A safe and reliable “pilot”

The PSS 4000 system by Pilz offers an important contribution to the safety and control of automated guidance transport.

Managers of logistics centers demand transport systems that are ever more flexible and high performance, but also reliable and, most importantly, safe. For this reason, many builders of automated guided vehicles (AGVs) rely on the PSS 4000 command and control system by Pilz. At the heart of the system are modular I/Os and an openness to third party communication protocols. Giovanni Sangiorgio, Product Manager at Pilz Italia, discusses the motion control of these driverless vehicles and the advantages it offers.

Motion control used to guarantee a flexible and safe process includes functions such as stationary axis control and motion direction detection. What does Pilz offer?
Pilz solutions for controlling speed and stops are customizable, scalable and flexible. With one axis, stand-alone “adjustable parameter” modules like PNOZ s30 can be used; for managing multiple axes simultaneously, scalable modular systems with integrated speed and stationary axis control, like PNOZmulti can be employed. On the other hand, for obtaining higher performance or dynamic functions, with PMCprotego DS drive Pilz makes it possible to manage electric axes. Last but not least, for installations with network distributed control logic (for example, lines made up of independent module machinery), it is possible to use the PSS 4000 automation system for speed threshold control, stationary axis and secure positioning.

What are the advantages of PSS 4000 motion control and the added value generated for customers?
PSS 4000 motion control safety is managed by the system’s software application. The advantage lies in the verification of signals from the two non-safety encoders, which simultaneously and securely controls speed, motion direction, positioning and the stationary axis, in compliance with the strictest UNI EN ISO 13849-1 and CEI EN 62061 standards.
Therefore, even though they are used as standard type encoder sensors, they make it possible to monitor speed and position, combining safety counter interfaces and special certified software packages.

TÜV certification prevents users from having to develop and certify their own software, thus saving time and costs. Thanks to the secure network connection to multiple control modules via SafetyNET p real-time Ethernet, it is possible to achieve a scalable system with axis data available to all PSS 4000-connected controls.

And so the safety function is made dynamic and can be more freely adapted to the application…
Exactly. In fact, the designers can set flexible reactions, according to magnitudes that can vary over time, and manage the intervention thresholds in a dynamic fashion. The parameters don’t have to be set beforehand or on the basis of a preset quantity of limit values; calculations can be adapted to the production process in a dynamic and continuous manner.    
     

Flexible solution for logistics installations
The PSSuniversal PLC safety systems, the beating heart of the PSS 4000 automation system by Pilz, are available in two versions: PSSuniversal PLC with two SafetyNET p interfaces and PSSuniversal PLC with one SafetyNET p interface and one Profibus-DP slave interface.
These PLCs can manage standard and/or safety functions using the EN/IEC 61131-3 standard languages. PAS IL (instruction list) and PAS STL (structured text) are already available, in addition to the graphic programming language PASmulti. The default software modules for standard and safety functions guarantee a high grade of standardization in applications.

Secure motion, in any direction. Latest generation automation applied to AGVs enables, for example, optimal management of pallets in logistics centers, increasing the number of pallets processed within a given timeframe and keeping all variables under control. Each automated guided vehicle can be equipped with a Pilz PSSuniversal safety PLC to control its speed and direction, while at the same time, supervising the safety area in terms of measured speed and turn angle (as the speed increases, the compliance threshold is increased). Furthermore, it is possible to detect any unexpected motion of the load during transport by installing a photoelectric barrier system of the same PSSuniversal PLC series as the AGV, which configures and manages stopping.

Speed, position and stationary axis. PSSuniversal PLCs can also manage the AGV loading and unloading process by properly installing standard sensors and actuators; the Pilz PLC’s “safety counter” interface, combined with certified software packages, enables controlling speed, positioning and stationary axis, guaranteeing compliance with governing laws.
Thanks to SafetyNET p real-time Ethernet protocol, the components of the automation system can be connected online and transmit data relating to both standard and safety functions. PSSuniversal programmable controls, in combination with the programming environment PAS4000 and program graphic editor PASmulti (in addition to standard EN/IEC 61131-3 standard languages), simplify the use of automation even for updating existing applications.