How to define response function for optimizing of bearing length with hyperstudy?

Hello

I have to optimize bearing length in extrusion process with hyperstudy(I do this with hxsolver (that relateed with hyperstudy directly)) but my supervisor doesnt accept and he wants me that do with hyperstudy and define objective function but I cant define it.

how to define response function for obtaining uniform velocity?

Thanks alot.