Internal velocity filters

Application of the Velocity Observer! Above a frequency of 300 Hz noise can become problematic. First and second-order filters are often ineffective in this case. The Velocity Observer of the AX5000 servo drive provides the velocity controller with a speed signal available without resonance-induced oscillations over the widest possible frequency range. It is available in FW v2.06 in Basic mode (third order) and in FW v2.10 in Advanced mode (fifth order). Further information can be found in chapter: „Velocity Observer“ of this function manual.

The control quality describes the capacity of the drive system to follow the setpoint values highly dynamically, with low losses and fail-safe. The control quality depends on many factors. On the mechanical side these could be soft drive trains with belt drive, or resonance points caused by the natural ageing of components or special features of the mechanical structure. Without the use of filters the only possibility is to reduce the loop gain and to adapt it to the worst condition. However, this adaptation affects the total application and lowers the dynamics of the drive system. The application and the parameterization of the internal speed and current filters act, for example, specifically on a resonant frequency, hence allowing a high loop gain and thus a highly dynamic drive system. The filters described here serve to eliminate or attenuate unwanted noise or resonant frequencies. The main control loops of a servo drive are the position controller, the velocity controller and the current controller. With the exception of the position controller, software filters can be inserted before the controllers. The characteristic of these special software filters is realized by means of a 1st and 2nd order IIR filter with time-discrete transfer function.