Embodiments of the present invention are directed to a controller that is configured to limit the rate of change of speed of a motor (e.g., the acceleration or deceleration) regardless of the operating mode of the motor (e.g., speed, torque, or power control mode). The controller can include an acceleration estimator which monitors the output speed of a motor and provides an acceleration-limited speed set point. The output of the acceleration estimator may be limited to a range of acceptable acceleration values that correspond to the required limits of acceleration and deceleration. The acceleration estimator can be configured such that it causes the speed regulator to override the torque and/or power regulators when the acceleration range is exceeded.