kubler articles

Future-Proof Motor Feedback Systems

Kubler 11/1/2017

Future-Proof Motor Feedback SystemsCompactness, efficiency and performance are the omnipresent requirements of the machinery and plant engineering industry. This applies to the drives technology too. With its new motor feedback systems, Kubler offers drive manufacturers a futureproof and flexible sensor solution. They are based on a platform that allows reducing the number of motor variants and standardizing the mechanical installation and covers a wide range of electrical interfaces. 
 
Companies today strongly invest in research and development in order to be able to offer in the future optimal solutions for the IIoT. One of their goals is to shape the future with new technologies for digitization and networking. Machinery and plant operators increasingly demand preventive maintenance by means of intelligent data analysis. This will allow them increasing further the availability and reliability of their production plants. Intelligent sensors allow fast error diagnosis, which contributes to the reduction of unscheduled downtimes and production outages. The drive manufacturers confront this task with the development of smart motor concepts. 
 
Trends in drive technology

The communication between a motor feedback system and the drive controller can be a decisive factor for the performance of the drive system. This applies in particular in case of dynamic axes, smooth speed control and high positioning accuracy.

So far, the choice of the components was often imposed by the proprietary interfaces and not by the requirements placed on the application. This is now counteracted by the trend according to which drive manufacturers are increasingly following a second-source strategy in order to minimize costs and risks. In parallel, manufacturers are opening their hitherto proprietary interfaces, leading to higher flexibility and an improved costs structure. The single-cable solution is another trend in the electrical drive technology. It allows further cost savings and at the same time simplifies the drive system, thus also offering benefits to the user. 
 
New motor feedback systems family

Kubler is now reacting to these trends with a new motor feedback systems family: it was developed in close cooperative partnership with well-known servomotor (Picture 2) and converter manufacturers. It is based on a specific platform that offers various possibilities and advantages for servomotors. The particular feature of the new Sendix S36 MotorLine encoders (Picture 1) is their compact size of only 36.5 mm for a maximum resolution of 2048 pulses per revolution or 24 bits fully digital. One single size allows realizing several power ranges which, until now, required at least two different encoder sizes of for example 36 mm and 58 mm.

The mechanical connection between motor and encoder is independent of the required performance range. Previous motors using a 58 mm-size encoder can now be designed in a more compact way using the Sendix S36 Motor-Line. A tapered or a blind hollow shaft and various torque stops are available for standardization. This ensures the drive manufacturer more flexibility when selecting the mechanical connection.

The choice is also broader in terms of functional safety. According to his choice for a tapered or for a blind hollow shaft, the drive manufacturer can select freely his preferred mechanical connection for his safety concept. Thanks to the platform concept, the Sendix-S36-MotorLine encoders can offer the following interfaces: RS-485 + sin/cos, Biss, Biss Safety, Biss Line (single-cable solution) and "SCS open Link" (single-cable solution). Thanks to this wide choice of interfaces, the electrical interface is no longer the limiting factor. Servomotors are also used in applications where they are subjected to high requirements in terms of shocks and vibrations.
 
The three market players see themselves as the initiators of a growing community that supports the establishment of an open-source interface standard. The goal is to ensure in the future higher flexibility to the drive manufacturers when choosing the suitable encoder for their application. A neutral certification body will guarantee the compatibility of the devices from different manufacturers.

"We feel in the servo drives market a strong demand for compatible motor feedback systems, more flexibility and a future-proof, non-proprietary standard. Summarized, there is an urgent desire for an open, safe single-cable solution. We meet these requirements with the new "SCS open link" interface. In addition, we durably meet the market trends relating to increasing performance and functional safety" said Gebhard F. Kubler, Managing Director of the Kubler Group at a press conference during the Motek fair on October 10 in Stuttgart.

"SCS" means Single Cable Solution. "A high-performance single-cable solution realized with two wires" describes G. Kubler, who continues: "open means a non-proprietary, open-source interface that promises to become a proven certified standard. And 'link' emphasizes the meaning as a motion protocol for the connection between a rotary or linear motor feedback encoder and the drive controller."

Moreover, the high significance of safety has been documented by the suitability of this interface for applications up to SIL3/PLe. To illustrate the future-proofness of this new solution, he mentioned the possibilities of condition monitoring and of the connection of further secondary sensors. IIoT scenarios can therefore be realized already today. This new interface also stands out by a transparent license model that ensures the openness also towards further providers.

Jochen Feiler, Manager of Hengstler GmbH, presented the technical particularities of "SCS open link" and the corresponding customer benefits. He first answered the question: How open is open? "Focus has actually been set on a future-proof and clear regulation of the rights of use and on the fact that the three founder members are basically favorable to the extension of the sensor manufacturers circle." But it is obvious too that the community has been launched from the customer's perspective. "The marked clearly indicated us that an additional closed interface is not desired," said J. Feiler.

Besides, he emphasized the advantages of "SCS open link" for drive and machinery manufacturers: "The high flexibility thanks to offers from different encoder manufacturers and the easy implementation of 'SCS open link' based on a micro controller, which ensures high innovative drive both on machine and on motor level, are a central feature". J. Feiler also recalls that the new interface is based on the Acuro link interface developed by Hengstler and is entirely backward compatible with it.

Karsten Just, Sales and Marketing Manager of Baumer Group, also emphasized: "The union of three renowned encoder manufacturers is an absolute novelty, which sets the focus on the meaning of the term community. All relevant information about this interface is available on a common web site (www.scs-open-link.org). This web site is the contact point for interested users as well as for further potential licensees. The offer of 'SCS open link'-capable sensors and the market development are driven ahead by every single member. Therefore, all three founder members will present individual products and solution approaches at the coming SPS IPC Drives fair in Nuremberg." K. Just announced following the press conference a small in-house exhibition. Many connector and cable manufacturers already belonging to the "SCS open link" community network presented themselves there: the companies Helukabel, Igus, Lapp, Phoenix Contact, SAB Bröckskes, TecniKabel und TE Connectivity. 
 
New single-cable solution

Cables and connectors belong to the main cost drivers in every automation architecture. A single-cable solution allows saving material costs, installation work and, last but not least, space (Picture 3). This solution allows realizing both voltage supply and data transmission though one single cable. This is decisive above all for servomotors in the 40 mm-size. The tight mounting space in servomotors requires generally compact sensors and optimized connection possibilities for the assembly. With "SCS open link", Kubler now offers a new single-cable solution. It supports 2 and 4-wire applications and allows cable lengths reaching 100 m, transmission rates up to 10 MBaud and controller cycles up to 32 KHz.

The protocol is certified up to SIL3 and category 3 for functional safety. A neutral certification body ensures the compatibility of the devices from different manufacturers. But not only the reduction of the costs related to the connector, the cable and the integration makes the singlecable solution so interesting. Space for routing cables is often limited in the applications. The advantages are thus obvious: Simplification of the connection technology and less components. 
 
Smart Motor

Besides the usual information such as position and speed, the new motor feedback systems provide additional information. They will in the future provide also functions such as the electronic data sheet (EDS), saving customerspecific user data and condition monitoring for monitoring machine condition. Moreover, connecting additional sensors such as e.g. temperature sensors used for measuring the winding temperature is possible. The sensor data is transmitted to the servo inverter via the fully digital protocol of the single-cable technology. According to Kubler, the Sendix S36 Motor-Line encoders with single-cable solution are ideally equipped for the requirements of IIoT and of the smart motor.