Design and performance analysis of an adaptive anti-skid braking system for large aircraft

lt is the author's contention that a brake control system incorporating the following two features is suitable for high-performance, robust and adaptive anti-skid control. 1. Switching on wheel acceleration with hysteresis, 2. Fixed brake pressure rate control. Furthermore, the author contends that such a system can be developed in the context of large commercial aircraft development and with regard to; Minimal a-priori knowledge of system dynamics, I No requirement for on-line system identification. This thesis documents a programme of research conducted to examine this hypothesis in the context of large commercial aircraft, and in conjunction with Airbus UK at Filton in Bristol. The physical basis for this method of control is examined from first principles, explored in detail through a simulation based experimental process and is subsequently confirmed as a viable means of control. This is further developed into a prototype anti-skid braking control algorithm which in turn is incorporated into a nominal brake control system model. A detailed analysis of the systems performance is then conducted and reported upon. Finally, conclusions are drawn with respect to the aims and objectives documented herein and recommendations for further research are made. The novel aspects of this hypothesis and subsequent algorithm development are as follows, and are to be considered with respect to the current state-of-the-art in the field:

1. The use of a fixed brake pressure rate control to isolate the friction dependent aspects of the system dynamics,
2. The use of a simple switching element which incorporates hysteresis such that when combined with l, allows robust -slip gradient control* to be effected, and
3. The use of brake system response characteristics to drive an optimal wheel acceleration demand signal. The author believes that these three aspects of the anti-skid braking algorithm documented within this thesis combine to provide an effective and pragmatic solution to the problem, and represent a step forward in the state of- the-art as is befitting a research programme of EngD character. 'The gradient of the -slip (friction coefficient vs. wheel slip ratio) curve is controlled.