Incremental Encoder Based Position and Speed Identification: Modeling and Simulation

Electrical drives frequently use incremental encoders as position sensor. The paper deals with the modeling and simulation of an incremental encoder and associated units for processing the information provided by the encoder. A mathematical model of the incremental encoder is presented. Based on encoder signals the direction of the rotation, the position and the speed are identified. The described procedure for determination of the direction of the rotation is able to identify the direction changing in all cases during a rotation equal to the minimal detectable rotation-angle-increment. The computing of the position is based on the algebraic summing of the number of the generated encoder signals. For the speed determination different methods are modeled and simulated: for high speed region the frequency measurement is used and for low speed domain the period measurement is appropriate. In case of a large speed variation the minimal-error-based switching between the two methods is suitable. Matlab-Simulink simulation structures were realized for the encoder signals based on the identification of the direction of the rotation, for the position and speed computation. Experimental results performed on a DSP-based set-up (under development) are given. The presented simulation subsystems of the encoder, position and speed computation may be integrated in any Matlab-Simulink structure.