Active Hydraulically Interconnected Suspension. Modeling and Simulation

Rollover prevention is one of the prominent priorities in vehicle safety and handling control. A promising alternative for roll angle cancellation is the active hydraulically interconnected suspension. This paper represents the analytical model of a closed circuit active hydraulically interconnected suspension system followed by the simulation. Passive hydraulically interconnected suspension systems have been widely discussed and studied up to now. This work specifically focuses on the active hydraulically interconnected suspension system. Equations of motion of the system are formalized first. The system consists of two separate subsystems that can be modeled independently and further combined for simulation. One of the two subsystems is 4 degrees of freedom half-car model which simulates vehicle lateral dynamics and vehicle roll angle response to lateral acceleration in particular. The other subsystem is active hydraulically interconnected suspension system which is responsible for active roll angle reduction. The subsystems are coupled via hydraulics-to-mechanical boundary condition. The methodology used is based on obtaining the equations of motion for the hydraulically interconnected suspension system as well as the half-car model. Standard Lagrange method is used for the half-car model. Hydraulic impedance method and the Kirchhoff's laws for hydraulics are used for the hydraulic circuit. Under a certain simplification, the state-space model of the whole system can be obtained with all states measurable. In simulation part, the system response is examined under a number of typical input tests including NHTSA J-turn maneuver and NHSTA fishhook maneuver. The ability of the active system in roll angle reduction is compared with the conventional car suspension and passive hydraulically interconnected suspension system.