The post Compensation for Cascade Dead Zones in Proportional Control Valves first appeared on the ISA Interchange blog site.
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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Source: ISA News