11.1.1 Rate Limiter Theory

The rate of change of output remains within the specified limit whether the output is increasing or decreasing with respect to time. The output slope is configured by two parameters—rate count and slew count. See the following figures.

Note:
  • Rate count = Value with which output is incremented or decremented after every slew count.
  • Slew count = Wait period in number of start signals after which the output is updated.
Figure 11-2. Acceleration
Figure 11-3. Deceleration

The Rate Limiter IP also has a reset ramp input, which forces the output to zero instantaneously irrespective of the input value. This feature is useful for auto-restart in the motor control application to initialize speed reference output from the Rate Limiter IP to zero before starting motor again.

The soft stop input forces the output to zero irrespective of the input value. However, the output goes towards zero according to the ramp profile configured by slew count and rate count. Direction input is used to negate the input. This is generally related to changing direction of motor rotation.