Air Suspension System Model and Optimization 2011-01-0067

An air suspension system can consist of many different components. These components include an air compressor, air springs, pneumatic solenoid valves, height sensors, electronic control unit, air reservoir, air lines, pressure sensor, temperature sensor, etc. The system could be designed as a 2-corner rear air suspension or a 4-corner air suspension.

In this paper, the pneumatic models of air suspension systems are presented. The suspension system models are implemented in AmeSim. The suspension controls are implemented using Matlab/Simulink. The compressor was modeled using the standard AmeSim element with known mass flow rate as a function of pressure ratio. Air lines were modeled using a friction submodel of pneumatic pipe and control (isolation) valves are modeled using 2 position, 2 port pneumatic servo valves. The air spring is modeled as a single pneumatic chamber, single rod jack with spring assistance to account for spring nonlinearities. Vehicle dynamics equations are modeled using the AmeSim control library. Simulated scenarios include raising and lowering the test vehicle at different loading conditions. The test results were correlated in development vehicles equipped with either a 4-corner speed dependent air suspension or a 2- corner rear air suspension.

The air suspension system models can be used as design tools to assist in air suspension performance optimization, air compressor selection, solenoid valve sizing, etc. With these tools, engineers could design an air suspension system virtually. The system performance could be optimized before parts are built to reduce engineering development time and prototype hardware cost.