Mitsubishi Sequential Function Charts (SFC) for Material Handling

Implementing Material Handling with Sequential Function Charts (SFC)

Material Handling systems in Logistics & Warehousing require careful consideration of intermediate to advanced control requirements, real-time responsiveness, and robust error handling. This walkthrough demonstrates practical implementation using Mitsubishi GX Works2/GX Works3 and Sequential Function Charts (SFC) programming.

System Requirements:

A typical Material Handling implementation includes:

Input Devices (5 types):
1. Laser scanners: Critical for monitoring system state
2. RFID readers: Critical for monitoring system state
3. Barcode scanners: Critical for monitoring system state
4. Load cells: Critical for monitoring system state
5. Position sensors: Critical for monitoring system state

Output Devices (5 types):
1. AGV motors: Controls the physical process
2. Conveyor systems: Controls the physical process
3. Lift mechanisms: Controls the physical process
4. Sorting mechanisms: Controls the physical process
5. Robotic arms: Controls the physical process

Control Logic Requirements:

1. Primary Control: Automated material movement using PLCs for warehouse automation, AGVs, and logistics systems.
2. Safety Interlocks: Preventing Route optimization
3. Error Recovery: Handling Traffic management
4. Performance: Meeting intermediate to advanced timing requirements
5. Advanced Features: Managing Load balancing

Implementation Steps:

Step 1: Program Structure Setup

In GX Works2/GX Works3, organize your Sequential Function Charts (SFC) program with clear separation of concerns:

• Input Processing: Scale and filter 5 sensor signals


• Main Control Logic: Implement Material Handling control strategy


• Output Control: Safe actuation of 5 outputs


• Error Handling: Robust fault detection and recovery

Step 2: Input Signal Conditioning

Laser scanners requires proper scaling and filtering. Sequential Function Charts (SFC) handles this through perfect for sequential processes. Key considerations include:

• Signal range validation


• Noise filtering


• Fault detection (sensor open/short)


• Engineering unit conversion

Step 3: Main Control Implementation

The core Material Handling control logic addresses:

• Sequencing: Managing warehouse automation


• Timing: Using timers for 4-12 weeks operation cycles


• Coordination: Synchronizing 5 actuators


• Interlocks: Preventing Route optimization

Step 4: Output Control and Safety

Safe actuator control in Sequential Function Charts (SFC) requires:

• Pre-condition Verification: Checking all safety interlocks before activation


• Gradual Transitions: Ramping AGV motors to prevent shock loads


• Failure Detection: Monitoring actuator feedback for failures


• Emergency Shutdown: Rapid safe-state transitions

Step 5: Error Handling and Diagnostics

Robust Material Handling systems include:

• Fault Detection: Identifying Traffic management early


• Alarm Generation: Alerting operators to intermediate to advanced conditions


• Graceful Degradation: Maintaining partial functionality during faults


• Diagnostic Logging: Recording events for troubleshooting

Warehouse automation implementations face practical challenges:

1. Route optimization
Solution: Sequential Function Charts (SFC) addresses this through Perfect for sequential processes. In GX Works2/GX Works3, implement using Ladder Logic features combined with proper program organization.

2. Traffic management
Solution: Sequential Function Charts (SFC) addresses this through Clear visualization of process flow. In GX Works2/GX Works3, implement using Ladder Logic features combined with proper program organization.

3. Load balancing
Solution: Sequential Function Charts (SFC) addresses this through Easy to understand process steps. In GX Works2/GX Works3, implement using Ladder Logic features combined with proper program organization.

4. Battery management
Solution: Sequential Function Charts (SFC) addresses this through Good for batch operations. In GX Works2/GX Works3, implement using Ladder Logic features combined with proper program organization.

Performance Optimization:

For intermediate to advanced Material Handling applications:

• Scan Time: Optimize for 5 inputs and 5 outputs


• Memory Usage: Efficient data structures for FX5 capabilities


• Response Time: Meeting Logistics & Warehousing requirements for Material Handling