System Examination: Motion Monitoring

Motion monitoring has two main tasks: it must detect any violation of the limit values and then trigger an appropriate reaction function. It must also detect any potential errors on the encoder system and likewise trigger an appropriate error reaction function. Both functions are heavily linked to the availability of the drive system. Noisy signals or poorly tuned control loops can cause sensitive monitoring mechanisms to trigger reaction functions and therefore reduce plant availability. Proper screening of the motor and encoder cables is absolutely essential. The algorithms for the monitoring functions can be applied via hysteresis or filter settings. The reaction times for these components are in the millisecond range. Motion monitoring is available as both an external and a drive-integrated solution. An integrated solution has clear advantages over an external device in terms of wiring effort and convenience. Disadvantages are higher retrofitting costs for existing plants and dependence on the converter that is used. This means that the technical properties of the drive, as well as the interfaces and the performance of the safety functions, have to fi t the application. With an external monitoring unit, safety functions can be implemented as standard on frequency converters and servo amplifiers of a different performance class or manufacturer.