Antilock Brake System based on Sliding Mode Observer


Professor Emeritius William B. Ribbens


Department of Aerospace Engineering

and Electrical Engineering

and Computer Science


University of Michigan


An antilock brake system (ABS) for transport category aircraft is presented that derives control signals from a sliding mode observer (SMO). The long-term goal of the research on this subject has been to develop electrically activated ABS (brake by wire) for such aircraft, although the methodology is potentially also applicable to land vehicles.


In this talk, empirically derived models are developed for aircraft braking during normal landing and during refused takeoff scenarios.  The SMO is used to estimate braking torque and vehicle velocity.  The control system regulates applied brake force to maximize braking drag force thereby optimizing vehicle deceleration.  The ABS System functions without any prior knowledge of or measurement/estimate, made of tire/runway friction characteristics.


Of particular interest is the control methodology for suppressing a nonlinear oscillation of the landing gear known as “gear walk” that is a major technical obstacle in development of aircraft ABS systems.  Performance of a prototype system has been evaluated based upon 1) matlab simulation and 2) hardware in the loop simulation using a prototype brake configuration for a representative regional jet. Results are presented of the system performance with both electro-hydraulic and electrically activated brake actuators.


Friday, February 15, 2002

3:30 - 5:00 p.m.

1500 EECS