PURPOSE: To complete the position synchronization of plural suspended equipments without selecting a master equipment by an operator each time the position synchronizing operation is performed by finding speed reference correction quantities of the respective suspended equipments from the mean movement quantity, substantial movement quantities. and deviations of the respective suspended equipments and finding a speed reference correction quantity.

CONSTITUTION: A mean movement quantity arithmetic means 29 calculates the mean movement quantity of the substantial movement quantities of the respective suspended equipments from the outputs of respective substantial movement quantity arithmetic means 15-18. Movement quantity deviation arithmetic means 21-24 calculate the movement quantity deviations of the respective suspended equipments from the outputs of the respective substantial movement quantity arithmetic means 15-18 and the output of the mean movement quantity arithmetic means 29. Speed reference correction quantity arithmetic means 25 28 calculates the speed reference correction quantities of the respective suspended equipments from the outputs of the respective substantial movement quantity arithmetic means 21-24 and adds the correction quantities to the speed references of the respective suspended equipments. Consequently. the position synchronization of the suspended equipments can be completed in a short time and the reliability can be increased.