Capacitive Motor Feedback System

DAYTON, OH – SICK STEGMANN, INC. introduces SEK/SEL37 Capacitive Motor Feedback Systems. Just 36mm in diameter, these compact motor feedback systems with HIPERFACE® interface are available in singleturn and multiturn versions with a radial or axial plug outlet. The capacitive principle of operation is not only very accurate but also extremely robust, requiring no ball bearings. As a result, SEK/SEL37 motor feedback systems offer temperature resistance previously only found in resolvers.

As is common with ultra-compact motor feedback systems, SEK/SEL37 motor feedback systems are designed for mounting directly onto tapered shafts. Holistic scanning almost fully compensates for eccentricity errors, with possible error sources having been practically eliminated by removing wear and tear parts. The SEK/SEL37 provide 16 sine/cosine periods, resolution of 512 steps per revolution, and 1 (singleturn) or 4096 (multiturn) steps per rev. They are rated for shock resistance to 100 g/10 ms, vibration resistance to 50 g/10 … 2000 Hz, and provide reliable operation in temperatures ranging from -40…+115°C (singleturn) or -20 …+115°C (multiturn).

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SEK/SEL37 capacitive motor feedback systems are an ideal alternative in applications currently using resolvers, but where users need higher performance, final positioning such as servo motors, handling drives, feed axis or standard robot applications. They are also well suited for use in traditional motor feedback applications that demand higher than normal robustness for reliable operation in high temperature and vibration environments common in textile machinery and mining applications, for example.

The multiturn properties of the SEL versions are implemented using a mechanical gearbox in combination with magnets and Hall sensors, achieving absolute, non-volatile code and position determination. A crucial advantage over resolvers is that no external evaluation unit is required – all electronics are contained within an integrated ASIC.

Thanks to HIPERFACE, all popular servodrives have an interface standard that covers all applications needing only one type of signal line. Another advantage is the possibility of self-initialization and automatic controller parametrization of the drive system by using an electronic type label, as with the SEK/SEL motor feedback systems. Motor characteristics, serial and part numbers as well as further data which quickly help in case of service or exchange are written here. These can be used to independently adjust the controller to the parameters of the motor.

HIPERFACE is an eight wire interface standard that makes it possible to get commutation, speed regulation and position information from a single device. The physical interface includes two wires for an RS485 link, four wires for sine & cosine signals and two wires for the power supply; a reduction from as many as 19 leads in a traditional system.

HIPERFACE compatible motor feedback systems combine the functions of both incremental and absolute encoders. The absolute value in these systems is calculated when the device is initially turned on, and is then transmitted via the RS-485 interface to a counter in the drive. The drive uses this initial absolute value for the commutation of the motor and also as a pointer to identify the exact period of the sine/cosine signals that the drive is currently evaluating. The drive then increases the base resolution of the sine/cosine signal by interpolating these signals in the drive with an A/D converter.