Incremental Rotary Shaft Encoding Technique Providing Direct Coarse Angle and Absolute Sub-Angle Determinations
Original Publication Date: 1988-Sep-01
Included in the Prior Art Database: 2005-Feb-15
Optical incremental rotary shaft encoders for use on direct drive robots are known. In [*], it is shown how to subdivide an optical slot encoder such that velocities and, hence, subangles finer than the angles provided by the slots may be obtained. Division of each slot into many subangles is obtained by disposing a phase plate in front of four photodetectors to provide four quadrature outputs that are sequentially sampled, summed, and filtered to provide a sine wave of a given frequency. The sine wave is then squared and compared to the basic sampling rate.