Patent ID: 7400993

Claim:
A method for calculating rotation-dependent parameters in a system that senses multiple teeth during a single shaft rotation of a toothed speed wheel, the method comprising: sensing passing edges of multiple gear teeth on the toothed speed wheel; generating a signal pulse at one of rising and falling edges of the gear teeth; measuring time between the generated signal pulses; calculating a tooth correction for the span between at least one of rising and falling edges of successive gear teeth according to: Correction ⁢ [ ti ] = TICS ⁡ [ t n ] - TICS ⁡ [ t n - 1 ] ∑ k = 0 N - 1 ⁢ ⁢ TICS ⁡ [ t n - k ] ; and applying the tooth correction to the rotation-dependent parameter calculation according to: Freq ⁡ ( Hz ) = 1 ( TICS ⁡ [ t n ] - TICS ⁡ [ t n - 1 ] ) / 25000000 ⁢ ( Teeth Sec ) * ( tooth ⁢ ⁢ correction ⁡ [ ti ] ) * [ Teeth rev ] Speed 1 = 1 ( TICS ⁡ [ t n ] - TICS ⁡ [ t n - 1 ] ) / 25000000 ⁢ ( Teeth Sec ) * ( tooth ⁢ ⁢ correction ⁡ [ ti ] ) * [ Teeth rev ] Speed 0 = 1 ( TICS ⁡ [ t n - 1 ] - TICS ⁡ [ t n - 2 ] ) / 25000000 ⁢ ( Teeth Sec ) * ( tooth ⁢ ⁢ correction ⁡ [ ti - 1 ] ) * [ Teeth rev ] Acceleration ⁢ ⁢ ( Hz Sec ) = Speed 1 - Speed 0 ( TICS t n - TICS t n - 2 ) / 25000000 ⁢ ( Teeth Sec 2 ) where TICS represents circular buffer elements storing counter values associated with pulses, N represents the number of teeth on the speed wheel, t n represents a pointer to the latest TIC entry in a circular buffer, t n−1 is the pointer one entry back from t n , t n−k is the pointer k entries back from t n , [ti] represents t n , Modulus N, and tooth correction [ti] represents the tooth correction associated with an individual span.