Current value from target value plus output to be low, so the shift of the deviation is rather value acceleration while they close in the sense of the people.
Since the current value is low from the target value, it becomes a positive output, because the variation is somewhat during the acceleration of the deviation, the value is assumed to or close to the feeling of the people.
The current value from the target value is low, so that the output of the amount of change in the acceleration deviation from something, and this value is close to the human sense.