Script for CSS html buttons using ruby watir

Ruby
1 
           <div class="btnleft"></div>

           <input name="addbutton" value="Add" onclick="AddButton()"

class=“btncenter” type=“button”>

          <div class="btnright"></div>


  </div>

Here for above add button what is the script we have use.
1)Iam trying with the following methods but iam getting “unable to
recognize” error

1)$ie.button(:name, “addbutton”).click
$ie.button(:value, “Add” ).click

2)ie.button(:name, “addbutton”).click