Mapped variable smoothing evolution method and device
View Patent ↗The present inventions generally relate to methods and dedicated apparatuses outputting a variable mapped on a device orientation in a non-inertial reference system, with the device orientation being estimated using measurements of motion sensors (such as 3D accelerometers and gyroscopes) and a magnetometer or other similar sensors including cameras. A variable mapped on an orientation of a device is smoothed to have a gradual evolution by adjusting the estimated orientation of the device obtained via sensor fusion or other sensor processing to take into consideration a current measured angular velocity.
1. A method for smoothing evolution of a variable depending on an orientation of a device, the method comprising:
determining an adjusted angular velocity (Ω s,n ) based on a measured angular velocity (ω n ) and an estimated angular velocity (Ω f,n ), such that to satisfy one or more predefined constraints, including at least one constraint for masking of any of a correction and an artifact;
determining a current value (x) of the variable according to an adjusted estimate of the current orientation (q s,n ) of the device obtained using the adjusted angular velocity (Ω s,n ); and
outputting the current value (x) of the variable.
2. The method of claim 1 , wherein the variable defines any of a position of a cursor on a screen and an image displayed to a video-game user.
3. The method of claim 1 , wherein the adjusted estimate of the current orientation of the device, and the measured, estimated and adjusted angular velocities are expressed in a reference system defined relative to gravity direction and Earth magnetic field direction.
4. The method of claim 1 , further comprising:
calculating the estimated angular velocity (Ω f,n ) using an estimate of a current orientation (q f,n ) of the device and an adjusted estimate of a previous orientation (q s,n-1 ) of the device.
5. The method of claim 4 , wherein the estimate of the current orientation (q f,n ) of the device is obtained using a sensor fusion method, wherein the sensor fusion method uses measurements of any of a magnetometer and an accelerometer, and wherein the measured angular velocity is obtained using a gyroscope.
6. The method of claim 5 , wherein the estimate of the current orientation (q f,n ) and the adjusted estimate of a previous orientation (q s,n-1 ) are expressed as quaternions.
7. The method of claim 1 , wherein the one of more predetermined constraints include the adjusted angular velocity (Ω s,n ) being substantially equal to zero when the measured angular velocity (ω n ) is substantially equal to zero.
8. The method of claim 1 , wherein the determining of the adjusted angular velocity (Ω s,n ) includes projecting the estimated angular velocity (Ω f,n ) along a direction of the measured angular velocity (ω n ),
calculating a scaling factor (α) as a ratio of the result of the projecting and a magnitude of the measured angular velocity (ω n ); and
if the scaling factor exceeds a predetermined first value (MaxScaling) or is below a predetermined second value (MinScaling), setting the scaling factor (α) equal to the predetermined first value or to the predetermined second value, respectively,
wherein a magnitude of the adjusted angular velocity (Ω s,n ) is equal to the magnitude of the measured angular velocity (ω n ) multiplied with the scaling factor.
9. The method of claim 1 , wherein the determining of the adjusted angular velocity (Ω s,n ) includes:
determining an auxiliary unit vector (v 2 ) based on a first unit vector (v 0 ) along the measured angular velocity (ω n ), a second unit vector (v 1 ) along the estimated angular velocity (Ω f,n ) and an angle (θ) there-between; and
determining a unit vector (v) along the adjusted angular velocity (Ω s,n ) using the first, second and auxiliary unit vectors.
10. The method of claim 9 , wherein the unit vector (v) is the second unit vector (v 1 ) if the angle (θ) between the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ) is less than or equal to a maximum angle (θ max ).
11. The method of claim 10 , wherein if the angle (θ) is larger than the maximum angle (θ max ), then the unit vector (v) is at the maximum angle from the measured angular velocity (ω n ), between and in a same plane as the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ).
12. The method of claim 11 , wherein the determining of the adjusted angular velocity (Ω s,n ) includes projecting the estimated angular velocity (Ω f,n ) along a direction of the measured angular velocity (ω n ),
calculating a scaling factor (α) as a ratio of the result of the projecting and a magnitude of the measured angular velocity (ω n ); and
if the scaling factor (α) exceeds a predetermined first value (MaxScaling) or is below a predetermined second value (MinScaling), setting the scaling factor (α) equal to the predetermined first value or to the predetermined second value, respectively,
wherein a magnitude of the adjusted angular velocity (Ω s,n ) is equal to the magnitude of the measured angular velocity (ω n ) multiplied with the scaling factor (α).
13. The method of claim 12 , further comprising:
adjusting at least one of the predetermined first value (MaxScaling), the predetermined second value (MinScaling) and the maximum angle (θ max ).
14. The method of claim 1 , further comprising:
outputting a stabilized current orientation which is equal to a stabilized previous orientation (q′ s,n-1 ) if a difference between the adjusted estimate of the current orientation (q s,n ) and the stabilized previous orientation (q′ s,n-1 ) is less than a predetermined threshold (m).
15. The method of claim 14 , wherein if a difference between the adjusted estimate of the current orientation (q s,n ) and the stabilized previous orientation (q′ s,n-1 ) exceeds the predetermined threshold (m), then the stabilized current orientation (q′ s,n ) is equal to the adjusted estimate of the current orientation (q s,n ) after being shifted with the predetermined threshold, towards the stabilized previous orientation (q′ s,n-1 ).
16. The method of claim 1 , wherein the adjusted estimate of the current orientation (q s,n ) of the device is obtained by adding to a previous orientation (q s,n-1 ) of the device, a change thereof obtained by integrating the adjusted angular velocity (Ω s,n ) over a time interval.
17. A gaming system configured to display an image to a user according to an orientation of a device, the system comprising:
sensors mounted on the device and configured to acquire information leading to a measured angular velocity (ω n ) and an estimate of a current orientation (q f,n ) of the device; and
a data processing unit configured to determine:
an adjusted angular velocity (Ω s,n ) based on the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ), such that to satisfy one or more predefined constraints, including at least one constraint for masking of any of a correction and an artifact;
an adjusted estimate of the current orientation (q s,n ) of the device obtained using the adjusted angular velocity (Ω s,n ); and
the image to be displayed to the user according to the adjusted estimate of the current orientation.
18. An information system controlled by orientation of a device, the system comprising:
sensors mounted on the device and configured to acquire information leading to a measured angular velocity (ω n ) and an estimate of a current orientation (q f,n ) of the device; and
a data processing unit configured to determine:
an adjusted angular velocity (Ω s,n ) based on the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ), such that to satisfy one or more predefined constraints, including at least one constraint for masking of any of a correction and an artifact;
an adjusted estimate of the current orientation (q s,n ) of the device obtained using the adjusted angular velocity (Ω s,n ); and
a position of a cursor on a screen based on the current orientation (q s,n ) of the device.
19. An apparatus directed to smoothing evolution of a variable depending on an orientation of a device, the apparatus comprising circuitry, including a processor and memory, configured to:
determine an adjusted angular velocity (Ω s,n ) based on a measured angular velocity (ω n ) and an estimated angular velocity (Ω f,n ), such that to satisfy one or more predefined constraints, including at least one constraint for masking of any of a correction and an artifact; and
determine a current value (x) of the variable according to an adjusted estimate of the current orientation (q s,n ) of the device obtained using the adjusted angular velocity (Ω s,n ); and
output the current value (x) of the variable.
20. The apparatus of claim 19 , wherein the circuitry is configured to determine the adjusted angular velocity (Ω s,n ) by, at least in part:
projecting the estimated angular velocity (Ω f,n ) along a direction of the measured angular velocity (ω n ),
calculating a scaling factor (α) as a ratio of the result of the projecting and a magnitude of the measured angular velocity (ω n ); and
if the scaling factor exceeds a predetermined first value (MaxScaling) or is below a predetermined second value (MinScaling), setting the scaling factor (α) equal to the predetermined first value or to the predetermined second value, respectively,
wherein a magnitude of the adjusted angular velocity (Ω s,n ) is equal to the magnitude of the measured angular velocity (ω n ) multiplied with the scaling factor.
21. The apparatus of claim 19 , wherein the circuitry is configured to determine the adjusted angular velocity (Ω s,n ) by, at least in part:
determining an auxiliary unit vector (v 2 ) based on a first unit vector (v 0 ) along the measured angular velocity (ω n ), a second unit vector (v 1 ) along the estimated angular velocity (Ω f,n ) and an angle (θ) there-between; and
determining a unit vector (v) along the adjusted angular velocity (Ω s,n ) using the first, second and auxiliary unit vectors.
22. The apparatus of claim 21 , wherein the unit vector (v) is the second unit vector (v 1 ) if the angle (θ) between the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ) is less than or equal to a maximum angle (θ max ).
23. The apparatus of claim 22 , wherein if the angle (θ) is larger than the maximum angle (θ max ), then the unit vector (v) is at the maximum angle from the measured angular velocity (ω n ), between and in a same plane as the measured angular velocity (ω n ) and the estimated angular velocity (Ω f,n ).
24. The apparatus of claim 19 , wherein the circuitry is configured to:
output a stabilized current orientation which is equal to a stabilized previous orientation (q′ s,n-1 ) if a difference between the adjusted estimate of the current orientation (q s,n ) and the stabilized previous orientation (q′ s,n-1 ) is less than a predetermined threshold (m).
25. The apparatus of claim 24 , wherein if a difference between the adjusted estimate of the current orientation (q s,n ) and the stabilized previous orientation (q′ s,n-1 ) exceeds the predetermined threshold (m), then the stabilized current orientation (q′ s,n ) is equal to the adjusted estimate of the current orientation (q s,n ) after being shifted with the predetermined threshold, towards the stabilized previous orientation (q′ s,n-1 ).
26. The apparatus of claim 19 , wherein the adjusted estimate of the current orientation (q s,n ) of the device is obtained by adding to a previous orientation (q s,n-1 ) of the device, a change thereof obtained by integrating the adjusted angular velocity (Ω s,n ) over a time interval.