracked vehicle have been tested for
effects of sand gradation, vehicle speed, and vehicle payload on measures of pressure and sinkage in the contact patch,
and preliminary analysis is presented on the sinkage of the wheeled all-terrain vehicle. These three segments -
development of the comparison matrix and indexing function, modeling and development of novel forms of locomotion,
and physical experimentation of lightweight tracked and wheeled vehicles on varying terrain types for terramechanic
model validation - combine to give an overall picture of mobility that spans across different forms of locomotion.
Proc. SPIE. 6564, Modeling and Simulation for Military Operations II
KEYWORDS: Mathematical modeling, Unmanned aerial vehicles, Fluctuations and noise, Data modeling, Kinematics, Modeling and simulation, Chemical elements, Failure analysis, Performance modeling, Systems modeling
A multibody dynamics model of a Vertical Take-off and Landing (VTOL) Unmanned Aerial Vehicle (UAV) is presented
in this study. The scope of the project was to investigate a lightweight landing gear which has a stable and robust landing
performance. Two original designs of the landing gear for the module of interest have been modeled and analyzed in this
study. Two new designs have also been developed, modeled, and analyzed. A limited analysis of the forces that occur in
the legs/struts has also been performed, to account for possible failure of the members due to buckling.
The model incorporates a sloped surface of deformable terrain for stability analysis of the landing scenarios, and
unilateral constraints to model the ground reaction forces upon contact. The lift forces on the UAV are modeled as
mathematical relations dependent on the speed of the ducted fan to enable the variation of the impact velocities and the
different landing scenarios.
The simulations conducted illustrate that initial conditions at landing have a big impact on the stability of the module.
The two new designs account for the worst possible scenario, and, for the material properties given, end with a larger
weight than the one of the original design with three legs and a ring. Simulation data from several landing scenarios are
presented in this paper, with analysis of the difference in performance among the different designs.
The primary purpose of this study is to provide a comprehensive experimental analysis of how various popular semiactive control methods perform when used with magneto rheological dampers. Specifically, the performance of five different skyhook control methods is studied experimentally, using a single suspension test rig. The control methods that are analyzed include: skyhook control, groundhook control, hybrid control, displacement skyhook, and relative displacement skyhook. For a MR damper, this paper provides an in-depth analysis of how these semiactive control methods perform at the sprung and unsprung mass natural frequencies, using the single suspension test rig. Upon evaluating the performance of each control method in frequency domain for various conditions, they are compared with each other as well as with passive damping. The results indicate that no one control method outperforms others at both the sprung and unsprung mass natural frequencies. Each method can perform better than the other control methods in some respect. Hybrid control, however, comes close to providing the best compromise between different dynamic demands on a primary suspension. The results indicate that hybrid control can offer benefits to both the sprung and unsprung mass with control gain settings that provide equal contributions from skyhook control and groundhook control.
Proc. SPIE. 5760, Smart Structures and Materials 2005: Damping and Isolation
KEYWORDS: Digital filtering, Complex systems, Control systems, System identification, Dynamical systems, Algorithm development, Adaptive control, Nonlinear filtering, Systems modeling, Nonlinear control
The primary purpose of this paper is to present the theories leading to the development of a semiactive adaptive controller for nonlinear systems. The adaptive algorithm developed in this paper is applied to one class of nonlinear vibration systems, namely semiactive base-excited vibration isolation systems. The algorithm includes the on-line system identification and the adaptation of the control signal. Finally, the stability of the semiactive adaptive system is presented.