ADIS16480 AD [Analog Devices], ADIS16480 Datasheet - Page 27

• Manufacturer Part Number: ADIS16480
• Description: Ten Degrees of Freedom Inertial Sensor
• Manufacturer: AD [Analog Devices]

Data Sheet
EXTENDED KALMAN FILTER
ALGORITHM
The extended Kalman filter (EKF) continuously estimates the
state vector, which includes the four elements in a quaternion
orientation array and the bias levels for all three gyroscopes.
Figure 22 illustrates the iterative process used in the EKF, which
uses angular rate measurements (gyroscopes) to predict orienta-
tion updates and then makes corrections using accelerometer
and magnetometer measurements. In addition to continuous
state estimation, the EKF also estimates the error covariance
terms. Using the covariance terms, current orientation, and
gyroscope sensor measurements, the algorithm computes a
Kalman gain that provides a weighting value for each sensor’s
contribution to the state vector. The
settings for the covariance terms but provides access to them in
the form of user-configuration registers, for fine tuning, based
on application-specific conditions/requirements.
COVARIANCE TERMS
Table 76 through Table 79 provides register information for the
gyroscope noise/RRW process covariance (Q) terms. Table 80
through Table 83 provides register information for the
accelerometer/magnetometer measurement covariance (R)
terms. These covariance terms use the IEEE 32-bit floating-
point format. Each term has two registers, one for the upper
word and one for the lower word.
Table 76. QCVR_NOIS_UPR (Page 3, Base Address = 0x62)
Bits
[15:0]
Table 77. QCVR_NOIS_LWR (Page 3, Base Address = 0x60)
Bits
[15:0]
Description (Default = 0x3727)
Gyroscope noise covariance term, upper word
Description (Default = 0xC5AC)
Gyroscope noise covariance term, lower word
Q COVARIANCE
GYROSCOPE
ADIS16480
has factory
PREDICT
ERROR COVARIANCE
ERROR COVARIANCE
QUATERNION, BIAS
QUATERNION, BIAS
EKF PROCESS
Figure 22. EKF Process
Rev. 0 | Page 27 of 40
QUATERNION
CORRECT
Table 78. QCVR_RRW_UPR (Page 3, Base Address = 0x66)
Bits
[15:0]
Table 79. QCVR_RRW_LWR (Page 3, Base Address = 0x64)
Bits
[15:0]
Table 80. RCVR_ACC_UPR (Page 3, Base Address = 0x6E)
Bits
[15:0]
Table 81. RCVR_ACC_LWR (Page 3, Base Address = 0x6C)
Bits
[15:0]
Table 82. RCVR_MAG_UPR (Page 3, Base Address = 0x72)
Bits
[15:0]
Table 83. RCVR_MAG_LWR (Page 3, Base Address = 0x70)
Bits
[15:0]
Description (Default = 0x3189)
Accelerometer measurement variance term, upper word
Description (Default = 0x705F)
Accelerometer measurement variance term, lower word
Description (Default = 0x32AB)
Magnetometer measurement variance term, upper word
Description (Default = 0xCC77)
Magnetometer measurement variance term, lower word
Description (Default = 0x2E5B)
Gyroscope rate random walk (RRW) covariance term,
upper word
Description (Default = 0xE6FF)
Gyroscope rate random walk (RRW) covariance term,
lower word
ACCELEROMETERS
MAGNETOMETERS
R COVARIANCE
ADIS16480