Sensorless monitoring of safety brakes

Whether in collaborating robots in industrial applications or automation systems in medical technology - there are numerous application fields for small, high-performance brakes. mayr power transmission offers for example reliable safety brakes with the ROBA-servostop construction series which are tailored to robotic requirements through their slim design and low weight. In addition, the company has a fluid-free linear brake in its portfolio with its ROBA-linearstop in electromagnetic design, which has been designed to secure gravity-loaded vertical axes. These brakes are used in applications in which compressors or units for compressed air or oil hydraulics are not available or are unwanted, such as in medical technology or the food or pharmaceutical industry, where high hygiene standards are required.

The ROBA-brake-checker module now opens up new possibilities for brake monitoring in these application fields. With a new module design and thanks to even more accurate evaluation, it is now possible to also supply and monitor small brake sizes from a braking torque of 0.7Nm. This makes the ROBA-linearstop not just the only electromagnetic rack and pinion brake on the market, but it also means it can be monitored even in small construction sizes with the aid of the module.

The intelligent ROBA-brake-checker module works without the use of sensors. Instead, it detects the movements of the armature disk by analysing voltage and current, and knows what condition the brake is in at all times. In addition to switching condition, temperature and wear, it also monitors the tension path or tensile force reserve, i.e. whether the magnet is still able to attract the armature disk. With the new module, substantially more processes can therefore be depicted during monitoring than when using microswitches and proximity switches. On reaching the tensile force reserve, the ROBA-brake-checker emits a warning signal early enough so that a certain operating time is still possible for the brake. During this time, the system operator or manufacturer can undertake maintenance in a targeted manner, aligned to their own working process.

Increased system availability

The ROBA-brake-checker works without mechanical contacts with high reliability and wear-free, independently of the cycle frequency. Andreas Merz, Product Manager at mayr power transmission in Mauerstetten explains: "As the module works without sensors, which means no microswitch or proximity sensor has to be attached to the outside of the brake for monitoring of the switching condition, basic construction safety brakes can also be used. In addition, the extra wiring and any sealing of switches and sensors which may be required dependent on the aspired level of protection are no longer necessary. Furthermore, the risk of cable breakage is also excluded."

In contrast to products with switches and sensors, which are exposed to impacts and vibrations due to their installation situation, the monitoring process with the ROBA-brake-checker is carried out from the control cabinet, i.e. from a protected environment. Failures due to icing up and error signals caused by contamination such as friction dust are thus ruled out. Due to the electrical switching of the ROBA-brake-checker module in the DC version, the system availability can also be increased, as critical sparks can no longer form on the switching contactor, which in conventional wiring may lead to contact consumption.

With its ROBA-brake-checker, mayr power transmission is the only company to have an intelligent system for the sensorless monitoring of electromagnetic brakes in its standard portfolio. Merz explains: "Users can integrate the module easily and quickly into machines and systems, without having to intervene with the "converter' or "control' components. In this way, they don't take any risks as they don't have to validate limit values and data themselves. We supply the ROBA-brake-checker ready for installation and test all values beforehand. For users, this means a plug-and-play solution, so to speak."

Reliable monitoring even in adverse ambient conditions

Merz emphasises: "The fact that brakes in standard design are used for monitoring with the ROBA-brake-checker not only offers advantages in terms of costs and delivery time, but also for example with regard to corrosion protection. This is because the brakes can be painted over easily, quickly and safely - for example, if the corrosion risk is very high and protective measures are required in compliance with the DIN EN ISO 12944 standard Protective Measures (C5), for example on wind power plants or on applications in the maritime sector. In general, the ROBA-brake-checker represents a cost-effective solution, especially for small quantities, and even existing systems can be retrofitted without any difficulties."

See Mayr power transmission and the ROBA-brake-checker at the Hanover Trade Fair 2019; the company will be in Hall 25 at Stand D30. Visit www.mayr.co.uk for more information.