#Product Trends
Safe speed monitoring with safety encoders
Measuring speeds is an increasingly important requirement in machines and systems. They are used to reach certain positions quickly and safely.
Measuring speeds is an increasingly important requirement in machines and systems. They are used to reach certain positions quickly and safely. The drives are precisely controlled. It is usually possible to travel quickly between the end points - for example, in the case of a crane. When the target point is approaching, the speed is reduced. Servo drives with integrated sensors can perform this task. In many cases, however, a separate encoder must be used. Especially when it comes to safety-oriented applications in which additional position and speed detection by functionally safe sensors is required. It serves to protect the environment, people and machines.
In many cases, for example, the speed of automated guided vehicles (AGVs) is measured directly at the wheels in order to meet safety requirements. In addition to the control aspect, there is also the important task of speed monitoring, e.g. for the rotor of a wind turbine. Here, it must be ensured that a certain speed is not exceeded. If it does, the turbine must be switched off - or at least an alarm must be triggered. In other words, the requirements for a reliable output signal are high.
TWK has been active in the field of sensor technology for machines and plants for a long time and has been offering functionally safe and robust sensors for years. These are mainly rotary encoders, electronic cam switches and inclination sensors, including a special version, the rotor hub sensor. What they all have in common is that they are certified according to ISO 13849 as well as IEC 61508 - with level PLd or SIL2. Depending on the product, various flange and shaft shapes as well as stainless steel versions are available. In terms of encoders, there are several new releases from TWK. Some of them have features that are not yet available on the market.
For example, the ultra-compact TRK38/S3 multiturn safety encoder has been launched. It has a diameter and housing length of only 38 mm. With the Fail-Safe-over-EtherCAT interface (FSoE), it offers full SIL2/PLd performance with a resolution of up to 16 bits/360°. The quality of the speed signal has been significantly improved: the accuracy of the position detection on the time scale is now approx. 1 µs. This equidistance is important for precise speed, which is based on the calculation of the position difference per time unit (adjustable).
But also with regard to classic encoders with CANopen-safety interface, TWK has a certified encoder with safe position and speed signal in its portfolio with the new TRN/S4.
Finally, the established PROFIsafe via PROFINET encoder TRT/S3 will soon be launched in an updated version. The experience and ideas of recent years have been incorporated into the hardware and software - e.g. the encoder profile 4.2 known from the drive sector.
With the help of these devices, a functionally safe detection/monitoring of the speed in the most diverse variations can be easily realised in order to make machines and systems safer.
