Motion detection device and corresponding method

1. A wearable motion detection device configured for detecting body-to-ground proximity, the device comprising:

a capacitance detection unit arranged to detect body-to-ground capacitance, the capacitance detection unit comprising:

a first electrode arranged to contact a body portion of a monitored user, when the device is worn,

a second electrode that is arranged separately from but operatively connected with the first electrode,

a shield electrode that is arranged to shield the second electrode from the first electrode,

a control unit arranged to detect, under consideration of a body-to-ground capacitance signal provided by the capacitance detection unit, positional changes of the user.

2. The device as claimed in claim 1 , wherein the control unit compares a change in the capacitance measured by the capacitance detection unit to a threshold value to detect at least one of a body-to-ground contact, a body-to-ground proximity, and a body-to-ground approach.

3. The device as claimed in claim 1 , wherein the device is arranged as an arm-wearable or wrist-wearable device comprising a belt-shaped or ring-shaped strap comprising a support layer, wherein the first electrode is arranged in an inwardly-facing fashion, wherein the second electrode is arranged in an outwardly-facing fashion, and wherein the shield electrode is arranged between the first electrode and the second electrode.

4. The device as claimed in claim 3 , wherein the first electrode and the second electrode, preferably also the shield electrode, are arranged, such that the second electrode encompasses the first electrode.

5. The device as claimed in claim 4 , further comprising a control case attached to the strap, wherein the control unit is arranged in the control case and wherein the control unit is operatively coupled to the first electrode, the second electrode, and the shield electrode.

6. The device as claimed in claim 1 , wherein measurement electrodes of the capacitance detection unit consist of a single first electrode, a single second electrode, and a single shield electrode.

7. The device as claimed in claim 1 , wherein the first electrode is arranged to cling to the subject's skin at a measurement site to which the device is attached, and wherein preferably non-conductive layers are provided between the first electrode, the second electrode, and the shield electrode.

8. The device as claimed in claim 1 , further comprising a voltage follower unit for operating the shield electrode at the same potential as the second electrode.

9. The device as claimed in claim 1 , further comprising an accelerometer unit arranged to detect body acceleration of the subject of interest, wherein the control unit is arranged to detect a fall event based on an accelerometer signal provided by the accelerometer unit and on the capacitance signal provided by the capacitance detection unit.

10. The device as claimed in claim 1 , wherein the shield electrode comprises an areal extension that is at least two times larger, preferably four times larger, than the areal extension of the second electrode, wherein the shield electrode is at least sectionally arranged as a strip comprising an axial extension that extends beyond the axial extension of the second layer.

11. The device as claimed in claim 1 , further comprising a timer module arranged to control a discharge/charge action of a capacitor one terminal of which is formed by the second electrode, wherein a discharge/charge frequency is indicative of body-to-ground proximity, when the device is worn, particularly of ground contact.

12. The device as claimed in claim 11 , wherein the timer module is further arranged to apply a defined trigger level and to apply a defined threshold level based on which the discharge/charge action is controlled.

13. The device as claimed in claim 1 , wherein the second electrode is arranged to be coupled to a mobility aid selected from the group consisting of at least one of a walking aid, a walking frame and a wheelchair.

14. A motion detection method utilizing body-to-ground proximity detection, the method comprising the following steps:

applying a capacitance detection unit to a body portion of a subject of interest, the capacitance detection unit being arranged to detect body-to-ground capacitance and comprising:

a first electrode arranged to contact a body portion of a monitored user,

wherein applying a capacitance detection unit includes arranging the first electrode to establish a contact to the body portion,

a second electrode that is arranged separately from but operatively connected with the first electrode,

a shield electrode that is arranged to shield the second electrode from the first electrode,

causing the capacitance detection unit to output a body-to-ground proximity capacitance signal based on a capacitance measurement between the second electrode and the ground, and

detecting, under consideration of the body-to-ground capacitance signal, positional changes of the user.

15. Computer program comprising program code means for causing a computer to carry out the steps of the method as claimed in claim 14 when said computer program is carried out on a computer.