Interstellar's TARS - Animation Tips

So I’ve begun creating a scene involving putting TARS from Interstellar onto real footage. I’m taking this project seriously because it involved a lot of techniques and stuff that I have never touched before (PBR metals, creating HDRi maps, etc.) and I’ve ran into the first wall where I need to reach out for help.

The cool thing about TARS (And CASE) is he has motors in between his 4 legs that can move up and down, meaning he has several ways to get around.

http://imagesmtv-a.akamaihd.net/uri/mgid:file:http:shared:mtv.com/news/wp-content/uploads/2014/11/tumblr_nep57pn3HO1rv73a8o1_500-1415831445.gif?quality=.8&height=209&width=500http://cinetropolis.net/wp-content/uploads/2014/12/INTERSTELLAR-CASE-GIF-2.gifhttps://38.media.tumblr.com/a69111f19428cc16d7de25b6f3013300/tumblr_neuhpt0Cgq1qc31upo1_400.gif

Take note of the fluidity of the way he moves.

Now I’ve just started animating him, and it looks pretty bad. As you can tell, I’ve never done any animation work before.

I need tips/critique on the animation. I know it looks jagged and unnatural, but I have no clue how to do this. I have researched animating and watched plenty of videos, but it still looks terrible.

HERE IS THE .BLEND