Micromachined rate and acceleration sensor

In an apparatus for measuring the specific force and angular rotation rate of a moving body, a micromachined silicon structure comprising:

• a) a monolithic silicon substrate having first and second substantially planar surfaces disposed substantially parallel to each other;
• b) a first accelerometer formed of said substrate and having a first force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said first force sensing axis, said first accelerometer having a first proof mass, a first support frame, and first flexure means for connecting said first proof mass to said first support frame;
• c) a second accelerometer formed of said substrate and having a second force sensing axis for producing a second output signal indicative of the acceleration of the moving body along said second force sensing axis, said second accelerometer having a second proof mass, a second support frame, and second flexure means for connecting said second proof mass to said second support frame;
• d) a dither frame formed of said substrate;
• and
• e) a first pair of S-bend flexures connected between said first support frame and said dither frame, and a second pair of S-bend flexures connected between said second support frame and said dither frame, said first and second pairs of S-bend flexures being formed of said substrate for mounting said first and second accelerometers such that said first and second force sensing axes are both oriented at the same angle with respect to said first and second surfaces and such that said first and second accelerometers can be moved along a vibration axis perpendicular to each of said first and second sensing axes;
• wherein dithering of said first and second accelerometers along said vibration axis permits measurement of said specific force and angular rotation rate of said moving body.

In an apparatus for measuring the specific force and angular rotation rate of a moving body, a micromachined silicon structure comprising:

• a) a monolithic silicon substrate having first and second substantially planar surfaces disposed substantially parallel to each other;
• b) an accelerometer formed of said substrate and having a force sensing axis for producing an output signal indicative of the acceleration of the moving body along said force sensing axis, said accelerometer comprising an accelerometer frame, a proof mass, and hinge means interconnected between said accelerometer frame and said proof mass for rotating said proof mass about a hinge axis when the moving body is subjected to a force along said force sensing axis;
• and
• c) mounting means formed of said substrate for mounting said accelerometer such that said accelerometer can be moved along a vibration axis perpendicular to said force sensing axis;
• wherein dithering said accelerometer along one of said vibration axis or said force sensing axis enables measurement of said specific force and angular rotation rate of said moving body.

In an apparatus for measuring the specific force and angular rotation rate of a moving body, a micromachined silicon structure comprising:

• a) a monolithic silicon substrate having first and second substantially planar surfaces disposed substantially parallel to each other;
• b) first and second accelerometers formed of said substrate, each of said accelerometers having a force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said force sensing axis, each of said accelerometers further having an accelerometer frame, a proof mass, and hinge means interconnected between said frame and said proof mass for allowing said proof mass to rotate about a hinge axis when the moving body is subjected to a force along said force sensing axis, said proof mass having a first end interconnected by said hinge means to said frame and a free end permitted to rotate freely about said hinge axis with respect to said frame, said proof mass further having a center of gravity and a pendulous axis aligned to intersect said center of gravity and said hinge axis, flexible means interconnected between said frame and said free end of said proof mass for flexibly restraining the pivoting of said proof mass about said pendulous axis, and a dither frame;
• said structure further comprising flexure means for connecting the accelerometer frame of each of said first and accelerometers to said dither frame;
• said flexure means being generally compliant to allow dithering of said first and second accelerometers along a dither axis, said dither axis being generally perpendicular to said force sensing axes of said first and second accelerometers;
• wherein dithering of said first and second accelerometers along said dither axis enables measuring said force and angular rotation rate of said moving body.

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.

A combined angular rate 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 hinges and flexible connectors, 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 flames being connected to said second frame by flexures;
• means for sensing a displacement of each of said proof masses;
• and
• means for dithering each said proof masses along a dither axis that is disposed perpendicularly to said rate axis.