How to control a Actor to walk through walls in a constant speed?

Hi everyone, I am new to UE4, just want to ask how to control a Actor to walk through walls in a constant speed?
I am using the Add Input Movement node in Blueprint to get the input of keybord which is WSAD.

If the target of Add Input Movement node is a Pawn or Default Pawn, it just can’t move in a canstant speed, it has to be set a acceleration in the Detail panel of FloatingPawnMovement component or the MovementComponent.

if the target of Add Input Movement node is a Character, it will collides everything because of the existence of CapsuleComponent. Then I set the Details panel of CapsuleComponent → Collision → Collision presets to No collision or Overlap all, and it will straight falling down for the reason of no collision and the gravity.

OK, then I try to kill the gravity, I set the Gravity Scale to 0 in the Details panel of CharactorMovement component -->Charactor Movement(General Settings), then it comes out a wierd slow movement.

Then I set the Default Land Movement to “Flying” in the Details panel of CharactorMovement component–>Charactor Movement(General Settings), it did move faster, but with the annoying acceleration.

It make me crazy, just want to ask how to control a Actor to walk through walls in a constant speed?