the uncluttered user interface (user interface being an alternative term for human-machine interface and more appropriate for your context):
A user interface is the system by which people (users) interact with a machine. The user interface includes hardware (physical) and software (logical) components.
Ever since the increased use of personal computers and the relative decline in societal awareness of heavy machinery, the term user interface has taken on overtones of the (graphical) user interface, while industrial control panel and machinery control design discussions more commonly refer to human-machine interfaces.
http://en.wikipedia.org/wiki/User_interface