Connectivity & Security – secure connection with superordinate systems

Communication is a necessary aspect of digitalisation – it is needed to integrate motors with a digital control system in the structure of a plant or to enable different services such as remote monitoring and control. Therefore, in addition to internal communication links between the individual components of a drive (inverter, microcontroller, motor), communication interfaces to external systems, such as a plant controller, an industrial PC or directly to other drives, are also required. 

The most common way to connect drives to control units is via I/O connections or common networks for motion control applications such as IO-Link, EtherCAT, HART, SERCOS, Single Pair Ethernet and PROFINET. The network that is used depends on factors such as the application speed, the system complexity, real-time capability or the need for a highly synchronised movement over multiple axes.
 

Bus systems for drive solutions

Currently, the most common bus systems for motion applications are Ethernet, CANbus, RS485 and TSN (Time Sensitive Networks). In Europe, Profibus is also widely used. 

Ethernet offers data transfer rates of 10 MB/s to 1 gigabyte per second and is widely used, meaning that chips and hardware costs are low. Ethernet has been adapted for industrial applications such that the system is fast enough for the exacting requirements of industrial automation. These protocols, known as Industrial Ethernet, include Profinet, EtherCAT and Ethernet IP. Some of the drivers of growth in Industrial Ethernet systems are higher performance, larger data volumes, better real-time capability, the integration of safety protocols and access to office networks – making it easier, in turn, to connect to the Internet of Things and the cloud.

SERCOS has a unique role as a special real-time communication standard for sophisticated motion control applications. In contrast to EtherCAT, for example, it enables direct “cross-traffic”, i.e. direct real-time data exchange between any SERCOS devices. In this way, a servo drive can function as a virtual master and other drives follow it exactly (slave). 

CANbus was originally developed for the automotive industry. But today, due to its robustness and user friendliness, it is also a popular bus in devices for general industrial use and in drive technology. DeviceNet and CanOpen protocols are based on CANbus.

RS-485 and its “relatives” RS-422 and RS-232 are commonly used for communication between motion modules. Many of the “integrated all-in-one motors” on the market today use RS-485. What they lack in sophisticated protocols and automatic error checking, they more than make up for with their simplicity and low costs. RS-485 and similar serial buses are always used in the industry when performance demands are low and cost sensitivity is high.

 

Figure 1: Common bus systems for motion applications

 

Manipulation protection

With the connection of drives and their integration in cross-system communication structures, it is becoming more and more important to protect them from undesired access. That requires security measures on various levels, meaning drives should be integrated into a “Defence in Depth” strategy if necessary. Alongside the various possibilities to protect superordinate systems from unauthorised access, such as using firewalls, encrypting communication or reducing external communication interfaces, digital motor control systems themselves can also contribute to security: in this way, microcontrollers with the relevant security functions can be used. Hardware security modules (HSM) can be used to create a trusted environment for securely performing expected application. In HSM, cryptographic keys are generated and stored, which allows secure start-up, integrity checks, authentication and/or secure communication. HSM also improves protection against malware, unauthorised software updates, and software or data transfer manipulation.
 

Industrial Wireless networks

For less time-critical operations such as remote monitoring and simple on/off switching or speed control, wireless networks are increasingly used in industrial applications. Wireless M-Bus / OMS is leading the way in industrial environments. WiFi is also gaining some share in industrial applications, especially for accessing systems as an access port. When higher reliability is required and/or for access to remote assets, cellular connectivity technologies are used, such as LTE or possibly private LTE. In some applications such as advanced automation or robotics, 5G is gaining traction with its extreme reliability and low latency.

 

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