Abstract:For the issues that the openloop control system of the column cylinder of the original screw pile hammers had unstable performance,the manual operation was poor realtime and the synchronization error of the cylinder was large, the synchronous closedloop control system based on PLC was designed and used in the new type of screw pile hammers.The hardware of the closedloop control system consisted of a column cylinder, a magnetostrictive displacement sensor, and a S7200 programmable controller from SIEMENS.The field experimental results show that the designed closedloop control system of the column cylinder can be used to achieve the digital control of the column, and automatical correction in lifting and falling process. The synchronous control precision is ±2 mm, the control system is stable, safe and convenient, and has practical engineering value.