Mems device oscillating about two axes and having a position detecting system, in particular of a piezoresistive type

A position detecting method for a MEMS device, comprising the steps of:

• acquiring first and second measure signals generated by a first and a second stress sensor elements coupled to respective elastic suspension elements of a frame supporting a platform rotating about a first axis, the frame being rotatably supported about a second axis by the elastic suspension elements anchored to a fixed structure through respective anchorage portions arranged offset with respect to the second axis;
• adding the first and second measure signals to obtain a sum signal;
• and
• subtracting the first and second measure signals to obtain a difference signal;
• wherein a signal between the sum signal and the difference signal indicates an angle of rotation about the first axis, and
• wherein another signal between the sum signal and the difference signal indicates an angle of rotation about the second axis.

A MEMS device, comprising:

• a platform carried by a frame via elastic connection elements configured to enable rotation of the platform about a first axis;
• a bearing structure supporting the frame through first and second elastic suspension arms configured to enable rotation of the frame about a second axis transverse to the first axis;
• wherein the first and second elastic suspension arms are anchored to the bearing structure through respective anchorage portions arranged offset with respect to the second axis;
• and
• a stress sensor formed by first and second sensor elements respectively arranged on the first and second suspension arms and positioned in proximity of the anchorage portions, on a same side of the second axis, in a symmetrical position with respect to the first axis.

A MEMS micromirror system, comprising:

• a MEMS device, including:
• a platform carried by a frame via elastic connection elements configured to enable rotation of the platform about a first axis;
• a bearing structure supporting the frame through first and second elastic suspension arms configured to enable rotation of the frame about a second axis transverse to the first axis;
• wherein the first and second elastic suspension arms are anchored to the bearing structure through respective anchorage portions arranged offset with respect to the second axis;
• and
• a stress sensor formed by first and second sensor elements respectively arranged on the first and second suspension arms and positioned in proximity of the anchorage portions, on a same side of the second axis, in a symmetrical position with respect to the first axis;
• wherein each sensor element comprises first and second resistors of a piezoresistive or piezoelectric type, the first and second resistors of each sensor element being arranged transverse to the second axis and symmetrical to each other with respect to a symmetry axis parallel to the first axis, the first and second resistors of each sensor element defining first and second biasing nodes and intermediate output nodes;
• a processing unit connected to the intermediate output nodes of the sensor elements and configured to add and subtract signals at the intermediate nodes and generate measured angular position signals;
• and
• a position correction unit configured to compare the measured angular position signals with desired position signals and to generate a driving signal.