Search Results

This paper proposes a vehicle performance/safety method using combined active steering and differential braking to achieve yaw stability and rollover avoidance. The advantages and disadvantages of active steering and differential braking control methods are identified under a variety of input signals, such as J-turn, sinusoidal, and fishhook inputs by using the implemented linear 4 DOF model. Also, the nonlinear model of the vehicle is evaluated and verified through individual and integrated controller. Each controller gives the correction steering angle and correction moment to the simplified steering and braking actuators. The integrated active steering and differential braking control are shown to be most efficient in achieving yaw stability and rollover avoidance, while active steering and differential braking control has been shown to improve the vehicle performance and safety only in yaw stability and rollover avoidance, respectively.

Bonded structures, such as honeycomb sandwich, are becoming an important construction technique in the light aircraft industry. Designers can now select from a vast array of materials to meet almost any design criteria. Some guidelines in material selection, tooling and fabrication methods, and the economics of sandwich construction are presented to aid persons responsible for each of those areas.

Aircraft wing geometry morphing is a technology that has seen recent interest due to demand for aircraft to improve aerodynamic performance for fuel saving. One proposed idea to alter wing geometry is by a modular morphing wing designed through a discretization method and constructed using variable geometry truss mechanisms (VGTM). For each morphing maneuver, there are sixteen possible actuation paths for each VGTM module. This paper proposes a method to find an optimal actuation path from the point of view of the longitudinal static stability. To do so, we locate the aerodynamic center (ac) and the center of gravity (cg) of each VGTM module which is first determined according to its morphed shape. Then, the ac and cg of the entire modular morphing wing can be determined and the stability margin can be computed. The two suggested methods to obtaining the ac for each VGTM module are the integration method and the geometry method.

Automobiles of the future will be forced to travel further on a tank of fuel while discharging lower levels of pollutants. Currently, the United States uses in excess of 18 million barrels of petroleum per day. Sixty-six percent is used in the transportation of people and goods. Highway vehicles currently account for just under two-thirds of the nation's gasoline consumption, and about one-third of the total United States energy usage [1] while contributing a significant amount to the annual U.S. air pollutant burden. In 1997, 57.5% of the carbon monoxide, 29.8% of the nitrogen oxides, 27.2% of the volatile organic compounds, and 23.8% of the carbon dioxide came from highway vehicles [2] The U.S. government has supported R&D pertinent to highway vehicles since the early 1960's, to mitigate these problems.

Accurate knowledge of diesel particulate filter (DPF) particulate matter (PM) loading is critical for robust and efficient operation of the combined engine-exhaust aftertreatment system. Furthermore, upcoming on-board diagnostics regulations require on-board technologies to evaluate the status of the DPF. This work describes the application of radio frequency (RF) - based sensing techniques to accurately measure DPF particulate matter levels. A 1.9L GM turbo diesel engine and a DPF with an RF-sensor were studied. Direct comparisons between the RF measurement and conventional pressure-based methods were made. Further analysis of the particulate matter loading rates was obtained with a mass-based total PM emission measurement instrument (TEOM) and DPF gravimetric measurements.

The uniaxial compression test was used to assess the influence of strain amount on the behavior of precipitates and texture of the Al-7%Si-1%Cu-0.5%Mg alloy, modified with micro-additions of V, Zr and Ti. As revealed through metallographic examinations, fracturing and re-orientation of the second-phase particles increased with increasing compression strain. However, the intermetallic particles experienced substantially more frequent cracking than the eutectic silicon. The crystallographic texture was measured and correlated with deformation behavior of the alloy. The weak texture of 11<211> and 111<110> components, detected after casting transformed to a mixture of 1<110>, 112<110> and 111<110> components after room-temperature compression deformation. The intensity of the texture components depended on the strain amount. It is concluded that the texture formation in the studied alloy is controlled by the precipitates formed during solidification of the alloy.

With the prevalence of more electrical aircraft (MEA), aircrafts are more vulnerable to electrical system faults. The proactive Condition Based Maintenance (CBM) for aircraft electrical systems has become an issue of substantial importance and urgency. Although certain aspects of CBM have been implemented with considerable success, CBM for aircraft electrical systems is still at its early stage of development. Diagnostic and prognostic technologies need to be improved to meet CBM requirements. This paper reviews the existing studies on the CBM for aircraft electrical systems in terms of its concept, content, requirements, hierarchy, methodologies and system configuration, and is intended to provide a technology survey particularly on the state of the art and challenging issues of aircraft electrical system CBM.

Although designed for the purpose of reducing engine-out Particulate Matter (PM) emissions to meet or exceed mandated emissions regulations, the particulate filter also incurs a fuel economy penalty. This fuel penalty is due to the increased exhaust flow restriction attributed to the PM accumulated in the filter, in addition to fuel consumed for active regeneration. Unlike the soot which may be oxidized through the regeneration process, incombustible material or ash continues to build-up in the filter following each regeneration event. Currently pressure- and model-based controls are used to provide an indirect estimate of the loading state of the particulate filter, in order to manage the filter operation and determine when to regenerate the filter. The challenges associated with pressure- and model-based particulate filter control over real-world operating conditions are well-known.

This paper provides an overview of recent developments in the area of arc fault detection (AFD) and wire fault location for aircraft wiring systems. Arc faults have been identified as one of the greatest threats to human lives and properties, and the likely cause of several aircraft disasters. With the introduction of high voltage transmission in aircraft to reduce the wiring weight and to meet the increasing power demands, the probability of initiating and sustaining continuous arcs in modern aircraft have been increased. However, arc faults are hard to detect and wiring problems are difficult to locate in aircraft, due to their complex profiles, high impedance property, and pressure sensitive characteristic, etc. The difficulty in resolving this problem is also due to the fact that false alarms cannot be tolerated but missing alarms can be fatal, and arc faults are normally intermittent as a result of the in-flight vibration.

Presented in this paper is a framework for the implementation of a robotic percussive riveting system, a new robot application for aircraft assembly. It is shown here that a successful robot application to the automation of a process requires in-depth research of the process and the interaction with the robot. For this purpose, a process planning-driven approach is proposed to guide a robot application research. A typical process planning will involve a list of key considerations including: process sequence, process parameters, process tooling, and process control. Through this list, a number of key research issues are identified for robotic percussive riveting, such as rivet pattern planning, riveting time determination, riveting tooling design and rivet insertion control. The detailed research on these issues has effectively created know-how for the successful implementation of our robotic percussive riveting system.