System and method for determining the orientation of an inertial measurement unit (IMU)
First Claim
1. An inertial measurement unit (IMU) comprising:
- a gyroscope having an output to supply gyroscopic readings;
an accelerometer having an output to supply accelerometer readings;
a processor,a non-transitory memory;
an IMU application residing in the non-transitory memory, comprising a sequence of processor executable instructions for calculating a gyroscopic quaternion in response to gyroscopic readings, calculating a field quaternion using accelerometer readings when an accelerometer reading is about equal to gravity (1 G), estimating angular orientation errors due to IMU angular velocity and linear acceleration, and using the angular orientation errors to selectively mix the gyroscopic quaternion and field quaternion to supply a current sample quaternion; and
,an IMU interface to supply a current IMU orientation in space, responsive to the current sample quaternion.
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Accused Products
Abstract
A system and method are provided for determining the orientation of an inertial measurement unit (IMU). The method calculates a gyroscopic quaternion, and when the IMU accelerometer reading is about equal to gravity (1 G), a field quaternion is calculated using IMU accelerometer readings. Estimates are made of angular orientation errors due to IMU angular velocity and linear acceleration, and these angular orientation errors are used to selectively mix the gyroscopic quaternion and field quaternion to supply a current sample quaternion. Alternatively, if the accelerometer reading is not about equal to 1 G, the gyroscopic quaternion is used as the current sample quaternion. In one aspect, IMU gyroscope readings and IMU accelerometer readings are calibrated in response to determining a lack of IMU movement. Near-zero gyroscope reading jitter is removed by setting the IMU gyroscopic reading to zero, when the gyroscopic reading is near zero.
13 Citations
13 Claims
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1. An inertial measurement unit (IMU) comprising:
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a gyroscope having an output to supply gyroscopic readings; an accelerometer having an output to supply accelerometer readings; a processor, a non-transitory memory; an IMU application residing in the non-transitory memory, comprising a sequence of processor executable instructions for calculating a gyroscopic quaternion in response to gyroscopic readings, calculating a field quaternion using accelerometer readings when an accelerometer reading is about equal to gravity (1 G), estimating angular orientation errors due to IMU angular velocity and linear acceleration, and using the angular orientation errors to selectively mix the gyroscopic quaternion and field quaternion to supply a current sample quaternion; and
,an IMU interface to supply a current IMU orientation in space, responsive to the current sample quaternion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An inertial measurement unit (IMU) comprising:
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a gyroscope having an output to supply gyroscopic readings; an accelerometer having an output to supply accelerometer readings; a processor, a non-transitory memory; an IMU application residing in the non-transitory memory, comprising a sequence of processor executable instructions for calculating a gyroscopic quaternion in response to gyroscopic readings, calculating a field quaternion using accelerometer readings when an accelerometer reading is about equal to gravity (1 G), estimating angular orientation errors due to IMU angular velocity and linear acceleration, and using a field quaternion estimate error and the angular distance between the gyroscope quaternion and field quaternion to relatively weight the gyroscope quaternion and field quaternion used to form a current sample quaternion; and
,an IMU interface to supply a current IMU orientation in space, responsive to the current sample quaternion.
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Specification