H∞ Control Design of a Novel Active Quarter-Car Suspension System

Vehicle suspension systems require good road handling and passenger comfort given typical terrain irregularities. Active suspension control meets these requirements by isolating car body motion from vibrations at the wheels. Active suspension has been a favorite subject in the automotive industry in recent years. One promising approach for active suspension system is based on a passive spring and an actuator connected in parallel. This approach aims to increase driving comfort by actively decreasing the motion of the vehicle's body at low disturbance frequencies and to improve energy efficiency by applying passive suspension components in higher frequencies. This paper examines optimal control solutions for achieving these goals and aims to improve the suspension performance over the existing systems. A new, recently developed actuator is modeled, linearized, and combined with a quarter-car model after which H-infinity (H-infinity) control structures for both cascaded and direct control methods are designed and tested. Controller performance is evaluated by numerous simulations and input data from a real test track. The results are compared to a state-of-the-art controller implemented in an earlier project. The study shows the advantages of the new controllers over the existing one. The suspension performance is improved especially at low frequencies with no increase in energy consumption. Additionally, further increase in control bandwidth can be achieved if road-level measurements are utilized. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.