Encoder self-callibration apparatus and method

Abstract

The disclosed electronic processing apparatus calculates and applies calibrations to sensors that produce quasi-sinusoidal, quadrature signals. The apparatus includes either or both of fixed and programmable electronic circuits. The apparatus includes a circuit to calculate the phase and magnitude corresponding to the two input (quadrature) signals. The apparatus also includes a circuit for accumulating the number of cycles of the input signals. The apparatus also includes a circuit to generate Gain, Offset, and Phase calibration coefficients, wherein the circuit compares the phase space position of the measured phasor with the position of an idealized phasor, the locus of the idealized phasor in phase space being a circle of predetermined radius with no offset. The calculation of the coefficients occurs without user intervention, according to a pre-programmed rule or rules. The apparatus also includes a circuit to apply the Gain, Offset, and Phase calibration coefficients to the measured quadrature signals xand yaccording to the formulae=()×=()×where Gxand Gyare the scaling coefficients, Oxand Oyare the offset coefficients and Pis the phase coefficient and where Xand Yare the post-calibration quadrature signals. The apparatus also includes a circuit that creates an output signal representative of the current, calibrated phase. The output signal is either a parallel, digital word or one or more serial pulse trains wherein the total number of pulses produced over time corresponds to the total phase change in the measured signal. The output signal is coded to allow phase decreases as well as phase increases.