Application of Wireless Communication Technology of the Cranes Linkage Control(2)
2.1 To configure the hardware of PLC control system
To configure the hardware by use of Siemens STEP7 programming software, it is needed to enable STEP7 programming software, to insert the 300PLC track, the power source, CPU, the Ethernet module, in-out module, Siemens frequency converter S120 hardware, Siemens frequency converter G120 hardware, P+F encoder hardware, and then save and compile the hardware.
Under this item, it is needed to insert separately the PLC of the other 3 cranes to save and compile the PLC of each crane. Under the network configuration, 4 PLC compose ISO-on-TCP and then link the network, save and compile. In this way, the hardware configuration is finished.
2.2 The communication control program which program for this crane.
The communication control program does reading and writing to frequency converter by use of SFC14 and SFC15 function module of Siemens programming software. It configures the software of S120 frequency converter by means of STARTER software, and the standard communication message organization is needed. It gives the order of start, stop and speed by using the control word and status word of S120 frequency converter while it is monitoring the status word and giving protection. It gives the order of start, stop and speed by using the control word and status word of YASKAWA frequency converter while it is monitoring the status word and giving protection.
2.3 To compile the communication control program among the 4 PLC.
The FC5 and FC6 function module are invoked from STEP7 programming software and used to program the data which is sent and received between the PLC of the 4 cranes. It sends the data from one crane to the other 3 cranes and while receiving data from the other 3 cranes. The data contains order of control, speed and traveling distance of each mechanism and etc.
2.4 To compile the synchronous control procedure of each mechanism of the 4 cranes. We calculate the traveling distance of each mechanism by use of the encoder. Based on the traveling distance of each mechanism of one crane, we compare the traveling distances and base distances of the other 3 cranes. If the distance is bigger than the base distances, it means that the traveling speed of the mechanism of this crane is high. We should make it slow down and have the speed of frequency converter lower. Otherwise, we have it higher to ensure the synchronization of each mechanism of several cranes.
2.5 To compile the gang control program
In accordance to the data that is transferred between each PLC, we have the points of gang control switch and single-action control switch compiled in control program. Once the point of gang control switch is close, all cranes are in coordinate state. Once the point of single-action switch is close, all crane keep running separately, out of control of any cranes. Active control switch and slaved control switch work when the gang control switch is close. They complies the point of active control switch and slaved control switch into control program. If the point of active control switch is close, this crane will be active crane which is capable of controlling the slaved cranes. If the slaved control switch is close, this crane will be slaved crane, which is supposed to be controlled by active crane, and the command from slaved crane will not take effect. Under ganged state, to operate the single-action switch of the other 3 cranes can control the random crane and have it work alone.
2.6 Programming on communication interruption procedure.
CPU has its own Cycle/Memory cycle in its property. Each byte of Memory Cycle has different scanning periods. It’s allowed that to do timing program on communication in accordance with scanning period. Once the wireless communication is cut off, the scanning period of the clock of CPU would be interrupted. That leads to the breakover of the timer and ensures the running of interruption procedure.