There are different viewing angles for SELMO. On the one hand, a machine or system is always viewed from the point of view of personal safety. For this purpose, a risk analysis is made based on existing standards.
However, the focus and responsibility for process reliability lie particularly with the engineers. Understanding individual processes and dividing them into process steps is definitely one of the greatest challenges in mechanical engineering. The process safety itself lies in the mastery of work steps or functional groups. If something has to be cut, the cutting process must be reliable. It is almost impossible to automate unstable processes or to fix them with software.
We can increase the functional stability to almost 100 % with SELMO. The function of the machine or plant is defined by the process and the assemblies used. With SELMO, each process is broken down into steps. Only the steps that are defined are permitted.
SELMO assumes a basic position. A sequential sequence of steps starts from this position. Each step has a defined subsequent step. In each step, the entire system of the step chain (sequence) is monitored for correctness. We define this as monitoring. Every single bit that is processed in the SEQUENCE is checked for its correct value. This leads to a 100 % defined system. Each step change takes place when no bit contradicts it. This means that text can be displayed for each bit to inform the operator.
This leads to absolute operator safety. SELMO is structured in such a way that every single bit in the system is displayed. Behind each bit, there is a signal, an assembly evaluation (e.g. temperature at a switching point - discrete signal) or an HMI signal (e.g. operator key).
For the operability of a machine, it is becoming increasingly important to create uniform structures so that operators can work quickly and easily on different machines. It is important to ensure that this requirement is clearly defined when purchasing machines. If the operator interface has a uniform structure, a new machine can be integrated quickly with little training effort. The uniform structure also defines the interfaces to other machines. The standardised connection to the business processes is particularly important. Different disciplines or experts are needed to use such interfaces to bring the data from the customer to production and there to the machine. Conversely, a lot of data has to come back from the machine to the customer through records. A broader perspective is the maintenance of machines. Software that is guaranteed to have the same structure is easier to understand. It is easily exchangeable. Structures that are easy to learn lead to high maturity of the software.
The clear separation of logic and function in SELMO makes it easy to exchange modules. Just as in the office sector when installing a new printer, with SELMO there is no longer any need for a programr of an operating system. No operating system needs to be replaced either. SELMO thus wants to introduce the principle of PlugnPlay in mechanical engineering.
SELMO's driver concept is based on the separation of the executing function from the process sequence. The logical sequence does not change when a drive is to be replaced. The drive must be easily replaceable mechanically, electrically and in terms of software - even if the drive is not identical in construction. Flexibility in SELMO machines is provided by the driver structure. Mechanics and electrics can be exchanged worldwide by experts. The software reaches the same level of maturity with SELMO and is specifically exchanged by swapping the function in the form of drivers.
The aim is:
•to have the drivers for SELMO created by SELMO users.
•to develop each function only once tested and certified.
This means that a driver can be managed as an item in an ERP system and the development costs can be refinanced through use.
With SELMO, you only buy new software and use your existing drivers or purchase them cheaply via SELMO.
SELMO is changing the machine procurement process. SELMO offers an innovative standard for machine software and redefines its creation process. For new machines, the manufacturing process is placed at the centre. All experts define the requirements via the process. The process is divided into logical sequences. Four elements are available for this purpose:
1.State (Step): The simple step-by-step element. Each step has a clear subsequent step and a designation.
2.Timer (time): In the modelling of processes, steps are applicable for a certain time.
3.Loop: The element summarises steps and repeats them as often as determined.
4.Decision: The element allows a step to have two subsequent steps depending on the condition.
With this element, nestings can be built. The logical process is a deterministic, finite automaton with a defined starting point and defined endpoint. After reaching the endpoint, the process starts again at the start point. This repeats until a condition stops the process or an error occurs.
The system is defined in the system layer, in which the assemblies needed for the process are placed bit by bit. There are three types of zones that are inserted per bit:
Zone type 1: Input only without output. This zone has its feedback from the operator - from a sensor that interrogates a part.
Zone type 2: Output and input as feedback. An output is set in a certain state and the feedback is expected.
Zone type 3: Only output without feedback. This also exists when a lamp is switched or a drive is switched across several states.
Each zone with an output also has a button on the HMI by definition of SELMO. It is also defined that grouped zones of type 2 always have a pair check. This means that only one signal may be present in the group. With a pneumatic cylinder, for example, there can only be an error message if the rear end position and the front end position are present at the same time.
The SELMO standard has a parameter layer. The input and output data points are defined there. This makes the process flexible and adaptable. Example: A saw that moves to a position and cuts where the position is reached. This is always the same process, but the position can be changed. Or, for example, a drive with different speeds. All data in and out of the machine The display layer in SELMO has a standardised SEQUENCEcontrol. Other images on the HMI are easily created within the framework of the data points in the model.