Four-degree-of-freedom solid state MEMS joystick

This paper reports on a novel four-degree-of-freedom solid state joystick. It consists of a rigid polymer cylinder with spherical dome on top of a CMOS chip. The sensor chip with a size of 2.0times2.5 mm² contains 10 octagonal stress sensors distributed across the surface exploiting the shear piezoresistive effect in silicon. The joystick shows a linear response of its integrated stress sensors to forces F_x, F_y, and F_z up to 5 N and to a moment M_z up to 5 mNm. For calibration, the sensitivities towards these loads were measured individually. The Moore-Penrose inverse of the sensitivity matrix enables the extraction of these four loads from the vector of the piezoresistor signals.