PLC The Level Positioning method of Lattice Boom Offshore Crane by using Hydraulic proportional valve and PLC

摘要

The present invention relates to a position maintaining system and a level positioning method for a lattice boom offshore crane using a hydraulic proportional valve and a PLC, which can guarantee a position of a heavy part despite of simultaneous operation of main motor winches by being applied to a lattice boom type offshore crane for a marine plant. The position maintaining system comprises: a lift device mounted on an offshore crane for lifting goods; a first motor winch part mounted on the lift device; a second motor winch part driving together with the first motor winch part; a first hydraulic motor for operating the first motor winch part; a second hydraulic motor for operating the second motor winch part; a hydraulic oil tank; a hydraulic pump for supplying hydraulic fluid to the first and second hydraulic motors; first and second encoders for sensing the speed and the number of rotation of the first and second motor winch parts; a luffing joystick for controlling operation direction and speed of the second motor winch part; first and second hydraulic proportional valves for controlling pressure, flow rate and direction of the hydraulic fluid; a PLC control unit for controlling operation of the first motor winch part; and an RC control unit having first and second RC control units for controlling operation of the first and second hydraulic proportional valves. The level positioning method comprises the steps of: receiving output values of the first encoder, the second encoder and the luffing joystick, applying the received values to a first operation program, and calculating a first control value for controlling the operation of the first motor winch part; and applying the first control value to a preset second operation program, and calculating a second control value for controlling the first and second hydraulic proportional valves by the second operation program.