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udacity / robotics-nanodegree-issues

Public waffleboard to track Robotics Nanodegree Issues
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Controls 1-22 Putting it all together - code outline is wrong! #121

Closed adammalpass closed 7 years ago

adammalpass commented 7 years ago

In controls 1-22 there is a code outline for PID controller, but if you follow the outline it will not work! Look at this section:


        self.error_sum_ += error * delta_time

        # Update the past error
        self.last_error_ = error

        # Find delta_error
        delta_error = error - self.last_error_

        # Update the past error
        self.last_error_ = error```

Firstly notice there is an instruction to set self.last_error_ twice, once before and once after delta_error. The first one _must_ be removed. In the current code `delta_error` will always be 0 and hence the derivative term has no effect.

I removed this one line from my code and now everything works perfectly
adammalpass commented 7 years ago

Also the solution.py on same page contains same issue - please fix too!

kylesf commented 7 years ago

Fixed, thanks adam!