Systems and method for gyroscope calibration
View Patent ↗A mechanism by which a MEMS gyroscope sensor can be calibrated using data gathered from other sensors in a system incorporating the MEMS gyroscope sensor is provided. Data gathered from an accelerometer and a magnetometer in fixed orientation relative to the gyroscope is used to calculate changes in orientation of a system. A constant acceleration vector measured by the accelerometer and a constant magnetic vector measured by the magnetometer are used as reference vectors in a solution to Wahba's problem to calculate a rotation matrix providing the system's orientation with respect to those two constant vectors. By comparing changes in orientation from one time to a next time, measured rates of angular change can be calculated. The measured rates of angular change can be used along with observed gyroscope rates of angular change as input to a linear regression algorithm, which can be used to compute gyroscope trim parameters.
1. A system comprising:
a first set of directionally sensitive sensors, wherein the first set of directionally sensitive sensors comprises three orthogonally-oriented sensors configured to respond to gravity;
a second set of directionally sensitive sensors, wherein the second set of directionally sensitive sensors comprises three orthogonally-oriented sensors configured to respond to a constant magnetic field;
a set of gyroscope sensors, wherein the set of gyroscope sensors comprises three sensors oriented on orthogonally-oriented axes each configured to respond to rotation about a corresponding axis;
a processor, communicatively coupled to the first and second sets of directionally sensitive sensors and the set of gyroscope sensors, and configured to
determine a first orientation of the system with respect to
a gravity vector using signals received from the first set of directionally sensitive sensors at a first time, and
a magnetic field vector using signals received from the second set of directionally sensitive sensors at the first time, wherein
said determining the first orientation of the system is performed using a minimized loss function solution to Wahba's problem wherein the gravity vector and the magnetic field vector are fixed reference vectors,
determine an incremental change in orientation of the system with respect to the first orientation
using signals from the first set of directionally sensitive sensors at the first time and at a second time and
using signals from the second set of directionally sensitive sensors at the first time and the second time, wherein
said determining the incremental change in orientation of the system is performed using a minimized loss function solution to Wahba's problem comparing the sensor signals from the first time and the second time,
determine a second orientation of the system using the first orientation and the incremental change in orientation of the system,
determine a measured angular rate of change of the system using the determined first orientation of the system and the determined second orientation of the system,
determine an observed angular rate of change of the system using signals received from the set of gyroscope sensors during a period between the first time and the second time,
determine a set of measured angular rates of change of the system over a plurality of time periods,
perform a linear regression analysis to determine a difference between a set of observed angular rates of change over the plurality of time periods and the set of measured angular rates of change of the system, and
determine gyroscope gain and bias from the determined difference.
2. The system of claim 1 further comprising:
a memory, coupled to the processor, and configured to store the gyroscope gain and bias.
3. The system of claim 2 further comprising:
the processor is further configured to use the stored gyroscope gain and bias as trim parameters for subsequent gyroscope functions.
4. The system of claim 1 wherein the measured angular rate of change of the system is used in virtual gyroscope applications.
5. The system of claim 1 wherein the minimized loss function solution to Wahba's problem provides a mapping between measured values detected from the sensors and the fixed reference vectors.
6. A method comprising:
determining a first orientation of a system with respect to a gravity vector using signals received from a first set of directionally sensitive sensors at a first time and a magnetic field vector using signals received from a second set of directionally sensitive sensors at the first time, wherein
said determining the first orientation of the system is performed using a minimized loss function solution to Wahba's problem wherein the gravity vector and the magnetic field vector are fixed reference vectors;
determining an incremental change in orientation of the system with respect to the first orientation using signals from the first set of directionally sensitive sensors at the first time and at a second time and using signals from the second set of directionally sensitive sensors at the first time and at the second time, wherein
said determining the incremental change in orientation of the system is performed using a minimized loss function solution to Wahba's problem comparing the sensor signals from the first time and the second time;
determining a second orientation of the system using the first orientation and the incremental change in orientation of the system;
determining a measured angular rate of change of the system using the first orientation of the system and the second orientation of the system;
determining an observed angular rate of change of the system using signals received from a set of gyroscope sensors during a period between the first time and the second time;
determining a set of measured angular rates of change of the system over a plurality of time periods;
performing a linear regression analysis to determine a difference between a set of observed angular rates of change over the plurality of time periods and the set of measured angular rates of change of the system over the plurality of time periods; and
determining gyroscope gain and bias for the set of gyroscope sensors from the determined difference.
7. The method of claim 6 further comprising storing the gyroscope gain and bias.
8. The method of claim 7 further comprising using the stored gyroscope gain and bias as trim parameters for subsequent gyroscope functions.
9. The method of claim 6 further comprising using the measured angular rate of change of the system in virtual gyroscope applications.
10. The method of claim 6 wherein the first set of directionally sensitive sensors comprises three orthogonally-oriented sensors configured to respond to gravity.
11. The method of claim 10 wherein the three orthogonally-oriented sensors configured to respond to gravity comprise accelerometers.
12. The method of claim 6 wherein the second set of directionally sensitive sensors comprises three orthogonally-oriented sensors configured to respond to a constant magnetic field.
13. The method of claim 12 wherein the three orthogonally-oriented sensors configured to respond to the constant magnetic field comprises magnetometers.
14. The method of claim 6 further comprising providing a mapping between measured values detected from the first and second sets of directionally-sensitive sensors and the respective fixed reference vectors using the minimized loss function solution to Wahba's problem.
15. An apparatus comprising:
a first set of directionally sensitive sensors configured to respond to gravity;
a second set of directionally sensitive sensors configured to respond to a constant magnetic field;
a set of gyroscope sensors, wherein the set of gyroscope sensors comprises three sensors oriented on orthogonally-oriented axes each configured to respond to rotation about a corresponding axis;
means for determining a first orientation of a system with respect to a gravity vector using signals received from the first set of directionally sensitive sensors at a first time and with respect to a magnetic field vector using signals received from the second set of directionally sensitive sensors at the first time, wherein the means for determining the first orientation of the system uses a minimized loss function solution to Wahba's problem wherein the gravity vector and the magnetic field vector are fixed reference vectors;
means for determining an incremental change in orientation of the system with respect to the first orientation using signals received from the first set of directionally sensitive sensors at the first time and at a second time and using signals received from the second set of directionally sensitive sensors at the first time and at the second time, wherein
said means for determining the incremental change in orientation of the system uses a minimized loss function solution to Wahba's problem comparing the sensor signals from the first time and the second time;
means for determining a second orientation using the first orientation and the incremental change in orientation of the system;
means for determining a measured angular rate of change of the system using the determined first orientation of the system and the determined second orientation of the system;
means for determining an observed angular rate of change of the system using signals received from the set of gyroscope sensors during a period between the first time and the second time;
means for determining a set of measured angular rates of change of the system over a plurality of time periods;
means for performing a linear regression analysis to determine a difference between a set of observed angular rates of change over the plurality of time periods and the set of measured angular rates of change of the system; and
means for determining gyroscope gain and bias from the determined difference.