Modeling and control of an electromechanical brake (brake -by -wire) system
Abstract
This thesis focuses on two practically important issues associated with the development of an electromechanical brake (EMB, Brake-by-wire) and its safety control in early design stage. The first issue is the development of an analytical dynamic model which should have all relevant degrees of freedom without being unnecessarily complex so as to be useful in PC simulation environment. This objective is achieved through the analytical model development of all relevant hardware components of EMB and modal analysis of its linearized approximation for model reduction. This model fulfills the need arising due to the nonexistence of an analytical model for EMB. The developed model has six degrees of freedom (DOF) and includes essential nonlinearities such as gear backlashes, Coulomb frictions, and disk air gap clearance. The second issue is concerned with the safety control of EMB, either in case of force sensor failure or without using expensive force sensor for cost-saving purposes. To establish a force feedback structure without using force sensor, two simplified models are developed for contacting phase and non-contacting phase respectively, and a novel model based edge detection method is proposed and evaluated. Various parameter estimations are then performed to find realistic ways to obtain accurate and reliable estimates of key system parameters on-line to deal with the large operating ranges and changing working conditions of EMB. In addition, to deal with various nonlinearities and uncertain system parameters associated with an EMB, an advanced indirect adaptive robust controller (IARC) incorporated with the air gap management is designed for the entire brake operation to ensure a robust control performance. Extensive simulation results are provided to verify the effectiveness of the analytical model and the achievable control performance of the imbedded IARC design without force sensor. Simulation results reveal that, in terms of transient tracking performance for ABS cycling, the proposed IARC clamping force controller without using force sensor shows much better results than the conventional PI controller with using force sensor. Thus, aside from the benefit of providing a fail-safe control strategy for force sensor failure, a much more stringent ABS cycle than currently used can be achieved with the proposed IARC to improve the friction force between the tire and the road for a shorter stopping distance. Such a much improved clamping force control performance is also vital for future advanced vehicle control using EMB.
Degree
Ph.D.
Advisors
Bajaj, Purdue University.
Subject Area
Mechanical engineering
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