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Do-More PLC, Modbus RTU with V90 servos and INVT inverter

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  • Jarrett
    Quick update for those that are curious:

    The V90 Servo's are working and communicating via Modbus RTU. A few takeaways with the servo drives:
    1. V-Assistant: use control words and verify the parameters are for modbus. Not all firmware supports RTU and must be checked.

    2. The order of reading and writing information to the drives is crucial for operation. This is primarily for the Control word PZD1 and intermittent reading of the status word to trigger sequenced commands. This is the case for referencing the axis in IPos mode (Internal Positioning). FYI using IPos/S-Mode, Internal Positioning/Jogging

    3. Do-More Serio-4: Modbus buffer has limitations and if the read/write commands are exceeded the network fails. With 4 devices on the Modbus Network the reading and writing between the drives must be linked to avoid filling the buffer (not fully understood as to how it's managed and would like to know). To limit the transmissions the write instructions occur only upon variable changes, and a heartbeat read of the status word(s). Regardless of timeout settings with the drives RTU window a heartbeat read is required to maintain communication.

    4. On the application side. I would not recommend Modbus RTU for coordinated motion. This project does not require it thankfully. With the V90 servo's, in S-mode jogging for example, if a run command CW is given and communication is lost the drive continues acting on the last successful word written.

    5. PLC:
    Baud: 19200
    Data Bits: 8
    Stop Bits: 1
    Parity: Even
    TC: Unconditional
    RTS: Follow Transmitter
    Timeout: 20ms (may test reducing further)
    Retries: 2
    Inter-Packet-Delay: 4000us (may try reducing further)
    6. PC HMI: Excel VBA, Modbus TCP
    Using Excel VBA for the DIY HMI is not exactly recommended. You can do it successfully; however, there exist limitations with memory and data operators with converting between data types. Double integer data, two's compliment, and binary operations in VBA is not friendly.
    60 registers continually read
    30 registers to communicate job settings
    300 data point registers per job write.
    Thanks for the help


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  • Garry
    Here is a link on the Siemens site to help with the Modbus Addressing on the V90. Check the information on the default setting required to control this from the PLC.
    I would then try a read instruction from the PLC, to test communication and ensure that you have the correct addressing.

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  • Do-More PLC, Modbus RTU with V90 servos and INVT inverter

    I'm working on a project and replaced a siemens plc with an H2 Do-More PLC and a SERIO-4. It's a gantry style drilling machine with 3 servo axis utilizing Simatic V90 servos and an INVT G100 VFD.

    PC: Windows 10, Modbus TCP to Do-More (credit to Garry, ACC Automation)
    PLC: H2-DM1E
    Com Card: H2-SERIO-4, using port C Modbus RTU
    Servos: Sematic V90 series, 6SL3210-5FE11-5UA0, firmware updated to v11101
    VFD: INVT, GD100-5RSG-4
    Protocol: Modbus RTU
    Baud Rate: 38400
    Parity Check: 2 Even
    UI: Servos #1-#3, G100 #4

    I'm having a problem reading and writing to the drives, all set to even parity checks, baud rate of 38400, UI set according to the order, and tested with and without terminating resistors.

    Serio-4 C: RTU Master
    Timeout: 1000ms
    Retries: 2
    Inter-Packet Delay: 3500us (might need to change)
    Baud Rate: 38400
    Data Bits: 8
    Stop Bits: 1
    Parity: Even
    Transmit Control: Unconditional
    RTS: Follow Transmitter

    V90 Servos:
    1) RS485 monitoring time, default is 0ms and curious as to what the proper method is to set it given 4 slave items.
    2) Modbus addressing: Assuming the ex 40100 addresses are dec and not hex. Offset address 100 for instance for the MWX MRX?

    G100 VFD:
    1) Addressing documentation is ex 2001 hex, converting to dec is 8193, so the MWX and MRX offset addresses are?

    Any feedback or advice on how to go through and check the parameters and make adjustments would be greatly appreciated.