Incremental Encoder Interface With Fault Detection
Original Publication Date: 1988-Sep-01
Included in the Prior Art Database: 2005-Feb-15
This article describes a circuit arrangement for detecting failures in the position feedback circuitry of a robot or tool controller. An incremental encoder conveys positional information of a motor shaft by the use of two electrical signals. These signals are square waves and are approximately 90 degrees out of phase. By sampling these lines, encoder interface hardware can determine change in motor shaft position by the changes in the states of the two signal lines. Fig. 1 shows typical signals output by an incremental encoder. The circuit arrangement disclosed herein solves the problem of detecting hardware failures in the receiving of the signal lines which may look to the counter circuitry as normal signals. (Image Omitted) Position encoders may be purchased with many different types of signal interfaces.