Method to reduce data rates and power consumption using device based attitude generation

• US 10,247,748 B2
• Filed: 08/12/2013
• Issued: 04/02/2019
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Keal, William Kerry, Lim, James, Karahan, Sinan
• Primary Examiner(s): Bloss, Stephanie E
• Application Number:
  US13/965,131
• Publication Number:
  US 20140278215A1
• Time in Patent Office: 2,059 Days
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01P 1/00 Details of instruments

Abstract

A method includes generating motion data by receiving a gyroscope data from a gyroscope sensor, performing integration using the gyroscope data and generating an integrated gyroscope data using a first processor. The method further includes receiving a data from one or more sensors, other than the gyroscope sensor, and performing sensor fusion using the integrated gyroscope data and the data to generate motion data using a second processor.

Claims

1. A method of generating orientation of a device comprising;

receiving a gyroscope output generated by a gyroscope located on a motion processing unit (MPU), the gyroscope sensing an angular velocity of the device at a first rate to generate the gyroscope output, the gyroscope and the MPU formed on a first package;

integrating, by a processor, the gyroscope output at the first rate to generate an integrated gyroscope output, the integrated gyroscope output representing a change in the orientation of the device, the processor formed on the first package;

receiving an accelerometer output generated by an accelerometer, the accelerometer sensing the orientation of the device to generate the accelerometer output, the accelerometer formed on the first package;

transmitting the integrated gyroscope output to a second processor at a rate lower than the first rate thereby reducing processing requirements of the MPU, traffic from the MPU, and power consumption;

transmitting the received accelerometer output to the second processor; and

performing sensor fusion, by the second processor using the transmitted integrated gyroscope output and the transmitted accelerometer output to generate the orientation of the device, the second processor formed on a second package;

receiving a requested data rate and based on the received requested data rate utilizing an output of the second processor to determine the data rate being requested,

wherein the first and second packages are distinct package and the lower rate of the transmitted integrated gyroscope output allows use of the MPU with various sensor fusion algorithms performed by the second package and reducing power consumption.

2. The method of claim 1, further including a compass configured to measure the orientation of the device.

3. The method of claim 1, further including performing bias removal from the gyroscope output prior to the integrating step.

4. The method of claim 1, further including performing bias removal after the integrating step.

5. The method of claim 1, further including performing bias removal using a current integrated gyroscope data and a previous integrated gyroscope data and a current sensor fusion output and a previous sensor fusion output.

6. The method of claim 1, wherein the gyroscope output is set to zero if an absolute value of the gyroscope output is less than a threshold.

7. The method of claim 1, wherein the integrated gyroscope data is a form of a quaternion.

8. The method of claim 1, wherein the quaternion is normalized.

9. The method of claim 1, wherein at least a portion of the integrated gyroscope data is compressed.

10. The method of claim 1, wherein the integrating step is performed starting from an initial data.

11. The method of claim 1, wherein the integrating step has an integration time period associated with it.

12. The method of claim 1, wherein the integrating step includes generating the integrated gyroscope data from two consecutive gyroscope outputs and a previous integrated gyroscope data.

13. The method of claim 1, further comprises:

receiving at least two consecutive gyroscope outputs from the gyroscope;

averaging the at least two consecutive gyroscope outputs to generate an average data; and

calculating a cross product of the at least two consecutive measurement outputs to generate a cross product data,

wherein the integrating step further includes integrating over a time interval using the average data and the cross product data.

14. The method of claim 1, further comprising performing a derivation of the integrated gyroscope data to generate equivalent gyroscope data, wherein a gyroscope bias is computed using the equivalent gyroscope data, the gyroscope bias introduced by the gyroscope when sensing.

15. The method of claim 1, wherein the integrating step comprises sampling of the gyroscope output, wherein the sampling starts after a predetermined number of samples and continues over a predetermined time period.

16. The method of claim 1, wherein during a dead zone where an input of the integrating step is close to zero and the integrated gyroscope output is made to remain the same.

17. The method of claim 1, further including computing an approximate gyroscope data from the integrated gyroscope output by computing a derivate of the integrated gyroscope output, the derivative of the integrated gyroscope output used to determine a gyroscope data bias.

18. A method of generating orientation of a device, comprising:

receiving at least two consecutive measurement outputs, at a first rate, from a gyroscope formed on a motion processing unit (MPU), each of the at least two consecutive measure outputs generated by the gyroscope sensing an angular velocity of the device, the MPU formed on a first package;

averaging the at least two consecutive measurement outputs to generate an average data;

calculating a cross product of the at least two consecutive measurement outputs to generate a cross product data; and

integrating to generate a gyroscope quaternion, at the first rate using a processor, the average data, the cross product data, and the gyroscope quaternion being transmitted to a sensor fusion at a rate lower than the first rate thereby causing a reduction in a processing requirement of the MPU and reducing power consumption, the sensor fusion generating at least one output;

receiving a requested data rate and based on the received requested data rate utilizing the at least one of the sensor fusion outputs to determine the data rate being requested,

wherein because the sensor fusion uses data transmitted by the first package at the lower rate and the sensor fusion is externally located relative to the first package, the MPU is operational with various sensor fusion algorithms and traffic from the MPU is reduced.

19. The method of claim 18, wherein the integrating step comprises determining cosine and sine of the measurement output.

20. The method of claim 18, further including computing an approximate gyroscope data from the integrated gyroscope output by computing a derivate of the integrated gyroscope output, the derivative of the integrated gyroscope output used to determine a gyroscope data bias.

21. An apparatus for generating orientation of a device comprising;

a gyroscope configured to sense an angular velocity of the device, at a first rate, to generate a measurement output on a motion processing unit (MPU);

an accelerometer configured to generate sensor data representing an orientation of the device, the MPU, gyroscope, and accelerometer formed on a first package;

a processor configured to integrate the measurement output from the gyroscope at the first rate to generate an integrated gyroscope output,

wherein the integrated gyroscope output represents a change in the orientation of the device and wherein transmission of the integrated gyroscope output and the sensor data by the first package is performed at a rate lower than the first rate, transmission of the integrated gyroscope output being at a rate lower than the first rate thereby reducing processing requirements of the MPU and reducing power consumption;

a sensor fusion formed on a second package located externally to the MPU and responsive to the transmitted integrated gyroscope data and sensor data from the first package and configured to generate sensor fusion outputs including the orientation of the device; and

a data rate block responsive to a requested data rate and based on the requested data rate, the data rate block configured to utilize one of the sensor fusion outputs to determine the data rate being requested;

wherein the lower rate allows the MPU to operate with various sensor fusion algorithms and the sensor fusion to be located externally to the MPU.

22. The apparatus of claim 21, wherein a second processor comprises the sensor fusion.

23. The apparatus of claim 21, further including a register responsive to the integrated gyroscope output and the one of the sensor fusion outputs utilized by data rate block, the one of the sensor fusion outputs utilized by data rate block being indicative of the requested data rate.