This method is sometimes called "dry cleaning", which is a misnomer, since water is used.
Bonnet Pad Cleaning is simply an adaptation of hard floor spray buffing to carpets.
This method for carpet maintenance consists of the use of a rotary or oscillating brush adapted with a stiff brush or drive block designed to drive wet, damp or dry pads. The carpet can be sprayed with the cleaning solution and/or the pads can be soaked in the cleaning solution and squeezed lightly before placing the pad under the driving brush.
The maintenance brochure published by the world's largest carpet manufacturer, Shaw Industries, suggests NOT using this method, especially on cut pile, due to pile distortion and fiber damage. This method has very limited capability for soil removal and leaves much of the detergent in the pile since it employs no real extraction. As a result, rapid re-soiling often occurs. Another disadvantage is that the spinning bonnet may distort the fibers of cut pile carpet, fuzzing the pile and leaving distinct swirl marks.
Sometimes, carbonated water is used to (in theory) give better soil suspension and bring down the pH. Companies using this method frequently use "scare" tactics to convince consumers that extraction cleaning or steam cleaning will destroy the carpet.
Check with your carpet manufacturer because many leading carpet mills recommend against this method of cleaning.