Patent ID: 7838781

Claim:
A method of determining a mass of an item being accelerated by a rotating apparatus including opposed rollers capturing and accelerating the item, the method comprising: determining a base inertia of the rotating apparatus prior to capturing the item; determining an inertia of the rotating apparatus plus the item; determining an inertia of the item by subtracting the base inertia from the inertia of the rotating apparatus plus the item to determine an inertia difference; and determining the mass of the item according to a formula ΔI=½Mr 2 , where ΔI is the inertia difference, M the mass of the item, and r is a radius of a driven one of the opposed rollers; further comprising determining either of the base inertia or the inertia of the rotating apparatus plus the item by: determining a ramping torque value and a corresponding changing velocity of the rotating apparatus over a period of time; determining an average τ of the ramping torque value over the period of time; determining an average acceleration a of the rotating apparatus over the period of time; and determining inertia as τ/α.