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Abstract: The four-way proportional directional control valve has been widely used as the main stage spring constant for the two-stage proportional control valve (PDV). Since a tradeoff should be made between manufacturing costs and static performance, two symmetry dead zones are introduced in the main stage spring constant: the center dead zone caused by the center floating position and the intermediate dead zone caused by the intermediate position. Though the intermediate dead-zone is much smaller than the center dead zone, it has significant effect on the dynamic position tracking performance. In this paper, the cascade dead zones problem in a typical two-stage PDV is analyzed and a cascade dead zones model is proposed for the main stage spring constant. Then, a cascade dead zones inverse method is improved with gain estimation and dead zone detection to compensate the dead zone non-linearity. Finally, a digital controller is designed for verification. The comparative experimental results indicate that it is effective to reduce the large position tracking error when the proposed method is applied.

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