Abstract
Keywords - Damping level, Ride comfort, Handling, Semi-active suspension, Control system.
The current paper is devoted to describe a control strategy for semi-active suspension systems. In order to do that, and as a first step, the influence of the suspension damping level on the ride comfort and handling performance of a road vehicle (7 D.O.F model) is analyzed. This sensitivity analysis is then used to find the optimal damping rates for different vehicle velocities and types of road. Moreover, the influence of the rebound or compression damping rate, as well as its optimal value, is also analyzed for each case study.
As previously mentioned, taking in account the former investigation, the design of a low bandwidth semi-active suspension controller is developed. In this case, the reference of the controller is the optimal damping level of the shock absorber according to the vehicle velocity and the type of road. The economy of the system in terms of number of sensors is also analyzed.
From the bill of materials point of view, the implementation of the controller requires four suspension displacement sensors, one accelerometer near the center of gravity of the body, and some already existent sensors (steering wheel angle, braking force, vehicle velocity, etc).
The control strategy is based on fuzzy logic rules in one of its modules. Consequently, the controller is tuneable. On the other hand, the controller includes additional modules: a "road profile estimator" and a "need of handling estimator".
In order to validate the correct behavior of the proposed strategy, a benchmark on the performance of the proposed control versus a Skyhook control and a passive suspension (no control at all) is presented. The results show that the proposed control achieves better behavior than a passive suspension in terms of both, comfort and handling, and comparable results to the "Skyhook" strategy in ride comfort, taking advantage of a less complex damper valve technology.