1. Definition of Control Function Execution

Control Function Execution is the control domain that converts required machine functions into executable operating units and systematically defines the start, progress, completion, interruption, and return conditions of each operation.

In mechanical design, functions are generally defined in terms of purpose, such as:

• Feed the product.

• Align the product.

• Clamp the product.

• Cut the product.

• Inspect the product.

• Discharge the completed product.

However, these functional definitions alone are not sufficient to operate the machine.

To execute each function, the following items must be defined in detail:

• Which device operates

• Under what conditions the operation begins

• At what position, speed, or force the device operates

• How completion is determined

• What happens if the operation is not completed within the allowable time

• Which state the machine enters if an abnormal condition occurs during execution

• What conditions are required to transition to the next function

Control Function Execution is therefore an implementation framework that converts the functional intent of the machine into actual control commands and state transitions.

2. Position of Control Function Execution

The functional execution flow of general machinery can be organized as follows:

Requirements → Machine Function → Mechanism → Function Execution Control → State Verification → Transition to the Next Function

The role of each area is as follows:

Control Function Execution is not the domain in which the mechanism itself is designed.

For an already defined mechanism, it determines:

• When it should operate

• In what sequence it should operate

• To what extent it should operate

• When it should stop

• Which state it should enter after completion

3. Distinction Between Function and Action

Function and action must be clearly distinguished.

3.1 Function

A function is the result the machine must produce in the product or process.

Examples:

• Product positioning

• Product clamping

• Metered feeding

• Cutting

• Heating

• Inspection

• Discharge

3.2 Action

An action is the physical operation performed by an actual device in order to realize the function.

Examples:

• Conveyor motor rotation

• Stopper cylinder rise

• Clamp cylinder extension

• Servo-axis descent

• Heater output increase

• Discharge cylinder extension

One function may consist of several actions.

For example, the product-clamping function may consist of:

1. Confirm product arrival.

2. Extend the side guide.

3. Lower the upper clamp.

4. Build clamping pressure.

5. Confirm clamping completion.

Control design should therefore not merely list actions. It must connect each action to the functional result it is intended to produce.

4. Functional Execution Units

If the entire machine operation is written as one long sequence, modification, testing, and recovery become difficult.

The machine function should therefore be divided into functional execution units that can be independently executed and verified.

Typical functional execution units include:

• Product Feeding

• Product Detection

• Positioning

• Alignment

• Clamping

• Processing

• Inspection

• Unclamping

• Discharge

• Return

• Cleaning

• Homing

Each functional execution unit should include the following items:

5. Basic Structure of Function Execution

A function is generally executed through the following flow:

Idle → Start Condition Check → Command Execution → Operation in Progress → Completion Verification → Result Confirmation → State Transition

5.1 Idle

The function is not active and waits for the start conditions.

5.2 Start Condition Check

The system verifies that the conditions required to execute the function safely and correctly have been satisfied.

5.3 Command Execution

Execution commands are sent to motors, cylinders, valves, heaters, and other devices.

5.4 Execution

The device operates toward the target state.

5.5 Completion Verification

The system confirms whether the function is complete using sensors, encoders, pressure, time, or process results.

5.6 Result Confirmation

The system confirms not only that a completion signal has been received, but also that the intended functional result has actually been achieved.

5.7 State Transition

According to the result, the system transitions to the next function, an idle state, or a fault state.

6. Definition of Start Conditions

A function should not begin immediately simply because a command has been issued.

The required conditions must be verified before execution.

6.1 Device Readiness Conditions

• Is the motor ready to operate?

• Is the servo properly enabled?

• Is pneumatic or hydraulic pressure within the normal range?

• Are the valves and drives free from faults?

• Has homing been confirmed?

6.2 Process Readiness Conditions

• Is the product in the specified position?

• Has the previous process been completed?

• Is the next process ready to receive the product?

• Is the required tool installed?

• Are the settings and recipe valid?

6.3 Machine-State Conditions

• Is there no possibility of collision?

• Are other axes or devices outside the interference zone?

• Is the function permitted in the current operating mode?

• Is the current machine state suitable for execution?

6.4 Safety Conditions

• Is the safety door in the correct condition?

• Has the emergency stop been released?

• Is the hazardous area free of personnel?

• Are the required safety functions available?

Start conditions are not merely a list of sensor inputs. They are a set of conditions that demonstrate that the function can be executed.

7. Structure of Execution Commands

A function-execution command should contain a specific target rather than only an ON/OFF instruction.

7.1 Discrete Command

A discrete command switches a device between two or a limited number of states.

Examples:

• Valve ON/OFF

• Clamp forward/reverse

• Brake apply/release

• Heater enable/disable

7.2 Setpoint Command

A setpoint command specifies the target value the device must reach.

Examples:

• Position: 250 mm

• Speed: 300 mm/s

• Torque: 15 N·m

• Temperature: 80°C

• Pressure: 0.5 MPa

7.3 Motion or Process Profile

A profile defines not only the target value, but also the process of reaching it.

Examples:

• Acceleration time

• Deceleration time

• Approach speed

• Working speed

• Holding time

• Multi-stage pressure

• Multi-stage temperature

7.4 Conditional Command

A conditional command changes according to the state detected during execution.

Examples:

• Decelerate when the product is detected.

• Switch to force control after contact is detected.

• Hold output after the target temperature is reached.

• Limit speed when approaching an overload condition.

A well-defined function-execution command describes not only which device should operate, but also what result must be produced, under what conditions, and through what process.

8. Design of the Execution Sequence

Machine functions may be executed sequentially, in parallel, conditionally, or repeatedly.

8.1 Sequential Execution

The next function begins after the preceding function has been completed.

Example:

Feeding → Alignment → Clamping → Processing → Discharge

Sequential execution is clear and easy to understand, but unnecessary serialization increases cycle time.

8.2 Parallel Execution

Functions that do not interfere with one another are executed simultaneously.

Examples:

• Discharge of the completed product and preparation of the next product

• Return of the machining axis and preparation for clamp release

• Product transfer and inspection-data storage

Parallel execution reduces cycle time, but the following must be reviewed:

• Physical interference between devices

• Simultaneous electrical and pneumatic demand

• Synchronization of completion conditions

• Treatment of the other function when one function fails

8.3 Conditional Execution

Different functions are executed according to product type, process result, or machine state.

Examples:

• Different discharge routes for accepted and rejected products

• Different position commands according to product size

• Additional processing when rework is required

• Speed changes according to process conditions

8.4 Repetitive Execution

A function is repeated until a specified condition is satisfied.

Examples:

• Feed until the specified quantity is reached

• Pressurize until the specified pressure is reached

• Align until the product position enters the allowable range

• Retry within a limited number of attempts

Every repetitive structure must have a termination condition and a maximum repeat count.

9. Definition of Completion Conditions

Issuing a command does not mean that the function is complete.

Completion must be determined based on the actual result.

9.1 Position-Based Completion

• Target position reached

• Limit sensor detected

• Encoder position error within the allowable range

• Cylinder forward or reverse completion

9.2 Speed-Based Completion

• Target speed reached

• Rotating element fully stopped

• Speed maintained within the allowable range

• Speed synchronization between axes completed

9.3 Force- and Pressure-Based Completion

• Required clamping force achieved

• Target pressure reached

• Pressing force maintained

• Target torque reached

9.4 Temperature- and Process-Value-Based Completion

• Target temperature reached

• Holding time completed

• Target weight reached

• Specified flow quantity supplied

9.5 Product-Result-Based Completion

• Product position confirmed

• Processing completion detected

• Inspection passed

• Discharge completion confirmed

The more critical the function, the more important it becomes to verify the final product or process result directly rather than relying only on actuator completion.

10. Completion Conditions and Hold Conditions

In some functions, temporary achievement of the target state is not sufficient for completion.

For example, if pressure reaches the target only momentarily and immediately drops, clamping cannot be considered properly maintained.

The following should therefore be distinguished.

Completion Condition

The condition used to determine that the target state has been reached.

Hold Condition

The condition used to verify that the achieved state remains stable for the required period.

Examples:

• Maintain the target pressure for at least one second.

• Maintain position error within ±0.1 mm.

• Maintain the target temperature for five seconds.

• Maintain speed below the stop threshold for a defined period.

11. Timeout and Time Conditions

Every function has a reasonable execution time.

If the function is not completed within the allowable time, it should be treated as abnormal.

11.1 Start Delay Time

The allowable time from command output until the device begins to respond.

11.2 Completion Time Limit

The maximum time within which the function must be completed.

11.3 Minimum Hold Time

The minimum duration for which a signal or state must remain active to be considered valid.

11.4 Stabilization Time

The waiting time required after operation for vibration, pressure, temperature, or other conditions to stabilize.

11.5 Inter-Function Delay

The required waiting time before transitioning to the next function.

11.6 Communication Response Time

The maximum allowable response time from an external device or controller.

Timeout values should be established based on normal machine response, load variation, environmental conditions, and process requirements rather than treated as arbitrary alarm values.

12. Function Execution by Operating Mode

The execution condition and behavior of the same function may vary according to the operating mode.

12.1 Automatic Operation

• Function executed as part of the overall sequence

• All process interlocks applied

• Completion evaluated automatically

• Automatic transition to the next function

12.2 Manual Operation

• Individual function or device directly operated

• No automatic sequence progression

• Essential safety interlocks maintained

• Collision-prevention interlocks maintained

• Limited speed applied when required

12.3 Setup Operation

• Position, speed, time, and sensor conditions adjusted

• Single-cycle operation

• Low-speed or step-by-step execution

• Restricted authority for changing settings

12.4 Homing

• Reference position search

• Deceleration-point confirmation

• Home-sensor confirmation

• Position-coordinate reset

• Homing completion confirmation

12.5 Maintenance and Cleaning Mode

• Only limited devices may be operated

• Hold-to-run operation applied

• Low-speed operation

• Some standard interlocks may be bypassed

• Core safety functions maintained

12.6 Recovery Mode

• Incomplete process state cleared

• Axis and product positions verified

• Individual devices moved to safe positions

• Residual product removed

• Conditions for re-entry into automatic operation verified

13. Coordination and Synchronization Between Functions

Machine functions do not operate independently.

Multiple functions must exchange conditions and states in order to coordinate their operation.

13.1 Handshake Between Functions

One function communicates its readiness, execution, and completion state to another function.

Typical signals include:

• Ready

• Request

• Busy

• Complete

• Fault

• Reset

13.2 Axis Synchronization

Multiple axes maintain defined position, speed, or phase relationships.

Examples:

• Synchronization of left and right lifting axes

• Synchronization of film feeding and cutting axes

• Synchronization of conveyor motion and robot pickup

• Master-axis and slave-axis following

13.3 Coordination with Upstream and Downstream Equipment

Before transferring a product in a production line, the following should be confirmed:

• Is the downstream equipment ready to receive the product?

• Is the upstream supply request valid?

• Is the transfer path clear?

• Has the product-tracking information been transferred?

14. Interruption and Pause

Different situations requiring interruption during function execution must be distinguished.

14.1 Pause

The machine temporarily stops while maintaining the current state as far as possible.

• Operation can be resumed.

• Position and process state are maintained.

• Product condition is preserved.

• Resume conditions must be verified.

14.2 Controlled Interruption

The current function is completed up to a safe stage before interruption.

14.3 Immediate Interruption

The current function is stopped immediately to prevent equipment damage or process failure.

14.4 Safety Interruption

Hazardous motion is interrupted with priority over normal function control in order to reduce risk to personnel.

The following should be defined for each interruption method:

• Outputs to be disabled

• Outputs to be maintained

• Whether the brake is applied

• Condition of the product and tool

• Whether resumption is permitted

• Recovery procedure

15. Function-Execution Failure

The following conditions may be regarded as function-execution failure:

• Start conditions are not satisfied within the specified time

• The device does not respond after the command

• The completion signal is not received

• The completion signal occurs too early

• The target value is not reached

• The required state is not maintained

• Contradictory sensors are activated simultaneously

• A possible collision with another function arises

• The product condition differs from the expected condition

• No communication response is received

When a function fails, the system should determine the response level according to the influence and risk of the failure rather than merely generating an alarm.

16. Retry and Automatic Recovery

Some function failures can be recovered through automatic retry.

Examples:

• Re-aligning the product

• Retracting and re-extending a cylinder

• Re-detecting after possible sensor contamination

• Retransmitting a communication command

• Refeeding from the supply unit

Automatic retry requires the following limits:

• Maximum retry count

• Safe state before retry

• Waiting time between retries

• Response after repeated failure

• Retry-history recording

• Functions for which retry is prohibited

Automatic retry should be restricted for functions in which repeated execution may increase risk to personnel or equipment.

17. Boundary Between Function Execution and Interlock Control

Function execution control and interlock control are connected, but their roles are different.

Function Execution Control

• Defines the function to be executed.

• Outputs commands to devices.

• Manages function progress and completion.

• Transitions to the next state.

Interlock Control

• Determines whether the function may be executed.

• Blocks commands under specific conditions.

• Prevents collisions and process errors.

• Manages release and bypass conditions.

Function execution control answers, “What must be performed?”

Interlock control answers, “May it be performed now?”

18. Boundary Between Function Execution and Safety-Related Control

Safety-related control has priority over function execution control.

Even if a function-execution command exists, hazardous output must not be permitted when safety conditions are not satisfied.

Examples:

• Even if the automatic sequence requests the machining axis to descend, execution is prohibited when the safety door is open.

• Even if the discharge function is requested, movement is prohibited when an operator is inside the hazardous area.

• If brake status is uncertain, a vertical-axis movement command is not permitted.

Safety-related control gives priority to limiting risk to personnel and equipment over normal function completion.

19. Interface with Assembly

Function execution control must correspond to the actual assembled condition.

Required Assembly Information

• Reference direction of axes and actuators

• Definition of forward/reverse and clockwise/counterclockwise

• Home and working positions

• Sensor installation positions

• Mechanical limit positions

• Relationship between stoppers and sensors

• Brake operating direction

• Normal state of valves

• Adjustable ranges

If the control-direction definitions differ from the actual assembly, the following problems may occur:

• The axis moves in the opposite direction.

• Cylinder signals are interpreted in reverse.

• Home and limit positions are exchanged.

• Brake release and application operate in reverse.

Function-execution definitions must therefore be consistent with assembly drawings, I/O lists, and commissioning criteria.

20. Interface with Manufacturing

Function execution control must reproduce the same operation across all manufactured machines.

Main Parameters to Manage

• Position setpoints

• Speed

• Acceleration and deceleration

• Torque limit

• Pressure setting

• Execution time

• Holding time

• Timeout

• Retry count

• Position tolerance

• Completion criteria

Manufacturing and Commissioning Tests

• Individual function-execution test

• Start-condition test

• Completion-condition test

• Timeout test

• Sequential-execution test

• Parallel-execution test

• Manual-operation test

• Automatic-operation test

• Interruption and resume test

• Retry test

• Fault-recovery test

21. Major Design Deliverables

The following documents are required to implement Control Function Execution.

22. Review Questions for Function Execution Control

Function Definition

• Is the final result of each function clearly defined?

• Are the function and device actions distinguished?

• Has the function been divided into appropriate execution units?

Start Conditions

• Are all conditions required before execution defined?

• Are device, process, and safety conditions distinguished?

• Are upstream and downstream readiness conditions included?

Execution Commands

• Does the command include the target state rather than only ON/OFF?

• Are position, speed, force, and time conditions defined?

• Is there a response to condition changes during execution?

Completion Determination

• Is the actual functional result verified?

• Are actuator state and product result distinguished?

• Are completion conditions and hold conditions distinguished?

• Are tolerance and stabilization time defined?

Sequence

• Are sequential and parallel executions appropriately configured?

• Is there no interference between parallel functions?

• Are conditional branches and repetitive termination conditions clear?

Fault and Recovery

• Are timeout conditions defined?

• Are function-failure conditions clear?

• Is the scope of automatic retry appropriate?

• Can the product and device states be verified after interruption?

Assembly and Manufacturing

• Does the control direction match the actual assembly direction?

• Can settings be reproduced consistently?

• Can every function be tested independently?

• Are function-specific acceptance criteria defined?

23. Conclusion

Control Function Execution is the control domain that converts functional requirements into executable commands and state transitions.

Its essence is not simply to operate a motor or cylinder.

The following relationships must be clearly defined:

• Which function should be executed

• Under what conditions the function should begin

• Which command should be sent to which device

• Which actual result confirms completion

• How the system should respond if completion does not occur within the allowable time

• Under what conditions the system should transition to the next function

• How recovery should be performed after interruption or fault

Good function execution control does not implement only normal automatic operation.

It structures machine behavior in a predictable and verifiable form across automatic, manual, setup, maintenance, and recovery modes, and enables the same function and performance to be repeatedly implemented during Assembly and Manufacturing.