If by handheld controls, you mean manual devices (e.g., knobs and the like),
you may want to look at standards such as MIL STD 1472; it contains a wealth
of info on those. If you have other kind of devices in mind, send me an
email and I may have a couple of references handy.
Jean-Yves Fiset, ing., Ph. D.
Systes Humains-Machines Inc. ("Shumac")
Ingierie des facteurs humains, des systes et du logiciel
Human Factors, Systems and Software Engineering