Nonlinear modeling and h-infinity model reference control of pneumatic suspension system

摘要

The objective of this thesis research is to analyze the pneumatic suspension systems to improve their vibration isolation performance. The work presented in this thesis addresses modeling, analysis and control of the pneumatic suspension system. First, the static and dynamic characteristics of a generic pneumatic suspension system are studied, followed by the development of a nonlinear model of the pneumatic suspension system for multiple operating conditions. An air spring- accumulator system has various dynamic nonlinearities which are explored extensively through numerous simulations as well as exhaustive experimental work. One of the main objectives of this work was to better understand the physics behind the operation of air spring-accumulator system, obtain reliable math model, and develop effective control design for such systems. In terms of of the controller design, a control-oriented analytical model is obtained by the system identification techniques. Then, a model reference H-infinity controller design is presented based on the system-id where control input is the modulation of orifice opening using an electronically-controlled proportional solenoid valve. The experimental results show that the closed-loop system with designed controller significantly improved the vibration isolation performance over a wide frequency range. It is shown that the inherent vibration isolation characteristics of air spring-accumulator system can be exploited through careful modeling and advanced control design. The pneumatic system offers a much economical and easy way to maintain low weight isolation system for various applications such as over the road trucks, automobiles, gurneys. etc. Finally, potential enhancements to the system are proposed for future work.