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Adjustable Speed Drives

Safety via Slip Ring

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Safe Torque Off: Kollmorgen and Stemmann-Technik are developing a TÜV-certified solution1. Device with cable. The combination of Safe Torque Off and single-cable connection  technology enables streamlined installation with AKD-N servo drives from KOLLMORGEN arranged in a distributed setup.

Slip rings emerged at the same time as electric motors and generators. The operating principle, which involves sliding contacts on rotating circular conductors, is essentially fairly simple. Any issues relate to matters of detail, and these are the things that currently present the main challenge to developers – with regard, for example, to the growing role of safety technology in the field of engineering. For one thing, it is not that easy to transfer data, energy, air, or fluids from a static location to a component in constant rotation. The motion control experts at Kollmorgen have now managed, together with the slip ring manufacturer Stemmann-Technik, to develop a TÜV-certified safety solution – with UL approval – for this kind of thing.

Rotary indexing tables are a common piece of equipment used in an assembly and test stand context. Various work stations are arranged around an outer radius and take the component, held in a workpiece carrier, through another production stage with each indexing operation. If the workpieces on the rotating table still require rotational or linear positioning as well, the drives need to move as well. The job of slip ring systems is to transfer the power required for this along with the relevant control data. This is an established technology and works reliably well throughout a long service life. Things really get exciting, however, when this kind of slip ring is used to transfer safety-related data too. This was the task facing Kollmorgen as part of a project for a manufacturer of measurement inspection machines, with the aim being to investigate the behavior of crystalline components.

Benefits of distributed servo technology

The idea behind the engineering project was to install not only the actuators but also the controls on the rotary indexing table – adopting a distributed arrangement to save space. The Kollmorgen solution to this task was to use AKD-N servo drives, in a distributed setup, and compact AKM synchronous servo motors with high power density. The main benefits of the distributed setup and of having just one cable connecting drive and motor are small control cabinets and the fact that less space is required for installation purposes. In addition, the single cable connection technology, with the option to loop from drive to drive, also improved the inertia of the rotary indexing table. But it was still necessary to satisfy the safety technology requirements. This is integrated into the test station in the central AKD-C power supply module, which means a connection to the servo axes is required.

The Safe Torque Off (STO) feature was needed because the masses being moved – the rotary indexing table has a diameter of 120 cm after all – present a potential hazard to persons in the vicinity. The testing process does, however, envisage some operator intervention on the system, which ultimately implies Safe Torque Off as regards evaluating safety.

The central AKD-C power supply module does in fact feature STO as standard – albeit connected to clearly defined and certified cables. Using a slip ring as a connecting element between the central AKD-C power supply module and the AKD-N drives would inevitably mean disconnecting the cable, however, and invalidate certification. The same also applies to any existing UL approval. This too would no longer be effective.

Safety in the slip ring – with a certificate

As part of the joint engineering project with the test stand builder, Kollmorgen began to look for a suitable manufacturer of slip rings who would be willing and able, together with the servo drive and motion control specialists, to develop a safety slip ring with TÜV certification. The current solution, approved by TÜV Süd, is based on a slip ring from the Bako LP range from Stemmann-Technik. Compared with conventional slip rings, this transmission system (made in the German town of Schüttorf) offers a wide range of potential solutions for customized production – thanks to the numerous options available – along with UL approval.

The challenges associated the project included how to deal reliably, from a safety perspective, with the natural wear experienced by the contacts. In this regard, Stemmann-Technik would point out the reliable service life based on 35 million revolutions at maximum speeds of up to 80 rpm. Another challenging task was how to transmit safety signals reliably without interference. It should be noted here that the shielding integrated into the cables is no longer present in the slip ring. This then makes it necessary to find ways of preventing signaling errors caused by the coupling of interference signals.

Interference-resistant communication of signals

Kollmorgen and Stemmann-Technik are able to combat the familiar problems associated with EMC through two separate measures. From a design perspective, two shielded junction boxes in the safety slip ring interrupt the Ethercat communication supply via which the superimposed safety signal is transmitted. This ensures in particular that the magnetic influences from harmonics in the power wires do not cause any signal interference. The second aspect for ensuring high resistance to interference within the slip ring relates to the structure of the safety signals. Compared with the standard practice of arranging STO with 5 or 24 VDC signals, Kollmorgen uses AC signals with specific frequency patterns between the AKD-C, as the central module, and the distributed AKD-N servo drives.

In practice, this particular detail ensures that potential interference signals from the drive are completely ignored if they do not have the exact same frequency. This approach is therefore far more robust against interference – which ultimately, combined with the two separate junction boxes for power and signals, helped secure certification from TÜV Süd. Thanks to this equipment, engineering firms have the benefit of safely switching off the rotary indexing table without losing access to the positioning drives (which are also moving) for the workpiece carriers. Users also retain full access to all drives in the event of an emergency stop – which ultimately saves on time-consuming referencing as a result of undefined statuses.

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Adjustable Speed Drives

Continued market growth is testament to the development of PLCs

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The PLC versus IPC or PC based control debate has been with us for over two decades now, with commentators making various predictions about the rise of industrial controllers with PC based internals versus purely PLC solutions.  Yet according the latest figures from Gambica the PLC market continues to grow.

Mitsubishi Electric is heavily invested in PLC technology with a massive installed base and a continuous stream of innovations being released to the market.

Indeed, it is interesting as part of the PLC versus IPC debate to note that there has been some blurring of the technologies, with each now incorporating some of the features of the other. From the PLC perspective, this includes everything from the inclusion of embedded web servers to the availability of plug-in PC modules such as Mitsubishi Electric’s C-Controller. Other modules, such as Mitsubishi Electric’s MES module, mean that PLCs can now link directly to higher level systems without the need for intermediate PC hardware. Furthermore, the combination of PLCs and HMIs means that PLC platforms can also provide a very PC-like environment for SCADA and other visualisation applications.

The latest generation of PLCs are also offering broader functionality such as embedded robot controllers with the related safety systems and aspects of AI that allow for flexible learning and intelligent decision making. Users are thus free to look at the most appropriate solution for a given application rather than being forced along either one route or the other because certain vital features and functions are missing. Even here it is interesting that the appeal of the PLC often endures and for many users there remain good reasons to stick with a purely PLC orientated approach.

Part of that comes from the proven reliability of PLCs in applications where it is not uncommon for users to expect assets to deliver for a decade or more, with no pressing requirement to constantly upgrade control and automation systems. When the user does eventually want to upgrade to a new control platform, the PLC offers an inherently easier migration path than the IPC solution.

Perhaps more important to the user / operator is the requirement in many of those same applications for longevity of support. In the water industry, for example, AMP periods of typically 5 years mean that system integrators want to be assured of complete product stability, so that they can replace products like-for-like with minimal engineering overhead.

Now, system integrators in other areas of the utility and transport infrastructure are reporting that customers are calling for even longer product lifetime support, with even 15 years becoming common. Because PCs evolve and transform over much shorter product cycles than PLCs, they will often be much more of a challenge to support over the longer term, even if at the specification stage they might have tangible advantages over traditional PLC-based alternatives.

The feedback from system integrators and machine builders on the PLC versus IPC debate has also been interesting when it comes to their own development efforts, particularly in applications where, on paper, either approach would yield a good solution. For example, machine builders producing serial volumes of the same machine often feel the IPC route could be convenient for them. In contrast, machine builders and systems integrators who are adapting or customising individual machines to meet different requirements frequently report that they find it easier to configure PLCs to meet those differing user needs.

There are many other reasons why the appeal of the PLC endures. The issue of cyber security continues to grow, and many users are still reticent to put what they see as more vulnerable PC hardware into critical automation systems. Perhaps that view is unfair – there have, after all, been a number of high profile cyber attacks and viruses targeting PLCs. There exists a perception maybe, that the bespoke operating environment of the PLC offers protection through unfamiliarity rather than the standard operating systems of PC based control, however, it would be naïve to think that ‘security through obscurity’ would deter a determined hacker with the correct backing.

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Adjustable Speed Drives

Emission-Free Sweeping

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Baumüller has developed a compact drive system for a multifunctional municipal vehicle.

Baumüller has developed a compact drive system with a very high level of energy efficiency for a fully electric municipal vehicle. The vehicle is designed in series production for a speed of up to 80 km/h and has a range of 100 kilometers. An emission-free, environmentally-friendly and low-noise multifunctional municipal vehicle has been created in conjunction with other companies. It can be used with interchangeable attachments for various municipal cleaning and maintenance work, for example as a sweeper, snow plow or loader.

The joint development with the companies Cosyst Control Systems GmbH, bLz – Bayerisches

Laserzentrum GmbH, Polyplast Sander GmbH and SMS Engineering GmbH was supported as a funded project by the Bavarian State Ministry of Economic Affairs and Media, Energy and Technology. The project sponsor is Bayern Innovativ.

Electric Axle for Rear and All-Wheel Drive

The compact drive system from Baumüller consists of two fully electric drives, each of which is mounted to the vehicle’s rear axle. Alternatively, an all-wheel drive can also be used instead of a rear-wheel drive. The drive system consists of a Baumüller DSA synchronous external rotor motor with an integrated converter, power electronics as well as a planetary gear and was specifically developed for this funded project. The planetary gear is located in the rim of the rear wheel and is directly connected to the drive system. This has the advantage that there are fewer transmission losses, since an additional drive train, such as a cardan shaft, drive shaft or differential, is not necessary. Additional advantages of the compact drive system are increased application flexibility and improved driving comfort. In addition, the drive is very capable of handling overload, i.e. gradients of up to 18 percent can easily be managed.

The special feature about the rugged newly designed DSA motor with a rated output of 18 kW is the winding switchover. This allows an automatic gear change of the municipal vehicle from a working gear to a high-speed gear. The switchover makes it possible to achieve different torques and speeds, which are automatically adjusted to the application area and speed via the motor controller developed by Baumüller. This means that in the first stage, the working gear, i.e. when sweeping or mowing, a doubled rated torque is achieved at only half the speed. This level is used for speeds of 40 km/h or less. The energy source is not burdened with large currents here, which allows for a greater range and a longer operating duration than before. With the second stage, the high-speed gear that permits speeds of up to 80 km/h, a simple rated torque is generated and the full speed is reached in the process. Despite the higher speed, the power requirement still corresponds to that of the first stage. The degree of efficiency also remains very high, thus allowing for greater range and a longer operating duration.

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Adjustable Speed Drives

BAUMÜLLER, Intelligent Diagnostic and Communication System

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BAUMÜLLER, Intelligent Diagnostic and Communication System

Fotoğraf Açıklama: Archiving and evaluating data can take place locally or remotely with BAUDIS IoT. Smart data analysis is used to avoid production errors and to increase productivity, all automatically through a self-regulating machine learning process

Baumüller Demonstrates Predictive Maintenance System with Smart Data Analysis

With BAUDIS IoT, the Nuremberg-based drive and automatization specialist Baumüller presented a system for predictive maintenance at SPS 2016. But BAUDIS IoT can do much more than that. It is the consistent enhancement of the BAUDIS diagnostic system developed by Baumüller, which has successfully been in use for more than 20 years. BAUDIS increases the process reliability and availability of production and is successfully used worldwide in machines and plants.

BAUDIS IoT, the latest version, is an IoT-capable diagnostic and communication system that allows for a simple networking of machines and systems via the Internet and the intelligent analysis of data. The networked version benefits from the long-standing expertise of a successful system. The system can be used independently of the manufacturer of the automation components and the sensors and therefore can easily be retrofitted and upgraded. It is therefore equally suitable for greenfield and brownfield plants, i.e. for the digitization of new and existing production facilities.

Two Versions for Data Archiving and Evaluation

In principle, two versions for linking machines and systems are available. If the decision favors the local version, the data recorded on the drive will be evaluated directly by the operator on site. If the remote option is preferred, the data is uploaded to the cloud and is archived and analyzed either centrally at the customer’s location or externally at a service provider’s location for example. The benefits of the second version: The networking of plants and locations in the cloud or via a central server, i.e. an evaluation unit, allows for additional comparisons and evaluations. In addition, the updates can occur centrally. Externally, the evaluation always occurs with the latest available algorithms.

BAUDIS IoT from Baumüller allows for the continuous monitoring of automation components and machine states, data recording and analysis and the generation and output of a recommendation for action. The evaluation always occurs with the latest available algorithms. The system is thus continuously made more intelligent and uses algorithms to develop independent solutions (machine learning). By avoiding production errors, productivity increases and does so automatically through a self-regulating process. BAUDIS IoT can be used and upgraded at any time independent of the manufacturer and the sensors used.

Smart Data Analysis Saves Time and Money

Industry 4.0 applications create countless opportunities to improve machines, optimize drives, increase availability and make service more efficient. BAUDIS IoT is an industry 4.0 technology solution and provides for an intelligent networking of systems. With BAUDIS IoT, machine operators have an ideal system available to them in order to monitor their production and, in the event of a looming failure, to be able to act or react quickly or in a timely manner, thus increasing the running times of the machines and systems by means of scheduled maintenance measures. This saves time and money and improves the machine availability as well as the productivity. For the machine manufacturer, BAUDIS IoT is a good way to offer the system as an option and thus to create added value for his customers. Baumüller can completely take over the installation, monitoring and maintenance of the BAUDIS IoT system if desired.

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