Energy management and responsible handling of resources is currently the number one topic in industry. In light of this, the Automation Initiative of German Automobile Manufacturers (AIDA) asked PI (PROFIBUS & PROFINET International) to provide functions and mechanisms for PROFINET that support energy-efficient production.

In response, PI is working on a vendor-neutral energy savings profile called PROFIenergy. The objective is to develop a uniform (standardized) interface for data exchange between a controller and a wide range of devices with energy savings options. The profile will be used for exchanging data and commands, but will not contain any logic functions in terms of process control. The first release of PROFIenergy should be available by the end of 2009.

Energy-efficient production means more than just the use of variable-speed drives and efficient motors. The question going forward is how to selectively place complete production lines or portions thereof into standby mode during unproductive times. Ethernet networks such as PROFINET play a key role in this.

The launch of PROFINET IO for plant communication in November 2004 represented a decisive step in the commitment to modern Ethernet technology: According to the conceptions of AIDA, each plant component—whether an industrial robot, a converter, a process control system, or an I/O module—should be accessible in the future via a uniform and comprehensive communication infrastructure, ideally through Ethernet-based protocols such as PROFINET. Each component of the higher-level control system or the line PLC can then be selectively activated and controlled via the IP address and the device name.

In short: The decision to introduce PROFINET laid the foundation for a new and forward-looking energy management. Future-looking energy management means: switching off equipment is no longer accomplished by means of the conventional and very “coarse” main switch method but rather by means of the network. The general supply network of components remains activated, and the components, when initiated by a “network command,” pass into a defined energy-saving mode.

Energy-efficiency modes

One possible solution involves the definition of different energy-saving modes for devices. When developing the energy efficiency modes, an attempt was made to allow for the diversity and technical options of as many component groups and suppliers as possible.

Mode 0
If PC-based systems are used, as is the case for some process controllers or robot controllers, the standard “Wake on LAN” service, also referred to as “Magic Packet,” can be used in many cases. With this technology, the controller passes into an extreme energy savings mode. All energy-consuming systems of components are shut down, switches integrated into the component and the PROFINET IO stack are deactivated, and safety-relevant functions of components are no longer supported. Only the connection to the network is kept alive in order to react to the wake-up command in the form of the “Magic Packet.”

Mode 1
This mode was defined specifically for highly integrated components. It differs from Mode 0 only in that the PROFINET IO stack and, thus, the integrated switches remain activated—meaning that the network infrastructure continues to function. IO statuses of the component are still not available, and the transition to a higher mode is initiated by standardized PROFINET protocol.

Mode 2
Mode 2 is targeted specifically at modular IO modules. In this mode, the PROFINET IO stack and the integrated switches are active, and IO statuses and safety-relevant functions are available in some cases, depending on the preceding configuration. The transition to operating mode is initiated by standardized PROFINET protocol.

Mode 3
Operating mode – all subsystems of the component are activated, and the component signals that it is “ready to operate.”

For simpler configuration of the overall system, information is needed regarding the energy efficiency modes supported by the component along with its time behavior. Since PROFINET IO is the communication layer of the future power management level, it would be useful to describe the individual capabilities of a component in the GSDML file. Among other things, the standardized description would indicate which energy efficiency modes the component supports and the length of the individual power-up times until the "ready-to-operate" status is reached. The higher-level management software can use this information to calculate the time- and energy-optimized power-up of the (sub) system from the individual parameters, that is, to achieve the optimal sequence.

As described previously, all changeovers from one energy efficiency mode to another, except for "wake up" from Mode 0, are managed via the PROFINET IO communication layer. For this purpose, PI is offering a standardized data record that allows the required mode transitions ...