Encoder Accuracy?

I’m working on an autonomous challenge program and i want to know if anybody has any experience with using the encoders for directing the robot. Do they give accurate enough feedback to send a bot accross the field and still center up correctly on a goal? Is it a necessity to gear up the encoder so it has a higher resolution than the number of wheel rotations? Ive never done much programming with these before and what i have done in the past with programming by time was a joke if i was covering any distance and needed accuracy.

I’ve found the encoders provide reasonable accuracy and usually aren’t the biggest problem in trying to navigate by dead reckoning. The worst errors in trying to navigate with encoders are usually slop in wheels/axle/bearing/gear train connections. The farther removed from the wheels your encoder is (through gears, chains, etc.) the more slop will be introduced but we have seen a noticeable amount even when directly connected to the drive wheel axles. Over-run can also be a big issue. Given these other causes of error, I find the encoders to be completely adequate for the task.

On this page, you will learn that the encoders output 90 pulses per revolution.

On this page, you learn that the largest VEX wheel is 5" in diameter.

Therefore, the resolution without gearing is (5 * PI) / 90 = 0.1745 inches per count.

If you need more accuracy, gear it down…



I am not a very big fan of encoders. For moving distances that are more exact it doesnt work the greatest.