Integrated capacitive bridge and integrated flexure functions inertial measurement unit

A leveling system comprising:

• a platform coupled to said missile housing and defining an xz-plane, said platform controller by said processor;
• a first flexure plate accelerometer coupled to said platform at an angle such that said first flexure plate accelerometer is sensitive to movement of said first flexure plate accelerometer in an yz-plane, said first flexure plate accelerometer comprising a first flexure plate generating a first flexure plate accelerometer signal in response to movement of said first flexure plate;
• a second flexure plate accelerometer coupled to said platform at an angle such that said second flexure plate accelerometer is sensitive to movement of said second flexure plate accelerometer in said yz-plane, said second flexure plate accelerometer comprising a second flexure plate generating a second flexure plate accelerometer signal in response to movement of said second flexure plate;
• a third flexure plate accelerometer coupled to said platform at an angle such that said third flexure plate accelerometer is sensitive to movement of said third accelerometer in said xz-plane, said third flexure plate accelerometer comprising a third flexure plate generating a third flexure plate accelerometer signal in response to movement of said third flexure plate;
• a fourth flexure plate accelerometer coupled to said platform at an angle such that said fourth flexure plate accelerometer is sensitive to movement of said fourth accelerometer in said xz-plane, said fourth flexure plate accelerometer comprising a fourth flexure plate generating a fourth flexure plate accelerometer signal in response to movement of said fourth flexure plate;
• a fifth flexure plate accelerometer coupled to said platform at an angle such that said third flexure plate accelerometer is sensitive to movement of said fifth accelerometer in a xy-plane, said fifth flexure plate accelerometer comprising a fifth flexure plate generating a fifth flexure plate accelerometer signal in response to movement of said fifth flexure plate;
• a sixth flexure plate accelerometer coupled to said platform at an angle such that said sixth flexure plate accelerometer is sensitive to movement of said sixth accelerometer in said xy-plane, said sixth flexure plate accelerometer comprising a sixth flexure plate generating a sixth flexure plate accelerometer signal in response to movement of said sixth flexure plate;
• and
• a processor coupled to said first flexure plate accelerometer, said second flexure plate accelerometer, said third flexure plate accelerometer, said fourth flexure plate accelerometer, said fifth flexure plate accelerometer, and said sixth flexure plate accelerometer, said processor receiving said first flexure plate accelerometer signal, said second flexure plate accelerometer signal, said third flexure plate accelerometer signal, said fourth flexure plate accelerometer signal, said fifth flexure plate accelerometer signal, and said sixth flexure plate accelerometer signal, said processor leveling said platform and determining an east-west vector of rotation of the earth as a function of said first, second, third, fourth, fifth, and sixth accelerometer signals and generating a compass reference base as a function of said east-west vector.

A system for controlling inertia acting on an aerospace system relative to an x-axis, y-axis, and z-axis comprising:

• an inertial platform;
• a gyrocompass mounted on said platform and generating an output indicating a magnitude of a velocity vector through the xz-plane, when the xz-plane is level with local gravity perpendicular thereto, said gyrocompass may be rotated 360° to establish an east-west direction of earth rotation,
• an integrated inertial measurement unit coupled to said inertial platform and comprising a first flexure accelerometer and a second flexure accelerometer located along the z-axis and having deflection axes perpendicular to the xz-plane, wherein orientation of said accelerometers is such that acceleration in the y direction yields a positive output, further, clockwise rotation of said first flexure accelerometer and said second flexure accelerometer about the x-axis yields a positive angular acceleration,
• said integrated inertial measurement unit further comprising a third flexure accelerometer and a fourth flexure accelerometer located along the x-axis, said third flexure accelerometer and said fourth flexure accelerometer having a deflection axis perpendicular to the xy-plane, said third flexure accelerometer and said fourth flexure accelerometer oriented such that acceleration in the z direction yields a positive output and clockwise rotation about the y-axis yields a positive angular acceleration,
• said integrated inertial measurement unit further comprising a fifth flexure accelerometer and a sixth flexure accelerometer located along the y-axis, said fifth flexure accelerometer and said sixth flexure accelerometer having a deflection axis perpendicular to the yz-plane, orientation of said fifth flexure accelerometer and said sixth flexure accelerometer is such that acceleration in the x direction yields a positive output and clockwise rotation about the z-axis yields a positive angular acceleration;
• a first angular readout device detecting current angular position of both said first flexure accelerometer and said second flexure accelerometer relative to said platform;
• a second angular readout device detecting current angular position of both said third flexure accelerometer and said fourth flexure accelerometer relative to said platform;
• a third angular readout device detecting current angular position of both said fifth flexure accelerometer and said sixth flexure accelerometer relative to said platform;
• an actuator activating an object control device in response to a platform control signal from said processor;
• and
• a processor utilizing signals generated from said first flexure accelerometer, said second flexure accelerometer, said third flexure accelerometer, said fourth flexure accelerometer, said fifth flexure accelerometer, said sixth flexure accelerometer, said first angular readout device, said second angular readout device, and said third angular readout device, said processor computing signals and driving controlling gimbals and selecting a required mode and providing output data required by the system for maintaining an essentially zero rotation about the x-, y-, and z-axes when in an inertial mode, said processor further receiving gyrocompass signals and setting said gyrocompass signals as initial conditions for said first, second, third, fourth, fifth, and sixth flexure accelerometers.

A method for controlling an inertial measurement unit having a z-axis gimbal with a first flexure accelerometer and a second flexure accelerometer positioned thereon, an x-axis gimbal with a third flexure accelerometer and a fourth flexure accelerometer positioned thereon, and y-axis gimbal with a fifth flexure accelerometer and a sixth flexure accelerometer positioned thereon, said z-, x-, and y-axis gimbals mounted on a platform, said method comprising:

• leveling the platform perpendicular to a local gravity vector;
• computing a spatial gravity vector with respect to the platform as a function of first angles whereby the x-, y-, and z-axis gimbals experience maximum forces;
• controlling the gimbals such that an xz-plane, formed as a function of an intersection of axes of rotation of the x- and z-axis gimbals, is perpendicular to said local gravity vector;
• rotating the platform about a z-axis and recording a second gimbal angle wherein a maximum positive force vector is generated, thereby establishing an east-west vector;
• and
• recording said first gimbal angles and said second gimbal angle.

A method for controlling an inertial measurement unit having a z-axis gimbal with a first flexure accelerometer and a second flexure accelerometer positioned thereon, an x-axis gimbal with a third flexure accelerometer and a fourth flexure accelerometer positioned thereon, and y-axis gimbal with a fifth flexure accelerometer and a sixth flexure accelerometer positioned thereon, said z-, x-, and y-axis gimbals mounted on a platform, said method comprising:

• leveling the integrated inertial measurement unit with respect to a local vertical;
• establishing a directional reference for the integrated inertial measurement unit;
• positioning the platform perpendicular to a local gravity vector;
• reading present gimbal positions for the z-axis gimbal, the x-axis gimbal, and the y-axis gimbal;
• holding gimbal angles of the fifth flexure accelerometer and the sixth flexure accelerometer and the third flexure accelerometer and the fourth flexure accelerometer constant;
• rotating the first flexure accelerometer and second flexure accelerometer gimbal through 360°;
• while rotating the first and second flexure accelerometer gimbal, recording first and second flexure accelerometer gimbal angles where a first maximum force is detected;
• rotating the third and fourth flexure accelerometer gimbal through 360°;
• while rotating the third and fourth flexure accelerometer gimbal, recording third and fourth flexure accelerometer gimbal angles where a second maximum force is detected;
• rotating the fifth and sixth flexure accelerometer gimbal through 360°;
• while rotating the fifth and sixth flexure accelerometer gimbal, recording fifth and sixth flexure accelerometer gimbal angles where a third maximum force is detected;
• computing a spatial gravity vector with respect to the platform as a function of said first, second, and third maximum force data;
• computing and commanding gimbal angles that will result in an xz-plane being perpendicular to said spatial gravity vector;
• checking whether a signal from the first flexure accelerometer is equal to a signal from the second flexure accelerometer;
• recording a value of said first flexure accelerometer signal and said second flexure accelerometer signal;
• rotating the x-axis gimbal 90° such that a z-axis is up and the third and fourth flexure accelerometers are perpendicular to said local vertical;
• checking whether a signal from the third flexure accelerometer is equal to a signal from the fourth flexure accelerometer;
• verifying vertical orientation by rotating the platform 90° so that said z-axis is vertical and the third and fourth flexure accelerometers are generating equal signals also equal to a value measured by the first and second flexure accelerometers;
• restoring said xz-plane to a predetermined position;
• recording a value of said third and fourth flexure accelerometer signals;
• checking whether a value of said first and second flexure accelerometer signals equal said value of said third and fourth flexure accelerometer signals;
• rotating the platform back to said xz-plane perpendicular to said vertical;
• computing a level of the platform;
• leveling the platform;
• rotating the leveled platform about said z-axis;
• recording a gimbal angle where a force vector is maximum and positive establishing an east-west direction as a function of said gimbal angle;
• using said gimbal angle as a compass reference base of an operational mode;
• rotating said xz-plane 360° clockwise while recording an output of a gyrocompass;
• rotating said xz-plane counterclockwise for 360°;
• selecting maximum points of said xz-plane as a function signals from said gyrocompass;
• recording a defined angular position as an east-west earth rotation factor;
• rotating the inertial measurement unit to said target vector;
• activating said operation mode;
• recording said gimbal angles for maintenance of inertial position and guidance utility in said operation mode;
• maintain said inertial position as a function of said angular outputs;
• reading a present position of all the gimbals;
• redefining a current access position as a local level pointing at a predetermined target for computational usage;
• controlling a gimbal drive for maintaining current inertial position of the gimbals;
• checking whether platform angular acceleration at the x-, y-, and z-axes are equal to zero;
• and
• driving either the x-, y-, or z-axis gimbal in response to a signal that platform angular acceleration of the x-, y-, and z-axes gimbals are not equal to zero.