Abstract: This article introduces the communication application of PROFIBUS bus with devices such as frequency converters, ET200S, encoders, and displacement sensors in large straight seam milling machines, as well as the issues that should be noted.
0 Introduction
The large straight seam milling machine manufactured and developed by our company is one of the key pieces of equipment on the large-diameter straight seam welded pipe production line (JCOE) in the oil and gas pipeline manufacturing industry. This equipment is the first of its kind independently developed in China. The electrical control system adopts two Siemens PROFIBUS buses for communication, consisting of 28 master and slave communication stations, to achieve real-time monitoring and communication of global digital quantities. In the system configuration, a Siemens CPU414-3DP is selected as the master station, and ET200S remote I/O, 70 frequency converter, TR encoder, MTS displacement sensor, proportional servo valve, and Balluff micropulse displacement sensor are used as slave stations (see Figure 1 for the large straight seam milling machine PLC configuration). A Siemens MP377 touch screen is used for setting and displaying. All speed, displacement, safety protection, and fault points in the system must be monitored and alarmed in real time on the screen. Due to the large number of communication ports, long distances, and numerous program modules (see Figure 2 for the large straight seam milling machine PLC program block), the high degree of automation is required, making control very difficult.
PROFIBUS-DP communication of 1.70 frequency converter
1.1 The communication mode is set to PPO 4, which is 0 PKW/6 PZD. Both input and output are 6 PZD. With P60=7 set, P53=3 is set to enable CBP2 (PROFIBUS) operation. P918.1 sets the inverter's PROFIBUS address.
1.2 Set the first and second input PZD as the control words from the PLC to the frequency converter, set the first and second output PZD as the status words from the frequency converter to the PLC, set the third as the percentage value of the actual output frequency fed back by the frequency converter to the PLC, and set the fourth as the percentage value of the actual output current fed back by the frequency converter to the PLC.
1.3 The first PZD of the PLC to the frequency converter is stored in the K3001 word in the frequency converter. Here it is set to P554=3100, P571=3101, P572=3102. When bit 3100 of K3001 controls the start and stop of the frequency converter, 3101 controls the forward rotation, and 3102 controls the reverse rotation.
1.4 The second PZD from the PLC to the frequency converter is stored in word K3002 in the frequency converter. If P443=K3002, then the entire word K3002 is the main setpoint control word from the PLC to the frequency converter. The size of the second word sent by the PLC is 0 to 16384 (corresponding to 0 to 100% of the frequency converter output). When it is 8192, the frequency converter output frequency is 25Hz.
1.5 Program: (Create DB17, call SFC14, SFC15, the inverter address is 512, i.e., W#16#200)
1.5.1 Reading Data
CALL "DPRD_DAT"
LADDR :=W#16#200
RET_VAL:=MW200
RECORD := P#DB17.DBX0.0 BYTE 12 (Reads 12 BYTEs)
NOP 0
1.5.2 Sending Data
CALL "DPWR_DAT"
LADDR :=W#16#200
RECORD := P#DB17.DBX12.0 BYTE 12 (Writes 12 BYTEs)
RET_VAL:=MW210
NOP 0
1.5.3 L "DB17".DBW0
T "MW20"
NOP 0
1.5.4 L "DB17".DBW2
T "MW22"
NOP 0
Then: DB17.DBX 13.0 controls startup and shutdown;
DB17.DBX 13.1 controls forward rotation;
DB17.DBX 13.2 Inversion of Control;
M21.1 Inverter READY;
M21.3 frequency converter FAULT.
2. Encoder PROFIBUS-DP Communication
2.1 Read encoder values.
LP##Peripherieaddr
TAK
LAR1
L PID [AR1,P#0.0]
T #actual_C1_DI
2.2 Data correction, adding a correction value (offset, usually a negative value).
L #actual_C1_DI
L #offset
+D
T #actual_C2_DI
NOP 0
2.3 Convert and convert to actual position, data type conversion, multiply by conversion factor to obtain actual position.
A(
L #actual_C2_DI
DTR
T #actual_Pos_R
SET
SAVE
CLR
A BR
)
JNB _006
L #actual_Pos_R
L #multipliactor
*R
T #actual_position
_006: NOP 0
3. PROFIBUS-DP Communication of Displacement Sensor
3.1 Encoder data acquisition 1, PID257(L)/PID258(M), MB103(L)/MB102(M).
A(
L PIB 257
T MB 103
SET
SAVE
CLR
A BR
)
JNB _001
L PIB 258
T MB 102
_001: NOP 0
3.2 Encoder data acquisition 2, 0 / PID259(H), MB100(HH) / MB101(H).
A(
L PIB 259
T MB 101
SET
SAVE
CLR
A BR
)
JNB _002
L 0
T MB 100
_002: NOP 0
3.3 Read the status bit parameters and send the status bits to MB80.
L PIB 256
T MB 80
NOP 0
3.4 Correction results: MD100 is the encoder sampling data, MD104 is the encoder zero-position correction value, and MD108 is the corrected result, which is used in control; MD104 is set on the HMI (Human Machine Interface).
L MD 100
L MD 104
+R
T MD 108
NOP 0
4. When the ET200S is used as a remote I/O substation, its PROFIBUS-DP communication is relatively simple. You only need to set the PROFIBUS-DP address on the interface module, which will not be described in detail here.
5. Issues to be aware of regarding PROFIBUS-DP communication
5.1 The connection between the bus connector and the bus cable must be reliable, the shielding layer must be pressed correctly and firmly, loose wires must be bundled together, and they must not come into contact with the chips on the bus connector.
5.2 The DC24V GND on all master and slave stations must be connected.
5.3 Bus cables should be kept as far away from power cables as possible to prevent electromagnetic interference.
5.4 Shielded cables should be used as much as possible for the wiring between the 132KW motor and the frequency converter. The shielding layer should be crimped inside the electrical box, and the motor side should be suspended.
5.5 The PE line should be reliably connected to all equipment using the thickest possible grounding wire.
5.6 The grounding copper busbar inside the electrical box must be reliably connected to the grounding copper busbar inside the factory building.
6. Conclusion
Because this control system uses several non-Siemens bus products, although they all support the PROFIBUS protocol, there are still many differences in the internal communication software. We needed to understand, digest, and experiment repeatedly. After two years of extensive work, the equipment has now been debugged and delivered to the user, and the results are good.
References :
[1] A comprehensive guide to using the 6SE70 frequency inverter.
[2] CBP2 Communication Board User Manual
[3] Operation instructions for Balluff BTLT type displacement sensor.
[4] MTS RH type displacement sensor user manual.
