Special driving drag control system

Electric cranes are important equipment for material transportation in modern factories. Under traditional control methods, most of them adopt manual semi- automatic control
methods. On many occasions, in order to improve work efficiency, promote production automation and reduce labor intensity, it is often necessary to realize automated control of electric vehicles. The realization of automated control enables the vehicle to automatically complete a series of tasks in accordance with the predetermined sequence and control requirements. This example takes the special crane for electroplating in the factory as an example, and uses PLC to form an automatic control system to realize automatic control of the special crane for turtle plating .     (1) Drag system design The forward and backward and lifting movements of the special trolley are driven by a three-phase AC asynchronous motor. According to the lifting weight of the electroplating crane , two J 02-12-4 electric motors are selected for dragging, and a first-level mechanical deceleration is used. The   drag system is shown in Figure 26-35. Among them, the forward and backward, ascent and descent control of the vehicle are realized through the forward and reverse rotation of the electric motor . When the forward and backward and lifting movements of the vehicle are stopped, energy-consuming braking is used to ensure accurate parking. During the translation process, the lifting motor uses electromagnet braking to prevent the hanging basket from sliding down due to its own weight.     In Figure 26-35, contactors KM1＼KM2 control the forward and reverse rotation of the "front/rear" motor to realize the forward and backward movement ; contactors KM3/KM4 control the "raising/lowering" motor to achieve the upward movement of the vehicle. and lowering; contactors KM5 and KM6 control the front and rear brakes of the vehicle , and contactors KM7 and KM8 control the lifting and lowering brakes of the vehicle . FR1 and FR2 are thermal relays for protection. '     (2) PLC selection and address allocation According to the control requirements of this special vehicle, Mitsubishi's Fl-40M PLC is selected. Its basic I/ O points are: 24 input points and 16 output points.     In the electroplating crane PLC control system , the number of I/O points of the PLC varies with the number of electroplating tanks. When there are 4 plating tanks, the PLC needs to have a total of 20 input points and 8 output points; for each additional tank, 2 input points will be added, one of which is used for the slot control travel switch and the other for the slot selection switch. ;The number of PLC output points has nothing to do with the number of plating tanks. If there are a large number of plating tanks, F series expansion units can be used as needed, such as Fl-20E or Fl-40E expansion units. In this example, the number of plating tanks is 4, and there is no need to add expansion units. The u0 address allocation of PLC is shown in the table