Fault-Tolerant Rotary Gray Encoder for Industrial Applications

Motors are extensively used in factory automation. A correct determination of the motor shaft position is crucial for the success of any process. Rotary Gray encoders are often used to determine motor shaft position because of the reliability of their readings. In this paper, two error detection and masking mechanisms are developed to ensure the correctness of the data produced by the encoder for applications requiring either a small number of codewords or a larger number of codewords. These mechanisms rely on analyzing data from three identical encoders, such that the correct reading is produced even if one of the encoders fails and outputs a non-codeword or an incorrect codeword. Both mechanisms are validated on the Intel Cyclone IV E EP4CE22F17C6 FPGA, where exhaustive testing was carried out successfully to prove their error detection and masking capabilities.