A method for achieving constant rotation rates in a microorthogonal linkage system

Silicon micromachine designs include engines that consist of orthogonally oriented linear comb-drive actuators mechanically connected to a relating gear. These gears are as small as 50 /spl mu/m in diameter and can be driven at rotation rates exceeding 300000 r/min. Generally, these engines will run with nonuniform rotation rates if the drive signals are not properly designed and maintained over a range of system parameters. We present a method for producing constant rotation rates in a microengine driven by an orthogonal linkage system. We show that, provided the values of certain masses, springs, damping factors, and lever arms are in the right proportions, the system behaves as though it were symmetrical. We will refer to systems built in this way as being quasi-symmetrical. We show that if a system is built quasi-symmetrically, then it is possible to achieve constant rotation rates even if one does not know the form of the friction function or the value of the friction. We analyze this case in some detail.