Precision Three-Point Digital Velocity Measurements
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
The Taylor's series is used to construct a 3-point derivative. This 3-point derivative uses the standard 2-point velocity measurements obtained from a standard digital encoder (tachometer). These 2-point measurements are combined without special arithmetic. Only a unit delay, a subtract, a bit-shift (divide by two), and an add are necessary to construct an accurate 3-point velocity measurement. The 2-point derivative is incapable of taking into account acceleration. Thus, large errors in amplitude result when the 2-point velocity measurement is used when acceleration is present. The 3-point system compensates for effects of acceleration. Also, the 3-point velocity measurement technique does not have large errors in phase found in the 2-point measurement system.