Consider a quadrature encoder with 2 optical sensors located on it ( quadrature
ID: 2084220 • Letter: C
Question
Consider a quadrature encoder with 2 optical sensors located on it ( quadrature encoder with 2 optical sensors shown in the figure a ). That has the advantages like determining the position over the 1 sensor one.Now, what if there was 3 optical sensors( A, B, C) (quadrature encoder with 3 optical sensors shown in the figure b) instead of 2 ( A,B), what would be the advantages and drawbacks of this system? How would you determine the position and angular velocity of the rotatry system? ( explain your path briefly)
shaft rotating codewheel shaft rotating codewheel. (a) (a) (b) (b)Explanation / Answer
1. Position of the disc:
The encoder with 3 sensors is an incremental encoder. So, by counting the rising edges on all the three sensors and later dividing by the total pulses in a revolution we can determine the position of the disk.
2. Angular velocity:
By measuring the time difference between the rising edges of the sensor outputs. We can determine the angular velocity as the difference between the sensor position is constant and known.
The direction of rotation can also be determined from the phase difference between the three sensor outputs. The resolution of the measurements shall alao be improved with the 3 sensor system.
The drawback can be the limitation of measurements at higher speeds. This is due to the fact that the controller should be able to process all the three interrupts within the small time window available at high speeds.
Let me know your feedback on the same.
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