group size sliding average if the group size sliding average is less than flow_control_group_size_sliding_average_limit_lower the following steps are performed if opening the gate will exceed the ugl then attempt vibration before opening the gate further then transition to active vibration otherwise increase the gate position if the group size sliding average is greater than flow_control_group_size_sliding_average_limit_upper the gate position is decreased in the active vibration mode if vibration resulted in bringing the group size sliding average within range then the system returns to the active metering mode else vibration did not result in increased group size sliding average and the gate position is increased as pills pass through aperture 105 they enter transport tube 107 inside transport tube 107 is located a rotatable helical spiral 202 as shown in fig1 a 12 f rotation of spiral 202 transports pills up and through transport tube 107 and at the same time singulates them singulation means that pills are caused to move in single file for purposes of this discussion the process of moving pills through transport tube 107 is referred to as u201c primary singulation u201d and is described in greater detail hereinbelow with respect to fig1 the rotation of helical spiral 202 fig1 a 12 c is controlled by transport tube drive 108 in the preferred embodiment transport tube drive 108 consists of a transport tube motor 121 that drives a belt 150 coupled by means of pulleys 135 to helical spiral 202 thus rotation of tube motor 121 results.