Mitsubishi GX Works2/GX Works3 for Pump Control
GX Works3 represents Mitsubishi's latest engineering software supporting the MELSEC iQ-R and iQ-F series controllers, while GX Works2 remains in use for legacy Q, L, and FX5 series PLCs. The programming environment features a project-based structure organizing programs into multiple POUs (Program Organization Units) including main programs, function blocks, and structured projects. Unlike Western PLC manufacturers, Mitsubishi supports both device-addressed programming (X0, Y0, M0, D0) and label-...
Platform Strengths for Pump Control:
- Excellent price-to-performance ratio
- Fast processing speeds
- Compact form factors
- Strong support in Asia-Pacific
Unique ${brand.software} Features:
- Simple Motion module integration with motion SFC (Sequential Function Chart) programming eliminating complex positioning code
- RD.DPR instruction providing direct device programming without software transfer for recipe adjustments
- Melsoft Navigator project management integrating multiple controllers, HMIs, and network devices in unified environment
- Multiple CPU configuration allowing up to 4 CPUs in single rack sharing memory via high-speed backplane
Key Capabilities:
The GX Works2/GX Works3 environment excels at Pump Control applications through its excellent price-to-performance ratio. This is particularly valuable when working with the 5 sensor types typically found in Pump Control systems, including Pressure transmitters, Flow meters, Level sensors.
Control Equipment for Pump Control:
- Centrifugal pumps for high flow applications
- Positive displacement pumps for metering
- Submersible pumps for wet well applications
- Booster pump systems for pressure maintenance
Mitsubishi's controller families for Pump Control include:
- FX5: Suitable for intermediate Pump Control applications
- iQ-R: Suitable for intermediate Pump Control applications
- iQ-F: Suitable for intermediate Pump Control applications
- Q Series: Suitable for intermediate Pump Control applications
Hardware Selection Guidance:
Mitsubishi offers several controller families addressing different performance and application requirements. The MELSEC iQ-R series represents the flagship product line with processing speeds as fast as 0.98ns per basic instruction supporting applications from small machines to complex automated systems. R04CPU provides 40K steps program capacity and 256K words data memory suitable for compact mac...
Industry Recognition:
High - Popular in electronics manufacturing, packaging, and assembly. Mitsubishi PLCs serve Japanese and Asian automotive manufacturers with MELSEC iQ-R controllers managing assembly line transfers, welding automation, and quality inspection systems. Body assembly lines use multiple CPU configurations (up to 4 CPUs in single rack) distributing control: CPU1 handles co...
Investment Considerations:
With $$ pricing, Mitsubishi positions itself in the mid-range segment. For Pump Control projects requiring intermediate skill levels and 2-4 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.
Understanding Structured Text for Pump Control
Structured Text (ST) is a high-level, text-based programming language defined in IEC 61131-3. It resembles Pascal and provides powerful constructs for complex algorithms, calculations, and data manipulation.
Execution Model:
Code executes sequentially from top to bottom within each program unit. Variables maintain state between scan cycles unless explicitly reset.
Core Advantages for Pump Control:
- Powerful for complex logic: Critical for Pump Control when handling intermediate control logic
- Excellent code reusability: Critical for Pump Control when handling intermediate control logic
- Compact code representation: Critical for Pump Control when handling intermediate control logic
- Good for algorithms and calculations: Critical for Pump Control when handling intermediate control logic
- Familiar to software developers: Critical for Pump Control when handling intermediate control logic
Why Structured Text Fits Pump Control:
Pump Control systems in Water & Wastewater typically involve:
- Sensors: Pressure transmitters for discharge and suction pressure, Flow meters (magnetic, ultrasonic, or vortex), Level transmitters for tank or wet well level
- Actuators: Variable frequency drives (VFDs) for speed control, Motor starters (DOL or soft start), Control valves for flow regulation
- Complexity: Intermediate with challenges including Preventing cavitation at low suction pressure
Control Strategies for Pump Control:
- constant: Maintain fixed speed or output
- pressure: PID control to maintain discharge pressure setpoint
- flow: PID control to maintain flow rate setpoint
Programming Fundamentals in Structured Text:
Variables:
- declaration: VAR / VAR_INPUT / VAR_OUTPUT / VAR_IN_OUT / VAR_GLOBAL sections
- initialization: Variables can be initialized at declaration: Counter : INT := 0;
- constants: VAR CONSTANT section for read-only values
Operators:
- arithmetic: + - * / MOD (modulo)
- comparison: = <> < > <= >=
- logical: AND OR XOR NOT
ControlStructures:
- if: IF condition THEN statements; ELSIF condition THEN statements; ELSE statements; END_IF;
- case: CASE selector OF value1: statements; value2: statements; ELSE statements; END_CASE;
- for: FOR index := start TO end BY step DO statements; END_FOR;
Best Practices for Structured Text:
- Use meaningful variable names with consistent naming conventions
- Initialize all variables at declaration to prevent undefined behavior
- Use enumerated types for state machines instead of magic numbers
- Break complex expressions into intermediate variables for readability
- Use functions for reusable calculations and function blocks for stateful operations
Common Mistakes to Avoid:
- Using = instead of := for assignment (= is comparison)
- Forgetting semicolons at end of statements
- Integer division truncation - use REAL for decimal results
- Infinite loops from incorrect WHILE/REPEAT conditions
Typical Applications:
1. PID control: Directly applicable to Pump Control
2. Recipe management: Related control patterns
3. Statistical calculations: Related control patterns
4. Data logging: Related control patterns
Understanding these fundamentals prepares you to implement effective Structured Text solutions for Pump Control using Mitsubishi GX Works2/GX Works3.
Implementing Pump Control with Structured Text
Pump control systems use PLCs to regulate liquid flow in industrial processes, water treatment, and building services. These systems manage pump operation, protect equipment, optimize energy use, and maintain process parameters.
This walkthrough demonstrates practical implementation using Mitsubishi GX Works2/GX Works3 and Structured Text programming.
System Requirements:
A typical Pump Control implementation includes:
Input Devices (Sensors):
1. Pressure transmitters for discharge and suction pressure: Critical for monitoring system state
2. Flow meters (magnetic, ultrasonic, or vortex): Critical for monitoring system state
3. Level transmitters for tank or wet well level: Critical for monitoring system state
4. Temperature sensors for bearing and motor monitoring: Critical for monitoring system state
5. Vibration sensors for predictive maintenance: Critical for monitoring system state
Output Devices (Actuators):
1. Variable frequency drives (VFDs) for speed control: Primary control output
2. Motor starters (DOL or soft start): Supporting control function
3. Control valves for flow regulation: Supporting control function
4. Isolation valves (actuated for remote operation): Supporting control function
5. Check valves to prevent backflow: Supporting control function
Control Equipment:
- Centrifugal pumps for high flow applications
- Positive displacement pumps for metering
- Submersible pumps for wet well applications
- Booster pump systems for pressure maintenance
Control Strategies for Pump Control:
- constant: Maintain fixed speed or output
- pressure: PID control to maintain discharge pressure setpoint
- flow: PID control to maintain flow rate setpoint
- level: Control tank/wet well level within band
Implementation Steps:
Step 1: Characterize pump curve and system curve
In GX Works2/GX Works3, characterize pump curve and system curve.
Step 2: Size VFD for application (constant torque vs. variable torque)
In GX Works2/GX Works3, size vfd for application (constant torque vs. variable torque).
Step 3: Implement primary control loop (pressure, flow, or level)
In GX Works2/GX Works3, implement primary control loop (pressure, flow, or level).
Step 4: Add pump protection logic (minimum flow, temperature, seal)
In GX Works2/GX Works3, add pump protection logic (minimum flow, temperature, seal).
Step 5: Program lead/lag sequencing with alternation
In GX Works2/GX Works3, program lead/lag sequencing with alternation.
Step 6: Implement soft start/stop ramps for smooth operation
In GX Works2/GX Works3, implement soft start/stop ramps for smooth operation.
Mitsubishi Function Design:
Function block (FB) programming in Mitsubishi creates reusable logic modules with defined interfaces encapsulating complexity. FB definition includes input variables (VAR_INPUT), output variables (VAR_OUTPUT), internal variables (VAR), and retained variables (VAR_RETAIN) maintaining values between calls. Creating motor control FB: inputs include Start_Cmd (BOOL), Stop_Cmd (BOOL), Speed_SP (INT), outputs include Running_Sts (BOOL), Fault_Sts (BOOL), Actual_Speed (INT), internal variables store timers, state machine stages, and diagnostic counters. FB instantiation creates instance: Motor1 (Motor_FB) with unique variable storage, allowing multiple instances Motor1, Motor2, Motor3 controlling different motors using same logic. Array of FB instances: Motors : ARRAY[1..10] OF Motor_FB accessed as Motors[3].Running_Sts checking status of motor 3. Standard function (FUN) differs from FB by lacking internal memory, suitable for calculations or conversions: Temp_Conversion_FUN(Celsius) returns Fahrenheit without retaining historical data. Structured text programming within FBs/FUNs provides clearer logic for complex algorithms compared to ladder: IF-THEN-ELSIF-ELSE structures, FOR loops, CASE statements expressing intent more directly than ladder equivalents. EN/ENO functionality enables conditional execution: EN (enable input) controls whether FB executes, ENO (enable output) indicates successful execution detecting errors within block. Library management exports FBs to library files (.glib) shared across projects and engineering teams, versioned to track modifications and ensure consistency. The intelligent function module (IFM) templates provide pre-built FBs for common applications: PID control, analog scaling, motion positioning reducing development time and providing tested reliable code. Simulation mode tests FB logic without hardware, allowing desktop development and unit testing before commissioning. Protection functionality encrypts FB contents preventing unauthorized viewing or modification, useful for proprietary algorithms or OEM machine builders distributing programs to end users.
Common Challenges and Solutions:
1. Preventing cavitation at low suction pressure
- Solution: Structured Text addresses this through Powerful for complex logic.
2. Managing minimum flow requirements
- Solution: Structured Text addresses this through Excellent code reusability.
3. Coordinating VFD speed with system pressure
- Solution: Structured Text addresses this through Compact code representation.
4. Handling pump cycling with varying demand
- Solution: Structured Text addresses this through Good for algorithms and calculations.
Safety Considerations:
- Dry run protection using flow or level monitoring
- Overtemperature protection for motor and bearings
- Overload protection through current monitoring
- Vibration trips for mechanical failure detection
- Emergency stop with proper system depressurization
Performance Metrics:
- Scan Time: Optimize for 5 inputs and 5 outputs
- Memory Usage: Efficient data structures for FX5 capabilities
- Response Time: Meeting Water & Wastewater requirements for Pump Control
Mitsubishi Diagnostic Tools:
Device memory monitor: Real-time table displaying current values for X, Y, M, D devices with force capability,Entry data monitor: Shows actual rung logic states with contact ON/OFF indication during program execution,Device test: Manually control outputs and set internal relays for wiring verification without program influence,Intelligent module diagnostics: Buffer memory display showing module status, error codes, and configuration,Scan time monitor: Displays current, maximum, and minimum scan times identifying performance issues,Error code history: Chronological log of system errors, module faults, and CPU events with timestamps,CC-Link/network diagnostics: Visual network status showing connected stations, errors, and communication statistics,SD card operation log: Records all SD card read/write operations, file transfers, and access timestamps,Remote diagnosis via Ethernet: Connect GX Works over network for monitoring and troubleshooting without local access,Sampling trace: Records device value changes over time with trigger conditions for intermittent fault analysis,System monitor: Displays CPU load, memory usage, and battery status for predictive maintenance,Safety diagnosis (safety CPU): Dedicated diagnostics for safety I/O discrepancy detection and emergency stop chain status
Mitsubishi's GX Works2/GX Works3 provides tools for performance monitoring and optimization, essential for achieving the 2-4 weeks development timeline while maintaining code quality.
Mitsubishi Structured Text Example for Pump Control
Complete working example demonstrating Structured Text implementation for Pump Control using Mitsubishi GX Works2/GX Works3. Follows Mitsubishi naming conventions. Tested on FX5 hardware.
(* Mitsubishi GX Works2/GX Works3 - Pump Control Control *)
(* Structured Text Implementation for Water & Wastewater *)
(* Mitsubishi programming supports both traditional device addressing (M0 *)
PROGRAM PRG_PUMP_CONTROL_Control
VAR
(* State Machine Variables *)
eState : E_PUMP_CONTROL_States := IDLE;
bEnable : BOOL := FALSE;
bFaultActive : BOOL := FALSE;
(* Timers *)
tonDebounce : TON;
tonProcessTimeout : TON;
tonFeedbackCheck : TON;
(* Counters *)
ctuCycleCounter : CTU;
(* Process Variables *)
rPressuretransmitters : REAL := 0.0;
rCentrifugalpumps : REAL := 0.0;
rSetpoint : REAL := 100.0;
END_VAR
VAR CONSTANT
(* Water & Wastewater Process Parameters *)
C_DEBOUNCE_TIME : TIME := T#500MS;
C_PROCESS_TIMEOUT : TIME := T#30S;
C_BATCH_SIZE : INT := 50;
END_VAR
(* Input Conditioning *)
tonDebounce(IN := bStartButton, PT := C_DEBOUNCE_TIME);
bEnable := tonDebounce.Q AND NOT bEmergencyStop AND bSafetyOK;
(* Main State Machine - Pattern: State machine implementation in Mitsubis *)
CASE eState OF
IDLE:
rCentrifugalpumps := 0.0;
ctuCycleCounter(RESET := TRUE);
IF bEnable AND rPressuretransmitters > 0.0 THEN
eState := STARTING;
END_IF;
STARTING:
(* Ramp up output - Gradual start *)
rCentrifugalpumps := MIN(rCentrifugalpumps + 5.0, rSetpoint);
IF rCentrifugalpumps >= rSetpoint THEN
eState := RUNNING;
END_IF;
RUNNING:
(* Pump Control active - Pump control systems use PLCs to regulate liquid f *)
tonProcessTimeout(IN := TRUE, PT := C_PROCESS_TIMEOUT);
ctuCycleCounter(CU := bCyclePulse, PV := C_BATCH_SIZE);
IF ctuCycleCounter.Q THEN
eState := COMPLETE;
ELSIF tonProcessTimeout.Q THEN
bFaultActive := TRUE;
eState := FAULT;
END_IF;
COMPLETE:
rCentrifugalpumps := 0.0;
(* Log production data - High-speed data logging in Mitsubishi uses file registers (R devices) organized as circular buffers with automatic SD card archiving for long-term storage. Create logging structure: file registers R0-R9999 storing 10,000 samples with each sample containing timestamp (R[base]), values (R[base+1] to R[base+10]), status (R[base+11]). Write pointer (D500) increments with each log entry: [MOV current time R[(D500*12)]] [MOV process values R[(D500*12)+1]] [INC D500] with modulo operation wrapping pointer [LD> D500 K9999] [MOV K0 D500]. Triggered logging initiates capture on alarm conditions preserving pre-trigger buffer: maintain continuous logging but flag trigger index enabling post-event retrieval of 100 samples before alarm and 500 samples after providing failure context. CSV file export uses SD card write instructions formatting file register data into comma-delimited text files readable by Excel or data analysis software: SDWR instruction writes R0-R9999 to SD:\LOG\data.csv with timestamp filename generation creating unique files daily. Sampling rates configurable from 10ms (fixed cycle interrupt program) to several minutes (main program logic) depending on process dynamics and storage capacity requirements. Data compression implements deadband filtering: log sample only when value changes exceed threshold reducing storage requirements for slowly-changing process variables like tank levels or temperatures. Integration with SCADA/historian systems uses SLMP protocol transferring logged data via Ethernet to centralized databases with automatic retry logic handling network interruptions preventing data loss. Batch correlation links production data to specific product lots: each batch start creates new log file section with batch ID header enabling traceability from raw materials through finished goods. Energy logging totalizes consumption from power meters connected via CC-Link or Modbus calculating specific energy per produced unit, identifying efficiency improvements and cost allocation by product line. Safety event logging captures all safety input states, bypass activations, and emergency stop events with tamper-proof timestamps meeting regulatory documentation requirements for incident investigations and compliance audits. *)
eState := IDLE;
FAULT:
rCentrifugalpumps := 0.0;
(* Alarm management in Mitsubishi uses bit devices (M or B) for alarm active flags with corresponding data registers storing timestamps, values, and alarm details. Alarm structure allocates device ranges: M1000-M1999 for alarm active flags (1000 unique alarms), D5000-D5999 storing alarm timestamps or associated values. Alarm detection logic: [LD Tank_Level > High_Limit] [AND NOT previous alarm state M1000] [OUT M1000] [MOV current time D5000] capturing alarm activation moment. Alarm acknowledgment requires operator action via HMI: GOT screen button writes to acknowledgment bit (M2000) which resets alarm flag when condition clears [LD M1000] [AND alarm cleared] [AND M2000 acknowledged] [RST M1000] [RST M2000]. Priority classification uses different device ranges or separate bits: Critical alarms M1000-M1099, Warnings M1100-M1199, Information M1200-M1299 with severity-specific visual/audible HMI indicators. Alarm logging to SD card uses CSV file write instructions (SDWR) recording alarm number, timestamp, activation/deactivation, and associated process values for historical analysis and regulatory compliance. First-out alarm detection latches initial alarm in cascade of related faults: bearing temperature alarm (M1050) latches before motor overload (M1051) before production stopped (M1052) with reset sequence clearing in reverse order after root cause addressed. Integration with GOT HMI alarm viewer displays active alarms in sortable/filterable list with acknowledgment tracking, alarm help text, and corrective action guidance displayed to operators. Alarm rate limiting prevents flooding when single fault triggers hundreds of consequential alarms: introduce 5-second delays before enabling secondary alarms allowing operators to focus on root cause. Email notification for critical alarms uses Ethernet communication function blocks sending SMTP messages to distribution lists with alarm details formatted in message body. Statistical alarm analysis counts alarm frequencies storing totals in file registers: most frequent alarm identification guides preventive maintenance priorities addressing chronic equipment issues before failures occur. *)
IF bFaultReset AND NOT bEmergencyStop THEN
bFaultActive := FALSE;
eState := IDLE;
END_IF;
END_CASE;
(* Safety Override - Always executes *)
IF bEmergencyStop OR NOT bSafetyOK THEN
rCentrifugalpumps := 0.0;
eState := FAULT;
bFaultActive := TRUE;
END_IF;
END_PROGRAMCode Explanation:
- 1.Enumerated state machine (State machine implementation in Mitsubishi typically uses data registers (D devices) storing current state values with ladder logic evaluating state transitions. Define state constants using file registers or direct values: STATE_IDLE = 0, STATE_STARTING = 10, STATE_RUNNING = 20, STATE_STOPPING = 30, STATE_FAULT = 90 with spaced values allowing future state insertion. Current state stored in D0 with comparison instructions (LD= D0 K0) checking states and advancement logic incrementing or setting new state values (MOV K10 D0). Timer-based state transitions use timer completion contacts: [TON timer T0 reaches preset] [AND current state = STARTING] [THEN advance to RUNNING state MOV K20 D0]. Structured text programming within function blocks provides clearer state machine logic: CASE Machine_State OF 0: (IDLE state actions and transition evaluation), 10: (STARTING state actions), 20: (RUNNING state actions), END_CASE. State transition logging writes state changes to file registers creating audit trail: when D0 changes, copy timestamp and previous state to R[pointer] incrementing pointer for circular buffer. Fault handling sets state to FAULT (90) with fault code stored in separate register (D10) indicating cause: 100=Emergency_Stop, 101=Overload, 102=Communication_Loss, with reset logic evaluating fault code and returning to appropriate safe state. Parallel state machines coordinate through shared status bits: Machine1_State (D100), Machine2_State (D200) with interlock logic preventing conflicting operations. HMI integration displays state names using text switching on D0 value converting numeric states to operator-friendly descriptions: 0='Ready', 10='Starting', 20='Running'. Function block encapsulation creates reusable state machine logic instantiated multiple times for identical equipment with instance-specific state storage in FB internal variables.) for clear Pump Control sequence control
- 2.Constants define Water & Wastewater-specific parameters: cycle time 30s, batch size
- 3.Input conditioning with debounce timer prevents false triggers in industrial environment
- 4.STARTING state implements soft-start ramp - prevents mechanical shock
- 5.Process timeout detection identifies stuck conditions - critical for reliability
- 6.Safety override section executes regardless of state - Mitsubishi best practice for intermediate systems
Best Practices
- ✓Follow Mitsubishi naming conventions: Mitsubishi programming supports both traditional device addressing (M0, D100, X1
- ✓Mitsubishi function design: Function block (FB) programming in Mitsubishi creates reusable logic modules wit
- ✓Data organization: Mitsubishi uses file registers (R devices) and structured data in function block
- ✓Structured Text: Use meaningful variable names with consistent naming conventions
- ✓Structured Text: Initialize all variables at declaration to prevent undefined behavior
- ✓Structured Text: Use enumerated types for state machines instead of magic numbers
- ✓Pump Control: Use PID with derivative on PV for pressure control
- ✓Pump Control: Implement soft start ramps even with VFD (200-500ms)
- ✓Pump Control: Add flow proving before considering pump operational
- ✓Debug with GX Works2/GX Works3: Use sampling trace to capture high-speed events occurring faster than
- ✓Safety: Dry run protection using flow or level monitoring
- ✓Use GX Works2/GX Works3 simulation tools to test Pump Control logic before deployment
Common Pitfalls to Avoid
- ⚠Structured Text: Using = instead of := for assignment (= is comparison)
- ⚠Structured Text: Forgetting semicolons at end of statements
- ⚠Structured Text: Integer division truncation - use REAL for decimal results
- ⚠Mitsubishi common error: Error 2110: Illegal device specified - accessing device outside configured range
- ⚠Pump Control: Preventing cavitation at low suction pressure
- ⚠Pump Control: Managing minimum flow requirements
- ⚠Neglecting to validate Pressure transmitters for discharge and suction pressure leads to control errors
- ⚠Insufficient comments make Structured Text programs unmaintainable over time