Method: The Selmo PTF process

1. Introduction

The PTF process Selmo (Process – Technology – Function) describes the methodical approach taken before a process model is created and automated code is generated. It ensures clarity, consistency and traceability and thus forms the foundation of the entire Selmo approach.

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2. The three levels

2.1 Process (P) – Sequence and logic

• Definition of the logical sequence

• Description of all states and transitions

• Modeling of a state machine

👉 Result: A clear understanding of the process, independent of technical details.

2.2 Technology (T) – Components used

• Analysis of the available hardware (sensors, actuators, interfaces)

• Definition of the operation and characteristics

• Assignment of the measurement and control signals to the process

👉 Result: The process is linked to the real technology.

2.3 Function (F) – Building blocks of implementation

• Identification of the required functions (e.g. adder, cylinder control, test module)

• Clear description of inputs, outputs, limits and behavior

• Functions are encapsulated, reusable and testable

👉 Result: Building blocks that can be cleanly integrated into the process.

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3. Interaction of P, T and F

• process describes the “when” (sequence, state changes).

• technology defines the “with what” (components, interfaces).

• Function determines the “how” (concrete implementation).

This separation provides: ✅ Clarity in design ✅ Transparency in operation ✅ Safety and efficiency when making changes

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4. Practical example: The flap

Let’s take a flapthat is to open and close:

1. Process level: – Logic: “When part is inserted → close flap; after processing → open flap.” – The sequence is unambiguously described in the model.

2. Technology level: – Flap cylinder, limit sensors, possibly jam sensor. – Sensor reports “0 = free.”

3. Function level: – Function “close flap”: issue signal → cylinder moves → wait for feedback.

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The deviation in reality

Although the sensor reports “0”, a backlog may be present → the flap is blocked.

• In the Model is defined: “close flap.”

• In Reality it does not happen.

• Selmo recognizes: deviation between target and actual.

• Immediately a clear message appears on the HMI: “Flap zone – deviation”.

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5. The effect of the PTF process

• The process is described clearly and deterministically.

• Deviations in reality become immediately visible.

• Errors are transparent, analyzable and quickly removable.

• Iterative changes (hardware, process) can be specifically traced back into the model and remain consistent.

👉 In this way the PTF process connects formal rigor with practical manageability.

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