Digitally controlled electrorheological valves and their application in vehicle dampers

The idea to replace continuously adjustable proportional valves by a certain number of simple on/off valves is known as digital hydraulics. In recent years, various theoretical and practical works have shown the usefulness of this concept in classical hydraulics. This contribution is concerned with the application of the concept of digital hydraulics to electrorheological (ER) valves used in an ER damper. For this, a detailed mathematical model of ER valves, including the dynamics of the valve due to the inertia of the fluid, is developed. First, an ER damper based on conventional continuously adjustable ER valves is considered and its feasibility is proven by means of measurement results. In a second step, two constructions of digital ER valves are proposed which both are characterized by a very compact and simple design. The features of digital ER valves are analyzed by means of measurement results. Finally, the application of digital ER valves to an ER damper is shown and its properties are compared to the continuously adjustable ER damper in simulation studies on a validated model. It is shown that a similar high performance can be obtained with digital ER dampers at significantly lower overall system costs.