SENSOR FUSION OF MOTION DATA OBTAINED FROM PORTABLE ELECTRONIC DEVICES

• US 20130158928A1
• Filed: 12/16/2011
• Published: 06/20/2013
• Est. Priority Date: 12/16/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hogdal, Greg
• Granted Patent: US 9,410,809 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: G01C 21/04 by terrestrial means G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 21/06 involving measuring of drift angle; involving correction for drift
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth
• CPC Class Codes: G01C 21/10 by using measurements of speed or acceleration G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 21/14 by recording the course traversed by the object G01C21/16 takes precedence
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/18 Stabilised platforms, e.g. by gyroscope
• CPC Class Codes: G01C 21/185 for gravity
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G06F 1/1694 the I/O peripheral being a single or a set of motion sensors for pointer control or gesture input obtained by sensing movements of the portable computer

Abstract

A method for determining an orientation of a portable or mobile electronic device includes determining an orientation of the device using at least a first inertial motion sensor (e.g., a gyroscope) with which the portable electronic device is equipped. A correction factor is provided to the orientation of the electronic device using a feedback control signal based on motion data obtained from at least a second inertial motion sensor (e.g. an accelerometer) to reduce drift in motion data obtained from the first inertial sensor. Responsive to a loss of valid motion data from the first inertial motion sensor, a rate at which the correction factor is provided to the orientation of the portable electronic device is increased.

Claims

1. A method for determining an orientation of a portable electronic device, comprising:

sensing a rotational rate of the device using a first rotational sensor;

sensing a total acceleration including a gravitational component and linear acceleration component of the device using a second inertial sensor;

filtering data obtained by the second inertial sensor using a variable low pass filter which filters the data by an amount that depends at least in part on the sensed rotational rate of the device;

deriving an orientation of the device at successive periods of time based in part on the rotational rate sensed at each time; and

applying a correction factor to the derived orientation of the device based at least in part on the sensed gravitational component and the linear acceleration component of the filtered data obtained by the second inertial sensor when the second inertial sensor senses a total acceleration that is equal to the gravitational component within a predefined threshold to thereby obtain a corrected orientation of the device at a subset of the successive periods of time.

2. The method of claim 1 further comprising reducing the amount of filtering performed on the data obtained by the second inertial sensor as the sensed rotational rate of the device increases.

3. The method of claim 1 in which the corrected orientation of the device is obtained in body coordinates associated with the device and further comprising transforming the corrected orientation of the device in body coordinates to Earth coordinates.

4. The method of claim 1 in which applying the correction factor includes adjusting the derived orientation in response to a feedback control signal from the second inertial sensor to thereby obtain the corrected orientation of the device.

5. The method of claim 4 in which the feedback control signal is generated in a feedback control process that includes a proportional function and an integral function.

6. The method of claim 5 further comprising entering a fast correction mode of the feedback control process when valid data from the first inertial sensor is unavailable, the feedback control process in said fast correction mode having a faster proportional response relative to a nominal proportional response used when valid data from the first inertial sensor is available.

7. The method of claim 5 in which the fast correction mode is entered and exited at a rate greater than a linear rate.

8. The method of claim 7 in which the rate greater than the linear rate is a hyperbolic rate.

9. The method of claim 1 further comprising determining a geographic direction using a magnetometer, wherein applying the correction factor is further based on the geographic direction that is determined.

10. The method of claim 9 further comprising initializing the determination of the orientation of the device using absolute orientation information obtained from the second inertial sensor and the magnetometer.

11. A portable electronic device, comprising:

at least first and second inertial sensors for sensing motion of the device;

one or more processors for executing computer-executable instructions; and

one or more computer-readable storage media for storing the machine-executable instructions, the instructions when executed by the one more processors implementing processing logic that, based on motion data derived from the first inertial sensor in response to physical movement of the electronic device, is capable of tracking an orientation of the device, said tracked orientation having an error associated therewith such that the processing logic periodically reduces the error using a feedback control signal of a PID control process based on additional motion data obtained from the second inertial sensor, wherein, if said processing logic determines that the rotational motion data obtained from the first inertial sensor is invalid or unavailable while tracking the orientation of the device, the processing logic is capable of suppressing an integral function and causing a proportional function of the PID control process to increase its response rate until the rotational motion data is again available and valid.

12. The portable electronic device of claim 11 in which the first inertial sensor is a gyroscope providing rotational motion data and the orientation derived from the rotational motion is a relative orientation of the device.

13. The portable electronic device of claim 12 in which the processing logic initializes the rotation motion using the feedback control signal to obtain an absolute rotation motion of the device.

14. The portable electronic device of claim 12 in which the second inertial sensor is an accelerometer sensing a total acceleration that includes a gravitational component and a linear acceleration component.

15. The method of claim 14 further comprising filtering data obtained by the second inertial sensor using a variable low pass filter which filters the data by an amount that depends at least in part on the sensed rotational rate of the device.

16. The method of claim 15 further comprising reducing the amount of filtering performed on the data obtained by the second inertial sensor as the sensed rotational rate of the device increases.

17. The method of claim 11 in which the processing logic suppresses the integral function and causes the proportional function to increase at a rate greater than a linear rate.

18. One or more computer-readable storage media containing instructions which, when executed by one or more processors disposed in a mobile electronic device, perform a method comprising the steps of:

determining an orientation of a mobile electronic device using at least a first inertial motion sensor with which the mobile electronic device is equipped;

providing a correction factor to the orientation of the mobile electronic device using a feedback control signal based on motion data obtained from at least a second inertial motion sensor to reduce drift in motion data obtained from the first inertial sensor;

responsive to a loss of valid motion data from the first inertial motion sensor, increasing a rate at which the correction factor is provided to the orientation of the mobile electronic device.

19. The computer-readable storage media of claim 18 in which the first inertial motion sensor is a gyroscope detecting rotational motion of the device and the second inertial motion sensor is an accelerometer sensing a total acceleration that includes a gravitational component and a linear acceleration component said correction factor being provided to the orientation of the mobile electronic device when the accelerometer senses a total acceleration equal to the gravitational component within a predefined threshold.

20. The computer-readable storage media of claim 18 in which the second inertial motion sensor is an accelerometer further comprising filtering motion data obtained by the accelerometer using a variable low pass filter which filters the motion data obtained by the accelerometer by an amount that depends at least in part on the sensed rotational rate of the device.