3、大学本科毕业设计(论文)基于PLC控制桥式起重机变频系统的设计Frequency of Bridge Crane Based on PLC ControlSystem DesignAbstract:Thebridgecranecarriesakindoftypicalequipmentinthesuppliessystem,soithaveextensivefunctionintheactivityofProducingenterprise,soitimportantimprovethebridgecraneoper