PWM through a low pass filter tends to be slow in responding to changes or tends to have a lot of ripple. It doesn't have to be that way but those people who can design better don't usually have to be told to use a low pass filter.
An H bridge has TWO inputs. Either the H bridge is augmented with something else (such as an inverter) or another Arduino output is used (which has not been explained) or the H bridge is excessive because operation in both directions is not really needed or the H bridge is not really a full H bridge.
In any case, I would prefer to hear from the OP.