Mark O. Bodie

Improvements in vehicle handling through integrated control of chassis systems

In this paper methods of improving vehicle stability and emergency handling using electronically controlled chassis systems are discussed. By analysing a simple nonlinear vehicle model in the yaw plane, it is shown that vehicles can become unstable during portions of handling manoeuvres performed at or close to the limit of adhesion. It is further demonstrated how small changes in the balance of tyre forces between front and rear axles may affect vehicle yaw moment and stability. The methods of effecting vehicle yaw dynamics using controllable brakes, steering, and suspension are discussed. Control authority of each chassis system, in terms of its ability to generate a corrective yaw moment, is evaluated and is shown to depend on the operating point of vehicle and tyres. Consequently, regions of effectiveness of each subsystem are defined, which is a prerequisite for development of integrated chassis control systems. Preliminary test results for a vehicle with integrated closed loop control of brakes and suspension, performing typical handling manoeuvres, are presented. They demonstrate the benefits of integrated control in terms of improved handling response, stability, and reduced driver steering effort.

Thermal Analysis of an Integrated Aircraft Model

The INVENT Phase I efforts have focused strongly on the development of high fidelity aircraft modeling and simulation capabilities. As a part of this initiative, AFRL has undertaken the development, integration and demonstration of a mission level tip-to-tail thermal model. The major components of the integrated model include the Air Vehicle System (AVS), the Fuel Thermal Management System, the engine models, and Power Thermal Management System (PTMS). The integrated model is then flown over a complete aircraft flight mission from ground idle thru take-off, climb, cruise, descent, landing and post-flight ground hold. Having established a baseline level of performance for the aircraft PTMS system over the full mission length, the PTMS model is then exercised to investigate some possible design space trades. The trades include varying the engine bleed air demand for an aircycle design as well as comparing the air cycle performance to a representative vapor cycle design. The design trades are an effort to highlight the potential application of the integrated system model. This, first in a series of research investigations, is not constrained to actual hardware components. The components in this system are representative of modern/future aircraft. The motivation is to stimulate additional dialog and discussion as to the benefits of integrated aircraft system analysis with the long term goal of achieving a design system capable of analyzing future energy optimized aircraft.

An adaptive strategy for vehicle vibration and noise cancellation

The desire for increased comfort in both ride and quietness of passenger vehicles is receiving increased attention. To address this concern we develop an active system for vibration control that reduces vibrations on the body and simultaneously reduces noise inside the passenger cabin. The algorithm development is based upon well known principles from adaptive filter theory. The hardware implementation within a concept vehicle dedicated to noise and vibration research is presented. To gain insight with regard to vibration control, experimental modal vibration data are quantified to derive a forced response prediction model. As part of this work we investigate an approach to positioning cancellation forces on the vehicle structure in order to achieve the best noise and vibration reduction performance. Although the technology to date has limitations primarily due to situational physics, we present representative test results which show promise for the prescribed approach to active control of engine and chassis vibrations.