3D gesture stabilization for robust input control in mobile environments
View Patent ↗A non-contact gesture sensor is mounted within a vehicle for vehicle occupants to enter control commands by using hand gestures. The effects of vehicle motion and vibration are stabilized by an electronic circuit that includes an inertial motion sensor (IMU) in rigidly fixed relation to the gesture sensor. An adaptive filter processes the gesture sensor signal and the IMU sensor signal by modeling the arm and hand as a semi-rigid articulated body using a transfer function that relates accelerations measured by the IMU with vehicle motion-induced accelerations of the hand. The filter calculates a noise-reduced gesture signal by subtracting out the motion-induced accelerations and measurement noise. The filter also outputs a confidence measure that controls a threshold circuit that inhibits use of the filtered gesture signal when confidence in the filter's system estimation is low.
1. A stabilized gesture detecting circuit for use with a vehicle comprising:
an inertial sensor mounted to said vehicle and producing a vehicle motion signal indicative of changes in vehicle motion;
a non-contact gesture sensor mounted in fixed relation to said inertial sensor and producing a gesture signal in response to hand gestural motions of a vehicle occupant;
a filter coupled to receive said vehicle motion signal and said gesture signal and producing a filtered gesture signal;
the filter being tuned to reduce motion-induced noise in said gesture signal corresponding to movement of the gesture sensor; and
the filter being further tuned to reduce motion-induced noise in said gesture signal corresponding to vehicle motion-induced non-gestural motion of the vehicle occupant's hand.
2. The circuit of claim 1 wherein the inertial sensor is an accelerometer producing an acceleration signal indicative of said changes in vehicle motion.
3. The circuit of claim 2 wherein the accelerometer is a three-axis accelerometer, producing acceleration signals corresponding to three orthogonal axes.
4. The circuit of claim 1 wherein the gesture sensor comprises a collection of optical emitters and detectors.
5. The circuit of claim 1 wherein the filter is further tuned to reduce measurement noise in said gesture signal corresponding to measurement errors in the gesture signal.
6. The circuit of claim 1 wherein the filter is an adaptive filter corresponding to a transfer function that relates vehicle motion-induced acceleration measured at said gesture sensor to vehicle motion-induced acceleration measured at the vehicle occupant's hand.
7. The circuit of claim 6 wherein the adaptive filter implements at least one least mean squared (LMS) algorithm.
8. The circuit of claim 1 wherein the filtered gesture signal is adapted to be coupled to control a device associated with the vehicle;
wherein the filter is an adaptive filter that generates a confidence signal indicative of how accurately the adaptive filter is tracking the gesture signal; and
further comprising a threshold circuit coupled to receive said confidence signal and operative to inhibit use of the filtered gesture signal to control said device associated with the vehicle when the confidence signal is below a predetermined threshold.
9. The circuit of claim 1 wherein the filter is an adaptive filter that includes a first preprocessing circuit that receives the gesture signal and removes bias and drift to produce an adjusted gesture signal.
10. The circuit of claim 1 wherein the filter is an adaptive filter that includes a first preprocessing circuit that receives the gesture signal and produces an adjusted gesture signal that conforms to a stationary non-zero mean Gaussian domain.
11. The circuit of claim 10 wherein the filter further includes a normalized least mean squared filter receptive of the adjusted gesture signal and that generates an estimated transfer function that relates vehicle motion-induced acceleration measured at said gesture sensor to vehicle motion-induced acceleration measured at the vehicle occupant's hand.
12. The circuit of claim 11 wherein the filter further includes a computation circuit receptive of said estimated transfer function and said gesture signal and which calculates said filtered gesture signal by using the estimated transfer function and the vehicle motion signal to calculate a displacement of the occupant's hand associated to said vehicle motion-induced non-gestural motion and then subtracting said displacement from said gesture signal.
13. The circuit of claim 11 wherein the filter further includes a second least mean square filter receptive of said estimated transfer function that generates a measurement noise estimation signal.
14. The circuit of claim 13 wherein the filter further includes a computation circuit receptive of said estimated transfer function and said gesture signal and which calculates said filtered gesture signal by using the estimated transfer function and the vehicle motion signal to calculate a displacement of the occupant's hand associated to said vehicle motion-induced non-gestural motion and then subtracting said displacement and said measurement noise estimation signal from said gesture signal.
15. A method of stabilizing a gesture detecting circuit comprising:
electronically receiving and applying as input to a filter circuit a vehicle motion signal;
electronically receiving and applying as input to said filter circuit a non-contact gesture sensor signal; and
tuning the filter circuit to reduce motion-induced noise in said gesture signal corresponding to movement of the gesture sensor while additionally tuning said filter circuit to reduce motion-induced noise in the gesture signal corresponding to vehicle motion-induced non-gestural motion of the vehicle occupant's hand.
16. The method of claim 15 further comprising tuning the filter circuit to reduce measurement noise in said gesture signal corresponding to measurement errors in the gesture signal.
17. The method of claim 15 wherein the filter is an adaptive filter corresponding to a transfer function that relates vehicle motion-induced acceleration measured at said gesture sensor to vehicle motion-induced acceleration measured at the vehicle occupant's hand.
18. The method of claim 17 wherein the adaptive filter implements at least one least mean squared (LMS) algorithm.
19. The method of claim 15 wherein the filtered gesture signal is adapted to be coupled to control a device associated with the vehicle;
wherein the filter is an adaptive filter that generates a confidence signal indicative of how well the adaptive filter is tracking the gesture signal; and
further comprising a threshold circuit coupled to receive said confidence signal and operative to inhibit use of the filtered gesture signal to control said device associated with the vehicle when the confidence signal is below a predetermined threshold.
20. The method of claim 15 wherein the filter is an adaptive filter that includes a first preprocessing circuit that receives the gesture signal and removes bias and drift to produce an adjusted gesture signal.
21. The method of claim 15 wherein the filter is an adaptive filter that includes a first preprocessing circuit that receives the gesture signal and produces an adjusted gesture signal that conforms to a stationary non-zero mean Gaussian domain.
22. The method of claim 21 wherein the filter further includes a normalized least mean squared filter receptive of the adjusted gesture signal and that generates an estimated transfer function that relates vehicle motion-induced acceleration measured at said gesture sensor to vehicle motion-induced acceleration measured at the vehicle occupant's hand.
23. The method of claim 22 wherein the filter further includes a computation circuit receptive of said estimated transfer function and said gesture signal and which calculates said filtered gesture signal by using the estimated transfer function and the vehicle motion signal to calculate a displacement of the occupant's hand associated to said vehicle motion-induced non-gestural motion and then subtracting said displacement from said gesture signal.
24. The method of claim 21 wherein the filter further includes a second least mean square filter receptive of said estimated transfer function that generates a measurement noise estimation signal.
25. The method of claim 24 wherein the filter further includes a computation circuit receptive of said estimated transfer function and said gesture signal and which calculates said filtered gesture signal by using the estimated transfer function and the vehicle motion signal to calculate a displacement of the occupant's hand associated to said vehicle motion-induced non-gestural motion and then subtracting said displacement and said measurement noise estimation signal from said gesture signal.