How to set static friction and kinetic friction for sphere to plane contact model?

I am doing simulation for biped robot in simscape matlab2017b, but when simulation running, the robot was sliding on ground.

My static friction is 0.8 and kinetic friction is 0.6 accroding other simulation for robot. But I do not know why set this values.

So I need to test the friction parameters between real groud and real robot foot, right?

Thanks.