Micromachined accelerometer gyroscope

A combined angular rate and acceleration sensor, comprising:

• a first accelerometer and a second accelerometer each formed from a substantially planar body comprised of monocrystalline silicon, said planar body having first and second oppositely disposed major surfaces, each of said accelerometers including a first frame and a proof mass suspended from said first frame by first flexures, each of said accelerometers having an associated sensitive axis and an associated rate axis that is orthogonally disposed to said sensitive axis;
• a second frame that is disposed about each of said first frames, each of said first frames being connected to said second frame by second flexures;
• means for sensing a displacement of each of said proof masses;
• and
• means for dithering each of said proof masses along a dither axis that is disposed perpendicularly to said rate axis, said dithering means including,
• at least one first electrode and at least one second electrode, said at least one first electrode and said at least one second electrode each including a plurality of elongated finger portions that are disposed in parallel and interdigitated one with another, said first electrode being disposed over said first major surface and said second electrode being disposed over said second major surface each for exerting an electrostatic force upon an underlying portion of said planar body in response to an oscillatory drive signal, wherein each of said underlying portions of said planar body are connected to said second frame by third flexures, and wherein each of said underlying portions of said planar body has a plurality of grooves formed therein, said plurality of grooves being disposed in a parallel orientation with said finger portions of the overlying electrode.

A combined angular rate and acceleration sensor, comprising:

• a substantially planar body comprised of monocrystalline silicon, said planar body having first and second oppositely disposed major surfaces, said planar body having portions selectively removed for defining a plurality of regions of said planar body, said plurality of regions including,
• a first region comprising a quadrilateral outer frame structure;
• a second region comprising a first accelerometer having a quadrilateral first inner frame structure and a first proof mass suspended from said first inner frame structure by first flexures, said first inner frame structure being connected to said outer frame structure by second flexures;
• a third region comprising a second accelerometer having a quadrilateral second inner frame structure and a second proof mass suspended from said second inner frame structure by third flexures, said second inner frame structure being connected to said outer frame structure by fourth flexures;
• wherein each of said first and second accelerometers has an associated sensitive axis and an associated rate axis that is orthogonally disposed to said sensitive axis;
• said regions further including,
• a fourth region comprising centrally disposed support structure;
• a fifth region comprising a first driver mass having a plurality of grooves formed in first and second major surfaces thereof, said first driver mass being connected to said outer frame structure and to said support structure by fifth flexures;
• and
• a sixth region comprising a second driver mass having a plurality of grooves formed in first and second major surfaces thereof, said second driver mass being connected to said outer frame structure and to said support structure by sixth flexures;
• wherein said first and said second driver masses are also connected to said inner frames of said first and said second accelerometers through primary flexures;
• said integrated acceleration and rate sensor further including,
• a first planar structure having a surface overlying said first major surface of said planar body, said first planar structure having a first plurality of electrodes formed upon said surface, said first plurality of electrodes including a first forcing electrode that overlies said first proof mass, a second forcing electrode that overlies said second proof mass, a first pair of interdigitated drive electrodes overlying said grooves of said first driver mass, and a second pair of interdigitated drive electrodes overlying said groves of said second driver mass;
• and
• a second planar structure having a surface overlying said second major surface of said planar body, said second planar structure having a first plurality of electrodes formed upon said surface, said first plurality of electrodes including a first driver electrode that overlies said first proof mass, a second driver electrode that overlies said second proof mass, a first pair of interdigitated drive electrodes overlying said grooves of said first driver mass, and a second pair of interdigitated drive electrodes overlying said groves of said second driver mass, wherein
• the plurality of pairs of interdigitated drive electrodes are responsive to an oscillatory drive signal for exerting an electrostatic force upon edges of said trenches for dithering said driver masses in phase and antiphase within a plane of said planar body and, through said primary flexures, for dithering said first and said second accelerometers in phase and antiphase in a direction that is orthogonal to said associated sensitive axis of each of said first and second accelerometers.