This article describes how on/off valves can be used in the closed loop control. After studying different industrial hydraulic applications typical requirements will be compiled. From these requirements a basic on/off valve architecture will be derived. In this article the number of parallel connected on/off valves per control edge is limited to one valve. So the typical digital hydraulics with a high number of parallel connected valves is not considered. The on/off valves could not be controlled like normal directional valves. To control on/off valves digital control methods are common to use. The digital control methods are not optimized for the hydraulic on/off valves, because the origins of the digital control methods will be found in the electrical engineering. The novel idea for the digital control methods is the optimized pulse control which eliminates the disadvantages of the common digital control methods. How the optimized pulse control works is described in this article.
In this paper a novel and validated model to describe the dynamics of switching valves is presented and used to analyse the behaviour of switching valves. The paper starts with a brief discussion of the state of the art and the characteristics of switching valves, continuing with investigations of their dynamics, the development of the novel model and an analysis of the characteristics of switching valves based on the introduced model. The different operation modes which appear when fast switching control signals are applied are introduced and discussed. Additionally the application of the proposed model in closed loop simulations is pointed out and compared to state of the art models. It is demonstrated that the novel model offers a good trade-off between model accuracy and model complexity.
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