Development and control of a prototype pneumatic active suspension system

Real physical plants for control experimentation are valuable tools in a control laboratory. This paper describes a prototype pneumatic active suspension system, which was designed and built over a number of years as a sequence of student projects. The physical plant, which models a quarter-car suspension, consists of a wheel, coil springs, a pneumatic actuator for active damping, position, and velocity sensors, and an alternating current (ac) motor for simulating road disturbance input signal. An electronic subsystem is used to process the sensor signals which are sent to a Motorola 68HC16 microcontroller-based evaluation board. The microcontroller controls a four-bit automatic binary regulator that controls airflow to the pneumatic actuator for damping. A mathematical model of the suspension system was derived analytically and validated experimentally. MATLAB and Simulink (MathWorks, Inc., Natick, MA 01760 USA) were used to analyze and design a digital state feedback plus integral controller for the system. The digital controller was implemented on a Motorola 68HC16 microcontroller. The controller was able to reject a physically generated 0.01143-m negative step road disturbance input. The details of the design construction, modeling, analysis, computer simulation, controller implementation, and experimental results are presented.