Research on Air Suspension System Based on Genetic LQG and PID Control
An active air suspension system for vehicles using the Linear Quadratic Regulator vibration controller and Proportional Integral Derivative control strategy is presented. A quarter car with two degrees of freedom air suspension vibration model is described. Compared with the conventional passive suspension system, the analysis is done to the system control performance. The road profile is simulated according to ISO8608. The analysis of the system response is obtained through a lot of simulation work. The simulation results indicate that the vibration of the vehicle can be reduced and the ride comfort is improved by the two proposed suspension system. Introduction A suspension system is one of the most important components in a vehicle. It has two main functionalities. One is increasing driving comfort, by isolating the vehicle body from external disturbances, which mainly come from irregular road surfaces. The other one is to maintain a firm contact between road and tires to provide guidance along the track. This is called handling performance. In a conventional suspension system, which is composed of passive springs and dampers, a trade-off is required to resolve the conflicting requirements of ride comfort and good handling performance. The reason is that a hard suspension is required for handling and to support the mass of the vehicle, on the other hand, a soft suspension is needed to isolate the disturbances from the road. A semi-active system is able to alter some of its characteristics, e.g. the amount of damping. The active system is able to change the amount of dissipative power, but it can also supply power to the system, hence it can work in the four quadrants of the force-velocity diagram. This allows for significantly improving the performance of the suspension system with an active suspension. Many research work has been done to the control of the suspension system. An experimental verification on a quarter car setup of a robust controller in combination with a hydraulic actuator is conducted [1]. The robust controller was designed to reduce the body vibrations at 1.5 Hz without amplifying the body acceleration and tire force at other frequencies. To describe comfort, only the body acceleration between 1 and 5 Hz is taken into account. This resulted in a reduction of 50%. An H∞ robust controller was tested on a test vehicle with a semi-active suspension [2]. The Cowey Motor Works of Great Britain introduced air suspension that Lincoln ballyhooed for some models introduced in 1984 in 1909. It did not work well because it leaked. The first practical air suspension was developed by Firestone in 1933 for an experimental vehicle termed the Stout-Scarab. This was a rear-engine vehicle that used four rubberized bellows in place of conventional springs. Small M-P compressors attached to each bellow supplied air. As people might imagine, the air bag suspension was an expensive setup—still is, in fact. Air suspensions are designed to cushion the ride and keep the car, bus or truck level fore and aft and at a constant height regardless of load. Air suspension was introduced on many luxury vehicles in the late 1950s, but it was dropped after one or two model years. Recently, however, new leveling systems have been researched and developed for passenger automotive vehicle use, including air-adjustable rear shock absorber. A typical air