Using Siemens PLCs in ship component production enables high-precision automation control, enhancing production efficiency and product quality to meet the stringent standards of the shipbuilding industry.

1. Hardware Configuration

Selection of PLC and Expansion Modules

In the automation system for ship component production, we prioritize the Siemens S7-1500 series PLC as the core controller. This PLC features fast processing speed and strong anti-interference capabilities, making it particularly suitable for the high-precision control requirements in ship component manufacturing. Common configurations are as follows:

• CPU 1516F-3 PN/DP: Equipped with fault safety functions to meet the high safety requirements of ship manufacturing.

• SM 531 Digital Input Module: Used for collecting switch signals, such as limit switches and safety doors.

• SM 532 Digital Output Module: Controls motor start/stop, solenoids, indicator lights, etc.

• SM 534 Analog I/O Module: Collects parameters such as temperature, pressure, and displacement, and outputs control signals.

• CM 1542-5 Communication Module: Enables PROFIBUS communication with other control devices.

I/O Point Allocation Table

| Address | Function Description | Signal Type |

|——|———|———|

| I0.0-I0.7 | Safety emergency stop, limit switches | Digital Input |

| I1.0-I1.7 | Working mode selection, start/stop | Digital Input |

| IW64-IW72 | Servo motor position feedback | Analog Input |

| IW80-IW88 | Pressure, temperature sensors | Analog Input |

| Q0.0-Q0.7 | Main motor control, solenoids | Digital Output |

| Q1.0-Q1.7 | Indicator lights, alarms | Digital Output |

| QW64-QW72 | Servo motor control signals | Analog Output |

Key Wiring Points for the System

To ensure reliable operation in the ship component production environment, special attention must be paid to the following wiring points:

1. Strict separation of strong and weak currents within the control cabinet, using shielded cables for signal lines with good grounding.

2. Analog signals should use differential transmission methods to reduce electromagnetic interference in the workshop environment.

3. All safety circuits should adopt a dual-redundancy design and be pulled up to a 24V power supply.

4. Use metal waterproof connectors to ensure reliable connections in humid environments.

2. Control Program Design

Program Architecture Design

The control program for ship component production adopts a modular design approach, with a clear hierarchical structure that facilitates maintenance and secondary development:

• OB1: Main program loop, calling various function blocks.

• OB40: Hardware interrupt, handling emergency events.

• OB100: Startup organization block, system initialization.

• FB10-FB20: Function blocks for various processes.

• FB30-FB40: Communication processing function blocks.

• DB10-DB50: Process parameters and operational data blocks.

Function Block Design

Below is an example of the welding control function block for ship components:

FUNCTION_BLOCK "Welding Control FB"  // FB20

TITLE = 'Ship Component Welding Control'

{ S7_Optimized_Access := 'TRUE' }

AUTHOR : PLC Expert

VERSION : 1.0

   
VAR_INPUT

    Start_Command : Bool;  // Welding start signal

    Stop_Command : Bool;  // Welding stop signal

    Welding_Current_Set : Real;  // Unit: A

    Welding_Speed_Set : Real;  // Unit: mm/s

END_VAR


VAR_OUTPUT

    Welding_Status : Bool;  // TRUE=Welding in progress

    Welding_Complete : Bool;  // Single welding completion signal

    Fault_Status : Bool;  // Welding exception flag

END_VAR


VAR

    Welding_Timer : TON;  // Welding time control

    Cooling_Timer : TON;  // Cooling time control

    State_Machine : Int := 0;  // Welding state control

    // 0=Standby, 1=Preheat, 2=Welding in progress, 3=Cooling, 4=Complete, 5=Fault
    Actual_Welding_Current : Real;  // Actual measured current

    Temperature_Monitor_Value : Real;  // Welding area temperature

END_VAR


VAR_TEMP

    Temperature_Exceed : Bool;  // Temporary variable - temperature exceed flag

END_VAR


BEGIN

    // State machine control logic

    CASE #State_Machine OF

        0:  // Standby state

            #Welding_Status := FALSE;

            #Welding_Complete := FALSE;
            
            IF #Start_Command AND NOT #Stop_Command THEN

                #State_Machine := 1;  // Transition to preheat state

            END_IF;
            
        1:  // Preheat state

            // Preheat logic, current slowly rises

            #Welding_Status := TRUE;

            // Preheat timer for 5 seconds before entering welding state

            #Welding_Timer(IN := TRUE, PT := T#5S);

            IF #Welding_Timer.Q THEN

                #Welding_Timer(IN := FALSE);

                #State_Machine := 2;

            END_IF;
            
        2:  // Welding in progress

            // Welding current and speed control output

            "Welding_Power_DB".Current_Output := #Welding_Current_Set;

            "Welding_Mechanical_DB".Speed_Output := #Welding_Speed_Set;
            
            // Welding process monitoring

            #Temperature_Exceed := #Temperature_Monitor_Value > "Process_Parameters_DB".Max_Temperature_Limit;

            IF #Temperature_Exceed OR (#Actual_Welding_Current < #Welding_Current_Set * 0.8) THEN

                #State_Machine := 5;  // Abnormal situation transitions to fault state

            END_IF;
            
            // Determine welding time based on workpiece type

            IF "Workpiece_Info_DB".Workpiece_Type = 1 THEN  // Small component

               #Welding_Timer(IN := TRUE, PT := T#30S);

            ELSIF "Workpiece_Info_DB".Workpiece_Type = 2 THEN  // Medium component

               #Welding_Timer(IN := TRUE, PT := T#60S);

            ELSE  // Large component

               #Welding_Timer(IN := TRUE, PT := T#120S);

            END_IF;
            
            // After welding time is up, transition to cooling phase

            IF #Welding_Timer.Q THEN

                #Welding_Timer(IN := FALSE);

                #State_Machine := 3;

            END_IF;
            
            // Check stop command

            IF #Stop_Command THEN

                #State_Machine := 5;  // Transition to fault state on emergency stop

            END_IF;
            
        3:  // Cooling phase

            "Welding_Power_DB".Current_Output := 0.0;  // Turn off welding power

            #Cooling_Timer(IN := TRUE, PT := T#45S);
            
            IF #Cooling_Timer.Q THEN

                #Cooling_Timer(IN := FALSE);

                #State_Machine := 4;  // Transition to complete state after cooling

            END_IF;
            
        4:  // Complete state

            #Welding_Status := FALSE;

            #Welding_Complete := TRUE;

            // Record welding data to database

            "Data_Recording_DB".Last_Welding_Time := "System_Clock_DB".Current_Time;

            "Data_Recording_DB".Welding_Count := "Data_Recording_DB".Welding_Count + 1;

            #State_Machine := 0;  // Return to standby state
            
        5:  // Fault state

            #Welding_Status := FALSE;

            #Fault_Status := TRUE;

            "Welding_Power_DB".Current_Output := 0.0;  // Turn off welding power

            "Welding_Mechanical_DB".Speed_Output := 0.0;  // Stop mechanical movement
            
            // Fault requires manual reset

            IF "HMI".Fault_Reset_Button THEN

                #Fault_Status := FALSE;

                #State_Machine := 0;  // Reset and return to standby state

            END_IF;

    END_CASE;

END_FUNCTION_BLOCK

State Control Design

The ship component production control system implements process control using a state machine approach, with the main states including:

1. Standby State: The system is initialized and waiting for operational commands.

2. Production Preparation: Check if the workpiece is in place and confirm parameters.

3. Production in Progress: Execute cutting, welding, and other processes.

4. Pause State: Production is temporarily interrupted, maintaining the current position.

5. Completion State: Production of a single workpiece is complete, preparing for the next.

6. Fault State: An anomaly is detected, requiring manual intervention.

State transitions are triggered by operational commands, sensor signals, and internal timers, executing corresponding actions and outputting status light signals in each state.

3. Fault Diagnosis and Troubleshooting

Common Fault Analysis

Common faults and handling methods during ship component production:

| Fault Phenomenon | Possible Cause | Diagnosis Method | Solution |

|———|———|———|———|

| PLC running light flashing | Program cycle timeout | Check program cycle time | Optimize program, reduce calculation load within the cycle |

| Servo motor not rotating | Servo alarm or parameter error | Read servo drive error code | Clear alarm and correct parameters based on error code |

| Communication interruption | Loose or interfered network connection | Check communication status byte | Check network connection, add filtering devices |

| Process parameters abnormal | Sensor failure or calibration deviation | Compare data from multiple sensors | Recalibrate or replace sensors |

| Safety circuit triggered | Safety door opened or emergency stop pressed | Check safety module status | Inspect safety devices, reset and restart |

Using Diagnostic Tools

For complex faults, the diagnostic tools provided by Siemens engineering software STEP 7 can be used:

1. Online Monitoring: Use VAT tables to observe the process of key variable changes.

2. Program Status: Highlight the program execution path line by line.

3. Tracking Function: Record the trend of variable changes over time.

4. System Diagnosis: View the system diagnostic buffer for the CPU and modules.

Case Analysis

Case: Intermittent shutdown of the ship hull plate bending control system.

Problem Description: The bending mechanism triggers a protective shutdown intermittently under high load, but hardware checks show no abnormalities.

Analysis Process:

1. Using program status tracking, it was found that load current spikes triggered the protection.

2. Tracking function recorded that current spikes occurred at direction change points.

3. Comparing the program revealed that the acceleration and deceleration time parameters were set too short.

Solution:

1. Extended the servo drive acceleration and deceleration time from 50ms to 200ms.

2. Added a 10ms delay at direction change points.

3. Optimized PID parameters to eliminate overshoot.

4. Added current rise rate limit function.

After modifications, the system ran continuously for 200 hours without issues, and the fault was completely resolved.

4. System Maintenance and Management

Key Points for Daily Maintenance

Maintenance plan for the PLC system in ship component production:

• Daily Check: Power voltage, operational status indicators, safety devices.

• Weekly Check: Temperature inside the control cabinet, ventilation filters, backup battery voltage.

• Monthly Check: I/O terminal connections, communication network quality, program change records.

• Quarterly Check: Complete system backup, cleaning of electrical contacts, sensor calibration.

System Upgrade Methods

Steps for upgrading the production control system:

1. Upgrade Preparation:

• Create a complete system backup (program, parameters, configuration).

• Develop a detailed upgrade plan and rollback strategy.

• Test upgrade content in a simulated environment.

Execute Upgrade:

• Choose planned downtime to execute.

• Upgrade slave devices first, then the master station.

• Upgrade by module and test each one.

Upgrade Verification:

• Perform no-load startup tests.

• Conduct functional tests and performance verification.

• Record verification results and archive them.

Backup and Recovery Strategy

Regular backup strategy for the ship production line:

• Weekly complete program automatic backup to the engineering server.

• Immediately perform differential backup after parameter modifications.

• Quarterly create a complete image backup stored on offline devices.

• Establish a version management system to record each change and responsible person.

5. Human-Machine Interface Design

Interface Layout Description

The HMI system for ship component production adopts a multi-level menu structure:

• Main Interface: Overall equipment status, production count, alarm information.

• Process Parameters: Parameter settings for each process and display of process curves.

• Manual Control: Unit debugging and manual control functions.

• System Settings: Permission management, communication configuration, system time.

• Alarm Records: Historical alarm queries and statistical analysis.

The interface design follows ergonomic principles, with key operation button sizes no less than 30×30mm, and dangerous operations requiring secondary confirmation.

Parameter Setting Description

Example of the welding parameter setting interface:

• Parameters classified by welding process type (TIG welding, CO₂ welding, submerged arc welding).

• Use dropdown boxes to limit parameter selection range to avoid input errors.

• Key process parameter settings are password protected and managed by permissions.

• Parameter modifications automatically record the operator and modification time.

• Provide parameter template import and export functions for easy process replication.

Conclusion

The application of Siemens PLCs in ship component production, through reasonable hardware selection, structured program design, and comprehensive maintenance management, can effectively enhance production efficiency. We welcome you to share your application experiences!